Preparation of heteropolyacid supported catalyst and application of heteropolyacid supported catalyst in catalysis of hydrolysis of methyl glycolate

Abstract

The invention belongs to the technical field of fine chemical engineering, and particularly discloses preparation of a heteropolyacid supported catalyst and application of the heteropolyacid supported catalyst in catalysis of hydrolysis of methyl glycolate, and the preparation of the catalyst comprises the following steps: S1, taking resin as a carrier, rinsing, soaking with water to expand the resin, soaking with an acid solution, an alkali solution and an acid solution in sequence, and drying to obtain the heteropolyacid supported catalyst; washing with water after each time of soaking, and then carrying out next-step soaking, so as to obtain activated resin; and S2, impregnating the activated resin obtained in S1 into a heteropolyacid solution, carrying out ultrasonic oscillation, heating and refluxing, distilling to remove moisture, and carrying out vacuum drying on the obtained material to obtain the heteropolyacid supported catalyst. The catalyst provided by the invention is used for hydrolysis of methyl glycolate, can solve the problem that the existing catalyst is difficult to separate and regenerate, and has the advantages of high activity, high selectivity, easiness in separation and reusability.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and relates to the preparation of a heteropolyacid-supported catalyst and its application in the hydrolysis of methyl glycolate. Background Art

[0002] Glycolic acid is a widely used organic synthesis intermediate and chemical product, mainly used in fields such as chemical cleaning, daily chemical industry, and biodegradable new materials.

[0003] There are many production process routes for glycolic acid, mainly including chloroacetic acid hydrolysis method, formaldehyde cyanidation method, formaldehyde hydrocarboxylation method, dimethyl oxalate hydrogenation hydrolysis method, ethylene glycol selective oxidation method, oxalic acid electrolysis method, ethylene glycol selective oxidation method, biological glycerol catalytic oxidation method, etc. Among them, the dimethyl oxalate hydrogenation hydrolysis method is the main research method at present. First, methyl glycolate is prepared by the hydrogenation of dimethyl oxalate, and then glycolic acid is prepared by the hydrolysis of methyl glycolate.

[0004] Yu Kesheng et al. used phosphotungstic acid as a catalyst in "Hydrolysis of Methyl Glycolate to Prepare Glycolic Acid". The catalyst was repeatedly hydrolyzed 2 times, and the conversion rate of methyl glycolate reached 98.28% and the selectivity reached 97.52%. However, phosphotungstic acid is soluble in water and it is necessary to remove methanol and water under reduced pressure after the reaction, leaving the catalyst in the reaction kettle, which has problems such as complex separation process and easy loss. CN109603907A discloses a cation exchange resin, which is prepared by suspension copolymerization of styrene as a monomer, divinylbenzene as a crosslinking agent, together with a pore-forming agent, an initiator, and a dispersant. The conversion rate of methyl glycolate is close to 60%, and the selectivity of this catalyst is relatively low. Summary of the Invention

[0005] The present invention provides the preparation of a heteropolyacid-supported catalyst and its application in the hydrolysis of methyl glycolate, which can solve the problems of difficult separation and regeneration of existing catalysts, and has the advantages of high activity, high selectivity, easy separation, and reusability.

[0006] In order to achieve the above objectives, the present invention adopts the following technical scheme: A method for preparing a heteropolyacid-supported catalyst, comprising the following steps: S1. Using a resin as a carrier, first rinsing and then soaking it in water to make it swell, and then successively soaking it in an acid solution, an alkali solution, and an acid solution. After each soaking, wash it with water and then proceed to the next soaking to obtain an activated resin; S2. Immerse the activated resin obtained in S1 into a heteropolyacid solution, first perform ultrasonic oscillation, then heat reflux, and then distill to remove water. The obtained material is dried under vacuum to obtain a heteropolyacid-supported catalyst.

[0007] Optionally, the resin is a strong acid type ion exchange resin.

[0008] Optionally, the time for the resin to soak and swell in water is 12 - 48 h.

[0009] Optionally, the acid solution is a hydrochloric acid or acetic acid solution with a mass concentration of 1 - 10%; the soaking time each time is 6 - 10 h.

[0010] Optionally, the alkali solution is a sodium hydroxide solution with a mass concentration of 1 - 5%, and the soaking time is 5 - 8 h.

[0011] Optionally, the solute in the heteropolyacid solution described in S2 is phosphotungstic acid or phosphomolybdic acid, and the solvent is water or ethanol.

[0012] Optionally, the temperature for heating and refluxing in S2 is 60 - 90 °C, and the reflux time is 4 - 6 h; after the reflux reaction, the water is evaporated to dryness.

[0013] Optionally, the activated resin in S2 is impregnated with heteropolyacid, ultrasonic oscillation, heating and refluxing, and evaporation of water are repeated twice, and then vacuum drying is carried out at 50 - 70 °C. The present invention also relates to the application of the heteropolyacid - supported catalyst obtained by the described preparation method in the hydrolysis of methyl glycolate to prepare glycolic acid.

[0014] Optionally, during the hydrolysis reaction, the molar ratio of methyl glycolate to water is 4 - 30:1, the catalyst dosage is 0.1 - 5 wt%, the reaction time is 1 - 6 h, and the reaction temperature is 70 - 90 °C.

[0015] The present invention has the following beneficial effects: The present invention uses phosphomolybdic acid or phosphotungstic acid as the active center, has high catalytic activity, uses a strongly acidic ion - exchange resin as the carrier, has advantages such as a large specific surface area, a developed pore structure, and good thermal stability. Before loading the heteropolyacid, activation treatment is carried out. First, water soaking and swelling are used to remove water - soluble impurities in the resin, acid solution soaking is used to remove acid - soluble impurities, then alkali solution soaking is used to wash away alkali - soluble impurities, and finally, secondary acid solution soaking is carried out to transform the resin into the H - type. The activated resin is then loaded with heteropolyacid. The hydrogen - type cation - exchange resin can dissociate H + , and the cations can be loaded on the resin surface. During loading, two or more loadings and refluxes are required to ensure that more H + is dissociated, and at the same time, the loading amount of cationic active components is increased.

[0016] The present invention uses a resin - supported heteropolyacid as a catalyst, which can stabilize the heteropolyacid structure and optimize the catalytic performance of the heteropolyacid; this catalyst is easy to recycle and can be used repeatedly. Detailed implementation modes

[0017] The embodiments of the present invention will be described in detail below in conjunction with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

[0018] Example 1 S1. Using 001×7 strongly acidic ion exchange resin as the carrier, first rinse it and then soak it in water for 10 h to make it swell. After filtration, soak it in 10% hydrochloric acid solution for 6 h, stir at 30 °C for 6 h, wash the resin with pure water until the pH is between 4 and 5, then soak it in 5% NaOH solution for 6 h, stir at 30 °C, and after stirring, wash it with clear water until neutral. Continue to soak it in 10% hydrochloric acid solution for 10 h, and finally wash it with pure water until neutral to obtain the activated resin. S2. Immerse the activated resin obtained in S1 into 50% phosphotungstic acid solution, first perform ultrasonic oscillation for 3 h, then heat and reflux at 80 - 90 °C for 4 h, and then rotary evaporate to remove water; Immerse the dried catalyst into the heteropolyacid solution again, reflux and rotary evaporate to remove water again; Then dry it under vacuum at 50 °C overnight to obtain the heteropolyacid-supported catalyst. Denote it as Catalyst 1.

[0019] Use the catalyst obtained in Example 1 for the experiment of preparing glycolic acid by hydrolysis of methyl glycolate: During the hydrolysis reaction, the molar ratio of methyl glycolate to water is 10:1, the catalyst dosage is 1 wt%, the reaction time is 3 h, and the reaction temperature is 80 - 90 °C. The results are shown in Table 1.

[0020] Example 2 S1. Using D001 strongly acidic ion exchange resin as the carrier, first rinse it and then soak it in water for 10 h to make it swell. After filtration, soak it in 2% hydrochloric acid solution for 8 h, stir at 30 °C for 6 h, wash the resin with pure water until the pH is between 4 and 5, then soak it in 1% NaOH solution for 6 h, stir at 30 °C, and after stirring, wash it with clear water until neutral. Continue to soak it in 2% hydrochloric acid solution for 8 h, and finally wash it with pure water until neutral to obtain the activated resin. S2. Immerse the activated resin obtained in S1 into 30% phosphotungstic acid solution, first perform ultrasonic oscillation for 3 h, then heat and reflux at 80 - 90 °C for 6 h, and then rotary evaporate to remove water; Immerse the dried catalyst into the heteropolyacid solution again, reflux and rotary evaporate to remove water again; Then dry it under vacuum at 50 °C overnight to obtain the heteropolyacid-supported catalyst. Denote it as Catalyst 2.

[0021] Use the catalyst obtained in Example 2 for the experiment of preparing glycolic acid by hydrolysis of methyl glycolate: During the hydrolysis reaction, the molar ratio of methyl glycolate to water is 10:1, the catalyst dosage is 1 wt%, the reaction time is 3 h, and the reaction temperature is 80 - 90 °C. The results are shown in Table 1.

[0022] Example 3 S1. Using CD350 strongly acidic ion exchange resin as the carrier, first rinse it and then soak it in water for 10 h to make it swell. After filtration, soak it in 5% hydrochloric acid solution for 6 h, stir at 30 °C for 6 h, wash the resin with pure water until the pH is 4 - 5, then soak it in 3% NaOH solution for 6 h, stir at 30 °C, and after the stirring ends, wash it with clear water until neutral. Continue to soak it in 5% hydrochloric acid solution for 6 h, and finally wash it with pure water until neutral to obtain the activated resin; S2. Immerse the activated resin obtained in S1 into 50% phosphomolybdic acid solution, first perform ultrasonic oscillation for 3 h, then heat and reflux at 80 - 90 °C for 4 h, and then rotary evaporate to remove water; Immerse the dried catalyst again in the heteropolyacid solution, reflux and rotary evaporate to remove water again; Then dry it under vacuum at 50 °C overnight to obtain the heteropolyacid-supported catalyst. Denote it as Catalyst 3.

[0023] Use the catalyst obtained in Example 3 for the experiment of preparing glycolic acid by hydrolysis of methyl glycolate: During the hydrolysis reaction, the molar ratio of methyl glycolate to water is 10:1, the catalyst dosage is 1 wt%, the reaction time is 3 h, and the reaction temperature is 80 - 90 °C. The results are shown in Table 1.

[0024] Example 4 S1. Using Amberlite IR-120 strongly acidic ion exchange resin as the carrier, first rinse it and then soak it in water for 10 h to make it swell. After filtration, soak it in 5% hydrochloric acid solution for 5 h, stir at 30 °C for 6 h, wash the resin with pure water until the pH is 4 - 5, then soak it in 5% NaOH solution for 5 h, stir at 30 °C, and after the stirring ends, wash it with clear water until neutral. Continue to soak it in 5% hydrochloric acid solution for 5 h, and finally wash it with pure water until neutral to obtain the activated resin; S2. Immerse the activated resin obtained in S1 into 70% phosphomolybdic acid solution, first perform ultrasonic oscillation for 3 h, then heat and reflux at 70 - 80 °C for 6 h, and then distill to remove water; Immerse the dried catalyst again in the heteropolyacid solution, reflux and rotary evaporate to remove water again; Then dry it under vacuum at 50 °C overnight to obtain the heteropolyacid-supported catalyst. Denote it as Catalyst 4.

[0025] Use the catalyst obtained in Example 4 for the experiment of preparing glycolic acid by hydrolysis of methyl glycolate: During the hydrolysis reaction, the molar ratio of methyl glycolate to water is 10:1, the catalyst dosage is 1 wt%, the reaction time is 3 h, and the reaction temperature is 80 - 90 °C. The results are shown in Table 1.

[0026] Table 1

[0027] As shown in Table 1, from the results of the above catalysts, the catalytic activities of the catalysts corresponding to different carriers and different components are different. Phosphotungstic acid was respectively loaded on 001×7 strongly acidic ion exchange resin and D001 strongly acidic ion exchange resin, and the conversion rates of methyl glycolate were 100% and 97% respectively, and the selectivities were both above 99%. Phosphomolybdic acid was respectively loaded on CD350 strongly acidic ion exchange resin and Amberlite IR-120 strongly acidic ion exchange resin, and the conversion rates of methyl glycolate were 98% and 99.5% respectively, and the selectivities were 98.7% and 99.3% respectively. Both phosphotungstic acid and phosphomolybdic acid showed good catalytic activities. Among them, the catalyst with phosphotungstic acid loaded on 001×7 strongly acidic ion exchange resin had better activity, mainly because there were a large number of exchangeable H + on the resin surface. The higher the exchange capacity, the more the amount of active components loaded, and the higher the catalytic activity of the catalyst.

[0028] Comparative Example 1 S1: Using 001×7 strongly acidic ion exchange resin as the carrier, first rinse and then soak it in water for 10 h to make it swell. After filtration, soak it in 10% hydrochloric acid solution for 6 h, stir at 30 °C for 6 h, and wash the resin with pure water until neutral to obtain the activated resin; S2: Immerse the activated resin obtained in S1 into 50% phosphotungstic acid solution, first perform ultrasonic oscillation for 3 h, then heat and reflux at 80-90 °C for 4 h, and then rotary evaporate to remove water; Immerse the dried catalyst in the heteropolyacid solution again, reflux and rotary evaporate to remove water again; Then dry it under vacuum at 50 °C overnight to obtain the heteropolyacid-loaded catalyst. Recorded as Comparative Catalyst 1.

[0029] The catalyst obtained in Comparative Example 1 was used in the experiment of preparing glycolic acid by hydrolysis of methyl glycolate: During the hydrolysis reaction, the molar ratio of methyl glycolate to water was 10:1, the catalyst dosage was 1 wt%, the reaction time was 3 h, and the reaction temperature was 80-90 °C. The results are shown in Table 2.

[0030] Comparative Example 2 S1: Using 001×7 strongly acidic ion exchange resin as the carrier, first rinse and then soak it in water for 10 h to make it swell. After filtration, soak it in 10% hydrochloric acid solution for 6 h, stir at 30 °C for 6 h, wash the resin with pure water until the pH is 4-5, then soak it in 5% NaOH solution for 6 h, stir at 30 °C, and after stirring, wash it with water until neutral to obtain the activated resin; S2. Immerse the activated resin obtained in S1 into a 50% phosphotungstic acid solution, first perform ultrasonic oscillation for 3 h, then heat and reflux at 80 - 90 °C for 4 h, and then distill to remove water; Immerse the catalyst after evaporation again into the heteropolyacid solution, reflux and rotary evaporate again to remove water; Then dry it under vacuum at 50 °C overnight to obtain the heteropolyacid-supported catalyst. Denote it as Comparative Catalyst 2.

[0031] Use the catalyst obtained in Comparative Example 2 for the experiment of preparing glycolic acid by hydrolysis of methyl glycolate: During the hydrolysis reaction, the molar ratio of methyl glycolate to water is 10:1, the catalyst dosage is 1 wt%, the reaction time is 3 h, and the reaction temperature is 80 - 90 °C. The results are shown in Table 2.

[0032] Comparative Example 3 Dissolve phosphotungstic acid completely in deionized water, take a certain amount of unactivated ion exchange resin and immerse it in the phosphotungstic acid aqueous solution, first perform ultrasonic oscillation for 2 h, then heat and reflux at 80 - 90 °C for 4 h, and then distill to remove water; Immerse the catalyst after evaporation again into the heteropolyacid solution, reflux and rotary evaporate again to remove water; Then dry it under vacuum at 50 °C overnight to obtain the heteropolyacid-supported catalyst. Denote it as Comparative Catalyst 3.

[0033] Use the catalyst obtained in Comparative Example 3 for the experiment of preparing glycolic acid by hydrolysis of methyl glycolate: During the hydrolysis reaction, the molar ratio of methyl glycolate to water is 10:1, the catalyst dosage is 1 wt%, the reaction time is 3 h, and the reaction temperature is 80 - 90 °C. The results are shown in Table 2.

[0034] Table 2

[0035] As shown in Table 2, from the above results, after the strongly acidic resin is activated by different methods, the activities of the catalysts are different. When the resin is acidified and alkalized respectively, the activities of the treated catalysts decrease. After acidification, the conversion rate of methyl glycolate decreases to 96%, and after alkalization, the conversion rate of methyl glycolate decreases to 93.2%. The decrease in selectivity is not significant. When the resin support is not activated, the conversion rate of methyl glycolate further decreases to 90.5, and at the same time, the selectivity of glycolic acid also decreases. It shows that the alkali-soluble impurities and acid-soluble impurities contained in the resin have a certain impact on it.

[0036] Example 5 Immerse the used Catalyst 1 in a 5% hydrochloric acid solution for 3 h, then perform column elution with the hydrochloric acid solution, and finally wash it with water until it is close to neutral, and dry it at 50 °C to obtain the regenerated Catalyst 5.

[0037] Use the regenerated Catalyst 5 for the experiment of preparing glycolic acid by hydrolysis of methyl glycolate. The reaction conditions are the same as those in Example 1. The results are shown in Table 3.

[0038] The used regenerated catalyst 5 was immersed in a 5% hydrochloric acid solution for 3 h, then rinsed through a column with the hydrochloric acid solution, and finally washed with water until it was nearly neutral and dried at 50 °C to obtain regenerated catalyst 6.

[0039] The regenerated catalyst 6 was used in the experiment of preparing glycolic acid by hydrolysis of methyl glycolate. The reaction conditions were the same as those in Example 1, and the results are shown in Table 3.

[0040] The used regenerated catalyst 6 was immersed in a 5% hydrochloric acid solution for 3 h, then rinsed through a column with the hydrochloric acid solution, and finally washed with water until it was nearly neutral and dried at 50 °C to obtain regenerated catalyst 7.

[0041] The regenerated catalyst 7 was used in the experiment of preparing glycolic acid by hydrolysis of methyl glycolate. The reaction conditions were the same as those in Example 1, and the results are shown in Table 3.

[0042] Table 3

[0043] It can be seen from Table 3 that after the catalyst 1 was reused 3 times, the conversion rate of methyl glycolate did not change, and the selectivity of glycolic acid decreased by 0.1 percentage point. From the above data, it can be seen that the catalyst prepared by this method has good stability in catalytic activity, and the activity of the regenerated catalyst is not much different from that of the fresh catalyst, and it can be reused and industrially produced.

[0044] The above embodiments describe the preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the appended claims.

Claims

1. A method for preparing a heteropolyacid supported catalyst, characterized in that: The following steps are involved: S1, using the resin as a carrier, first rinsing and then soaking it in water to make it swell, then soaking it in an acid solution, an alkaline solution and an acid solution in sequence, washing it with water after each soaking and then soaking it in the next step to obtain an activated resin; S2, impregnating the activated resin obtained in S1 into a heteropoly acid solution, first subjecting it to ultrasonic vibration, then heating it under reflux, and then distilling it to remove moisture. The obtained material is vacuum dried to obtain a heteropoly acid-supported catalyst.

2. The preparation method according to claim 1, characterized in that: The resin is a strongly acidic cation exchange resin.

3. The preparation method according to claim 1, characterized in that: The time for the resin to swell after soaking in water is 12-48 hours.

4. The preparation method according to claim 1, characterized in that: The acid solution is a hydrochloric acid or acetic acid solution with a mass concentration of 1-10%; each immersion time is 6-10 hours.

5. The preparation method according to claim 1, characterized in that: The alkaline solution is a sodium hydroxide solution with a mass concentration of 1-5%, and the soaking time is 5-8 hours.

6. The preparation method according to claim 1, characterized in that: The solute in the heteropolyacid solution described in S2 is phosphotungstic acid or phosphomolybdic acid, and the solvent is water or ethanol.

7. The preparation method according to claim 1, characterized in that: The heating reflux temperature in S2 is 60-90°C, and the reflux time is 4-6h; after the reflux reaction, the water is evaporated to dryness.

8. The preparation method according to claim 1, characterized in that: The activated resin in S2 is impregnated with the heteropoly acid, subjected to ultrasonic oscillation, heating under reflux and distillation to remove water, and then dried under vacuum at 50-70°C.

9. Use of the heteropolyacid supported catalyst obtained according to the preparation method according to any one of claims 1 to 8 in the hydrolysis of methyl glycolate to prepare glycolic acid.

10. The use according to claim 9, characterized in that: During the hydrolysis reaction, the molar ratio of methyl glycolate to water is 4-30:1, the amount of catalyst is 0.1-5wt%, the reaction time is 1-6h, and the reaction temperature is 70-90°C.

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