WO2022054783A1 - Procédé de récupération d'acide acétique - Google Patents

Procédé de récupération d'acide acétique Download PDF

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WO2022054783A1
WO2022054783A1 PCT/JP2021/032795 JP2021032795W WO2022054783A1 WO 2022054783 A1 WO2022054783 A1 WO 2022054783A1 JP 2021032795 W JP2021032795 W JP 2021032795W WO 2022054783 A1 WO2022054783 A1 WO 2022054783A1
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acetic acid
cellulose acetate
membrane
aqueous solution
acid aqueous
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PCT/JP2021/032795
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English (en)
Japanese (ja)
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秀人 松山
直之 福井
知志 井本
秀隆 早水
和史 竹田
重典 松井
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国立大学法人神戸大学
株式会社ダイセル
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Publication of WO2022054783A1 publication Critical patent/WO2022054783A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/58—Multistep processes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • 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
    • C07C51/44—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation by distillation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C53/00—Saturated compounds having only one carboxyl group bound to an acyclic carbon atom or hydrogen
    • C07C53/08—Acetic acid
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B3/00—Preparation of cellulose esters of organic acids
    • C08B3/06—Cellulose acetate, e.g. mono-acetate, di-acetate or tri-acetate

Definitions

  • This disclosure relates to a method for recovering acetic acid and a method for producing cellulose acetate using the same.
  • This disclosure claims the priority of Japanese Patent Application No. 2020-150254 filed in Japan on September 8, 2020, the contents of which are incorporated herein by reference.
  • Cellulose acetate has excellent chemical resistance, heat resistance, and flame retardancy, and is therefore used in various applications such as liquid crystal optical films, tobacco filters, acetate fibers, photographic films, fibrous plastics, and filter membranes.
  • a method for producing cellulose acetate a method of reacting cellulose with an acetylating agent in an aqueous acetic acid solution is known. Further, after obtaining cellulose acetate as a product from the reaction mixture, acetic acid is recovered from the residual liquid and reused.
  • the residual liquid contains water and cellulose acetate in addition to acetic acid, but it is difficult to separate acetic acid by distillation because water and acetic acid have similar boiling points. Therefore, an organic solvent having a large difference in boiling point from acetic acid is used to separate the extract liquid phase mainly containing acetic acid and the organic solvent into the extraction liquid phase mainly containing water, and then the extract liquid phase is prepared.
  • Acetic acid was recovered by separating the organic solvent and acetic acid by subjecting to distillation.
  • the problem is that the efficiency of extracting acetic acid into the extract phase is low, and a large amount of acetic acid cannot be recovered and is discarded.
  • the cellulose acetate dissolved in the extract phase precipitates at the bottom of the column, causing poor liquid feeding and heat transfer, and maintaining stable operation of the distillation column. Becomes difficult. Therefore, cellulose acetate is removed as a non-volatile component by gasifying the extract phase using an evaporator or the like before charging the extract phase into the distillation column.
  • Patent Document 1 describes that the residual liquid is subjected to nanofiltration treatment to remove cellulose acetate, and the residual liquid to be subjected to the filtration treatment is lignosulfonates, which is one of the surfactants.
  • the surfactant When added, the surfactant does not permeate the filter membrane and exerts an effect of suppressing the formation of a layer containing a high concentration of cellulose acetate on the surface of the filter membrane. Therefore, it is described that high-purity acetic acid can be obtained. However, even with this method, a large amount of acetic acid could not be recovered and was discarded.
  • an object of the present disclosure is to provide a method for recovering acetic acid, which can reduce the loss of acetic acid, improve the recovery rate, and has an excellent steam saving effect.
  • Another object of the present disclosure is to provide a method for efficiently recovering high-purity acetic acid and reusing it to produce cellulose acetate by a method having an excellent steam-saving effect.
  • the concentration of dissolved cellulose acetate in the acetic acid aqueous solution is adjusted by membrane separation treatment, it is superior in steam saving effect as compared with the conventional method of removing cellulose acetate as a non-volatile component by gasification. Even if the extract phase having a reduced concentration of dissolved cellulose acetate is charged into the distillation column as it is, acid cellulose does not precipitate at the bottom of the column, causing poor liquid feeding and heat transfer, and the extract phase can be used as the liquid phase. It was found that if the distillation column is charged as it is, the separation efficiency is improved as compared with the case where the distillation column is charged in a gasified state. This disclosure has been completed based on these findings.
  • the present disclosure is a method for recovering acetic acid from an acetic acid aqueous solution in which cellulose acetate is dissolved.
  • Step 1 of adjusting the concentration of cellulose acetate dissolved in an acetic acid aqueous solution to 1 to 10000 ppm,
  • Step 2. Provided is a method for recovering acetic acid, which comprises a step 3 of subjecting the extract phase to distillation to recover acetic acid.
  • step 1 the acetic acid aqueous solution in which cellulose acetate is dissolved is subjected to a membrane separation treatment using a precision filtration membrane having a pore size of 0.01 to 10 ⁇ m, and is dissolved in the acetic acid aqueous solution as a membrane permeate.
  • a method for recovering acetic acid which is a step of obtaining an acetic acid aqueous solution having a cellulose acetate concentration of 1 to 10,000 ppm.
  • step 1 the acetic acid aqueous solution in which cellulose acetate is dissolved is subjected to a membrane separation treatment using a precision filtration membrane having a pore size of 0.01 to 10 ⁇ m, and the obtained membrane permeation liquid is further back-permeated.
  • a method for recovering acetic acid which is a step of obtaining an acetic acid aqueous solution having a cellulose acetate concentration of 1 to 10000 ppm dissolved in an acetic acid aqueous solution as a membrane permeate in a membrane separation treatment using a membrane.
  • the present disclosure also provides a method for recovering acetic acid using a reverse osmosis membrane having a surface layer containing a polymer having a phosphorylcholine group (hereinafter, may be referred to as "PC polymer") as the reverse osmosis membrane. ..
  • the present disclosure is also a method for producing cellulose acetate by acetylating cellulose in an aqueous acetic acid solution to obtain cellulose acetate.
  • the cellulose acetate is recovered from the reaction solution after the acetylation, and the acetic acid is obtained from the residual solution.
  • a method for producing cellulose acetate in which acetic acid is recovered by the recovery method of the above and reused as a raw material for the acetic acid aqueous solution.
  • the extraction step is compared with the conventional method (that is, a method in which the extract phase is gasified after extraction with an organic solvent to reduce the concentration of dissolved cellulose acetate, and then subjected to a distillation treatment).
  • the extraction rate of acetic acid can be improved, and the recovery rate of acetic acid can be improved (resource saving effect).
  • the acetic acid recovered by the above method can be reused for the production of cellulose acetate.
  • the distillation step since it can be charged into the distillation column in the liquid phase, the separation efficiency is excellent, and even if the reflux ratio is lowered, acetic acid having the same purity as the conventional one can be recovered. Furthermore, if the concentration of dissolved cellulose acetate in the acetic acid aqueous solution is reduced by the membrane separation treatment, the enormous energy required for gasification can be reduced (steam saving effect).
  • FIG. 1 It is a schematic flow chart which shows an example of the acetic acid recovery method of this disclosure.
  • the figure which shows the relationship between the operation time of the membrane separation process and the circulation flow rate of the reverse osmosis membrane (0), the reverse osmosis membrane (1) provided with the surface layer containing PC polymer, and the reverse osmosis membrane (1) after alkaline cleaning. be.
  • the relationship between the operation time of the membrane separation treatment and the rate of decrease in the circulating flow rate of the reverse osmosis membrane (0), the reverse osmosis membrane (1) having a surface layer containing a PC polymer, and the reverse osmosis membrane (1) after alkaline cleaning is shown. It is a figure.
  • the acetic acid recovery method of the present disclosure is a method of recovering acetic acid from an acetic acid aqueous solution in which cellulose acetate is dissolved, and includes the following steps 1 to 3.
  • Step 1 Adjust the concentration of acetic acid cellulose dissolved in the acetic acid aqueous solution to 1 to 10000 ppm
  • Step 2 Bring the acetic acid aqueous solution having a dissolved acetic acid cellulose concentration of 1 to 10000 ppm into contact with an organic solvent to mainly mix acetic acid and the organic solvent.
  • Step 3 Separation of the extract phase containing and the extraction residue phase mainly containing water
  • Step 3 The step of subjecting the extract phase to distillation to recover acetic acid.
  • Step 1 Adjusting the concentration of cellulose acetate dissolved in the acetic acid aqueous solution
  • Step 1 is a step of adjusting the concentration of cellulose acetate dissolved in the acetic acid aqueous solution to 1 to 10000 ppm.
  • the upper limit of the cellulose acetate concentration is preferably 5000 ppm, more preferably 3000 ppm, still more preferably 2000 ppm, still more preferably 1500 ppm, still more preferably 1250 ppm, particularly preferably 1000 ppm, most preferably 500 ppm, and particularly preferably 100 ppm.
  • the lower limit of the cellulose acetate concentration is preferably 10 ppm.
  • acetic acid aqueous solution (a) having a dissolved cellulose acetate concentration in the above range is obtained.
  • the acetic acid aqueous solution (a) is subjected to the subsequent step 2 (extraction step).
  • the acetic acid recovery method of the present disclosure since the acetic acid aqueous solution (a) to be subjected to the extraction step contains the dissolved cellulose acetate concentration in the above range, the effect of improving the extraction efficiency can be obtained by the surface active effect of the dissolved cellulose acetate. ..
  • the acetic acid aqueous solution (a) contains 1 to 10000 ppm of soluble cellulose acetate, but may also contain a soluble component, for example, an inorganic salt (for example, magnesium sulfate or the like). ..
  • the method for adjusting the concentration of cellulose acetate dissolved in the acetic acid aqueous solution is not particularly limited, and examples thereof include a membrane separation treatment method and a distillation treatment method. Among the above methods, the membrane separation treatment method is preferable because it is excellent in steam saving effect.
  • a membrane separation treatment using a microfiltration membrane having a pore size of 0.01 to 10 ⁇ m (preferably 1 to 10 ⁇ m) is preferable.
  • a large amount of insoluble cellulose acetate is contained together with dissolved cellulose acetate in the acetic acid aqueous solution which is the residual liquid after the production of cellulose acetate (the concentration of insoluble cellulose acetate is, for example, 100 ppm or more), but the pore size is 0.01.
  • the concentration of insoluble cellulose acetate is, for example, 100 ppm or more
  • the pore size is 0.01.
  • the membrane separation process can be performed using a filtration device equipped with a filtration membrane module.
  • the filter membrane module is not particularly limited as long as it has a configuration capable of separating the membrane permeate that has permeated the filter membrane and the membrane concentrate that does not permeate the filter membrane.
  • the filtration membrane module examples include a spiral type filtration membrane module in which a filtration membrane is wound around a water collecting pipe.
  • the material of the filter membrane include polyamide, polysulfone, cellulose acetate and the like, and among these, polyamide such as aromatic polyamide and crosslinked aromatic polyamide is preferable.
  • a membrane separation treatment by a cross-flow filtration method is preferable.
  • the membrane separation treatment can be performed while preventing a decrease in the filtration rate.
  • the cross-flow filtration method the water to be treated is flowed parallel to the surface of the filtration membrane, and a part of the water to be treated is filtered on the side of the flow of the water to be treated while preventing the filtration membrane from being contaminated due to the deposition of the filter slag. It is a method.
  • Membrane separation using a filtration membrane is preferably performed in the range of, for example, 30 to 50 ° C, preferably 35 to 45 ° C.
  • the filtration pressure for membrane separation using a filtration membrane is, for example, about 0.001 to 6.0 MPaG, preferably 0.01 to 5.0 MPaG, and particularly preferably 0.1 to 4.0 MPaG.
  • the circulation amount of the liquid flowing through the membrane surface of the membrane separation using the filtration membrane is, for example, 10 to 40 L / min, preferably 15 to 30 L / min, particularly preferably 20 to 25 L / min. Is.
  • the circulation amount is, for example, 5 to 22 L / min, preferably 6 to 17 L / min, and particularly preferably 8 to 12 L / min. If the size of the membrane module is different, the circulation flow rate is also changed according to the above.
  • the membrane separation operation using the membrane is repeated until the concentration of dissolved cellulose acetate in the membrane permeate reaches the above range by using a circulating membrane filtration method or the like.
  • the membrane separation treatment using a reverse osmosis membrane may be further performed.
  • the membrane permeate obtained through the membrane separation treatment using the reverse osmosis membrane has a dissolved cellulose acetate concentration in the range of 1 to 10000 ppm. ..
  • the membrane permeation liquid is a liquid that has passed through the reverse osmosis membrane
  • the membrane concentrate is a liquid that has not passed through the reverse osmosis membrane.
  • the dissolved cellulose acetate is mainly contained in the membrane concentrate.
  • MPC polymer 2-methacryloyloxyethyl phosphorylcholine
  • a reverse osmosis membrane including a surface layer containing a PC polymer can be prepared, for example, by passing an aqueous solution of the PC polymer through the reverse osmosis membrane.
  • the PC polymer concentration in the PC polymer aqueous solution is, for example, 100 to 3000 ppm, preferably 300 to 2000 ppm or less, and particularly preferably 500 to 1000 ppm.
  • the circulation amount of the liquid flowing through the membrane surface of the reverse osmosis membrane provided with the surface layer is the same as described above.
  • the reverse osmosis membrane provided with the surface layer can maintain the effect of suppressing the adhesion of soluble cellulose acetate to the surface even in the presence of an alkaline chemical or after contact with the alkaline chemical. That is, the reverse osmosis membrane provided with the surface layer has excellent alkali resistance.
  • the reverse osmosis membrane provided with the surface layer has excellent durability, and the surface layer is not damaged even after 100 hours of use.
  • the polymer constituting the surface layer does not permeate the reverse osmosis membrane, the polymer does not mix with the acetic acid to be recovered.
  • Step 2 is a step of bringing the acetic acid aqueous solution (a) into contact with an organic solvent to separate the extract liquid phase mainly containing acetic acid and the organic solvent and the extraction liquid phase mainly containing water.
  • the acetic acid recovery method of the present disclosure since the acetic acid aqueous solution (a) applied to the extraction step contains the dissolved cellulose acetate concentration in the above range, high extraction efficiency is realized by the surface active effect of the dissolved cellulose acetate. ..
  • the organic solvent has a boiling point lower than the boiling point of acetic acid (for example, 25 ° C. or higher, preferably 30 ° C. or higher, preferably 35 ° C. or higher), and has high solubility of acetic acid. Moreover, it is preferable to use a solvent having low solubility in water.
  • the organic solvent include aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic hydrocarbons such as n-hexane, cyclohexane, heptane, octane and nonane; ethyl acetate, n-amyl acetate and cyclohexyl acetate.
  • Esters such as isoamyl propionate and methyl benzoate; halogenated hydrocarbons such as chloroform, carbon tetrachloride and chlorbenzene; ethers such as 1,2-dimethoxyethane and dimethyl ether and the like. These can be used alone or in combination of two or more.
  • a mixed solvent of an ester such as ethyl acetate (particularly preferably an acetate) and an aromatic hydrocarbon such as benzene is preferable, and the mixing ratio of the ester and the aromatic hydrocarbon (the former / the latter).
  • the weight ratio is, for example, 5/95 to 95/5, preferably 20/80 to 90/10, particularly preferably 40/60 to 85/15, and most preferably 55/45 to 85/15.
  • the amount of the organic solvent used is about 1.0 to 5.0 times (volume ratio) the amount of the acetic acid aqueous solution (a) used.
  • an apparatus is not particularly limited, and examples thereof include a known method using an extraction apparatus such as an extraction tower.
  • extraction apparatus such as an extraction tower.
  • extraction tower extraction of commonly used types such as mixer setra type extraction tower, perforated plate type, packed tower type, baffle tower type, vibrating perforated plate type, stirring and mixing type, pulsating filling type, centrifugal extraction type and the like. Equipment etc. are included.
  • the acetic acid aqueous solution (a) and the organic solvent come into countercurrent contact inside the extraction device.
  • the contact temperature between the acetic acid aqueous solution (a) and the organic solvent is, for example, in the range of 20 to 60 ° C, preferably 30 to 50 ° C.
  • the contact time is, for example, about 0.1 to 10 hours.
  • the contact between the acetic acid aqueous solution (a) and the organic solvent can be performed under normal pressure, pressure, or reduced pressure, and the gauge pressure is, for example, about -30 to 30 kPa.
  • the extraction operation can be performed intermittently or continuously. If the extraction effect is insufficient, the extraction operation can be repeated.
  • the extraction rate of acetic acid in the acetic acid aqueous solution (a) into the extract phase can be increased, and the water separation / removal efficiency can be improved.
  • the extract phase obtained in this step mainly contains acetic acid and the organic solvent, and the content of water is, for example, 15% by weight or less, preferably 10% by weight or less.
  • the cellulose acetate content is 200 ppm or less (preferably 150 ppm or less).
  • the liquid phase can be used as it is even if it is directly subjected to the distillation step (for example, without providing a gasification step or the like). Even if it is charged in the distillation column), it is possible to suppress the precipitation of cellulose acetate at the bottom of the column, and it is possible to maintain the safe operation of the distillation column.
  • Step 2' Extraction step 2
  • the membrane concentrate obtained through the membrane separation treatment of Step 1 contains water, acetic acid, and a large amount of dissolved cellulose acetate.
  • the membrane concentrate was subjected to the extraction step in the same manner as the acetic acid aqueous solution (a) which is a membrane permeate, and the obtained extract phase (containing acetic acid, the organic solvent used for extraction, and a large amount of dissolved cellulose acetate). Is gasified using an evaporator or the like, cellulose acetate can be separated and removed as a non-volatile component, and an aqueous acetate solution (a') having an extremely low concentration of dissolved cellulose acetate can be obtained.
  • the obtained acetic acid aqueous solution (a') can also be subjected to the subsequent steps in the same manner as the acetic acid aqueous solution (a) to recover high-purity acetic acid.
  • Step 3 is a step of distilling the extract phase obtained through step 2 and the gas obtained through step 2'to recover acetic acid.
  • the extract phase obtained through step 2 and the gas obtained through step 2' are subjected to distillation using a distillation column, and acetic acid and an organic solvent are used by utilizing the difference in boiling point.
  • High-purity acetic acid is recovered by separation. For example, when an organic solvent having a boiling point lower than that of acetic acid is used, the organic solvent is discharged to the outside of the system as a distillate, and high-purity acetic acid is recovered as a canned liquid.
  • distillation column examples include a shelf column, a packed column, and the like.
  • the tower top temperature is, for example, 20 to 120 ° C, preferably 30 to 100 ° C, and more preferably 40 to 80 ° C.
  • the pressure in the distillation column can be appropriately adjusted in the range of, for example, 0 to 60 kPa.
  • the distillation step may be composed of a single step or a combination of a plurality of steps.
  • the actual number of stages of the distillation column is, for example, 1 to 100 stages, preferably 10 to 100 stages, particularly preferably 30 to 80 stages, and most preferably 40 to 60 stages in terms of excellent separation efficiency.
  • the extract liquid phase obtained through step 2 can be charged into the distillation column as the liquid phase. Therefore, the energy cost can be reduced and the steam saving effect is excellent as compared with the case where all the preparation to the distillation column is performed in the gas phase.
  • high-purity acetic acid can be obtained as canned liquid.
  • the acetic acid concentration in the canned liquid is, for example, 90% by weight or more, preferably 98% by weight or more, and more preferably 99.9% by weight or more.
  • the acetic acid concentration in the distillate can be controlled by adjusting the reflux ratio.
  • the residual liquid after the production of cellulose acetate is supplied to the membrane separation device A by the line 1 and subjected to the membrane separation treatment.
  • the acetic acid aqueous solution (a) obtained by permeating the reverse osmosis membrane is introduced from line 2 to the top of the extraction column B-1.
  • the extract phase is charged into the distillation column C (in the liquid phase) from the line 4.
  • the extracted liquid phase is discharged from the line 13 to the outside of the system.
  • the extract phase is charged into the distillation column C, most of the organic solvent contained in the extract phase is cooled by the cooler D from the top of the column via the line 8 and introduced into the tank E from the line 9.
  • the upper layer liquid mainly contains an organic solvent and is discharged from the line 10 to the outside of the system. This can be reused as an organic solvent to be introduced into the extraction tower B-1 or B-2 again.
  • the lower layer liquid of the tank E mainly contains water and is discharged from the line 11 to the outside of the system. A part of the upper layer liquid of the tank E may be recycled to the distillation column C through the line 12 while remaining in the liquid phase. On the other hand, high-purity acetic acid is recovered as canned out liquid from the bottom of the distillation column C via the line 5.
  • the membrane concentrate that did not permeate the reverse osmosis membrane in the membrane separation device A is introduced from the line 14 to the top of the extraction tower B-2.
  • the organic solvent is introduced from line 15 to the bottom of the extraction tower B-2, and is in countercurrent contact with the membrane concentrate in the extraction tower B-2, and mainly contains acetic acid, an organic solvent, and an extract phase containing soluble cellulose acetate. It is separated into an extraction residual phase, which mainly contains water and soluble cellulose acetate.
  • the extract phase is introduced into the evaporator G from the line 16.
  • the extracted residual phase is discharged from the line 17 to the outside of the system.
  • the extract phase is evaporated in the evaporator G and separated into a vapor containing acetic acid and an organic solvent and an evaporation residual liquid containing soluble cellulose acetate, and the vapor containing acetic acid and an organic solvent is vaporized from line 18 into the distillation column C. It is prepared in.
  • the subsequent flow is the same as the extract phase charged in the distillation column C as a liquid phase.
  • the evaporation residue containing soluble cellulose acetate is discharged from the line 19 to the outside of the system.
  • the method for producing cellulose acetate of the present disclosure is a method for producing cellulose acetate by acetylating cellulose in an acetic acid aqueous solution to obtain cellulose acetate, in which cellulose acetate is recovered from the reaction solution after acetylation and the residual liquid thereof is recovered. Therefore, acetic acid is recovered by the above-mentioned acetic acid recovery method and reused as a raw material for the acetic acid aqueous solution.
  • the production of cellulose acetate includes, for example, the following steps 1 to 3.
  • Step 1 The cellulose raw material is dissociated and crushed, and then acetic acid or acetic acid containing a small amount of an acidic catalyst is sprayed to activate the cellulose.
  • Step 2 Activated cellulose.
  • Acetylation step 3 Purification step to obtain cellulose acetate by acetylating in an acetic acid aqueous solution
  • the reaction solution after acetylation contains insoluble cellulose acetate, soluble cellulose acetate, and acetic acid aqueous solution obtained by acetylation.
  • the acetic acid aqueous solution may contain other components other than acetic acid and water, such as an acetylating agent (for example, acetic anhydride) and an acidic catalyst (for example, sulfuric acid).
  • an acetylating agent for example, acetic anhydride
  • an acidic catalyst for example, sulfuric acid
  • the primary cellulose acetate obtained through the acetylation step can be hydrolyzed to obtain the secondary cellulose acetate having a desired degree of acetic acidation.
  • acetic acid is recovered from the reaction solution after the acetylation step and reused, so that the production cost of cellulose acetate can be reduced.
  • each configuration of the invention according to the present disclosure and combinations thereof are examples, and the configurations can be added, omitted, replaced, and changed as appropriate within the range not deviating from the gist of the invention according to the present disclosure. .. Further, the invention according to the present disclosure is not limited to the embodiments, but is limited only by the description of the scope of claims.
  • Example 1 [Membrane Separation Step-Extraction Step-Distillation Step] (Membrane separation process) 30% aqueous acetate solution (1) (soluble component: dissolved cellulose acetate 0.4%, inorganic salt 0.6%, insoluble component: 100 ppm) microfiltration membrane (MF film manufactured by PORTEX, pore size: 5 ⁇ m, material: polyethylene) ) was filtered to obtain a membrane permeate (1) (soluble component: dissolved cellulose acetate 0.4%, inorganic salt 0.6%, insoluble component: zero).
  • aqueous acetate solution (1) soluble component: dissolved cellulose acetate 0.4%, inorganic salt 0.6%, insoluble component: 100 ppm
  • microfiltration membrane MF film manufactured by PORTEX, pore size: 5 ⁇ m, material: polyethylene
  • the obtained extract phase was charged in the 24th stage from the top of the distillation column (older show 60 stages).
  • the amount of liquid charged was 233 g / h.
  • the tower top pressure is normal pressure, and the thermometer is the tower top (1st step from the top), 4th step, 8th step, 14th step, 18th step, 24th step, 28th step, 38th step from the top. It was installed in the eyes, the 44th stage, the 48th stage, the 54th stage, the 58th stage, and the reboiler liquid (BTM liquid).
  • the recirculation ratio (recirculation amount / (upper layer liquid amount + lower layer water amount)) was set to 0.6. Distillation was carried out under the above conditions to obtain high-purity acetic acid as a canned out liquid.
  • Example 2 [Membrane Separation Step-Extraction Steps 1, 2-Distillation Steps] (Membrane separation process)
  • the membrane permeate (1) obtained in the same manner as in Example 1 was used with a reverse osmosis membrane (2-inch membrane module, ES15 manufactured by Nitto Denko Co., Ltd., material: polyamide) at 40 ° C. and a circulation flow rate of 8 L / min. , Cross-flow filtration at an operating pressure of 2.4 MPaG to obtain a membrane permeate (3) (soluble component: dissolved cellulose acetate 20 ppm, inorganic salt 30 ppm, insoluble component: zero) and a membrane concentrate (1). ..
  • Example 2 The membrane concentrate (1) was subjected to S / F: 1.6 (v / v), extraction temperature: 40 ° C., superficial velocity: using an organic solvent (ethyl acetate: 75%, benzene: 25%). Under the condition of 0.4 cm / sec, countercurrent multi-stage extraction (actual number of extraction towers: 112 stages: 28 stages / section ⁇ 4 sections) was performed. The extraction operation was stable from beginning to end. As a result, an extract phase (2) containing cellulose acetate was obtained. Then, the obtained extract phase (2) was subjected to an evaporator (distillation rate: 99%) and gasified to obtain a gas (2) containing no cellulose acetate.
  • the obtained extract phase (1) was charged in the 24th stage from the top of the distillation column (older show 60 stages). The amount of liquid charged was 185 g / h. Further, the obtained gas (2) was charged from the 34th stage from the top. The amount of liquid charged was 615 g / h.
  • the tower top pressure is normal pressure, and the thermometer is the tower top (1st step from the top), 4th step, 8th step, 14th step, 18th step, 24th step, 28th step, 38th step from the top. It was installed in the eyes, the 44th stage, the 48th stage, the 54th stage, the 58th stage, and the reboiler liquid (BTM liquid).
  • the recirculation ratio (recirculation amount / (upper layer liquid amount + lower layer water amount)) was set to 0.65. Distillation was carried out under the above conditions to obtain high-purity acetic acid as a canned out liquid.
  • Example 3 [Membrane Separation Step-Extraction Step] An extract phase was obtained by performing (film separation step) and (extraction step) in the same manner as in Example 1 except that the superficial velocity was changed from 0.4 cm / sec to 0.6 cm / sec.
  • Example 1 Comparative Example 1
  • a 30% aqueous acetic acid solution (1) soluble component: dissolved cellulose acetate 0.4%, inorganic salt 0.6%, insoluble component: 100 ppm
  • the same (extraction step) was carried out to obtain an extract phase.
  • Comparative Example 2 [Extraction process] When the same as in Comparative Example 1 was applied except that the superficial velocity was changed from 0.4 cm / sec to 0.6 cm / sec, liquid separation failure occurred after significant cloudiness was observed in the extraction tower, and the operation was continued. I can no longer do it.
  • Preparation Example 1 (Preparation of reverse osmosis membrane having a surface layer containing MPC polymer) A 0.075% MPC polymer aqueous solution (2-methacryloyloxyethyl phosphorylcholine, manufactured by Nichiyu Co., Ltd.) was charged in a tank, and a reverse osmosis membrane (0) (2-inch membrane module) was charged at a flow rate of 1 mL / min for 30 minutes under normal temperature conditions. , ES15 manufactured by Nitto Denko Co., Ltd., material: polyamide), and the MPC polymer was adsorbed on the membrane surface to obtain a reverse osmosis membrane (1) having a surface layer containing the MPC polymer.
  • the reverse osmosis membrane (1) can maintain a constant circulation flow rate for a long period of time by dramatically suppressing the decrease in the circulation flow rate as compared with the reverse osmosis membrane (0). ..
  • the MPC polymer was adsorbed on the membrane surface (depth: 3 to 5 nm region) of the reverse osmosis membrane (1) before being subjected to the membrane separation treatment.
  • the reverse osmosis membrane (1) was subjected to alkaline cleaning using a pH 12 NaOH aqueous solution. Then, the reverse osmosis membrane (1) after alkaline washing was subjected to a membrane separation treatment in the same manner as described above, and the effect on the surface layer was confirmed. The results are shown in FIGS.
  • the elution of the MPC polymer present on the surface of the reverse osmosis membrane (1) was evaluated by the following method. That is, a 26 wt% aqueous acetic acid solution (phosphorus undetected) was used as a model solution, and the model solution was filtered using a reverse osmosis membrane (1) to obtain a permeate and a concentrate, which were contained in the permeate. The phosphorus concentration was quantified by ICP-AES. As a result, phosphorus was not detected in the permeate. From this, it was confirmed that the MPC polymer was hardly mixed in the recovered acetic acid.
  • a method for recovering acetic acid from an acetic acid aqueous solution in which cellulose acetate is dissolved Step 1 of adjusting the concentration of cellulose acetate dissolved in an acetic acid aqueous solution to 1 to 10000 ppm, Step 2.
  • a method for recovering acetic acid which comprises a step 3 of subjecting the extract phase to distillation to recover acetic acid.
  • step 1 the acetic acid aqueous solution in which cellulose acetate is dissolved is subjected to a membrane separation treatment using a precision filtration membrane having a pore size of 0.01 to 10 ⁇ m, and the concentration of cellulose acetate dissolved in the acetic acid aqueous solution as a membrane permeate.
  • step 1 an acetic acid aqueous solution in which cellulose acetate is dissolved is subjected to a membrane separation treatment using a precision filtration membrane having a pore size of 0.01 to 10 ⁇ m, and the obtained membrane permeate is further subjected to a back-penetration membrane.
  • the method for recovering acetic acid according to [1] which is a step of obtaining an acetic acid aqueous solution having a cellulose acetate concentration of 1 to 10000 ppm dissolved in the acetic acid aqueous solution as a membrane permeate by subjecting to the membrane separation treatment.
  • the organic solvent used in step 2 is a solvent having a boiling point lower than that of acetic acid, and is at least one selected from aromatic hydrocarbons, aliphatic hydrocarbons, esters, halogenated hydrocarbons, and ethers.
  • the organic solvent used in step 2 is a mixed solvent of an ester and an aromatic hydrocarbon, and the weight ratio of the ester to the aromatic hydrocarbon (the former / the latter) is 5/95 to 95/5.
  • the extraction step is compared with the conventional method (that is, a method in which the extract phase is gasified after extraction with an organic solvent to reduce the concentration of dissolved cellulose acetate, and then subjected to a distillation treatment).
  • the extraction rate of acetic acid can be improved, and the recovery rate of acetic acid can be improved (resource saving effect).
  • the acetic acid recovered by the above method can be reused for the production of cellulose acetate.
  • the distillation step since it can be charged into the distillation column in the liquid phase, the separation efficiency is excellent, and even if the reflux ratio is lowered, acetic acid having the same purity as the conventional one can be recovered. Furthermore, if the concentration of dissolved cellulose acetate in the acetic acid aqueous solution is reduced by the membrane separation treatment, the enormous energy required for gasification can be reduced (steam saving effect).

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Water Supply & Treatment (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Environmental & Geological Engineering (AREA)
  • Hydrology & Water Resources (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Biochemistry (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Polysaccharides And Polysaccharide Derivatives (AREA)

Abstract

L'invention fournit un procédé de récupération d'acide acétique qui permet de réduire une perte d'acide acétique et ainsi d'améliorer un taux de récupération, et qui présente d'excellents résultats d'économie de vapeur.　Selon le procédé de récupération d'acide acétique de l'invention, un acide acétique est récupéré à partir d'une solution aqueuse d'acide acétique dans laquelle un acétate de cellulose est dissous. Ce procédé inclut : une étape (1) au cours de laquelle la concentration en acétate de cellulose dissous dans la solution aqueuse d'acide acétique, est ajustée entre １ et １００００ｐｐｍ ; une étape (2) au cours de laquelle la solution aqueuse d'acide acétique dans laquelle la concentration en acétate de cellulose dissous est comprise entre １ et １００００ｐｐｍ, est mise en contact avec un solvant organique, et est séparée en phase liquide d'extraction contenant principalement l'acide acétique et le solvant organique, et en phase résiduelle d'extraction contenant principalement une eau ; et une étape (3) au cours de laquelle ladite phase liquide d'extraction est soumise à une distillation, et l'acide acétique est ainsi récupéré.
PCT/JP2021/032795 2020-09-08 2021-09-07 Procédé de récupération d'acide acétique WO2022054783A1 (fr)

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