Acetic acid manufacturing method

专利摘要:
  It is a method for producing acetic acid,which includes a reaction stage, a first stage ofpurification, a second purification step and a thirdpurification step. In the reaction step, a mixture ofmaterial, including methanol, carbon monoxide, acatalyst and an iodide, is subjected to a reaction ofcarbonylation of methanol in a reactor (1) to form acidacetic. In the first stage of purification, a flow of acidcrude acetic acid, including acetic acid formed in thereaction, is subjected to distillation in a distillation column(3) to provide a first flow of acetic acid,enriched with acetic acid. In the second stage ofFor purification, the first flow of acetic acid is subjected todistillation in a distillation column (5) to provide asecond stream of acetic acid most enriched with acidacetic. In the third stage of purification, a flow of acidacetic is subjected to purification in a unit ofadditional purification (eg, a distillation column(6)), while controlling the concentration of corrosive iodine in theacetic acid flow through the unit up to 100 ppm orleast to provide a third stream of acetic acid yetmore enriched with acetic acid. The method for producingacetic acid is suitable for restricting corrosion ofacetic acid producing equipment.
公开号:BR112017022092A2
申请号:R112017022092-0
申请日:2016-09-20
公开日:2020-10-27
发明作者:Shimizu Masahiko；Masahiko Shimizu；Hirabayashi Nobuyuki；Nobuyuki HIRABAYASHI；Mizutani Yoshihisa；Yoshihisa Mizutani
申请人:Daicel Corporation；
IPC主号:

专利说明:

[0001] [0001] The present invention relates, in general, to methods for producing acetic acid. This Order claims priority to Japanese Patent Application No. 2015-192286 filed on September 29, 2015, the entire content of which is incorporated herein by reference. TECHNICAL FUNDAMENTALS
[0002] [0002] A methanol carbonylation process is known as an acetic acid synthesis process, which is suitable for the industrial production of acetic acid. With this synthesis process, raw materials methanol and carbon monoxide are reacted with each other in the presence of a predetermined catalyst to form acetic acid.
[0003] [0003] An acetic acid production plant, for use in the production of acetic acid using the methanol carbonylation process, includes two or more units, such as a reactor, an instantaneous evaporator, a low point removal component column boiling, and a dehydration column. In the acetic acid production plant, as mentioned above, acetic acid is normally produced through processes in the individual units, as follows. In the reactor, acetic acid is continuously formed from raw materials methanol and carbon monoxide, by a methanol carbonylation reaction. In the instantaneous evaporator, a reaction liquid from the reactor, where the reaction liquid contains acetic acid formed in the reactor, is subjected to a so-called instantaneous evaporation treatment, to extract crude acetic acid vapor from the reaction liquid. In the low boiling component removal column, crude acetic acid is subjected to distillation, and a stream of liquid acetic acid enriched with acetic acid is extracted from the low boiling component removal column. Distillation is performed mainly to remove low boiling components from crude acetic acid, where low boiling components have lower boiling points compared to acetic acid. In the dehydration column, oThe acetic acid flow is subjected to distillation, mainly to remove water from the acetic acid flow, and a flow of acetic acid liquid, further enriched with acetic acid, is extracted from the dehydration column.
[0004] [0004] The methanol carbonylation process can use iodide as a promoter to assist the action of a catalyst to be used. Iodine, when used, forms hydrogen iodide as a by-product in the reactor. Hydrogen iodide, with the main product of acetic acid and other substances, passes through the units in the acetic acid production plant, acts as a strong acid and causes corrosion of the acetic acid production plant. Techniques to decrease the hydrogen iodide concentration in the low boiling component removal column can usually be found in PCT International Publication Number WO 2013/137236 (PTL 1). Techniques to decrease the hydrogen iodide concentration in the dehydration column can be found, usually, in the International PCT Publication Number WO 2012/086386 (PTL 2). LIST OF QUOTES PATENT LITERATURE
[0005] [0005] PTL 1: PCT International Publication WO Number 2013/137236 PTL 2: PCT International Publication WO Number 2012/086386 SUMMARY OF THE INVENTION TECHNICAL PROBLEM
[0006] [0006] Suppose that the acetic acid production plant, which supplies hydrogen iodide as a by-product in the reactor, still includes a purification unit, such as a distillation column downstream of the dehydration column. In this case, the hydrogen iodide tends to be thickened (concentrated) in the additional purification unit, even when conventional techniques for decreasing the hydrogen iodide concentration are used in the low boiling component and / or column removing column. dehydration. The thickening of hydrogen iodide in the additional purification unit causes corrosion of the acetic acid-producing equipment in the purification unit. The present invention was made in these circumstances and aims to provide an acetic acid production method, which is suitable for restricting the corrosion of such acetic acid producing equipment. SOLUTION TO THE PROBLEM
[0007] [0007] The present invention provides a method for producing acetic acid in equipment producing acetic acid, where the equipment includes a reactor, a first distillation column, a second distillation column and an additional purification unit.
[0008] [0008] Equipment producing acetic acid, with which the method is performed, includes a reactor, a first distillation column, a second distillation column and an additional purification unit. The additional purification unit is arranged downstream of the first and second distillation columns. the equipment “can also include an instant evaporator placed between the reactor and the first distillation column.
[0009] [0009] As described above, the acetic acid production method is suitable for restricting corrosion of the additional purification unit and is therefore suitable for restricting corrosion of the acetic acid producing equipment. The acetic acid production method, which is suitable for restricting corrosion of acetic acid-producing equipment, is appropriate to eliminate or minimize the use of expensive corrosion-resistant material in the equipment, to reduce the cost of acetic acid production.
[0010] [0010] In a preferred embodiment, the additional purification unit includes a third distillation column, and the third purification step includes distillation on the third distillation column. This configuration is advantageous to offer high purity of the resulting acetic acid product.
[0011] [0011] In the embodiment, where the additional purification unit includes the third distillation column, the third purification step preferably includes providing at least one substance selected from the group consisting of methanol, methyl acetate and hydroxide potassium, to the flow of acetic acid with distillation in the third distillation column, in order to control the concentration of corrosive iodine at 100 ppm or less. Methanol, when fed, can react with hydrogen iodide in the acetic acid stream to form methyl iodide and water. Methyl acetate, when fed, can react with hydrogen iodide in the acetic acid stream to form methyl iodide and acetic acid. Potassium hydroxide, when fed, can react with hydrogen iodide in the acetic acid stream to form potassium iodide and water. The decrease in the concentration of hydrogen iodide in the acetic acid flow also tends to decrease the concentration of iodine ions in the acetic acid flow. Methanol is fed to the acetic acid flow with distillation in the third distillation column, preferably at a level equal to or less than the level, in which the acetic acid flow is introduced in the third distillation column, where the levels are defined with respect to the height direction of the third distillation column. Methyl acetate is fed to the flow of acetic acid with distillation in the third distillation column, preferably at a level equal to or less than the level, in which the flow of acetic acid is introduced into the third distillation column, where the levels are defined with respect to the height direction of the third distillation column. Potassium hydroxide is fed to the acetic acid flow with the distillation in the third distillation column, preferably at a level equal to or greater than the level, in which the acetic acid flow is introduced in the third distillation column, where the levels are defined in relation to the height direction of the third distillation column. The configuration, as described above, is advantageous for efficiently controlling the concentration of corrosive iodine in the acetic acid flow in the third distillation column at 100 ppm or less.
[0012] [0012] In the embodiment, where the additional purification unit includes the third distillation column, the third purification step preferably includes, in order to control the corrosive iodine concentration at 100 ppm or less, at least an element selected from the group consisting of the supernatant recycling part of the third distillation column for the first acetic acid stream, before being introduced into the second distillation column, and the supernatant recycling part of the third distillation column for the flow of crude acetic acid, before being introduced into the first distillation column.
[0013] [0013] Preferably, the acetic acid-producing equipment still includes a purification system. The purification system treats part of the gaseous components emanating from the equipment to form a component to be recycled for the reactor; and a component to be unloaded from the equipment. The configuration is advantageous for converting the corrosive iodines contained in gaseous components, emanating from the acetic acid producing equipment, into methyl iodide to be recycled to the reactor. In addition, the configuration is advantageous to efficiently discharge other unnecessary chemical species from the equipment.
[0014] [0014] Preferably, part of the supernatant from the third distillation column is introduced into the purification system. This configuration is usually advantageous for converting corrosive iodines contained in the supernatant of the third distillation column into methyl iodide in the purification system and for recycling the methyl iodide to the reaction system to be reused therein. In addition, the configuration is still advantageous for discharging other unnecessary chemical species from the equipment using the purification system.
[0015] [0015] Preferably, the third purification step includes feeding at least one substance selected from the group consisting of methanol, methyl acetate and potassium hydroxide to a flow of acetic acid, before being introduced into the additional purification unit in order to to control the concentration of corrosive iodine at 100 ppm or less. Methanol, when fed, can react with hydrogen iodide in the acetic acid stream to form methyl iodide and water. Methyl acetate, when fed, can react with hydrogen iodide in the acetic acid stream to form methyl iodide and acetic acid. Potassium hydroxide, when fed, can react with hydrogen iodide in the acetic acid stream to form potassium iodide and water. The decrease in the concentration of hydrogen iodide in the acetic acid flow also tends to decrease the concentration of iodine ions in the acetic acid flow. The acetic acid flow, before it is introduced into the additional purification unit, is preferably carried out so that the acetic acid flow, before being introduced into the additional purification unit, has a corrosive iodine concentration of 100 ppb or less. As used herein, the term "ppb" refers to "bulk ppb". This configuration is advantageous for efficiently controlling the concentration of corrosive iodine in the acetic acid stream in the additional purification unit at 100 ppm or less.
[0016] [0016] Preferably, the flow of acetic acid in the additional purification unit has a water concentration of 0.001 to 2% by mass. The flow of acetic acid in the additional purification unit may have a water concentration, preferably 0.001% by mass or more, more preferably 0.003% by mass or more, even more preferably, 0.005% by mass or more and, particularly preferably, 0.006% by mass or more. This is preferred from the point of view of allowing a passive film of a constitutional material of inner wall to be properly formed on the surface of the inner wall of the unit, by purifying it in the unit, in order to thus restrict corrosion of the inner wall. The flow of acetic acid in the additional purification unit may have a water concentration, preferably 2% by weight or less, more preferably 1% by weight or less and even more preferably 0.5 Bulk% or less. This is preferred from the point of view of restricting the ionization (electrolytic dissociation) of hydrogen iodide and acetic acid in the liquid to be treated, through purification in the unit, in order to thus restrict the corrosion of the internal wall of the unit. The concentration of water in the acetic acid stream in the additional purification unit is preferably adequately controlled and managed, normally, through the points of view above. To control the water concentration in the acetic acid stream, in the additional purification unit, water can be fed to an acetic acid stream, before being introduced into the additional purification unit and / or to the acetic acid stream, by purification in the additional purification unit.
[0017] [0017] Purification in the additional purification unit can be carried out at a temperature, preferably of 160º C or less, more preferably of 150º C or less, even more preferably of 140º C or less and, even more preferably, 120º C or less. This configuration is advantageous for reducing the corrosion rate caused by iodine, which proceeds in the additional purification unit. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] [0018] The single figure (Fig. 1) schematically illustrates the general arrangement of acetic acid-producing equipment, with which the method of producing acetic acid, according to an embodiment of the present invention, is performed. DESCRIPTION OF METHODS
[0019] [0019] Fig. 1 schematically illustrates the general arrangement of acetic acid-producing equipment X, with which the method of producing acetic acid, according to an embodiment of the present invention, is performed. equipment producing acetic acid X includes a reactor 1, an evaporator 2, a distillation column 3, a decanter 4, a distillation column 5, a distillation column 6, an ion exchange resin column 7, an purification 8, capacitors la, 2a, 3a, 5a and 6a, a heat exchanger 2B, and lines 11 to 48. The acetic acid-producing equipment X is configured so as to continuously produce acetic acid. The acetic acid production method, according to the embodiment, includes a reaction step, an instant evaporation step, a first distillation step, a second distillation step, a third distillation step, and a adsorption / removal respectively carried out in reactor l1, evaporator 2, distillation column 3, distillation column 5, distillation column 6, and ion exchange resin column 7, as illustrated below.
[0020] [0020] Reactor 1 is a unit, with which the reaction step is carried out. The reaction step is the step of carrying out a reaction (methanol carbonylation reaction) represented by the Reaction Formula (1) to form acetic acid continuously. A reaction mixture, which is continuously stirred, usually by a stirrer, is present in reactor 1 during the constant operation of the acetic acid X-producing equipment. The reaction mixture includes the raw materials methanol and carbon monoxide, a catalyst, a promoter, water, target acetic acid to be produced, and various by-products. In the reaction mixture, a liquid phase and a gas phase (vapor phase) are in equilibrium. Reaction Formula (1) is expressed as follows: CH; OH + CO - CH, COOH + - (1)
[0021] [0021] The raw materials in the reaction mixture are liquid methanol and gaseous carbon monoxide. Methanol is fed, continuously, from a methanol reservoir (not shown) through line 11 to reactor 1 at a predetermined flow rate. the carbon monoxide is fed continuously from a carbon monoxide reservoir (not shown) through line 12 to reactor 1, at a predetermined flow rate.
[0022] [0022] The catalyst in the reaction mixture plays the role of promoting the methanol carbonylation reaction. The catalyst can normally be selected from rhodium catalysts and iridium catalysts. A non-limiting example of rhodium catalysts is a rhodium complex represented by the chemical formula [Rh (CO); I7]. A non-limiting example of iridium catalysts is an iridium complex represented by the chemical formula [Ir (CO): I2]. The reaction mixture can have a catalyst concentration, in general, from 200 to 5000 ppm of the entire liquid phase in the reaction mixture.
[0023] [0023] The promoter is an iodide to assist the activity of the catalyst. Non-limiting examples of iodide, such as the promoter, include methyl iodide and an ionic iodide. Methyl iodide can offer the action of promoting catalyst catalysis. The reaction mixture can have a methyl iodide concentration of normally 1 to 20% by weight of the entire liquid phase in the reaction mixture. Ionic iodide is an iodide, which forms an iodine ion in the reaction liquid. Ionic iodide can offer the actions of stabilizing the catalyst and restricting side reactions. Non-limiting examples of ionic iodide include lithium iodide, sodium iodide and potassium iodide. The reaction mixture can have an iodide ion concentration, typically 1 to 25% by mass of the entire liquid phase in the reaction mixture.
[0024] [0024] Water in the reaction mixture is a component, which is necessary for the formation of acetic acid in the reaction mechanism of the methanol carbonylation reaction, and is necessary for the dissolution of water-soluble components in the reaction system. The reaction mixture can have a water concentration, normally from 0.1 to 15% by mass of the entire liquid phase in the reaction mixture. The water concentration is preferably 15% by weight or less to save the energy required to remove water in the acetic acid purification process, in order to offer greater efficiency in the production of acetic acid. To control the water concentration, water can be fed continuously to reactor 1 at a predetermined flow rate.
[0025] [0025] The acetic acid in the reaction mixture includes acetic acid previously charged in reactor 1 before the operation of the acetic acid-producing equipment X; and acetic acid formed as a major product of the methanol carbonylation reaction. Acetic acid can act as a solvent in the reaction system. The reaction mixture can have a concentration of acetic acid, usually 50 to 90% by weight and, preferably, 60 to 80% by weight, of the entire liquid phase in the reaction mixture.
[0026] [0026] A non-limiting example of the main by-products in the reaction mixture is methyl acetate. Methyl acetate can be formed by the reaction between acetic acid and methanol. The reaction mixture can have a concentration of methyl acetate, usually 0.1 to 30% by weight of the entire liquid phase in the reaction mixture. Non-limiting examples of the by-products in the reaction mixture also include hydrogen iodide. Hydrogen iodide is inevitably formed in the reaction mechanism of the methanol carbonylation reaction when the catalyst and / or promoter, as above, is used. The reaction mixture can have a hydrogen iodide concentration, typically 0.01 to 2% by mass of the entire liquid phase in the reaction mixture. Non-limiting examples of by-products also include hydrogen, methane, carbon dioxide, acetaldehyde, propionic acid and alkyl iodides, such as hexyl iodide and decyl iodide.
[0027] [0027] The reaction conditions in reactor 1, housing the above reaction mixture, can be defined normally, as follows. The reaction temperature can normally be 150º C to 250º C; the reaction pressure, as a total pressure, can normally be from 2.0 to 3.5 MPa (absolute pressure); and the partial pressure of carbon monoxide can normally be from 0.5 to 1.8 MPa (absolute pressure) and, preferably, from 0.8 to 1.5 MPa (absolute pressure).
[0028] [0028] In reactor 1, during the operation of the equipment, several components of the gas phase tend to be emanated or formed “continuously with the continuous formation of acetic acid in order to increase the total volume of vapors. Vapors in reactor 1 typically include carbon monoxide, hydrogen, methane, carbon dioxide, acetic acid, methyl acetate, methyl iodide, hydrogen iodide, acetaldehyde and water. Vapors can be extracted from reactor 1 via line 13. The internal pressure of reactor 1 can be controlled by regulating the amount of vapors to be extracted. For example, the internal pressure of the l1 reactor can be kept constant. Vapors extracted from reactor 1 are introduced into capacitor la.
[0029] [0029] The condenser there cools and partially condenses the vapors in reactor 1, to separate the vapors into condensed components and gaseous components. Condensed components typically include acetic acid, methyl acetate, methyl iodide, acetaldehyde and water, and are introduced and recycled into condenser la through line 14 inside reactor 1. Gaseous components typically include carbon monoxide, hydrogen, methane and carbon dioxide, and are fed from condenser la, through line 15, to the purification system 8. The gaseous components of condenser la are separated in the purification system 8, from which useful components (for example, carbon monoxide ) are recovered. The separation and recovery, in the embodiment, are carried out according to a wet process, using an absorbent liquid (absorbent) to collect useful components from the gaseous components. Separation and recovery can also be performed using pressure variation adsorption. The separated and recovered useful components are recycled, introducing them from the purification system 8, through a recycling line (not shown), in reactor 1. The treatment in the purification system 8 and the subsequent recycling for reactor l1, as mentioned above, can be applied to gaseous components mentioned below, fed from other condensers to the purification system 8.
[0030] [0030] Acetic acid is continuously formed in reactor 1 during the operation of the equipment, as described above. The reaction mixture containing acetic acid is continuously extracted from reactor 1 at a predetermined flow rate and fed, through line 16, into the subsequent evaporator (downstream) 2.
[0031] [0031] Evaporator 2 is a unit, with which the instant evaporation step is performed. The instant evaporation step is the step of partially evaporating the reaction mixture to separate the mixture into vapors and residual liquid components, where the reaction mixture is continuously introduced into the evaporator 2. Evaporation can be carried out by decompressing the reaction mixture without heating, or with heating. In the instant evaporation step, the temperature of the steam can normally be from 100º C to 260º C; the temperature of the residual liquid component can normally be 80º C and 200º C; and the internal pressure of the evaporator can normally be from 50 to 1000 kPa (absolute pressure). The ratio (weight ratio) of the vapors to the residual liquid components, which are separated from each other in the instant evaporation step, is usually from 10:90 to 50:50. The vapors formed in the step usually include acetic acid, methyl acetate, methyl iodide, water, hydrogen iodide, methanol, acetaldehyde and propionic acid, and are continuously removed from evaporator 2 to line 17. A portion of the vapors removed from the evaporator 2 is continuously introduced into condenser 2a, and another part (or the remainder) of the vapors is continuously introduced, as a stream of crude acetic acid, into the subsequent distillation column 3. The stream of crude acetic acid may have a concentration of acetic acid , typically 87 to 99% by weight. The residual liquid components formed in the step include the catalyst and the promoter contained in the reaction mixture; and acetic acid, methyl acetate, methyl iodide, water and other substances, which remain without volatilization in the stage. The residual liquid components are introduced continuously from the evaporator 2, through line 18, into the heat exchanger 2b.
[0032] [0032] Condenser 2a cools and partially condenses the vapors of the evaporator 2 to separate the vapors into condensed components and gaseous components. Condensed components typically include acetic acid, methanol, methyl acetate, methyl iodide, acetaldehyde and water, and are introduced and recycled from capacitor 2a, via lines 19 and 20, into reactor 1. The gaseous components normally include carbon monoxide and hydrogen, and are fed from capacitor 2a, through lines 21 and 15, to the purification system 8. The reaction of formation of acetic acid in the reaction step is an exothermic reaction. A portion of the heat accumulated in the reaction mixture is transferred to the vapors obtained from the reaction mixture in the instant evaporation step. the condensed components formed by cooling the vapors in condenser 2a are recycled to reactor 1. That is, the acetic acid X-producing equipment is capable of efficiently removing the heat generated in the methanol carbonylation reaction by operating the capacitor 2a.
[0033] [0033] The heat exchanger 2b cools the residual liquid components of the evaporator 2. The refrigerated residual liquid components are continuously introduced and recycled from the heat exchanger 2b, through lines 22 and 20, in the reactor 1.
[0034] [0034] The distillation column 3 is a unit, with which the first distillation stage is carried out. The distillation column 3, in the embodiment, is positioned as a so-called low-boiling component removal column. The first distillation step is the step of subjecting the vapors to distillation to purify the acetic acid in the vapors, where the vapors are continuously introduced into the distillation column 3. The first distillation step normally corresponds to the first purification step in the present invention. The distillation column 3 can normally be selected from the grinding columns, such as plate columns and filling columns. The distillation column 3, when it is a plate column, can normally contain from 5 to 50 theoretical plates and can have a reflux ratio normally from 0.5 to 3000, according to the number of theoretical plates. Inside the distillation column 3 during the first distillation step, the pressure at the top of the column can normally be set from 80 to 160 kPa (gauge pressure), and the bottom pressure can normally be set at a pressure higher than the pressure in the top of the column, which is 85 to 180 kPa (gauge pressure). Inside the distillation column 3 during the first distillation step, the temperature at the top of the column can normally be set at a temperature, which is lower than the boiling temperature of acetic acid, at the pressure set at the top of the column, and which is from 90ºC to 130ºC; and the bottom temperature can normally be set at a temperature, which is equal to or greater than the boiling point of acetic acid, at the set bottom pressure, and which is from 120º C to 160º C.
[0035] [0035] Within the distillation column 3, the flow of crude acetic acid (vapor) from the evaporator 2 is introduced continuously. In the distillation column 3, as above, vapors are continuously extracted as a supernatant flow from the top of the column to line 23; a bottom liquid is drawn continuously off the bottom of the column into line 24; and a first flow of acetic acid (liquid), as a side flow, is continuously extracted from the distillation column 3, at a height level between the top of the column and the bottom part of the column, for line 25.
[0036] [0036] Vapors extracted from the top of the column of the distillation column 3 are enriched with components with low boiling point, compared to the liquid from the bottom part of the distillation column 3, where components with low boiling point have points lower boiling points compared to acetic acid. Vapors usually include methyl acetate, methyl iodide, hydrogen iodide, acetaldehyde, methanol and water. Vapors also include acetic acid. Vapors, as above, are introduced continuously through line 23 into capacitor 3a.
[0037] [0037] Condenser 3a cools and partially condenses the vapors of the distillation column 3 to separate the vapors into condensed components and gaseous components. Condensed components typically include methyl acetate, methyl iodide, hydrogen iodide, acetaldehyde, water and acetic acid, and are introduced continuously from condenser 3a, through line 26, into the decanter 4. The “condensed components introduced into the decanter 4 are separated into an aqueous phase and an organic phase.
[0038] [0038] The bottom liquid extracted from the bottom part of the distillation column 3 is enriched with components with a high boiling point, compared to the supernatant flow from the distillation column 3, where components with a high boiling point have points higher boiling points compared to acetic acid. The bottom liquid usually includes propionic acid and the catalyst and promoter, when entrained. The bottom liquid also includes, for example, methyl iodide, acetic acid, methyl acetate and water. In the embodiment, a part of the bottom liquid, as above, is continuously introduced and recycled, through line 24, in the evaporator 2, and another part (or remaining part) of the bottom liquid is continuously introduced and recycled, through the lines. lines 24 and 20, in reactor 1.
[0039] [0039] the first flow of acetic acid, extracted continuously, as a side flow, from the distillation column 3, is enriched with acetic acid, in comparison with the flow of crude acetic acid continuously introduced in the distillation column 3. Specifically , the first acetic acid stream has a higher acetic acid concentration than the acetic acid concentration in the crude acetic acid stream. The concentration of acetic acid in the first acetic acid stream can normally be 99 to 99.9% by mass, as long as it is greater than the concentration of acetic acid in the crude acetic acid stream. The first stream of acetic acid also includes other components, such as methyl acetate, methyl iodide, water and hydrogen iodide, in addition to acetic acid. In the embodiment, the first flow of acetic acid is extracted from the distillation column 3 at a level below the level, in which the flow of crude acetic acid is introduced into the distillation column 3, where the levels are defined in relation to the direction in height of the distillation column 3. The first flow of acetic acid from the distillation column 3 is introduced, via line 25, into the subsequent distillation column 5, continuously, at a predetermined flow rate.
[0040] [0040] The distillation column 5 is a unit, with which the second distillation stage is carried out. The distillation column 5, in the embodiment, is positioned as a so-called dehydration column. The second stage of distillation is the stage of subjecting the first flow of acetic acid to distillation, to further purify the acetic acid, where the first flow of acetic acid is continuously introduced into the distillation column 5. The second distillation stage normally corresponds to the second purification step in the present invention. The distillation column 5 can normally be selected from grinding columns, such as plate columns and filling columns. The distillation column 5, when it is a column of plates, can normally have 5 to 50 theoretical plates and can have a reflux ratio normally from 0.5 to 3000, according to the number of theoretical plates. Inside the distillation column 5, during the second distillation stage, the pressure at the top of the column can normally be set from 150 to 250 kPa (gauge pressure), and the bottom pressure can normally be set at a pressure higher than the pressure at the top of the column, which is 160 to 290 kPa (gauge pressure). Inside the distillation column 5 during the second distillation step, the temperature at the top of the column can normally be set at a temperature, which is higher than the boiling point of water and lower than the boiling point of acid acetic to the pressure defined at the top of the column, which is 130ºC to 155ºC; and the background temperature can normally be set at a temperature, which is equal to or greater than the boiling point of acetic acid at the defined background pressure, and which is 150 ° C to 175 ° C.
[0041] [0041] Within the distillation column 5, the first flow of acetic acid (liquid) is continuously introduced from the distillation column 3. In the distillation column 5, as above, vapors, such as a supernatant flow, are continuously extracted from the top of the column to row 30; and a bottom liquid is continuously drawn from the bottom of the column to line 31. Also in the distillation column 5, a lateral flow (liquid or gas) can be continuously drawn into line 32 at a height level between the top of the column and the bottom part of the column.
[0042] [0042] Vapors extracted from the top of the distillation column are enriched with components with a low boiling point, compared to the liquid at the bottom of the distillation column 5, where components with a low boiling point have more boiling points. compared to acetic acid. Thus, vapors normally include acetaldehyde, methyl acetate, methyl iodide, hydrogen iodide and water. Vapors are introduced continuously, via line 30, into condenser 5a.
[0043] [0043] The condenser 5a cools and partially condenses the vapors of the distillation column 5 to separate the vapors into condensed components and gaseous components. Condensed components typically include water and acetic acid. A portion of the condensed components is refluxed continuously from the condenser 5a, through line 33, to the distillation column 5; and another part (or the rest) of the condensed components is continuously introduced and recycled from the condenser 5a, through lines 33 and 34, in the reactor 1. This configuration allows the equipment producing acetic acid X to efficiently remove the heat in the condenser 5a. The gaseous components separated in condenser 5a include carbon monoxide, hydrogen, carbon dioxide, methane, nitrogen, hydrogen iodide and any other substances, and are fed from condenser 5a, through lines 35 and 15, to the purification system 8. Hydrogen iodide in the gaseous components entering the purification system 8 is adsorbed by the absorbent liquid in the purification system 8 and reacts with methanol or methyl acetate in the absorbent liquid to form methyl iodide. Such useful liquid-containing components, such as methyl iodide, are introduced or recycled from the purification system 8, via the recycling line (not shown), in reactor 1, to be reused.
[0044] [0044] The bottom liquid extracted from the bottom part of the distillation column 5 is enriched with components with a high boiling point, compared to the supernatant flow from the distillation column 5, where the components with a high boiling point have points higher boiling points compared to acetic acid. The bottom liquid usually includes propionic acid and the catalyst and / or promoter, as entrained. The bottom liquid also includes acetic acid. The bottom liquid, as above, is fed, via line 31, to line 32, to form a second flow of acetic acid and is continuously introduced into the subsequent distillation column 6. We will assume that the side flow is continuously extracted from the distillation column 5 for row
[0045] [0045] The second stream of acetic acid is enriched with acetic acid, compared to the first stream of acetic acid continuously introduced into the distillation column 5. Specifically, the second stream of acetic acid has a higher concentration of acetic acid than the acetic acid concentration in the first acetic acid stream. The concentration of acetic acid in the second acetic acid stream can normally be 99.1 to 99.99% by mass, as long as it is greater than the concentration of acetic acid in the first acetic acid stream. The second stream of acetic acid also includes other components, such as methyl acetate, methyl iodide, water and hydrogen iodide, in addition to acetic acid. In the embodiment, the lateral flow is extracted from the distillation column 5 at a level below the level, in which the first flow of acetic acid is introduced in the distillation column 5, where the levels are defined in relation to the height direction of the distillation column 5.
[0046] [0046] In equipment producing acetic acid X, at least one substance selected from the group consisting of methanol, methyl acetate and potassium hydroxide, can be fed or added to the first flow of acetic acid, before being introduced, through the line 25, in the distillation column 5, where at least one substance is fed or added via line 36, which is a supply line coupled to line 25. This configuration is for controlling the concentration of corrosive iodine in the second acetic acid stream from the distillation column 5, at 100 ppb or less.
[0047] [0047] Feeding methanol to the first acetic acid stream tends to decrease hydrogen iodide in the first acetic acid stream. Specifically, when methanol is fed, the hydrogen iodide concentration in the first acetic acid stream can be reduced, so that two chemical reactions represented by Reaction Formula (2) in the first acetic acid stream reach equilibrium, where the two chemical reactions are a reaction between methanol and hydrogen iodide to form methyl iodide and water, and a reverse reaction. The decrease in the concentration of hydrogen iodide in the first acetic acid stream also tends to decrease the concentration of iodine ions in the first acetic acid stream. Reaction Formula (2) is expressed as follows: CH; OH + HI = CH, I + H, O --- (2)
[0048] [0048] The feeding of methyl acetate to the first flow of acetic acid tends to decrease hydrogen iodide in the first flow of acetic acid. Specifically, when methyl acetate is fed, the concentration of hydrogen iodide in the first acetic acid stream can be reduced, so that two chemical reactions represented by Reaction Formula (3) reach equilibrium, where the two chemical reactions are a reaction between methyl acetate and hydrogen iodide to form methyl iodide and acetic acid, and a reverse reaction. Reaction Formula (3) is expressed as follows: CH3; COOCH; + HI == CH, I + CH, COOH --- G)
[0049] [0049] Feeding potassium hydroxide to the first acetic acid stream tends to decrease hydrogen iodide in the first acetic acid stream. Specifically, when potassium hydroxide is fed, the concentration of hydrogen iodide in the first flow of acetic acid can be reduced, so that two chemical reactions represented by Reaction Formula (4) reach equilibrium, where the two chemical reactions are a reaction between potassium hydroxide and hydrogen iodide to form potassium iodide and water, and such a reverse reaction. The chemical equilibrium is now well to the right in Reaction Formula (4). Reaction Formula (4) is expressed as follows: KOH + HI = & KI + H, O --- (4)
[0050] [0050] The action of feeding or adding to the first flow of acetic acid, before it is introduced into the distillation column 5, as described above, is preferable to decrease the concentration of hydrogen iodide in the first flow of acetic acid in the distillation column 3, in order to control the corrosive iodine concentration of the second flow of acetic acid from the distillation column 5 to 100 ppb or less.
[0051] [0051] In the embodiment, at least one substance selected from the group consisting of methanol, methyl acetate and potassium hydroxide can be fed or added to the first flow of acetic acid with distillation in the distillation column 5, where at least one substance is fed or added via line 37, which is a supply line attached to the distillation column 5. This configuration is for controlling the corrosive iodine concentration of the second flow of acetic acid from the distillation column 5 to 100 ppb or less . The amount of at least one substance to be added can be determined normally, based on the analysis of the chemical composition of a sample, sampled from the first flow of acetic acid passing through line 25. Feeding methanol to the first flow of acetic acid with distillation tends to decrease hydrogen iodide in the first flow of acetic acid. Specifically, the feed acts, as described above with reference to the Reaction Formula (2). Feeding methyl acetate to the first acetic acid stream with distillation tends to decrease hydrogen iodide in the first acetic acid stream. Specifically, the feed acts, as described above with reference to the Reaction Formula (3). Feeding potassium hydroxide to the first acetic acid stream with distillation tends to decrease hydrogen iodide in the first acetic acid stream. Specifically, the feed acts, as described above with reference to the Reaction Formula (4). The decrease in the concentration of hydrogen iodide in the first acetic acid flow with distillation in the distillation column 5 also tends to decrease the iodine ion concentration in the first acetic acid flow.
[0052] [0052] The levels of methanol and methyl acetate to be fed to the first flow of acetic acid with the distillation in the distillation column 5 are preferably equal to or less than the level at which the first flow of acetic acid is introduced into the distillation column 5 (the level, at which line 25 is coupled to the distillation column 5), where the levels are defined in relation to the height direction of the distillation column 5. Methanol and methyl acetate have lower boiling points , compared to acetic acid and thus tend to migrate to, and thicken, in the upper portion of the distillation column 5 during distillation. Therefore, methanol and methyl acetate are preferably introduced into the distillation column 5 at levels equal to or less than the level at which the first flow of acetic acid is introduced, in order to ensure the frequency of contact of the substance with hydrogen iodide, in order to efficiently decrease the hydrogen iodide concentration. In contrast, the level of potassium hydroxide to be fed to the first flow of acetic acid with distillation in the distillation column 5 is preferably equal to or greater than the level at which the first flow of acetic acid is introduced into the column of distillation. distillation 5, where the levels are defined in relation to the height direction of the distillation column 5. Potassium hydroxide has a higher boiling point compared to acetic acid and thus tends to migrate to, and to be thickened in, a lower part of the distillation column 5 during distillation. Potassium hydroxide, therefore, is preferably introduced into the distillation column 5 at a level equal to or higher than the level, at which the first flow of acetic acid is introduced, in order to ensure the frequency of contact of the substance with hydrogen iodide, in order to efficiently decrease the concentration of hydrogen iodide.
[0053] [0053] The addition action to the first flow of acetic acid in the distillation column 5, as described above, is preferable for controlling the concentration of corrosive iodine in the second flow of acetic acid in the distillation column 5 to 100 ppb or less. In addition, the addition action contributes to a decrease in the abundance of hydrogen iodide in the distillation column 5 during the distillation of the first flow of acetic acid, and normally contributes to restricting the thickening of hydrogen iodide and, in turn, to restriction of thickening of corrosive iodine at the top of the column. Controlling the concentration of corrosive iodine in the distillation column 5 is advantageous to restrict corrosion in the distillation column 5.
[0054] [0054] The distillation column 6 is an additional purification unit, with which the third distillation stage is performed, and is positioned, in the embodiment, as a so-called component removal column with a high boiling point.
[0055] [0055] Within the distillation column 6, the second flow of acetic acid (liquid) is continuously introduced from the distillation column 5. In the distillation column 6, as above, vapors, such as a supernatant flow, are continuously extracted from the top of the column to row 38; a bottom liquid is drawn continuously from the bottom of the column to line 39; and a lateral flow (liquid or gas) is continuously drawn into line 40 at a height level between the top of the column and the bottom part of the distillation column 6. With respect to the height direction of the distillation column 6, the line 40 can be coupled to the distillation column 6 at a level less than or equal to the level, where line 32 is coupled to the distillation column 6, instead of the level indicated in the figure.
[0056] [0056] The vapors extracted at the top of the distillation column 6 are enriched with components with a low boiling point, compared to the liquid at the bottom of the distillation column 6, where the components with a low boiling point have boiling points. lower compared to acetic acid. Vapors usually include acetaldehyde, methyl acetate, methyl iodide, water and hydrogen iodide. Vapors also include acetic acid. Vapors, as above, are introduced continuously through line 38 into condenser 6a.
[0057] [0057] Condenser 6a cools and partially condenses the vapors of the distillation column 6 to separate the vapors into condensed components and gaseous components. Condensed components typically include acetic acid and hydrogen iodide. At least a part of the condensed components is continuously refluxed, from the condenser 6a, through line 41, to the distillation column 6. A part (distillate) of the condensed components can be recycled from the condenser 6a, through the lines 41 and 42, for the first flow of acetic acid in line 25, before being introduced into the distillation column 5. In addition, or instead, a part (distillate) of the condensed components can be recycled from condenser 6a, through lines 41 and 42, for the flow of crude acetic acid in line 17, before being introduced into the distillation column 3. A portion of the condenser distillate 6a can be fed into the purification system 8 and used as a liquid absorbent in the system. In the purification system 8, hydrogen iodide and other gaseous components are separated from the distillate and are discharged from the equipment; and a liquid containing useful components is introduced or recycled from the purification system 8, via the recycling line (not shown), in reactor 1, to be reused. useful components include acetic acid and methyl iodide. Methyl iodide includes methyl iodide formed by reacting hydrogen iodide with methanol or methyl acetate in the absorbent liquid. In addition, a portion of the condenser distillate 6a can be introduced, via a line (not shown), into various pumps (not shown) operated on the equipment, and used as a sealant (sealing liquid) for the pumps. In addition, a portion of the condenser distillate 6a can be extracted constantly or not from the equipment, as needed. The extraction is performed through an extraction line connected to line 41. Suppose that a part (distillate) of the condensed components is removed from the distillation system in the distillation column
[0058] [0058] The bottom liquid extracted from the bottom part of the distillation column 6, through line 39, is enriched with components with a high boiling point, in comparison with the supernatant flow of the distillation column 6, where the components with high boiling points have higher boiling points compared to acetic acid. The bottom liquid usually includes propionic acid. The bottom liquid extracted from the bottom part of the distillation column 6, through line 39, also includes corrosive metals, which are formed in, and released from, the internal wall of members or components that make up the acetic acid-producing equipment X; and compounds between iodine and corrosive metals, where iodine is obtained from corrosive iodines. The bottom liquid, as above, is discharged from equipment producing acetic acid X, in the embodiment. Instead, it is also acceptable for some of the bottom liquid to be discharged from the equipment and another part (or the rest) of the bottom liquid to be recycled to line 25.
[0059] [0059] The side flow continuously extracted from the distillation column 6 to line 40 is continuously introduced, as a third flow of acetic acid, into the subsequent ion exchange resin column 7. The third flow of acetic acid is enriched with acetic acid , compared to the second acetic acid stream continuously introduced into the distillation column 6. Specifically, the third acetic acid stream has a higher acetic acid concentration than the acetic acid concentration in the second acetic acid stream. The third acetic acid stream can have a concentration of acetic acid typically from 99.8 to 99.999% by mass, as long as it is greater than the concentration of acetic acid in the second acetic acid stream. In the embodiment, the lateral flow is extracted from the distillation column
[0060] [0060] In the embodiment, at least one substance selected from the group consisting of methanol, methyl acetate and potassium hydroxide can be fed or added to the second flow of acetic acid, before being introduced, via line 32, in the column distillation 6, where at least one substance is fed or added, via line 44, which is a supply line coupled to line 32. This is done with the aim of controlling the concentration of corrosive iodine in the second flow of acetic acid in the distillation column 6 to 100 ppm or less. The amount of at least one substance to be added can be determined normally, based on the analysis of the chemical composition of a sample sampled from the second acetic acid stream passing through line 32. Feeding methanol to the acetic acid stream tends to decrease iodide of hydrogen in the second acetic acid stream. Specifically, the feed acts, as described above, on the methanol feed for the first flow of acetic acid with reference to the Reaction Formula (2). Feeding methyl acetate to the second acetic acid stream tends to decrease hydrogen iodide in the second acetic acid stream. Specifically, the feed acts, as described above, on the methyl acetate feed for the first acetic acid stream with reference to the Reaction Formula (3). Feeding potassium hydroxide to the second acetic acid stream tends to decrease hydrogen iodide in the second acetic acid stream. Specifically, the feed acts, as described above, on the feed of potassium hydroxide to the first flow of acetic acid with reference to the Reaction Formula (4). The decrease in hydrogen iodide, that is, decrease in the concentration of hydrogen iodide, in the second flow of acetic acid also tends to decrease the concentration of the iodine ion in the second flow of acetic acid.
[0061] [0061] The action of feeding or adding to the second flow of acetic acid, before being introduced into the distillation column 6, as described above, can control the concentration of corrosive iodine in the second flow of acetic acid, before being introduced into the column distillation 6, usually at 100 ppb or less. The addition action controls the concentration of corrosive iodine in the second stream of acetic acid, preferably at 10 ppb or less. The addition action, as above, is preferable to decrease the thickening of corrosive iodines in the second flow of acetic acid in the distillation column 6, in order to control the concentration of corrosive iodine in the second flow of acetic acid in the distillation column 6 to 100 ppm or less. The addition action, as above, is preferred, because the action can directly directly control the concentration of corrosive iodine in the second flow of acetic acid introduced in the distillation column 6.
[0062] [0062] In the embodiment, at least one substance selected from the group consisting of methanol, methyl acetate and potassium hydroxide can be fed Or added to the second flow of acetic acid with distillation in the distillation column 6, where at least one substance is fed or added via line 45, which is a supply line coupled to the distillation column 6. This is done, with the aim of controlling the concentration of corrosive iodine in the second flow of acetic acid, in the distillation column 6, at 100 ppm or less.
[0063] [0063] The levels, at which methanol and methyl acetate are fed to the second stream of acetic acid with distillation in the distillation column 6, are each preferably equal to or less than the level at which the second stream of acetic acid is introduced into the distillation column 6 (the level, at which line 32 is coupled to the distillation column 6), where the levels are defined in relation to the height direction of the distillation column 6. Methanol and methyl acetate they have lower boiling points compared to acetic acid and thus tend to migrate to, and be thickened in, an upper portion in the distillation column 6 during distillation. Methanol and methyl acetate are therefore introduced into the distillation column 6, preferably at levels equal to or less than the level, at which the second flow of acetic acid is introduced, where the levels are defined in relation to the height direction. , from the point of view of ensuring the frequency of contact of the substance with hydrogen iodide, in order to efficiently decrease the concentration of hydrogen iodide. The levels, at which methanol and methyl acetate are fed to the second flow of acetic acid with distillation in the distillation column 6, are preferably higher than the level of line 40. This is preferred from the point of view of greater purity the third flow of acetic acid extracted to line 40 and, in turn, for greater purity of the acetic acid product. In contrast, the level at which potassium hydroxide is fed to the second stream of acetic acid with distillation in the distillation column 6 is preferably equal to or higher than the level at which the second stream of acetic acid is introduced into the distillation column 6, where the levels are defined in relation to the height direction of the distillation column 6. Potassium hydroxide has a higher boiling point, compared to acetic acid, and tends to migrate to, and be thickened in, a bottom part in the distillation column 6 during distillation. Potassium hydroxide is therefore preferably introduced into the distillation column 6 at a level equal to or higher than the level, at which the second flow of acetic acid is introduced, in order to ensure the frequency of contact of the substance with hydrogen iodide in order to efficiently decrease the concentration of hydrogen iodide. The potassium hydroxide is fed to the second flow of acetic acid with distillation in the distillation column 6, preferably below the level of line 40. This is preferred, from the point of view of greater purity of the third flow of acetic acid extracted for line 40 and, in turn, for greater purity of the acetic acid product.
[0064] [0064] Each of the addition actions described above for the second flow of acetic acid in the distillation column 6 is preferred for controlling the concentration of corrosive iodine in the second flow of acetic acid, in the distillation column 6, at 100 ppm or any less.
[0065] [0065] In equipment producing acetic acid X, water can be fed or added to the second flow of acetic acid, before being introduced through line 32 in the distillation column 6, where water is fed or added through line 46, which is a supply line coupled to line 32, in order to control the water concentration in the second flow of acetic acid, in the distillation column 6,
[0066] [0066] In equipment producing acetic acid X, a part of the supernatant from the distillation column 6 can be recycled through lines 41 and 42 to the first flow of acetic acid, before being introduced into the distillation column 5, in order to control the concentration of corrosive iodine in the second flow of acetic acid, in the distillation column 6, at 100 ppm or less. In this configuration of the supernatant of the distillation column 6, corrosive iodines contained in the liquid stream to be recycled to the first acetic acid stream will again pass through the second distillation step in the distillation column 5 and the third distillation step in the distillation column 6 Specifically, corrosive iodines contained in the liquid stream to be recycled to the first acetic acid stream will again go through a purification path centered on the distillation column 5 and a purification path centered on the distillation column
[0067] [0067] The ion exchange resin column 7 is an additional purification unit, with which the adsorption / removal step is performed. The adsorption / removal step is the step of removing, through adsorption, mainly alkyl iodides (such as hexyl iodide and decyl iodide) from the third flow of acetic acid, to further purify the acetic acid, where the third flow of acetic acid is continuously introduced into the ion exchange resin column
[0068] [0068] Within the ion exchange resin column 7, the third flow of acetic acid (liquid) from the distillation column 6 is introduced continuously. In the ion exchange resin column 7, as above, a fourth flow of acetic acid is continuously drawn from a final bottom part of the column to line 48. The fourth flow of acetic acid has a higher concentration of acetic acid than the acetic acid concentration in the third acetic acid stream. Specifically, the fourth flow of acetic acid is enriched with acetic acid, compared to the third flow of acetic acid continuously introduced into the ion exchange resin column 7. The concentration of acetic acid in the fourth flow of acetic acid is normally of 99.9 to 99.999% by weight, or more, provided it is greater than the concentration of acetic acid in the third acetic acid stream. In the production method, the fourth stream of acetic acid can be stored in a product tank (not shown).
[0069] [0069] In equipment producing acetic acid X, water can be fed or added to the third flow of acetic acid, before being introduced, via line 40, into the ion exchange resin column 7, where the water is fed or added through line 47, which is a supply line coupled to line 40. This is done, with the objective of controlling the water concentration of the third flow of acetic acid passing through the ion exchange resin column 7, from 0.001 to 2 % in large scale. The amount of water to be added can be determined normally, based on the analysis of the chemical composition of a sample, sampled from the third flow of acetic acid passing through line 40. The third flow of acetic acid in the ion exchange resin column 7 it has a water concentration, preferably 0.001% by mass or more, more preferably 0.002% by mass or more, even more preferably 0.003% by mass or more and particularly preferably 0%. 005% by mass or more. This is preferred from the point of view of appropriately forming a passive film of a constitutional inner wall material on the inner wall surface of the column, in order to restrict corrosion of the inner wall by purifying the column. The third flow of acetic acid in the ion exchange resin column 7 has a water concentration, preferably 2% by weight or less, more preferably 1% by weight or less and, even more preferably, by 0.5% by weight or less. This is preferred from the point of view of restricting the ionization of hydrogen iodide and acetic acid in the liquid to be treated by purifying the column in order to restrict corrosion of the column's inner wall.
[0070] [0070] Equipment producing acetic acid X may also include a so-called product column or finishing column, which is a distillation column. The present product column serves as an additional purification unit to further purify the fourth flow of acetic acid fed from the ion exchange resin column 7. With the product column, a step, as follows, can be performed. This step is the step of subjecting the fourth stream of acetic acid to purification in order to further purify the acetic acid, while controlling the concentration of corrosive iodine in the fourth stream of acetic acid at 100 ppm or less, where the fourth stream of acetic acid is continuously introduced into the product column.
[0071] [0071] All or part of the fourth flow of acetic acid (liquid) from the ion exchange resin column 7 is continuously introduced into the product column. In the product column, vapors, such as a supernatant flow including traces of components with a low boiling point, are continuously extracted at the top of the column. The vapors are separated into condensed components and gaseous components in a predetermined condenser. A portion of the condensed components is continually refluxed into the product column; another part (or the rest) of the condensed components is recycled to reactor 1; and the gaseous components are fed to the purification system 8. Also in the product column, a bottom liquid, which contains traces of components with a high boiling point, is continuously extracted from the bottom part of the column and is normally recycled to the second flow of acetic acid in line 32, before being introduced into the distillation column
[0072] [0072] In one embodiment, where the product column is provided, potassium hydroxide can be added to the fourth stream of acetic acid, before being introduced into the product column, in order to control the corrosive iodine concentration in the room flow of acetic acid in the product column at 100 ppm or less. The amount of potassium hydroxide to be added can be determined normally, based on the analysis of the chemical composition of a sample sampled from the fourth stream of acetic acid, before being introduced into the product column. Feeding potassium hydroxide to the fourth acetic acid stream tends to decrease hydrogen iodide in the fourth acetic acid stream. Specifically, the feed acts, as described above, on the feed of potassium hydroxide to the second flow of acetic acid with reference to the Reaction Formula (4). The decrease in hydrogen iodide, that is, decrease in the concentration of hydrogen iodide, in the fourth acetic acid flow also tends to decrease the iodine ion concentration in the fourth acetic acid flow. The addition action to the fourth acetic acid stream, before being introduced into the product column, can control the concentration of corrosive iodine in the fourth acetic acid stream, before being introduced into the product column, usually at 100 ppb or less. The addition action can control the concentration of corrosive iodine in the fourth acetic acid stream to a level, preferably, 10 ppb or less, more preferably, 2 ppb or less and, even more preferably, 1 ppb or any less. Such an addition action is preferred to restrict the thickening of corrosive iodines in the fourth flow of acetic acid in the product column, in order to control the concentration of corrosive iodine in the fourth flow of acetic acid to 100 ppm or less. The addition action, as above, is preferred from the point of view of directly and efficiently controlling the concentration of corrosive iodine in the fourth flow of acetic acid to be introduced into the product column.
[0073] [0073] In the embodiment, where the product column is supplied, potassium hydroxide can be fed or added to the fourth flow of acetic acid with distillation in the product column, in order to control the concentration of corrosive iodine in the fourth flow of acetic acid in the product column at 100 ppm or less. The amount of potassium hydroxide to be added can be determined normally, based on the analysis of the chemical composition of a sample sampled from the fourth stream of acetic acid, before being introduced into the product column. Feeding potassium hydroxide to the fourth acetic acid stream with distillation tends to decrease hydrogen iodide in the fourth acetic acid stream. Specifically, the feed acts, as described above, on the potassium hydroxide feed for the second acetic acid stream with reference to the Reaction Formula (4). The decrease in the concentration of hydrogen iodide in the fourth flow of acetic acid with distillation in the product column also tends to decrease the concentration of the iodine ion in the fourth flow of acetic acid.
[0074] [0074] In the embodiment, where the product column is supplied, water can be fed or added to the fourth flow of acetic acid, before being introduced into the product column, in order to control the water concentration in the fourth flow of acetic acid in the product column, from 0.001 to 2% by mass. The amount of water to be added can normally be determined, based on the analysis of the chemical composition of a sample sampled from the fourth stream of acetic acid, before being introduced into the product column. The fourth flow of acetic acid in the product column has a water concentration, preferably 0.001 mass% or more, more preferably 0.002 mass% or more, even more preferably 0.003 mass% or more and, particularly preferably, 0.05% by mass or more. This is preferred, from the point of view of appropriately forming a passive film of a constitutional inner wall material on the inner wall surface of the product column, in order to restrict corrosion of the inner wall during distillation on the column of product. product. The fourth flow of acetic acid in the product column has a water concentration, preferably 2% by weight or less, more preferably 1% by weight or less and even more preferably 0.5% by mass or less, from the point of view of restricting the ionization of hydrogen iodide and acetic acid in the liquid to be treated, in order to restrict the corrosion of the inner wall of the product column during distillation in the product column.
[0075] [0075] The acetic acid production method continuously performs a plurality of purification steps in the acetic acid formed in the reactor 1, in the acetic acid X producing equipment, as described above. In addition to the purifications on the distillation columns 3 and 5, the purification steps include purifications on the distillation column 6 and on the ion exchange resin column 7, each of which serves as an additional purification unit, or the purification steps include purifications on the distillation column 6, ion exchange resin column 7 and product column, each of which serves as an additional purification unit. The method including such additional purification step (s) in the additional purification unit (s) is advantageous to obtain a high degree of purity of the resulting acetic acid product. The acetic acid product produced by the method has an iodine ion concentration, preferably 10 ppb or less and, more preferably, 1 ppb or less and normally 0.01 ppb or more, or 0.1 ppb or more. The purification step (s), as performed in the additional purification unit (s) with the control of the corrosive iodine concentration at 100 ppm or less, is (are) appropriate ( s) to restrict corrosion of the unit (s). The purification step (s), as above, can eliminate or minimize the use of nickel-based alloys and other materials with high corrosion resistance, but being expensive as materials to constitute the inner wall of the (s) unit (s), with which the step (s) is (are) performed. Details of this will be illustrated in the functional examples. In addition, the purification step (s), when performed, may decrease the amount of corrosion-resistant materials to be used in acetic acid-producing equipment X.
[0076] [0076] As described above, the acetic acid production method is appropriate to restrict the corrosion of acetic acid X-producing equipment. The acetic acid production method, which is suitable for restricting the corrosion of acetic acid-X producing equipment. , is also suitable for eliminating or minimizing the use of such expensive corrosion-resistant materials in equipment, to lower the cost of producing acetic acid. EXAMPLES
[0077] [0077] The present invention will be illustrated in more detail with reference to several examples below. It should be noted, however, that the examples are never intended to limit the scope of the present invention. Example 1
[0078] [0078] Acetic acid was produced using the equipment producing acetic acid X illustrated in Fig. 1. In this process, the equipment was operated, so that the second flow of acetic acid from the distillation column 5, which serves as a column of dehydration, include, as a composition, 510 ppm of water, 105 ppm of propionic acid, 1 ppm of methyl acetate, 17 ppm of formic acid, 100 ppb of hydrogen iodide, 120 ppb of iodine ion, 5 ppb of iodide methyl, 10 ppb of hexyl iodide and 49 ppm of potassium in the form of potassium oxide, with the remainder being approximately acetic acid. In the production process, the second flow of acetic acid from the distillation column 5 was introduced into the distillation column 6, which serves as a component removal column with a high boiling point, and subjected to distillation there (third distillation step). The distillation column 6 used here was a column with 12 plates (column including 12 plates). Distillation on distillation column 6 was carried out as follows. The second flow of acetic acid from the distillation column 5 was introduced into the distillation column 6, in the third dish from the bottom at a rate of 1005 grams per hour; and a lateral flow (third flow of acetic acid) was extracted from distillation column 6 in the sixth plate from the bottom at a rate of 998 grams per hour. From a supernatant stream from the top portion of the column, a portion, such as a distillate, was removed or extracted in an amount (amount of distillate removed) of 6 grams per hour; and another part was refluxed at a reflux rate of 810 grams per hour. A bottom liquid was removed at a rate of 1 gram per hour. During distillation on the distillation column 6, the pressure at the top of the column was controlled within the range of 75 to 80 kPa (pressure gauge); the bottom pressure was controlled within the range of 95 to 100 kPa (gauge pressure), which is greater than the pressure at the top of the column; the temperature at the top of the column was set at 82 ° C; and the bottom temperature was set at 147º C.
[0079] [0079] The distillate formed as a result of distillation in the distillation column 6 was sampled and subjected to a corrosivity assessment test, as follows, where the test simulated distillation in the distillation column 6. Initially, an autoclave equipped with a box pressure-proof zirconium was prepared, 500 ml of distillate, as a test liquid, was loaded into the pressure-proof box, specimens having a size of 36 mm x 25 mm by 2.5 mm were placed in the liquid test, and the autoclave was capped. Separately, the test liquid, before testing, was subjected to a chemical composition analysis. The results of the chemical composition analysis before the corrosivity test are shown in Table 1. A material to make up the specimens was selected from zirconium (Zr), a nickel-based alloy (trade name HASTELLOY C, supplied by Oda Koki Co., Ltd.), stainless steel (SUS) 444 (supplied by Morimatsu Industry Co., Ltd.), which is a high purity 18Cr-2Mo ferritic stainless steel, and 316 stainless steel (SUS) (supplied by UMETOKU Inc.). Then, the test liquid in the autoclave was purged with nitrogen at an oxygen concentration of 1 ppm or less. Subsequently, the interior of the autoclave was pressurized to 30 kPa (gauge pressure) by the introduction of nitrogen, its temperature was raised to 135º C by heating in an oil bath, and at static pressure, after the temperature increased, it was fixed at 90 kPa (gauge pressure). After a lapse of 500 hours under static conditions (static temperature and static pressure), the interior of the autoclave was cooled to room temperature, and part of the test liquid was sampled from the autoclave nozzle, followed by analysis of the chemical composition of the sampled liquid. . Table 1 also presents the results of the chemical composition analysis after the corrosivity test.
[0080] [0080] The autoclave, after the cooling process, was purged with nitrogen and was discovered, from where the specimens were recovered and weighed en masse. Based on the results of the measurements, the thickness reduction rates or corrosion rates (in millimeters (mm) per year) of the specimens were calculated. The corrosion rate corresponds to the reduction in the thickness (mm) of each specimen per year. Each of the specimens was visually examined to determine whether they suffered localized corrosion (including honeycomb corrosion). the results of the corrosivity assessment test are shown in Table 3. In Table 3, the nickel-based alloy is indicated as "HC". Example 2
[0081] [0081] Acetic acid was produced using the equipment producing acetic acid X by a procedure identical to that of Example 1, except by distilling it on the distillation column 6, as follows. Specifically, the distillate was removed from the top part of the column in an amount (amount of distillate removed) of 60 grams per hour, instead of 6 grams per hour, and the side flow (third flow of acetic acid) was extracted of distillation column 6 in an amount of 944 grams per hour, instead of 998 grams per hour. Except for the use of a distillate formed here in the distillation in the distillation column 6, a corrosivity assessment test was carried out by a procedure similar to that of Example 1. The results of the chemical composition analyzes in Example 2 are shown in Table 1 , and the results of the corrosion rate measurements and visual examinations in Example 2 are shown in Table 3. This also occurs for Examples 3 to 6, as follows. Example 3
[0082] [0082] Acetic acid was produced using equipment producing acetic acid X, by a procedure similar to that of Example 1; and a corrosivity assessment test was performed by a procedure similar to that of Example 1, except for the use of a test liquid with a methanol concentration of 200 ppm, where the test liquid was prepared by adding methanol to the distillate at be subjected to the corrosivity assessment test. Example 4
[0083] [0083] Acetic acid was produced using equipment producing acetic acid X, by a procedure similar to that of Example 1; and a corrosivity assessment test was carried out by a procedure similar to that of Example 1, except for the use of a test liquid with a potassium concentration of 42 ppm, where the test liquid was prepared by adding potassium hydroxide to the distillate to be subjected to the corrosivity assessment test. Example 5
[0084] [0084] Acetic acid was produced using equipment producing acetic acid X, by a procedure identical to that of Example 1, except that the second flow of acetic acid from the distillation column 5 had a different chemical composition, where the distillation column serves as a dehydration column; that the distillate was removed in a different amount (amount of distillate removed) from the distillation column 6; and that the lateral flow (third flow of acetic acid) was extracted from the distillation column 6 in a different amount. The second flow of acetic acid in Example 5 included 510 ppm of water, 105 ppm of propionic acid, 1 ppm of methyl acetate, 17 ppm of formic acid, 10 ppb of hydrogen iodide, 14 ppb of iodine ion, 5 pPb of methyl iodide, 10 ppb of hexyl iodide and 49 ppm of potassium in the form of potassium acetate, with the remainder being approximately acetic acid. In Example 5, the distillate was removed from the distillation column 6 in an amount
[0085] [0085] Acetic acid was produced using equipment producing acetic acid X, by a procedure similar to that of Example 5; and a corrosivity assessment test was carried out by a procedure similar to that of Example 1, except for carrying out the test at a static temperature and a static pressure of 150º C and 200 kPa (gauge pressure), respectively, instead of 135º C and 90 kPa (gauge pressure).
[0086] [0086] A corrosivity assessment test was performed by a procedure similar to that of Example 1, except for the use of another test liquid, instead of the distillate obtained from the distillation column 6 in the acetic acid production process using the equipment of acetic acid production X. The other test liquid included, as a composition, 0.05% by weight of water, 100 ppm of propionic acid, 5 ppm of methyl acetate, 20 ppm of formic acid, 0.01 ppm of hydrogen iodide, 0.02 ppm iodine ions, 5 ppb of methyl iodide and 5 ppb of hexyl iodide, with the remainder being approximately acetic acid. The results of the chemical composition analyzes in Example 7 are shown in Table 2, and the results of the corrosion rate measurements and visual examinations in Example 7 are given in Table 3. This is the same for Example 8 and Comparative Examples 1 to 3 below. Example 8
[0087] [0087] A corrosivity assessment test was carried out by a procedure similar to that of Example 1, except for the use of another test liquid, instead of the distillate obtained from the distillation column 6 in the acetic acid production process using the equipment of acetic acid production X, and to carry out the corrosivity assessment test at a static temperature of 118º C, instead of 135º C. The other test liquid included, as a composition, 0.05% by mass of water, 100 ppm propionic acid, 5 ppom methyl acetate, 20 ppm formic acid, 0.01 ppm hydrogen iodide, 0.02 ppm iodine ions, 5 ppb methyl iodide and 5 ppb hexyl iodide, with the remainder being approximately acetic acid. Comparative Example 1
[0088] [0088] Acetic acid was produced using equipment producing acetic acid X, by a procedure identical to that of Example 1, except that the second flow of acetic acid from the distillation column 5 had a different chemical composition, where the distillation column 5 serves as a dehydration column. The second flow of acetic acid in Comparative Example 1 included 510 ppm water, 105 ppm propionic acid, 1 ppm methyl acetate, 17 ppm formic acid, 990 ppb hydrogen iodide, 1050 ppb iodine ion, 5 ppb of methyl iodide, 10 ppb of hexyl iodide and 49 pom of potassium in the form of potassium acetate, with the remainder being approximately acetic acid. Except for the use of a distillate formed here in the distillation in the distillation column 6, a corrosivity assessment test was carried out by a procedure similar to that of Example
[0089] [0089] A corrosivity assessment test was performed by a procedure similar to that of Example 1, except for the use of another test liquid, instead of the distillate obtained from the distillation column 6 in the acetic acid production process using the equipment of acetic acid production X. The other test liquid included, as a composition, 0.0005% by weight of water, 30 ppm of propionic acid, 103 ppm of methyl acetate, 655 ppm of formic acid, 120 ppm of iodide hydrogen, 134 ppm of iodine ions, 595 ppb of methyl iodide and 8 ppb of hexyl iodide, with the remainder being approximately acetic acid.
[0090] [0090] A corrosivity assessment test was carried out by a procedure similar to that of Example 1, except for the use of another test liquid, instead of the distillate obtained from the distillation column 6 in the acetic acid production process using the equipment of acetic acid production X. The other test liquid included, as a composition, 2.1% by weight of water, 29 ppm of propionic acid, 102 ppm of methyl acetate, 650 ppm of formic acid, 118 ppm of iodide of hydrogen, 132 ppm of iodine ions, 590 ppb of methyl iodide and 8 ppb of hexyl iodide, with the remainder being approximately acetic acid.
[0091] [0091] In the corrosivity assessment tests, materials can be evaluated, as follows, in terms of thickness reduction (weight loss). A material having a corrosion rate under the predetermined conditions of 0.05 mm per year or less can be assessed as adequately usable as an internal wall constitutional material for purification units, which are exposed to the conditions; a material with a corrosion rate in the predetermined conditions greater than 0.05 mm per year to less than 0.2 mm per year can be evaluated as usable as an internal wall constitutional material for purification units, which are exposed to the conditions; and a material with a corrosion rate under the predetermined conditions of 0.2 mm per year or more can be assessed as unsuitable for use as an internal wall constitutional material for purification units, which are exposed to the conditions. Based on this, the evaluation results showed that, of the materials, SUS 444 and SUS 316 are unsuitable for use under conditions, according to Comparative Examples 1 to 3, in which the corrosive iodine concentration (total iodide concentration hydrogen content and iodine ion concentration) was greater than 100 ppm. These materials are unsuitable from the point of view of corrosion rate or thinning. In addition, the material HASTELLOY C ("HC", the nickel-based alloy) experienced localized corrosion under all conditions, according to Comparative Examples 1 to 3. And, separately, there is a tendency for iodide ionization hydrogen and acetic acid is restricted by decreasing the concentration of water in a liquid to be treated; and that the restriction to ionization acts advantageously in the restriction to corrosion. The trend, as above, is found in the results of the corrosivity assessment test in Comparative Examples 1 and 3. Specifically, HC, SUS 444 and SUS 316 materials in Comparative Example 3 showed corrosion rates higher than the corresponding corrosion rates in the Comparative Example 1, where the corrosivity assessment test in Comparative Example 3 was performed at a significantly higher water concentration, compared to Comparative Example 1. In contrast, zirconium (Zr) and SUS 444, in Comparative Example 2, presented corrosion rates higher than the corresponding corrosion rates in Comparative Example 1 and 3, where the corrosivity assessment test in Comparative Example 2 was performed at a very low concentration of water, and where zirconium can be used as a material having much high resistance to corrosion. This is probably due to a tendency for a passive film to not be properly formed on the surface of the material under such conditions, with a very low water concentration.
[0092] [0092] In contrast, the HC nickel-based alloy was evaluated as a suitably usable material, from the point of view of the corrosion rate, and did not show any localized corrosion in all Examples 1 to 8, where the evaluation tests of Corrosivity in Examples 1 to 8 were performed at corrosive iodine concentrations (total hydrogen iodide concentration and iodine ion concentration) of 100 ppm or less. SUS 444 was evaluated as a suitably usable material, from the point of view of the corrosion rate, and did not present approximately any corrosion located in the
[0096] [0096] The configurations, in accordance with the present invention, and their variations or modifications will be listed below as a summary of the description above.
[0097] [0097] Appendix 1: A method produces acetic acid in equipment producing acetic acid. The equipment includes a reactor, a first distillation column, a second distillation column and an additional purification unit. The method includes a reaction step, a first purification step, a second purification step and a third purification step. In the reaction step, a mixture of material, including methanol, carbon monoxide, a catalyst and an iodide, is subjected to a carbonyl reaction of methanol in the reactor to form acetic acid. In the first purification step, a stream of crude acetic acid is subjected to distillation in the first distillation column, where the stream of crude acetic acid contains acetic acid formed in the reaction step. The first purification step provides a first flow of acetic acid enriched with acetic acid, compared to the flow of crude acetic acid. In the second purification step, the first acetic acid stream is subjected to distillation on the second distillation column, to provide a second acetic acid enriched acetic acid stream, as compared to the first acetic acid stream. In the third purification step, an acetic acid stream is subjected to purification in the additional purification unit, while controlling the concentration of corrosive iodine in the acetic acid stream passing through the additional purification unit at 100 ppm or less, where the flow of acetic acid is the second stream of acetic acid or is a stream of acetic acid derived from the second stream of acetic acid. The third purification step provides a third stream of acetic acid enriched with acetic acid, compared to the second stream of acetic acid.
[0098] [0098] Appendix 2: In the acetic acid production method, according to Appendix 1, the third purification step may include subjecting the acetic acid flow to purification, while controlling the concentration of corrosive iodine in the acetic acid flow through the additional purification unit at 30 ppm or less.
[0099] [0099] Appendix 3: In the acetic acid production method, according to Appendix 1l, the third purification step may include subjecting the acetic acid flow to purification, while controlling the concentration of corrosive iodine in the acetic acid flow through the additional purification unit at 10 ppm or less.
[0100] [0100] Appendix 4: In the acetic acid production method, according to Appendix 1, the third purification step may include subjecting the acetic acid flow to purification, while controlling the concentration of corrosive iodine in the acetic acid flow through the additional purification unit at 3.5 ppm or less.
[00101] [00101] Appendix 5: In the acetic acid production method, according to Appendix 1, the third purification step may include subjecting the acetic acid flow to purification, while controlling the concentration of corrosive iodine in the acetic acid flow through the additional purification unit at 1 ppm or less.
[00102] [00102] Appendix 6: In the acetic acid production method, according to Appendix 1, the third purification step may include subjecting the acetic acid flow to purification, while controlling the concentration of corrosive iodine in the acetic acid flow through the additional purification unit at 0.3 ppm or less.
[00103] [00103] Appendix 7: In the acetic acid production method, according to Appendix 1, the third purification step may include subjecting the acetic acid flow to purification, while controlling the concentration of corrosive iodine in the acetic acid flow through the additional purification unit at 0.1 ppm or less.
[00104] [00104] Appendix 8: In the acetic acid production method, according to Appendix 1, the third purification step may include subjecting the acetic acid flow to purification, while controlling the concentration of corrosive iodine in the acetic acid flow through the additional purification unit at 0.03 ppm or less.
[00105] [00105] Appendix 9: In the acetic acid production method, according to any of Appendices 1 to 8, the additional purification unit may include a third distillation column, and the third purification step may include subjecting the flow of acetic acid to distillation in the third distillation column.
[00106] [00106] Appendix 10: In the acetic acid production method, according to Appendix 9, the third purification step may include feeding at least one substance selected from the group consisting of methanol, methyl acetate and potassium hydroxide to the flow of acetic acid with distillation in the third distillation column.
[00107] [00107] Appendix 11: In the acetic acid production method, according to Appendix 10, methanol can be fed to the acetic acid flow with the distillation in the third distillation column, at a level equal to or lower than that level, in which the flow of acetic acid is introduced in the third distillation column, where the levels are defined in relation to the height direction of the third distillation column.
[00108] [00108] Appendix 12: In the acetic acid production method, according to one of Appendices 10 and 11, methyl acetate can be fed to the acetic acid flow with distillation in the third distillation column, at a level equal to or less than the level, at which the acetic acid flow is introduced in the third distillation column, where the levels are defined in relation to the height direction of the third distillation column.
[00109] [00109] Appendix 13: In the acetic acid production method, according to any of Appendices 10 to 12, potassium hydroxide can be fed to the acetic acid flow with distillation in the third distillation column, at an equal level or greater than the level, at which the acetic acid flow is introduced into the third distillation column, where the levels are defined in relation to the height direction of the third distillation column.
[00110] [00110] Appendix 14: In the acetic acid production method, according to any of Appendices 9 to 13, the third purification step may include at least one item selected from the group consisting of the recycling part of a supernatant from the third column of distillation for the first acetic acid stream, before being introduced into the second distillation column, and by the supernatant recycling part of the third distillation column to the crude acetic acid stream, before being introduced into the first distillation column, the in order to control the concentration of corrosive iodine.
[00111] [00111] Appendix 15: In the acetic acid production method, according to any of Appendices 9 to 14, the acetic acid producing equipment may also include a purification system. The purification system treats part of the gaseous components emanating from the equipment to form a component to be recycled to the reactor, and a component to be discharged from the equipment.
[00112] [00112] Appendix 16: The method of producing acetic acid, according to Appendix 15, also includes introducing part of a supernatant from the third distillation column into the purification system.
[00113] [00113] Appendix 17: In the acetic acid production method, according to any of Appendices 1 to 16, the third purification step may include feeding at least one substance selected from the group consisting of methanol, methyl acetate and hydroxide potassium to a stream of acetic acid, before being introduced into the additional purification unit, in order to control the concentration of corrosive iodine.
[00114] [00114] Appendix 18: In the acetic acid production method, according to Appendix 17, at least one substance can be fed to the acetic acid stream, before being introduced into the additional purification unit, so that the acid stream acetic acid has a corrosive iodine concentration of 100 ppb or less.
[00115] [00115] Appendix 19: In the acetic acid production method, according to any of Appendices 1 to 18, the flow of acetic acid in the additional purification unit can be controlled to have a water concentration of 0.001% by mass or more.
[00116] [00116] Appendix 20: In the acetic acid production method, according to any of Appendices 1 to 18, the flow of acetic acid in the additional purification unit can be controlled to have a water concentration of 0.003% by weight or more.
[00117] [00117] Appendix 21: In the acetic acid production method, according to any of Appendices 1 to 18, the flow of acetic acid in the additional purification unit can be controlled to have a water concentration of 0.005% by weight or more.
[00118] [00118] Appendix 22: In the acetic acid production method, according to any of Appendices 1 to 18, the flow of acetic acid in the additional purification unit can be controlled to have a water concentration of 0.006% by mass or more.
[00119] [00119] Appendix 23: In the acetic acid production method, according to any of Appendices 1 to 22, the flow of acetic acid in the additional purification unit can be controlled to have a water concentration of 2% by mass or any less.
[00120] [00120] Appendix 24: In the acetic acid production method, according to any of Appendices 1 to 22, the flow of acetic acid in the additional purification unit can be controlled to have a water concentration of 1% by mass or any less.
[00121] [00121] Appendix 25: In the acetic acid production method, according to any of Appendices 1 to 22, the flow of acetic acid in the additional purification unit can be controlled to have a water concentration of 0.5% in mass or less.
[00122] [00122] Appendix 26: In the acetic acid production method, according to any of Appendices 1 to 25, purification in the additional purification unit can be carried out at 160º C or less.
[00123] [00123] Appendix 27: In the acetic acid production method, according to any of Appendices l1 to 25, purification in the additional purification unit can be carried out at 150ºC or less.
[00124] [00124] Appendix 28: In the acetic acid production method, according to any of Appendices l1 to 25, purification in the additional purification unit can be carried out at 140ºC or less.
[00125] [00125] Annex 29: In the acetic acid production method, according to any of Appendices 1 to 25, purification in the additional purification unit can be carried out at 120ºC or less.
[00126] [00126] Appendix 30: In the acetic acid production method, according to any of Appendices 1 to 29, the flow of crude acetic acid can have an acetic acid concentration of 87 to 99% by weight.
[00127] [00127] Appendix 31: In the acetic acid production method, according to any of Appendices 1 to 30, the concentration of acetic acid in the first acetic acid stream may be greater than the concentration of acetic acid in the acid stream crude acetic acid, and can be 99 to 99.9% by mass.
[00128] [00128] Appendix 32: In the acetic acid production method, according to any of Appendices 1 to 31, the concentration of acetic acid in the second stream of acetic acid may be greater than the concentration of acetic acid in the first stream of acetic acid, and can be 99.1 to 99.99% by weight.
[00129] [00129] Appendix 33: In the acetic acid production method, according to any of Appendices 1 to 32, the concentration of acetic acid in the third stream of acetic acid may be greater than the concentration of acetic acid in the second stream of acetic acid, and can be from 99.8 to 99.999% by weight.
LIST OF REFERENCE NUMBERS 1 - reactor 2 - evaporator 3 - distillation column (first distillation column) 4 -— decanter - distillation column (second distillation column) 6 - distillation column (third distillation column; purification unit additional) 7 - ion exchange resin column (additional purification unit) 8 - purification system

权利要求:
Claims (14)
[1]
1. METHOD TO PRODUCE ACETIC ACID IN EQUIPMENT PRODUCING ACETIC ACID, characterized by the equipment comprising: reactor; first distillation column; second distillation column; and additional purification unit, the method consisting of: reaction step to subject a material mixture, composed of methanol, carbon monoxide, a catalyst and an iodide, to a reaction of methanol carbonylation in the reactor to form acetic acid; first purification step to subject a stream of crude acetic acid to distillation in the first distillation column to provide a first stream of acetic acid, the stream of crude acetic acid containing the acetic acid formed in the reaction step, the first stream of acetic acid being enriched with acetic acid compared to the crude acetic acid flow; second purification step to subject the first stream of acetic acid to distillation in the second distillation column to provide a second stream of acetic acid enriched with acetic acid compared to the first stream of acetic acid; and third purification step to subject an acetic acid stream for purification in the additional purification unit, while controlling a concentration of corrosive iodine in the acetic acid stream passing through the additional purification unit at 100 ppm or less, to provide a third flow of acetic acid enriched with acetic acid compared to the second flow of acetic acid.
[2]
METHOD according to claim 1, characterized in that the additional purification unit consists of a third distillation column, and the third purification step comprises distilling the third distillation column.
[3]
METHOD, according to claim 2, characterized in that the third purification stage comprises feeding at least one substance selected from the group consisting of methanol, methyl acetate and potassium hydroxide to the acetic acid flow with distillation in the third column of distillation in order to control the concentration of corrosive iodine.
[4]
METHOD, according to claim 3, characterized in that methanol is fed to the acetic acid flow with the distillation in the third distillation column at a level equal to or less than one level, in which the acetic acid flow is introduced in the third distillation column, where the levels are defined with respect to a height direction of the third distillation column.
[5]
METHOD according to any one of claims 3 and 4, characterized in that the methyl acetate is fed to the acetic acid flow with the distillation in the third distillation column at a level equal to or less than a level, at which the flow of acetic acid is introduced in the third distillation column, where the levels are defined with respect to a height direction of the third distillation column.
[6]
METHOD according to any one of claims 3 to 5, characterized in that the potassium hydroxide is fed to the acetic acid flow with the distillation in the third distillation column at a level equal to or greater than a level, at which the flow of acetic acid is introduced in the third distillation column, where the levels are defined in relation to a height direction of the third distillation column.
[7]
METHOD, according to any one of claims 2 to 6, characterized in that the third purification step consists of at least one of the group consisting of: recycling part of a supernatant from the third distillation column to the first acid flow acetic, before being introduced into the second distillation column; and recycling part of the supernatant from the third distillation column to the crude acetic acid flow, before being introduced into the first distillation column, in order to control the concentration of corrosive iodine.
[8]
8. METHOD according to any one of claims 2 to 7, characterized in that the acetic acid-producing equipment still comprises a purification system that treats the part of the gaseous components emanating from the equipment to form a component to be recycled to the reactor, and a component to be unloaded from the equipment.
[9]
9. METHOD according to claim 8, characterized in that the method further comprises introducing part of a supernatant from the third distillation column into the purification system.
[10]
10. METHOD according to any one of claims 1 to 9, characterized in that the third purification step comprises feeding at least one substance selected from the group consisting of methanol, methyl acetate and potassium hydroxide to an acetic acid stream, before to be introduced into the additional purification unit.
[11]
11. METHOD according to claim 10, characterized in that at least one substance is fed into the acetic acid stream, before being introduced into the additional purification unit, so that the acetic acid stream has a corrosive iodine concentration of 100 ppb or less.
[12]
METHOD according to any one of claims 1 to 11, characterized in that the flow of acetic acid in the additional purification unit has a water concentration of 0.001% by weight, or more.
[13]
13. METHOD according to any one of claims 1 to 12, characterized in that the flow of acetic acid in the additional purification unit has a water concentration of 2% by weight or less.
[14]
METHOD according to any one of claims 1 to 13, characterized in that the third purification step comprises performing the purification in the additional purification unit at a temperature of 160 ° C or less.

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法律状态:
2020-03-24| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2020-03-31| B06I| Publication of requirement cancelled [chapter 6.9 patent gazette]|Free format text: ANULADA A PUBLICACAO CODIGO 6.21 NA RPI NO 2568 DE 24/03/2020 POR TER SIDO INDEVIDA. |

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2020-12-22| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2021-08-24| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2021-12-07| B11D| Dismissal acc. art. 38, par 2 of ipl - failure to pay fee after grant in time|

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2021-12-07| B350| Update of information on the portal [chapter 15.35 patent gazette]|

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JP2015-192286|2015-09-29|

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JP2015192286|2015-09-29|

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PCT/JP2016/077651|WO2017057085A1|2015-09-29|2016-09-20|Method of producing acetic acid|

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