CN112521265B - Method for continuously producing glycollic acid - Google Patents
Method for continuously producing glycollic acid Download PDFInfo
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- CN112521265B CN112521265B CN202011447680.3A CN202011447680A CN112521265B CN 112521265 B CN112521265 B CN 112521265B CN 202011447680 A CN202011447680 A CN 202011447680A CN 112521265 B CN112521265 B CN 112521265B
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/09—Preparation of carboxylic acids or their salts, halides or anhydrides from carboxylic acid esters or lactones
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- 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
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/30—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group
- C07C67/313—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group by introduction of doubly bound oxygen containing functional groups, e.g. carboxyl groups
Abstract
The invention provides a method for continuously producing glycolic acid, which comprises the following steps: A) after mixing and preheating dimethyl oxalate and water, carrying out autocatalysis semi-hydrolysis reaction, and rectifying and purifying the obtained hydrolysate to obtain monomethyl oxalate; B) and C) carrying out catalytic hydrogenation reaction on the monomethyl oxalate obtained in the step A) and hydrogen under the condition of a catalyst, and rectifying and purifying a reaction product to obtain the glycolic acid. The invention adopts a process of hydrolysis and hydrogenation, and the hydrolysis process is an autocatalytic semi-hydrolysis reaction, so that the control is easier compared with the hydrolysis reaction adopted in industry, the amount of byproducts generated by the reaction is less, and the product yield is greatly improved; the hydrogenation reaction condition of the monomethyl oxalate is milder; the hydrogenation reaction has no side reaction, the product in the material obtained by the reaction is easy to separate, and the product purity is high; the by-product oxalic acid can be directly sold as a product, the generation of waste materials is reduced, and the green production principle is followed.
Description
Technical Field
The invention belongs to the technical field of organic synthesis, and particularly relates to a method for continuously producing glycolic acid.
Background
Glycolic acid has been used mainly for the production of boiler scale removers, cleaning agents, and the like. In recent years, they have been widely used as cosmetics and pharmaceuticals, and have also attracted attention as a raw material for polyglycolic acid. Glycolic acid is useful for the preparation of high molecular weight polyglycolic acid. Although traditional high polymer materials such as PET, PE, PP, PS and the like bring much convenience to the life of common people and play an important role in social and economic development, serious white pollution is caused because recycling is incomplete and the traditional high polymer materials cannot be degraded or are difficult to degrade in the earth environment, plastic limit orders are issued in succession in various countries and regions with increasing importance of the society on environmental protection, and the development of the replacement of the traditional non-degradable high polymer materials by degradable and environment-friendly high polymer materials becomes an important research direction.
At present, the production process of glycolic acid in industry mainly adopts chloroacetic acid hydrolysis method and formaldehyde carbonylation method.
(1) And (3) chloroacetic acid hydrolysis method: the glycolic acid is prepared by the sodium chloroacetate and the sodium hydroxide through catalytic hydrolysis, the yield can reach more than 95 percent, and the mass fraction of the product can reach more than 98 percent. The method has low requirements on reaction raw materials, impurities in the raw materials, namely dichloroacetic acid, are hydrolyzed into glycolic acid, chloroacetic acid has high toxicity and strong corrosivity and is not beneficial to environmental protection, and the product contains chloride ions.
(2) A formaldehyde carbonylation method: the method is the most important industrialized method abroad at present. And synthesizing the glycolic acid by formaldehyde, CO and water under the action of a catalyst. The yield of glycolic acid at 90MPa is close to 90%, and the method has low cost of raw materials, but has high requirements on equipment, and the separation and purification of products are complicated.
Disclosure of Invention
The invention aims to provide a method for continuously producing glycolic acid, which is simple, efficient and good in economic benefit.
The invention provides a method for continuously producing glycolic acid, which comprises the following steps:
A) after mixing and preheating dimethyl oxalate and water, carrying out autocatalysis semi-hydrolysis reaction, and rectifying and purifying the obtained hydrolysate to obtain monomethyl oxalate;
B) and C) carrying out catalytic hydrogenation reaction on the monomethyl oxalate obtained in the step A) and hydrogen under the condition of a catalyst, and rectifying and purifying a reaction product to obtain the glycolic acid.
Preferably, the autocatalytic semi-hydrolysis reaction is carried out under the condition of stirring, and the temperature of the autocatalytic semi-hydrolysis reaction is 30-120 ℃; the time of the autocatalysis semi-hydrolysis reaction is 40-70 min.
Preferably, the rectification purification in the step a) sequentially comprises atmospheric rectification and vacuum rectification.
Preferably, water is separated by normal pressure rectification, and the separated water is used as a raw material and returns to participate in hydrolysis reaction;
and (3) performing reduced pressure distillation to obtain dimethyl oxalate, residual water and methanol, and returning the separated dimethyl oxalate and water to participate in hydrolysis reaction.
Preferably, the molar ratio of the dimethyl oxalate to the water is (10-60): 1.
preferably, the catalyst comprises a carrier and an active metal loaded on the carrier, wherein the active metal is one or more of Cu, Ni, Zn, Mo, Pd and Pt; the carrier is ZSM-5 molecular sieve, ZSM-22 molecular sieve, ZSM-23 molecular sieve or modified alumina.
Preferably, the temperature of the hydrogenation reaction is 100-150 ℃; the mass airspeed of the oxalic acid monomethyl ester is 0.1-5 h -1 (ii) a The pressure of the hydrogenation reaction is 0.1-5.0 MPa.
Preferably, the molar ratio of the hydrogen to the monomethyl oxalate is (10-200): 1.
preferably, the hydrogenation reaction in step B) is carried out in a fixed bed reactor.
Preferably, the rectification purification in step B) comprises one or more atmospheric rectification;
and the monomethyl oxalate obtained by rectification, purification and separation is returned to participate in the hydrogenation reaction.
The invention provides a method for continuously producing glycolic acid, which comprises the following steps: A) after mixing and preheating dimethyl oxalate and water, carrying out autocatalysis semi-hydrolysis reaction, and rectifying and purifying the obtained hydrolysate to obtain monomethyl oxalate; B) and C) carrying out catalytic hydrogenation reaction on the monomethyl oxalate obtained in the step A) and hydrogen under the condition of a catalyst, and rectifying and purifying a reaction product to obtain the glycolic acid. The invention adopts a process of hydrolysis and hydrogenation, and the hydrolysis process is an autocatalytic semi-hydrolysis reaction, so that the control is easier compared with the hydrolysis reaction adopted in industry, the amount of byproducts generated by the reaction is less, and the product yield is greatly improved; the hydrogenation reaction condition of the monomethyl oxalate is milder, the energy consumption is reduced, and the requirement on equipment is low; the hydrogenation reaction has no side reaction, the product in the material obtained by the reaction is easy to separate, and the product purity is high; water and dimethyl oxalate obtained by distillation after the hydrolysis reaction and monomethyl oxalate obtained by distillation after the hydrogenation reaction can circularly flow back to the reactor to continuously participate in the reaction, and a byproduct, namely oxalic acid, can be directly sold as a product, so that the generation of waste is reduced, and the green production principle is followed.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a schematic diagram of the structure of a hydrolysis stage according to the present invention;
FIG. 2 is a schematic diagram of the apparatus of the hydrogenation zone of the present invention;
wherein, 1 is a hydrolysis reaction kettle, 2 is an atmospheric distillation tower I, 3 is an atmospheric distillation tower II, 4 is a vacuum distillation tower I, 5 is a vacuum distillation tower II, 6 is a material groove, 7 is a fixed bed reactor, 8 is an atmospheric distillation tower III, and 9 is an atmospheric distillation tower IV.
Detailed Description
The invention provides a method for continuously producing glycolic acid, which comprises the following steps:
A) after mixing and preheating dimethyl oxalate and water, carrying out autocatalysis semi-hydrolysis reaction, and rectifying and purifying the obtained hydrolysate to obtain monomethyl oxalate;
B) and C) carrying out catalytic hydrogenation reaction on the monomethyl oxalate obtained in the step A) and hydrogen under the condition of a catalyst, and rectifying and purifying a reaction product to obtain the glycolic acid.
In the prior art, generally, dimethyl oxalate is subjected to hydrogenation reaction to obtain methyl glycolate, and then the methyl glycolate is further hydrolyzed to prepare a glycolic acid product. When dimethyl oxalate is hydrogenated, excessive hydrogenation is easily caused to generate ethylene glycol and ethanol by-products under the conditions of high temperature and high pressure, and the selectivity of methyl glycolate is low. The invention has the advantages of no need of considering the problem of excessive hydrogenation when the monomethyl oxalate is subjected to hydrogenation reaction, less by-products in the process and high yield of glycolic acid products.
By changing the sequence of hydrogenation and hydrolysis processes, the invention not only avoids the problem of excessive hydrogenation of dimethyl oxalate, but also is easier to carry out hydrogenation reaction because only one ester group in monomethyl oxalate is hydrogenated, the requirements of the reaction on temperature and pressure are correspondingly reduced, and the process energy consumption is reduced.
The method is divided into a hydrolysis section and a hydrogenation section; the hydrolysis section is an autocatalysis semi-hydrolysis reaction of dimethyl oxalate to prepare monomethyl oxalate; the hydrogenation section is used for preparing glycolic acid by catalytic hydrogenation of monomethyl oxalate.
In the invention, the device of the hydrolysis section comprises a mixed heat exchange tank, a hydrolysis reaction kettle, an atmospheric distillation tower I, an atmospheric distillation tower II, a vacuum distillation tower I and a vacuum distillation tower II;
the atmospheric distillation and the vacuum distillation of the hydrolysis section can also be provided with 1 or more than 2 atmospheric distillation towers and 1 or more than 2 vacuum distillation towers according to requirements.
According to the invention, firstly, the dimethyl oxalate and water are pumped into a mixing heat exchange tank for mixing and preheating, and then the mixture is continuously conveyed into a hydrolysis reaction kettle through a pipeline for an autocatalytic semi-hydrolysis reaction, wherein the reaction is carried out under strong stirring.
In the invention, the molar ratio of the dimethyl oxalate to the water is preferably (10-60): 1, more preferably (20 to 50): 1, most preferably (30-40): 1; the preheating temperature, namely the temperature of the autocatalytic semi-hydrolysis reaction, is preferably 30-120 ℃, more preferably 40-100 ℃, most preferably 50-90 ℃, and further preferably 50-70 ℃, and the time of the autocatalytic semi-hydrolysis reaction is preferably 40-70 min, and more preferably 50-60 min.
Since dimethyl oxalate can generate monomethyl oxalate and oxalic acid simultaneously in the hydrolysis process, but the monomethyl oxalate is unstable in property and the generation amount of the monomethyl oxalate is difficult to control, few reports of preparing and further utilizing monomethyl oxalate by hydrolysis of dimethyl oxalate exist, and industrial application is not carried out until now. Currently, the industrial use of dimethyl oxalate hydrolysis is commonly used to produce oxalic acid and methanol products. Since dimethyl oxalate undergoes a two-step hydrolysis process in the hydrolysis reaction: the first step is as follows: reacting one molecule of dimethyl oxalate with one molecule of water to generate monomethyl oxalate and methanol; the second step is that: one molecule of monomethyl oxalate reacts with one molecule of water to produce oxalic acid and methanol. Therefore, the invention controls the conversion rate of the hydrolysis conversion of the dimethyl oxalate into the monomethyl oxalate by controlling the raw material ratio of the dimethyl oxalate to the water in the hydrolysis reaction, and selects the optimal proportion which can ensure the conversion rate of the monomethyl oxalate to reach the maximum.
And maintaining the constant temperature of the system in the hydrolysis process, continuously introducing a reaction system in the hydrolysis reaction kettle into an atmospheric rectification tower I, an atmospheric rectification tower II, a vacuum rectification tower I and a vacuum rectification tower II which are sequentially connected in series when the conversion rate of the monomethyl oxalate is maximum, and rectifying, separating and purifying the reaction product to obtain the monomethyl oxalate.
The reaction system after the autocatalytic semi-hydrolysis contains oxalic acid monomethyl ester, methanol, oxalic acid, unreacted water and dimethyl oxalate, firstly enters a normal pressure rectifying tower I, the methanol is fractionated, the rest components continuously flow into a normal pressure rectifying tower II for dehydration, and after the water is dehydrated from the top of the tower, the water circularly flows back to a hydrolysis reaction kettle to continuously participate in the hydrolysis reaction. The rest components continuously flow into a decompression rectifying tower I from the bottom of the tower kettle through a pipeline, and dimethyl oxalate, water and methanol which are not completely separated in an atmospheric tower are distilled out from the top of the tower in the tower I in a light component form and circularly flow back to a hydrolysis reaction kettle to continuously carry out hydrolysis reaction. And the rest heavy components oxalic acid and oxalic acid monomethyl ester continuously flow into a decompression rectifying tower II from the bottom of the tower, and the oxalic acid monomethyl ester is distilled out from the top of the tower in a light component form and continuously flows into a hydrogenation reaction system through a pipeline. The main component of the residual material is oxalic acid and a small amount of pre-boiling water, the residual material is discharged into a material groove, and then the oxalic acid finished product can be obtained through crystallization.
In the invention, the top temperature of the atmospheric distillation tower I is 65-80 ℃, and preferably 70-75 ℃; the temperature of the tower kettle is 70-100 ℃, preferably 75-95 ℃, and more preferably 80-90 ℃;
the top temperature of the atmospheric distillation tower II is 100-105 ℃, the tower kettle temperature is 100-130 ℃, preferably 105-125 ℃, and more preferably 110-120 ℃;
the temperature of the tower I of the reduced pressure rectifying tower is controlled to be 70-100 ℃, preferably 75-95 ℃, and more preferably 80-90 ℃; the pressure is 1.5-10 KPa;
the temperature of the tower II of the reduced pressure rectifying tower is controlled to be 100-120 ℃, and preferably 105-115 ℃; the pressure is 1.0 to 5 KPa.
The hydrogenation section comprises a fixed bed reactor, and an atmospheric distillation tower III and an atmospheric distillation tower IV which are sequentially connected in series.
After the secondary atmospheric distillation and the secondary vacuum distillation of the hydrolysis section, the obtained monomethyl oxalate is introduced into a fixed bed reactor for catalytic hydrogenation reaction, and the reacted materials are rectified and purified to obtain the glycolic acid product.
In the invention, a catalyst is loaded in the fixed bed reactor, the catalyst is a carrier loaded with active metal, and the active metal is one or more of Cu, Ni, Zn, Mo, Pd and Pt; the carrier is ZSM-5 molecular sieve, ZSM-22 molecular sieve, ZSM-23 molecular sieve or modified alumina. The loading amount of the active metal on the carrier is preferably 3-8 wt%, more preferably 4-7 wt%, and most preferably 5-6 wt%.
The hydrogenation catalyst of the present invention may be a homogeneous catalyst, but the separation step of the catalyst is increased.
According to the invention, the monomethyl oxalate and hydrogen are preferably mixed and preheated, and then pass through a catalyst bed layer to carry out hydrogenation reaction under the action of a catalyst to obtain the glycolic acid.
In the present invention, the molar ratio of monomethyl oxalate to hydrogen is preferably 1: (10-200), more preferably 1: (50-150); specifically, in the embodiment of the present invention, the ratio may be 1: 50; the mixing and preheating temperature, namely the reaction temperature of catalytic hydrogenation, is preferably 100-150 ℃, more preferably 110-140 ℃, and most preferably 120-130 ℃; the mass space velocity of the oxalic acid monomethyl ester is preferably 0.1-5 h -1 More preferably 1 to 4 hours -1 Most preferably 2 to 3 hours -1 The pressure of the hydrogenation reaction is preferably 0.1-2 MPa, more preferably 0.5-1.8 MPa, and most preferably 1-1.5 MPa.
The material obtained after the hydrogenation reaction enters an atmospheric distillation tower III and an atmospheric distillation tower IV for distillation and purification, in the invention, the distillation and purification are realized by 2 atmospheric distillation towers, but in the actual production, 1 atmospheric distillation tower or more than two atmospheric distillation towers can be selected and used according to different production working conditions. Namely, the rectification purification comprises one-time atmospheric rectification or multiple times of atmospheric rectification, and the multiple times of atmospheric rectification are two or more times of atmospheric rectification.
And after the hydrogenation reaction is finished, obtaining materials comprising glycolic acid, methanol and unreacted monomethyl oxalate, continuously flowing the obtained materials into a normal-pressure rectifying tower III, taking the methanol as a light component to be separated from the top of the rectifying tower, continuously flowing the rest materials into a rectifying tower IV from the bottom of the tower kettle, taking the glycolic acid as the light component from the top of the tower, and recycling the monomethyl oxalate into a hydrogenation reactor from the bottom of the tower kettle to continuously participate in the hydrogenation reaction.
In the invention, the temperature of the atmospheric distillation tower III is 65-80 ℃, and preferably 70-75 ℃; the pressure is 0-10 KPa, preferably 1-8 KPa, more preferably 3-6 KPa; the temperature of the atmospheric distillation tower IV is 0-50 ℃, preferably 10-40 ℃, and more preferably 20-30 ℃; the pressure is 0 to 10KPa, preferably 1 to 8KPa, and more preferably 3 to 6 KPa.
Based on the process, the invention also provides a device for continuously producing the glycolic acid, which is matched with the process and comprises a mixed heat exchange tank, a hydrolysis reaction kettle, an atmospheric distillation tower I, an atmospheric distillation tower II, a vacuum distillation tower I, a vacuum distillation tower II, a fixed bed reactor, an atmospheric distillation tower III and an atmospheric distillation tower IV which are communicated in sequence.
And a power pump for providing flowing kinetic energy is also arranged between the reduced pressure rectifying tower II and the fixed bed reactor.
Preferably, the "communication" in the present invention may be a direct communication between the two apparatuses through a pipeline, or an indirect communication between the two apparatuses, that is, some functional devices are disposed on the communication pipeline between the two apparatuses, for example, a storage device such as a material tank is disposed on the communication pipeline between the vacuum distillation tower II and the fixed bed reactor, which are communicated with each other, for receiving, buffering and temporarily storing monomethyl oxalate.
Compared with the prior art, the continuous production method has the following advantages:
1) high conversion rate
The method comprises the following steps of carrying out hydrogenation reaction on dimethyl oxalate, taking hydrogen ions generated by water ionization as an initial catalyst to catalyze dimethyl oxalate to hydrolyze to generate monomethyl oxalate, further hydrolyzing a part of monomethyl oxalate to generate oxalic acid along with the increase of the concentration of the monomethyl oxalate, and taking the hydrogen ions generated by oxalic acid ionization as a main catalyst to catalyze dimethyl oxalate to hydrolyze to generate the monomethyl oxalate. The method can effectively control the hydrolysis process of the dimethyl oxalate, and control the hydrolysis rate by controlling the initial molar ratio of the water to the dimethyl oxalate so as to regulate and determine the optimal reaction process. The conversion rate of the oxalic acid monomethyl ester reaches the highest, and the generation amount of byproducts is reduced to the maximum.
2) Low cost
In the invention, dimethyl oxalate is used as a raw material, and a glycolic acid product is prepared by hydrolysis and hydrogenation processes. The raw materials used in the process are cheap and easily available. In addition, no catalyst is required to be additionally added in the hydrolysis reaction, so that the probability of mixing new impurities into the glycolic acid product is reduced by avoiding the separation and recovery of the catalyst in the later period, the purity of the obtained glycolic acid product is high, and the production cost is saved. Compared with the hydrogenation reaction condition of dimethyl oxalate adopted industrially, the hydrogenation reaction condition of monomethyl oxalate is milder, the energy consumption is reduced, and the requirement on equipment is low.
3) Simple process
In the invention, dimethyl oxalate is used as a raw material to prepare a glycollic acid product through hydrolysis and hydrogenation. In the process, no catalyst is required to be added in the hydrolysis reaction, so that the catalyst recovery and separation operation is reduced. The catalyst added in the hydrogenation reaction is a heterogeneous catalyst and consists of an active metal hydrogenation component and a carrier component, so that the catalyst is simple to recycle and can be recycled, and the production cost is reduced.
In order to further illustrate the present invention, the following examples are provided to describe the method for continuously producing glycolic acid according to the present invention in detail, but should not be construed as limiting the scope of the present invention.
Example 1
(1) Mixing dimethyl oxalate and water according to a molar ratio of 60: 1, mixing, preheating, and introducing into a hydrolysis reaction kettle for an autocatalytic semi-hydrolysis reaction at 50 ℃ for 40 min. Obtaining hydrolysis liquid containing monomethyl oxalate through hydrolysis reaction, and rectifying and purifying to obtain monomethyl oxalate, wherein the selectivity of the monomethyl oxalate is more than or equal to 95%. In addition, water and dimethyl oxalate separated by the atmospheric distillation and the reduced pressure distillation can be returned to the hydrolysis reaction kettle to continue to participate in the hydrolysis reaction.
(2) And (2) introducing the monomethyl oxalate obtained in the step (1) into a fixed bed reactor. Meanwhile, a certain amount of hydrogen is introduced so that the molar ratio of the monomethyl oxalate to the hydrogen is 1: 50. at 150 ℃, the pressure is 1MPa, and the mass space velocity of the oxalic acid monomethyl ester is 5h -1 Then, a Cu-loaded ZSM-5 molecular sieve is used as a catalyst to carry out catalytic hydrogenation reaction, and the glycolic acid product obtained by rectification and purification has the purity of more than or equal to 99.9 percent and the yield of more than or equal to 90 percent.
Example 2
(1) Mixing dimethyl oxalate and water according to a molar ratio of 30: 1, mixing, preheating, and introducing into a hydrolysis reaction kettle for an autocatalytic semi-hydrolysis reaction at 50 ℃ for 40 min. Obtaining hydrolysis liquid containing monomethyl oxalate through hydrolysis reaction, and rectifying and purifying to obtain monomethyl oxalate, wherein the selectivity of the monomethyl oxalate is more than or equal to 90%. In addition, water and dimethyl oxalate separated by the atmospheric distillation and the vacuum distillation can be returned to the hydrolysis reaction kettle to continue to participate in the hydrolysis reaction.
(2) And (2) introducing the monomethyl oxalate obtained in the step (1) into a fixed bed reactor. Meanwhile, a certain amount of hydrogen is introduced so that the molar ratio of the monomethyl oxalate to the hydrogen is 1: 50. at 120 ℃, the pressure is 2MPa, and the mass space velocity of the oxalic acid monomethyl ester is 0.1h -1 Then, ZSM-5 molecular sieve loaded with Ni is used as a catalyst to carry out catalytic hydrogenation reaction, and glycolic acid product obtained by rectification and purification has the purity of more than or equal to 99.6 percent and the yield of more than or equal to 90 percent.
Example 3
(1) Mixing dimethyl oxalate and water according to a molar ratio of 10: 1, preheating, and then introducing into a hydrolysis reaction kettle for an autocatalytic semi-hydrolysis reaction at the temperature of 50 ℃ for 40 min. Obtaining hydrolysis liquid containing monomethyl oxalate through hydrolysis reaction, and rectifying and purifying to obtain monomethyl oxalate, wherein the selectivity of the monomethyl oxalate is more than or equal to 90%. In addition, water and dimethyl oxalate separated by the atmospheric distillation and the vacuum distillation can be returned to the hydrolysis reaction kettle to continue to participate in the hydrolysis reaction.
(2) And (2) introducing the monomethyl oxalate obtained in the step (1) into a fixed bed reactor. Meanwhile, a certain amount of hydrogen is introduced so that the molar ratio of the monomethyl oxalate to the hydrogen is 1: 50. at the temperature of 120 ℃, the pressure of 1MPa and the mass space velocity of the oxalic acid monomethyl ester of 3h -1 Then, a Zn-loaded ZSM-5 molecular sieve is used as a catalyst to carry out catalytic hydrogenation reaction, and the glycolic acid product obtained by rectification and purification has the purity of more than or equal to 99.8 percent and the yield of more than or equal to 90 percent.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (8)
1. A method for the continuous production of glycolic acid comprising the steps of:
A) after mixing and preheating dimethyl oxalate and water, carrying out autocatalysis semi-hydrolysis reaction, and rectifying and purifying the obtained hydrolysate to obtain monomethyl oxalate;
the molar ratio of the dimethyl oxalate to the water is (10-60): 1; the autocatalytic semi-hydrolysis reaction is carried out under the condition of stirring, and the temperature of the autocatalytic semi-hydrolysis reaction is 30-120 ℃; the time of the autocatalytic semi-hydrolysis reaction is 40-70 min;
B) and C) carrying out catalytic hydrogenation reaction on the monomethyl oxalate obtained in the step A) and hydrogen under the condition of a catalyst, and rectifying and purifying a reaction product to obtain the glycolic acid.
2. The method according to claim 1, wherein the rectification purification in step a) comprises atmospheric rectification and vacuum rectification.
3. The method of claim 2, wherein the atmospheric distillation separates water, and the separated water is used as a raw material to be returned to the hydrolysis reaction;
and (3) performing reduced pressure distillation to obtain dimethyl oxalate, residual water and methanol, and returning the separated dimethyl oxalate and water to participate in hydrolysis reaction.
4. The method of claim 1, wherein the catalyst comprises a carrier and an active metal supported on the carrier, the active metal being one or more of Cu, Ni, Zn, Mo, Pd, Pt; the carrier is ZSM-5 molecular sieve, ZSM-22 molecular sieve, ZSM-23 molecular sieve or modified alumina.
5. The method according to claim 1, wherein the temperature of the hydrogenation reaction is 100 to 150 ℃; the mass airspeed of the oxalic acid monomethyl ester is 0.1-5 h -1 (ii) a The pressure of the hydrogenation reaction is 0.1-5.0 MPa.
6. The method according to claim 1, wherein the molar ratio of hydrogen to monomethyl oxalate is (10-200): 1.
7. the process according to claim 1, characterized in that the hydrogenation reaction in step B) is carried out in a fixed bed reactor.
8. The method according to claim 1, wherein the rectification purification in step B) comprises one or more atmospheric rectification;
and the monomethyl oxalate obtained by rectification, purification and separation is returned to participate in the hydrogenation reaction.
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| JP2005194242A (en) * | 2004-01-09 | 2005-07-21 | Nippon Shokubai Co Ltd | Method for producing glycolate |
| WO2006126626A1 (en) * | 2005-05-27 | 2006-11-30 | Asahi Kasei Chemicals Corporation | Method for producing glycolic acid |
| CN102001944B (en) * | 2010-10-27 | 2014-05-14 | 上海华谊（集团）公司 | Method for preparing glycolate by catalyzing oxalate under action of hydrogenation |
| WO2017134139A1 (en) * | 2016-02-04 | 2017-08-10 | Shell Internationale Research Maatschappij B.V. | A method of preparing glycolic acid (hoch2cooh) |
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