A process for the production of methyl glycolate

Abstract

The application discloses a production method of glycollic acid methyl ester, and belongs to the field of chemical product preparation. The production method comprises the following steps: mixing a raw material mixture containing methyl alkoxyl acetate and / or methoxyl acetic acid and low-carbon alcohol, contacting the raw material mixture with a catalyst in a reactor, and reacting to obtain glycollic acid methyl ester; the low-carbon alcohol is selected from methanol and / or ethanol. The production method can be carried out under normal pressure and anhydrous conditions, and separation energy consumption is saved. The process is simple, the catalyst is easy to obtain and low in price, and the production method has important industrial application prospects. The production method realizes efficient and clean utilization of coal resources, and has important significance for promoting the sustainable development of the coal chemical industry.

Description

Technical Field

[0001] This application relates to a method for producing methyl glycolate, which belongs to the field of chemical product preparation. Background Technology

[0002] With my country's increased control over non-degradable plastics, the demand for biodegradable plastics is growing across various sectors. Polyglycolic acid (PGA), a biodegradable plastic, is an aliphatic polyester polymer with the fewest carbon atoms and the fastest degradation rate. It can be prepared by the condensation of monomers such as methyl glycolate and glycolic acid. PGA degrades rapidly, with degradation products being water and carbon dioxide, which are harmless to humans and the environment. Furthermore, PGA is one of the few polymers that degrades rapidly in marine environments and has obtained certification as a safe biodegradable plastic material, showing promising industrialization prospects in fields such as biomedicine, oil and gas extraction, and packaging. Statistics show that the global market for PGA is approximately 1.2 to 1.8 million tons, with a market value of about US$5 billion. However, in my country, PGA is mainly imported. Therefore, developing PGA monomer synthesis processes with independent intellectual property rights is of great significance to the country's green and sustainable development.

[0003] Methyl glycolate, a key monomer in the production of PGA, can be prepared through various methods including chloroacetic acid hydrolysis, methyl formate-formaldehyde coupling, and dimethyl oxalate hydrogenation reduction. The chloroacetic acid hydrolysis method uses sodium hydroxide and chloroacetic acid as raw materials, reacting them thoroughly before adding methanol and then proceeding under an acidic catalyst to produce methyl glycolate. However, this method suffers from low yield and environmental pollution. The dimethyl oxalate hydrogenation reduction method reacts dimethyl oxalate with hydrogen to obtain the final product. This method offers advantages such as being environmentally friendly and having mild reaction conditions, and holds promise for large-scale industrial production in the future. However, current processes suffer from low catalyst conversion rates, poor stability, lengthy processes, and high costs, severely limiting their development. Therefore, there is an urgent need to develop new, green, economical, and efficient methyl glycolate synthesis processes. Summary of the Invention

[0004] According to one aspect of this application, a method for producing methyl glycolate is provided. This method uses methyl alkoxyacetate or methoxyacetic acid and a lower alcohol as raw materials, and an alcoholysis reaction can occur on a solid catalyst to directly generate methyl glycolate, with simple separation. The methyl glycolate production method provided in this application can be combined with coal-based routes for producing methylal and methylal carbonylation to produce methyl methoxyacetate, broadening the coal-to-oxygenated compound production routes and achieving efficient and clean utilization of coal resources, which is of great significance for promoting the sustainable development of the coal chemical industry. The method for producing methyl glycolate provided in this application uses a non-precious metal catalyst. The process is simple, the catalyst is readily available and inexpensive, and it has significant industrial application prospects.

[0005] A method for producing methyl glycolate, the method comprising:

[0006] A mixture of raw materials containing methyl alkoxyacetate and / or methoxyacetic acid and lower alcohols is reacted with a catalyst in a reactor to obtain methyl glycolate.

[0007] The lower alcohol is selected from methanol and / or ethanol.

[0008] Optionally, the catalyst is selected from at least one of solid acid catalysts and solid base catalysts.

[0009] Optionally, the solid acid catalyst is selected from at least one of acidic zeolite molecular sieve catalysts, acidic resin catalysts, and acidic alumina catalysts.

[0010] Optionally, the solid base catalyst is selected from at least one of hydrotalcite, anion exchange resin, and hydroxyapatite.

[0011] Optionally, the acidic zeolite molecular sieve catalyst comprises an acidic zeolite molecular sieve;

[0012] The acidic zeolite molecular sieve is selected from at least one of the following: acidic zeolite molecular sieves with MFI structure, acidic zeolite molecular sieves with MEL structure, acidic zeolite molecular sieves with MTT structure, acidic zeolite molecular sieves with TON structure, acidic zeolite molecular sieves with MWW structure, acidic zeolite molecular sieves with FER structure, acidic zeolite molecular sieves with MOR structure, acidic zeolite molecular sieves with EUO structure, acidic zeolite molecular sieves with BEA structure, and acidic zeolite molecular sieves with FAU structure.

[0013] Optionally, the acidic zeolite molecular sieve is selected from at least one of the following: hydrogen-form ZSM-5 molecular sieve, hydrogen-form ZSM-11 molecular sieve, hydrogen-form ZSM-23 molecular sieve, hydrogen-form ZSM-22 molecular sieve, hydrogen-form MCM-22 molecular sieve, hydrogen-form ZSM-35 molecular sieve, hydrogen-form MOR molecular sieve, hydrogen-form EU-1 molecular sieve, hydrogen-form Beta molecular sieve, and hydrogen-form Y molecular sieve.

[0014] Preferably, the acidic molecular sieve is selected from at least one of hydrogen-form ZSM-5 molecular sieve, hydrogen-form ZSM-11 molecular sieve, hydrogen-form MCM-22 molecular sieve, hydrogen-form ZSM-23 molecular sieve, hydrogen-form ZSM-22 molecular sieve, and hydrogen-form ZSM-35 molecular sieve.

[0015] Those skilled in the art can commercially purchase hydrogen-form zeolite molecular sieves, or prepare them using any suitable method in the prior art. This application does not limit the preparation method. A preferred method for preparing hydrogen-form zeolite molecular sieves is described below: Na-form molecular sieves are placed in a 0.5 mol / L to 1 mol / L NH4NO3 aqueous solution and subjected to ion exchange at room temperature to 90°C for 0.5 h to 10 h. The sieves are then washed with deionized water, and the above steps are repeated 1 to 3 times. The sieves are then dried at 80°C to 150°C and calcined at 500°C to 600°C to obtain the hydrogen-form zeolite molecular sieves.

[0016] Optionally, the silicon-to-aluminum molecular ratio of the acidic molecular sieve is 5 to 500.

[0017] Optionally, the silica-alumina molecular ratio of the acidic molecular sieve is independently selected from any value or a range between any two of 5, 10, 20, 50, 100, 150, 200, 250, 300, 350, 400, 450 and 500.

[0018] Optionally, the acidic zeolite molecular sieve catalyst further includes a matrix;

[0019] The matrix is ​​selected from at least one of alumina, silicon dioxide, kaolin, and magnesium oxide.

[0020] The acidic zeolite molecular sieve has a mass content of 10-100% in the catalyst.

[0021] Those skilled in the art can prepare matrix-containing solid acid catalysts using any suitable method in the prior art, and this application does not limit the preparation method. The following describes a preferred method for preparing a matrix-containing solid acid catalyst: acidic molecular sieve, matrix, and guar gum powder are mixed in a mass ratio of 770:24:1, 10% nitric acid is added and kneaded, the mixture is shaped by extrusion, and calcined at 500–600°C to obtain the matrix-containing solid acid catalyst.

[0022] Optionally, the acidic resin catalyst is selected from at least one of Amberlyst-15 and Nafion;

[0023] The acidic alumina catalyst is selected from γ-alumina.

[0024] Optionally, the hydrotalcite is selected from Mg-Al hydrotalcite;

[0025] The anion exchange resin is selected from Amberlyst A26.

[0026] Optionally, the catalyst may be activated before use. Those skilled in the art can perform activation using any suitable method available in the prior art; this application does not limit the activation method. For example, activation with nitrogen at 40 mL / min at 450°C for 2 hours.

[0027] Optionally, the methyl alkoxyacetate is selected from at least one of methyl methoxyacetate, methyl ethoxyacetate, methyl propoxyacetate, and methyl butoxyacetate.

[0028] Optionally, the raw material mixture consists of methyl alkoxyacetate and / or methoxyacetic acid and lower alcohols.

[0029] Optionally, the mass hourly space velocity (WHSV) of methyl alkoxyacetate and / or methoxyacetic acid is 0.1 h⁻¹. -1 ~5.0h -1 The molar ratio of methyl alkoxyacetate and / or methoxyacetic acid to lower alcohols is 1:20 to 20:1.

[0030] Optionally, the mass hourly space velocity (WHSV) of methyl alkoxyacetate and / or methoxyacetic acid is 0.1 h⁻¹. -1 ~3.0h -1 The molar ratio of methyl alkoxyacetate and / or methoxyacetic acid and lower alcohols is 1:1 to 1:10.

[0031] Optionally, the mass hourly space velocity (WHSV) of methyl alkoxyacetate and / or methoxyacetic acid is independently selected from 0.1 h⁻¹. -1 0.3h -1 1h -1 2h -1 3h -1 4h -1 and 5h -1 Any value in the range or any value between the two.

[0032] Optionally, the molar ratio of methyl alkoxyacetate and / or methoxyacetic acid and lower alcohol is independently selected from any value or a range between 1:20, 1:15, 1:10, 1:8, 1:4, 1:2, 1:1, 2:1, 4:1, 6:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1 and 20:1.

[0033] Optionally, the reaction temperature is 100℃~250℃; the reaction pressure is 0.1MPa~10MPa.

[0034] Optionally, the reaction temperature is 150℃~200℃; the reaction pressure is 0.1MPa~0.3MPa.

[0035] Optionally, the reaction temperature is independently selected from any value or a range between 100°C, 125°C, 150°C, 175°C, 200°C, 225°C, and 250°C.

[0036] Optionally, the reaction pressure is independently selected from any value or a range between 0.1 MPa, 0.3 MPa, 0.5 MPa, 1 MPa, 4 MPa, 6 MPa, 8 MPa and 10 MPa.

[0037] Optionally, the raw material mixture further includes a carrier gas; the carrier gas includes at least one of dimethyl ether, methyl ethyl ether, hydrogen, nitrogen, and argon.

[0038] The flow rate of the carrier gas is 0–40 mL / min.

[0039] Optionally, the flow rate of the carrier gas is independently selected from any value or a range between any two of 0 mL / min, 5 mL / min, 10 mL / min, 15 mL / min, 20 mL / min, 25 mL / min, 30 mL / min, 35 mL / min, and 40 mL / min.

[0040] Optionally, the reactor is selected from at least one of a fixed-bed reactor, a fluidized-bed reactor, and a moving-bed reactor.

[0041] Those skilled in the art can select a suitable reactor based on actual production needs. Preferably, the reactor is a fixed-bed reactor.

[0042] The beneficial effects that this application can produce include:

[0043] 1) The method for producing methyl glycolate provided in this application uses a molecular sieve catalyst, which has a long lifespan and high alcoholysis efficiency. The alcoholysis reaction can occur on a solid catalyst to directly produce methyl glycolate, and separation is simple. The process is simple, the catalyst is readily available and inexpensive, and it has significant prospects for industrial application.

[0044] 2) The method for producing methyl glycolate provided in this application can be carried out under normal pressure and anhydrous conditions, which greatly saves separation energy consumption.

[0045] 3) The method for producing methyl glycolate provided in this application, using methyl methoxyacetate and methanol as raw materials, can achieve a three-step combined process: condensation of methanol with formaldehyde to produce methylal, carbonylation of methylal to produce methyl methoxyacetate, and alcoholysis of methyl methoxyacetate to produce methyl glycolate. Furthermore, the byproduct dimethyl ether can be used in coal-based ethanol processes, efficiently converting coal into oxygen-containing compounds. This achieves efficient and clean utilization of coal resources and is of great significance for promoting the sustainable development of the coal chemical industry. Detailed Implementation

[0046] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0047] Unless otherwise specified, the raw materials and catalysts used in the embodiments of this application were all purchased commercially.

[0048] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0049] The analysis methods and conversion rate and selectivity calculations in the examples are as follows:

[0050] Products other than glycolic acid and unreacted reactants were analyzed using an Agilent 7890B gas chromatograph. Its FID detector was connected to an HP-FFAP capillary column, and its TCD detector was connected to a Porapak Q packed column. Glycolic acid was analyzed using a liquid chromatograph with a C10 column. 18 The column is equipped with an ultraviolet detector.

[0051] In the examples, the conversion rate of methyl methoxyacetate was calculated using the internal standard method, and the product selectivity was calculated using the normalization method.

[0052] Methyl methoxyacetate conversion rate = [(number of carbon moles of methyl methoxyacetate in the feedstock) - (number of carbon moles of methyl methoxyacetate in the product)] ÷ (number of carbon moles of methyl methoxyacetate in the feedstock) × 100%

[0053] Product selectivity = (Amount of the product ÷ Amount of all carbon-containing products) × 100%

[0054] Example 1

[0055] Commercial hydrogen-form ZSM-5 molecular sieve (silicon-to-aluminum ratio 35) was crushed and sieved into 0.4–0.8 mm particles. 2 g of the particles were placed in a stainless steel reaction tube with an inner diameter of 8 mm and activated with nitrogen at 450 °C for 2 h using 40 mL / min. The reaction conditions were as follows: reaction temperature 150 °C, reaction pressure 0.1 MPa, nitrogen as carrier gas at a flow rate of 30 mL / min, a molar ratio of methyl methoxyacetate to methanol in the feedstock of 1:2, and a mass hourly space velocity (HHSV) of methyl methoxyacetate of 1.0 h⁻¹. -1 After 24 hours of reaction, the products were analyzed by gas chromatography and liquid chromatography. The reaction results based on the number of carbon atoms are shown in Table 1.

[0056] Examples 2-6

[0057] The catalyst, reaction conditions, and reaction results are shown in Table 1. Other procedures are the same as in Example 1.

[0058] Table 1. Results of catalytic reactions in Examples 1-6

[0059]

[0060] As shown in Table 1, the hydrogen-type molecular sieve catalyst exhibits excellent catalytic performance in the alcoholysis of methyl methoxyacetate to methyl glycolate, with high conversion rate of methyl methoxyacetate and high selectivity of methyl glycolate.

[0061] Example 7

[0062] The reaction was carried out at commercial hydrogen-type ZSM-5 molecular sieve (silicon-aluminum molecular ratio of 35) at temperatures ranging from 100 to 250°C. Other reaction conditions were the same as in Example 1. The reaction results are shown in Table 2.

[0063] Table 2. Reaction results at different reaction temperatures

[0064] Reactor temperature / °C 100 150 200 250 methyl methoxyacetate conversion rate / % 15.1 50.5 80.2 88.1 Methyl glycolate selectivity / % 44.8 40.3 10.5 2.7 Dimethyl ether selectivity / % 40.5 43.7 71.4 79.0 Methoxyacetic acid selectivity / % 7.9 10.8 17.9 18.3 Glycolic acid selectivity / % 4.1 3.1 0.2 0 other / % 2.7 2.1 0 0

[0065] Example 8

[0066] The reaction was carried out using commercial hydrogen-type ZSM-5 molecular sieve (silicon-aluminum molecular ratio of 35), with reaction pressures ranging from 0.1 to 10.0 MPa. Other reaction conditions were the same as in Example 1, and the reaction results are shown in Table 3.

[0067] Table 3. Reaction results under different reaction pressures

[0068] Reaction pressure / MPa 0.1 0.2 0.3 10 methyl methoxyacetate conversion rate / % 50.5 51.3 53.9 88.9 Methyl glycolate selectivity / % 40.3 41.3 43.8 44.7 Dimethyl ether selectivity / % 43.7 44.7 44.3 44.1 Methoxyacetic acid selectivity / % 10.8 10.1 9.8 10.1 Glycolic acid selectivity / % 3.1 3.1 2.1 1.1 other / % 2.1 0.7 0 0

[0069] Example 9

[0070] Selected from commercial hydrogen-form ZSM-5 molecular sieve (silicon-to-aluminum ratio 35), methyl methoxyacetate has a mass hourly space velocity (WHSV) of 0.1 h⁻¹. -1 ~5.0h -1 Other reaction conditions were the same as in Example 1, and the reaction results are shown in Table 4.

[0071] Table 4. Reaction results at different mass space velocities.

[0072]

[0073] Example 10

[0074] The reaction mixture was selected from commercial hydrogen-form ZSM-5 molecular sieve (silicon-aluminum molecular ratio of 35), and the molar ratio of methyl methoxyacetate to methanol was 1:20 to 20:1. Other reaction conditions were the same as in Example 1. The reaction results are shown in Table 5.

[0075] Table 5. Reaction results at different molar ratios of methyl methoxyacetate to methanol.

[0076]

[0077] Examples 11-15

[0078] The catalyst in Example 1 was replaced with commercially available Amberlyst 15, γ-alumina, Amberlyst A26, Mg-Al hydrotalcite and hydroxyapatite, and other conditions and operations were the same. The reaction results are shown in Table 6.

[0079] Table 6 Results of catalytic reactions in Examples 11-15

[0080]

[0081] It can be seen that the above-mentioned solid acid catalysts and solid base catalysts can also catalyze the alcoholysis of methyl methoxyacetate to produce methyl glycolate.

[0082] Examples 16-19

[0083] The commercial hydrogen-form ZSM-5 molecular sieve (silicon-aluminum molecular ratio of 35) from Example 1 was extruded using alumina / silica / kaolin / magnesium oxide. The preparation method involved mixing the hydrogen-form ZSM-5 molecular sieve, matrix, and guar gum powder in a ratio of 70:24:1, adding 10% nitric acid, kneading, and then extruding the mixture. After calcination at 550°C, a solid acid catalyst containing the matrix (20 wt%) was obtained. Other conditions and operations remained unchanged. The reaction results are shown in Table 7.

[0084] Table 7 Results of catalytic reactions in Examples 16-19

[0085]

[0086] As can be seen from Table 7, the activity of acidic molecular sieve catalysts is basically maintained after being formed using alumina, silica, kaolin, or magnesium oxide.

[0087] Examples 20-23

[0088] The methyl methoxyacetate in Example 1 was replaced with other methyl alkoxyacetate and methoxyacetic acid, respectively, while other conditions and operations remained unchanged. The reaction results are shown in Table 8.

[0089] Example 24

[0090] The methanol in Example 1 was replaced with ethanol, while other conditions and operations remained unchanged. The reaction results are shown in Table 8.

[0091] Table 8 Results of catalytic reactions in Examples 20-24

[0092]

[0093] Examples 25-26

[0094] The carrier gas in Example 1 was replaced with hydrogen and dimethyl ether, respectively, while other conditions and operations remained unchanged. The reaction results are shown in Table 9.

[0095] Table 9 Results of catalytic reactions in Examples 25-26

[0096] Example carrier gas methyl methoxyacetate conversion rate / % Methyl glycolate selectivity / % 25 hydrogen 50.2 39.8 26 dimethyl ether 40.3 38.7

[0097] Example 27

[0098] Commercially available hydrogen-form ZSM-5 molecular sieve (silicon-to-aluminum molecular ratio 35) was crushed and sieved into 0.4–0.8 mm particles. 2 g of the sieve was placed in a stainless steel reaction tube with an inner diameter of 8 mm and activated with nitrogen at 40 mL / min at 450 °C for 2 h. The reaction conditions were as follows: reaction temperature 150 °C, reaction pressure 0.1 MPa, nitrogen as carrier gas at a flow rate of 30 mL / min, a molar ratio of methyl methoxyacetate to methanol in the feedstock of 1:2, and a mass hourly space velocity (HHSV) of methyl methoxyacetate of 1.0 h⁻¹. -1 The products at different time points were analyzed by gas chromatography and liquid chromatography. The reaction results based on the carbon number are shown in Table 10.

[0099] Table 10 Results of the catalytic reaction in Example 27

[0100]

[0101] As can be seen from Table 10, the hydrogen-type molecular sieve catalyst has good stability in the alcoholysis of methyl methoxyacetate to methyl glycolate, which meets the requirements for industrial use.

[0102] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for producing methyl glycolate, characterized in that, The production method includes: A mixture of raw materials containing methyl alkoxyacetate and / or methoxyacetic acid and lower alcohols is reacted with a catalyst in a reactor to obtain methyl glycolate. The lower alcohol is selected from methanol and / or ethanol.

2. The production method according to claim 1, characterized in that, The catalyst is selected from at least one of solid acid catalysts and solid base catalysts.

3. The production method according to claim 1, characterized in that, The solid acid catalyst is selected from at least one of acidic zeolite molecular sieve catalysts, acidic resin catalysts, and acidic alumina catalysts. The solid base catalyst is selected from at least one of hydrotalcite, anion exchange resin, and hydroxyapatite.

4. The production method according to claim 3, characterized in that, The acidic zeolite molecular sieve catalyst includes an acidic zeolite molecular sieve. The acidic zeolite molecular sieve is selected from at least one of the following: acidic zeolite molecular sieves with MFI structure, acidic zeolite molecular sieves with MEL structure, acidic zeolite molecular sieves with MTT structure, acidic zeolite molecular sieves with TON structure, acidic zeolite molecular sieves with MWW structure, acidic zeolite molecular sieves with FER structure, acidic zeolite molecular sieves with MOR structure, acidic zeolite molecular sieves with EUO structure, acidic zeolite molecular sieves with BEA structure, and acidic zeolite molecular sieves with FAU structure. Preferably, the acidic zeolite molecular sieve is selected from at least one of the following: hydrogen-form ZSM-5 molecular sieve, hydrogen-form ZSM-11 molecular sieve, hydrogen-form ZSM-23 molecular sieve, hydrogen-form ZSM-22 molecular sieve, hydrogen-form MCM-22 molecular sieve, hydrogen-form ZSM-35 molecular sieve, hydrogen-form MOR molecular sieve, hydrogen-form EU-1 molecular sieve, hydrogen-form Beta molecular sieve, and hydrogen-form Y molecular sieve. Preferably, the silicon-to-aluminum molecular ratio of the acidic molecular sieve is 5 to 500.

5. The production method according to claim 4, characterized in that, The acidic zeolite molecular sieve catalyst also includes a matrix; The matrix is ​​selected from at least one of alumina, silicon dioxide, kaolin, and magnesium oxide; The acidic zeolite molecular sieve has a mass content of 10-100% in the catalyst.

6. The production method according to claim 3, characterized in that, The acidic resin catalyst is selected from at least one of Amberlyst-15 and Nafion; The acidic alumina catalyst is selected from γ-alumina; The hydrotalcite is selected from Mg-Al hydrotalcite; The anion exchange resin is selected from Amberlyst A26.

7. The production method according to claim 1, characterized in that, The methyl alkoxyacetate is selected from at least one of methyl methoxyacetate, methyl ethoxyacetate, methyl propoxyacetate, and methyl butoxyacetate.

8. The production method according to claim 1, characterized in that, The mass hourly space velocity (HSV) of methyl alkoxyacetate and / or methoxyacetic acid is 0.1 h⁻¹. -1 ~5.0h -1 The molar ratio of methyl alkoxyacetate and / or methoxyacetic acid to lower alcohols is 1:20 to 20:

1. Preferably, the mass hourly space velocity (WHSV) of methyl alkoxyacetate and / or methoxyacetic acid is 0.1 h⁻¹. -1 ~3.0h -1 The molar ratio of methyl alkoxyacetate and / or methoxyacetic acid and lower alcohols is 1:1 to 1:

10.

9. The production method according to claim 1, characterized in that, The reaction temperature is 100℃~250℃; the reaction pressure is 0.1MPa~10MPa; Preferably, the reaction temperature is 150℃~200℃; the reaction pressure is 0.1MPa~0.3MPa.

10. The production method according to claim 1, characterized in that, The raw material mixture also contains a carrier gas; the carrier gas includes at least one of dimethyl ether, methyl ethyl ether, hydrogen, nitrogen, and argon. The flow rate of the carrier gas is 0–40 mL / min; Preferably, the reactor is selected from at least one of a fixed-bed reactor, a fluidized-bed reactor, and a moving-bed reactor.

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