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    • 专利摘要:
    The present invention relates to the implementation of a separator wall column as a purification / finishing column in a (meth) acrylic acid recovery process based on the implementation of two distillation columns in the absence of external organic solvent. The process according to the invention makes it possible to improve the energy balance of the process while improving the technical quality of the (meth) acrylic acid recovered. The method according to the invention also makes it possible to directly produce polymer grade (or glacial) (meth) acrylic acid of improved quality when a chemical treatment agent of the residual aldehydes is introduced upstream or in the wall column. separating.
    公开号:FR3064630A1
    申请号:FR1752902
    申请日:2017-04-04
    公开日:2018-10-05
    发明作者:Michel Fauconet；Serge Tretjak
    申请人:Arkema France SA；
    IPC主号:
    专利说明:

    TECHNICAL AREA
    The present invention relates to the production of (meth) acrylic acid.
    It relates more particularly to the implementation of a column with a separating wall as a purification / finishing column in a recovery process of (meth) acrylic acid based on the implementation of two distillation columns in the absence of external organic solvent. The process according to the invention improves the energy balance of the process while improving the technical quality of the (meth) acrylic acid recovered.
    The method according to the invention also makes it possible to directly produce (meth) acrylic acid of polymer (or glacial) grade of improved quality when an agent for the chemical treatment of residual aldehydes is introduced upstream or into the wall column. separator.
    TECHNICAL BACKGROUND AND TECHNICAL PROBLEM
    The acrylic acid synthesis process exploited on a large industrial scale, implements a catalytic oxidation reaction of propylene in the presence of oxygen.
    This reaction is generally carried out in the gas phase, and most often in two stages: the first stage carries out the substantially quantitative oxidation of propylene to a mixture rich in acrolein, then, during the second stage carries out the selective oxidation of the acrolein to acrylic acid.
    The gaseous mixture resulting from the second stage consists, apart from acrylic acid, of non-transformed compounds derived from the reactants involved or from impurities generated during at least one of the 2 reaction stages, namely
    - light compounds which cannot be condensed under the temperature and pressure conditions usually used, essentially: propylene, propane, nitrogen, unconverted oxygen, carbon monoxide and dioxide formed in small quantities by ultimate oxidation;
    - light condensable compounds, essentially: water, light aldehydes such as unconverted acrolein, formaldehyde, glyoxal and acetaldehyde, formic acid, acetic acid, propionic acid;
    - heavy compounds: furfuraldehyde, benzaldehyde, maleic acid and anhydride, benzoic acid, 2-butenoic acid, phenol, protoanemonin.
    The complexity of the gaseous mixture obtained in this process requires carrying out a set of operations to recover the acrylic acid contained in this gaseous effluent and transform it into a grade of acrylic acid compatible with its end use, for example the synthesis of 'acrylic esters or the production of acrylic acid polymers and / or acrylic esters.
    A new technology for recovery / purification of acrylic acid has appeared recently, involving a reduced number of purification steps and requiring no external organic solvent.
    Patent EP 2 066 613, based on this "solvent-free" technology, describes a process for recovering acrylic acid without using external water or azeotropic solvent. This process uses only two distillation columns to purify the cooled gaseous reaction mixture: a) a dehydration column, b) and a finishing column (or purification column) fed by part of the bottom flow from the column dehydration.
    According to this process, the cooled gaseous reaction stream is subjected to dehydration in a first column. The gas flow distilled at the top of the column is partially condensed in a condenser, generating a liquid reflux returned to the dehydration column which participates in the absorption / condensation of acrylic acid, the non-condensed gaseous effluent being returned at least in part towards the reaction and the rest being eliminated.
    The flow from the bottom of the dewatering column is partially sent to a second column called the finishing column. The other part of this liquid flow is returned via a heat exchanger in the lower part of the dehydration column, thus forming a recirculation loop. During the purification / finishing step, a stream rich in heavy compounds is removed at the bottom, and at the top is recovered a distillate comprising water and light by-products which is condensed and then recycled at the bottom of the first column. dehydration. The liquid flow coming from the bottom of the dehydration column and sent to the finishing column, containing the (meth) acrylic acid and the light and heavy impurities coming from the absorption - condensation stage, as well as the liquid flow coming from the head of the recycled finishing column at the bottom of the dehydration column, containing a flow of (meth) acrylic acid enriched in light compounds, form a recycling loop between the 2 columns.
    A stream of purified acrylic acid is recovered in the form of liquid or vapor, by lateral withdrawal of the finishing column. The acrylic acid obtained is generally of purity greater than 98.5% by mass and contains less than 0.5% by mass of water and less than 0.4% by mass of acetic acid. Among the other impurities still present, there are in particular heavy compounds such as aldehydes and protoanemonin.
    The purified acrylic acid can be used as technical grade acrylic acid without further purification, for example to produce esters, or can be subjected to an additional treatment by fractional crystallization to remove residual impurities and lead to a quality of acrylic acid. of polymer grade (also called glacial).
    The finishing column usable in the process described in document EP 2 066 613 can be of any configuration, for example packed column, column with trays, column with separating wall; the filling can be of any type, loose or structured, and the number of theoretical plates is not limited.
    The operating conditions in temperature and pressure for the finishing column are not critical in this process, and can be determined in accordance with the distillation methods known in the state of the art. However, preferably, the purification column is operated at a pressure below atmospheric pressure, making it possible to operate at relatively low temperatures, thus avoiding the polymerization of the unsaturated products present, and minimizing the formation of heavy by-products.
    Despite the advantages of the purification process described in document EP 2 066 613, there are still disadvantages.
    For the production of polymers of (meth) acrylic acid or esters of (meth) acrylic acid, it is necessary to produce a quality of technical (meth) acrylic acid sufficiently free of certain annoying impurities. For example, heavy impurities such as furfural, benzaldehyde and protoanemonin are troublesome because they react in the polymerization process. Other light impurities, such as acetic acid, can generate volatile organic compounds which remain inside the (meth) acrylic acid polymer and make it unfit for reuse.
    Finally during the production of esters by reaction between (meth) acrylic acid of technical grade and an alcohol, the impurities having a carboxylic function, such as acetic acid, crotonic acid, or the acid or the maleic anhydride form impurities which are difficult to remove and which can deteriorate the esterification reaction yields by partially consuming the alcohol used during the reaction.
    In order to avoid these problems, it is necessary to use a finishing column having a large number of rectification stages.
    Acrylic acid is a product which is very sensitive to radical polymerization, which leads to the formation of insoluble polymers which foul equipment and require costly installation downtime for cleaning.
    The addition of polymerization inhibitors reduces this parasitic reaction, but this solution is not sufficient for continuous production for long periods, in particular when the temperature inside the column or its equipment is too high. In addition, the distribution of the inhibitor on the trays or the packing of the column is generally made difficult because of the dead centers generated by the structure, difficult to reach by the liquid reflux containing the polymerization inhibitors.
    Thus, the distillation operations for the purification of streams rich in acrylic acid are carried out under reduced pressure, so as to limit the temperature, and the distillation columns are generally equipped with simple packings, to allow efficient distribution of the liquid containing the inhibitors. and avoid the accumulation of precursor polymers. Perforated tray columns are for example used.
    In general, the column internals making it possible to reduce the initiation phenomena of polymerization generate more pressure drops per theoretical plate installed, than the more efficient columns but more favorable to the formation and accumulation of polymers.
    The increase in the number of grinding plates to achieve an improved quality of technical acrylic acid then leads to an increase in the overall pressure drop of the column, which results in an increase in the temperature in the column and a worsening of sensitivity to polymerization.
    Acrylic acid also has the distinction of easily forming Michael addition derivatives, such as 3-acryloxypropionic acid, also called acrylic acid dimer. These compounds are heavy products which reduce the recovery yield by consuming the monomeric acrylic acid.
    Like radical polymerization, this covalent reaction to form Michael derivatives is strongly favored by temperature. Consequently, the establishment of columns with a high number of rectification plates to meet the quality requirements of acrylic acid leads to drawbacks in terms of product loss, which can only be partially compensated for by additional treatment. high temperature cracking of Michael derivatives to regenerate the acrylic acid monomer.
    Thus, there is an important advantage of carrying out the separation by reducing the number of theoretical rectification plates, both to reduce the risk of polymerization and the formation of Michael adducts, these two undesirable effects being favored by a higher temperature.
    In addition, the elimination of light impurities (mainly water and acetic acid) in a solvent-free process as described in document EP 2 066 613 requires a recycling loop between the 2 columns, the flow of which is high and inversely proportional to the efficiency of the finishing column. An increase in the recycling rate to compensate for insufficient efficiency thus leads to additional energy consumption.
    The inventors have discovered that the use of a column equipped with a separating wall and its implementation under special conditions, as a finishing column in the process of document EP 2 066 613, makes it possible to overcome the aforementioned drawbacks by leading to a significant energy gain during the purification of acrylic acid while producing a better quality of technical acrylic acid.
    When a distillation column is equipped with a separating wall, the wall being contiguous with the upper dome of the column at the top, and not contiguous with the bottom of the column at the bottom, the column has two sections, the lower space communicates with the column bottom space and whose head space is separated into two hermetic zones.
    When the finishing column meets this configuration, the inventors have discovered that the light compounds and the water contained in the feed flow of the finishing column are eliminated more efficiently from the feeding section, and can be recycled into bottom of the dehydration column in a recycling loop with a lower flow rate, while making it possible to extract, at the top of the other section, acrylic acid with improved purity; and the flow of heavy products forming in the lower space of the column is eliminated at the bottom of the finishing column.
    The inventors have also discovered that in this configuration, when an agent for the chemical treatment of residual aldehydes is introduced upstream or into the column with a separating wall, it is possible to recover at the head of this column directly an acrylic acid of polymer grade, this acrylic acid of polymer grade being of superior quality, in particular as regards the residual content of water, acetic acid and protoanemonin.
    It has already been suggested in patent application PCT / LR2016 / 052434 in the name of the Applicant to use a column with a separating wall as a finishing column with the presence of an agent for the chemical treatment of residual aldehydes, in a process for recovery of polymer grade acrylic acid.
    In this process, the separating wall of the finishing column is not joined with the upper part of the column. The finishing column is supplied at the head on one side of the wall by the flow from the bottom of the dehydration column, and a flow of acrylic acid of polymer grade is obtained by lateral withdrawal in the section located on the other side of the separating wall. On the side of the separating wall supplied with a flow of acrylic acid to be purified, that is to say in the supply section, the elimination of the light compounds (mainly acetic acid and water) is carried out, and the residual flow back to the bottom of the column containing acrylic acid enriched in heavy compounds (including the reaction products with the chemical agent) is distilled in the withdrawal section located on the other side of the separating wall.
    The purified acrylic acid is collected by lateral racking in this second section. The gas flow obtained at the head of this withdrawal section is mixed with the gas flow comprising the light compounds eliminated at the head of the feed section, then returned in liquid form, after condensation, in the recirculation loop at the bottom of the column dehydration. The liquid flow from the bottom of the dewatering column supplying the finishing column and the flow from the head of the finishing column recycled to the dewatering column constitute a recycling loop containing mainly acrylic acid.
    The acrylic acid obtained according to this process is of polymer grade, having an acrylic acid content by weight> 99%, preferably> 99.5%, and having a total aldehyde content <10 ppm, even <3 ppm. It also contains less than 5 ppm protoanemonin.
    In the purification scheme described in patent application PCT / FR2016 / 052434, to obtain a flow of acrylic acid sufficiently free of water and acetic acid, it is necessary to maintain a sufficient flow rate of overhead flow enriched with light compounds from the finishing column to the dehydration column. This head flow is mainly made up of acrylic acid which we wish to recover in full. The recycling of a large flow from the head of the finishing column to the dewatering column is accompanied by an increased feed rate from the flow from the bottom of the dehydration column to the feeding of the finishing column. Consequently, it is the flow rate of the entire recycling loop which is impacted, and it is necessary to have sufficient energy to ensure the vaporization of the recycling loop. In these conditions only, it is possible to avoid "polluting" with acrylic acid the lateral filling acrylic acid and guarantee a constant quality of acrylic acid of polymer grade.
    In addition, the chemical agents used for the removal of aldehydes are not reactive enough for the removal of protoanemonin impurity, which is a heavy lactone-like compound. The complete elimination of protoanemonin to very low contents, in order to obtain a quality of glacial (meth) acrylic acid compatible with the manufacture of polymers of high molecular weights, requires a very high column efficiency. The presence of protoanemonin in acrylic acid of polymer grade, even at a concentration as low as 5 ppm, even 3 ppm, can be prohibitive for the manufacture of acrylic acid polymers or high molecular weight acrylic acid salts .
    However, this elimination of protoanemonin remains an unsolved problem in this process. Indeed, obtaining the purified product in lateral racking, that is to say at a point located lower than the head of the racking section, reduces the height of the separation section located below this racking . Therefore, to obtain a flow of acrylic acid completely free of protoanemonin, it is necessary to set up a very high efficiency column. The disadvantages generated are the investment cost, an increase in the formation of 3-acryloxypropionic acid (AA dimer) and an increased risk of polymerization, since the addition of rectifying plates of a distillation column causes an increase in the total pressure drop in the column and consequently an increase in the temperature at the bottom of the column.
    There therefore remains a need to improve the elimination of protoanemonin impurity in the processes for the recovery of acrylic acid of polymer grade described in the prior art.
    It has now been discovered that a finishing column equipped with a separating wall implemented under special conditions, makes it possible to meet this need, and leads to a acrylic acid of polymer grade comprising less than 2 ppm of protoanemonin, and a mass water content of less than 0.1%.
    SUMMARY OF THE INVENTION
    The subject of the present invention is a process for recovering purified (meth) acrylic acid, in the absence of organic solvent, from a gaseous reaction mixture comprising (meth) acrylic acid obtained by oxidation in the gas phase a (meth) acrylic acid precursor, comprising at least the following steps:
    a) the gaseous reaction mixture is subjected to dehydration without using an azeotropic solvent in a first distillation column called the dehydration column, leading to an overhead stream at least part of which is condensed and returned to the dehydration column in the form of reflux, and to a bottom flow of which at least part is returned to reflux in the lower part of the dehydration column to form a recirculation loop;
    b) the bottom stream from the dehydration column is sent at least in part to a second distillation column called the finishing column, making it possible to separate a bottom stream containing heavy compounds and a top stream containing light compounds, including at least part is returned to the dehydration column;
    said process being characterized in that:
    i) the finishing column is equipped with a separating wall, the wall being contiguous with the upper dome of the column at the top and not contiguous with the bottom of the column at the bottom, thus separating the column into two sections equipped with internal distillation elements ensuring gas-liquid contact, the lower space of which communicates with the column bottom space, and the head space of which is separated into two hermetic zones, the supply of said column being effected on one side of the separating wall, and ii) a gas flow rich in light compounds and comprising water and acetic acid is extracted at the top of the feed section, then recycled, after condensation, to the less partially in the recirculation loop at the bottom of the dehydration column, and iii) a flow of purified (meth) acrylic acid extracted in gaseous form from the finishing column at the top of the section located on the other side of the feed section, is withdrawn after s condensation, part of the condensed flow being returned as liquid reflux at the top of the withdrawal section.
    For the sake of simplification in the remainder of the description of the invention, by “feed section” is meant the section of the column with a separating wall which is supplied by the flow of (meth) acrylic acid to be purified; and "draw-off section" means the section of the column with a separating wall from which the stream of purified (meth) acrylic acid is extracted at the top.
    According to a first particular embodiment, the supply to the finishing column is carried out at the head at the level of the upper plate of the supply section, and optionally, part of the gas flow, which is extracted at the head of the feed section, is returned after condensation, in the feed stream of the finishing column.
    According to a second particular embodiment, the supply of the finishing column takes place at a point located lower than the upper plate of the supply section, and part of the gas flow which is extracted at the head of the section feed, is returned after condensation as liquid reflux at the top of the feed section.
    According to these two embodiments, the method according to the invention makes it possible to produce a flow of purified (meth) acrylic acid of better quality, while making it possible to reduce the flow rate of the recycling loop composed of the bottom of the dehydration column. and the finishing column head, and therefore reduce the associated energy.
    The flow of purified (meth) acrylic acid extracted at the top of the finishing column can be used directly as technical grade (meth) acrylic acid without further purification.
    In particular, technical grade (meth) acrylic acid advantageously has the following mass contents of impurities:
    Water: <0.2%, preferably <0.05%
    Acetic acid: <0.2%, preferably <0.05%
    Furfural: <0.05%, preferably <0.02%
    Benzaldehyde: <0.05%, preferably <0.02%
    Protoanemonin: <0.05%, preferably <0.02%.
    As an alternative, it can be subjected to an additional treatment by fractional crystallization, or by distillation in the presence of a compound reacting with the residual aldehydes, leading to a quality of (meth) acrylic acid of polymer grade.
    The method according to the invention may also comprise the introduction into the finishing column, of a chemical treatment agent aimed at reducing the content of residual aldehydes, the flow of (meth) acrylic acid extracted at the top of the column finishing then being directly a flow of (meth) acrylic acid of polymer grade.
    According to certain particular embodiments, the process according to the invention leading to a (meth) acrylic acid of polymer grade can also have at least one of the advantageous characteristics listed below:
    - the chemical treatment agent is introduced into the feed stream of the finishing column;
    - the chemical treatment agent is introduced via a mixing device comprising at least one capacity ensuring the effective dispersion of the chemical agent with the feed stream;
    - the chemical treatment agent is introduced directly into the finishing column at a point between the head and the foot of the column, lower than the tray where the column is fed, preferably at a point located between about one third and two thirds of the height of the feed section of the finishing column.
    - a lateral withdrawal of a gas stream comprising intermediate-quality (meth) acrylic acid is carried out from the withdrawal section.
    In all of its variants, the polymer-grade (meth) acrylic acid drawn off at the top of the finishing column, has a (meth) acrylic acid content by weight> 99.5%, and contains less than 2 ppm of protoanemonin, preferably less than 1 ppm of protoanemonin, a mass content of water less than 0.1%, preferably less than 0.05%, a mass content of acetic acid less than 0.2%, preferably less than 0.05 %. In addition, the content of total aldehydes is less than 10 ppm, preferably less than 3 ppm.
    Another object of the invention is a process for the production of purified (meth) acrylic acid comprising at least the following steps:
    A) at least one (meth) acrylic acid precursor is subjected to gas phase oxidation to form a gaseous reaction mixture comprising (meth) acrylic acid;
    B) the gaseous reaction mixture is cooled;
    C) the cooled gaseous reaction mixture is subjected to the recovery process of (meth) acrylic acid as defined above.
    The process according to the invention may also comprise other preliminary, intermediate or subsequent steps, provided that they do not adversely affect the production of the purified (meth) acrylic acid.
    According to an embodiment of the invention, the precursor of (meth) acrylic acid is acrolein.
    According to one embodiment of the invention, acrolein is obtained by oxidation of propylene or by oxideshydrogenation of propane.
    According to an embodiment of the invention, the precursor of (meth) acrylic acid is methacrolein.
    According to one embodiment of the invention, methacrolein is obtained by oxidation of isobutylene and / or tert-butanol.
    According to an embodiment of the invention, methacrolein is obtained from the oxidationhydrogenation of butane and / or isobutane.
    According to an embodiment of the invention, the gaseous reaction mixture comprising (meth) acrylic acid obtained by gas phase oxidation of a (meth) acrylic acid precursor comprises carbon of renewable origin.
    According to an embodiment of the invention, the precursor of (meth) acrylic acid is derived from glycerol, 3-hydroxypropionic acid or 2hydroxypropionic acid (lactic acid).
    According to a preferred embodiment of the invention, the gaseous reaction mixture comprises acrylic acid derived from propylene obtained according to an oxidation process in two stages.
    In its preferred embodiment, using a residual aldehyde treatment agent, the method according to the invention directly produces a flow of (meth) acrylic acid of polymer grade, corresponding to a higher quality for producing polymers of high molecular mass , usable for example as superabsorbents.
    The process according to the invention does not require the use of an external organic solvent to remove the water contained in the gaseous reaction mixture comprising (meth) acrylic acid. It does not require additional crystallization treatment, which is costly in energy.
    The method according to the invention uses only a dehydration column and a finishing column which can include a step of treatment of aldehydes using a chemical agent, carried out inside a finishing column having a separating wall in a particular configuration. The physical separation via the separating wall, between the feed stream and the purified acid leads to an increase in the number of theoretical stages, for a height of the finishing column and an assembly of fixed internal distillation elements, on the one hand to efficiently separate the light compounds and obtain an energy gain for recycling, on the other hand to efficiently separate the heavy compounds and obtain a better quality of purified (meth) acrylic acid. It also results in a decrease in the amount of chemical agent required to remove residual aldehydes which are more effectively separated in the finishing column.
    According to the invention, it is possible to guarantee a constant quality of acrylic acid of polymer grade with an optimized purification cost.
    Other characteristics and advantages of the invention will emerge more clearly on reading the detailed description which follows, with reference to the appended FIGS. 1 to 4 which represent:
    - Figure 1: Installation adapted to the implementation of the process of the prior art described in patent EP 2 066 613.
    - Figure 2: Installation adapted to the implementation of the recovery process of purified (meth) acrylic acid according to a first embodiment of the invention, with the possible addition of a chemical treatment agent.
    - Figure 3: Installation adapted to the implementation of the recovery process of purified (meth) acrylic acid according to a second embodiment of the invention, with the possible addition of a chemical treatment agent.
    - Figure 4: Installation according to the prior art adapted to the implementation of a recovery process of (meth) acrylic acid of polymer grade using a distillation column with a separating wall as a finishing column.
    DETAILED DESCRIPTION OF THE INVENTION
    In the present invention, the term "(meth) acrylic" means "acrylic" or "methacrylic". For simplification, the rest of the presentation will refer to the production of acrylic acid, but also applies by analogy to the production of methacrylic acid.
    The term “external organic solvent” designates any organic compound in which the (meth) acrylic acid is soluble and whose origin is external to the process, used as solvent for absorption, extraction or azeotropic distillation
    The term "azeotropic solvent" designates any organic solvent having the property of forming an azeotropic mixture with water.
    The term "non-condensable" or "noncondensable" denotes compounds whose boiling point is below the temperature of 20 ° C under atmospheric pressure.
    The term “light”, qualifying the by-product compounds, designates the compounds whose boiling point is lower than that of (meth) acrylic acid under the working pressure considered, and by analogy, the term “heavy” denotes compounds whose boiling point is higher than that of (meth) acrylic acid.
    The term "aldehyde chemical treatment agent" means a chemical compound which forms heavier reaction products with aldehydes which are more easily separable from (meth) acrylic acid by distillation, thereby reducing to a level very low the rate of aldehydes present in the medium to be treated.
    By "chemical treatment" is meant the treatment carried out with the aid of the chemical treatment agent for aldehydes.
    This type of treatment and the compounds that can be used are well known in the art, without the reactions or complexations used being completely identified. The main mode of action is to form heavier reaction products than the aldehydes to be treated.
    The term chemical aldehyde treatment agent excludes polymerization inhibitors which, although they may have a minor effect on aldehydes, are generally introduced for the sole purpose of stabilizing fluxes containing (meth) acrylic derivatives. vis-à-vis a polymerization, these polymerization inhibitors can be introduced at different levels and / or in different flows of the installation.
    The term "polymer grade" and the term "glacial" have the same meaning and indicate that (meth) acrylic acid meets high quality criteria for its use in the manufacture of high molecular weight (meth) acrylic polymers.
    By “recycling loop” between the 2 columns is meant the loop formed by the liquid flow coming from the bottom of the dewatering column and sent to the finishing column, and by the liquid flow coming from the head of the recycled finishing column. at the bottom of the dehydration column.
    The invention aims to produce high purity acrylic acid with an optimized purification cost, and it is based on the use under special conditions of a column equipped with a separating wall as a finishing column in a prior art purification process involving a reduced number of distillation columns and requiring no external organic solvent.
    According to this process of the prior art represented in FIG. 1, a gaseous reaction mixture 1 comprising acrylic acid obtained by oxidation in the gas phase of a precursor of acrylic acid feeds a first distillation column 10. The mixture gaseous reaction comprising a water / acrylic acid mass ratio generally between 0.3 and 2, preferably between 0.3 and 1.2, can be cooled beforehand before being subjected to dehydration in the dehydration column 10.
    The reaction mixture comprises, in addition to water and acrylic acid, incondensable light products such as nitrogen, oxygen, carbon monoxide and dioxide, as well as various light or heavy by-products of different nature. chemical, which may be light aldehydes such as acrolein, formaldehyde, acetaldehyde or glyoxal, heavy aldehydes such as furfuraldehyde or benzaldehyde, light acids such as formic acid, acetic acid or propionic acid, heavy acids such as maleic acid, benzoic acid or 2-butenoic acid, and protoanemonin, a heavy lactone type compound.
    The dehydration column leads to a top flow 2, at least part of which is condensed in a condenser 13 and returned to the dehydration column in the form of reflux 7 to absorb acrylic acid, the other part (flow 14 and 15 ) comprising the incondensable light compounds being generally sent partially or totally to a purification device or partially recycled to other stages of the acrylic acid production process, preferably in a stage situated upstream of the reactor for producing the mixture reaction 1.
    The entire overhead stream from the dewatering column can be sent to the overhead condenser 13.
    The purpose of the dehydration step is to eliminate in a head stream most of the water present in the reaction mixture, but also the light noncondensable compounds and the light condensable compounds. It generates a head flow 2 comprising most of the water and light compounds, with acrylic acid and heavy compounds in very small quantities, and a foot flow 16 depleted in light compounds comprising almost all acrylic acid with heavy by-products, and a mass content of water generally less than 10%, preferably less than 7%.
    A typical mass composition of the bottom stream 16 of the dehydration column essentially comprises acrylic acid (84-90%), acetic acid (2-10%), water (2-10%) , and heavy by-products.
    The dehydration column generally comprises from 5 to 50 theoretical plates, preferably from 20 to 30 theoretical plates.
    Advantageously, the dehydration column operates at atmospheric pressure or slightly higher, up to an absolute pressure of 1.5 10 5 Pa.
    Advantageously, the temperature in the upper part of the dehydration column is at least 40 ° C, preferably is between 40 ° C and 80 ° C. The temperature of the bottom stream of the dehydration column preferably does not exceed 120 ° C.
    The bottom stream 16 of the dehydration column is sent at least in part (stream 3), at the head of a second distillation column 17, called the purification column or finishing column, in which a top stream 8 is separated and a foot flow 9.
    A portion 20 of the liquid flow 16 at the bottom of the dewatering column is sent to a heat exchanger 12 which can be a heater or a cooler and reinjected into the dewatering column, so as to constitute a recirculation loop at the bottom. Preferably, the part 11 of the foot loop is reinjected between the supply of the reaction gas mixture and the head of the dehydration column.
    The remainder (stream 3) of the liquid stream 16 is sent to supply the finishing column 17.
    The finishing column 17 is generally a conventional distillation column comprising from 5 to 30 theoretical plates, preferably from 8 to 20 theoretical plates. This distillation column is associated at the bottom with at least one reboiler 18 and at the top with a condenser 19.
    The temperature and pressure in column 17 are not critical, and can be determined in accordance with known distillation methods in the art. However, preferably, the finishing column 17 operates at a pressure below atmospheric pressure, making it possible to operate at relatively low temperatures, thus avoiding the polymerization of the unsaturated products present, and minimizing the formation of heavy by-products.
    Advantageously, the finishing column operates under an absolute pressure ranging from 5 kPa to approximately 60 kPa, the temperature of the overhead flow being advantageously between 40 ° C and about 90 ° C, and the temperature of the bottom flow being between 60 ° C and 120 ° C.
    The overhead gas flow 8 from the finishing column is sent to the condenser 19, and the outgoing liquid flow 4 is returned to the dewatering column, mixed with the flow from the bottom loop of the dewatering column. The head stream 8 essentially comprises water and the light condensable by-products.
    The stream 9 separated at the bottom of the finishing column comprises most of the heavy by-products, in particular Michael adducts such as 3acryloxypropionic acid, anhydride / maleic acid, benzoic acid, as well as polymerization inhibitors. This flow 9 can be partly recycled at the bottom of the finishing column, or used as a raw material for preparing acrylic esters (flow 6).
    A stream 5 comprising purified acrylic acid in the form of liquid or vapor, preferably gaseous, is extracted from the finishing column by lateral withdrawal. This flow 5 corresponds to technical grade acrylic acid.
    Figure 2 shows an installation suitable for implementing the recovery process of purified (meth) acrylic acid according to a first embodiment of the invention.
    This installation differs from the installation of the prior art in that it includes, as finishing column 17, a column equipped with a separating wall, the wall being contiguous with the upper dome of the column in the upper part and not contiguous with the bottom of the column in the lower part. The wall thus separates the column into two sections equipped with trays 35 and 36, the lower space of which communicates with the column bottom space, and the head space of which is separated into two hermetic zones.
    The number of theoretical plates necessary for the separation of the light compounds, in the feed section 35 is generally between 5 and 20 In the withdrawal section, the number of theoretical plates is generally between 2 and 20 theoretical plates T
    The sections of the column can be equipped with all types of internal, for example: bulk or ordered packings, perforated trays without weirs or with weirs such as bell trays, trays with fixed or mobile valves, etc.
    The feeding of the finishing column is carried out on one side of the separating wall, in the feeding section 35.
    The flow of crude acrylic acid 3 obtained at the bottom of the dehydration column
    10, is sent to section 35 at the top of the finishing column.
    According to this first embodiment, the feed to the finishing column is effected at the head at the level of the upper plate of the feed section.
    A gas stream 4 rich in light compounds and comprising water is extracted at the head of section 35, condensed in an exchanger 40 and recycled at least in part in the recirculation loop at the bottom of the dehydration column, in the stream 20.
    Part of the flow 4 which is extracted at the head of the feed section can advantageously be returned after condensation in the feed flow of the finishing column.
    The stream obtained at the bottom of section 35 containing acrylic acid, free of light compounds and of water, is purified in section 36 with a view to eliminating at the bottom a stream 9 rich in heavy compounds. This flow 9 is partly recycled at the bottom of the finishing column, through a reboiler 18, and the remainder is withdrawn. This withdrawn stream (stream 6) contains residual acrylic acid and heavy compounds of the Michael addition type (3-acryloxypropionic acid). Advantageously, it can be sent to a recovery section for the purpose of recovering acrylic acid, for example by distillation in an evaporator, or by thermal cracking in a high temperature reactor, so as to regenerate the monomer from derivatives of Michael, or by combining these two types of equipment. Alternatively, stream 9 can also be used as a raw material rich in acrylic acid and in heavy products derived from Michael reactions for the synthesis of esters, in particular under conditions favorable to the cracking of these heavy and to the subsequent regeneration of the monomer.
    In general, the finishing column with a separating wall will operate under vacuum in a pressure range ranging from 5 kPa to 60 kPa, (50 mbar to 600 mbar) preferably between 5 and 20 kPa, with a temperature at the top of the column. between 50 ° C and 80 ° C, and a temperature at the bottom of the column between 85 ° C and 120 ° C. The ratio of the mass flow rate between the withdrawal at the top of the column (5) and the bottom flow rate (6) is at least 75/25, preferably at least 95/5. Furthermore, the mass ratio of the return flow rate of the flow from the top of the finishing column to the dewatering column (flow 4) over the sum of the flows drawn off at the head (5) and at the bottom of the column (6) is generally understood between 1 and 4.
    At the head of section 36, a gas stream of purified acrylic acid is extracted from the finishing column. Part of this flow, after condensation, is added with polymerization inhibitors, then returned as liquid reflux at the top of the withdrawal section. The polymerization inhibitors used are of a nature and in concentration suitable for the use of the technical acrylic acid thus recovered.
    Figure 3 shows an installation suitable for implementing the recovery process of purified (meth) acrylic acid according to a second embodiment of the invention.
    According to this second embodiment, the supply of the finishing column is carried out at a point situated lower than the upper plate of the supply section, preferably at a point situated between a quarter and three quarters of the height from the feed section and part of the gas flow 4 which is extracted at the head of the feed section is returned after condensation as liquid reflux at the head of the feed section.
    In the same way as the first embodiment of the invention, the flux obtained at the foot of section 35 containing acrylic acid, free of light compounds and of water, is purified in section 36 in order to eliminate at the bottom a stream 9 rich in heavy compounds. This stream 9 is partly recycled at the bottom of the finishing column, through a reboiler 18, and the balance is withdrawn (stream 6), to be advantageously sent to a section for recovering the residual monomer present in free form or combined (3-acryloxypropionic acid), or in a unit for producing acrylic esters, as described in the first embodiment of the invention.
    At the head of section 36, a gas stream of purified acrylic acid is extracted from the finishing column. Part of this flow, after condensation, is added with polymerization inhibitors, then returned as liquid reflux at the top of the withdrawal section. The polymerization inhibitors used are of a nature and in concentration suitable for the use of the technical acrylic acid thus recovered.
    According to these two embodiments of the invention shown in Figures 2 and 3, a solid recovery device (not shown in the figures), for example a filter, can be placed in line or bypass on the recirculation loop at the bottom of the finishing column, in order to avoid potential fouling of the finishing column.
    Compared to the configuration using a conventional finishing column shown in FIG. 1, the invention according to the two embodiments makes it possible to implement, for the same number of trays installed, a lower column height operating at a pressure and lower temperatures; as a result, acrylic acid can be produced reliably and continuously, without interruption caused by the deposition of polymer solids on the equipment. In addition, the addition of polymerization inhibitor can be carried out in a smaller quantity to avoid the formation of polymers of acrylic acid in the column. Furthermore, for the same column height, the invention leads to a better quality of technical acrylic acid and a reduction in the flow rate of the recycling loop at the top of the finishing column.
    When a chemical treatment agent intended to reduce the content of residual aldehydes is also introduced into the finishing column with a separating wall, represented by flow 22, in FIGS. 2 and 3, the purified acrylic acid extracted at the top of the withdrawal section 36 corresponds directly to a quality of acrylic acid of polymer grade.
    The agents for the chemical treatment of aldehydes which can be used in the invention may be those described in the prior art for processes combining purification by distillation and chemical treatment of the aldehydes contained in a technical acrylic acid. They can be chemical agents used alone or in a mixture in all proportions.
    We can cite in particular:
    • amines, such as, for example, without limitation, monoethanolamine, ethylene diamine glycine, diethylenetriamine, dipropylenetriamine, ortho-, para-, and meta-phenylenediamine;
    • compounds of the aniline family, such as, for example, without limitation, aniline, ortho-, para-, and meta-methylaniline;
    • compounds of the hydrazine family, such as, without limitation, hydrazine and its salts, hydrazine hydrate, hydrazine sulfate, hydrazine carboxylates, hydrazine hydrochloride, phenylhydrazine, 4-nitrophenylhydrazine, and 2,4dinitrophenylhydrazine, or alternatively aminoguanidine and its salts, such as aminoguanidine hydrogen carbonate;
    • Compounds of the hydrazide family, such as, for example, without limitation, the hydrazides of carboxylic acids and their salts, such as the hydrazides of formic, acetic, propionic, butanoic, pentanoic, maleic acids and the dihydrazides of acids adipic and succinic, urea or derivatives of urea and hydrazine, such as semicarbazide or carbohydrazide and their salts;
    alone or their mixtures in all proportions.
    Preferably used in the invention, hydrazine or a hydrazine derivative, or an aminoguanidine salt, such as aminoguanidine hydrogen carbonate to reduce the content of residual aldehydes.
    The chemical agents are introduced as such into the flow to be treated, or in solution in a solvent, for example in solution in acrylic acid.
    The chemical agent is introduced in a minimum quantity to obtain a quality of glacial acrylic acid sufficiently free of aldehydic impurities (in particular acrolein, furfuraldehyde and benzaldehyde) to meet the needs of customers. In general, the chemical agent is added in a molar ratio of 0.5 to 10, preferably 1 to 5, relative to all of the aldehydes present in the medium to be treated.
    The chemical agent can be introduced into the flow which feeds the feed section 35, by means of a mixing device 38.
    According to this embodiment of the invention (represented in FIG. 2 and FIG. 3), the mixing of the chemical treatment agent for aldehydes with the flow 3 is carried out upstream of the finishing column, in a device for mixture 38 allowing the most effective dispersion of the chemical treatment agent in the stream. This device can in particular contain in series one or more capacities and one or more mixing or heat exchange equipment, so as to carry out the treatment at an optimum temperature and during a residence time. In a non-exhaustive manner, the mixing equipment can include tools generally used by a person skilled in the art for mixing liquids, such as agitated or recirculated containers or static mixers, but also any type of equipment allowing rapid dispersion. of the chemical treatment agent in the flow to be treated, such as axial jet mixers, rotary jet mixers, liquid jet ejectors, hydro-ejectors, pumps, filters, etc.
    Alternatively, the chemical agent can be introduced directly into the finishing column at a point located between the head and the foot of the column, lower than the tray where the column is fed, preferably at a point located between about one third and two thirds of the feed section of the finishing column.
    It is indeed necessary, for ease of operation, to limit the risk of solid formation to an area very close to the bottom of the column, and possibly to place a system making it possible to collect and easily eliminate the solid formed.
    In addition, light aldehydes being at least partially removed at the top by distillation by entering the finishing column operating under reduced pressure, the concentration of total aldehydes is lower in the part located between about one third and two thirds of the section d 'supply of the finishing column, the amount of chemical agents to be introduced is therefore lower.
    The stream 9 separated at the bottom of the finishing column is then a stream rich in heavy compounds initially contained in the feed stream 3, or formed during the reactions for removing impurities with the chemical agent.
    According to the invention, the increase in the number of separation stages between the feed stream and that making it possible to recover acrylic acid of polymer grade, leads to a very high efficiency column making it possible to completely remove the impurity protoanemonin.
    By way of comparison, in FIG. 4 is shown a distillation column with a separating wall as a finishing column, in a process for recovery of (meth) acrylic acid of polymer grade of the prior art.
    In this process, the separating wall of the finishing column is not joined with the upper part of the column. Polymer grade acrylic acid is recovered by side-drawing from the other side of the feed section.
    With this configuration, the injection of the chemical agent is carried out in the feed flow of the column, or in the feed section of the column, necessarily at a level situated above the lateral draw-off. The risk of generating solids which will accumulate in the column is significant, and it is not possible to place a solids recovery system.
    The number of separation stages resulting from the operation of this type of column does not completely eliminate the protoanemonin impurity.
    Indeed, the separation of acrylic acid with protoanemonin will depend largely on the number of separation stages available. In the case of the configuration shown in Figure 4, section 36 must perform two operations: i) guarantee the separation of the light compounds with the product of the lateral racking, which can be achieved schematically by the plates included between the upper part and the location of the lateral draw-off of part 36, ii) then separate the heavy compounds and acrylic acid between the lower part and the lateral draw-off of part 36.
    In the method according to the invention, these 2 operations can be carried out respectively by sections 35 and 36 in their entirety.
    In addition, the energy linked to the recycling flow rate at the top of this finishing column towards the dehydration column in order to recycle the light compounds and guarantee a constant quality of the glacial acrylic acid extracted by lateral withdrawal, remains a drawback in this process. of the prior art.
    The method according to the invention advantageously overcomes all of these drawbacks of the prior art.
    权利要求:
    Claims (15)
    [1" id="c-fr-0001]
    1. Process for recovering purified (meth) acrylic acid, in the absence of organic solvent, from a gaseous reaction mixture comprising (meth) acrylic acid obtained by gas phase oxidation of a precursor of (meth) acrylic acid, comprising at least the following steps:
    a) the gaseous reaction mixture is subjected to dehydration without using an azeotropic solvent in a first distillation column called the dehydration column, leading to an overhead stream at least part of which is condensed and returned to the dehydration column in the form of reflux, and to a bottom flow of which at least part is returned to reflux in the lower part of the dehydration column to form a recirculation loop;
    b) the bottom stream of the dehydration column is sent at least in part to a second distillation column called the finishing column, making it possible to separate a bottom stream containing heavy compounds, and a top stream containing light compounds, at least part of which is returned to the dehydration column;
    said process being characterized in that:
    i) the finishing column is equipped with a separating wall, the wall being contiguous with the upper dome of the column at the top and not contiguous with the bottom of the column at the bottom, thus separating the column into two sections equipped with internal distillation elements ensuring gas-liquid contact, the lower space of which communicates with the column bottom space, and the head space of which is separated into two hermetic zones, the supply of said column being effected on one side of the separating wall, and ii) a gas flow rich in light compounds and comprising water is extracted at the top of the feed section, then recycled, after condensation, at least partly in the loop recirculation at the bottom of the dehydration column, and iii) a gaseous flow of purified (meth) acrylic acid extracted in gaseous form from the finishing column at the top of the section located on the other side of the feed section , is withdrawn after condensation, part of the condensed flow being returned as liquid reflux at the top of the withdrawal section.
    [2" id="c-fr-0002]
    2. Method according to claim 1 characterized in that the precursor of (meth) acrylic acid is acrolein, obtained by oxidation of propylene or by oxideshydrogenation of propane.
    [3" id="c-fr-0003]
    3. Method according to claim 1 characterized in that the precursor of (meth) acrylic acid is methacrolein obtained by oxidation of isobutylene and / or tert-butanol or from oxideshydrogenation of butane and / or isobutane.
    [4" id="c-fr-0004]
    4. Method according to claim 1 characterized in that the precursor of (meth) acrylic acid comprises carbon of renewable origin.
    [5" id="c-fr-0005]
    5. Method according to any one of the preceding claims, characterized in that the supply of the finishing column is carried out at the head at the level of the upper plate of the supply section, and optionally, part of the gas flow which is extracted at the head of the feed section, is returned after condensation in the feed stream of the finishing column.
    [6" id="c-fr-0006]
    6. Method according to any one of claims 1 to 4 characterized in that the supply of the finishing column takes place at a point located lower than the upper plate of the supply section, and part of the flow gaseous which is extracted at the head of the feed section, is returned after condensation as liquid reflux at the head of the feed section.
    [7" id="c-fr-0007]
    7. Method according to any one of the preceding claims, characterized in that it further comprises the introduction into the finishing column, of a chemical treatment agent aimed at reducing the content of residual aldehydes.
    [8" id="c-fr-0008]
    8. Method according to claim 7 characterized in that the agent for the chemical treatment of aldehydes is chosen from:
    • amines, such as, for example, without limitation, monoethanolamine, ethylene diamine glycine, diethylenetriamine, dipropylenetriamine, ortho-, para-, and meta-phenylenediamine., • compounds of the family aniline, such as, for example, without limitation, aniline, ortho-, para-, and meta-methylaniline • compounds of the hydrazine family, such as, without limitation, hydrazine and its salts, hydrazine hydrate, hydrazine sulfate, hydrazine carboxylates, hydrazine hydrochloride, phenylhydrazine, 4-nitrophenylhydrazine, and 2,43064630 dinitrophenylhydrazine, or aminoguanidine and its salts , such as aminoguanidine hydrogen carbonate.
    • Compounds of the hydrazide family, such as, for example, without limitation, the hydrazides of carboxylic acids and their salts, such as the hydrazides of formic, acetic, propionic, butanoic, pentanoic, maleic acids and the dihydrazides of acids adipic and succinic, urea or derivatives of urea and hydrazine, such as semicarbazide or carbohydrazide and their salts;
    alone or their mixtures in all proportions.
    [9" id="c-fr-0009]
    9. Method according to claim 7 or 8 characterized in that the chemical treatment agent is introduced into the feed stream of the finishing column, preferably by means of a mixing device comprising at least one capacity ensuring efficient dispersion of the chemical agent with the feed stream.
    [10" id="c-fr-0010]
    10. Method according to claim 7 or 8 characterized in that the chemical treatment agent is introduced directly into the finishing column at a point between the head and the column bottom, lower than the plate where the column feed, preferably at a point between about one third and two thirds of the height of the feed section of the finishing column.
    [11" id="c-fr-0011]
    11. Method according to claim 7 or 8 characterized in that a lateral drawing off of a gas flow comprising (meth) acrylic acid of intermediate quality is carried out from the drawing section.
    [12" id="c-fr-0012]
    12. Method according to any one of claims 1 to 6 characterized in that the purified (meth) acrylic acid is of technical grade and comprises a mass content of water of less than 0.2%, a mass content of lower acetic acid 0.2%. a mass content of furfural less than 0.05%, a mass content of benzaldehyde less than 0.05%, and a mass content of protoanemonin less than 0.05%.
    [13" id="c-fr-0013]
    13. Method according to any one of claims 1 to 6 further comprising a complementary treatment of the purified (meth) acrylic acid by fractional crystallization, or by distillation in the presence of a compound reacting with the residual aldehydes, leading to a quality of polymer grade (meth) acrylic acid.
    [14" id="c-fr-0014]
    14. Method according to any one of claims 7 to 11 characterized in that the purified (meth) acrylic acid is of polymer grade with a weight content of (meth) acrylic acid greater than 99.5%, and comprising less preferably 2 ppm
    5 less lppm of protoanemonin, a mass content of water less than 0.1%, preferably less than 0.05%, and a mass content of acetic acid less than 0.2%, preferably less than 0.05% .
    [15" id="c-fr-0015]
    15. Process for the production of purified (meth) acrylic acid comprising
    10 minus the following steps:
    A) at least one (meth) acrylic acid precursor is subjected to gas phase oxidation to form a gaseous reaction mixture comprising (meth) acrylic acid;
    B) the gaseous reaction mixture is cooled;
    C) the cooled gaseous reaction mixture is subjected to the process for recovering (meth) acrylic acid as defined according to any one of the preceding claims.
    1/2
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    FR3064630B1|2019-09-13|
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    法律状态:
    2018-03-15| PLFP| Fee payment|Year of fee payment: 2 |
    2018-10-05| PLSC| Search report ready|Effective date: 20181005 |
    2019-03-13| PLFP| Fee payment|Year of fee payment: 3 |
    2020-03-12| PLFP| Fee payment|Year of fee payment: 4 |
    2021-03-10| PLFP| Fee payment|Year of fee payment: 5 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1752902|2017-04-04|
    FR1752902A|FR3064630B1|2017-04-04|2017-04-04|PROCESS FOR PURIFYINGACRYLIC ACID INCLUDING A SEPARATING WALL DISTILLATION COLUMN|FR1752902A| FR3064630B1|2017-04-04|2017-04-04|PROCESS FOR PURIFYINGACRYLIC ACID INCLUDING A SEPARATING WALL DISTILLATION COLUMN|
    JP2019554697A| JP2020515626A|2017-04-04|2018-04-03|Method for purifying acrylic acid including distillation column with separation wall|
    US16/499,887| US10815182B2|2017-04-04|2018-04-03|Process for purifying acrylic acid including a dividing-wall distillation column|
    CN201880020674.4A| CN110461811A|2017-04-04|2018-04-03|Purifyingacrylic acid including the destilling tower with partition wall|
    SG11201908220P| SG11201908220PA|2017-04-04|2018-04-03|Method For Purifying Acrylic Acid Including A Distillation Column With A Separating Wall|
    EP18718888.3A| EP3606903A1|2017-04-04|2018-04-03|Process for purifying acrylic acid including a dividing-wall distillation column|
    BR112019018426A| BR112019018426A2|2017-04-04|2018-04-03| acrylic acid purification process including a partition wall distillation column|
    KR1020197031516A| KR20190135018A|2017-04-04|2018-04-03|Method for Purifyingacrylic Acid Including Distillation Column with Separation Walls|
    PCT/FR2018/050826| WO2018185423A1|2017-04-04|2018-04-03|Process for purifying acrylic acid including a dividing-wall distillation column|
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