Catalyst for preparing alkyl levulinate from furfuryl alcohol as well as preparation method and application of catalyst

Abstract

The invention discloses a catalyst for preparing alkyl levulinate from furfuryl alcohol as well as a preparation method and application of the catalyst. The preparation method of the catalyst comprises the following steps: (1) adding precursor salt of copper and aluminum oxide into deionized water, stirring at normal temperature, then adding 2-methylimidazole, stirring at normal temperature, and finally heating and stirring to obtain a mixed solution; (2) adding sodium carbonate into the mixed solution, heating and stirring, then filtering, washing filter residues with ionized water until the filter residues are neutral, and then drying to obtain a precursor; and (3) roasting the precursor to obtain the catalyst for preparing alkyl levulinate from furfuryl alcohol. The method for preparing the alkyl levulinate by catalyzing the hydrogenolysis of the furfuryl alcohol is mild in reaction condition, the alkyl levulinate is prepared by the hydrogenolysis of the furfuryl alcohol under the mild condition, and the yield of the alkyl levulinate is relatively high.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and particularly relates to a catalyst for preparing alkyl levulinate from furfuryl alcohol, a preparation method thereof, and an application thereof. Background Art

[0002] Alkyl levulinate is a green biomass-based platform chemical, which is often used in the chemical industries such as food additives, pharmaceuticals, and plasticizers, and can also be used as a green solvent for chemical synthesis. The demand is increasing year by year, but its price is expensive, the domestic production capacity is insufficient, and it still depends on imports to a certain extent.

[0003] At present, the production methods of alkyl levulinate mainly include the following: direct esterification of levulinic acid, acid alcoholysis of furfuryl alcohol, and direct alcoholysis of saccharide compounds, etc. Among them, the method of preparing alkyl levulinate by acid alcoholysis of furfuryl alcohol has the advantage of low raw material price and is a preparation method widely used in industry.

[0004] In recent years, the preparation of bio-based alkyl levulinate from furfuryl alcohol has received increasing attention in more and more industries. For example, Chinese Patent CN105646227A discloses a method for preparing ethyl levulinate by converting furfuryl alcohol with a metal oxide (α-Fe 2 O 3 ) as a catalyst. Using furfuryl alcohol as a raw material, the yields of methyl levulinate, ethyl levulinate, and n-butyl levulinate are 73%, 83%, and 86% respectively at 250°C under nitrogen pressure. Although this catalyst has good catalytic effects in the reaction of hydrogenolysis of furfuryl alcohol to prepare alkyl levulinate, the reaction temperature is high and the conditions are harsh, making it difficult to achieve industrial application. CN114195637A discloses a method for preparing ethyl levulinate by using bacterial residue carbon to catalyze furfuryl alcohol. The yield of ethyl levulinate reaches 83.1% under the condition of 160°C. However, the preparation of this catalyst is cumbersome and high-toxic reagents are used, which does not meet the requirements of green environmental protection. CN110963914A discloses a method for preparing alkyl levulinate by regulating the water content, but the addition of a third-component azeotropic agent increases the cost of product separation. In summary, in the existing process of hydrogenolysis of furfuryl alcohol to prepare alkyl levulinate, there are problems of harsh reaction conditions and complex catalyst preparation. Developing a high-performance and low-cost catalyst to achieve the hydrogenolysis of furfuryl alcohol to prepare alkyl levulinate under mild conditions is crucial for improving the market competitiveness of products. Summary of the Invention

[0005] The main purpose of the present invention is to provide a catalyst for preparing alkyl levulinate from furfuryl alcohol with high activity and low cost, a preparation method thereof, and an application thereof.

[0006] To achieve the above object, the present invention provides a preparation method of a catalyst for preparing alkyl levulinate from furfuryl alcohol, including the following steps:

[0007] (1) Add a copper precursor salt and alumina to deionized water, stir at room temperature, then add 2-methylimidazole, stir at room temperature again, and finally stir while heating to obtain a mixed solution.

[0008] (2) Add sodium carbonate to the mixed solution, stir while heating, then filter, wash the filter residue with ionized water until neutral, and then dry to obtain a precursor.

[0009] (3) Calcinate the precursor to obtain the catalyst for preparing alkyl levulinate from furfuryl alcohol.

[0010] Furthermore, in step (1), the copper precursor salt is copper sulfate pentahydrate, and the mass ratio of copper sulfate pentahydrate to alumina and 2-methylimidazole is 5:3:1. The temperature for stirring while heating is 80 °C and the time is 3 h.

[0011] Furthermore, in step (1), the time for both stirrings at room temperature is 30 min.

[0012] Furthermore, in step (2), the addition amount of sodium carbonate is such that the mass ratio to the alumina added in step (1) reaches 1:3. The temperature for stirring while heating is 80 °C and the time is 1 h.

[0013] Furthermore, in step (2), the temperature for drying is 100 °C and the time is 12 h.

[0014] Furthermore, in step (3), the calcination is carried out in an air atmosphere at a temperature of 500 °C for 2 h.

[0015] The present invention also provides a catalyst for preparing alkyl levulinate from furfuryl alcohol, which is prepared according to the above preparation method.

[0016] The present invention also provides a method for catalytic hydrogenolysis of furfuryl alcohol to prepare alkyl levulinate, which includes the following steps: Add furfuryl alcohol, the above catalyst, and an alcohol reaction solvent to a reactor, then introduce nitrogen to displace the air in the reactor, and finally carry out a heating reaction.

[0017] Furthermore, the ratio of furfuryl alcohol to the catalyst is 4 mmol:0.1 g. The temperature for the heating reaction is 120 - 160 °C and the time is 0.5 - 4 h.

[0018] Furthermore, different alkyl levulinates are prepared by selecting different alcohol reaction solvents in the method.

[0019] The beneficial effects of the present invention are as follows:

[0020] The catalyst prepared by the present invention exhibits high activity in the reaction of hydrogenolysis of furfuryl alcohol to prepare alkyl levulinate, which can reduce the amount of catalyst used. With alumina as the carrier, the main active ingredient is copper oxide, and the active promoter is basic nitrogen. The selected sodium carbonate as the precipitant greatly improves the hydrogenolysis activity of the catalyst, and it has advantages in terms of catalytic activity, preparation method, and synthesis cost.

[0021] The catalyst prepared by the present invention is simple to prepare, does not require large-scale production equipment, has low production cost, and can be used for industrial large-scale synthesis.

[0022] The method for catalytic hydrogenolysis of furfuryl alcohol to prepare alkyl levulinate provided by the present invention has mild reaction conditions, realizes the hydrogenolysis of furfuryl alcohol to prepare alkyl levulinate under mild conditions, and has a relatively high yield of alkyl levulinate. Specific Embodiments

[0023] In order to make the technical solutions described in the present invention clearer and more understandable to those skilled in the art, the following examples are listed for illustration. It should be noted that the following examples do not limit the scope of protection required by the present invention.

[0024] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial channels or can be obtained by existing known methods; unless otherwise specified, the methods used in the embodiments of the present invention are all methods mastered by those skilled in the art.

[0025] Example 1

[0026] Preparation of the catalyst for preparing alkyl levulinate from furfuryl alcohol

[0027] The specific steps are as follows:

[0028] (1) Disperse 5 g of copper sulfate pentahydrate and 3 g of alumina in 100 ml of deionized water, stir at 25 °C for 30 min, then add 1 g of 2-methylimidazole, stir at 25 °C for 30 min, and finally transfer it to an oil bath and heat up to 80 °C, and stir constantly for 3 h to obtain a mixed solution;

[0029] (2) Add 1 g of anhydrous sodium carbonate to the mixed solution, stir at 80 °C for 1 h, then filter by suction, wash the filter residue with deionized water until the filtrate is neutral, and then dry at 100 °C for 12 h to obtain a precursor;

[0030] (3) Calcinate the precursor in an air atmosphere at 500 °C for 2 h to obtain the catalyst for preparing alkyl levulinate from furfuryl alcohol.

[0031] Example 2

[0032] Catalytic hydrogenolysis of furfuryl alcohol to prepare alkyl levulinate

[0033] The specific steps are as follows:

[0034] Add 15 mL of ethanol and 12 mmol of furfuryl alcohol into a kettle reactor, then add 0.3 g of the catalyst for preparing alkyl levulinate from furfuryl alcohol prepared in Example 1. Then, introduce nitrogen to displace the air in the kettle reactor. Finally, heat the kettle reactor to 140 °C, stop the reaction after reacting for 2 h, and collect the reaction solution.

[0035] Analyze the reaction solution by gas chromatography, and calculate the amount of substance of furfuryl alcohol and alkyl levulinate in the reaction solution according to the gas chromatography results. The conversion rate of furfuryl alcohol and the yield of alkyl levulinate are calculated by the following formulas:

[0036]

[0037] The results are as follows: the conversion rate of furfuryl alcohol is 99%, and the main reaction product is ethyl levulinate, with a yield of 71%.

[0038] Example 3

[0039] Hydrogenolysis of furfuryl alcohol to prepare alkyl levulinate

[0040] This example was prepared according to the method of Example 2, with the only difference being that ethanol was replaced by methanol. The final reaction results were as follows: the conversion rate of furfuryl alcohol was 99%, and the main product was methyl levulinate, with a yield of 65%.

[0041] Example 4

[0042] Hydrogenolysis of furfuryl alcohol to prepare alkyl levulinate

[0043] This example was prepared according to the method of Example 2, with the only difference being that ethanol was replaced by n-butanol. The final reaction results were as follows: the conversion rate of furfuryl alcohol was 99%, and the main product was n-butyl levulinate, with a yield of 98%.

[0044] Example 5

[0045] Hydrogenolysis of furfuryl alcohol to prepare alkyl levulinate

[0046] This example was prepared according to the method of Example 2, with the only difference being that the reaction temperature was adjusted to 120 °C. The final reaction results were as follows: the conversion rate of furfuryl alcohol was 99%, and the main product was ethyl levulinate, with a yield of 34%.

[0047] Example 6

[0048] Hydrogenolysis of furfuryl alcohol to prepare alkyl levulinate

[0049] This example was prepared according to the method of Example 2, with the only difference being that the reaction temperature was adjusted to 160 °C. The final reaction results were as follows: the conversion rate of furfuryl alcohol was 99%, and the main product was ethyl levulinate, with a yield of 74%.

[0050] Example 7

[0051] Hydrogenolysis of furfuryl alcohol to prepare alkyl levulinates

[0052] This example was prepared according to the method of Example 2, with the only difference being that the reaction time was adjusted to 0.5 hours. The final reaction results were as follows: the conversion rate of furfuryl alcohol was 99%, and the main product was ethyl levulinate, with a yield of 43%.

[0053] Example 8

[0054] Hydrogenolysis of furfuryl alcohol to prepare alkyl levulinates

[0055] This example was prepared according to the method of Example 2, with the only difference being that the reaction time was adjusted to 1 hour. The final reaction results were as follows: the conversion rate of furfuryl alcohol was 99%, and the main product was ethyl levulinate, with a yield of 48%.

[0056] Example 9

[0057] Hydrogenolysis of furfuryl alcohol to prepare alkyl levulinates

[0058] This example was prepared according to the method of Example 2, with the only difference being that the reaction time was adjusted to 4 hours. The final reaction results were as follows: the conversion rate of furfuryl alcohol was 99%, and the main product was ethyl levulinate, with a yield of 46%.

[0059] Comparative Example 1

[0060] Preparation of a comparative catalyst and hydrogenolysis of furfuryl alcohol to prepare alkyl levulinates

[0061] This comparative example was prepared to obtain a comparative catalyst according to the method of Example 1, with the only difference being that the nitrogen source 2-methylimidazole was not added.

[0062] The comparative catalyst was used to hydrogenolyze furfuryl alcohol to prepare alkyl levulinates according to the method of Example 2. The final reaction results were as follows: the conversion rate of furfuryl alcohol was 77%, and the main product was ethyl levulinate, with a yield of 22%.

[0063] Comparative Example 2

[0064] Preparation of a comparative catalyst and hydrogenolysis of furfuryl alcohol to prepare alkyl levulinates

[0065] This comparative example was prepared to obtain a comparative catalyst according to the method of Example 1, with the only difference being that each stirring temperature was adjusted to 25 °C.

[0066] The comparative catalyst was used to catalytically hydrogenolyze furfuryl alcohol to prepare alkyl levulinate according to the method of Example 2. The final reaction results were as follows: the conversion rate of furfuryl alcohol was 85%, and the main product was ethyl levulinate, with a yield of 37%.

[0067] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a catalyst for preparing alkyl levulinate from furfuryl alcohol, characterized in that: The following steps are involved: (1) adding a copper precursor salt and aluminum oxide to deionized water, stirring at room temperature, then adding 2-methylimidazole, stirring at room temperature again, and finally heating and stirring to obtain a mixed solution; (2) adding sodium carbonate to the mixed solution, heating and stirring, filtering, washing the filter residue with deionized water until it is neutral, and drying to obtain a precursor; (3) calcining the precursor to obtain the catalyst for preparing alkyl levulinate from furfuryl alcohol.

2. The method for preparing a catalyst for preparing alkyl levulinate from furfuryl alcohol as claimed in claim 1, characterized in that: In step (1), the copper precursor salt is copper sulfate pentahydrate, the mass ratio of copper sulfate pentahydrate to alumina and 2-methylimidazole is 5:3:1, the temperature of the heating and stirring treatment is 80° C., and the time is 3 hours.

3. The method for preparing a catalyst for preparing alkyl levulinate from furfuryl alcohol as claimed in claim 1 or 2, characterized in that: In step (1), the two normal temperature stirring treatments are both performed for 30 min.

4. The method for preparing a catalyst for preparing alkyl levulinate from furfuryl alcohol as claimed in claim 1 or 2, characterized in that: In step (2), the amount of sodium carbonate added is such that the mass ratio of the sodium carbonate added in step (1) reaches 1:3, and the temperature of the heating and stirring treatment is 80° C. and the time is 1 hour.

5. The method for preparing a catalyst for preparing alkyl levulinate from furfuryl alcohol according to claim 1 or 2, characterized in that: In step (2), the drying temperature is 100° C. and the drying time is 12 h.

6. The method for preparing a catalyst for preparing alkyl levulinate from furfuryl alcohol according to claim 1 or 2, characterized in that: In step (3), the calcination treatment is carried out in an air atmosphere at a temperature of 500° C. for 2 hours.

7. A catalyst for preparing alkyl levulinate from furfuryl alcohol, characterized in that: Prepared by the preparation method according to any one of claims 1 to 6.

8. A method for preparing alkyl levulinate by catalytic hydrogenolysis of furfuryl alcohol, characterized in that: The method comprises the following steps: adding furfuryl alcohol, the catalyst as claimed in claim 7 and an alcohol reaction solvent into a reactor, then introducing nitrogen to replace the air in the reactor, and finally performing heating reaction.

9. The method for preparing alkyl levulinate by catalytic hydrogenolysis of furfuryl alcohol as claimed in claim 8, characterized in that: The ratio of furfuryl alcohol to catalyst is 4 mmol:0.1 g, the heating reaction temperature is 120-160°C, and the time is 0.5-4 h.

10. The method for preparing alkyl levulinate by catalytic hydrogenolysis of furfuryl alcohol as claimed in claim 8, characterized in that: The method prepares different alkyl levulinates by selecting different alcohol reaction solvents.

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