Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
  • C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
  • C07C51/255—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting
  • C07C51/265—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting having alkyl side chains which are oxidised to carboxyl groups
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/42—Separation; Purification; Stabilisation; Use of additives
  • C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation

Definitions

• the present invention relates to a method for producing an aromatic carboxylic acid.
• terephthalic acid which is an aromatic carboxylic acid
• a process for producing terephthalic acid which is an aromatic carboxylic acid
• a reactor 1 containing a catalyst in an acetic acid solvent first, as an oxidation reaction step, an alkyl aromatic aromatic acid is prepared in a reactor 1 containing a catalyst in an acetic acid solvent.
• the compound para-xylene a is oxidized with air b to generate terephthalic acid.
• the generated terephthalic acid is a slurry in which a part thereof is dissolved in a solvent, and the reaction slurry 1c is introduced into the crystallization tank 2 and is evaporated under reduced pressure to further precipitate terephthalic acid to form a crystallization slurry d.
• the reaction slurry 1c is introduced into the crystallization tank 2 and is evaporated under reduced pressure to further precipitate terephthalic acid to form a crystallization slurry d.
• the crystallization slurry d is separated into a terephthalic acid cake e and a separated mother liquor f through a solid-liquid separation step in which the crystallization slurry d is separated by the solid-liquid separation device 3.
• the terephthalic acid cake e is dried in the drying device 4 to obtain terephthalic acid crystals g.
• the separated mother liquor f can be reused as a recycled mother liquor h as a solvent in the above-mentioned acidification reaction step.
• impurities contained in the separated mother liquor f accumulate in the system, the quality of the obtained terephthalic acid crystals g is reduced. Have an effect. Therefore, in order to suppress the accumulation of impurities, a part of the separated mother liquor f is purged out of the system as a purge mother liquor i.
• the purge mother liquor i contains an oxidation catalyst and a solvent component that are not only impurities, and it is necessary to recover these effective components.
• the solvent component of the purge mother liquor i is evaporated by a solvent evaporator 5 to concentrate high-boiling components such as an oxidation catalyst and impurities, and the oxidation catalyst is extracted from the concentrated residue. Collect by processing. Further, the evaporated solvent vapor k is usually recovered acetic acid m obtained by removing the oxidized water 1 by a dehydration apparatus 6 such as distillation, and is used as a solvent in the oxidation reaction step or a washing liquid in the solid-liquid separation step. Reuse.
• the purge mother liquor i is accompanied by solids such as terephthalic acid and its oxidized intermediate due to leakage in the solid-liquid separator 3.
• Patent Document 1 discloses that when separating mother liquor f is branched, one is returned as the recycled mother liquor h to the above oxidation reaction step, and the other is concentrated as the purge mother liquor i, the concentration treatment is performed in advance of this concentration treatment. A method for solid-liquid separation of a solid content contained in a purge mother liquor i is described.
• a patent is given for a method of solid-liquid separation in which the reaction slurry c is directly heated without passing through the crystallization tank 2 or is depressurized and evaporated in the crystallization tank 2 while maintaining high temperature and pressure without releasing pressure to normal pressure. It is described in Document 2 and Patent Document 3. Thereby, it is possible to simplify the drying step of the downstream separated terephthalic acid cake e and to reduce the heat energy consumed in the purification step of the dried terephthalic acid crystals g. ,.
• the mother liquor of high temperature and high pressure obtained by solid-liquid separation under high temperature and high pressure has a higher solubility than that of the mother liquor obtained by solid-liquid separation at lower temperature and low pressure. High! ⁇ . Therefore, many active ingredients such as terephthalic acid and its intermediate are dissolved, and if the separation mother liquor is concentrated at a time until the residue is obtained by purging the separated mother liquor at high temperature and high pressure, the separated mother liquor at high temperature and high pressure can be obtained.
• the active ingredients such as terephthalic acid and the intermediate thereof are mixed into the residue, leading to a decrease in productivity.
• Patent Document 1 Japanese Patent Publication No. 2000-505041
• Patent Document 2 JP 2001-139514 A
• Patent Document 3 JP-A-2002-336687
• the present invention relates to a method for producing an aromatic carboxylic acid having an alkylaromatic compound and a method for treating a separation mother liquor obtained by solid-liquid separation of an oxidation reaction slurry in a high-temperature and high-pressure state at a high temperature and a high pressure.
• an object of the present invention is to produce an aromatic carboxylic acid by dissolving the mother liquor in the mother liquor and recovering the active ingredient by efficiently utilizing the energy of the separated mother liquor for concentration treatment.
• the present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, concentrated purging was performed by depressurizing and evaporating the purge mother liquor to a pressure equal to or lower than the vapor pressure of the mother liquor at the mother liquor temperature to precipitate an aromatic carboxylic acid. Then, the inventors have found that the above-mentioned problems can be solved by recovering the precipitated aromatic carboxylic acid, and have completed the present invention. That is, the gist of the present invention resides in the following 110.
• an oxidation step of oxidizing (A) an alkylaromatic compound in an acetic acid solvent at 140-230 ° C in a acetic acid solvent under a pressure higher than normal pressure to produce an aromatic carboxylic acid;
• the mother liquor is subjected to concentration treatment by depressurizing and evaporating the mother liquor to a pressure equal to or lower than the vapor pressure of the mother liquor at the mother liquor temperature to precipitate an aromatic carboxylic acid.
• a method for producing an aromatic carboxylic acid which comprises recovering the aromatic carboxylic acid.
• the above-mentioned (D) concentration step becomes a two-stage concentration power, the mother liquor is subjected to the first-stage concentration treatment at a pressure higher than the normal pressure, and the pressure is reduced to a pressure lower than the vapor pressure of the mother liquor at the mother liquor temperature.
• the first-stage concentration treatment is performed to precipitate the aromatic carboxylic acid, and then the precipitated aromatic carboxylic acid is recovered, and the mother liquor after the recovery of the aromatic carboxylic acid is subjected to the second-stage concentration treatment.
• the (A) alkyl aromatic compound is dissolved in an acetic acid solvent at a pressure exceeding atmospheric pressure in the presence of a catalyst.
• An oxidation process that oxidizes in the presence of 1, to produce an aromatic carboxylic acid,
• the above (D) concentration step also has a two-stage concentration power, the mother liquor is subjected to the first-stage concentration treatment at a pressure higher than the normal pressure, and is decompressed and evaporated to a pressure lower than the vapor pressure of the mother liquor at the mother liquor temperature.
• the first-stage concentration treatment is performed to precipitate an aromatic carboxylic acid, and then the precipitated aromatic carboxylic acid is recovered and returned to the step (A), and the mother liquor after the recovery of the aromatic carboxylic acid is added to the mother liquor.
• a method for producing an aromatic carboxylic acid comprising performing a second concentration treatment to evaporate and recover a solvent component.
• the (B) solid-liquid separation step includes a step of washing an aromatic carboxylic acid obtained by solid-liquid separation with a washing liquid, wherein the solid-liquid separation step and the washing step are performed.
• the energy of the mother liquor is used for part of the concentration in the concentration of the purge mother liquor, whereby the recovery rate of useful components contained in the purge mother liquor is reduced. Can be raised.
• the energy required for raising the temperature is reduced, and the ionic reaction energy can be effectively recovered.
• FIG. 1 is a production process diagram of an aromatic carboxylic acid crystal according to the present invention.
• Aromatic carboxylic acid slurry E Aromatic carboxylic acid cake
• the present invention is a method for producing an aromatic carboxylic acid, comprising (A) an oxidizing step, (B) a solid-liquid separation step, (C) a mother liquor recycling step, and (D) a concentration step.
• the alkyl aromatic compound A is liquid-phased in a reaction medium at 140 to 230 ° C to obtain an aromatic carboxylic acid slurry C.
• the aromatic carboxylic acid to be produced is terephthalic acid
• the alkyl aromatic compound A is para-xylene.
• acetic acid is used as a reaction medium in the oxidation step (A).
• the amount of the acetic acid solvent used is desirably 2 to 6 times by weight, more preferably 2 to 4 times by weight, relative to paraxylene. If the amount of acetic acid is too small, the temperature of the reaction slurry is too high, which may cause problems such as clogging.If the amount is too large, the amount of solvent in the system with respect to the product production becomes large, and it is necessary to increase the size of the equipment, which is economical Is not preferred.
• the recycled mother liquor H obtained in the (B) solid-liquid separation step described below and the acetic acid M recovered from the solvent vapor obtained in the (D) concentration step can be reused. .
• the solvent vapor obtained in the (D) concentration step it is preferable to subject the solvent vapor obtained in the (D) concentration step to a dehydration treatment by distillation or the like.
• the acetic acid solvent in the present invention is preferably a mixture of acetic acid and water, which is usually a mixture of 100 parts by weight of acetic acid and 120 parts by weight of water, preferably 5 to 15 parts by weight. You.
• an aromatic compound having an alkyl substituent or a partially oxidized alkyl substituent can be used as the alkyl aromatic compound A in the present invention.
• Such an alkyl aromatic compound may be monocyclic or polycyclic.
• the alkyl substituent include an alkyl group having 114 carbon atoms such as a methyl group, an ethyl group, an propyl group, and an isopropyl group.
• the partially oxidized alkyl group include an aldehyde group, an acyl group, a carboxyl group, and a hydroxyalkyl group.
• aromatic compound having an alkyl substituent that is, the alkyl-substituted aromatic hydrocarbon
• the aromatic compound having an alkyl substituent that is, the alkyl-substituted aromatic hydrocarbon
• the aromatic compound having an alkyl substituent include, for example, m-diisopropylbenzene, p-diisopropylbenzene, m-cymene, ⁇ -cymene, and m-xylene
• the alkyl group in the above compound is partially oxidized to form an aldehyde group, an acyl group, a carboxyl group or a hydroxyalkyl group. It is a compound that has been ridden. Specific examples include 3-methylbenzaldehyde, 4-methylbenzaldehyde, m-toluic acid, p-toluic acid, 3-formylbenzoic acid, 4-formylbenzoic acid, 2-methyl-6-formylnaphthalene, and the like. it can. These are used alone or as a mixture of two or more.
• the alkyl aromatic compound A preferably includes m-xylene and p-xylene, and more preferably includes p-xylene.
• the alkyl aromatic compound A may be usually oxidized by the molecular oxygen-containing gas B.
• the molecular oxygen-containing gas B for example, a gas containing molecular oxygen such as air, oxygen diluted with an inert gas, or oxygen-enriched air is used. Of these, air is preferably used practically.
• aromatic carboxylic acids in the present invention include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4-biphenyldicarboxylic acid; trimellitic acid, trimesin And aromatic polycarboxylic acids such as pyromellitic acid.
• the method of the present invention is preferably applied to the production of an aromatic dicarboxylic acid or an aromatic carboxylic acid that is hardly soluble in a reaction solvent, and is particularly suitable for the production of terephthalic acid using p-xylene as a raw material. Prefer to apply,.
• the catalyst used for the oxidation of the alkyl aromatic compound A is not particularly limited as long as it has the ability to oxidize the alkyl aromatic compound A and convert it to an aromatic carboxylic acid. Absent. Usually, a heavy metal compound is used, and if necessary, a bromine compound may be used as a catalyst aid. Examples of the heavy metal in the heavy metal compound include cobalt, manganese, nickel, chromium, zirconium, copper, lead, hafnium, cerium, and the like. These can be used alone or in combination. In particular, it is preferable to use a combination of cobalt and manganese.
• Such heavy metal compounds include, for example, acetates, nitrates, acetyl acetonate salts, naphthenates, stearates, bromides, etc., and particularly preferred are acetates and bromides.
• bromine compound examples include inorganic bromine compounds such as molecular bromine, hydrogen bromide, sodium bromide, potassium bromide, cobalt bromide, and manganese bromide, and methyl bromide and methyl bromide. And organic bromine compounds such as bromoform, benzyl bromide, bromomethyltoluene, dibromoethane, tribromoethane and tetrabromoethane. These bromine compounds are also used alone or as a mixture of two or more.
• inorganic bromine compounds such as molecular bromine, hydrogen bromide, sodium bromide, potassium bromide, cobalt bromide, and manganese bromide, and methyl bromide and methyl bromide.
• organic bromine compounds such as bromoform, benzyl bromide, bromomethyltoluene, dibromoethane, tribromoethane and tetrabromoethane.
• the catalyst used for oxidizing the alkyl aromatic compound A include a combination of cobalt, manganese, and bromine, and a combination of cobalt acetate, manganese acetate, and hydrogen bromide is particularly preferable. Better ,.
• the catalyst capable of combining the heavy metal compound and the bromine compound is used in an amount of 0.05 to 10 moles, preferably 0.1 to 5 moles of bromine atoms to 1 mole of heavy metal atoms. It is desirable to have a range power.
• Such a catalyst is generally used in a concentration of 10 to 10,000 ppm, preferably 100 to 3000 ppm as a heavy metal concentration in the reaction solvent.
• the reaction temperature of the oxidation of the alkyl aromatic compound A in the reactor 11 in the figure is usually 140 to 230 ° C, preferably 150 to 210 ° C, more preferably 170 to 200 ° C. ° C. If the reaction temperature is too low, the reaction rate decreases, and if the reaction temperature is too high, the amount of acetic acid solvent lost by combustion tends to increase, which is not preferable.
• the reaction pressure must be at least a pressure at which the mixture can maintain a liquid phase at the reaction temperature, and must be a pressure exceeding normal pressure. Specifically, 0.2 to 5 MPa (absolute pressure) is preferable, and 0.4 to 3 MPa (absolute pressure) is more preferable.
• the reaction is usually carried out continuously, and the reaction time (average residence time) is preferably from 30 to 300 minutes, particularly preferably from 40 to 150 minutes. If the reaction time is too short, the reaction may be inadequate and the desired product quality may not be obtained. If the reaction time is too long, the combustion of acetic acid increases, which is not economical. Further, it is not economical in that the capacity of the reactor 11 is increased.
• the water concentration in the reaction solvent can be adjusted, for example, by purging a part of the condensate O obtained by condensing the reaction gas N generated in the reactor 11 to the outside of the system.
• the above-mentioned reactor 11 is preferably a tank with a stirrer, but may be a bubble column type which does not necessarily need to have a stirrer.
• a supply port for the molecular oxygen-containing gas B is provided at a lower portion of the reactor 11, and a condenser 11a may be provided at an upper portion of the reactor 11 if necessary.
• the molecular oxygen-containing gas B supplied from the lower part is used for the oxidation reaction of the alkyl aromatic compound A, and then is extracted from the reactor 11 as a reaction gas E accompanied by a large amount of acetic acid vapor.
• the condensate O mainly composed of acetic acid is condensed and separated in the condenser 11a, and then discharged as exhaust gas P.
• the condensate O contains water, part of which is purged out of the system for adjusting the water content in the system, and the rest is refluxed to the reactor 11.
• the exhaust gas P may be branched into two streams, one of which is discharged outside the system, and the other of which is continuously circulated and supplied to the reactor 11.
• the reaction mixture is usually at a lower temperature than the first reaction zone, and when the alkyl aromatic compound A is noxylene, the first reaction zone is generally used.
• the second reaction zone maintained at a lower temperature of 5 to 20 ° C., this refers to the additional oxidation treatment (hereinafter, referred to as “low temperature additional oxidation”) without supplying the alkyl aromatic compound A.
• the pressure at the time of the low-temperature additional oxidation must be at least a pressure at which the internal mixture can maintain a liquid phase at the reaction temperature, and is preferably 0.2 to 5 MPa (absolute pressure).
• the low-temperature reoxidation reaction is preferably performed continuously, and the reaction time is preferably 5 to 120 minutes. Further, the above low-temperature re-oxidation may be performed twice or more. Furthermore, if necessary, the third reaction zone may be subjected to additional oxidation at a higher temperature than the first and second reaction zones (hereinafter, referred to as “high-temperature additional oxidation”).
• the molecular oxygen-containing gas B supplied for performing the low-temperature re-oxidation or the high-temperature re-oxidation may be air, oxygen diluted with an inert gas, or oxygen-enriched gas, as in the first reaction zone. Air or the like is used. Practically, air is preferably used. Further, the supply amount is about 1Z10000-1Z5, more preferably lZioo-lZio, of the amount supplied to the oxidation reaction performed in the first reaction zone. In addition, a reactor of the same type as the first reaction zone can be used as the second reaction zone for performing the low-temperature re-oxidation reaction or the third reaction zone for performing the high-temperature re-oxidation reaction.
• the aromatic carboxylic acid slurry C obtained as the reaction mixture is not subjected to the aromatic solid carboxylic acid slurry C in the following (B) solid-liquid separation step.
• crystallization treatment Prior to recovering the aromatic carboxylic acid crystals, crystallization treatment may be performed under a pressure higher than normal pressure, if necessary.
• the aromatic carboxylic acid slurry C is cooled by depressurizing and evaporating the aromatic carboxylic acid slurry C at a pressure lower than that in the above-mentioned oxidation step, whereby the aromatic carboxylic acid dissolved in the solvent is further precipitated, and the aromatic carboxylic acid slurry C is removed. The recovery of acid crystals is increased.
• the separation operation temperature obtained in the above (B) solid-liquid separation step decreases.
• the temperature of the separated mother liquor and the separated cake is also reduced, so that the effect of the present technology is reduced.
• the final aromatic carboxylic acid slurry C is maintained at a pressure higher than normal pressure while maintaining the temperature at a high temperature, specifically, 110 ° C-oxidation reaction. High temperature It is necessary to keep it.
• the aromatic carboxylic acid slurry C is solidified by the solid-liquid separation device 12 into an aromatic carboxylic acid cake E and a mother liquor F under a pressure higher than normal pressure. Separate the liquid.
• the mother liquor F which has been separated by the solid-liquid separator 12, is sent to the mother liquor recycling step (C) while maintaining the pressure above normal pressure.
• the pressure higher than the normal pressure is a pressure higher than the vapor pressure of the aromatic carboxylic acid slurry C at the mother liquor temperature at the mother liquor.
• the pressure at which the slurry containing crystals of the aromatic carboxylic acid produced is solid-liquid separated into the aromatic carboxylic acid and the mother liquor is as follows:
• the pressure must be higher than the normal pressure, specifically, 0.2 to 1.5 MPa (absolute pressure) is more preferable, and 0.3 to 1.2 MPa (absolute pressure) is more preferable. . If the pressure is too low, the effective component dissolved in the separated mother liquor is small, so that the effect of adopting the present invention is small.
• the upper limit is (A) the pressure of the obtained slurry.
• the drying device 15 Before the separated aromatic carboxylic acid cake E is dried by the drying device 15, it is desirable that impurities and by-products and the like are washed with the washing liquid Q in the washing device 13.
• acetic acid, water, or the like is used as the cleaning liquid Q.
• the solid-liquid separation process in the solid-liquid separation device 12 and the washing process in the washing device 13 are combined as shown in a broken line in FIG.
• the use of the apparatus 14 simplifies the process and is more desirable.
• the solid-liquid separation / washing device 14 capable of performing the two steps collectively as described above include, for example, a screen bowl type centrifuge, a rotary vacuum filter, and a horizontal belt filter.
• a screen bowl type centrifuge having excellent heat resistance even in a high temperature range close to the temperature of the oxidation step (A) is preferable.
• the obtained washed cake R is dried in a drying device 15 to remove the adhering liquid remaining on these cakes to obtain aromatic carboxylic acid crystals G.
• the drying device 15 may be composed of a plurality of devices. Among them, as a device for removing at least a part of the above-mentioned adhesion liquid, these cakes and the adhesion liquid adhering thereto are brought to a lower pressure state. It is desirable to use an apparatus that releases and evaporates the adhered liquid adhering to these cakes by the internal energy possessed by the transfer.
• depressurization evaporation refers to the rapid transition of a liquid in a high pressure state to a low pressure state in which the temperature before the transition is equal to or higher than the boiling point at the pressure after the transition. It means that it is cooled to below its boiling point and Z or partly evaporates due to its internal energy. It is more desirable that as much of the deposited liquid as possible can be evaporated by the above-mentioned decompression evaporation. However, if drying is insufficient with only the decompression evaporation, further heating is required.
• the washing effluent S after washing the above-mentioned aromatic carboxylic acid cake E contains an acetic acid solvent, the above-mentioned aromatic carboxylic acid and the like. For this reason, it is desirable to use the recycled mother liquor H together with the recycled mother liquor H alone or by returning it to the above-mentioned reactor 11 because the yield of the entire production process is improved.
• the mother liquor F is branched into a recycling mother liquor H and a purge mother liquor I while maintaining a pressure higher than the normal pressure.
• the phrase "while maintaining a pressure higher than the normal pressure” refers to a pressure level at which the operating pressure in the (B) solid-liquid separation step is substantially maintained.
• the ratio of the branch to the recycled mother liquor H and the purge mother liquor I can be adjusted arbitrarily according to the situation of the whole manufacturing process. — 95%, preferably 60-90%, where it is desirable that the recycled mother liquor H and the purge mother liquor I maintain a pressure exceeding normal pressure (B) It is more desirable that the operating pressure is substantially maintained.
• the recycled mother liquor G and the washing effluent S are maintained at (B) the operating pressure in the solid-liquid separation step, whereby the recycled mother liquor H is not substantially cooled by decompression evaporation (B).
• energy for pressurizing and heating again to satisfy predetermined oxidation reaction conditions can be saved, and energy (oxidation reaction heat) generated in the oxidation reaction can be effectively recovered and used from the distillate steam.
• the amount of generated steam can be increased.
• the mother liquor F contains The aromatic carboxylic acid and other active components are more dissolved than in the case where solid-liquid separation is performed under normal temperature and normal pressure conditions. Therefore, in the purge mother liquor I from which the mother liquor F is branched, an aromatic carboxylic acid is precipitated and recovered in the (D) concentration step. If the operation of concentrating the purged mother liquor I all at once until a residue is obtained, the dissolved aromatic carboxylic acid and other effective components are almost mixed into the residue, and these can be recovered. And reduce productivity.
• the concentration step becomes a two-stage concentration power
• the aromatic carboxylic acid is precipitated in the first concentration treatment
• the precipitated aromatic carboxylic acid is recovered
• the mother liquor after the recovery of the aromatic carboxylic acid is added to the mother liquor.
• a method in which the second-stage concentration treatment is performed to evaporate and recover the solvent component is preferable.
• the purge mother liquor I is decompressed and evaporated to perform a first-stage concentration treatment to partially evaporate a solvent component.
• the solid precipitated by the eye concentration treatment is collected.
• the mother liquor from which the aromatic carboxylic acid has been separated by this recovery is subjected to a second-stage concentration treatment to evaporate the remaining solvent components and recover the solvent.
• the mother liquor F force also maintains the operating temperature of the (B) solid-liquid separation process by maintaining the operating pressure of the (B) solid-liquid separation process until the purge mother liquor I and the recycled mother liquor are branched. It is desirable to do.
• the mother liquor F is also removed from the recycled mother liquor H by V, and the remaining purge liquor I is vaporized from the mother liquor at the temperature of the purge liquor I.
• the first-stage concentration and cooling treatment for decompression evaporation was performed, and a part of the solvent component was evaporated as solvent vapor T, concentrated and cooled.
• the cooling temperature corresponds to the boiling point of the mother liquor at the pressure after the pressure is released.
• the amount of the solvent evaporated by the first-stage concentration is usually 10 to 50% by weight, preferably 20 to 40% by weight.
• the amount to be evaporated is too large, impurities which affect the quality of the product which cannot be obtained only with the active ingredient are undesirably deposited. On the other hand, if the amount is too small, the recovered amount of the active ingredient is small and the effect is not sufficient.
• the operating pressure of the decompression evaporator 16 (the operating pressure of the first stage concentration) is equal to or lower than the vapor pressure of the mother liquor at the temperature of the purge mother liquor I for efficient concentration. It is desirable that the pressure be as follows. Specifically, 0.05MPa (absolute pressure)-the temperature of the purge mother liquor I (Preferably 0.08 MPa (absolute pressure) -one pressure below the vapor pressure of the mother liquor at the temperature of the purge mother liquor I). If the operating pressure is too low, the concentration and cooling undesirably lead to the precipitation of impurities that affect the quality of the product, which is not only the active ingredient.
• the pressurized state pressurized in the oxidation step (A) is maintained by the purge mother liquor, and the pressurized state is used at the time of concentration, so that the purge mother liquor I can be used without heating or the like. Can be evaporated, and efficient concentration can be performed.
• the solvent vapor T evaporated during the concentration is mainly composed of acetic acid as a solvent component.
• the solvent vapor T is cooled and returned to a liquid and then directly returned to the (A) oxidizing step, or after being treated in a dehydrating apparatus 19 such as distillation.
• the recovered acetic acid M may be indirectly returned to (A) the oxidizing step. These may be used as the washing liquid Q.
• the solid content recovery device 17 separates the separated mother liquor V from the separated mother liquor V to obtain the solid W containing the precipitate by the above-described pressureless evaporation.
• a solid content recovery device 17 include a filter, a centrifuge, a cyclone, and a thickener.
• the solid W is an active ingredient such as the above-mentioned aromatic carboxylic acid or an intermediate thereof, and by returning this to the reactor (A) in the oxidation step, productivity can be improved. I can do it.
• the separated mother liquor V is introduced into the solvent evaporator 18, and is heated to further evaporate the remaining solvent components to be concentrated.
• the solvent component is evaporated with a heat medium such as steam.
• the separated mother liquor V is introduced into a solvent evaporator 18 composed of a tank, and steam is used as a heat source from the outside under an operating pressure of 0.03 MPa (absolute pressure) to 0.15 MPa (absolute pressure) to remove the solvent component.
• Cook and concentrate 10 to 40 times the concentration of high boiling components such as catalyst components, by-products and impurities.
• the concentrated liquid may be continuously or indirectly extracted from the solvent evaporator 18, and may be recovered by evaporating the solvent component. Since the solvent vapor X evaporated by this process is mainly composed of acetic acid, which is a solvent component, it is cooled and cooled similarly to the above-mentioned solvent vapor T. After returning to the liquid, (A) the force to return to the oxidizing step directly, or the acetic acid M indirectly as recovered acetic acid M after treatment with a dehydrator 19 such as distillation to remove the oxidizing water L The process may be returned to the oxidizing process. Similarly, these may be used as the cleaning liquid Q. In the above dehydration treatment, the solvent vapor T and the solvent vapor X may be integrated.
• the residual window which did not evaporate, the by-products of the aromatic sulfonic acid, the catalyst used in the reactor 11 and the like were present. include. It is desirable that this residue be subjected to an appropriate treatment such as extraction to recover the catalyst component, and that the recovered catalyst be regenerated and reused in the catalyst regeneration step.
• the energy of the mother liquor is utilized for part of the concentration when the mother liquor is concentrated, so that the useful component contained in the purge mother liquor can be recovered. Can be raised. Further, by recycling the mother liquor at a high temperature and a high pressure to the oxidation step of converting the alkyl aromatic compound to the aromatic carboxylic acid, the energy required for achieving the predetermined reaction conditions can be reduced. The generated energy can be used effectively.
• the condensate obtained from each condenser was integrated and refluxed to the oxidation reactor, and a part of the condensate was withdrawn so that the concentration of water in the mother liquor of the slurry withdrawn was 10% by weight.
• 2.55 parts by weight of crude terephthalic acid, 3.79 parts by weight of mother liquor, and cobalt Z manganese Z bromine concentration in the reaction mother liquor were 300Z300Z100. 0 ppm by weight and the slurry concentration was 35% by weight.
• the temperature of the low-temperature additional acid reactor was withdrawn and supplied to a screen bowl type centrifugal separator to perform solid-liquid separation.
• the operating pressure was 1.18 MPa (absolute pressure).
• the centrifuged crude terephthalic acid cake is washed with 2.99 parts by weight of acetic acid on the screen in a screen bowl-type centrifuge, and then discharged. Thus, 1.56 parts by weight of crude terephthalic acid crystals were obtained.
• the separated mother liquor recovered by the solid-liquid separation diverges 20% of the purged mother liquor while maintaining the solid-liquid separation operation pressure, and the remaining 80% of the separated mother liquor is recycled together with the washing wastewater generated in the above washing. 6. Recycled as 24 parts by weight to the Sidani reactor (Mother liquor recycling rate 80%

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Crystallography & Structural Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=34835951

Family Applications (1)

Country Status (2)

Cited By (9)

Families Citing this family (1)

Citations (2)

• 2005
  • 2005-02-04 CN CN2005800038402A patent/CN1914145B/zh active Active
  • 2005-02-04 WO PCT/JP2005/001683 patent/WO2005075403A1/ja active Application Filing

Patent Citations (2)

Also Published As

Similar Documents

Legal Events