A heteropolyacid catalyst and its preparation and application

Abstract

This invention relates to a heteropolyacid catalyst for the condensation of formaldehyde and methyl formate to methyl glycolate, the preparation method of which includes the following steps: (1) loading the active component and (2) overflow hydrogen reduction. This invention uses common silica as a support and employs a co-impregnation method to load the active component to prepare the catalyst, under mild conditions and with a stable and controllable process. By doping with an appropriate amount of metal, overflow hydrogen is induced to reduce some coordinating atoms in the heteropolyacid as basic sites, which synergistically interact with the strongly acidic sites of the heteropolyacid to promote the cross-condensation of formaldehyde and methyl formate, thereby improving the reaction activity and selectivity. The prepared catalyst has advantages such as low reaction temperature, high activity, and good selectivity.

Description

Technical Field

[0001] This invention relates to a catalytic method for the condensation of formaldehyde and methyl formate to produce methyl glycolate, specifically a method for the catalytic condensation of formaldehyde and methyl formate on a doped supported heteropolyacid catalyst. Background Technology

[0002] Methyl glycolate is an important chemical raw material. Through amination, oxidation, hydrogenation, carbonylation, and polymerization, it can be used to produce glycine, methyl glyoxylate, ethylene glycol, methyl malonate, and polyglycolic acid (PEG). PEG possesses excellent biocompatibility and biodegradability, and has broad application and industrialization prospects in medical, oil and gas extraction, and packaging fields. The existing methyl glycolate production route is the chloroacetic acid hydrolysis esterification method. This route has low product yield, heavy pollution, and severe equipment corrosion, making large-scale industrial production difficult. Formaldehyde and methyl formate have large production capacities and are readily available, giving them a resource advantage. Using formaldehyde and methyl formate as raw materials, designing efficient catalysts, and preparing methyl glycolate through cross-condensation, will extend the downstream application of methanol to key links in biodegradable materials such as PEG. This will not only meet the country's growing demand for biodegradable materials but also be an important means to improve the technological economy and market resilience of coal chemical engineering.

[0003] The development of efficient catalysts is crucial for the condensation of formaldehyde and methyl formate to methyl glycolate. Catalysts used for the condensation of formaldehyde and methyl formate mainly include liquid strong acid catalysts and solid acid catalysts. Hoechst AG (DE2652072) reported a sulfuric acid or organic sulfonic acid catalytic system in which formaldehyde and methyl formate react to produce methyl glycolate at 90°C and atmospheric pressure, with yields of 24%-69%. The Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, disclosed a catalytic system combining a metal carbonyl sulfate compound, aminosulfonic acid, p-toluenesulfonic acid, and a metal halide, with mild process conditions and high product yields (ZL97107692.8, ZL2005100211146.5, and ZL200610022389.5). However, this catalytic system is prone to corroding equipment, and waste liquid treatment is difficult. Mitsubishi Chemical of Japan used Diaion (cation exchange resin) as a catalyst, achieving a methyl glycolate yield of 56% at 110℃ and 6MPa (Japanese Patent Publication No. 57-46934). The Shanxi Coal Research Institute of the Chinese Academy of Sciences disclosed a catalytic system with an alumina and silica composite solid acid as the active component and a Group VIII non-precious metal oxide as the active agent. This catalytic system features high feed conversion rate, high product selectivity, and low corrosivity (ZL201210486084.5). This method solves the equipment corrosion problem, but requires high reaction pressure, and cost and safety issues are prominent.

[0004] This invention develops a novel method for preparing a condensation catalyst for formaldehyde and methyl formate. An active metal is introduced while supporting a heteropolyacid active component. By reducing some of the coordinating atoms of the heteropolyacid with overflow hydrogen, making it basic, the metal synergistically activates methyl formate and formaldehyde with the strong acid center of the heteropolyacid, promoting their cross-condensation to prepare methyl glycolate, thereby improving the catalyst's reactivity. Summary of the Invention

[0005] The problem to be solved by the present invention is to provide a method for preparing a formaldehyde-methyl formate condensation catalyst that is highly efficient, has mild reaction conditions, a controllable preparation process, and simple steps. The prepared catalyst has the advantages of mild reaction conditions, high activity, and good selectivity, and can be applied to condensation reactions catalyzed by acid-base synergy, and has broad application prospects.

[0006] The technical solution is as follows:

[0007] The method for preparing the heteropolyacid catalyst for the condensation of formaldehyde and methyl formate to methyl glycolate according to the present invention includes the following steps:

[0008] (1) Loading metal additives and active components: The raw material salt is prepared into a solution and co-impregnated onto the silica support. After aging, drying and calcination, the catalyst precursor is obtained.

[0009] (2) Overflow hydrogen reduction: The catalyst precursor obtained in step 1 is placed in a reducing atmosphere and treated at a certain temperature to obtain a formaldehyde and methyl formate condensation catalyst. This step is the key step of the present invention. Its function is to obtain a suitable amount of metal by loading it, and generate overflow hydrogen in a reducing atmosphere to reduce some of the coordinating atoms in the heteropolyacid as base centers. These atoms, together with the acid centers of the heteropolyacid, activate methyl formate and formaldehyde, promoting their cross-condensation to prepare methyl glycolate, thereby improving the activity and selectivity of the catalyst.

[0010] Preferably, in step (1), the carrier is silicon dioxide with the following properties: specific surface area 350±100m². 2 / g, pore volume 0.8±0.4mL / g, average pore size 12±6nm.

[0011] Preferably, the active component in step (1) is one or more of phosphomolybdic acid, phosphotungstic acid and silicotungstic acid, and the content of the active component is 10-40 wt%.

[0012] Preferably, in step (1), the additive is metallic Cu, and the molar ratio of Cu to the coordinating atoms in the heteropolyacid is 1:12.

[0013] As a preferred embodiment, in step (1), the Cu source in the raw material salt is Cu(NO3)2·3H2O. The Cu salt and heteropoly acid solution are impregnated onto the support by co-impregnation method, aged for 12 hours, dried at 120°C for 12 hours, and calcined at 300°C for 4 hours to obtain the catalyst precursor loaded with additives and active components.

[0014] Preferably, in step (2), the reducing atmosphere is a mixture of hydrogen and nitrogen, with a hydrogen content of 10 vol%. After treatment at 250°C for 4 hours, the catalyst is obtained by cooling to room temperature in a nitrogen atmosphere.

[0015] Application of a heteropolyacid catalyst in the condensation of formaldehyde and methyl formate to methyl glycolate.

[0016] Preferably, a fixed-bed reactor is used, with paraformaldehyde and methyl formate as raw materials, in a molar ratio of 1:1.5 (based on formaldehyde), at a reaction temperature of 140-160℃, a reaction pressure of 0.5-1.5 MPa, and a mass hourly space velocity of 1-5 h⁻¹. -1 .

[0017] This invention uses common silica as a support and employs a co-impregnation method to prepare catalysts with mild conditions and a stable and controllable process. By doping with an appropriate amount of metal, overflow hydrogen is induced to reduce some coordinating atoms in the heteropolyacid, which act as basic sites. These sites synergistically interact with the strongly acidic sites of the heteropolyacid to promote the cross-condensation of formaldehyde and methyl formate, thereby improving the reactivity and selectivity. The resulting catalyst has advantages such as low reaction temperature, high activity, and good selectivity.

[0018] Beneficial technical effects

[0019] 1. The present invention provides a formaldehyde-methyl formate condensation catalyst with simple steps, mild conditions, and controllable process. The catalyst has acid-base dual function and can synergistically activate formaldehyde and methyl formate to promote their efficient cross condensation to prepare methyl glycolate, thereby improving reaction activity and selectivity.

[0020] 2. Catalysts have advantages such as low reaction temperature and good stability. The reaction process is simple, controllable and easy to operate, and has broad application prospects. Detailed Implementation

[0021] To provide a more detailed description of the present invention, several specific implementation examples are given below, but the present invention is not limited to these embodiments.

[0022] The silica carrier used in the following examples has the following properties: specific surface area 285 m². 2 / g, pore volume 0.79mL / g, pore size 5.2-13.8nm, average pore size 12.6nm.

[0023] Example 1

[0024] (1) Loading aids and active components: Weigh 5.0 g of silica support and add it to 10 mL of a solution containing 1.67 g of H3PMo 12 O 40 The catalyst precursor, containing ·xH2O and 0.22g Cu(NO3)2·3H2O aqueous solution, was aged at room temperature for 12h, dried at 120℃ for 12h, and calcined at 300℃ for 4h to obtain a catalyst precursor supported on additives and active components.

[0025] (2) Overflow hydrogen reduction: The catalyst precursor obtained in step (1) was placed in a mixture of hydrogen and nitrogen (where the hydrogen content was 10 vol%) and treated at 250°C for 4 h. After cooling to room temperature in a nitrogen atmosphere, the catalyst was obtained and designated as catalyst 1. XRD results showed that the crystal phase was H3PMo. 12 O 40 XRF results showed that the catalyst contained 15.8 wt% Mo and 0.9 wt% Cu.

[0026] (3) Catalyst evaluation: The reaction was carried out in a fixed-bed tubular reactor using paraformaldehyde and methyl formate (calculated as formaldehyde, with a molar ratio of formaldehyde to methyl formate of 1:1.5). The reaction temperature was 160℃, the reaction pressure was 1.0 MPa, and the mass hourly space velocity was 1.0 h⁻¹. -1 After gas-liquid separation, the product composition was determined by gas chromatography and liquid chromatography, and the conversion rate of formaldehyde and the selectivity of methyl glycolate were calculated.

[0027] Comparative Example 1

[0028] Compared with Example 1, Comparative Example 1 differs in that no metal additive is added to the 10 mL impregnation solution in step (1), while the rest of the process and conditions are exactly the same as in Example 1; the catalyst obtained is referred to as Catalyst 2.

[0029] Comparative Example 2

[0030] Compared with Example 1, Comparative Example 2 omits step (2) and directly applies the solid catalyst obtained in step (1) to the evaluation of catalytic reaction. The rest of the process and conditions are exactly the same as in Example 1. The catalyst obtained is referred to as catalyst 3.

[0031] Example 2: Different Cu contents

[0032] The difference between Example 2 and Example 1 is that in step (1), 10 mL of impregnation solution contains 0.11 g Cu(NO3)2·3H2O, and the rest of the process and conditions are exactly the same as in Example 1; the catalyst obtained is referred to as catalyst 4.

[0033] Example 3: Different Cu contents

[0034] Compared with Example 1, Example 3 differs in that in step (1), 10 mL of impregnation solution contains 0.44 g Cu(NO3)2·3H2O, while the rest of the process and conditions are exactly the same as in Example 1; the catalyst obtained is referred to as catalyst 5.

[0035] Example 4: Different phosphomolybdic acid contents

[0036] The difference between Example 4 and Example 1 is that in step (1), the 10 mL impregnation solution contains 0.56 g H3PMo. 12 O 40 The catalyst prepared was 6, consisting of xH2O and 0.07g Cu(NO3)2·3H2O, with the remaining processes and conditions exactly the same as in Example 1.

[0037] Example 5: Different phosphomolybdic acid contents

[0038] The difference between Example 5 and Example 1 is that in step (1), the 10 mL impregnation solution contains 3.33 g of H3PMo. 12 O 40 The catalyst prepared was 0.44 g Cu(NO3)2·3H2O and 0.x H2O, with the remaining processes and conditions being exactly the same as in Example 1; the catalyst was designated as catalyst 7.

[0039] Example 6: Different H2 content, reduction temperature, and reduction time

[0040] Compared with Example 1, Example 6 differs in that in step (2), the hydrogen content in the reducing atmosphere is 1 vol%, the reduction time is 10 h, and the rest of the process and conditions are exactly the same as in Example 1; the catalyst obtained is referred to as catalyst 8.

[0041] Example 7: Different H2 content, reduction temperature, and reduction time

[0042] Compared with Example 1, Example 7 differs in that in step (2), the hydrogen content in the reducing atmosphere is 1 vol%, the reduction temperature is 350°C, and the rest of the process and conditions are exactly the same as in Example 1; the catalyst obtained is referred to as catalyst 9.

[0043] Example 8: Different H2 content, reduction temperature, and reduction time

[0044] Compared with Example 1, Example 8 differs in that in step (2), the hydrogen content in the reducing atmosphere is 50 vol%, the reduction time is 1 h, and the rest of the process and conditions are exactly the same as in Example 1; the catalyst obtained is referred to as catalyst 10.

[0045] Example 9: Different H2 content, reduction temperature, and reduction time

[0046] Compared with Example 1, Example 9 differs in that in step (2), the hydrogen content in the reducing atmosphere is 50 vol%, the reduction temperature is 150 °C, and the rest of the process and conditions are exactly the same as in Example 1; the catalyst obtained is referred to as catalyst 11.

[0047] Example 10: Different types of metals

[0048] Compared with Example 1, Example 10 differs in that in step (1), 10 mL of impregnation solution contains 0.27 g Ni(NO3)2·6H2O, while the rest of the process and conditions are exactly the same as in Example 1; the catalyst obtained is referred to as catalyst 12.

[0049] Example 11: Different types of metals

[0050] Compared with Example 1, Example 11 differs in that in step (1), 10 mL of impregnation solution contains 0.24 g Pd(NO3)2·2H2O, while the rest of the process and conditions are exactly the same as in Example 1; the catalyst obtained is referred to as catalyst 13.

[0051] Example 12: Different types of metals

[0052] Compared with Example 1, Example 12 differs in that in step (1), 10 mL of impregnation solution contains 0.29 g Pt(NO3)4, while the rest of the process and conditions are exactly the same as in Example 1; the catalyst obtained is referred to as catalyst 14.

[0053] Example 13: Different types of heteropolyacids

[0054] The difference between Example 13 and Example 1 is that in step (1), 10 mL of the impregnation solution contains 1.67 g of H3PW. 12 O 40 The catalyst prepared was catalyst 15, consisting of xH2O and 0.14g Cu(NO3)2·3H2O, with the remaining processes and conditions being exactly the same as in Example 1.

[0055] Example 14: Different types of heteropolyacids

[0056] The difference between Example 14 and Example 1 is that in step (1), the 10 mL impregnation solution contains 1.67 g H4SiW. 12 O 40 The catalyst prepared was 0.14 g Cu(NO3)2·3H2O and 0.x H2O, with the remaining processes and conditions being exactly the same as in Example 1; the catalyst was designated as Catalyst 16.

[0057] The table below lists the reaction evaluation results of the catalysts prepared by the method described in this invention.

[0058]

[0059] From Examples 1 and Comparative Examples 1 and 2, it can be seen that loaded metal additives and overflow hydrogen reduction are beneficial to improving reaction activity and selectivity; from Examples 1-9, it can be seen that the conditions in Example 1 are optimal; from Examples 1 and 10-12, it can be seen that the promoting effect of additives Cu, Pd and Pt is better than that of Ni, but considering the cost, additive Cu is the best; from Examples 1, 13 and 14, it can be seen that the activity and selectivity of phosphomolybdic acid are higher than those of phosphotungstic acid and silicotungstic acid.

Claims

1. The application of a heteropolyacid catalyst prepared by a method for preparing a heteropolyacid catalyst in the catalytic condensation of formaldehyde and methyl formate to methyl glycolate, characterized in that: A fixed-bed reactor was used, with paraformaldehyde or formaldehyde and methyl formate as the raw materials. The molar ratio of formaldehyde to methyl formate was 1:0.5-5 (based on formaldehyde content). The reaction temperature was 100-200 ℃, the reaction pressure was 0.1-2 MPa, and the mass hourly space velocity (WHSV) was 0.5-10 h⁻¹. -1 ; The heteropolyacid catalyst comprises a metal promoter, a heteropolyacid, and a support. The preparation of the catalyst includes two parts: loading the metal promoter and the active component, and overflow hydrogen reduction. (1) Loading metal additives and active components: Metal salts and heteropoly acids are prepared into solutions, impregnated onto silica supports, and then aged, dried and calcined to obtain catalyst precursors; (2) Overflow hydrogen reduction: The catalyst precursor obtained in step (1) is placed in a reducing atmosphere for treatment to obtain a highly efficient condensation catalyst for formaldehyde and methyl formate.

2. The application according to claim 1, characterized in that: A fixed-bed reactor was used, with paraformaldehyde or formaldehyde and methyl formate as the raw materials. The molar ratio of formaldehyde to methyl formate was 1:1.5 (based on formaldehyde content). The reaction temperature was 140-160 ℃, the reaction pressure was 0.5-1.5 MPa, and the mass hourly space velocity (WHSV) was 1-5 h⁻¹. -1 .

3. The application according to claim 1, characterized in that: In step (1), the support is common silicon dioxide with the following properties: specific surface area 350±100 m². 2 / g, pore volume 0.8±0.4mL / g, average pore size 12±6nm.

4. The application according to claim 1, characterized in that: In step (1), the active component is one or more of phosphomolybdic acid, phosphotungstic acid and silicotungstic acid, and its content in aqueous solution is 5-50 wt%.

5. The application according to claim 1, characterized in that: In step (1), the active component is one or more of phosphomolybdic acid, phosphotungstic acid and silicotungstic acid, and the content in the aqueous solution is 10-40 wt%.

6. The application according to claim 1 or 4, characterized in that: In step (1), the additive is one or more of the metals Cu, Ni, Pd and Pt, and the molar ratio of the metal to molybdenum and / or tungsten in the heteropolyacid is 1:(6-24).

7. The application according to claim 1 or 4, characterized in that: In step (1), the additive is one or more of the metals Cu, Ni, Pd and Pt, and the molar ratio of the metal to molybdenum and / or tungsten in the heteropolyacid is 1:

12.

8. The application according to claim 6, characterized in that: In step (1), Cu salt is Cu(NO3)2·3H2O, Ni salt is Ni(NO3)2·6H2O, Pd salt is Pd(NO3)2·2H2O, and Pt salt is Pt(NO3)4.

9. The application according to claim 1, characterized in that: In step (1), nickel salt and heteropoly acid solution are co-impregnated onto the support by impregnation, left to mature for 4-24 hours, dried at 80-160 ℃ for 4-24 hours, and calcined at 200-500 ℃ for 1-12 hours to obtain a catalyst precursor loaded with additives and active components.

10. The application according to claim 1, characterized in that: In step (1), nickel salt and heteropoly acid solution are co-impregnated onto the support by impregnation method, left to mature for 8-16 h, dried at 100-140℃ for 8-16 h, and calcined at 250-400℃ for 2-8 h to obtain catalyst precursor loaded with additives and active components.

11. The application according to claim 1, characterized in that: In step (1), nickel salt and heteropolyacid solution are co-impregnated onto the support by impregnation method, left to mature for 12 hours, dried at 120 °C for 12 hours, and calcined at 300 °C for 4 hours to obtain catalyst precursor loaded with additives and active components.

12. The application according to claim 1, characterized in that: In step (2), the catalyst precursor is treated in a reducing atmosphere, the reducing gas is a mixture of hydrogen and nitrogen, the hydrogen content is 1-50 vol%; the treatment temperature is 150-350 ℃; the treatment time is 1-10 h; after treatment, it is cooled to room temperature in a nitrogen atmosphere to obtain the catalyst.

13. The application according to claim 1, characterized in that: In step (2), the catalyst precursor is treated in a reducing atmosphere, the reducing gas is a mixture of hydrogen and nitrogen, the hydrogen content is 10-20 vol%; the treatment temperature is 250-300℃; the treatment time is 4-6 h; after treatment, it is cooled to room temperature in a nitrogen atmosphere to obtain the catalyst.

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