CN1300088C - Method for recovering raw material, solvent and by-product in aromatic carboxylic acid production process - Google Patents
Method for recovering raw material, solvent and by-product in aromatic carboxylic acid production process Download PDFInfo
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- CN1300088C CN1300088C CNB2005100385607A CN200510038560A CN1300088C CN 1300088 C CN1300088 C CN 1300088C CN B2005100385607 A CNB2005100385607 A CN B2005100385607A CN 200510038560 A CN200510038560 A CN 200510038560A CN 1300088 C CN1300088 C CN 1300088C
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Abstract
A process for recovering starting materials, solvents and by-products from a terephthalic acid production process comprising the steps of: 1. condensing a steam product at the top of an oxidation reactor, entering an azeotropic distillation tower, performing azeotropic distillation with propyl acetate, 2, returning acetic acid as a bottom product in the step 1 to the oxidation reactor, partially condensing steam at the top of the oxidation reactor, 3, entering a partially condensed liquid phase into an oil-water separator, fully condensing a vapor phase into a liquid phase, and fractionating to recover methyl acetate and propyl acetate, 4, fractionating water separated by the oil-water separator, and recovering methyl acetate and propyl acetate in the water, 5, fractionating an organic phase separated by the oil-water separator, and recovering propyl acetate and methyl acetate as entrainers, and 6, when the content of p-xylene in the organic phase separated by the oil-water separator exceeds a specified value, fractionating to recover p-xylene. The method can reduce the content of methyl acetate in the condensed liquid phase by partially condensing the overhead vapor of the azeotropic tower, thereby being easy to recover.
Description
Technical field
---aliphatic carboxylic acid, reaction raw materials---aromatic hydrocarbons compounds and byproduct of reaction that alkyl replaces---aliphatic carboxylic acid esters,'s the method that the present invention relates to a kind of solvent of producing in the aromatic carboxylic acid process that reclaims.Separation method involved in the present invention is mainly azeotropic distillation.
Background technology
Pure terephthalic acid's (Pure Terephtalic Acid is called for short PTA) is widely used in manufacturing the vibrin of fiber, film, industrial element, common molded part etc.
Aromatic carboxylic acids such as terephthalic acid normally in the presence of catalyzer, aromatic hydrocarbons compounds that the corresponding alkyl of gaseous oxidation replaces such as p-Xylol and make.The production of terephthalic acid is generally carried out in solvent aliphatic carboxylic acid such as acetic acid, in this production process, is attended by the generation of water.For anti-accumulating of sealing influences efficiency, often from oxidation reactor, remove the water that dereaction generates with the form of vapor stream of top of the tower.Such method may make vapor stream of top of the tower comprise other component, mainly contains the by product of solvent and unreacted raw material and reaction.At first, separate the useful component aliphatic carboxylic acid in this vapour stream, and be very necessary the aliphatic carboxylic acid Returning oxidation reactor of this dehydration.When acetic acid was widely used as above-mentioned aliphatic carboxylic acid solvent, the traditional rectification method that has adopted can be finished this detached job.But the azeotropic distillation method of Gong Rening has more effective separating effect, energy expenditure still less and investment still less, process cost and better operational stability.This makes the azeotropic distillation method of this system separate and becomes more favourable.
The research of the azeotropic distillation separation method of relevant this azeotropic system is a lot of both at home and abroad.
Yet, as previously mentioned, except containing water and acetic acid, also have the by-product acetic acid methyl esters of unreacted raw material p-Xylol and reaction in the vapour stream to be separated of introducing azeotropy rectification column.
P-Xylol, boiling point are 137 ℃, form homogeneous azeotrope with acetic acid at 115 ℃, form two liquid phase azeotropes with water at 92 ℃.A spot of p-Xylol is constantly accumulation in tower, when its concentration is increased to a certain degree, will certainly weaken the performance of tower, influences the effect of azeotropic separation.As described in Chinese patent 1161686 and Chinese patent 1219162, in order to remove the p-Xylol in the tower effectively, in the azeotropic distillation process, if use lower boiling relatively acetic acid alkyl ester as entrainer, n-propyl acetate for example, the result can cause p-Xylol that concentration distribution is longitudinally arranged in tower, especially near the feed stream input point, the concentration of p-Xylol obviously increases, and so most of p-Xylol from then on position is discharged outside the tower.Verified, p-Xylol reaches maximum with respect to entrainer concentration and infeeds below the position at position in the water-containing acetic acid incoming flow.On the contrary, if adopt n-butyl acetate as entrainer, p-Xylol then can trend towards being evenly dispersed in the whole tower, can not remove in large quantities in a certain position.
Yet, when removing p-Xylol by this way, entrainer is also discharged from distillation tower, the liquid circulation that side line is discharged is to oxidation reactor, and the entrainer of thereupon discharging to small part is converted into other compound, thereby causes the loss of entrainer.This mode is higher to parameter requests such as the temperature in the azeotropy rectification column, pressure, trim the top of column amounts simultaneously, makes complex process, operation be difficult to control.Chinese patent 1219162 has been introduced and a kind ofly will have been introduced stripping tower from the p-Xylol that contains entrainer that side line is removed, and adds and contains the water of acetic acid so that the isolating method of p-Xylol and entrainer.This invention can effectively reduce the loss of entrainer.
Equally, also contain the by-product acetic acid methyl esters that responds in the aforementioned vapour stream to be separated.Methyl acetate can form the azeotrope be positioned at the single phase region with water, makes that water content reduces in the overhead water azeotrope, thereby reduces the water-content that the condensation of azeotropy rectification column overhead product generates, and has increased the diameter of energy expenditure and tower.Because the concentration of methyl acetate is enough high in the distillation tower vapor stream of top of the tower, steam is on good terms and is condensed into a liquid phase, and this makes that recycle-water is unpractical from overhead product.In the external three big PTA production technology companies (AMOCO, ICI and MPC oiling), AMOCO adopts the condensation compress technique, and this must make the aqueous phase of solvent tower overhead condensation liquid contain a certain amount of methyl acetate; Thereby having ignored the concentration of methyl acetate in the organic phase that forms after the condensation of azeotropy rectification column overhead product, the recovery method of ICI increases the problem that influences the azeotropic separation effect; The method of the direct incineration oxidation device of MPC oiling waste gas then can be ignored the part methyl acetate of the liquid state that enters in the solvent recovery tower.Chinese patent 1312787 and Chinese patent 1264359 etc. also all relate to the recovery technology of methyl acetate, yet, also be assigned a spot of methyl acetate in the organic phase that forms after the azeotropy rectification column overhead product condensation of these processing methodes, the continuous increase of its concentration also will influence the azeotropic separation effect.Chinese patent 1492850 is conceived to the thinking that the concentration of impurity methyl acetate of the aqueous phase of phlegma that the condensation of azeotropic distillation column overhead fraction is obtained draws with the ratio of the concentration of entrainer and makes starting point, has found to suppress the technology that the impurity methyl acetate concentration increases.It requires below 20 times of amount of the methyl acetate that preferably reclaims from water in the amount of the methyl acetate that reclaims from organic phase, and isolating effect below 18 times is better, and is good especially below 15 times.But the change in concentration of this methyl acetate in the azeotropy rectification column overhead product is suitable in very little scope.
Investigate domestic existing patent, in the following aspects raising that haves much room for improvement.
General patent only relates to a kind of material of handling in p-Xylol or the methyl acetate, have only CN1374937, CN1492850 simultaneously the two to be separated, but it all adopts the mode of side line discharging to the processing of p-Xylol, will cause the loss of entrainer inevitably.
To isolating influence, partial monopoly has proposed different treatment processs, has obtained good effect for the existence of methyl acetate.But, also being assigned a spot of methyl acetate in the organic phase that forms after the azeotropy rectification column overhead product condensation of these processing methodes, the continuous increase of its concentration also will influence the azeotropic separation effect.Simultaneously, the cat head methyl acetate content range that such technology is fit to processing is very little, does not have applicability widely.
At these situations, the present invention is conceived to the comprehensive recovery of solvent acetic acid in the Production of Terephthalic Acid process, raw material p-Xylol and by-product acetic acid methyl esters, introduces less energy-consumption, the technology of high organic efficiency.Its purpose be by under not causing the situation of entrainer loss, intermittently reclaim in the charging p-Xylol and by reclaiming the methyl acetate in water and the organic phase simultaneously, thereby improve the efficient of azeotropic distillation, the final acetic acid that obtains high density that reclaims returns oxidizing reaction.
Summary of the invention
The objective of the invention is to produce the acetate system of moisture and other impurity that forms in the process of aromatic carboxylic acid, the azeotropic distillation method of a kind of comprehensive recovery acetic acid, p-Xylol and by-product acetic acid methyl esters is provided at the aromatic hydrocarbon based compound for catalysis oxidation that replaces with alkyl.
A kind of method that reclaims raw material, solvent and by product in the Production of Terephthalic Acid process is characterized in that it comprises the following steps:
Step 1. enters azeotropy rectification column and entrainer Iso Butyl Acetate azeotropic distillation with oxidation reactor overhead vapours product after condenser condenses, the phlegma of separation of oxygenated reactor cat head steam product, bottom product is the solvent acetic acid of moisture content less, overhead vapours contains water, raw material p-Xylol, by-product acetic acid methyl esters and entrainer Iso Butyl Acetate
Oxidation reactor overhead vapours product in the aromatic carboxylic acid production process contains the aliphatic carboxylic acid acetic acid as solvent, the water that reaction generates, aromatic hydrocarbons compounds p-Xylol and the byproduct of reaction aliphatic carboxylic acid esters, methyl acetate that the reaction raw materials alkyl replaces.The described oxidation reactor overhead vapours of azeotropic fractionation phlegma under the condition of entrainer such as Iso Butyl Acetate existence forms acetic acid bottom product that contains less water and the overhead product that contains above-mentioned raw materials, water and by product,
Step 2. is made solvent with the bottom product acetic acid Returning oxidation reactor of step 1, and with the overhead vapours partial condensation of step 1, water, p-Xylol and Iso Butyl Acetate are condensed into liquid phase simultaneously, and uncooled vapour phase partly is mainly methyl acetate,
The liquid phase of step 3. step 2 condensation enters oil, water separator, simultaneously will be still for the methyl acetate of vapour phase is condensed into liquid phase entirely, and further methyl acetate and entrainer Iso Butyl Acetate are reclaimed in fractionation,
Step 4. is step 3 oil, the further fractionation of the isolated water of water separator, methyl acetate in the recycle-water and Iso Butyl Acetate,
Step 5. is with step 3 oil, the isolated organic phase of water separator, and entrainer Iso Butyl Acetate and by-product acetic acid methyl esters are reclaimed in further fractionation,
When the amount of the p-Xylol that step 6. contains when step 3 oil, the isolated organic phase of water separator surpasses 6% (mass percentage concentration), organic phase is pumped into the fractionation of p-Xylol knockout tower, (if necessary, can add the water that contains acetic acid and help entrainer to separate with p-Xylol, the amount that adds entry is controlled in the concentration range of water and p-Xylol formation azeotropic component); Reclaim p-Xylol at the bottom of the tower, Returning oxidation reactor is made raw material, and overhead vapours is after condensation, and entrainer Iso Butyl Acetate (at the bottom of the tower) and methyl acetate (cat head) are reclaimed in further fractionation.
Recovery method provided by the invention is fit to handle the azeotropy rectification column feed stream that contains various strength acetic acid methyl esters.For the situation that contains the high-concentration acetic acid methyl esters in the feed stream, partial condensation azeotropy rectification column overhead vapours can be so that the content of methyl acetate reduces in the liquid phase of overhead condensation, thereby is easy to reclaim.
Another advantage of recovery method of the present invention is: handle methyl acetate in water that the azeotropy rectification column overhead vapours forms after condensation and the organic phase simultaneously.Thereby efficiently solve traditional treatment method and ignore the problem that the continuous accumulation of methyl acetate in the organic phase influences the azeotropic separation effect.
The present invention is directed to and contain a small amount of p-Xylol in the oxidation reactor overhead vapours, adopt the method for batch operation to handle.Promptly when its content surpasses 6% (mass percentage concentration), recycle, keeping its content in azeotropy rectification column in the concentration range that allows, thereby do not influence the effect of azeotropic separation.
Recovery method of the present invention can make the entrainer that enters azeotropy rectification column cat head position that refluxes keep foreign matter content less relatively.
Description of drawings
Fig. 1 is the schema of an embodiment of the inventive method.
Embodiment
Specify recovery method of the present invention below by schema.
With the p-Xylol is raw material, produces in pure terephthalic acid's the process at catalyzer with in the presence of as the acetic acid of solvent, and the overhead vapours product mainly contains acetic acid, water, reaction raw materials p-Xylol and byproduct of reaction methyl acetate.
Overhead vapours product 2 from oxidation reactor 1 enters in the azeotropy rectification column 4 through condenser 3 condensations.Feed entrance point is the position (the azeotropic district is at least 0.1% distillation tower zone with entrainer mass content in total liquid phase) that is higher than azeotropic district lower limit, and this can guarantee that the logistics that enters azeotropy rectification column can fully contact with entrainer, forms minimum azeotropic mixture.
In the presence of entrainer, overhead vapours product 2 separates in azeotropy rectification column 4.Form the acetic acid 19 of moisture content less at the bottom of the tower, acetic acid 19 parts are back to oxidation reactor 1 through pipeline 5, are partly refluxed to azeotropy rectification column 4.The azeotropy rectification column overhead vapours is the azeotrope of entrainer and water and comprises the byproduct of reaction methyl acetate at some interior organism.As previously mentioned, the existence of methyl acetate can influence the effect of azeotropic separation.And because the boiling point of methyl acetate has only 57 ℃, therefore when methyl acetate concentration is higher in the overhead product, can be by fractional distillating tube 6 controlled temperature with all the other components condense to decanting vessel 7 (decanting vessel is a kind of oil, water separator), and methyl acetate with vapor form through total condenser 8 total condensation, enter methyl acetate recovery tower 11 and reclaim methyl acetates.The content of the methyl acetate that can contain in the handled like this oxidation reactor overhead vapours product has bigger concentration range.Thereby make the present invention have applicability more widely.
The weir 7.1 that decanting vessel 7 is equipped with certain altitude is divided into two portions in order to water phase separated and organic phase.Because the proportion of water is big than organic phase, the phlegma that enters decanting vessel 7.2 is divided into two-phase up and down in the chamber, and when its liquid level surpassed weir 7.1, the organic phase on upper strata spilt into chamber 7.3; And when liquid level reduced, the valve of discharging by liquid-level controller 10 control waters made lower floor's liquid continue to assemble.
As previously mentioned, isolating organic phase and aqueous phase all contain the methyl acetate of a small amount of condensation, and this influence to azeotropic separation is very big.The methyl acetate of aqueous phase reclaims in the following manner.The water that discharge chamber 7.2 enters methyl acetate recovery tower 11 separating acetic acid methyl esters and water.Methyl acetate recovery tower 11 bottom products are moisture, and part acetic acid and a small amount of entrainer are as aqueous-phase reflux separating acetic acid and water to the azeotropy rectification column 4.Overhead product contains the methyl acetate partial reflux of a small amount of entrainer, and all the other enter vapor-liquid separation tower 12 and are separated into vapor phase acetic acid methyl esters and liquid phase entrainer after the fractional distillating tube partial condensation.The methyl acetate hydrolyzable becomes acetic acid and methyl alcohol, and acetic acid can be back to oxidation reactor, or reclaims methyl acetate as fuel, or with using it for anything else.Separated fresh entrainer is back to the chamber 7.4 of decanting vessel 7 at the bottom of methyl acetate recovery tower 11 towers, be back to azeotropy rectification column 4 through pipeline 13 then.Like this, the entrainer of aqueous phase also obtains efficient recovery to a certain extent.And reclaimed in the process below of the methyl acetate in the organic phase.
Organic phase in the decanting vessel 7 can directly enter entrainer and the methyl acetate that methyl acetate recovery tower 11 separates wherein by valve 15.But as previously mentioned, the existence of p-Xylol has negative influence to separation.This can remove it from organic phase by the following method effectively.When detecting thief hole 16 samplings and detect that p-Xylol content surpasses 6% (mass percentage concentration) in the organic phase, open valve 18 towards p-Xylol knockout tower 17, will introduce p-Xylol knockout tower 17 from the organic phase that decanting vessel 7 is discharged.P-Xylol knockout tower 17 is in order to separation and azeotropic agent and p-Xylol, and WO9729068 describes as patent, because the two has similar volatility, adds the water that contains little acetic acid at top of tower and can change its relative volatility and make the two separation.At the bottom of the tower p-Xylol, partial reflux wherein, all the other are back to oxidation reactor.Overhead product 21 mainly contains entrainer and enters further separation methyl acetate wherein of vapor-liquid separation tower 12.Like this, the methyl acetate in the organic phase also obtains efficient recovery, and this has solved the problem of the separating effect variation that the increase of methyl acetate content causes in the organic phase.Equally, the entrainer of purifying enters decanting vessel chamber 7.4 through pipeline 9, is back to azeotropy rectification column 4 through pipeline 13 again.Like this, the entrainer that makes backflow enter azeotropy rectification column 4 keeps purer.Liquid-level controller 22 enters azeotropy rectification column 4 in order to the entrainer of controlling from chamber 7.4, can guarantee in time to replenish entrainer and enter azeotropy rectification column 4 to keep the operation balance under the situation that chamber 7.4 entrainers reduce.Thus, the entrainer of organic phase and aqueous phase all reclaims through purifying.
Embodiment
Concrete application of the present invention is described by the following examples, but range of application of the present invention is not subjected to the restriction of the following example.
Embodiment 1
Solution to be separated is the acetum that contains p-Xylol and methyl acetate, and the entrainer of azeotropic distillation is an Iso Butyl Acetate, handles this system continuously with technical process as shown in Figure 1.
To produce the solution that is reclaimed in each operation of terephthalic acid process, composed as follows: the total feed rate of time per unit is acetic acid 57.990 mass parts, water 19.770 mass parts, p-Xylol 0.022 mass parts, methyl acetate 0.292 mass parts to system to be separated from the p-Xylol liquid-phase oxidation.This system divides 5 bursts of chargings to be fed to respectively on the 9th, 12,33,34, the 29 block of plate that number of theoretical plate is 38 azeotropy rectification column 4.The mass percentage concentration that obtains time per unit 57.715 mass parts at the bottom of the tower of azeotropy rectification column 4 is 97.99% concentrated acetic acid, at the bottom of the tower in the liquid effluent p-Xylol and methyl acetate concentration below 20ppm, contain Iso Butyl Acetate hardly; Acetate concentration is lower than 0.1% in the azeotropy rectification column 4 cat head part phlegmas, p-Xylol concentration 100ppm, and methyl acetate concentration 0.1%, all the other are water and entrainer.This cat head part condensed product shared oil, water two-phase after condensation.
The 2nd block of plate that water directly pumps into methyl acetate recovery tower 11 divides dried up and methyl acetate.Methyl acetate recovery tower 11 number of theoretical plates are 6, separate to obtain the water that methyl acetate concentration at the bottom of the tower is lower than 10ppm, and cat head is the azeotrope of methyl acetate and portion water, pumps into vapor-liquid separation tower 12.
During p-Xylol mass percentage concentration in detecting the condensed oil phase of azeotropy rectification column 4 cat head part condensed product 〉=6%, it is that 16 p-Xylol knockout tower 17 reclaims p-Xylol that oil phase is sent to number of theoretical plate, and charging is on the 9th block of plate of p-Xylol knockout tower 17.Separate to obtain the cat head overhead product and be lower than the Iso Butyl Acetate of 50ppm for p-Xylol concentration, at this, the entrainer loss is lower than 0.01%, and the entrainer Iso Butyl Acetate pumps into vapor-liquid separation tower 12.When p-Xylol concentration in the oil phase is low, then directly pump into methyl acetate recovery tower 11 separation and azeotropic agent Iso Butyl Acetates.
Embodiment 2
Except the mass parts with methyl acetate in the system to be separated among the embodiment 1 is increased to 2.80, all the other conditions are all identical with embodiment 1 with treatment process.Methyl acetate concentration is lower than 5ppm even lower at the bottom of the tower of methyl acetate recovery tower 11.
Can determine that like this between 0.1-10%, this concentration range is not subjected to the restriction of embodiment 1 and embodiment 2 to the methyl acetate concentration scope at least in the suitable processing of the present invention azeotropic distillation dehydration column overhead water.If any application need, also can extend to bigger range of application.
Claims (2)
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| CNB2005100385607A CN1300088C (en) | 2005-03-25 | 2005-03-25 | Method for recovering raw material, solvent and by-product in aromatic carboxylic acid production process |
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| CNB2005100385607A CN1300088C (en) | 2005-03-25 | 2005-03-25 | Method for recovering raw material, solvent and by-product in aromatic carboxylic acid production process |
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| CN1696098A CN1696098A (en) | 2005-11-16 |
| CN1300088C true CN1300088C (en) | 2007-02-14 |
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Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101712616B (en) * | 2008-09-30 | 2013-09-04 | 李长海 | Method for separating dimethyl benzene and butyl acetate from industrial waste solvent |
| CN101792386B (en) * | 2010-02-04 | 2013-04-10 | 南京工业大学 | Method for treating solvent and by-product in aromatic carboxylic acid production |
| CN102653512B (en) * | 2011-03-02 | 2014-08-20 | 中国石油化工股份有限公司 | Integrated process for recovering acetic acid and methyl acetate in production process of aromatic carboxylic acid |
| CN102423548A (en) * | 2011-08-18 | 2012-04-25 | 天津市化工设计院 | Recovery and separation system and method for xylene from water-absorption cis-butenedioic anhydride production process |
| CN102746135B (en) * | 2012-08-01 | 2015-03-25 | 中国石油化工股份有限公司 | Method for recovering acetic acid and water through azeotropic distillation in aromatic carboxylic acid production |
| CN104974035B (en) * | 2014-04-11 | 2016-10-05 | 中国石化扬子石油化工有限公司 | Azeotropic distillation is used to process the acetic acid containing dialkyl aromatic hydrocarbons and water method |
| CN115745797A (en) * | 2022-12-03 | 2023-03-07 | 福州大学 | Process for synthesizing propylene glycol monomethyl ether acetate and byproduct 1, 2-diacetoxy propane through continuous reaction, rectification and esterification |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1219162A (en) * | 1996-02-09 | 1999-06-09 | 纳幕尔杜邦公司 | Azeotropic distillation process |
| CN1264359A (en) * | 1997-04-09 | 2000-08-23 | 纳幕尔杜邦公司 | Water separation process |
| CN1312787A (en) * | 1998-08-11 | 2001-09-12 | 纳幕尔杜邦公司 | Method for recovering methyl acetate and residual acetic acid in the production of pure terephthalic acid |
| CN1374937A (en) * | 1999-09-21 | 2002-10-16 | 纳幕尔杜邦公司 | Process for producing pure terephthalic acid with improved recovery of precursors, solvent and mentyl acetate |
| CN1492850A (en) * | 2001-02-27 | 2004-04-28 | 三菱化学株式会社 | Azeotropic distillation method |
-
2005
- 2005-03-25 CN CNB2005100385607A patent/CN1300088C/en not_active Expired - Lifetime
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1219162A (en) * | 1996-02-09 | 1999-06-09 | 纳幕尔杜邦公司 | Azeotropic distillation process |
| CN1264359A (en) * | 1997-04-09 | 2000-08-23 | 纳幕尔杜邦公司 | Water separation process |
| CN1312787A (en) * | 1998-08-11 | 2001-09-12 | 纳幕尔杜邦公司 | Method for recovering methyl acetate and residual acetic acid in the production of pure terephthalic acid |
| CN1374937A (en) * | 1999-09-21 | 2002-10-16 | 纳幕尔杜邦公司 | Process for producing pure terephthalic acid with improved recovery of precursors, solvent and mentyl acetate |
| CN1492850A (en) * | 2001-02-27 | 2004-04-28 | 三菱化学株式会社 | Azeotropic distillation method |
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