A process for the synthesis of glyoxylic acid from methyl glycolate

Abstract

This invention proposes a method for synthesizing glyoxylic acid from methyl glycolate. Using methyl glycolate and oxygen / water as raw materials, glyoxylic acid is produced in a one-step process. This invention employs a novel catalyst based on ZSM-5 molecular sieve, modified with transition metals and organic bases, and finally extruded into strips. This catalyst can catalyze both oxidation and hydrolysis. This route is characterized by its simplicity, high reactivity, and high catalytic selectivity, making it a green route for glyoxylic acid synthesis.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a method for synthesizing glyoxylic acid from methyl glycolate. Background Technology

[0002] Glyoxylic acid, abbreviated as GLA, has the chemical formula C2H2O3 and a molecular weight of 74.04. The pure form is a white crystalline solid, and industrially it is often sold as a 50% aqueous solution. One glyoxylic acid molecule contains one molecule of aldehyde and one molecule of carboxyl, making it the simplest aldehyde acid. Therefore, it possesses the properties of both aldehydes and acids, and can undergo simultaneous aldehyde and acid reactions, sometimes even cyclization reactions. Glyoxylic acid is an important chemical intermediate widely used in the synthesis of mandelic acid, vanillin, allantoin, penicillin, amoxicillin, and p-hydroxyphenylacetamide, among other products, making it a promising fine chemical.

[0003] Glyoxylic acid production methods can be categorized into chemical and electrolytic methods based on their synthesis approach. Chemical methods include ethylene / aldehyde oxidation, glyoxal nitric acid oxidation, maleic anhydride ozonation, and hydroxycellulose hydrolysis. Electrolytic methods include oxalic acid electrolysis and glyoxal anodic oxidation. Currently, the main industrialized methods are glyoxal nitric acid oxidation and maleic anhydride ozonation. Glyoxal nitric acid oxidation is the most mainstream process due to its low cost, but it generates nitrogen-containing wastewater and exhaust gas, posing a significant environmental burden, and the product purity is not high. While maleic anhydride ozonation can yield high-purity glyoxylic acid crystals, the ozonation equipment is energy-intensive, poses significant safety risks, and has high production costs, limiting its large-scale application.

[0004] In recent years, the process of producing dimethyl oxalate (DMC) from syngas has seen significant development, with an increasing number of DMC producers shifting to this route. During the DMC production process from syngas, methyl glycolate is generated as a byproduct. With the continuous increase in plant capacity, the yield of this byproduct is also considerable. Therefore, the application of this byproduct methyl glycolate has attracted widespread attention. Currently, the most promising utilization method is the oxidation and hydrolysis of methyl glycolate to produce glyoxylic acid.

[0005] Glycol esters are oxidized or dehydrogenated to glyoxylate under the action of a catalyst. Glyoxylate can be further hydrolyzed to obtain glyoxylic acid. Current research mainly focuses on the first step. US Patent 4340748 discloses a method for generating glyoxylate from glycolate, with a preferred reaction temperature of 200–400°C. The method involves gas-phase catalytic oxidation of glycolate with oxygen-containing gas to obtain glyoxylate. However, the catalyst used in this method has a low yield of glyoxylate, below 90%. Chinese Patent CN107445830A uses molybdenum-vanadium as the active component of the catalyst, silicon oxide, alumina, and zirconium oxide as supports, and copper, palladium, manganese, and nickel as co-catalysts to efficiently catalytically oxidize glycolate to prepare glyoxylate. To avoid over-oxidation of methyl glycolate, nitrogen oxides are added to the oxygen-containing gas. However, this method involves cumbersome catalyst preparation, and the nitrogen oxide tail gas is difficult to treat, thus its economic value needs improvement. Summary of the Invention

[0006] To address the problems of existing technologies, this invention provides a method for synthesizing glyoxylic acid from methyl glycolate, which can obtain the product in one step. The preparation method is simple and saves on reaction and product purification processes.

[0007] To achieve the above objectives, the present invention provides a method for synthesizing glyoxylic acid from methyl glycolate. Glycolic acid is produced by reacting glycolate, oxygen or air, and water in the presence of a catalyst. The catalyst is a solid acid catalyst supported on a metal, wherein the metal includes manganese, lanthanum, and copper. Preferably, the mass ratio of manganese, lanthanum, and copper is 1:(0.8-1.5):(0.2-0.7).

[0008] The total metal loading accounts for 0.1-1 wt% of the total catalyst weight.

[0009] Preferably, the catalyst uses a molecular sieve as a support.

[0010] Preferably, the catalyst is prepared by the following method:

[0011] (1) The NH4ZSM-5 molecular sieve was calcined at high temperature to obtain HZSM-5 without template agent;

[0012] (2) HZSM-5 was impregnated and modified with a salt solution of manganese, lanthanum and copper, and then dried;

[0013] (3) The above-impregnated molecular sieve is further modified by adding it into an organic alkali solution, and then calcined at high temperature.

[0014] (4) The obtained catalyst is mixed with binder, extruded, and calcined to obtain a shaped catalyst.

[0015] In step (1) of the present invention, the Si / Al ratio of NH4ZSM-5 molecular sieve is 20-60, and the preferred Si / Al ratio is 30-40.

[0016] In step (1) of the present invention, the specific surface area (BET) of NH4ZSM-5 molecular sieve is 100-600 m² / g, and the preferred BET is 300-500 m² / g.

[0017] In step (1) of this invention, the calcination temperature is 400-800℃, preferably 500-600℃. The calcination time is 1-10h, preferably 3-6h.

[0018] In step (2) of this invention, the salts of manganese, lanthanum, and copper can be selected from sulfates, nitrates, hydrochlorides, etc., such as copper sulfate, copper nitrate, manganese sulfate, manganese nitrate, lanthanum sulfate, and lanthanum nitrate.

[0019] In the present invention (2), the mass ratio of manganese, lanthanum and copper elements in the metal salt of manganese, lanthanum and copper is 1:(0.8-1.5):(0.2-0.7), and the three have a synergistic effect.

[0020] In step (2) of the present invention, the total mass concentration of the metal salt solution is 1-30%wt, preferably 5-10%wt.

[0021] In step (2) of the present invention, HZSM-5 is placed in a transition metal salt solution and stirred, wherein the mass ratio of HZSM-5 to the metal salt is 1:(2-20), and the preferred mass ratio is 1:(5-15).

[0022] In step (2) of this invention, the stirring temperature is room temperature and the stirring time is 3-8 hours.

[0023] In step (2) of the present invention, the drying temperature is 100-150℃ and the drying time is 6-12h.

[0024] In step (3) of this invention, the impregnated molecular sieve is added to an organic alkaline solution for impregnation modification. The impregnation temperature is 50℃-100℃, and the impregnation time is 5-15h. The preferred impregnation temperature is 60-80℃, and the preferred impregnation time is 6-9h.

[0025] In step (3) of the present invention, the organic base may be one or more of triethylamine, tripropylamine, dimethylaminopyrrole, pyridine, tetrapropylammonium hydroxide, tetramethylammonium hydroxide, etc.

[0026] In step (3) of the present invention, an organic base solution is prepared, and the solvent selected is water, ethanol, diethyl ether, acetone, etc. The mass concentration of the organic base is 0.1%-5%, preferably 0.5%-2%.

[0027] In step (3) of the present invention, the impregnated molecular sieve is filtered, dried and then calcined at a temperature of 400-700℃, preferably 500-600℃; the calcination time is 2-12h, preferably 5-8h.

[0028] In step (4) of the present invention, the binder is one or more of silica sol, alumina sol, sodium carboxymethyl cellulose, kaolin, etc.

[0029] In step (4) of the present invention, the mass ratio of catalyst to binder is (2-10):1, preferably (3-6):1.

[0030] In step (4) of the present invention, the particle size of the catalyst after extrusion is controlled at 1-10 mm, preferably 2-5 mm.

[0031] In step (4) of the present invention, the strength of the catalyst after extrusion is controlled at 5-30N, preferably 10-20N.

[0032] In step (4) of the present invention, the calcination temperature is 4-8h and the calcination time is 4-8h.

[0033] The BET of the prepared catalyst was 300-400 m² / g.

[0034] In some specific embodiments of the present invention, the method for preparing glycolic acid is as follows: a shaped catalyst is loaded into a fixed bed, and methyl glycolate, oxygen or air, and water are simultaneously introduced into the fixed bed to carry out the reaction. The reaction temperature is 150-200°C, the reaction pressure is 0.1-0.8 MPa, and the catalyst mass hourly space velocity (based on methyl glycolate) is 0.1-0.3 h⁻¹. -1 .

[0035] The beneficial effects of this invention are as follows: ZSM-5 is a widely used zeolite molecular sieve with a typical MFI framework, possessing a large specific surface area and strong catalytic activity. Impregnating ZSM-5 with transition metal salts can improve the dispersion of transition metals on the molecular sieve, thereby enhancing the catalytic activity for the oxidation of methyl glycolate to methyl glyoxylate. This invention uses a mixture of three metal salts for loading. All three metal salts possess certain catalytic activity and exhibit strong synergistic effects at specific ratios. Manganese, lanthanum, and copper are all transition metals with abundant active electrons in their outermost shells. These active electrons can combine with the outer electrons of elements such as oxygen, sulfur, and nitrogen to form covalent bonds, thus forming new multi-element covalent compounds, which can improve product selectivity. Furthermore, ZSM-5 possesses strong acidic sites, which can be used to catalyze hydrolysis reactions, enabling the hydrolysis of the generated methyl glyoxylate to glyoxylic acid.

[0036] However, ZSM-5 has strong acidic sites, which are prone to other side reactions. By using organic bases to modify the catalyst, the organic bases can neutralize some of the more active acidic sites, effectively balancing the distribution of acidic sites. The density and strength of strong acidic sites are reduced accordingly, while the weak acidic sites remain unchanged, thus reducing the occurrence of side reactions.

[0037] Finally, the modified ZSM-5 was mixed with a binder to prepare an extruded catalyst, which was then used in a fixed-bed reactor. Only the raw material and oxygen source need to be introduced into the fixed bed to obtain an aqueous solution of glyoxylic acid in one step. Currently, most commercially available glyoxylic acid is a 50% aqueous solution, so it can be purified slightly to meet the standards for sale, which greatly simplifies the process. Detailed implementation method:

[0038] The following embodiments will further illustrate the method provided by the present invention, but the present invention is not limited to the listed embodiments, and should also include any other known modifications within the scope of the claims of the present invention.

[0039] Sources of some raw materials in the examples:

[0040] NH4ZSM-5: Dalian Zhuoran Environmental Protection Technology Co., Ltd.

[0041] Manganese sulfate, manganese nitrate, copper sulfate, copper nitrate, lanthanum nitrate: Beijing Innocare Technology Co., Ltd.

[0042] Triethylamine: Sinopharm Group Co., Ltd.

[0043] Example 1

[0044] 30g of NH4ZSM-5 molecular sieve (Si / Al = 30, BET = 550 m² / g) was placed in a muffle furnace and calcined at 550℃ for 4 hours to obtain H-type HZSM-5 without template agent. 20g of HZSM-5 was added to 1200g of a metal salt solution (metal salt concentration: 10%), the metal salt being a mixture of manganese sulfate, lanthanum nitrate, and copper sulfate, with a manganese, lanthanum, and copper mass ratio of 1:0.9:0.6. After stirring for 5 hours, the mixture was filtered and dried at 120℃ for 8 hours. 20g of the dried catalyst was added to an ethanol solution of triethylamine (0.5wt%), heated to 80℃, and impregnated at this temperature for 7 hours. After filtration, washing, and drying, the catalyst was calcined at 500℃ for 8 hours. 20g of the calcined catalyst, 5g of silica sol, and a small amount of water were mixed and stirred into a slurry. This slurry was then extruded using a screw extruder, dried, and calcined before being granulated into 3mm long pieces. The catalyst has a strength of 12 N and a measured BET of 320 m² / g. Inductively coupled plasma atomic emission spectrometry (ICP) was used to determine the metal ion content, yielding a loading of 0.5 wt%.

[0045] The 20g of shaped catalyst was loaded into a fixed bed, and a mixture of methyl glycolate, oxygen, and water was simultaneously introduced into the fixed bed. The reaction temperature was 150℃, the reaction pressure was 0.5MPa, and the catalyst mass hourly space velocity (based on methyl glycolate) was 0.15h⁻¹. -1 The reaction solution was analyzed by liquid chromatography, and the yield of glyoxylic acid was found to be 95.6%.

[0046] Example 2

[0047] 30g of NH4ZSM-5 molecular sieve (Si / Al = 35, BET = 450 m² / g) was placed in a muffle furnace and calcined at 450℃ for 5h to obtain H-type HZSM-5 without template agent. 20g of HZSM-5 was added to 2000g of a metal salt solution (5% wt), the metal salt being a mixture of manganese sulfate, lanthanum nitrate, and copper sulfate, with a mass ratio of manganese, lanthanum, and copper of 1:1.1:0.4. After stirring for 5h, the mixture was filtered and dried at 110℃ for 6h. 20g of the dried catalyst was added to an ethanol solution of tetrapropylammonium hydroxide (1 wt%), heated to 70℃, and impregnated at this temperature for 6h. After filtration, washing, and drying, the catalyst was calcined at 500℃ for 6h. 20g of the calcined catalyst, 5g of silica sol, and a small amount of water were mixed and stirred into a slurry. This slurry was then extruded using a screw extruder, dried, and calcined before being granulated into 3mm long pieces. The catalyst has a strength of 11.5 N, a measured BET of 330 m² / g, and a metal loading of 0.4 wt%.

[0048] The 20g of shaped catalyst was loaded into a fixed bed, and a mixture of methyl glycolate, oxygen, and water was simultaneously introduced into the fixed bed. The reaction temperature was 150℃, the reaction pressure was 0.5MPa, and the catalyst mass hourly space velocity (based on methyl glycolate) was 0.15h⁻¹. -1 The reaction solution was analyzed by liquid chromatography, and the yield of glyoxylic acid was found to be 96.4%.

[0049] Example 3

[0050] 30g of NH4ZSM-5 molecular sieve (Si / Al = 50, BET = 550 m² / g) was placed in a muffle furnace and calcined at 700℃ for 2.5h to obtain H-type HZSM-5 without template agent. 20g of HZSM-5 was added to 800g of a metal salt solution (25% wt), the metal salt being a mixture of manganese sulfate, lanthanum nitrate, and copper sulfate, with a mass ratio of manganese, lanthanum, and copper of 1:1.3:0.4. After stirring for 5h, the mixture was filtered and dried at 140℃ for 6h. 20g of the dried catalyst was added to an ethanol solution of tripropylamine (4 wt%), heated to 70℃, and impregnated at this temperature for 8h. After filtration, washing, and drying, the catalyst was calcined at 600℃ for 3h. 20g of the calcined catalyst, 4g of silica sol, and a small amount of water were mixed and stirred into a slurry. This slurry was then extruded using a screw extruder, dried, and calcined before being granulated into 3mm long shaped catalyst particles. The catalyst has a strength of 10.8 N, a measured BET of 390 m² / g, and a metal loading of 0.8 wt%.

[0051] The 20g of shaped catalyst was loaded into a fixed bed, and a mixture of methyl glycolate, oxygen, and water was simultaneously introduced into the fixed bed. The reaction temperature was 150℃, the reaction pressure was 0.5MPa, and the catalyst mass hourly space velocity (based on methyl glycolate) was 0.15h⁻¹. -1 The reaction solution was analyzed by liquid chromatography, and the yield of glyoxylic acid was found to be 95.7%.

[0052] Comparative Example 1

[0053] 30g of NH4ZSM-5 molecular sieve (Si / Al = 40, BET = 500 m² / g) was placed in a muffle furnace and calcined at 600℃ for 3 hours to obtain H-type HZSM-5 without template agent. 20g of HZSM-5 was added to 1800g of copper sulfate solution (15% wt), stirred for 5 hours, filtered, and dried at 140℃ for 8 hours. 20g of the dried catalyst was added to a triethylamine ethanol solution (2 wt%), heated to 60℃, and impregnated at this temperature for 8 hours. After filtration, washing, and drying, it was calcined at 500℃ for 2 hours. 20g of the calcined catalyst, 4g of silica sol, and a small amount of water were mixed and stirred into a slurry. This slurry was then extruded using a screw extruder, dried, and calcined. The catalyst was then granulated into 3mm long shaped catalyst particles. The catalyst strength was 11 N, the BET was measured to be 350 m² / g, and the metal loading was 0.5 wt%.

[0054] The 20g of shaped catalyst was loaded into a fixed bed, and a mixture of methyl glycolate, oxygen, and water was simultaneously introduced into the fixed bed. The reaction temperature was 150℃, the reaction pressure was 0.5MPa, and the catalyst mass hourly space velocity (based on methyl glycolate) was 0.15h⁻¹. -1 The reaction solution was analyzed by liquid chromatography, and the yield of glyoxylic acid was found to be 82.4%.

Claims

1. A method for synthesizing glyoxylic acid from methyl glycolate, characterized in that, Glyoxylic acid is produced by the reaction of glycolate, oxygen or air, and water in the presence of a catalyst; the reaction temperature is 150-200℃. The catalyst is a solid acid catalyst supported on a metal, wherein the metal is manganese, lanthanum, or copper, and the mass ratio of the manganese, lanthanum, and copper elements is 1:(0.8-1.5):(0.2-0.7). The total metal loading accounts for 0.1-1 wt% of the total catalyst weight; The catalyst is prepared as follows: (1) The NH4ZSM-5 molecular sieve was calcined at high temperature to obtain HZSM-5 without template agent; (2) HZSM-5 was impregnated and modified with a salt solution of manganese, lanthanum and copper, and then dried; (3) The above-impregnated molecular sieve is further modified by adding it into an organic alkali solution, and then calcined at high temperature; (4) The obtained catalyst is stirred with a binder, extruded, and calcined to obtain a shaped catalyst; In step (2), HZSM-5 is placed in a transition metal salt solution and stirred, wherein the mass ratio of HZSM-5 to the metal salt is 1:(2-20). In step (3), the organic base is selected from one or more of triethylamine, tripropylamine, dimethylaminopyrrole, pyridine, tetrapropylammonium hydroxide, and tetramethylammonium hydroxide.

2. The method according to claim 1, characterized in that, In step (1), the Si / Al ratio of NH4ZSM-5 molecular sieve is 20-60.

3. The method according to claim 2, characterized in that, In step (1), the Si / Al ratio of NH4ZSM-5 molecular sieve is 30-40.

4. The method according to claim 1, characterized in that, In step (1), the specific surface area of ​​NH4ZSM-5 molecular sieve is 100-600㎡ / g.

5. The method according to claim 4, characterized in that, In step (1), the specific surface area of ​​NH4ZSM-5 molecular sieve is 300-500㎡ / g.

6. The method according to claim 1, characterized in that, In step (1), the roasting temperature is 400-800℃ and the roasting time is 1-10h.

7. The method according to claim 6, characterized in that, In step (1), the roasting temperature is 500-600℃ and the roasting time is 3-6h.

8. The method according to claim 1, characterized in that, In step (2), the total mass concentration of the metal salt solution is 1-30%wt.

9. The method according to claim 8, characterized in that, In step (2), the total mass concentration of the metal salt solution is 5-10%wt.

10. The method according to claim 1, characterized in that, The mass ratio of HZSM-5 to metal salt is 1:(5-15).

11. The method according to claim 1, characterized in that, In step (2), the stirring temperature is room temperature and the stirring time is 3-8 hours.

12. The method according to claim 1, characterized in that, In step (2), the drying temperature is 100-150℃ and the drying time is 6-12h.

13. The method according to claim 1, characterized in that, In step (3), the impregnated molecular sieve is added to an organic alkaline solution for impregnation and modification. The impregnation temperature is 50℃-100℃ and the impregnation time is 5-15h.

14. The method according to claim 13, characterized in that, In step (3), the impregnated molecular sieve is added to an organic alkaline solution for impregnation and modification. The impregnation temperature is 60-80℃ and the impregnation time is 6-9h.

15. The method according to claim 1, characterized in that, In step (3), an organic base solution is prepared, and the mass concentration of the organic base is 0.1%-5%.

16. The method according to claim 15, characterized in that, In step (3), the mass concentration of the organic base is 0.5%-2%.

17. The method according to claim 15, characterized in that, In step (3), the solvents used to prepare the organic base solution are water, ethanol, diethyl ether, and acetone.

18. The method according to claim 1, characterized in that, In step (3), the impregnated molecular sieve is filtered, dried and then calcined at a temperature of 400-700℃ for 2-12 hours.

19. The method according to claim 18, characterized in that, In step (3), the roasting temperature is 500-600℃ and the roasting time is 5-8h.

20. The method according to claim 1, characterized in that, In step (4), the binder is one or more of silica sol, alumina sol, sodium carboxymethyl cellulose, and kaolin.

21. The method according to claim 1, characterized in that, In step (4), the mass ratio of catalyst to binder is (2-10):

1.

22. The method according to claim 21, characterized in that, In step (4), the mass ratio of catalyst to binder is (3-6):

1.

23. The method according to claim 1, characterized in that, In step (4), the particle size of the catalyst after extrusion is controlled to be 1-10 mm.

24. The method according to claim 23, characterized in that, In step (4), the particle size of the catalyst after extrusion is controlled at 2-5 mm.

25. The method according to claim 1, characterized in that, In step (4), the strength of the catalyst after extrusion is controlled at 5-30N.

26. The method according to claim 25, characterized in that, In step (4), the strength of the catalyst after extrusion is controlled at 10-20N.

27. The method according to claim 1, characterized in that, In step (4), the roasting time is 4-8 hours.

28. The method according to claim 1, characterized in that, The method for preparing glycolic acid is as follows: a shaped catalyst is loaded into a fixed bed, and methyl glycolate, oxygen or air and water are simultaneously introduced into the fixed bed to carry out the reaction. The reaction pressure was 0.1-0.8 MPa, and the catalyst mass hourly space velocity (HHSV) was 0.1-0.3 h⁻¹, based on methyl glycolate. -1 .