CN115124417B - Refining method and equipment for lactic acid monomer - Google Patents
Refining method and equipment for lactic acid monomer Download PDFInfo
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- CN115124417B CN115124417B CN202210962469.8A CN202210962469A CN115124417B CN 115124417 B CN115124417 B CN 115124417B CN 202210962469 A CN202210962469 A CN 202210962469A CN 115124417 B CN115124417 B CN 115124417B
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- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 title claims abstract description 430
- 239000004310 lactic acid Substances 0.000 title claims abstract description 219
- 235000014655 lactic acid Nutrition 0.000 title claims abstract description 215
- 238000007670 refining Methods 0.000 title claims abstract description 76
- 239000000178 monomer Substances 0.000 title claims abstract description 40
- 238000000034 method Methods 0.000 title abstract description 39
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims abstract description 361
- 238000006460 hydrolysis reaction Methods 0.000 claims abstract description 132
- 230000007062 hydrolysis Effects 0.000 claims abstract description 119
- 239000003054 catalyst Substances 0.000 claims abstract description 11
- 238000011084 recovery Methods 0.000 claims description 98
- 238000010992 reflux Methods 0.000 claims description 50
- 238000000926 separation method Methods 0.000 claims description 44
- 238000005192 partition Methods 0.000 claims description 35
- 238000012856 packing Methods 0.000 claims description 30
- 230000008878 coupling Effects 0.000 claims description 12
- 238000010168 coupling process Methods 0.000 claims description 12
- 238000005859 coupling reaction Methods 0.000 claims description 12
- 230000003197 catalytic effect Effects 0.000 claims description 10
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 claims description 5
- 239000002253 acid Substances 0.000 claims description 5
- 239000003729 cation exchange resin Substances 0.000 claims description 5
- 239000000945 filler Substances 0.000 claims description 4
- LPEKGGXMPWTOCB-UHFFFAOYSA-N 8beta-(2,3-epoxy-2-methylbutyryloxy)-14-acetoxytithifolin Natural products COC(=O)C(C)O LPEKGGXMPWTOCB-UHFFFAOYSA-N 0.000 abstract description 33
- ODQWQRRAPPTVAG-GZTJUZNOSA-N doxepin Chemical compound C1OC2=CC=CC=C2C(=C/CCN(C)C)/C2=CC=CC=C21 ODQWQRRAPPTVAG-GZTJUZNOSA-N 0.000 abstract description 33
- 229940057867 methyl lactate Drugs 0.000 abstract description 33
- 238000005886 esterification reaction Methods 0.000 abstract description 27
- 239000000463 material Substances 0.000 abstract description 22
- 239000007795 chemical reaction product Substances 0.000 abstract description 18
- 239000000047 product Substances 0.000 abstract description 11
- 230000003287 optical effect Effects 0.000 abstract description 10
- 239000000126 substance Substances 0.000 abstract description 10
- 230000032050 esterification Effects 0.000 abstract description 6
- 230000003301 hydrolyzing effect Effects 0.000 abstract description 4
- 230000009471 action Effects 0.000 abstract description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 31
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 26
- JVTAAEKCZFNVCJ-REOHCLBHSA-N L-lactic acid Chemical compound C[C@H](O)C(O)=O JVTAAEKCZFNVCJ-REOHCLBHSA-N 0.000 description 16
- 229930182843 D-Lactic acid Natural products 0.000 description 14
- JVTAAEKCZFNVCJ-UWTATZPHSA-N D-lactic acid Chemical compound C[C@@H](O)C(O)=O JVTAAEKCZFNVCJ-UWTATZPHSA-N 0.000 description 14
- 229940022769 d- lactic acid Drugs 0.000 description 14
- 239000000203 mixture Substances 0.000 description 14
- 239000002994 raw material Substances 0.000 description 14
- 239000012071 phase Substances 0.000 description 13
- 230000008569 process Effects 0.000 description 12
- 238000006243 chemical reaction Methods 0.000 description 11
- 239000012535 impurity Substances 0.000 description 8
- 238000007599 discharging Methods 0.000 description 7
- 238000000605 extraction Methods 0.000 description 7
- 238000000746 purification Methods 0.000 description 7
- 238000005265 energy consumption Methods 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 6
- 239000007788 liquid Substances 0.000 description 6
- 238000002156 mixing Methods 0.000 description 6
- 230000008901 benefit Effects 0.000 description 5
- 238000000855 fermentation Methods 0.000 description 5
- 230000004151 fermentation Effects 0.000 description 5
- 239000012264 purified product Substances 0.000 description 5
- 238000001514 detection method Methods 0.000 description 4
- LZCLXQDLBQLTDK-UHFFFAOYSA-N ethyl 2-hydroxypropanoate Chemical compound CCOC(=O)C(C)O LZCLXQDLBQLTDK-UHFFFAOYSA-N 0.000 description 4
- 239000002699 waste material Substances 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 150000003903 lactic acid esters Chemical class 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 229920000747 poly(lactic acid) Polymers 0.000 description 3
- 239000004626 polylactic acid Substances 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- MKJXYGKVIBWPFZ-UHFFFAOYSA-L calcium lactate Chemical compound [Ca+2].CC(O)C([O-])=O.CC(O)C([O-])=O MKJXYGKVIBWPFZ-UHFFFAOYSA-L 0.000 description 2
- 229960002401 calcium lactate Drugs 0.000 description 2
- 239000001527 calcium lactate Substances 0.000 description 2
- 235000011086 calcium lactate Nutrition 0.000 description 2
- 229940116333 ethyl lactate Drugs 0.000 description 2
- 238000004128 high performance liquid chromatography Methods 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000012808 vapor phase Substances 0.000 description 2
- 102000004190 Enzymes Human genes 0.000 description 1
- 108090000790 Enzymes Proteins 0.000 description 1
- JVTAAEKCZFNVCJ-UHFFFAOYSA-M Lactate Chemical compound CC(O)C([O-])=O JVTAAEKCZFNVCJ-UHFFFAOYSA-M 0.000 description 1
- 241001052560 Thallis Species 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000000306 component Substances 0.000 description 1
- 229910000365 copper sulfate Inorganic materials 0.000 description 1
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- -1 ethanol ester Chemical class 0.000 description 1
- 239000012847 fine chemical Substances 0.000 description 1
- 239000000413 hydrolysate Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 229960000448 lactic acid Drugs 0.000 description 1
- JJTUDXZGHPGLLC-UHFFFAOYSA-N lactide Chemical compound CC1OC(=O)C(C)OC1=O JJTUDXZGHPGLLC-UHFFFAOYSA-N 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000000813 microbial effect Effects 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 1
- ILVGAIQLOCKNQA-UHFFFAOYSA-N propyl 2-hydroxypropanoate Chemical compound CCCOC(=O)C(C)O ILVGAIQLOCKNQA-UHFFFAOYSA-N 0.000 description 1
- 102000004169 proteins and genes Human genes 0.000 description 1
- 108090000623 proteins and genes Proteins 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 238000000066 reactive distillation Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/487—Separation; Purification; Stabilisation; Use of additives by treatment giving rise to chemical modification
- C07C51/493—Separation; Purification; Stabilisation; Use of additives by treatment giving rise to chemical modification whereby carboxylic acid esters are formed
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention discloses a method and equipment for refining lactic acid monomers. The crude lactic acid and methanol are preheated to carry out esterification reaction under the action of a catalyst, so as to obtain a reaction product containing methyl lactate; separating and hydrolyzing the reaction product to obtain a material containing unreacted lactic acid and methyl lactate and purified lactic acid and methanol; refining the purified lactic acid to obtain a lactic acid monomer product; unreacted lactic acid and methyl lactate are separated and purified, the recovered lactic acid and methanol are subjected to esterification reaction, and the recovered methyl lactate is separated and hydrolyzed; and (3) recovering methanol from the methanol-containing material, and carrying out esterification reaction on the recovered methanol and crude lactic acid. The esterification rate of the crude lactic acid is over 99 percent, the mass concentration of the lactic acid extracted from the tower bottom of the hydrolysis tower is over 90 percent, the chemical purity of the lactic acid monomer in the side discharge of the refining tower is higher than 0.999, and the optical purity of the lactic acid monomer is higher than 0.999.
Description
Technical Field
The invention relates to the field of chemical industry, in particular to a methyl lactate esterification reaction process, a methyl lactate hydrolysis process, a rectification separation technology and corresponding equipment, and more particularly relates to a refining method and equipment of lactic acid monomers.
Background
Lactic acid is a multipurpose fine chemical, lactic acid, lactate and derivatives thereof are widely applied to the fields of food, chemical industry, medicine and the like, 2 corresponding isomer forms of lactic acid exist, namely D-lactic acid and L-lactic acid respectively, and a high-purity lactic acid monomer is a basic raw material for synthesizing environment-friendly and biocompatible polylactic acid. In recent years, with the development and application of polylactic acid, the demand for high-purity lactic acid monomers is increasing.
The production method of lactic acid mainly comprises a chemical synthesis method, an enzyme method and a microbial fermentation method, and the fermentation method has the advantages of low raw material price, high optical purity, green and environment-friendly production process and the like, is a main method for industrial production of lactic acid, but is limited by the characteristics of strong hydrophilicity, difficult volatility and the like of lactic acid, and fermentation liquid contains thalli, proteins, inorganic salts and the like, so that the separation and purification process of lactic acid in the fermentation liquid is complex, and lactic acid with high purity level cannot be obtained. The traditional separation method of lactic acid comprises a calcium lactate crystallization process and a calcium lactate direct acidolysis process, and has the advantages of simple process and easy control, but the product purity is low, and a plurality of impurities in fermentation liquor cannot be effectively separated and cannot be directly used for the subsequent production of polylactic acid or lactide.
The esterification-hydrolysis method can produce high-purity lactic acid monomers (D-lactic acid and L-lactic acid), is also a common method capable of effectively separating lactic acid from other organic matters at present, lactic acid is easy to generate volatile lactic acid ester with lower alcohol (methanol, ethanol and the like) in the presence of a catalyst, and the lactic acid ester is separated and purified by reduced pressure rectification to obtain purer lactic acid ester which undergoes hydrolysis reaction by water vapor in the presence of the catalyst, and then is separated to obtain refined lactic acid. Therefore, reaction rectification and esterification-hydrolysis coupling refined lactic acid are hot points of current research, crude lactic acid is esterified by methanol to obtain reactants containing methyl lactate, lactic acid, methanol and water, and the mixture is subjected to hydrolysis and rectification separation to obtain refined lactic acid. At present, the main process for refining lactic acid by reactive distillation is divided into a plurality of single towers and partition towers. The multi-unit tower is characterized in that a mixture containing methyl lactate, lactic acid, methanol and water firstly enters a methyl lactate reaction rectifying tower to carry out hydrolysis reaction and primary separation of components, lactic acid and water extracted from a tower kettle enter a subsequent refining tower to refine the lactic acid, but the water has back mixing phenomenon in the tower, heavy component accumulation and the temperature of the tower kettle are not easy to control, so that high energy consumption and unstable product quality are caused. The partition tower technology is characterized in that a vertical partition plate is arranged inside a single tower, a rectifying tower is divided into an upper section, a lower section and a feeding section and a lateral line extraction section separated by the partition plate, a hydrolysis catalyst is arranged in the middle section, methanol (or methanol and water) is extracted from the tower top, water is extracted from the side, refined lactic acid is extracted from the tower bottom, the problem that the temperature of the tower bottom is difficult to control is also faced, other impurities, particularly substances with boiling point larger than that of lactic acid (almost) cannot be contained in materials entering the partition tower, and the quality of lactic acid is difficult to meet the requirement.
Disclosure of Invention
The invention aims to provide a refining method and equipment of lactic acid monomer, which can overcome the defects existing in the existing process of preparing (refining) lactic acid: the preparation of lactic acid adopts an esterification-hydrolysis process, so that the quality requirement on raw material lactic acid is reduced; the process for refining the lactic acid can flexibly control the temperature in the process, ensure the quality of lactic acid monomers and the yields of raw materials lactic acid and methanol; can ensure the esterification rate of crude lactic acid and methanol and the hydrolysis conversion rate of methyl lactate, can avoid the back mixing of water components in the tower, saves energy consumption, and has remarkable practicability and economic benefit.
By applying the technology of the invention, the yield of the crude lactic acid to lactic acid monomers (including D-lactic acid and L-lactic acid) reaches more than 95%, the chemical purity of the lactic acid monomers is higher than 0.999, and the optical purity of the lactic acid monomers is higher than 0.999.
The technical scheme of the invention is as follows:
A method for refining lactic acid monomer comprises the following steps:
s1, preheating crude lactic acid and methanol to perform esterification reaction under the action of a catalyst to obtain a reaction product containing methyl lactate;
s2, separating and hydrolyzing the reaction product in the step S1 to obtain a purified product of lactic acid and methyl lactate containing unreacted lactic acid and a methanol containing material;
s3, refining the purified lactic acid in the step S2 to obtain a lactic acid monomer product;
s4, separating and purifying the lactic acid and methyl lactate obtained in the step S2, returning the recovered lactic acid to the step S1 for esterification reaction with methanol, and returning the recovered methyl lactate to the step S2 for separation and hydrolysis;
And S5, recovering the methanol from the methanol-containing material in the step S2, and returning the recovered methanol to the step S1 to perform esterification reaction with crude lactic acid.
In the step S1, the mass concentration of raw material lactic acid is more than or equal to 0.75, the mass concentration of raw material methanol is more than or equal to 0.9, and the feeding mole ratio of the methanol to the lactic acid is 2-10: 1.
The operation temperature of the pre-reaction is 70-130 ℃, and the operation pressure is controlled to be 200-900 kPa; in the step S2, the operation pressure for separating and hydrolyzing the reaction product is 5-15 kPa, and the operation temperature is 40-75 ℃; in the step S3, the operation pressure of the purification product lactic acid refining is 1-15 kPa, and the operation temperature is 20-80 ℃; in the step S4, the operation temperature for separating and purifying the lactic acid and the methyl lactate is 70-100 ℃, and the operation pressure is 1-5 kPa; in the step S5, the operation temperature of methanol recovery is 120-140 ℃ and the operation pressure is 400-650 kPa.
The esterification catalyst contained in the reactor is strong acid cation exchange resin.
The present invention provides an apparatus for refining lactic acid monomer, comprising: the device comprises a preheater, a reactor, a hydrolysis tower reboiler, a hydrolysis tower coupling reboiler, a hydrolysis tower condenser, a hydrolysis tower reflux tank, a lactic acid recovery tower reboiler, a lactic acid recovery tower condenser, a lactic acid recovery tower reflux tank, a refining tower reboiler, a refining tower condenser, a refining tower reflux tank, a methanol recovery tower reboiler, a methanol recovery tower subcooler and a methanol recovery tower reflux tank; the outlet of the preheater is connected with the inlet of the reactor, the outlet of the reactor is connected with the inlet of the hydrolysis tower, the outlet of the top of the hydrolysis tower is connected with the inlet of the hydrolysis tower condenser, and the outlet of the hydrolysis tower condenser is connected with the reflux tank of the hydrolysis tower; the outlet of the reflux tank of the hydrolysis tower is connected with the inlet of the methanol recovery tower, the outlet of the top of the methanol recovery tower is connected with the hot side inlet of the coupling reboiler of the hydrolysis tower, and the hot side outlet of the coupling reboiler of the hydrolysis tower is connected with the inlet of the subcooler of the methanol recovery tower; the outlet of the hydrolysis tower pre-separation tower kettle is connected with the inlet of the lactic acid recovery tower, and the gas phase outlet of the top of the lactic acid recovery tower is connected with the inlet of the lactic acid recovery tower condenser; the outlet of the hydrolysis section tower kettle of the hydrolysis tower is connected with the inlet of the refining tower, and the outlet of the top of the refining tower is connected with the inlet of the condenser of the refining tower.
The hydrolysis tower adopts a partition tower, the inside of the tower is divided into two vertical spaces by a partition plate, the pre-separation section is on the same side as the feeding, the hydrolysis section is arranged on the other side of the partition plate, and catalytic filler is formed by combining a strong acid cation exchange resin catalyst and a silk screen filler according to a hollow structure; the operation pressure of the top of the hydrolysis tower is 5-15 kPa, the operation temperature of the top of the tower is 40-75 ℃, and the reflux feed ratio is 0.5-2.
The refining tower adopts a partition tower, the inside of the tower is divided into two vertical spaces by a partition, a pre-separation section is arranged on the same side of the partition as the feeding section, and a lateral line discharging section is arranged on the other side of the partition; the operation pressure of the top of the refining tower is 1-15 kPa, the operation temperature of the top of the refining tower is 20-80 ℃, and the reflux feed ratio is 3-9.
The operation temperature of the top of the lactic acid recovery tower is 70-100 ℃, the operation pressure of the top of the tower is 1-5 kPa, and the reflux feed ratio is 1-5; the operation temperature of the top of the methanol recovery tower is 120-140 ℃, the operation pressure of the top of the tower is 400-650 kPa, and the reflux feed ratio is 2-5.
The refining tower, the lactic acid recovery tower and the methanol recovery tower all adopt high-efficiency structured packing, and the hydrolysis tower adopts high-efficiency structured packing except catalytic packing.
The inside baffle lower extreme to the tower cauldron of hydrolytic column also divide into two vertical spaces with the tower cauldron, baffle upper end to the upper portion in the tower, be less than the top, consequently there is public rectifying section not have public stripping section, public rectifying section is equipped with 2 sections high-efficient structured packing on baffle upper portion, preseparation section and feeding homonymy are equipped with 4 sections high-efficient structured packing, the section of hydrolysising is at the baffle opposite side, 2 sections catalytic packing, catalytic packing upper and lower ends respectively have and are equipped with 1 section high-efficient structured packing. The hydrolysis tower combines the pre-separation tower and the hydrolysis tower in one rectifying tower, so that the equipment investment is saved, and meanwhile, the heat is recycled in the same tower, so that the energy consumption is saved.
Preferably, the reaction product from the reactor is sent to a hydrolysis tower pre-separation Duan Dafu, unreacted lactic acid and methyl lactate in the pre-separation section are gathered in a tower kettle as heavy phases, and are extracted from the tower kettle at the side and sent to a lactic acid recovery tower, the lactic acid, methanol and water vapor phase rise from the separation section and enter a public rectifying section, the light-phase methanol vapor phase comes out from the top of the public rectifying section and enters a lactic acid condenser to be condensed, a part of methanol is taken as reflux, a part of methanol is extracted from the top of the tower, lactic acid and water in the public rectifying section are gathered at the lower end of the public rectifying section as heavy phases, a part of the lactic acid and the methyl lactate are taken as reflux of the pre-separation section, and a part of the lactic acid and the water are taken as feed and reflux of the hydrolysis section simultaneously; the hydrolysis takes place in the hydrolysis section, and the hydrolysate is methyl alcohol and lactic acid, and methyl alcohol and water gather in the upper end as light phase in the hydrolysis section to through public rectifying section, methyl alcohol is extracted, and lactic acid stays the gathering in the hydrolysis section tower cauldron as the heavy phase, and is extracted as lactic acid purification, and this method separates lactic acid and methyl lactate, and methyl lactate hydrolysis is accomplished in single tower.
Further, the temperature of the tower bottom of the hydrolysis tower is controlled to be not more than 130 ℃ by adjusting the extraction amount from the pre-separation tower bottom of the hydrolysis tower.
The lower end of the internal baffle plate of the refining tower is connected to the middle lower part of the refining tower, the upper end of the internal baffle plate is connected to the middle upper part of the refining tower, and the upper end and the lower end of the baffle plate are not connected to the tower kettle and the tower top, so that the refining tower is provided with a public rectifying section, a pre-separation section, a lateral line discharging section and a public stripping section; the method comprises the steps that a public rectifying section is provided with 2 sections of efficient structured packing at the upper part of a partition plate, a pre-separating section and a feeding section are arranged on the same side, 4 sections of efficient structured packing are arranged on the other side of the partition plate, a lateral line discharging section is provided with 4 sections of efficient structured packing, a public stripping section is provided with 2 sections of efficient structured packing at the lower part of the partition plate, lactic acid of a purified product enters from the upper part (from top to bottom) of the 2 nd section of packing of the pre-separating section of a refining tower, lactic acid and light components are used as light phases at the upper end of the pre-separating section and then enter the public rectifying section, the light components are mainly gathered at the upper end of the public rectifying section and condensed by a refining tower condenser, a part of the lactic acid is extracted, a part of the lactic acid flows back at the lower end of the public rectifying section, a part of the lactic acid is used as the reflux of the pre-separating section, and a part of the lactic acid is used as the feeding and the reflux of the lateral line discharging section at the same time; at the upper end of the side line discharging section, the heavy components are gathered at the lower end, and the lactic acid product is extracted from the upper part (from top to bottom) of the 2 nd section of the side extraction discharging section; and (3) separating lactic acid from heavy components in the stripping section of the public stripping section, the stripping section of the pre-separation section and the stripping section of the side line extraction section, and concentrating the heavy components in a tower kettle to be extracted.
In order to remove the light components in the system, a side-extraction port is reserved in the rectifying section of the methanol recovery tower, methanol is extracted from the side, and the light components are extracted from the top of the tower.
Further, according to the method and apparatus for refining lactic acid monomer of the present invention, crude lactic acid and methanol, but not limited to, lower alcohols such as ethanol, propanol, etc., are subjected to esterification reaction in a reactor to produce methyl lactate, ethyl lactate, propyl lactate, etc., and then fed into a hydrolysis tower for separation and hydrolysis to obtain purified lactic acid, and lactic acid monomer (including D-lactic acid and L-lactic acid) is obtained by a refining tower.
The invention has the beneficial effects that:
The invention adopts the technology of combining a reactor and a hydrolysis tower (a partition tower) to simultaneously realize crude lactic acid esterification and hydrolysis and separation of methanol and water, wherein the esterification rate of the crude lactic acid is more than 99 percent, the mass fraction of lactic acid extracted from the tower bottom of the hydrolysis tower is more than 90 percent, the chemical purity of lactic acid monomers in side discharge of a refining tower (the partition tower) is higher than 0.999, and the optical purity of the lactic acid monomers is higher than 0.999.
Compared with the prior art, the method has the advantages that one reactor and two partition towers are adopted to realize the control of the temperature of the tower bottom from crude lactic acid to refined lactic acid, the quality requirement on the crude lactic acid is low, and meanwhile, the tower bottom of the pre-separation section of the hydrolysis tower and the lactic acid recovery tower are used in a combined way; and the condenser of the methanol recovery tower is thermally integrated and coupled with the reboiler of the hydrolysis reaction section tower kettle of the hydrolysis tower, so that the energy consumption is saved.
The method has low requirements on the purity of crude lactic acid and methanol, easily obtained raw materials, stable product quality and high yield, and has remarkable practicability and economic benefit.
Drawings
Fig. 1 shows a schematic diagram of a method and apparatus for refining lactic acid monomer according to an embodiment of the present invention.
Reference numerals illustrate:
01-preheater, 02-reactor, 03-hydrolysis tower reboiler, 04-hydrolysis tower coupling reboiler, 05-hydrolysis tower, 06-hydrolysis tower condenser, 07-hydrolysis tower reflux drum, 08-lactic acid recovery tower reboiler, 09-lactic acid recovery tower, 10-lactic acid recovery tower condenser, 11-lactic acid recovery tower reflux drum, 12-refining tower reboiler, 13-refining tower, 14-refining tower condenser, 15-refining tower reflux drum, 16-methanol recovery tower reboiler, 17-methanol recovery tower, 18-methanol recovery tower subcooler, 19-methanol recovery tower reflux drum.
Detailed Description
Unless defined otherwise, technical terms used in the following examples have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains. It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.
According to an exemplary embodiment of the present invention, a method and apparatus for purifying lactic acid monomers are provided. The apparatus for purifying lactic acid monomer by the method of the present invention, as shown in FIG. 1, comprises a preheater (01), a reactor (02), a hydrolysis tower reboiler (03), a hydrolysis tower coupling reboiler (04), a hydrolysis tower (05), a hydrolysis tower condenser (06), a hydrolysis tower reflux drum (07), a lactic acid recovery tower reboiler (08), a lactic acid recovery tower (09), a lactic acid recovery tower condenser (10), a lactic acid recovery tower reflux drum (11), a purification tower reboiler (12), a purification tower (13), a purification tower condenser (14), a purification tower reflux drum (15), a methanol recovery tower reboiler (16), a methanol recovery tower (17), a methanol recovery tower subcooler (18), and a methanol recovery tower reflux drum (19).
The reactor (02) is provided with a crude lactic acid and methanol inlet, a lactic acid and methanol recovery inlet and a reaction product outlet.
The outlet of the reactor (02) is connected with the inlet of the hydrolysis tower (05), the gas phase outlet at the top of the hydrolysis tower (05) is connected with the inlet of the hydrolysis tower condenser (06), and the outlet of the hydrolysis tower condenser (06) is connected with the inlet of the hydrolysis tower reflux drum (07).
The outlet of the hydrolysis tower reflux tank (07) is connected with the inlet of the methanol recovery tower (17), the outlet of the methanol recovery tower reflux tank (19) is connected with the methanol inlet of the reactor (02), the outlet of the methanol recovery tower reflux tank (19) is provided with a collecting outlet, and if the mass fraction of the methanol recovered from the tower top is lower than 80% and is required to be discharged, the methanol is collected from the side line and returned to the methanol inlet of the reactor (02).
The hydrolysis tower (05) hydrolysis section tower cauldron export is connected with the separation section entry in advance of refining tower (13), refined lactic acid product is extracted to refining tower (13) side stream discharge section middle part side, refining tower (13) top gas phase export links to each other with refining tower condenser (14) entry, refining tower condenser (14) export links to each other with refining tower reflux drum (15) entry, refining tower reflux drum (15) export links to each other with hydrolysis tower (05) separation section tower cauldron entry in advance, refining tower (15) tower cauldron export leaves the export, if heavy component content is more, needs to arrange outward.
The hydrolysis tower (05) is connected with the inlet of the lactic acid recovery tower (09), the gas phase outlet at the top of the lactic acid recovery tower (09) is connected with the inlet of the lactic acid recovery tower condenser (10), the outlet of the lactic acid recovery tower condenser (10) is connected with the inlet of the lactic acid recovery tower reflux tank (11), the outlet of the lactic acid recovery tower reflux tank (11) is connected with the inlet of the hydrolysis tower (05) is connected with the inlet of the lactic acid recovery tower, the outlet of the lactic acid recovery tower (09) is connected with the lactic acid inlet of the reactor (02), and the outlet is reserved at the outlet of the lactic acid recovery tower (09), and if the mass fraction of the recovered lactic acid is lower than 50% and is required to be discharged.
The hydrolysis tower (05) adopts a partition tower, the inside of the tower is divided into two vertical spaces (unequal proportion) by a partition, the lower end of the partition is connected to a tower kettle, the tower kettle is also divided into two vertical spaces, the upper end of the partition is connected to the middle upper part of the tower, so that a public rectifying section is arranged on the upper part of the partition, 2 sections of 4-meter high-efficiency structured packing is arranged on the public rectifying section, the pre-separation section is arranged on the same side with the feeding, 4 sections of 4-meter high-efficiency structured packing is arranged on the other side of the partition, catalytic packing is arranged on the upper part and the lower part of the partition, 1 section of high-efficiency structured packing is arranged on the middle 2 sections of high-4-meter hydrolysis catalytic packing, and the arranged catalytic packing is formed by combining a strong acid cation exchange resin catalyst and silk screen packing according to a hollow structure.
The refining tower (15) adopts a partition tower, the inside of the tower is divided into two vertical spaces (unequal proportion) by a partition, the lower end of the partition is arranged at the middle lower part of the tower, the upper end of the partition is arranged at the middle upper part of the tower, the public rectifying section is arranged at the upper part of the partition, 2 sections of high-efficiency structured packing with the height of 4 meters are arranged at the same side of the pre-separating section and the feeding, 4 sections of high-efficiency structured packing with the height of 4 meters are arranged at the upper part of the 2 sections of packing at the feeding position (from top to bottom), 4 sections of high-efficiency structured packing with the height of 4 meters are arranged at the other side of the partition at the side of the side draw-off section, 2 sections of packing at the upper part of the discharging position (from top to bottom) and 2 sections of high-efficiency structured packing with the height of 4 meters are arranged at the lower part of the partition.
The lactic acid recovery tower and the methanol recovery tower are all filled with efficient structured packing.
By applying the technical scheme of the invention, the refining method of the lactic acid monomer comprises the following operation steps: s1, preheating crude lactic acid and methanol, and sending the crude lactic acid and methanol into a reactor to perform esterification reaction under the action of a catalyst to obtain a reaction product containing methyl lactate; s2, sending the reaction product into a hydrolysis tower for separation and hydrolysis, extracting unreacted lactic acid and methyl lactate from the bottom of a pre-separation section tower, extracting purified lactic acid from the bottom of the hydrolysis section tower, and extracting methanol-containing materials from the top of the hydrolysis section tower; s3, delivering the purified lactic acid into a refining tower to remove light components and heavy components, so as to obtain a lactic acid product; s4, feeding the lactic acid and methyl lactate extracted from the hydrolysis tower into a lactic acid recovery unit, returning the recovered lactic acid to the reactor, and returning the recovered methyl lactate to the hydrolysis tower; s5, feeding the methanol-containing material into a methanol recovery unit, and returning the recovered methanol to the reactor.
Further, in the step S1, the mass concentration of the raw material lactic acid is 0.75 or more, the mass concentration of the raw material methanol is 0.9 or more, and the feeding mole ratio of the methanol to the lactic acid is 2-10: 1.
Preferably, the esterification catalyst contained in the reactor is strong acid cation exchange resin, has high catalytic efficiency, and is particularly suitable for the application of the reaction of the invention in industry.
Preferably, the operating temperature of the reactor is controlled between 70 and 130 ℃, the operating pressure is controlled between 200 and 900kPa, the reaction is facilitated under the conditions of the pressure and the temperature range, and the conversion rate reaches more than 70 percent.
Preferably, the operation pressure at the top of the hydrolysis tower is controlled to be 5-15 kPa, the operation temperature at the top of the hydrolysis tower is controlled to be 40-75 ℃, and the reflux feed ratio is controlled to be 0.5-2.
In order to improve the product quality and reduce the energy consumption, the temperature of the tower bottom and the temperature of the tower top are controlled by controlling the extraction amount and the operation pressure of the tower bottom of the pre-separation section of the hydrolysis tower, the temperature of the tower bottom is not higher than 130 ℃, and the temperature of the tower top is not lower than 40 ℃.
Wherein, the material that is extracted from the tower cauldron of hydrolysising tower preseparation section is sent into lactic acid recovery tower, through adopting lower operating pressure to the recovery of lactic acid, and the material that is extracted from the tower top of hydrolysising tower is sent into the recovery of methanol tower and is retrieved methyl alcohol to this improves the yield of raw materials.
The top operation temperature of the lactic acid recovery tower is controlled at 70-100 ℃, the top operation pressure is controlled at 1-5 kPa, and the reflux feed ratio is 1-5.
The operation temperature of the top of the methanol recovery tower is controlled to be 120-140 ℃, the operation pressure of the top of the tower is controlled to be 400-650 kPa, and the reflux feed ratio is 2-5.
Preferably, the top operation temperature of the refining tower is controlled to be 20-80 ℃, the top operation pressure is controlled to be 1-15 kPa, and the reflux feed ratio is 3-9.
In the step S2, the reaction product from the reactor is sent to a pre-separation section of the hydrolysis tower, the temperature control of the pre-separation section of the hydrolysis tower is realized by adopting a tower kettle feeding mode, the larger the extraction flow is, the higher the content of methyl lactate, methanol and water is, the lower the temperature is, the recovered lactic acid is returned to the reactor (or part of the lactic acid is discharged outside), and the recovered methyl lactate is returned to the hydrolysis tower.
In order to save energy consumption, the tower bottom reboilers of the hydrolysis reaction section of the methanol recovery tower and the hydrolysis tower are in thermal coupling, namely, gas phase at the top of the methanol tower provides a heat source for the coupling reboilers of the hydrolysis tower.
In addition, analytical determination of relevant components is performed in the process:
(1) D-lactic acid and L-lactic acid content determination: HPLC was used and the chromatographic detection conditions were: the chromatographic column is an HPX-87H organic acid analysis column, the column temperature is 65 ℃, the detection wavelength is 210nm, the mobile phase is 5mmol/L sulfuric acid solution, the flow rate is 0.8mL/min, and the sample injection amount is 10 mu L. All data are averages of 3 replicates.
(2) Measurement of optical purity of lactic acid monomer: HPLC was used and the chromatographic detection conditions were: the chromatographic column is an Astec CLC-L optical purity analysis column, the column temperature is 25 ℃, the detection wavelength is 254nm, the mobile phase is 5mmol/L concentration copper sulfate solution, the flow rate is 1mL/min, and the sample injection amount is 10 mu L.
Example 1
Raw material lactic acid mass composition: d-lactic acid 0.75%, water 0.1%, light impurity 0.1%, heavy impurity 0.05%.
Methanol mass composition: methanol 0.9%, water 0.09%, and other impurities 0.01%.
The method for refining lactic acid monomer provided by the invention comprises the following operation steps:
(1) Mixing crude lactic acid with methanol in a molar ratio of 10:1, preheating the preheater to 130 ℃, and sending the mixture into a reactor for esterification reaction, wherein the reaction temperature is 130 ℃, so as to obtain an esterification reaction product.
(2) And (3) delivering the esterification reaction product into a hydrolysis tower for pre-separation Duan Dafu, wherein the reflux feed ratio is 2, the tower top temperature is 75 ℃, the temperature of a pre-separation tower kettle is 125 ℃, the temperature of the hydrolysis tower kettle is 110 ℃, the material containing 70% of methanol in mass fraction is extracted from the tower top, and the purified product lactic acid is extracted from the hydrolysis tower kettle in mass fraction of 91%.
(3) Feeding the purified lactic acid into a refining tower, wherein the operation pressure is 15kPa, the tower top temperature is 20 ℃, the refined lactic acid is extracted from the side line, and the chemical purity of the D-lactic acid monomer is higher than 0.9999 and the optical purity of the D-lactic acid monomer is higher than 0.999 through sampling analysis and determination.
(4) The methanol-containing and water materials extracted from the top of the hydrolysis tower are sent to a methanol recovery tower, light components are extracted from the top of the methanol recovery tower, the content of methanol is more than 95% from a side line of the methanol recovery tower, waste liquid is extracted from the tower bottom of the methanol recovery tower, the operating pressure of the methanol recovery tower is 650kPa, and the temperature of the top of the methanol recovery tower is 120 ℃.
(5) The material containing lactic acid and methyl lactate extracted from the tower bottom of the pre-separation section of the hydrolysis tower is sent into a lactic acid recovery tower, the operation pressure of the lactic acid recovery tower is 1kPa, the reflux ratio is 5, the temperature of the tower top is 70 ℃, the methyl lactate extracted from the tower top returns to the hydrolysis tower, the heavy component containing lactic acid is extracted from the tower bottom, 85% returns to the reactor, and 15% is extracted.
(6) The yield of lactic acid in the crude lactic acid is more than 90%, and the loss rate of methanol is less than 10%.
Example 2
Raw material lactic acid mass composition: d-lactic acid 0.95%, water 0.02% and other impurities 0.03%.
Methanol mass composition: methanol 0.95% and water 0.05%.
The method for refining lactic acid monomer provided by the invention comprises the following operation steps:
(1) Mixing the crude lactic acid with methanol, wherein the molar ratio of the methanol to the lactic acid is 2:1, preheating to 70 ℃ by a preheater, and sending the mixture into a reactor for esterification reaction, wherein the reaction temperature is 70 ℃, thus obtaining an esterification reaction product.
(2) And (3) delivering the esterification reaction product into a hydrolysis tower for pre-separation Duan Dafu, wherein the reflux feed ratio is 0.5, the tower top temperature is 40 ℃, the temperature of a pre-separation tower kettle is 115 ℃, the temperature of the hydrolysis tower kettle is 112 ℃, the tower top is used for extracting a material containing 85% of methanol by mass, and the hydrolysis tower kettle is used for extracting a purified product lactic acid by mass of 93%.
(3) Feeding the purified lactic acid into a refining tower, wherein the operating pressure of the refining tower is 1kPa, the temperature of the tower top is 55 ℃, the refined lactic acid is extracted from the side line, the chemical purity of the D-lactic acid monomer is higher than 0.9999, and the optical purity of the D-lactic acid monomer is higher than 0.999.
(4) The methanol and water-containing material extracted from the top of the hydrolysis tower is sent into a methanol recovery tower, the mass fraction of the methanol extracted from the top of the tower is more than 0.95, the methanol is returned to the reactor, the waste liquid is extracted from the tower kettle, the operation pressure of the methanol recovery tower is 550kPa, and the temperature of the top of the tower is 130 ℃.
(5) The material containing lactic acid and methyl lactate extracted from the tower kettle of the pre-separation section of the hydrolysis tower is sent into a lactic acid recovery tower, the operation pressure of the lactic acid recovery tower is 5kPa, the reflux ratio is 1, the temperature of the tower top is 85 ℃, the methyl lactate extracted from the tower top returns to the hydrolysis tower, the heavy component containing lactic acid is extracted from the tower kettle, 98% returns to the reactor, and 2% is extracted.
(6) The yield of lactic acid in the crude lactic acid is 98% or more, and the loss rate of methanol is 2% or less.
Example 3
Raw material lactic acid mass composition: l-lactic acid 0.80%, water 0.1%, light impurity 0.05%, heavy impurity 0.05%.
Methanol mass composition: methanol 0.98% and water 0.02%.
The method for refining lactic acid monomer provided by the invention comprises the following operation steps:
(1) Mixing crude lactic acid with methanol, wherein the molar ratio of the methanol to the lactic acid is 5:1, preheating to 90 ℃ by a preheater, and sending the mixture into a reactor for esterification reaction, wherein the reaction temperature is 90 ℃, thus obtaining an esterification reaction product.
(2) And (3) delivering the esterification reaction product into a hydrolysis tower for pre-separation Duan Dafu, wherein the reflux feed ratio is 1, the tower top temperature is 50 ℃, the temperature of a pre-separation tower kettle is 110 ℃, the temperature of the hydrolysis tower kettle is 112 ℃, the tower top is used for extracting a material containing 85% of methanol in mass percent, and the hydrolysis tower kettle is used for extracting purified lactic acid in mass percent of 85%.
(3) Feeding the purified lactic acid into a refining tower, wherein the operating pressure of the refining tower is 2kPa, the temperature of the tower top is 80 ℃, the refined lactic acid is extracted from the side line, the chemical purity of the L-lactic acid monomer is higher than 0.9999, and the optical purity of the L-lactic acid monomer is higher than 0.999.
(4) The methanol and water-containing material extracted from the top of the hydrolysis tower is sent into a methanol recovery tower, the mass fraction of the methanol extracted from the top of the tower is more than 0.95, the methanol is returned to the reactor, the waste liquid is extracted from the tower kettle, the operating pressure of the methanol recovery tower is 650kPa, and the temperature of the top of the tower is 120 ℃.
(5) The material containing lactic acid and methyl lactate extracted from the tower bottom of the pre-separation section of the hydrolysis tower is sent into a lactic acid recovery tower, the operation pressure of the lactic acid recovery tower is 2kPa, the temperature of the tower top is 100 ℃, the methyl lactate extracted from the tower top returns to the hydrolysis tower, the heavy component containing lactic acid is extracted from the tower bottom, 95% returns to the reactor, and 5% is extracted.
(6) The yield of lactic acid in the crude lactic acid is 95% or more, and the loss rate of methanol is 5% or less.
Example 4
Raw material lactic acid mass composition: d-lactic acid 0.92% and water 0.08%.
Ethanol mass composition: ethanol 0.95% and water 0.05%.
The method for refining lactic acid monomer provided by the invention comprises the following operation steps:
(1) Mixing crude lactic acid with ethanol, wherein the molar ratio of the ethanol to the lactic acid is 3:1, preheating to 90 ℃ by a preheater, and sending the mixture into a reactor for esterification reaction, wherein the reaction temperature is 90 ℃, thus obtaining an esterification reaction product.
(2) And (3) delivering the esterification reaction product into a hydrolysis tower for pre-separation Duan Dafu, wherein the reflux feed ratio is 1.5, the tower top temperature is 51 ℃, the temperature of a pre-separation tower kettle is 115 ℃, the temperature of the hydrolysis tower kettle is 112 ℃, the tower top is used for extracting materials containing 0.85 mass fraction of ethanol, and the mass fraction of the purified product lactic acid is extracted from the pre-separation tower kettle and is above 0.9.
(3) Feeding the purified lactic acid into a refining tower, wherein the operating pressure of the refining tower is 1kPa, the temperature of the tower top is 55 ℃, the refined lactic acid is extracted from the side line, the chemical purity of the D-lactic acid monomer is higher than 0.9999, and the optical purity of the D-lactic acid monomer is higher than 0.999.
(4) The ethanol and water-containing materials extracted from the top of the hydrolysis tower are sent into an ethanol recovery tower, ethanol is extracted from the top of the tower, the ethanol content is more than 95 percent, the materials are returned to the reactor, waste liquid is extracted from the tower kettle, the operating pressure of the ethanol recovery tower is 650kPa, and the temperature of the top of the tower is 125 ℃.
(5) The materials containing lactic acid and ethyl lactate extracted from the kettle of the pre-separation section of the hydrolysis tower are sent into a lactic acid recovery tower, the operation pressure of the lactic acid recovery tower is 1kPa, the temperature of the top of the tower is 75 ℃, the ethanol ester of lactic acid extracted from the top of the tower returns to the hydrolysis tower, the heavy component containing lactic acid is extracted from the kettle of the tower, 95% of the heavy component returns to the reactor, and 5% of the heavy component is extracted from the outside.
(6) The yield of lactic acid in the crude lactic acid is above 95%, and the loss rate of ethanol is below 3%.
Moreover, by adopting the technology and the equipment provided by the invention, the hydrolysis tower separates the methanol and the lactic acid and hydrolyzes and combines the methyl lactate into one tower, the refining tower combines the lactic acid light component removing tower and the lactic acid heavy component removing tower into one tower, compared with the traditional process and equipment, two towers and related equipment (a condenser, a tank and a pump) are saved, the equipment cost is saved by about 15%, and a thermal coupling mode of the methanol recovery tower and the refining tower is adopted, so that the methanol recovery tower provides a heat source for a reboiler of the refining tower, and the consumption per ton of products is saved by 0.59 Gcal/hour.
The technology and the equipment are not only suitable for preparing the lactic acid by esterification-hydrolysis reaction of crude lactic acid and lower alcohol (methanol, ethanol and the like), but also can be popularized to the related fields. Modifications and combinations of the described methods and apparatus may be made by those skilled in the relevant art to practice the teachings of the invention without departing from the spirit or scope thereof. It is specifically intended that all modifications, equivalents, improvements and modifications falling within the spirit and principles of the invention be included within the scope of the invention.
Claims (4)
1. An apparatus for refining lactic acid monomer, characterized by comprising: the device comprises a preheater, a reactor, a hydrolysis tower reboiler, a hydrolysis tower coupling reboiler, a hydrolysis tower condenser, a hydrolysis tower reflux tank, a lactic acid recovery tower reboiler, a lactic acid recovery tower condenser, a lactic acid recovery tower reflux tank, a refining tower reboiler, a refining tower condenser, a refining tower reflux tank, a methanol recovery tower reboiler, a methanol recovery tower subcooler and a methanol recovery tower reflux tank; the outlet of the preheater is connected with the inlet of the reactor, the outlet of the reactor is connected with the inlet of the hydrolysis tower, the outlet of the top of the hydrolysis tower is connected with the inlet of the hydrolysis tower condenser, and the outlet of the hydrolysis tower condenser is connected with the reflux tank of the hydrolysis tower; the outlet of the reflux tank of the hydrolysis tower is connected with the inlet of the methanol recovery tower, the outlet of the top of the methanol recovery tower is connected with the hot side inlet of the coupling reboiler of the hydrolysis tower, and the hot side outlet of the coupling reboiler of the hydrolysis tower is connected with the inlet of the subcooler of the methanol recovery tower; the outlet of the hydrolysis tower pre-separation tower kettle is connected with the inlet of the lactic acid recovery tower, and the gas phase outlet of the top of the lactic acid recovery tower is connected with the inlet of the lactic acid recovery tower condenser; the tower bottom outlet of the hydrolysis section of the hydrolysis tower is connected with the inlet of the refining tower, and the tower top outlet of the refining tower is connected with the inlet of the condenser of the refining tower;
the hydrolysis tower adopts a partition tower, the inside of the tower is divided into two vertical spaces by a partition plate, the pre-separation section is on the same side as the feeding, the hydrolysis section is arranged on the other side of the partition plate, and catalytic filler is formed by combining a strong acid cation exchange resin catalyst and a silk screen filler according to a hollow structure; the operation pressure of the top of the hydrolysis tower is 5-15 kPa, the operation temperature of the top of the hydrolysis tower is 40-75 ℃, and the reflux feed ratio is 0.5-2.
2. The apparatus of claim 1, wherein the refining column is a divided wall column, the dividing wall divides the interior of the column into two vertical spaces, the pre-separation section is on the same side of the dividing wall as the feed, and the side discharge section is on the other side of the dividing wall; the operation pressure of the top of the refining tower is 1-15 kPa, the operation temperature of the top of the refining tower is 20-80 ℃, and the reflux feed ratio is 3-9.
3. The apparatus according to claim 2, wherein the operation temperature at the top of the lactic acid recovery column is 70 to 100 ℃, the operation pressure at the top of the column is 1 to 5 kPa, and the reflux-feed ratio is 1 to 5; the operation temperature of the top of the methanol recovery tower is 120-140 ℃, the operation pressure of the top of the tower is 400-650 kPa, and the reflux feed ratio is 2-5.
4. The apparatus according to claim 2, characterized in that: the refining tower, the lactic acid recovery tower and the methanol recovery tower all adopt structured packing, and the hydrolysis tower adopts structured packing except catalytic packing.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101492367A (en) * | 2009-03-11 | 2009-07-29 | 合肥工业大学 | Method for fine purification of lactic acid |
| CN110357771A (en) * | 2018-04-09 | 2019-10-22 | 中国石化扬子石油化工有限公司 | A kind of partition tower process of methyl lactate hydrolysis rectifying |
| CN113603585A (en) * | 2021-09-23 | 2021-11-05 | 福州大学 | Continuous production process of ultra-pure methyl lactate |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101492367A (en) * | 2009-03-11 | 2009-07-29 | 合肥工业大学 | Method for fine purification of lactic acid |
| CN110357771A (en) * | 2018-04-09 | 2019-10-22 | 中国石化扬子石油化工有限公司 | A kind of partition tower process of methyl lactate hydrolysis rectifying |
| CN113603585A (en) * | 2021-09-23 | 2021-11-05 | 福州大学 | Continuous production process of ultra-pure methyl lactate |
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