process for producing acetic acid, and method for separating or removing acetaldehyde

专利摘要:
PROCESS TO PRODUCE ACETIC ACID, AND, METHOD TO SEPARATE OR REMOVE ACETALDEHYDE. A method is provided to effectively remove acetaldehyde and produce acetic acid in a stable manner. Methanol and carbon monoxide are reacted continuously in a carbonylation reactor (1) in the presence of a catalyst system, the reaction mixture is supplied continuously to an expander (2), and a volatile phase (2A) containing acetic acid and iodide of methyl is produced The volatile phase (2A) is continuously supplied to a separation column (3) and separated at the top (3A) containing methyl iodide and acetaldehyde, and flow fraction (3B) containing acetic acid. The volatile phase (2A) and / or the upper part (3A) are cooled by first condensers (C1, C3) having a predetermined cooling temperature, the non-condensed gas component is additionally cooled by second condensers (C2, C4) and condenses do, the temperature is further lowered, and a concentrate in which acetaldehyde was concentrated to a high concentration is produced. The high-concentration acetaldehyde concentrate is distilled through a distillation column (6), and the acetaldehyde is effectively removed.
公开号:BR112015014628B1
申请号:R112015014628-7
申请日:2013-12-02
公开日:2021-01-05
发明作者:Masahiko Shimizu；Ryuji Saito；Hiroyuki Miura
申请人:Daicel Corporation；
IPC主号:

专利说明:

TECHNICAL FIELD
[001] The present invention relates to a process for producing acetic acid by methanol carbonylation, particularly it relates to a process to produce acetic acid with effectively decreased impurities (e.g., acetaldehyde) and a method for removing acetaldehyde. TECHNICAL FUNDAMENTALS
[002] Industrial processes known to produce acetic acid include a process that comprises allowing methanol to continuously react with carbon monoxide in a liquid phase having a low water content in the presence of a rhodium catalyst, a metal iodide, and iodide methyl to produce acetic acid with high productivity. In the reaction liquid, there are small amounts of by-products (impurity), for example, a carbonylated compound (for example, acetaldehyde, butylaldehyde, crotonaldehyde, 2-ethylcrotonaldehyde, and an aldol condensate) and an organic iodide (for example, iodide of C2-12 alkyl such as ethyl iodide, butyl iodide, or hexyl iodide). These impurities result in low quality of acetic acid. Extremely low amounts of reducing impurities present in acetic acid can be assessed by a test with a permanganate reducing substance (permanganate time), and this method of assessment detects very small concentrations of impurities that are difficult to determine quantitatively even by advanced instrumental analysis current. In addition, some of these impurities have adverse effects in relation to the use of acetic acid. For example, in a case in which vinyl acetate is produced from ethylene and acetic acid, it is known that such impurities deteriorate a catalyst in the palladium series that is used. Unfortunately, a carbonyl compound such as acetaldehyde and a C1-12 alkyl iodide cannot be removed sufficiently by ordinary means such as distillation, due to the fact that they have very close boiling points.
[003] In a continuous reaction process, the removal of a carbonyl compound in a process recycling stream has been attempted. For example, Publication Open to Public Inspection of Japanese Patent Application No. 4-266843 (JP-4-266843A, Patent Document 1) describes a method for removing carbonyl impurities, which comprises contacting a stream of recycled methyl iodide for a carbonylation reactor with an amino compound to form a water-soluble nitrogenous derivative by a reaction with carbonyl impurities; separating an organic phase of methyl iodide from an aqueous phase of derivative; and distilling the methyl iodide phase from an aqueous derivative phase; and distill the methyl iodide phase to remove carbonyl impurities. However, the content of carbonyl impurities in the organic stream recycled to the carbonylation reactor is still high, and it is difficult to sufficiently remove the carbonyl impurities. In addition, the method described in this document requires the removal of nitrogenous compounds.
[004] Publication Open to Public Inspection of Japanese Patent Application No. 8-67650 (JP-8-67650A, Patent Document 2) describes a process for producing a highly purified acetic acid, comprising the step of allowing methanol to react continuously with carbon monoxide in the presence of a rhodium catalyst, an iodide salt, and methyl iodide to produce acetic acid, in which the concentration of acetaldehyde in the reaction liquid is maintained no greater than 400 ppm by removing acetaldehyde from the liquid of the process being recycled to a reactor. This document considers that impurities are formed predominantly in the reaction system and that these impurities originate in the acetaldehyde by-product formed in the reaction system. Thus, according to the document, the content of carbonylated compound or the content of organic iodide is reduced by controlling the concentration of acetaldehyde in the reaction system, and high purity acetic acid is obtained.
[005] Additionally, this document refers to a process for producing acetic acid while removing acetaldehyde and describes a process that comprises separating a reaction liquid into a volatile phase containing acetic acid, methyl acetate and methyl iodide and a low volatility containing a rhodium catalyst; distill the volatile phase to form a product containing acetic acid and a column top effluent containing methyl acetate and methyl iodide; contact the column top effluent rich in carbonyl impurity (particularly acetaldehyde) with water to form an organic phase containing methyl acetate and methyl iodide and an aqueous phase containing the carbonyl impurities, and recycle the organic phase into a reactor. In addition, as a concrete method for separating methyl iodide from the concentrate containing the carbonylated impurity, this document describes that it is selectively preferred to extract the acetaldehyde by distillation and separate a stream of acetaldehyde containing methyl iodide from the process stream and subject it to the rich stream in acetaldehyde resulting from water extraction.
[006] According to this document, acetic acid is purified by distillation of the volatile phase (by a first distillation column) to form a column top effluent containing methyl acetate and methyl iodide (for example, a lower phase formed by liquid-liquid separation from the column top effluent); distill the column top effluent through a distillation column; and subjecting a concentrated acetaldehyde stream from the top of the column to water extraction to remove acetaldehyde. In the entire process, although acetaldehyde is concentrated to some degree in the column top effluent, the concentration of acetaldehyde in the column top effluent is not as high. Consequently, acetaldehyde cannot be removed effectively in a process to treat a liquid that has a low concentration of acetaldehyde.
[007] WO2010 / 053571 (Patent Document 3) describes a process for producing acetic acid, which comprises carbonyl methanol, subjecting a reaction mixture to flash distillation, distilling the resulting low boiling component through a first distillation column for form a stream of acetic acid and an exhaust gas containing a light tip fraction (eg methyl iodide) and an aldehyde impurity (eg acetaldehyde), wash the exhaust stream with an absorption solvent (such as acetic acid) or methanol), extract the light tip fraction and the aldehyde impurity from the absorption solvent to form a light tip stream, purify the light tip stream through a second distillation column to remove the aldehyde impurity, subject the distillate to extraction with water to remove the aldehyde impurity, and recycle the light tip fraction of the light tip stream into the reaction system. Unfortunately, since the absolute amount of acetaldehyde contained in the exhaust gas is small, acetaldehyde cannot be removed effectively. RELATED TECHNICAL DOCUMENTS PATENT DOCUMENTS Patent Document 1: JP-4-266843A (Claims) Patent Document 2: JP-8-67650A (Claims, [0007] [0018], and Examples) Patent Document 3: WO 2010 / 053571 (Claims) SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION
[008] Therefore, an objective of the present invention is to provide a process for producing acetic acid while effectively removing acetaldehyde.
[009] Another objective of the present invention is to provide a process for producing high purity acetic acid while concentrating acetaldehyde in a simple manner and effectively removing it from a process stream.
[0010] Yet another objective of the present invention is to provide a process for producing high quality acetic acid by the concentration of acetaldehyde and methyl iodide for higher levels and effective removal of acetaldehyde from the concentrate.
[0011] An additional objective of the present invention is to provide a process for producing high quality acetic acid by effectively separating an aqueous phase (or upper phase) highly rich in acetaldehyde and an organic phase (or lower phase) containing methyl iodide and effective separation and removal of acetaldehyde from the aqueous phase. MEANS TO SOLVE THE PROBLEMS
[0012] The inventors of the present invention observed that, among the components of acetic acid, methyl acetate, methyl iodide, methanol, water and acetaldehyde, acetaldehyde, which adversely affects the quality of acetic acid, has a boiling point near to that of methyl iodide and has a lower boiling point, and carried out intensive studies to achieve the above objectives. After the studies, the inventors found that (a) methyl iodide and a large amount of acetaldehyde are contained in a volatile phase [which is formed by flash distillation of a reaction mixture produced by methanol carbonylation in the presence of a catalyst system containing a metal catalyst, a metal halide and methyl iodide], particularly in a column top effluent formed by the distillation of the volatile phase; and (b) condensation of the volatile phase, particularly of column top effluent, by a plurality of condensers at a sequentially lower cooling temperature (condensate temperature) allows the concentration of methyl iodide and acetaldehyde to higher levels to separate acetaldehyde in the form of a gaseous phase or condensate from the process stream, and the process can effectively remove acetaldehyde compared to direct removal of acetaldehyde by simple distillation of the column top effluent. For example, if a column top effluent gas (a column top effluent) from a first distillation column that distills the volatile phase is cooled by a first condenser to form a condensate having a certain temperature and a non-gaseous component condensate is cooled by a second condenser having a lower cooling temperature than that of the first condenser to form a condensate having a lower temperature than that of the first condensate, so acetaldehyde, which is a low boiling point component, is concentrated in the condensate of the second condenser in a higher concentration compared to the concentration of acetaldehyde in a process liquid (condensate) obtained from the simple condensation of the total amount of column top effluent by only the first condenser. A process liquid predominantly comprising highly concentrated acetaldehyde is subjected to the acetaldehyde removal treatment (e.g., distillation) to produce a concentrate having an additionally higher concentration of acetaldehyde, and thus the acetaldehyde can be effectively removed from the system. The present invention was carried out on the basis of the above findings.
That is, according to the present invention, a process for producing acetic acid comprises: a reaction step to allow methanol to continuously react with carbon monoxide in the presence of a catalyst system containing a metal catalyst (for example , a rhodium catalyst), a metal halide (for example, a metal iodide), and methyl iodide in a carbonylation reactor; a flash evaporation step to separate a reaction mixture, which is continuously fed from the reactor to a flasher (or an evaporator), in a volatile phase (lowest boiling component) (2A) containing produced acetic acid and iodide from methyl and a less volatile phase (or low volatility phase, higher boiling point component) (2B) containing the metal catalyst and the metal halide; a distillation step (or an acetic acid collection step) to separate the volatile phase (2A), which is continuously fed to at least one distillation column, in a column top effluent (lowest boiling point component) ) (3A) containing methyl iodide and acetaldehyde by-product and a stream (3B) containing acetic acid; and a step to condense a gas phase, containing at least methyl iodide and acetaldehyde, resulting from at least one step of these steps, to separate acetaldehyde from the condensate. In the process for producing acetic acid according to the present invention, the aqueous phase is condensed by a plurality of condensers to form sequentially lower condensates at temperature, and acetaldehyde is separated or removed from a condensate (s) enriched in acetaldehyde .
[0014] The gas phase containing at least acetaldehyde can be a low-boiling gas component resulting from at least one flash evaporation step and the distillation step. For example, the gas phase can be a volatile phase of the flash evaporation step or it can be a column top effluent from a distillation step or a plurality of distillation steps. The gaseous phase preferably includes at least one column top effluent (particularly, a first column top effluent having a high acetaldehyde concentration from a first distillation step). In addition, the gas phase may be a low-boiling gas component contained in an expelled gas (waste gas) discharged or discharged from the process. The gas phase may contain acetaldehyde, methyl iodide, and others.
[0015] In order to effectively separate and remove acetaldehyde from the column top effluent (3A), the column top effluent (3A) as the gas phase can be subjected to a plurality of condensers and cooled to form condensates and gaseous components non-condensing, where the condensates can have a lower temperature and a higher concentration of acetaldehyde sequentially in the downstream direction (or where a condensate on a more downstream side has a lower temperature and a higher concentration of acetaldehyde) ; and acetaldehyde can be separated from a condensate (s) having a high concentration of acetaldehyde. In addition, the volatile phase (2A) can be distilled by a first distillation column to form a column top effluent, and the column top effluent like the gas phase can be condensed by the plurality of condensers to separate acetaldehyde from a condensate (s) enriched in acetaldehyde.
[0016] The component to be fed to the acetaldehyde separation step is not particularly limited to column top effluent (3A) or a condensate thereof, and various process streams can be used as such a component. For example, in order to effectively separate and remove acetaldehyde from the volatile phase (2A) separated by the flasher, the volatile phase (2A) like the gas phase can be subjected to a plurality of condensers and cooled to form condensates and non-condensed gaseous components, wherein the condensates may have a lower temperature and a higher concentration of acetaldehyde sequentially in the downstream direction; and acetaldehyde can be separated from a condensate (s) having a high concentration of acetaldehyde. In addition, the volatile phase (2A) like the gas phase can be condensed by the plurality of capacitors, an upper phase and / or a lower phase formed in at least one among a second or subsequent capacitors [in other words, at least one among the second (2nd) to the nth (no) (n = 2 an) condensers except a first capacitor, where the number of capacitors is n] can be distilled by a first distillation column and / or a second distillation column to form a first column top effluent and / or a second column top effluent.
[0017] Additionally, the gas phase can be condensed by the plurality of condensers, and a condensate from at least one of a second and subsequent condensers (for example, a condensate (concentrate) enriched in acetaldehyde) can be stored in a storage tank. , and acetaldehyde can be separated from the stored condensate.
[0018] Additionally, according to the present invention, since acetaldehyde can be effectively removed from a process stream, a useful component can be recycled to a process step. For example, the volatile phase (2A) separated in the flasher can be distilled by a first distillation column to form a first column top effluent, the column top effluent like the gas phase can be condensed by the plurality of condensers, and a condensate of at least one of a second and subsequent condensers (in a case in which a condensate is separated into two liquid phases (or layers), an upper phase and / or a lower phase) can be distilled by a second distillation column to separate or produce a second column top effluent rich in acetaldehyde. In this process, the first column top effluent can be condensed by the plurality of condensers, a condensate of at least one of a second and subsequent condensers (in a case in which a condensate is separated into two liquid phases (or layers), one upper and / or a lower phase) can be stored in a storage tank, and the stored liquid can be distilled through a second distillation column to separate or produce a second column top effluent rich in acetaldehyde. In addition, the gas phase can be condensed by the plurality of condensers, a condensate of at least one first condensate can be stored in a decanter, a condensate of at least one of a second and subsequent condensers (for example, an condensate enriched in acetaldehyde) it can be stored in a storage tank, the liquid stored in the decanter and the liquid stored in the storage tank can be combined, and acetaldehyde can be separated from the combined liquid. For example, the first column-top effluent such as the gas phase can be condensed by the plurality of condensers, a condensate from at least one first condenser (in a case in which a condensate is separated into two liquid phases (or layers), one upper phase and / or a lower phase) can be stored in a decanter, a condensate of at least one of a second and subsequent condensers (in a case in which a condensate is separated into two liquid phases (or layers), an upper phase and / or a lower phase) can be stored in a storage tank, the condensate in the decanter and the condensate in the storage tank can be combined and distilled by a second distillation column to separate or produce a second rich column top effluent in acetaldehyde. The liquid stored in the decanter and the liquid stored (condensate enriched in acetaldehyde) in the storage tank can be combined in a weight ratio of about 0/100 to 95/5 as the liquid stored in the decanter / the liquid stored in the storage tank. storage, and the combination of these can be distilled.
[0019] The second column top effluent can be subjected to extraction with water to form an aqueous phase containing acetaldehyde and an organic phase containing methyl iodide, and the organic phase can be recycled to the reactor. For example, the reaction mixture can be flashered to form a volatile phase (2A), the volatile phase (2A) can be distilled through the first distillation column to form at least a first column top effluent (3A) a gaseous phase selected from the volatile phase (2A) and the first column-top effluent (3A) can be condensed by the plurality of condensers to form sequentially lower condensates in temperature, a condensate of at least one of a second and subsequent condensers (in a case in which a condensate is separated into two liquid phases (or layers), an upper phase and / or a lower phase) it can be distilled by a second distillation column to form a second column top effluent, the second column top effluent (if necessary, the upper phase and / or the lower phase formed in the condenser) can be subjected to extraction with water, and the resulting organic phase (heavy phase, methyl iodide phase) can be recycled to the reactor.
[0020] The gas phase can be condensed by 2 to 5 condensers positioned at least in series. In addition, since acetaldehyde has a low boiling point, acetaldehyde can be separated from a condensate of at least one within a second and subsequent condensers among the plurality of capacitors. For example, in a case where two condensers are used, the gas phase can be cooled by a first condenser to form a first condensate and a first non-condensed gas component, the first non-condensed gas component can be cooled by a second condenser whose cooling temperature is lower than that of the first condenser to form a second condensate having a temperature lower than that of the first condensate and a second non-condensed gas component, and acetaldehyde can be separated from at least the second condensate.
[0021] Additionally, acetaldehyde can be separated and removed from an exhaust gas (waste gas) resulting from the process. For example, from the reaction step (reactor), an exhaust gas is generated at a relatively high pressure. In addition, an exhaust gas is also generated from a condenser (in particular, a last condenser) to condense the volatile phase of the flash evaporation step and a condenser (in particular, a last condenser) to condense the top effluent from column of the distillation step. Thus, an expelled gas, containing at least methyl iodide and acetaldehyde, resulting from at least one step between the reaction step, the flash evaporation step, the storage step (condensate storage step) and at least one step Distillation can be allowed to contact an absorption solvent, the resulting solvent can be extracted to form a gas phase containing at least methyl iodide and acetaldehyde, and acetaldehyde can be separated from the gas phase. This process may comprise a recovery (or collection) step to recover (or collect) a lower boiling point component with an absorption solvent.
[0022] The process may additionally comprise a separation and recycling step to separate acetaldehyde from at least a portion (portion or total, or a mixture containing a portion or total of each condensate) of acetaldehyde condensates formed in the plurality of condensers, and recycling a residual liquid from which acetaldehyde has been removed (a liquid with acetaldehyde removed) for at least one step from the reaction step to the acetaldehyde separation step. For example, the residual liquid from which acetaldehyde has been removed (for example, a liquid rich in methyl iodide) can be recycled, for example, to the reactor, the flasher, the separating column, and the distillation column.
[0023] Each of the condensates formed in the plurality of capacitors has a temperature at which a mixture of volatile components is condensable, for example, a condensate formed in a first condenser can have a temperature no lower than an boiling point of acetaldehyde, and a condensate formed in at least one of a second and subsequent condensers (for example, a last condenser) can have a temperature at which the acetaldehyde is condensable (for example, a temperature lower than the boiling point). For example, the condensate formed in a first capacitor out of the plurality of capacitors can have a temperature no higher than 110 ° C (for example, about 20 ° C to 110 ° C) and preferably a temperature no higher than 105 ° C (for example, about 30 ° C to 100 ° C). In addition, the condensate formed in at least one of a second and subsequent condensers (for example, one last capacitor) can have a temperature no higher than 45 ° C (for example, about -15 ° C to 45 ° C) and preferably a temperature of -10 ° C to 40 ° C (for example, about -5 ° C to 30 ° C).
[0024] Additionally, the present invention also includes a method for separating or removing acetaldehyde from a mixture (or liquid mixture). This method comprises: distilling a mixture containing acetic acid, methyl acetate, methyl iodide, methanol, water and acetaldehyde to form a gas phase containing at least methyl iodide and acetaldehyde and a liquid phase containing at least water and methanol; and condensing the gas phase for the purpose of separating acetaldehyde from the condensate (s). The aqueous phase is condensed by a plurality of condensers to form sequentially lower condensates at temperature, and acetaldehyde is separated or removed from a condensate (s) enriched in acetaldehyde. According to this method, the condensate (s) enriched in acetaldehyde can be distilled to concentrate the acetaldehyde to a higher concentration and to separate or remove the condensed acetaldehyde. For example, a condensate of at least one out of one second and subsequent condensers out of the plurality of condensers can be distilled to separate a column top effluent containing acetaldehyde (a column top effluent enriched in acetaldehyde). In this case, the condensate can be separated into a column top effluent and a liquid stream (or bottom stream) by distillation. In addition, the gas phase can be condensed by a plurality of condensers, a condensate from at least one first condenser can be stored in a decanter, a condensate from at least one of a second and subsequent condensers (for example, a last condenser) (for example, an acetaldehyde-enriched condensate) can be stored in a storage tank, the liquid stored in the decanter and the liquid stored in the storage tank can be combined and distilled to separate a column top effluent containing acetaldehyde. In addition, for the purpose of effectively separating and removing acetaldehyde, a condensate of at least one of a second and subsequent condensers (for example, a last condenser) among the plurality of condensers can be distilled to form a column top effluent containing acetaldehyde (a column top effluent enriched in acetaldehyde), and the column top effluent can be subjected to extraction with water to form an aqueous phase containing acetaldehyde and an organic phase.
[0025] Q Vgtoq "wo ugiwpfq g uwdugswgpVgu eqpfgpucfqtgu" means, assuming that the number of capacitors is n (capacitors n1, n2, n3, ..., nn), second, third, ..., nth capacitors (capacitors n2 , n3, ..., nn) except for a first capacitor (capacitor n1). This hqtoc. q vgtoq "wo g ugiwpfq uwdugswgpvgu eqpfgpucfqtgu" rqfg ugt tgguetkvq eqoq "wo g ugiwpfq uwdugswgpvgu eqpfgpucfqtgu swg rqfgo eqpvgt WO únvkoq eqpfgpucfqt" Ug púogtq q p q fi 4. Vgtoq "wo g ugiwpfq uwdugswgpVgu eqpfgpucfqtgu" wo ukipkhkec úpkeq eqpfgpucfqt kuVq * fi. second capacitor).
[0026] Q Vgtoq “hcug icuquc” rqfg ugt ejcocfc fg q “eqorqpgpVg de hcug icuquc” 0
[0027] Qu Vgtoqu “low volatility phase” g “hcug xqnáVü” rqfgo be ejcocfqu fg “low volatility phase component” g “volatile phase component”. tgurgeVkxcogpVg0
[0028] Q Vgtoq "ghnwgpVg fg Vqrq fg eqnwpc" rqfg ugt ejcocfq fg "eqorqpgpVg gflwgpVg fg Vqrq fg eqlwpc"
[0029] Q Vgtoq "eqpfgpucfq" rqfg ugt ejcocfq fg "eqorqpgpVg condenscfq"
[0030] It is also to be understood that as used here and in tgkxkpfkec> õgu go cpgzq, cu fqtocu pq ukpiwlct “wo”, “woc”, “q” g “c” include references in the plural unless the context clearly indicate fg qwvtq oqfq0 C lgvtc “u” cr „u wo uwduvcpvkvo designates both singular and plural forms of that noun. EFFECTS OF THE INVENTION
[0031] According to the present invention, since a gas phase containing at least acetaldehyde is condensed by a plurality of condensers to separate and remove acetaldehyde from a condensate (s) enriched in (enriched with) acetaldehyde , acetic acid can be produced with effectively enhanced acetaldehyde removal. In addition, since the gas phase is condensed by the plurality of condensers to form sequentially lower condensates at temperature, acetaldehyde can be effectively condensed and removed from a process stream in a simple way, and in this way a highly acetic acid can be produced. purified. In addition, condensation of the gas phase with the use of a plurality of condensers results in high concentrations of acetaldehyde and methyl iodide, which have very close boiling points. In this way, acetaldehyde can be effectively removed, and high quality acetic acid can be produced. In addition, the condensation of the gas phase by the plurality of condensers effectively separates liquid-liquid from an aqueous phase (or upper phase) having highly concentrated acetaldehyde and an organic phase (or lower phase) containing methyl iodide. Thus, the combination of condensates enriched with acetaldehyde (or separate condensates) formed in the plurality of condensers with distillation and / or extraction with water effectively separates and removes acetaldehyde from the aqueous phase and produces a high quality acetic acid with effective recycling of iodide of methyl for a reaction system. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] [Fig. 1] Fig. 1 is a diagram to explain an acetic acid production process (or production apparatus) according to an embodiment of the present invention.
[0033] [Fig. 2] Fig. 2 is a diagram to show an absorption system indicated in Fig. 1.
[0034] [Fig. 3] Fig. 3 is a diagram for explaining a production process (or production apparatus) for acetic acid according to another embodiment of the present invention. DESCRIPTION OF MODALITIES
[0035] Hereinafter, the present invention will be explained in detail with reference to the drawings. Fig. 1 is a diagram (a flow chart, a schematic process drawing, or a schematic layout drawing of the manufacturing unit) to explain a production process to (or production apparatus) of acetic acid according to a modality of present invention.
[0036] The modality of Fig. 1 shows a continuous process (or apparatus) to produce acetic acid from a liquid reaction medium (or reaction mixture) produced by a continuous carbonyl reaction of methanol with carbon monoxide in the presence of a catalyst system comprising a rhodium catalyst as a metal catalyst and a cocatalyst [lithium iodide as a metal halide and methyl iodide], as well as acetic acid, methyl acetate, and a (limited) finite amount of Water.
[0037] The process (or production apparatus) comprises a reactor (reaction system) 1 to carry out the methanol carbonylation reaction; a flasher 2 to separate the reaction mixture (or a reaction solution) containing the acetic acid product in a volatile phase (or lower boiling point component) (2A) containing the acetic acid product, methyl iodide, acetate methyl and water, and the low volatility phase (or highest boiling point component) (2B) containing the rhodium catalyst and lithium iodide; a separator column (distillation column) 3 to separate the volatile phase (2A) from flasher 2 into a column top effluent (or first column top effluent, gas stream, lowest boiling point component) (3A) containing methyl iodide, methyl acetate, acetaldehyde by-product, water and others, an acetic acid stream or phase (3B) containing acetic acid as a side stream, and a liquid stream (bottom stream, highest boiling point component) ) (3C) containing acetic acid, water, propionic acid, and others; a decanter 4 to condense the first column-top effluent (3A) and temporarily retain or store the condensate (liquid component); a buffer tank 5 for temporarily storing (or retaining) the condensate (or a lower or upper phase formed by the phase separation of the condensate in the decanter 4) from the decanter 4; a distillation column [or acetaldehyde separation (or removal column)] 6 to separate condensate from decanter 4 and / or buffer tank 5 (or a lower or upper phase formed in decanter 4 and / or the buffer tank 5) in a second column top effluent (gas stream, lowest boiling point component) (4A) containing acetaldehyde and methyl iodide and a liquid stream (bottom current or highest boiling point component) (4B ) containing methyl iodide, methyl acetate, water, acetic acid, and others; a buffer tank 7 to temporarily store (or retain) the bottom stream (4B) of the distillation column 6; and an extraction column (extraction unit or extractor) 8 to subject the second column top effluent (4A) to extraction with water to form an aqueous phase (light phase) containing acetaldehyde and an organic phase (heavy phase) containing iodide of methyl and to recycle the organic phase (heavy, refined phase) to reactor 1. In addition, the process (or production apparatus) shown in Fig. 1 also comprises a storage tank 9 for storing condensate formed by cooling the volatile phase (2A) of flasher 2 to recycle the condensate to reactor 1; and an absorption system for treatment of absorption of an exhaust gas generated from the process.
[0038] From now on, the process shown in Fig. 1 will be explained in more detail.
[0039] To reactor 1, methanol as a liquid component and carbon monoxide as a gaseous reagent are continuously fed at predetermined flow rates. In addition, to reactor 1, a catalyst mixture (liquid catalyst mixture) containing a carbonylation catalyst system [a catalyst system comprising a main metal catalyst component (for example, a rhodium catalyst) and a cocatalyst (for example lithium iodide and methyl iodide)] and water can be fed.
[0040] Within reactor 1, a methanol carbonylation reaction proceeds with the formation of an equilibrium between a liquid phase reaction system containing the reagents and the highest boiling point component such as the metal catalyst component (eg example, a rhodium and lithium iodide catalyst) and a gas phase system comprising carbon monoxide, by-products (hydrogen, methane, carbon dioxide), and a vaporized lower boiling point component (eg methyl iodide , acetic acid as a product, and methyl acetate). In order to keep the internal pressure of reactor 1 (for example, reaction pressure, partial pressure of carbon monoxide, and partial pressure of hydrogen) constant, an exhaust gas (residual gas) A is removed and discharged from the top of the reactor 1, and the exhaust gas (waste gas) A is fed to the absorption system.
[0041] Components in the reaction mixture (crude reaction solution) of reactor 1 may include acetic acid, a lower boiling point component or an impurity having a lower boiling point than that of acetic acid (for example, methyl iodide as a cocatalyst, methyl acetate as a reaction product of acetic acid with methanol, water, and acetaldehyde as a by-product), and a higher boiling point or impurity component having a higher boiling point than that of acetic acid [for example, a metal catalyst component (for example, a rhodium catalyst), lithium iodide as a cocatalyst, and a C3-12 carboxylic acid as propionic acid]. In addition, several by-products derived from acetaldehyde, for example, an aldehyde compound (such as crotonaldehyde or 2-ethylcrotonaldehyde) is underproduced, and a C2-12 alkyl iodide (such as ethyl iodide, propyl iodide, butyl iodide, butyl iodide pentyl, hexyl iodide) is also underproduced. Therefore, it is preferable to separate and remove acetaldehyde, which is a major component to produce by-products of the reaction mixture and to recover (or collect) a useful component (eg, methyl iodide) from the process stream for effective reuse.
[0042] A portion of the reaction mixture is continuously removed from reactor 1 and introduced or fed to the flasher (distillation column or catalyst separation column) 2 via a power line 11 for flash distillation.
[0043] In the flasher (flash distillation column) 2, the reaction mixture is separated into a volatile phase (lower boiling current) (2A) (predominantly containing acetic acid, which is a product and also acts as a reaction solvent, methyl acetate, methyl iodide, water, methanol, acetaldehyde, and others) and a less volatile phase (higher boiling current) (2B) (predominantly containing the metal catalyst component as the catalyst). rhodium and lithium iodide, and others), and the low volatility phase (2B) is recycled to reactor 1 via a bottom line 21 from the bottom of the flasher, and the volatile phase (2A) (current predominantly containing acetic acid) is continuously fed or introduced into the separator column (or distillation column) 3 via a feed line 22 from the top or top of the flasher 2. Incidentally, the low volatility phase (2B) also contains, in addition to the metal catalyst (the rhodium catalyst) and the halide of metal (lithium iodide), non-evaporated components (for example, methyl iodide, methyl acetate, water, and a trace of acetic acid). In this embodiment, the amount of the volatile phase (2A) to be separated in flasher 2 is about 20% to 40% by volume of the entire reaction mixture.
[0044] A portion of the volatile phase (2A) is fed to a first condenser (cooling condenser, heat exchanger) C1 having a predetermined condensing temperature via a line 23 to condense and separate the volatile phase by cooling in a first condensate and a first non-condensed gaseous component having a high acetaldehyde concentration. The condensate can be separated into two liquid phases. The first condensate is fed to the storage tank 9 mentioned below. In addition, the first non-condensed gaseous component is fed to a second condenser (cooling condenser, heat exchanger) C2 having a lower temperature than that of the first condenser C1 via a line 26 to separate into a second condensate having highly concentrated acetaldehyde and a second non-condensed gaseous component. The condensate can be separated into two liquid phases. Such a plurality of condensation operations can form a condensate enriched in acetaldehyde (or a condensate having a high acetaldehyde concentration). A portion of the second condensate is fed to the decanter 4 via decanter lines (a line 27 and a bypass line 28), and another portion thereof is fed to the buffer tank (or storage tank) 5 via a line 29 attached to the line 27. At least a portion (portion or whole) of the second condensate is fed to an acetaldehyde removal step [distillation column (acetaldehyde removal column) 6]. In more detail, the second condensate is fed to the distillation column (acetaldehyde removal column) 6 via a line and a unit (for example, lines 27, 28, 29, the decanter 4, the buffer tank 5, and line 52) for an acetaldehyde removal treatment. The second non-condensed gaseous component is sent as an exhaust gas B to the absorption system.
[0045] In the embodiment shown in Fig. 1, the production process (or production apparatus) of acetic acid comprises a storage container (storage tank) 9 for storing the condensate that is formed by cooling and condensing a portion of the volatile phase (2A) of the flasher 2, and the condensate (component with heat removed and condensate) is recycled from the storage container 9 to the reactor 1 to control the reaction temperature. In more detail, a portion (for example, about 10% to 30% by volume) of the volatile phase (2A) is cooled (or with heat removed) and condensed in the first condenser (cooling condenser, heat exchanger) C1; the resulting condensate is stored in the storage tank 9 via a line 24; and the stored condensate is recycled to reactor 1 via a line 25. In this way, condensation or removal of heat from a portion of the volatile phase (2A) and recycling of the resulting condensate to the reactor facilitates the temperature control of reactor 1 in which an exothermic reaction occurs, and can reduce the loading to the separator column (for example, the distillation column) 3 even in a large production unit. In addition, since the volatile phase can be condensed into a liquid having a smaller volume, an apparatus such as the separating column (for example, the distillation column) 3 can be undersized (or miniaturized). In this way, acetic acid can be produced with high purity and high performance in equipment that saves energy and saves resources.
[0046] In the separating column (distillation column) 3, the volatile phase (2A) of the flash distillation is separated into a column top effluent (column top effluent gas, component or lowest boiling current) ( 3A) (containing at least methyl iodide and acetaldehyde, usually methyl iodide, methyl acetate, acetaldehyde, water, methanol, acetic acid, and others) removed from a top or top of the column via a withdrawal line 32 , a side stream or phase stream of acetic acid (acetic acid stream) (3B) which is recovered via a feed line 40 by the side cut and predominantly contains acetic acid, and a bottom liquid stream (component or stream) highest boiling point) (3C) (a liquid phase containing at least water and methanol, usually a component containing acetic acid, water, methanol, propionic acid, and others) removed from the bottom or bottom of the column via a bottom line 31.
[0047] In this embodiment, the amount of column top effluent (3A) separated in the separating column 3 is about 35% to 50% by weight in the total volatile phase (2A). In addition, as described below, when a process liquid from the subsequent step (s) is recycled to the separator column 3, the total amount of the volatile phase (2A) fed from the flasher 2 and the recycled component from the (s) Subsequent step (s) is subjected to distillation on the separating column 3 to form the column top effluent (3A).
[0048] The acetic acid stream (3B) is fed to the other distillation column (not shown) via line 40 and then distilled for further purification. In addition, the bottom liquid stream (component or highest boiling current) (3C) can be discharged via line 31. In this embodiment, the bottom liquid stream (3C) is partially or completely recycled to the reactor 1 via a 90 line.
[0049] The column top effluent (3A) contains acetaldehyde and methyl iodide, in addition, acetic acid, methyl acetate, water, methanol, other impurities [for example, an aldehyde or a carbonylized impurity (such as crotonaldehyde or butylaldehyde ), a C2-12 alkyl iodide, and a C3-12 carboxylic acid] in practical cases. The column top effluent (3A), which is a column top effluent gas from the separating column 3, is fed to the first condenser C3 via the withdrawal line 32, cooled and condensed at a predetermined temperature, and separated into a first condensed and a first non-condensed gaseous component having a high acetaldehyde concentration (or having enriched acetaldehyde). The first condensate is continuously fed to the decanter (decanter, storage vessel) 4 via a line 33 and temporarily retained (stored).
[0050] Additionally, the first non-condensed gaseous component is fed to a second condenser C4 via lines 34, 35. In the second condenser C4, the component is cooled and condensed at a lower temperature than that of the first condenser C3 to form a second condensate enriched in acetaldehyde and a second non-condensed gaseous component, which are separated from each other.
[0051] A portion of the second condensate is fed to the decanter 4 via a decanter line (in the mode shown, a line 36 and a line 39 derived from line 36 (line 39 is joined to line 28 on a downstream side)) , and another portion thereof is fed to the buffer tank (or storage tank) 5 via a first buffer tank line (in the mode shown, lines 37 and 38 extending in a direction downstream of the line 39 bypass point ( a line 38 joined to lines 29, 36, 37 on one side upstream)). The second condensate in the decanter 4 (in a case in which the condensate is separated into two liquid phases (or layers), an upper phase and / or a lower phase) can be fed to the buffer tank (or storage tank) 5 via a second buffer tank line (in the embodiment shown, lines 41, 43a or lines 44, 44b, 43a).
[0052] At least a portion (whole or portion) of the second condensate is fed to the acetaldehyde removal step [distillation column (acetaldehyde removal column) 6]. In more detail, the second condensate is fed to the distillation column (acetaldehyde removal column) 6 via a line and a unit (for example, lines 39, 38, decanter 4, buffer tank 5, and lines 52, 53) for an acetaldehyde removal treatment. The second non-condensed gaseous component is sent as an exhaust gas (waste gas) C to the absorption system. In addition, the non-condensed gaseous component of the decanter 4 is also sent as an exhaust gas (waste gas) D to the absorption system.
[0053] The volatile phase (2A) and the column top effluent (3A) are cooled and condensed by a plurality of cooling condensers to effectively condense acetaldehyde. More specifically, in the production of acetic acid, the process stream (mixture), such as the volatile phase (2A), the column top effluent (3A), and other streams, contain several components with different boiling points, for example , acetic acid (118 ° C), water (100 ° C), methanol (64.1 ° C), methyl acetate (57.5 ° C), methyl iodide (42.5 ° C), acetaldehyde (21 ° C), dimethyl ether (-23.6 ° C), and hydrogen iodide (-35.4 ° C). The boiling point is given in parentheses. Among these components, hydrogen iodide and dimethyl ether, which usually exist in smaller quantities, have a boiling point no higher than 0 ° C, and acetaldehyde has a boiling point close to that of methyl iodide. Thus it is difficult to separate and remove only and preferably acetaldehyde from the mixture by simple distillation. In addition, even if the process stream (steam mixture) is cooled by a single cooling condenser to form a condensate containing acetaldehyde, several wide range components are condensed and liquefied. Thus, acetaldehyde cannot be effectively separated from the condensate.
[0054] In contrast, the plurality of capacitors C1 and C2 (and / or C3 and C4), being sequentially lower in cooling temperature in the further downstream direction, can condense a predetermined component depending on the cooling temperature of each capacitor to separate a condensed component from a gas phase. For example, a first condensate (for example, a condensate predominantly containing acetic acid, water, methanol, and others) can be separated from a first non-condensed component (for example, a gas component predominantly containing methyl acetate, methyl iodide, acetaldehyde, and others) by a first C1 or C3 condenser set to a condensation temperature of about 25 ° C to 100 ° C. Additional cooling of the first non-condensing component (lowest boiling point component) by a second condenser C2 or C4 adjusted to a condensing temperature of about -10 ° C to 50 ° C can separate a second condensate containing a concentrate from a predetermined lower boiling point component (for example, a condensate predominantly containing methyl acetate, methyl iodide, acetaldehyde, and the like) of a second non-condensed gaseous component (for example, a gaseous component containing traces of methyl iodide and acetaldehyde, and others).
[0055] In particular, the use of a plurality of capacitors can form a condensate enriched in acetaldehyde (or a condensate having a high concentration of acetaldehyde). For example, in the case in which two capacitors, C3 and C4, are used for condensation, a first condensate formed in the first capacitor C3 (in a case in which a condensate is separated into two liquid phases (or layers), an entire mixture of an upper and a lower phase) has an acetaldehyde concentration of, for example, 0.1% to 0.2% by weight. A condensate formed in a single condenser also has the same concentration of acetaldehyde. In contrast, in a second condensate formed in the second condenser C4 (in a case in which a condensate is separated into two liquid phases (or layers), an entire mixture of an upper and a lower phase), acetaldehyde can be concentrated to one concentration 1.2 times or more (for example, 1.5 to 3 times) higher than that of the first condensate (the whole mixture mentioned above). For example, the second condensate can have an acetaldehyde concentration of 0.15% to 0.5% by weight.
[0056] In the case in which the first condensate in the first condenser C3 is separated into two liquid phases (or layers), the upper phase can have an acetaldehyde concentration of about 500 to 5,000 ppm, preferably about 1,000 to 4,000 ppm, and more preferably about 1,200 to 3,000 ppm, and the lower phase can have an acetaldehyde concentration of about 200 to 3,000 ppm, preferably about 400 to 2,500 ppm, and more preferably about 500 to 2,000 ppm. In contrast, in the case where the second condensate in the second condenser C4 is separated into two liquid phases (or layers), the upper phase may have an acetaldehyde concentration of about 2,000 to 15,000 ppm and preferably about 3,000 to 12,000 ppm ( for example, about 5,000 to 10,000 ppm), and the lower phase can have an acetaldehyde concentration of about 1,000 to 5,000 ppm and preferably about 1,500 to 4,000 ppm.
[0057] In decanter 4, the first condensate of the first condenser C3 does not necessarily need to form separate liquid phases (layers). The first condensate usually forms an upper layer (aqueous phase) predominantly containing water and acetaldehyde (and an aldehyde) and a lower layer (organic phase) predominantly containing methyl iodide. Even if the first condensate is separated into two liquid phases (or layers), acetaldehyde and methyl iodide will be contained in both layers in a small amount. The volume ratio of the top layer (or aqueous phase) to the bottom layer (or organic phase) can be, for example, about 0.5 / 1 to 1.5 / 1 (for example, about 0.7 / 1 to 1.3 / 1) as the top layer / bottom layer.
[0058] The condensate in the decanter 4 is supplied to a buffer tank line (a line 43 derived from a line 41, a line 43a derived from line 43), and at least a portion of the condensate (particularly the upper phase and / or the lower phase, for example, the lower organic phase) is fed to the buffer tank 5.
[0059] The decanter 4 for storing the first condensate of the first condenser C3 plays an important role in the process according to the present invention. Specifically, for decanter 4, the first condensate from the first condenser C3 is fed via the feed line 33, the second condensate, having a high acetaldehyde concentration, from the second condenser C4 is fed via the line 39, and these condensates can be converged and stored in the decanter 4. Thus, the control of the condensate flow rates to be lines 33 and 39 allows the stable operation of the entire process, including the distillation column 6, and improvement of the acetaldehyde removal efficiency (amount of removal acetaldehyde).
[0060] The second condensate, having a high acetaldehyde concentration, of the second condenser C4 does not necessarily need to be fed to the decanter 4.
[0061] In addition, the rest of the condensate (the condensate not fed to the buffer tank 5) can be fed to the distillation column 6 via a feed line (a line 43b derived from line 43). The condensate can be fed to the distillation column 6 via another route. For example, the condensate in the decanter 4 is fed to the distillation column 6 depending on the acetaldehyde concentration or composition, if necessary, via a feed line (for example, feed lines 44, 44b and / or feed lines 41, 43, 43b, 52) to remove acetaldehyde. Specifically, a portion of the condensate (particularly, the upper aqueous phase) can be fed to the distillation column 6 via a feed line (for example, lines 44, 44b).
[0062] In addition, the condensate can be fed to reactor 1. For example, the condensate (particularly the lower organic phase) in the decanter 4 can be recycled to reactor 1 via a recycling line 90 via lines 41 and 42 In addition, a portion of the condensate (particularly the upper phase and / or the lower phase, for example, the upper aqueous phase) can be returned to reactor 1 via a recycle line (a recycle line 90 via lines 44 , 44a and a bypass line 45b derived from line 44a).
[0063] In addition, the condensate can also be fed to the separating column 3. For example, a portion of the condensate in the decanter 4 (particularly the upper aqueous phase) can be recycled to the separating column 3 via a recycling line (the line 44, bypass line 44a derived from line 44, a bypass line 45a derived from line 44a, and a recycle line 46). A portion of the condensate (particularly, the upper aqueous phase or the lower organic phase) can be recycled for each of the separating column 3 and the reactor 1 via these recycling lines (lines 45a and 45b).
[0064] According to the modality of Fig. 1, the fluctuation of the stored quantity (or fluctuation of the liquid level) of the condensate in the decanter 4 is eliminated. Specifically, the fluctuation of the stored quantity (or liquid level) of the condensate in the decanter 4 is eliminated (or controlled) by recycling a portion of the condensate to the reactor 1 and / or the separating column 3 or others via a recycling line. (for example, line (underline) 44a derived from line 44 or line (underline) 42 derived from line 41) based on the fluctuation of the condensate flow to the decanter 4.
[0065] For the buffer tank (storage tank) 5, the volatile phase condensate (2A) and / or that of the column top effluent (3A) is fed via line 38, and the condensate enriched in acetaldehyde is stored in storage tank 5. In addition, condensate from decanter 4 does not necessarily need to be fed to buffer tank 5, and condensate from decanter 4 can usually be fed to storage tank 5 via line 43a.
[0066] The condensate in the buffer tank 5 is fed at least to the distillation column (aldehyde removal column) 6 to form a second column top effluent rich in acetaldehyde. The condensate [articularly, in a case in which the condensate is separated into two liquid phases (or layers), an upper phase (aqueous phase) and / or a lower phase (organic phase)) can be fed to the distillation column (column aldehyde removal) 6 via a feed line (lines 54, 56, lines 51, 52, 53).
[0067] In the case in which the condensate from line 43a is temporarily stored in the buffer tank 5 and fed to the distillation column 6 via a certain line, the fluctuation of the condensate flow (condensate component) can be effectively reduced in the buffer tank 5, so that the condensate can be fed from the buffer tank 5 to the distillation column 6 at a predetermined (or substantially constant) flow rate.
[0068] As described above, since the flow fluctuation of the condensate in line 43a is significantly inhibited, the condensate can be directly fed to the distillation column 6. In the modality shown in Fig. 1, with the purpose of additionally reducing the fluctuation of the flow, the condensate is indirectly fed to the distillation column 6 through a storage container (buffer tank) 5 having a buffer function. That is, the condensate from line 43a is temporarily stored in the buffer tank 5 and then fed to the distillation column 6 via a given line 53. In this way, the condensate can be fed from the buffer tank 5 to the distillation column 6 via the given line 53 at a predetermined (or substantially constant) flow steadily while effectively eliminating the flow fluctuation of the condensate to be fed from line 43a to the buffer tank 5.
[0069] The buffer tank (or storage tank) 5 for storing the second condensate of the second condenser C4 plays an important role in the process according to the present invention. In more detail, to the supply line (lines 36, 37, 38, particularly line 38), the following lines are joined: line 37 to feed the second condensate (condensate after being bypassed by the bypass line 39) of the second condenser C4, line 29 to supply the second condensate of the volatile phase (2A) formed in the second condenser C2, and a line 112 to supply the exhaust gas condensate A to E. Thus, the condensate having a high acetaldehyde concentration can be stored (or retained) in the buffer tank (or storage tank) 5, and distillation of the condensate in the distillation column 6 can distill or effectively remove acetaldehyde. In addition, the apparatus shown in Fig. 1 is equipped with the feed line 43a to feed the condensate to the storage tank 5 and the feed line 43b to feed the condensate to the distillation column 6, and the amount of acetaldehyde removal. it can be controlled by adjusting the flow of condensate in these lines to increase the amount of acetaldehyde removal.
[0070] Additionally, the condensate (concentrate) having a high acetaldehyde concentration stored in the storage tank 5 and the condensate stored in the decanter 4 can be joined and distilled by the distillation column 6 to increase the amount of acetaldehyde removal with the column. distillation unit 6 stably operated, depending on the ratio of condensate from decanter 4 to condensate (concentrate) from storage tank 5. For example, the amount of acetaldehyde removal can be significantly increased by distillation of condensate (concentrate) stored in the tank In addition, due to the fact that the ratio of condensate from decanter 4 to condensate (concentrate) from storage tank 5 is greater, the amount of acetaldehyde removal is reduced compared to the removal of acetaldehyde from only the condensate in the storage tank 5 (but the amount is even greater than the conventional removal amount), while However, the amount of total acetaldehyde removal can be increased with the distillation column 6 stably operated.
[0071] However, the condensate can also be returned to the separating column 3 or the reactor 1. For example, the condensate in the buffer tank 5 (particularly, for example, in the case in which the condensate is separated into two phases (or liquid layers, an upper phase or aqueous phase) can be recycled to the separating column 3 via a recycling line (line 54, line 57 and recycling line 46). In addition, the condensate (for example, in a case in which the condensate is separated into two liquid phases (or layers), a lower phase or organic phase) can be returned to reactor 1 via a recycle line (lines 58 and 90). The condensate (particularly, in a case in which a condensate is separated into two liquid phases (or layers), an upper phase or aqueous phase) can be returned to reactor 1 via a recycle line 55, which is derived from line 54 and connected to the 90 recycling line.
[0072] The gas expelled (exhaust gas) from the storage tank 5 is fed, via a line 59, to the supply line 34, which is located on an upstream side of the second capacitor C4, between the first capacitor C3 and the second capacitor C4. Line 35 is connected from the joined portion of these lines to the second capacitor C4. Line 59 can be joined to a side upstream of the first capacitor C3. If necessary, the expelled gas can be fed as an exhaust gas to the absorption system.
[0073] The condensate fed to the distillation column 6 (in the manner shown in Fig. 1, the lower phase and / or upper phase in the decanter 4 and the lower phase and / or upper phase in the buffer tank 5) is separated into a second column-top effluent (or lowest-boiling point component or stream) (4A) and the bottom current (liquid, highest-boiling point component or stream) (4B) in the distillation column 6; the second column top effluent (4A) contains acetaldehyde, a trace of methyl iodide, hydrogen iodide, dimethyl ether, carbon monoxide, hydrogen, and others, and the bottom stream (4B) contains methyl iodide, acetate methyl, water, acetic acid, and others. The second column top effluent (4A) is fed from a top or top of the column to a condenser C5 via a line 63 for cooling and condensation. A portion of the condensate is fed to the acetaldehyde extraction unit (water extraction column) 8 via a line 65, and another portion is returned and refluxed to the distillation column (aldehyde removal column) 6 via a line 64 In addition, the non-condensing gaseous component of condenser C5 is fed as an exhaust gas E to the absorption system.
[0074] Bottom current (highest boiling current) (4B), which is a residual liquid (bottom fraction or column bottom fraction), is fed to line 90 to reactor 1 or column separator 3 with or without being fed to the buffer tank 7 via a line 61.
[0075] In the distillation column 6, the condensate can be distilled without passing through the decanter 4 and / or the buffer tank 5.
[0076] In the acetaldehyde extraction unit (water extraction column) 8, the second column top effluent (4A) having acetaldehyde concentrated in the distillation column 6 is placed in contact with water (as shown in Fig. 1 , the second column top effluent (4A) is in countercurrent contact with the water fed from a lower part of the water extraction column 8) to extract the acetaldehyde with water, thus forming an aqueous phase current (light phase, aqueous aldehyde solution) and an organic phase (heavy, refined phase) containing methyl iodide. The organic phase (heavy phase, refined) is removed from a line 81 at the bottom of the extraction column with water 8, and fed to the distillation column 6 via a line 82 and / or recycled to reactor 1 through a line of recycle 90 via a line 83. In this way, the distillation and / or recycling of the organic phase (heavy, refined phase) can additionally increase the percentage recovery of methyl iodide. In addition, since the bottom current (highest boiling current) (4B) of the distillation column 6 can also be recycled to reactor 1 via recycle line 90, a useful component containing methyl iodide can be used effectively. The aqueous phase stream (light phase) having a high concentration of acetaldehyde can be discharged via a line 84.
[0077] At least a portion (portion or totality) of the organic phase (heavy, refined phase) (4B) fed to the recycling line 90 can be recycled to the separating column 3 via a line 91 derived from the recycling line 90. As long as stable operation of the distillation column 6 is guaranteed, at least a portion (portion or totality) of the organic phase (heavy, refined phase) (4B) fed to line 90 or 91 can be fed to the distillation column 6 via a line 92.
[0078] Exhaust gas (residual gas) A from reactor 1, exhaust gas B (second gas component, non-condensing component) formed by cooling and condensation of the volatile phase of flasher 2, exhaust gas C (second component gas, non-condensing component) formed by cooling and condensing the first column-top effluent of the separating column 3, the exhaust gas D from the decanter 4 or the storage tank 5, and the exhaust gas E (gaseous component, non-component) condensate) formed by cooling and condensing the second column top effluent of the distillation column 6 contain traces of acetaldehyde and methyl iodide, and others. The residual gas (exhaust gas A) of the pressurized reactor 1 has a higher pressure than that of the exhaust gases B to E. Thus, the exhaust gas (residual gas) A of the reactor 1 is fed to an absorption column of high pressure 101 via a line 105 and is treated in the manner of absorption with an absorption solvent (methanol and / or acetic acid) fed from a line 104 by the gas-liquid contact to form a mixture containing acetaldehyde, methyl iodide and others that are absorbed in the solvent. This mixture is taken from a bottom line 107 of the high pressure absorption column 101 and fed to a diffusion column (extraction column or extractor) 103 via line 109.
[0079] In addition, exhaust gases B to E are joined (or converged) and fed to a low pressure absorption column 102 via a line 106 and are treated in the manner of absorption with an absorption solvent (methanol and / or acetic acid) fed from a line 104 by the gas-liquid contact to form a mixture containing acetaldehyde, methyl iodide and others that are absorbed in the solvent, as described above. This mixture is removed from a bottom of the low pressure absorption column 102 via a line 108 and fed to the diffusion column (extraction column or extractor) 103 via line 109.
[0080] In the diffusion column (extraction column or extractor) 103, an extraction treatment is carried out, and the gas stream (5A) containing acetaldehyde and methyl iodide is removed from the top of the column via a line 111. The gas stream (5A) is cooled by a first condenser C6 to form (separate into) a condensate and a non-condensed gaseous component. The condensate is fed to the distillation column (acetaldehyde removal column) 6 via a line 112. In this embodiment, the condensate is fed, via line 112, to the distillation column (acetaldehyde removal column) 6 via the decanter 4, the storage tank 5 and the above mentioned line (s).
[0081] This process (or production apparatus) forms a closed system production process to effectively remove a useful component and to effectively separate and remove an impurity component from the process stream.
[0082] Fig. 3 is a diagram to explain another embodiment of the present invention. For explanation, the same element as that in Fig. 1 is denoted by the same reference number as that in Fig. 1.
[0083] In this embodiment, the process diagram is different from that shown in Fig. 1 and Fig. 2 in that (i) the process diagram does not comprise buffer tanks 5 and 7, a storage tank 9 and a system absorption for exhaust gases A to E and (ii) the process diagram additionally provides a distillation column 10 in addition to a distillation column (acetaldehyde removal column) 6.
[0084] Specifically, for a decanter 4, a volatile phase condensate (2A) from a flasher 2 (a condensate formed by sequential cooling and condensation of the volatile phase (2A) in capacitors C1, C2) is fed via a supply line bypass (lines 27, 28), and a condensate from a first column top effluent (3A) of a separator column (distillation column) 3 (a condensate formed by sequential cooling and condensation of a first column top effluent (3A) in capacitors C3, C4) is fed via lines 33, 39. In the decanter 4, the condensate forms two layers. At least a portion of an upper phase (aqueous phase) containing acetaldehyde can be fed to the separator column 3 via a feed line (lines 44, 46) to form a first column top column effluent from column 3, and the plurality of condensers C3, C4 can additionally concentrate the acetaldehyde. In addition, by cooling at least a portion of the upper phase (aqueous phase) to the distillation column 6 via lines 44, 56 and subjecting the second column top effluent formed to the water extraction by the water extraction column 8, acetaldehyde can be removed from the light phase (aqueous stream).
[0085] Additionally, a portion of the lower phase (organic phase) containing methyl iodide in the decanter 4 is recycled to a reactor 1 via recycling lines (lines 42, 90), and another portion of the lower phase (organic phase) is fed to the distillation column 6. A second column-top effluent component formed by the distillation is subjected to water extraction by the water extraction column 8 to purify the heavy (refined) phase which is then recycled to reactor 1. The upper phase and / or the lower phase in the decanter 4 can be fed to the distillation column 6.
[0086] The acetaldehyde removed from the top or top of the water extraction column 8 is fed to the aldehyde removal column 10. In the aldehyde removal column 10, a fraction of acetaldehyde from the top or top of the column and water (or aqueous stream) and a bottom or bottom part of the column are separated. The separated water (or aqueous stream) is fed to the water extraction column 8 via a line 10a and used for the extraction of acetaldehyde in the water extraction column 8.
[0087] Also in this process, since the condensate (concentrate) enriched in acetaldehyde from the plurality of condensers is subjected to distillation and extraction with water by the distillation column 6, the extraction column with water 8, and the aldehyde removal column 10, acetaldehyde can be effectively removed from the process stream. In addition, since the condensate (concentrate) is also rich in methyl iodide, the effectiveness of methyl iodide recovery can also be improved. In this way methyl iodide can be used effectively.
[0088] From now on, each stage and device will be explained in detail. [Reaction step]
[0089] In the reaction step, it is sufficient to continuously carbonize methanol with carbon monoxide in a reaction medium containing a carbonylation catalyst system (particularly, a rhodium catalyst and a cocatalyst containing lithium iodide and methyl iodide) and water . The reaction medium usually contains methyl acetate, acetic acid, and water.
[0090] The carbonylation catalyst system can usually comprise a metal catalyst (particularly, for example, a cobalt catalyst, a rhodium catalyst, and an iridium catalyst), a cocatalyst, and an accelerator. The metal catalyst can be used in the form of a metal as a simple substance, a metal oxide (including a complex metal oxide), a hydroxide, an iodide, a carboxylate (for example, an acetate), a salt of an inorganic acid (for example, a sulfate, a nitrate, and a phosphate), a complex, and others. These metal catalysts can be used alone or in combination. The preferred metal catalyst includes a rhodium catalyst and an iridium catalyst (particularly, a rhodium catalyst).
[0091] It is preferable to use the metal catalyst in the form (the form as a complex) dissolvable in the reaction medium (reaction liquid). As the rhodium catalyst, a rhodium iodide complex [e.g., RhI3, [RhI2 (CO) 4] -, and [Rh (CO) 2I2] -], a carbonyl rhodium complex, or the like is preferred. The concentration of the metal catalyst is, for example, about 100 to 5,000 ppm (based on weight, the same applies hereinafter), preferably about 200 to 3,000 ppm, more preferably about 300 to 2,000 ppm, and particularly about 500 to 1,500 ppm in the entire liquid phase in the reactor. The metal catalyst can be stabilized in the reaction medium by the addition of an alkali metal iodide and / or water.
[0092] The cocatalyst or accelerator may include a metal iodide, for example, an alkali metal iodide (eg, lithium iodide, sodium iodide, and potassium iodide). The cocatalyst or accelerator preferably includes lithium iodide. Metal iodide (for example, an alkali metal iodide) functions as a stabilizer for the carbonylation catalyst (for example, a rhodium catalyst) under a low water content and is useful for inhibiting side reactions. These cocatalysts or accelerators can be used alone or in combination.
[0093] The concentration of the cocatalyst or accelerator is, for example, about 1% to 25% by weight, preferably about 2% to 22% by weight, and more preferably about 3% to 20% by weight in the liquid phase. whole in the reactor. In addition, the concentration of the iodide ion in the reaction system can be, for example, about 0.07 to 2.5 moles / liter and preferably about 0.25 to 1.5 moles / liter.
[0094] As the accelerator contained in the catalyst system, an alkyl iodide (for example, a C1-4 alkyl iodide is used as methyl iodide, ethyl iodide, or propyl iodide), particularly methyl iodide. Since the reaction is promoted at higher concentrations of the accelerator, the accelerator can be used in an economically advantageous concentration. The concentration of the alkyl iodide (particularly methyl iodide) is, for example, about 1% to 20% by weight, preferably about 5% to 20% by weight, and more preferably about 6% to 16% by weight (for example, about 8% to 14% by weight) in the entire liquid phase in the reactor.
[0095] The preferred carbonylation catalyst system may comprise a rhodium catalyst and a cocatalyst containing a metal iodide (lithium iodide) and methyl iodide.
[0096] The reaction medium (or liquid phase) usually comprises the acetic acid product, methyl acetate formed by the reaction of acetic acid product and raw material methanol, and water. Acetic acid also works as a solvent. In addition, the reaction medium (or liquid phase) usually contains raw material unreacted methanol. The proportion of methyl acetate can be about 0.1% to 30% by weight, preferably about 0.3% to 20% by weight, and more preferably about 0.5% to 10% by weight (e.g. , about 0.5% to 6% by weight) in the entire reaction liquid. The water concentration in the reaction system (reaction medium) can be a low concentration. The water concentration in the reaction system is, for example, about 0.1% to 15% by weight, preferably about 0.5% to 10% by weight, and more preferably about 0.5% to 5% by weight (for example, about 1% to 3% by weight) and can usually be about 1% to 15% by weight (for example, about 2% to 10% by weight) in the entire liquid phase of the reaction. Maintaining the specific concentration of the metal iodide (for example, an alkali metal iodide such as lithium iodide) and water in the reaction system can decrease the solubility of carbon monoxide in the liquid fed to the flasher (evaporator) and reduce the loss of carbon monoxide.
[0097] Carbon monoxide can be used as a pure gas or it can be used as a gas diluted with an inactive gas (eg nitrogen, helium, and carbon dioxide). In addition, the expelled gaseous component (s) containing carbon monoxide obtained from the subsequent step (s) can be recycled to the reaction system. The partial pressure of carbon monoxide in the reactor can be, for example, about 203 kilopascals (kPa) to 3,040 kilopascals and preferably about 405 kilopascals to 1,520 kilopascals.
[0098] The carbonylation reaction generates hydrogen by a reaction of carbon monoxide with water. Hydrogen increases catalytic activity. Thus, for reactor 1, if necessary, hydrogen can be fed. In addition, hydrogen can be fed into the reaction system by recycling gaseous component (s) (including hydrogen, carbon monoxide, and others) expelled in a subsequent step (s), if necessary after purification. of the gaseous component (s). The partial pressure of hydrogen in the reaction system can be, for example, about 0.5 kPa to 250 kPa, preferably about 1 kPa to 200 kPa, and more preferably about 5 kPa to 150 kPa (for example, about 10 kPa to 100 kPa) in terms of absolute pressure.
[0099] In the carbonylation reaction, the reaction temperature can be, for example, about 150 ° C to 250 ° C, preferably about 160 ° C to 230 ° C, and more preferably about 180 ° C to 220 ° Ç. In addition, the reaction pressure (total pressure in the reactor), including the partial pressures of by-products, can be, for example, about 1,520 kilopascals to 4,053 kilopascals.
[00100] According to the present invention, since acetaldehyde can be effectively separated and removed, the concentration of acetaldehyde in the reactor can be reduced despite the continuous reaction. For example, the concentration of acetaldehyde in the reactor can be no greater than 1,000 ppm (for example, 0 or detection limit for 700 ppm), preferably no greater than 400 ppm (for example, 5 ppm at 300 ppm), and most preferably about 10 ppm to 250 ppm in the entire liquid phase in the reactor.
[00101] In the reactor, by-products derived from acetaldehyde are also produced (for example, crotonaldehyde, which is a reducing substance, produced by condensation of acetaldehyde aldol; 2-ethylcrotonaldehyde produced by condensation of hydrogenated crotonaldehyde and acetaldehyde; and hexyl iodide produced by aldol condensation of three acetaldehyde molecules, hydrogenation and iodination). These by-products are often produced in proportion to the second to third potencies of the acetaldehyde concentration, and thus reducing acetaldehyde can effectively eliminate the formation of by-products. According to the present invention, since the fluctuation of the concentration of acetaldehyde in the reactor can also be inhibited while reducing the concentration of acetaldehyde, the formation of by-products derived from acetaldehyde can be significantly inhibited.
[00102] The space-time yield of the desired carboxylic acid (acetic acid) in the reaction system can be, for example, about 5 moles / Lh to 50 moles / Lh, preferably about 8 moles / Lh to 40 moles / Lh, and more preferably about 10 moles / Lh to 30 moles / Lh
[00103] Incidentally, the reaction system is an exothermic reaction system that accompanies heat generation, and the reaction temperature can be controlled by recycling the condensate with heat removed, installing a removable heat unit (or heat remover) or a cooling unit (for example, a jacket) to control the reaction temperature.
[00104] For the purpose of removing part of the reaction heat, a vapor component (exhaust gas) from the reactor can be cooled with a condenser, a heat exchanger or other medium and separated into a liquid component (containing acetic acid, acetate of methyl, methyl iodide, acetaldehyde, water and others) and a gaseous component (containing carbon monoxide, hydrogen and others), and the liquid component and / or the gaseous component can be recycled to the reactor. In addition, the vapor component (exhaust gas) can be removed from the top of the reactor, or it can be subjected to an absorption treatment to recover carbon monoxide, which can be recycled to the reactor. [Flash evaporation step]
[00105] In the flash evaporation step, it is sufficient to continuously remove the reaction mixture from the reaction step and to separate the reaction mixture into a volatile phase (the volatile phase containing acetic acid and methyl iodide) and a non-volatile phase ( the low volatility phase containing a high boiling catalyst component (a metal catalyst component, for example, a metal catalyst and a metal halide). The reaction mixture can be separated into the vapor component and the liquid component with or without heating. For example, in adiabatic flash, the reaction mixture can be separated into the vapor component and the liquid component without heating and under reduced pressure, and in thermostatic flash, the reaction mixture can be separated into the vapor component and the liquid component with heating and reduced pressure. The reaction mixture can be separated into the vapor component and the liquid component by the combination of these flash conditions. Flash distillation can be carried out, for example, at a temperature of about 80 ° C to 200 ° C under a pressure (absolute pressure) of about 50 kPa to 1,000 kPa (for example, about 100 kPa to 1,000 kPa) , preferably about 100 kPa to 500 kPa, and more preferably about 100 kPa to 300 kPa.
[00106] The high boiling point catalyst composition (metal catalyst component) can be separated from the low volatility phase (2B) by a single step or a plurality of steps. In addition, a portion of the volatile phase (2A) can have the heat removed and be condensed by using a condenser or a heat exchanger and then recycled to the reactor. [Distillation or extraction step (acetic acid collection step)]
[00107] The volatile phase (2A) is continuously fed to at least one extraction column (distillation column) and separated into a column top effluent (3A) containing methyl iodide and acetaldehyde by-product and an acid-containing stream (3B) acetic acid to collect acetic acid. Specifically, in the distillation column, the column top effluent (3A) containing at least methyl iodide and acetaldehyde (usually containing methyl iodide, methyl acetate, acetaldehyde, water and others) is separated with a volatile phase vapor (2A) powered from the flasher; and the liquid stream (side cut chain, side chain) (3B) containing acetic acid is removed by the side cut. Incidentally, the distillation column can separate a bottom liquid stream (highest boiling point component) (3C) containing at least water and methanol (usually, acetic acid, water, methanol, propionic acid, a metal catalyst component metal halide, and others). The bottom liquid stream (3C) can be removed (discharged) from the bottom of the distillation column. Since the bottom liquid stream (3C) contains a useful component such as the metal catalyst or acetic acid component remaining unevaporated, and the stream (3C) can be recycled to the reactor (or reaction step), the step flash evaporation (or distillation column), or others, as shown in the figure. In addition, as described below, the bottom liquid stream (3C) can be recycled to the reaction system or others via a storage vessel having a buffer function.
[00108] In the separating column (distillation column), the position of a feed port to feed the volatile phase (2A) is not particularly limited to a specific location. For example, the position of the feed port can be at an upper part, an intermediate part, or a lower part of the distillation column. In addition, in the distillation column, the volatile phase (2A) can be fed to an upper or lower position in relation to a side chain port for lateral cutting of the acetic acid chain. In addition, the position of the side chain port for lateral cutting of the acetic acid stream can be in an upper part, an intermediate part, or a lower part of the distillation column, and is usually preferably in an intermediate part or a lower part ( or from an intermediate to a lower part) of the distillation column.
[00109] As the separating column (distillation column), a conventional distillation column can be used, for example, a plate column, a filled column, and the flash distillation column. The distillation column such as a plate column or a filled column can usually be used. Incidentally, the material of (or to form the) distillation column is not limited to a specific material, and a glass material, a metal material, or a ceramic material, or the like, can be used. Usually, a distillation column made of metal is used in practice.
[00110] The distillation temperature and pressure in the separator column can be appropriately selected depending on the condition such as the type of the distillation column, or the selected (target) removal of the lowest boiling point component and the boiling point component higher. For example, the internal temperature of the distillation column (usually the temperature at the top of the column) can be controlled by adjusting the internal pressure of the column, and can be, for example, about 20 ° C to 180 ° C, preferably about from 50 ° C to 150 ° C, and more preferably about 100 ° C to 140 ° C.
[00111] Furthermore, for the column of plates, the theoretical number of plates is not particularly limited to a specific number, and depending on the species of the component to be separated, it is about 5 to 50, preferably about 7 to 35 , and more preferably about 8 to 30. Additionally, for the purpose of separating acetaldehyde highly (or with a high precision) in the distillation column, the theoretical number of plates can be about 10 to 80, preferably about 20 to 60 , and more preferably about 25 to 50. Additionally, in the distillation operation, the reflux ratio for the distillation column can be selected from, for example, about 0.5 to 3,000, and preferably about 0.8 to 2,000 depending on the number of theoretical dishes, or can be reduced by increasing the number of theoretical dishes.
[00112] The column top effluent (3A) contains, in addition to methyl iodide and acetaldehyde, methyl acetate, water, methanol, acetic acid, an aldehyde or a carbonyl impurity (such as crotonaldehyde or butylaldehyde), an iodide of C2-12 alkyl, a C3-12 carboxylic acid, and others. The amount of column top effluent (3A) can be, for example, about 5% to 70% by volume, preferably about 10% to 65% by volume, and more preferably about 12% to 60% by volume (for example, about 15% to 50% by volume) in relation to the entire volatile phase (2A).
[00113] Before recycling the bottom liquid stream (3C) to the reactor (or reaction step) or the flash evaporation step (or distillation column), propionic acid can be removed, because of the deterioration of the quality of acetic acid as a final product. In addition, usually, the acetic acid stream (crude acetic acid solution) (3B) can be further distilled (dehydrated) in the subsequent distillation column and then introduced into an acetic acid purification column to separate a point component. higher boiling (for example, a C3-12 alkanecarboxylic acid) and a lower boiling point component of the dehydrated stream to produce the acetic acid product. [Condensation and separation step]
[00114] According to the present invention, the gas phase (or gas phase component) containing at least acetaldehyde, particularly at least methyl iodide and acetaldehyde, is cooled and condensed by a plurality of condensers to produce a condensate rich in acetaldehyde, and acetaldehyde is separated and removed from the condensate. Accordingly, the present invention allows effective removal of acetaldehyde even by a small size removal apparatus (for example, a distillation column or a water extraction unit), compared to the removal of acetaldehyde by condensation of the gas phase. once (single condensation).
[00115] The gas phase is practically a mixture containing acetic acid, methyl acetate, methyl iodide, methanol, water, and acetaldehyde, or a mixture containing, in addition to the above components, hydrogen iodide, dimethyl ether, the impurities mentioned above (for example, an aldehyde such as crotonaldehyde, an alkyl iodide such as hexyl iodide, and propionic acid). In addition, in the embodiment described above, the volatile phase (2A), the column top effluent (3A) and the exhaust gas (5A) as a gas phase component are cooled and condensed to produce an acetaldehyde-rich condensate, and the condensate is purified from acetaldehyde. The gas phase (or gas phase component) can be a gas phase generated from at least one step during the acetic acid production process, for example, the reaction step, the flash evaporation step, and at least one distillation step . As the gas phase, usually a gas phase generated from at least one step between the flash evaporation step and a distillation step, particularly at least one distillation step, is subjected to the condensation treatment in practical cases. More specifically, the order of the high acetaldehyde content of gaseous components is as follows: (a) the first column top effluent (3A) of the separating column> (b) the volatile phase (2A) of the flasher> (c) the second column top effluent from the distillation column and the exhaust gas. Thus, in order to effectively separate and remove acetaldehyde, the gas phase to be condensed is practically at least one lower boiling point component of the volatile phase (2A) formed in the flash evaporation step and the first top effluent from column (3A) formed in the first distillation column, particularly at least the first column-top effluent (3A).
[00116] According to the present invention, the gas phase is condensed by cooling in sequence by a plurality of condensers that are sequentially lower in cooling temperature to form condensates, each having a low temperature, and acetaldehyde is separated from one condensate (s) enriched in acetaldehyde. The plurality of capacitors is practically positioned at least in series. If necessary, each of the capacitors of the plurality of capacitors positioned in parallel can be connected to a capacitor (s) in a serial manner or serially in a downstream direction.
[00117] Additionally, in cooling by the condensers, a component having a boiling point higher than the condensate temperature is condensed and liquefied, in contrast to a component having a boiling point lower than the condensate temperature maintains a gaseous state. In this way, the cooling of the gas phase by a plurality of condensers with lowering of the temperature sequentially in the downstream direction forms condensates sequentially lower in temperature. Finally, a component to be separated and removed or to be recovered (acetaldehyde and / or methyl iodide) contained in the gas phase can be separated as a condensate or a gas component. More specifically, in the case in which the gas phase is cooled sequentially by two condensers positioned in series, the gas phase is condensed in the first condenser to form a first condensate containing a condensate and a higher condensed and liquefied boiling point component and a first non-condensed gaseous component containing a concentrated lower boiling point component (such as acetaldehyde), and the first gaseous component is additionally cooled in the second condenser to form a second condensate having a temperature lower than that of the first condensate and a higher concentration of acetaldehyde and a second non-condensed gas component containing a component having a lower boiling point.
[00118] In the embodiment shown in the drawings, each of the volatile phase (2A) and the column top effluent (3A) is condensed using two condensers sequentially. If necessary, in order to further separate acetaldehyde from the second non-condensed gaseous component, the second non-condensed gaseous component can be further condensed by the subsequent condenser or a plurality of condensers (for example, third and fourth condensers) to form an enriched condensate in acetaldehyde, and the condensate can be subjected to an acetaldehyde removal treatment by the distillation column 6. Furthermore, since a desired component can be produced in a liquid or a gaseous form depending on the cooling temperature, not just the component condensate (condensate) of the second condenser but also a condensate (condensate) component enriched in acetaldehyde formed in an appropriate condenser of the plurality of condensers (for example, the subsequent condenser or the plurality of condensers) by cooling and condensing a gaseous component collected and subjected to treatment removal of acetaldehyde by the distillation column 6. Acetaldehyde is usually condensed by the second and subsequent condensers (for example, the second, third, or fourth condenser) among the plurality of condensers. In particular, acetaldehyde is practically condensed and liquefied by adjusting the cooling temperature of at least one of the second and subsequent capacitors (for example, the last capacitor), particularly the last capacitor, among the plurality of capacitors, to a temperature of condensation (or a temperature lower than a boiling point) of acetaldehyde.
[00119] The number of capacitors is not particularly limited to a specific number. The gas phase is usually subjected to the condensation treatment for about 2 to 5 (preferably about 2 to 3) condensers positioned in a series direction. The temperature of the condensates by the plurality of condensers can be selected depending on the gas phase. The temperature of the condensate by the first condenser can be about a temperature no lower than an acetaldehyde boiling point, for example, no higher than 110 ° C (for example, about 20 ° C to 110 ° C), preferably no higher than 105 ° C (for example, about 30 ° C to 105 ° C), and most preferably about 35 ° C to 100 ° C (for example, about 35 ° C to 90 ° C) and can usually be about 30 ° C to 80 ° C (for example, about 30 ° C to 70 ° C). In addition, the temperature of the condensate (s) by the second and subsequent condensers (for example, the last condenser) in a series direction is not greater than an acetaldehyde condensation temperature, and a temperature may be lower than a boiling point of acetaldehyde. The temperature of the condensate (s) by the second and subsequent condensers (for example, the last condenser) can, for example, be no higher than 50 ° C (for example, about -15 ° C to 50 ° C ), preferably not higher than 45 ° C (for example, about -15 ° C to 45 ° C), more preferably not higher than 40 ° C (for example, about -10 ° C to 40 ° C) , and particularly about -10 ° C to 35 ° C (for example, about -5 ° C to 30 ° C) and can be about -10 ° C to 25 ° C (for example, about - 5 ° C to 20 ° C). The temperature of the condensate (s) by the second and subsequent condensers (for example, the last capacitor) can be about 0 ° C to 40 ° C (for example, about 0 ° C to 30 ° C).
[00120] For the purpose of condensing acetaldehyde while separating acetaldehyde from the other components, it is preferable that the gas phase is cooled by a condenser having a condensate temperature T1 of 0 ° C to 50 ° C and then the resulting gas phase is cooled by a condenser having a T2 condensate temperature of -15 ° C to 45 ° C to condense and liquefy acetaldehyde. In particular, to liquefy the acetaldehyde by condensation, a temperature difference F (T1-T2) is preferably 1 ° C to 60 ° C (for example, 5 ° C to 50 ° C). In order to condense methyl iodide while separating methyl iodide from the other components, it is preferable that the gas phase is cooled by a condenser having a T3 condensate temperature of -15 ° C to 50 ° C and then the resulting gas phase is cooled by a condenser having a T4 condensate temperature of -15 ° C to 45 ° C for the condensation of methyl iodide. A temperature difference F (T3-T4) is preferably about 1 ° C to 60 ° C (for example, about 5 ° C to 50 ° C).
[00121] The condenser may include a multitubular heat exchanger, a multitubular cylindrical heat exchanger, a heat exchanger using a thermosyphon, an air-cooled heat exchanger, a double tube heat exchanger, a coil, a cascade heat exchanger, a plate heat exchanger, and a spiral heat exchanger.
[00122] Additionally, when the condensate (s) (concentrate (s) of the second and subsequent condensers cause (s) separation of phases in two liquid layers, one of a higher phase (for example, an aqueous phase containing acetaldehyde) and a lower phase (for example, an organic phase containing methyl iodide) or at least a portion (portion or whole) of both the upper and lower phase can be subjected to an acetaldehyde removal treatment.
[00123] In the case in which the plurality of condensers is used, the non-condensed gaseous component (s) of the second and subsequent condensers (for example, the last condenser) can be fed as an exhaust gas to the absorption system.
[00124] Condensate formed by condensation or removal of heat from a portion of the volatile phase (2A) and / or column top effluent (3A) by the condenser does not necessarily need to be recycled to reactor 1. In addition, at least a portion (portion or totality) of acetaldehyde concentrates (condensates) formed by the plurality of condensers can optionally be mixed together, and the concentrates (mixed) can be purified from acetaldehyde (including removal of acetaldehyde or distillation, water extraction, or others), and the residual liquid (or separate liquid) from which the acetaldehyde was removed can be recycled to a step from the reaction step to the acetaldehyde separation step. For example, acetaldehyde can be separated not only from the condensed component formed by the first capacitor, but also from the condensed component formed by the subsequent capacitor or by the plurality of capacitors (for example, the second capacitor). For example, the residual liquid (for example, a liquid rich in methyl iodide) from which acetaldehyde was separated can be, for example, recycled to reactor 1, flasher, separator column 3, distillation column 6, and others. Additionally, for example, when the volatile phase (2A) is not condensed by cooling, the entire amount of the volatile phase (2A) can be fed to the separating column (distillation column) 3. [Decanter and buffer tank] Liquid separation unit
[00125] The decanter and the buffer tank (or storage tank) are not necessarily necessary. In order to additionally concentrate acetaldehyde and methyl iodide by liquid-liquid separation, the apparatus according to the present invention is practically equipped with at least one unit selected from the decanter and the buffer tank (or storage tank) . The use of the buffer tank inhibits flow fluctuation as described above and provides stable acetic acid production. In addition, when the condensate forms two layers in a buffer tank, the buffer tank acts as a decanter. In this way, both of the decanter and the buffer tank can be composed of a single decanter or buffer tank. Hereinafter, the decanter and the buffer tank will be described simply as a liquid separation unit unless otherwise specified, and the treatment of the condensate (condensate component) will be explained.
[00126] It is sufficient that the liquid separation unit stores a condensate of at least one gas phase selected from the group consisting of the volatile phase (2A) of the flash evaporation step and the column top effluent (3A, 4A , ...) of a distillation step or a plurality of distillation steps. A condensate of at least one gas phase selected from the group consisting of the volatile phase (2A) and the first column top effluent (3A), in particular a condensate of at least the first column top effluent (3A) , is practically stored in the liquid separation unit. In addition, among the condensates of the gas phases (for example, at least the first column top effluent (3A)), the condensate of the preceding condenser (for example, at least the first condenser) and the condensate (concentrate) of at least one of the second and subsequent capacitors (for example, the last capacitor) can be practically stored separately (individually) in the liquid separation units. For example, the gas phase can be condensed by the plurality of condensers, the concentrate (condensate enriched in acetaldehyde) formed by at least one of the second and subsequent condensers (for example, the last condenser) can be stored in a storage tank, and acetaldehyde can be separated from the stored liquid. In addition, the condensate from the preceding condenser (for example, at least the first condenser) can be stored in a decanter, and as described above, this condensate and the concentrate mentioned above can be mixed and distilled.
[00127] The condensate from the column top effluent (3A), which is rich in acetaldehyde, is fed at least to the distillation column 6 from the liquid separation unit (the decanter 4, the buffer tank 5) without pass through complicated lines, and the acetaldehyde is separated and removed from the condensate.
[00128] In the case where the condensate (condensed component) causes phase separation in two layers of liquid in the liquid separation unit (the decanter 4, the buffer tank 5), the phase separation further enriches acetaldehyde in the phase upper (aqueous phase) and methyl iodide in the lower phase (organic phase). Acetaldehyde and methyl iodide are also distributed to both the upper phase (aqueous phase) and the lower phase (organic phase).
[00129] For the purpose of separating and removing acetaldehyde, the upper phase and / or the lower phase, particularly the upper phase, can be distilled by at least the distillation column 6. In addition, the upper phase and / or the phase The lower phase, particularly the lower phase, can be recycled to at least reactor 1. Additionally, the upper phase and / or the lower phase, particularly the upper phase (aqueous phase), can be distilled by the separator column 3 and then condensed by the plurality of condensers to condense and separate acetaldehyde.
[00130] Condensates (for example, condensate from the first column top effluent (3A)) except condensate (higher concentrate) rich in acetaldehyde and / or methyl iodide can be fed to the liquid separation unit for separation phases, and do not necessarily need to be fed to the liquid separation unit. For example, in the above embodiment, the condensate in the first condenser (for example, the first condensate from the first column top effluent (3A)) does not necessarily need to be fed to the liquid separation unit. Decanter
[00131] In the embodiment shown in Fig. 1, the condensate (condensed component) is fed to a predetermined line or unit of the decanter 4 through the lower phase line 41 and the upper phase line 44. A portion of the condensate (condensed component ) can be recycled through just the line (a single line) 41 or 44 to control the flow of condensate to be fed to line 43a connected to buffer tank 5. Furthermore, without referring to the separate liquid phases (the upper layer , the bottom layer), the condensate can be fed or discharged on a predetermined line of the unit via a single line.
[00132] The condensate in the decanter usually forms two layers. In this case, the condensate from any of the upper layer (upper phase) and / or the lower layer (lower phase) can be fed to the reactor, the separating column, the distillation column, or others.
[00133] Either the top layer (a portion or all of the top layer) or the bottom layer (a portion or all of the bottom layer) can be recycled to the reaction system, or both layers can be recycled to the reaction system . The condensate to be recycled to the reaction system or others can be recycled, if necessary, after separation of acetaldehyde in a conventional manner (for example, extraction as described below).
[00134] Furthermore, in the case in which the condensate forms the upper layer (upper phase) and the lower layer (lower phase), the fluctuation of the liquid level (or the amount maintained) can be completely eliminated, or the fluctuation of the liquid phase levels (or each of the amounts maintained) of both layers can be eliminated. For example, as shown in Fig. 1, the fluctuation of the liquid level of both the upper layer and the lower layer can be eliminated by regulating the discharge flows of the upper layer and the lower layer, depending on the fluctuation of the flow of the condensate fed. to the decanter. Buffer tank (storage tank)
[00135] The buffer tank is not necessarily necessary. If necessary, via decanter 4, the volatile phase condensate (s) (2A) and / or the column top effluent (3A), that is, the rich condensate (s) in acetaldehyde it can be supplied to the distillation column 6 to separate the acetaldehyde. In addition, the condensate in the buffer tank 5 can be subjected to the distillation column 6 or the separating column 3, and if necessary, it can be recycled to reactor 1. The condensate (stored liquid) stored in the buffer tank 5 is rich in acetaldehyde and methyl iodide condensed by at least one of the second and subsequent condensers among the plurality of condensers. In the case where the condensate (stored liquid) causes phase separation in two layers of liquid, the phase separation additionally enriches acetaldehyde in the upper phase (aqueous phase) and methyl iodide in the lower phase (organic phase or heavy phase). Thus, for example, in the case where the condensate causes phase separation in two layers of liquid in the buffer tank 5, the upper phase (aqueous phase) can be fed to the distillation column 6 and / or to the reactor 1 with or without recycling to the separating column 3, and the lower phase (organic phase) can be fed to the separating column 3 and / or to the reactor 1 with or without feeding to the distillation column 6.
[00136] The lower phase or the organic phase of the condensate in the buffer tank 5 can be fed to the distillation column 6 (aldehyde removal column) via the supply line (lines 51, 52, 53). The upper phase or the aqueous phase in the buffer tank 5 can be recycled to the separating column 3 via the recycling line (line 54, line 57 and recycling line 46). In addition, the upper phase or the aqueous phase in the buffer tank 5 can be fed to the distillation column 6 via the feed line (line 54, lines 56 and 53). The distillation of the upper phase (aqueous phase) by the distillation column 6 allows effective separation and removal of acetaldehyde as a second column top effluent. In addition, the distillation of the lower phase (organic phase or heavy phase) by the distillation column 6 allows effective recovery of methyl iodide as a bottom stream.
[00137] Additionally, since the condensate in the buffer tank 5 contains acetaldehyde in the highest concentration, the acetaldehyde can be separated from the condensate (small amount of liquid stored) by a small size device, which is industrially advantageous. Although acetaldehyde is separated from the condensate (stored liquid) in buffer tank 5, the absolute amount of acetaldehyde to be removed is sometimes less than the absolute amount of byproduct acetaldehyde. Thus, for the purpose of separating the acetaldehyde, it is advantageous to combine the condensate (stored liquid) in the buffer tank 5 and a portion of the condensate stored in the decanter 4 and to separate the acetaldehyde from the combined mixture. According to this way for acetaldehyde separation, a liquid (condensate) having a higher concentration of acetaldehyde compared to a conventional process can be treated to increase the amount of acetaldehyde removal even by using conventional equipment. For example, in the case where the condensate (stored liquid) in the buffer tank 5 is distilled by the distillation column 6, if the amount of condensate fed to the distillation column 6 (lines 51, 54, 53) is the same , the condensate will have a higher concentration of acetaldehyde compared to the conventional way, so that the acetaldehyde can be removed in a greater amount.
[00138] When the liquid stored in the decanter and the liquid stored in the storage tank are combined (or joined) and acetaldehyde is separated from them (for example, when the combined liquid is distilled through the second distillation column), the ratio between the weight of the liquid in the decanter and the weight of the liquid in the storage tank can be selected from the range of about 0/100 to 95/5 as the liquid in the decanter / the liquid in the storage tank and can be about 0/100 to 75/25 (for example, about 3/97 to 90/10), preferably about 0/100 to 85/15 (for example, about 5/95 to 80/20), more preferably about 0/100 to 75/25 (e.g., about 7/93 to 70/30) or it can be about 5/95 to 50/50 or about 5/95 to 30/70.
[00139] In the case in which the condensate stored in the decanter 4 and / or the storage tank 5 causes phase separation in two layers of liquid, it is sufficient to separate the acetaldehyde from at least one selected phase from an upper phase (aqueous phase) and a lower phase (organic phase). In a preferred embodiment, acetaldehyde is separated from an upper phase (aqueous phase) having a high concentration of acetaldehyde with predominant distribution. For example, in order to increase the acetaldehyde removal efficiency, an upper phase having a high acetaldehyde concentration of the condensate of the first condenser C3 and an upper phase having a high acetaldehyde concentration of the condensate of the second condenser C4 can be combined ( or joined) and distilled by the distillation column 6.
[00140] It is useful to separate acetaldehyde from the second condensate from the first column top effluent (3A). With respect to a condensate, the second condensate (via lines 27, 29) of the volatile phase (2A), the second condensate (via lines 36, 37, 38) of the first column-top effluent (3A), and the condensate ( via line 112) of the expelled gas absorption system (exhaust gases A to E) are different from each other in acetaldehyde concentration. Each of the second condensate from the first column top effluent (3A) and the condensate from the expelled gas absorption system (exhaust gases A to E) has a relatively high acetaldehyde concentration. From this, acetaldehyde can be separated in a high concentration by storing the entire amount of the second condensate from the volatile phase (2A) in the decanter 4 via feed lines (lines 27, 28), storage or retention of the second condensate from the first top effluent column (3A) and condensate from the expelled gas absorption system (exhaust gases A to E) in buffer tank 5 via feed line 38, and treatment (acetaldehyde removal treatment) of these condensates (stored liquids) , preferably at least the condensate in the buffer tank 5. [Step to remove acetaldehyde and recycle the useful component]
[00141] In the step (separation and recycling step) to remove acetaldehyde and recycle a useful component, the acetaldehyde is separated from the condensate and the residual liquid from which the acetaldehyde was removed is recycled to a reaction system step to the acetaldehyde separation.
[00142] The condensate practically contains acetaldehyde, methyl iodide, acetic acid, methyl acetate, water, methanol, an aldehyde (such as crotonaldehyde or butylaldehyde), C2-12 alkyl iodide, C3-1212 carboxylic acid, and others. In the condensate, the acetaldehyde content can be about 0.05% to 50% by weight, the methyl iodide content can be about 0.5% to 90% by weight, the methyl acetate content can be about from 0% to 15% by weight, the acetic acid content can be about 0% to 80% by weight, and the water content can be about 0.1% to 40% by weight.
[00143] The method for separating acetaldehyde is not particularly limited to a specific method and can use a conventional method such as extraction, distillation (distillation of a process liquid containing acetaldehyde by a distillation column or a plurality of distillation columns), a combination thereof, or extractive distillation. Representatively, at least a portion (portion or totality) of the condensate (the volatile phase condensates (2A), the column top effluent (3A), and / or the exhaust gas (the exhaust gases from the reactor, from the column distillation and condenser)) is fed to the distillation column (acetaldehyde separation column) to form the second column top effluent (4A) containing acetaldehyde and the residual liquid (bottom stream, bottom fraction or bottom fraction column) from which acetaldehyde was removed. As the acetaldehyde separation column, for example, a conventional distillation column can be used, for example, a plate column, a filled column, and a flash distillation column. The distillation column such as a plate column or a filled column can usually be used.
[00144] In the above modality, the condensate is subjected to a treatment of removal (distillation) of acetaldehyde by a single distillation column. The condensate can be subjected to a plurality of acetaldehyde removal treatments, for example, it can be distilled by a plurality of distillation columns. For the removal of acetaldehyde through a distillation column, the feed liquid (the condensate to be treated) can be fed as is, or it can be fed after the feed liquid is degassed to remove gas (such as N2, CO, CO2) . In this case, the gas can be separated after the feed liquid is heated and evaporated in a separation vessel, or the gas can be removed by heating the separation vessel. Since overheating removes acetaldehyde together with the gas, thus decreasing the concentration of acetaldehyde in the feed liquid, it is useful to adjust the heating temperature.
[00145] The temperature (the top column temperature) and the pressure (the top column pressure) in the acetaldehyde separation column can be selected depending on the concentrations of acetaldehyde and methyl iodide and also the species of the distillation column and other factors provided that at least acetaldehyde can be separated by using a difference between the boiling points of acetaldehyde and other components (particularly methyl iodide). For example, for a column of plates, the pressure at the top of the column is about 10 kPa to 1,000 kPa, preferably about 10 kPa to 700 kPa, and more preferably about 100 kPa to 500 kPa in terms of absolute pressure. The internal temperature of the column (the temperature of the top of the column) can be, for example, about 10 ° C to 80 ° C, preferably about 20 ° C to 70 ° C, and more preferably about 40 ° C to 60 ° C. The theoretical number of dishes can be, for example, about 5 to 80, preferably about 8 to 60, and more preferably about 10 to 50.
[00146] If necessary, water is fed to the distillation column (acetaldehyde separation column) to increase the pressure and / or the distillation temperature in the column in order to inhibit the formation of paraldehyde and metaldehyde. Alternatively, a condensed aldehyde (for example, paraldehyde and metaldehyde) can be positively generated by changing the distillation conditions, and acetaldehyde can be separated and removed as a condensed aldehyde from the distillation column. In this case, blocking or clogging of the tubes due to the crystallization of the condensed aldehyde can be inhibited by feeding a solvent (for example, methanol) that dissolves the condensed aldehyde into the column.
[00147] Condensate distillation usually separates the residual liquid (highest boiling point component (4B)) containing a useful component, methyl iodide, as a bottom stream. The residual liquid can be recycled to a reaction system step to the acetaldehyde separation step, for example, any of the reaction step (or reactor), the flash distillation step (or flash distillation column), the step of collecting acetic acid (or extracting column), and other steps. The residual liquid is practically recycled to at least the reactor.
[00148] In the above modality, the residual liquid can be recycled to the acetaldehyde separation column. In the acetaldehyde separation column, the reflux ratio can be selected from about 1 to 1,000, preferably about 10 to 800, more preferably about 50 to 600 (for example, about 100 to 600) depending on the number of dishes theoretical. [Buffer tank]
[00149] The residual liquid (bottom stream or highest boiling point component (4B)) from the distillation column (acetaldehyde removal column) can be recycled directly to the reaction system other than through the buffer tank 7 or it can be recycled to the reaction system through a storage container (such as a buffer tank) having a buffer function. The use of the storage container having a buffer function eliminates flow fluctuation in the storage container and allows easy recycling of the residual liquid at a constant or substantially constant flow, even if the flow of the residual liquid fluctuates. In this way, the storage container can reduce the adverse influence of flow fluctuation on the recycling step.
[00150] Also in the storage container having a buffer function, as is the case with the condensation step, the flow can be controlled based on the degree of flow fluctuation or based on the retention time of the residual liquid. In the storage container, the retention time of the residual liquid can be, for example, not less than 1 minute (for example, about 2 minutes to 3 hours), preferably not less than 3 minutes (for example, about 4 to 60 minutes), and more preferably not less than 12 minutes (for example, about 15 to 40 minutes). [Extraction step]
[00151] The second column top effluent (4A) can be discharged as is. Since the second column top effluent (4A) sometimes contains a useful component such as methyl iodide, methyl iodide (or a component containing methyl iodide, for example, a component containing methyl iodide, methyl acetate, and others) can be recovered from the second column top effluent (4A) for recycling.
[00152] The method for separating each of acetaldehyde and methyl iodide (or a component containing methyl iodide) from the second column top effluent (4A) may include a conventional method (for example, extraction, distillation). Representative examples of the method may include (i) a method for separating each of methyl iodide and acetaldehyde by distilling the second column top effluent (4A), (ii) a water extraction method to separate each of the iodide from methyl and acetaldehyde by subjecting the second column top effluent (4A) to water extraction, based on the miscibility of acetaldehyde with water and the immiscibility of methyl iodide. From the point of view of inhibiting the formation of a condensed aldehyde such as metaldehyde, the water extraction method (ii) is preferred. According to the water extraction method, since the concentration of protons in the distillation solution is increased due to the decomposition of ester or others and inhibits the formation of a condensed aldehyde (eg, paraldehyde and metaldehyde), acetaldehyde can be effectively high and removed from the process stream.
[00153] The second column top effluent (4A) subjected to water extraction forms (or is separated into) an aqueous phase (light phase or upper phase) containing acetaldehyde and an organic phase (heavy phase, methyl iodide phase or refined) containing methyl iodide. Water extraction can be performed by a single extractor or a plurality of extractors. It may be possible to operate the process so that the gaseous phase (s) is cooled or chilled (s) with the plurality of capacitors, the total amount of the second and subsequent condensates (liquid cooled) (or either the top layer or the bottom layer in the case where condensates cause phase separation into two liquid layers) can be fed to the distillation column (aldehyde removal column), and a distillate from the distillation can be subjected to extraction with water.
[00154] Regarding water extraction, the extraction temperature is not particularly limited to a specific extraction temperature and the extraction time is not particularly limited to a specific extraction time. For example, extraction can be carried out at a temperature of 0 ° C to 100 ° C for about 1 second to 1 hour. The extraction pressure is not particularly limited to a specific extraction pressure, and an advantageous condition can be selected from costs, and other factors. As the extractor, for example, a combination of a mixer with a settler, a combination of a static mixer with a decanter, a RDC (rotated disk contactor), a Karr column, a spray column can be used , a stuffed column, a column of perforated plates, a compartmentalized column, a pulsed column, and others. The extractor (extraction column) can be a single stage extraction unit to extract an object from a mixture of the object and water and separate the mixture into liquid phases, or it can be a plurality of single stage extraction units positioned in a cascading way. For example, the extractor may be a multistage extraction unit that comprises a plurality of extractors (each extractor having a theoretical number of plates of 1) for sequential extraction. In addition, the extractor can be a multistage extraction unit in which a plurality of extractors have been installed in a single unit, for example, a single extraction unit having the theoretical number of plates equivalent to that of a multistage extraction unit ( the theoretical number of dishes corresponding to the multistage extraction). In addition, the extraction may be either a batch or a continuous system, or it may be either a concurrent extraction or a countercurrent extraction.
[00155] The organic phase can be discharged from the system. The organic phase can be recycled to any stage of the reaction system for the acetaldehyde separation stage, for example, the reaction stage (or reactor), the flash distillation stage (or flash distillation column), the collection stage of acetic acid (or distillation column), or other steps. As shown in the drawings, the organic phase can be recycled to the acetaldehyde separation column (recycled as the highest boiling point component (4B)) or it can be recycled to a plurality of steps. The organic phase (heavy or refined phase) is recycled to at least the reactor.
[00156] The aqueous phase (light phase or upper phase) can be additionally fed to the aldehyde removal column via line 84 and separated into a fraction of aldehyde and water. The water can be used for the extraction of acetaldehyde in the water extraction column 8, or if necessary, the water can be returned to the reactor 1.
[00157] In addition, if necessary, the gaseous phase (s) can be cooled by a plurality of capacitors in a multistage manner, and the acetaldehyde concentrate (or condensate) / methyl iodide can be subjected to extraction with water. [Treatment of expelled gas]
[00158] The expelled gas (exhaust gas) produced from the acetic acid production process contains at least methyl iodide and acetaldehyde. Thus, according to the present invention, at least methyl iodide and acetaldehyde can be concentrated or recovered from the expelled gas (exhaust gas) and then can be separated or used effectively. For example, acetic acid can be produced by placing an expelled gas (exhaust gas) produced by at least one step selected from the group consisting of the reaction step, the flash evaporation step, at least one distillation step, and at least one step of retention (storage) in contact with an absorption solvent; extracting the solvent to form a gas phase (5A) containing at least methyl iodide and acetaldehyde; and separation and removal of acetaldehyde from the gas phase. As the absorption solvent, at least one member selected from the group consisting of methanol and acetic acid can be used. Even if the expelled gas (exhaust gas) has a low concentration of a volatile component (for example, predominantly methyl iodide, acetaldehyde, methyl acetate, water, and acetic acid, in particular, acetaldehyde and methyl iodide), a such a process can concentrate the volatile component to a high concentration by extraction. In addition, recycling (recycling of the organic phase containing methyl iodide to the reaction system) allows the effective use of a useful component.
[00159] According to Fig. 2, an absorption treatment in the high pressure absorption column 101 can be carried out by placing the expelled gas in contact with an absorption solvent (methanol and / or acetic acid) at a high pressure ( for example, 0.7 MPa to 4 MPa, preferably 1 MPa to 3.5 MPa); an absorption treatment on the low pressure absorption column 102 can also be carried out by placing the expelled gas in contact with an absorption solvent at 0 MPa to 0.2 MPa (for example, 0.05 MPa to 0.15 MPa). For example, the temperature of the absorption solvent can be about 0 ° C to 40 ° C, the methanol temperature can be about 0 ° C to 40 ° C (for example, about 10 ° C to 30 ° C) , and the temperature of acetic acid can be about 17 ° C to 40 ° C (e.g., about 18 ° C to 30 ° C). The extraction in the diffusion column (extraction column) 103 can be carried out at a pressure (for example, about 0 MPa to 0.2 MPa), a column top temperature (for example, about 50 ° C to 120 ° C), and a column bottom temperature (e.g., about 90 ° C to 170 ° C). For example, extraction of the gas expelled with methanol can be conducted at a column top temperature of about 40 ° C to 70 ° C and a column bottom temperature of 90 ° C to 110 ° C; extraction of the gas expelled with acetic acid can be conducted at a column top temperature of about 100 ° C to 115 ° C and a column bottom temperature of about 130 ° C to 155 ° C. When methanol is used as the absorption solvent, condensate from the C6 condenser can be refluxed into the diffusion column (extraction column) 103. Although concentration by a condenser in the expelled gas treatment is not essential, the expelled gas as the gas phase (5A) can be concentrated by a condenser if necessary, as described above.
[00160] The treatment of the expelled gas (exhaust gas) is not essential, and, for example, an exhaust gas from the reactor, the condenser, the distillation column, or others can be discharged. In addition, the exhaust gas A of reactor 1 can be additionally cooled or cooled by a heat exchanger to form a liquid component (containing acetic acid, methyl acetate, methyl iodide, acetaldehyde, water and others) and a gaseous component (containing carbon monoxide, hydrogen and others), and the liquid component can be recycled to reactor 1 and the gaseous component (waste gas) can be discharged. In addition, unlike the process shown in Fig. 1, it may be useful to treat an expelled gas (exhaust gas) produced from at least one step selected from the group consisting of the reaction step, the flash evaporation step, and at least least one distillation step. For example, the gas expelled (exhaust gas) from the reaction step and that from the flash evaporation step can be treated, the gas expelled (exhaust gas) from the flash evaporation step and that from the distillation step can be treated, or the gas expelled (exhaust gas) from the plurality of distillation steps can be treated.
[00161] In the treatment of exhaust gas, a non-condensed gaseous component that has not been liquefied by a condenser can be further separated into a condensed component and a gaseous component by a subsequent condenser or a plurality of condensers (for example, second, third , and four capacitors). The resulting liquid enriched in acetaldehyde can be treated by the acetaldehyde removal column (acetaldehyde removal step). In such a treatment, a gaseous component among at least one of the second and subsequent condensers (for example, the last condenser) can be fed as an exhaust gas to the absorption system. EXAMPLES
[00162] The following examples are intended to describe this invention in more detail and should not be construed in any way as defining the scope of the invention. (Comparative Example 1)
[00163] According to Comparative Example 1, the column top effluent (3A) of the separating column 3 was condensed by the first condenser without the second condenser, and the resulting condensate was fed to the decanter 4. That is, in the apparatus ( or process) shown in Fig. 1, the first condensate (temperature: 38 ° C) of the column top effluent (3A) from the separating column 3 was fed to the decanter 4 to form an upper layer and a lower layer, and 75% in volume of the lower layer formed in the decanter, it was fed to the distillation column 6 (in line 53) through the storage tank 5 (in line 43a). The amount fed to the distillation column 6 corresponded to 37% by volume of the first whole condensate of the column top effluent (3A) fed to the decanter 4. In addition, a portion of the upper layer (upper phase) was refluxed into the separating column 3 via line 46 without being fed to line 43a or line 43, and another portion thereof was recycled to reactor 1 via line 45b.
[00164] That is, 37% by volume of the first entire condensate of the column top effluent (3A) fed to the decanter 4 was supplied to the distillation column 6 via line 43a, and 63% by volume of the first entire condensate was recycled. for separator column 3 and reactor 1. The following were the details of the recycle: 3% by volume of the first entire condensate of the column top effluent (3A) fed to the decanter 4 [100% by volume of the upper layer, 0% by volume of the bottom layer] and 11% by volume of the first whole condensate (the bottom layer) was recycled to reactor 1, and 47% by volume of the first whole condensate was fed to the separator column 3 (incidentally, the rest was a component gas that had not been liquefied).
[00165] The composition of the first condensate (in line 43a) fed to storage tank 5 was as follows: 86.8% by weight methyl iodide, 11% by weight methyl acetate, 0.9% by weight acetic acid, 1.0 wt% water, 0.163 wt% acetaldehyde, and 0.001 wt% hydrogen iodide. Then, the gas expelled from storage tank 5 was recycled to line 34 via line 59 and introduced into the absorption system, in which acetaldehyde was collected, other than through the second condenser, and then fed to decanter 4 via line 112. The amount of liquid (lines 51, 52) flowing out of storage tank 5, that is, the amount of the first condensate from the column top effluent (3A) fed to the distillation column 6 was 96% of the total amount (the first condensate (in line 43a)) fed to storage tank 5, and its composition was as follows: 86.8% by weight methyl iodide, 11% by weight methyl acetate, 0.8% by acid weight acetic, 0.9% by weight water, 0.138% by weight acetaldehyde, and 0.001% by weight hydrogen iodide.
[00166] In addition, the volatile phase (lowest boiling point component) (2A) of the flash evaporation step (evaporator) was supplied to the two condensers (C1, C2), fed to tank 9, and recycled to the reactor 1 without being fed to the decanter 4.
[00167] The second column-top effluent (4A) taken from the 80-plate distillation column 6 was subjected to extraction with water in extractor 8 to form refined methyl-containing iodide from which acetaldehyde had been extracted with water. A portion of the refine was recycled as such for the 10th dish from the bottom of the distillation column 6, and another portion of the refine was recycled as such for reactor 1. The flow of the recycled refine to the distillation column 6 was maintained constant. The acetaldehyde extraction rate from the second column top effluent (4A) was 98%. Acetaldehyde (20 kg / h) was removed by extracting the entire liquid (51 kg / h) removed from the top of the 80-plate distillation column. By such a process, acetaldehyde was produced in the reactor, and 47% of the produced acetaldehyde (43 kg / h) was obtained removed.
[00168] After the above process has been operated continuously for a predetermined time (210 hours), the determined acetaldehyde concentration in the reactor was 300 ppm. The resulting acetic acid product had a permanganate time of 290 minutes. In addition, acetic acid had a propionic acid concentration of 81 ppm. (Example 1)
[00169] According to the apparatus (or process) shown in Fig. 1, the process to produce acetic acid was conducted continuously. Specifically, the first column-top effluent (3A) was cooled by the first condenser C3 to a controlled cooling fluid temperature to form a first condensate having a temperature of 38 ° C (and a first gas component having a temperature of approximately 38 ° C). ° C). The first gaseous component was cooled by the second condenser C4 to a controlled cooling fluid temperature, and a second entire condensate of the second condenser C4 was fed to the storage tank (which functioned as a decanter when the condensate forms separate liquid phases) 5 via lines 36 and 38, where line 36 had a temperature of 12 ° C, the flow in line 39 was zero “2” Cnfio fkuuq. q rtkogktq eqpfgpucfq was fed to the decanter 4 to form an upper layer and a lower layer. The lower layer (lower phase) was fed to the storage tank 5 via lines 41, 43 and 65c * go swg c xcz «q pc nknjc 65d hqk zgtq“ 2 ”+ the Godqtc q ugiwpfq condensed from the second condenser C4 and the layer bottom of the decanter 4 were kept in the storage tank 5, a mixture of these liquids did not form separate liquid phases. The mixture in storage tank 5 was fed to the distillation column 6 via lines 51, 52, 53. The conditions were the same as in Comparative Example 1 except that line 38 was joined not to decanter 4, but to storage tank 5 , that the quantity fed to the distillation column 6 via line 53 was the same as in Comparative Example 1 by adjusting the flow of line 43a and that of line 38, and that of line 28 was added not to tank 9, but to decanter 4 .
[00170] That is, the first condensate and the second condensate of the column top effluent (3A) of the separating column 3 were combined to form a mixture of these condensates, and 37% by volume of the entire condensate mixture (the condensate from the line 33 and line 36) was fed to line 53 (or to the distillation column 6). In addition, 13% by volume of the entire condensate mixture (condensate from line 33 and line 36) [3% by volume of the upper layer, 10% by volume of the lower layer] was recycled to reactor 1, and 47% in volume of the entire condensate, it was fed to the separating column 3 (incidentally, the remainder was a gaseous component that had not been liquefied).
[00171] The composition of the first condensate (in line 43a) fed to storage tank 5 was as follows: 86.8% by weight methyl iodide, 11% by weight methyl acetate, 0.9% by weight acetic acid, 1.0 wt% water, 0.163 wt% acetaldehyde, and 0.001 wt% hydrogen iodide. The composition of the second condensate (in line 38) was as follows: 86.1% by weight methyl iodide, 10.8% by weight methyl acetate, 0.1% by weight acetic acid, 2.4% by weight water , 0.338% by weight acetaldehyde, and 0.001% by weight hydrogen iodide. The feed ratio of the first condensate to the second condensate was 91.4% by weight relative to 8.6% by weight. Then, the gas expelled from the storage tank 5 was recycled to line 35 via line 59. The quantity (in line 51) of the mixture of the first condensate and the second condensate taken from the storage tank 5, that is, the quantity ( in line 53) of the mixture fed to the distillation column 6, was 87% of the total amount (a total amount of the first condensate (in line 43a) and the second condensate (in line 38)) fed to storage tank 5. In addition Furthermore, the composition of the mixture fed to the distillation column 6 was as follows: 86.9% by weight methyl iodide, 11.1% by weight methyl acetate, 0.9% by weight acetic acid, 0.8% by weight water weight, 0.151 wt% acetaldehyde, and 0.001 wt% hydrogen iodide.
[00172] In addition, the second column top effluent (4A) from the top of the column was subjected to extraction with water in the extractor 8 to form a refine containing methyl iodide from which acetaldehyde had been removed. A portion of the refine was recycled as such for the 10th bottom plate of the distillation column 6, and the other portion of the refine was recycled as such for reactor 1. The flow rate of the recycled refine to the distillation column 6 was kept constant . The acetaldehyde extraction rate of the lowest boiling point component (4A) was 98%. Acetaldehyde (22 kg / h) was removed by extraction treatment of the entire liquid (51 kg / h) removed from the top of the 80-plate distillation column. By such a process, acetaldehyde was produced in the reactor, and 51% of the removed acetaldehyde (43 kg / h) was removed.
[00173] The above process could be operated continuously and steadily. After the process was continuously operated for a predetermined time (210 hours), the concentration of acetaldehyde determined in the reactor was 250 ppm, which revealed that the process could be operated stably while removing acetaldehyde at a high level. The resulting acetic acid product had a permanganate time of 330 minutes. In addition, acetic acid had a propionic acid concentration of 71 ppm. (Example 2)
[00174] The experiment was carried out in the same manner as in Example 1 except that the temperature of the first condensate was 50 ° C.
[00175] The composition of the first condensate (in line 43a) fed to storage tank 5 was as follows: 86.9% by weight methyl iodide, 10.9% by weight methyl acetate, 0.9% by acid weight acetic, 1.0% by weight water, 0.169% by weight acetaldehyde, and 0.001% by weight hydrogen iodide. The composition of the second condensate (in line 38) was as follows: 85.7% by weight methyl iodide, 11.6% by weight methyl acetate, 0.2% by weight acetic acid, 2.0% by weight water , 0.354% by weight acetaldehyde, and 0.001% by weight hydrogen iodide. The feed ratio of the first condensate to the second condensate was 84.2% by weight relative to 15.8% by weight. Then, the gas expelled from the storage tank 5 was recycled to line 35 via line 59. The quantity (in line 51) of the mixture of the first condensate and the second condensate taken from the storage tank 5, that is, the quantity ( in line 53) of the mixture fed to the distillation column 6, was 80% of the total amount (a total amount of the first condensate (line 43a) and the second condensate (line 38)) fed to storage tank 5. In addition, the composition of the mixture fed to the distillation column 6 was as follows: 86.9% by weight methyl iodide, 11.0% by weight methyl acetate, 1.0% by weight acetic acid, 0.9% by weight water , 0.156% by weight acetaldehyde, and 0.001% by weight hydrogen iodide.
[00176] In addition, the acetaldehyde extraction rate of the lowest boiling point component (4A) was 98%. Acetaldehyde (23 kg / h) was removed by extracting the entire liquid (51 kg / h) removed from the top of the 80-plate distillation column. By such a process, acetaldehyde was produced in the reactor, and 53% of the produced acetaldehyde (43 kg / h) was removed.
[00177] The above process could be operated continuously and steadily. After the process was continuously operated for a predetermined time (250 hours), the concentration of acetaldehyde determined in the reactor was 230 ppm, which revealed that the process could be operated stably while removing acetaldehyde at a high level. The resulting acetic acid product had a permanganate time of 350 minutes. In addition, acetic acid had a propionic acid concentration of 67 ppm. (Example 3)
[00178] The experiment was carried out in the same manner as in Example 1 except that the temperature of the first condensate was 63 ° C.
[00179] The first condensate (in line 43a) fed to storage tank 5 was zero. The composition of the second condensate (in line 38) was as follows: 85.2% by weight methyl iodide, 12.3% by weight methyl acetate, 0.3% by weight acetic acid, 1.8% by weight water , 0.212% by weight acetaldehyde, and 0.001% by weight hydrogen iodide. The feed ratio of the first condensate to the second condensate was 0% by weight relative to 100% by weight. Then, the gas expelled from the storage tank 5 was recycled to line 35 via line 59. The amount (in line 51) of the mixture of the first condensate and the second condensate taken from the storage tank 5, ie the quantity (in line 53) of the condensate fed to the distillation column 6, was 95% of the total amount (the second condensate (line 38)) fed to the storage tank 5. In addition, the composition of the condensate fed to the distillation column 6 was as follows : 85.3% by weight methyl iodide, 12.4% by weight methyl acetate, 0.3% by weight acetic acid, 1.7% by weight water, 0.195% by weight acetaldehyde, and 0.001% by weight iodide of hydrogen.
[00180] The quantity fed to the distillation column 6 is almost equal to that of Comparative Example 1 and those of Examples 1 to 3. In Example 3, the liquid fed to the distillation column 6 was compensated by only the condensate (in line 38) of the second capacitor C4.
[00181] In addition, the acetaldehyde extraction rate of the lowest boiling point component (4A) was 98%. Acetaldehyde (26 kg / h) was removed by extracting the entire liquid (51 kg / h) removed from the top of the 80-plate distillation column. By such a process, acetaldehyde was produced in the reactor, and 60% of the produced acetaldehyde (43 kg / h) was removed.
[00182] The above process could be operated continuously and steadily. After the process was continuously operated for a predetermined time (280 hours), the concentration of acetaldehyde determined in the reactor was 190 ppm, which revealed that the process could be operated stably while removing acetaldehyde at a high level. The resulting acetic acid product had a permanganate time of 400 minutes. In addition, acetic acid had a propionic acid concentration of 57 ppm. INDUSTRIAL APPLICABILITY
[00183] The present invention is significantly useful as a process to stably produce high quality acetic acid while effectively separating and removing acetaldehyde. DESCRIPTION OF THE REFERENCE NUMBERS 1 © © Copyright Reactor 2 © © Copyright flasher (Evaporator) 3 © © Copyright Separating Column (Distillation Column) 4 © © Copyright Decanter 5, 7 © © Copyright Buffer Tank 6 © © Copyright Distillation Column (Acetaldehyde Separation Column) 8 © © Copyright Extraction Unit 9 © © Copyright Storage Tank

权利要求:
Claims (17)
[0001]
1. A process for producing acetic acid comprising: a reaction step to allow methanol to continuously react with carbon monoxide in the presence of a catalyst system containing a metal catalyst, a metal halide, and methyl iodide in a carbonylation reactor (1), a FLASH evaporation step to separate a reaction mixture into a volatile phase (2A) containing produced acetic acid and methyl iodide and a less volatile phase (2B) containing the metal catalyst and metal halide, a distillation step to separate the volatile phase (2A) into a column top effluent (3A) containing methyl iodide and acetaldehyde by-product, and a stream (3B) containing acetic acid, and a condensation step to condense a gas phase, containing at least acetaldehyde, resulting from at least one stage selected from the group consisting of the reaction stage, FLASH evaporation stage and distillation stage, characterized by the fact that the aqueous phase is condensed, in the condensation step, by a plurality of condensers (C1, C2, C3, C4) to form a plurality of condensates sequentially lower in temperature, and acetaldehyde is separated from at least one of the condensates, enriched (s) in acetaldehyde.
[0002]
2. Process according to claim 1, characterized by the fact that the gas phase, containing at least methyl iodide and acetaldehyde, resulting from at least one step of the FLASH evaporation and the distillation step is condensed by the plurality of condensers (C1 , C2, C3, C4).
[0003]
3. Process according to claim 1 or 2, characterized by the fact that at least one gas phase selected from the group consisting of column top effluent (3A) and the volatile phase (2A) is subjected to the plurality of condensers (C1, C2, C3, C4) and cooled to form condensates and non-condensed gaseous components, where the condensates have a lower temperature and a higher concentration of acetaldehyde sequentially in the downstream direction, and acetaldehyde is separated from a condensate or condensates highly enriched in acetaldehyde.
[0004]
Process according to any one of claims 1 to 3, characterized by the fact that the gas phase is condensed by the plurality of capacitors (C1, C2, C3, C4), and an acetaldehyde enriched condensate of at least one among one second and subsequent condensers (C2, C4) a storage tank (5) is stored, and acetaldehyde is separated from the stored condensate.
[0005]
Process according to any one of claims 1 to 4, characterized in that the gas phase is condensed by the plurality of capacitors (C1, C2, C3, C4), a condensate of at least one first capacitor (C1, C3 ) is stored in a decanter (4), an condensate enriched in acetaldehyde of at least one second and subsequent condensers is stored in a storage tank (5), the condensate in the decanter (4) and the condensate in the storage tank (5) are combined and distilled to separate a column top effluent containing acetaldehyde.
[0006]
Process according to any one of claims 1 to 5, characterized in that the volatile phase (2A) is distilled by a first distillation column (3) to form a first column top effluent, the top effluent column as the gas phase is condensed by the plurality of condensers (C3, C4), and (i) an acetaldehyde enriched condensate of at least one of a second and subsequent condensers (C4) is distilled by a second distillation column (6 ), (ii) a condensate of at least one of a second and subsequent condensers (C4) is stored in a storage tank (5), and the stored condensate is distilled through a second distillation column (6), or (iii ) a condensate of at least one first condenser (C3) is stored in a decanter (4), a condensate of at least one of a second and subsequent condensers (C4) is stored in a storage tank (5), the condensate in decanter (4) and the condensate in the tank storage (5) are combined and distilled by a second distillation column (6), to separate a second column top effluent enriched in acetaldehyde.
[0007]
Process according to claim 5 or 6, characterized in that the condensate in the decanter (4) and the condensate in the storage tank (5) are combined in a weight ratio of 0/100 to 95/5 as the former / the latter and distilled by a second distillation column (6).
[0008]
8. Process according to claim 6 or 7, characterized in that the second column top effluent is subjected to extraction with water to form an aqueous phase containing acetaldehyde and an organic phase containing methyl iodide, and the organic phase is recycled to the reactor (1).
[0009]
Process according to any one of claims 1 to 8, characterized in that the volatile phase (2A) as the gas phase is condensed by the plurality of capacitors (C1, C2), a condensate of at least one within a second and subsequent condensers (C2) is distilled by the first distillation column (3) and / or a second distillation column (6) to form a first column top effluent and / or a second column top effluent.
[0010]
Process according to any one of claims 1 to 9, characterized in that the gas phase is condensed by 2 to 5 condensers (C1, C2, C3, C4) positioned in series.
[0011]
Process according to any one of claims 1 to 10, characterized by the fact that a condensate of at least one of a second and subsequent condensers (C2, C4) among the plurality of capacitors (C1, C2, C3, C4) is distilled to separate a column top effluent containing acetaldehyde.
[0012]
Process according to any one of claims 1 to 11, characterized in that the gas phase is cooled by a first condenser (C1, C3) to form a first condensate and a first non-condensed gas component, the first gaseous component non-condensate is cooled by a second condenser (C2, C4) whose cooling temperature is lower than that of the first condenser (C1, C3) to form a second condensate having a temperature lower than that of the first condensate and a second non-gaseous component condensate, and acetaldehyde is separated from at least the second condensate.
[0013]
Process according to any one of claims 1 to 12, characterized in that, in addition, an expelled gas (5A), containing at least methyl iodide and acetaldehyde, resulting from at least one step selected from the group consisting of reaction step, the FLASH evaporation step, the storage step, and at least one distillation step, it is allowed to contact with an absorption solvent, the resulting solvent is extracted to form a gas phase containing at least methyl iodide and acetaldehyde , and acetaldehyde is separated from the gas phase.
[0014]
Process according to any one of claims 1 to 13, characterized in that a condensate in a first condenser (C1, C3) has a temperature no higher than 110 ° C, and a condensate in at least one among one second and subsequent capacitors (C2, C4) have a temperature no higher than 45 ° C.
[0015]
15. A method for separating or removing acetaldehyde comprising: distilling a mixture containing acetic acid, methyl acetate, methyl iodide, methanol, water and acetaldehyde to form a gas phase containing at least methyl iodide and acetaldehyde and a liquid phase containing at least water and methanol, and to condense the gas phase to separate acetaldehyde from the gas phase, characterized by the fact that the aqueous phase is condensed, in a condensation step, by a plurality of condensers (C1, C2, C3, C4) to form a plurality of condensates sequentially lower in temperature, and acetaldehyde is separated from at least one of the condensates enriched in acetaldehyde.
[0016]
16. Method according to claim 15, characterized in that a condensate in a first condenser (C1, C3) has a temperature of 20 ° C to 110 ° C, and a condensate in at least one of a second and subsequent condensers (C2, C4) have a temperature of -5 ° C to 30 ° C.
[0017]
17. Method according to claim 15 or 16, characterized in that a condensate of at least one of a second and subsequent condensers (C2, C4) is distilled to form a column top effluent containing acetaldehyde, and the effluent column top is subjected to extraction with water to form an aqueous phase containing acetaldehyde and an organic phase.

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法律状态:
2018-11-21| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|

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2019-08-13| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2020-12-08| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2021-01-05| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 02/12/2013, OBSERVADAS AS CONDICOES LEGAIS. |

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2021-03-30| B16C| Correction of notification of the grant [chapter 16.3 patent gazette]|Free format text: REF. RPI 2609 DE 05/01/2021 QUANTO AO ENDERECO. |

优先权:

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JP2012-279114|2012-12-21|

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JP2012279114|2012-12-21|

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PCT/JP2013/082334|WO2014097867A1|2012-12-21|2013-12-02|Method for producing acetic acid|

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