A kind of preparation method of ethyl levulinate

Abstract

The present invention proposes a preparation method of ethyl levulinate, using sugar alcohol as raw material, using a mixture of anhydrous ethanol and ethyl levulinate as solvent, hydrolyzing under the action of an acidic catalyst at 110°C-130°C under normal pressure, and the obtained hydrolyzate is refined and separated to obtain ethyl levulinate; in the solvent, the weight ratio of anhydrous ethanol to ethyl levulinate is 1:10-15. The present invention improves the boiling point of the solvent by adding a certain proportion of mixed solvents of product ethyl levulinate and alcoholysis reagent anhydrous ethanol, and can prepare ethyl levulinate with high yield without using an autoclave, reduce potential production risks, simplify production equipment, reduce the difficulty of production operation and the qualification requirements of operators; the prepared ethyl levulinate has excellent quality, stable yield and high production capacity, and the prepared ethyl levulinate can be applied to the production of subsequent batches without repeated purchase as raw materials.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, and in particular to a method for preparing ethyl levulinate. Background Art

[0002] The existing methods for preparing levulinic acid esters generally use the biomass-based raw material furfuryl alcohol, which is obtained by alcoholysis and ring-opening with the corresponding alcohol with the assistance of an acidic catalyst. Since furfuryl alcohol has the characteristic of easy self-polymerization, the high-yield preparation of levulinic acid esters requires the dilution and dropwise addition of furfuryl alcohol, and the reaction temperature is preferably in the range of 120 to 130°C. For ethyl levulinate, the reaction temperature is obviously higher than that of its corresponding anhydrous ethanol, so the conventional method for preparing levulinic acid esters cannot be replicated and applied to ethyl levulinate. The present invention provides a new method for preparing ethyl levulinate.

[0003] At present, the common innovation direction of ethyl levulinate process focuses on the application of high-efficiency catalytic materials. The process generally adopts the method of high-pressure reaction and high solvent volume. By increasing the pressure in the kettle and the boiling point of anhydrous ethanol, the temperature required for high-yield preparation is achieved. Chinese patent CN118307401A discloses a high-pressure preparation process of ethyl levulinate using sulfonated activated carbon. When the molar ratio of furfuryl alcohol to ethanol is 0.005, the GC calculated yield in the reaction solution can reach 95.3%, but when the molar ratio of furfuryl alcohol to ethanol is increased to 0.1, the GC calculated yield is only 52.3%. Chinese patent CN117229142A provides a method for preparing ethyl levulinate by alcoholysis of furfuryl alcohol using a supported non-precious metal catalyst. The selectivity of ethyl levulinate can reach 98%, but the mass ratio of furfuryl alcohol to ethanol is fixed at 0.01.

[0004] In large-scale industrial production, reaction efficiency, production risk control, and process cost are the core of mature processes. Compared with ordinary enamel reactors, high-pressure reactors have higher potential risks, complex equipment operation, and strict qualifications for operators. It is estimated that the purchase and maintenance costs of high-pressure reactors are 2 to 3 times that of ordinary enamel reactors, and the costs of related operating teams are also 1.5 to 2 times, and enterprises need to apply for relevant qualifications and licenses before they can carry out compliant and legal high-pressure production operations. High solvent usage is also a problem that needs to be avoided in large-scale industrial production. Without considering energy and time issues, according to the 90% recovery rate of the distillation equipment, the mass ratio of furfuryl alcohol to ethanol in Chinese patent CN117229142A is 0.01, that is, the synthesis of each ton of ethyl levulinate may consume about 7 to 8 tons of ethanol, greatly increasing the overall production cost. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the prior art. The present invention provides a method for preparing ethyl levulinate, which realizes the normal pressure preparation of ethyl levulinate, improves the preparation safety, and reduces the operation difficulty of the preparation process.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing ethyl levulinate, using sugar alcohol as a raw material, a mixture of anhydrous ethanol and ethyl levulinate as a solvent, carrying out alcoholysis under the action of an acidic catalyst at 110°C-130°C under normal pressure, and distilling and separating the obtained hydrolyzate to obtain ethyl levulinate;

[0007] In the solvent, the weight ratio of anhydrous ethanol to ethyl levulinate is 1:10-15, with the best ratio being about 1:13.

[0008] Further, the following steps are included:

[0009] S1, adding sugar alcohol and part of anhydrous ethanol into a dropping kettle and stirring evenly to obtain an anhydrous ethanol solution of sugar alcohol;

[0010] S2, add ethyl levulinate, concentrated sulfuric acid and the remainder of anhydrous ethanol into the synthesis kettle and start stirring, heat the temperature in the kettle to 110-130° C., dropwise add the solution obtained in S1 into the synthesis kettle and keep warm for reaction;

[0011] S3. After the reaction is completed, the temperature is cooled to room temperature, sulfuric acid is quenched with triethylamine, and ethanol is recovered and then distilled under reduced pressure to obtain ethyl levulinate.

[0012] Furthermore, in the anhydrous ethanol solution of the sugar alcohol, the weight ratio of anhydrous ethanol to the sugar alcohol is 1-3:2-5, with the best ratio being about 3:5.

[0013] Furthermore, in the preparation process of ethyl levulinate, the raw materials used, by mass fraction, include 20%-30% sugar alcohol, 15%-20% anhydrous ethanol, 50%-60% ethyl levulinate, 0.1%-1% concentrated sulfuric acid and 0.2%-2% triethylamine.

[0014] Furthermore, the anhydrous ethanol solution of the sugar alcohol is added dropwise within 2-3 hours.

[0015] Furthermore, during the heat preservation reaction process, the temperature is kept at 110° C.-130° C. for 2-3 hours.

[0016] Compared with the prior art, the beneficial effects of the present invention include:

[0017] 1) By adding a certain proportion of a mixed solvent composed of the product ethyl levulinate and anhydrous ethanol as an alcoholysis reagent, the boiling point of the solvent is increased, and a high-yield ethyl levulinate can be prepared without using a high-pressure reactor, thereby reducing potential production risks, simplifying production equipment, and reducing the difficulty of production operations and the qualification requirements of operators.

[0018] 2) The prepared ethyl levulinate has excellent quality, stable yield and high production capacity, and the prepared ethyl levulinate has also been verified to be fully applicable to the production of subsequent batches without the need to repeatedly purchase it as a raw material. DETAILED DESCRIPTION

[0019] It is easy to understand that according to the technical solution of the present invention, without changing the essential spirit of the present invention, a person skilled in the art can propose a variety of interchangeable structural modes and implementation modes. Therefore, the following specific implementation modes are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as the whole of the present invention or as a limitation or restriction to the technical solution of the present invention.

[0020] A preparation method of ethyl levulinate, which uses sugar alcohol as a reaction starting material, anhydrous ethanol as a reaction reagent for alcoholysis of the sugar alcohol, a diluent for the sugar alcohol and a combined mixed solvent, ethyl levulinate as a component mixed solvent of a final product, concentrated sulfuric acid as an acidic catalyst, and triethylamine as a neutralizer for the concentrated sulfuric acid.

[0021] The present invention adds the final product ethyl levulinate to anhydrous ethanol as a solvent to form a mixed solvent as a method of increasing the boiling point of anhydrous ethanol under normal pressure. The following table shows the results of the boiling point study of mixtures of different proportions:

[0022]

[0023]

[0024] In order to provide the temperature required for high-yield reactions and ensure sufficient anhydrous ethanol for rapid alcoholysis, the ratio of anhydrous ethanol to ethyl levulinate as the initial mixed solvent should be in the range of 1:15-1:10, with 1:13 being the best.

[0025] In order to avoid the change in the ratio of anhydrous ethanol and ethyl levulinate in the system after the reaction of furfuryl alcohol diluted with anhydrous ethanol, which would lead to a decrease in the internal temperature and affect the subsequent reaction effect, the ratio of anhydrous ethanol to furfuryl alcohol should be controlled in the range of 1:2-3:5, with 3:5 being the best, to ensure that in addition to the anhydrous ethanol participating in the reaction, the additional anhydrous ethanol used for dilution will not lower the overall internal temperature.

[0026] Due to the easy self-polymerization of furfuryl alcohol, the temperature for the start of dripping needs to be controlled in the range of 110-130°C, with 120°C being the best. The dripping time should be extended as much as possible, but it should be controlled within 2-4h to avoid the total reaction time being too long, which will increase the difficulty of distillation.

[0027] Therefore, a preparation method of ethyl levulinate specifically comprises the following steps:

[0028] S1. Add 0.8-1.0 ton of furfuryl alcohol and 0.4-0.8 ton of anhydrous ethanol to a 2-ton dropping kettle in sequence and stir evenly.

[0029] S2, add 1.5-2.5 tons of ethyl levulinate, 0.1-0.3 tons of anhydrous ethanol, and 10-100kg of concentrated sulfuric acid to a 5-ton synthesis reactor, start the condenser refrigerant circulation, start stirring, and introduce steam into the reactor jacket to start heating. After the temperature in the reactor is heated to 110-130°C, start dripping the anhydrous ethanol solution of furfuryl alcohol that is stirred evenly, and control the dripping rate so that the anhydrous ethanol solution of furfuryl alcohol is dripped in a total of 2-3 hours. After the dripping is completed, continue to keep warm at 110-130°C for 2-3h, and control the reaction fully in the sampling GC.

[0030] After S3 and the reaction are completed, the reaction solution is cooled to room temperature, 20-200kg of triethylamine is added and stirred for 1 hour to quench sulfuric acid, and then transferred to a rectification reactor. Hot water circulation is introduced into the reactor jacket, the condenser refrigerant circulation is turned on, the vacuum pump is turned on, and ethanol is recovered by vacuum distillation. After there is substantially no liquid dripping at the condenser, the hot water in the jacket is removed, steam is introduced into the jacket, and ethyl levulinate is collected by vacuum distillation, and the ethyl levulinate added as a solvent is deducted to obtain about 1-1.2 tons.

[0031] The technical effects of the present application are specifically described below in conjunction with the embodiments, in which the reaction process is carried out in a small amount in a four-necked reaction bottle.

[0032] Experimental Example 1

[0033] Weigh 24.6 g of furfuryl alcohol and 14.41 g of anhydrous ethanol, stir well, and set aside.

[0034] Add 50.12g of ethyl levulinate, 3.80g of anhydrous ethanol and 0.60g of concentrated sulfuric acid to a 250mL four-necked reaction bottle, stir evenly, turn on the oil bath, and set the temperature to 135°C. After the internal temperature is heated to 120°C, start dripping the prepared anhydrous ethanol solution of furfuryl alcohol, control the dripping rate, and complete the dripping in 2 hours and 28 minutes. During the dripping process, the internal temperature is maintained in the range of 120-130°C. After the dripping is completed, the internal temperature is 125°C, and the temperature is maintained for 2 hours. The reaction is fully controlled in the GC sampling.

[0035] After the reaction was completed, the reaction solution was cooled to room temperature, 1.50 g of triethylamine was added and stirred for 1 hour to quench the sulfuric acid. After sufficient quenching, the vacuum distillation apparatus was replaced, the oil bath pot and vacuum pump were turned on, the temperature was set to 55 ° C, and ethanol was recovered by vacuum distillation. After almost no liquid dripped, the temperature was increased to 90 ° C, and 79.84 g of ethyl levulinate was collected by vacuum distillation. After deducting the ethyl levulinate added as a solvent, 29.72 g was obtained, and the yield was 82.6%.

[0036] Experimental Example 2

[0037] Weigh 196.01 g of furfuryl alcohol and 115.21 g of anhydrous ethanol, stir well, and set aside.

[0038] Add 400.02g of ethyl levulinate, 29.87g of anhydrous ethanol and 4.04g of concentrated sulfuric acid to a 1000mL four-necked reaction bottle, stir evenly, turn on the oil bath, and set the temperature to 135°C. After the internal temperature is heated to 120°C, start dripping the prepared anhydrous ethanol solution of furfuryl alcohol, control the dripping rate, and complete the dripping in 3 hours and 53 minutes. During the dripping process, the internal temperature is maintained in the range of 120-130°C. After the dripping is completed, the internal temperature is 127°C, and the temperature is maintained for 2h. The reaction is fully controlled in the GC sampling.

[0039] After the reaction was completed, the reaction solution was cooled to room temperature, 10.02 g of triethylamine was added and stirred for 1 hour to quench the sulfuric acid. After sufficient quenching, the vacuum distillation apparatus was replaced, the oil bath pot and vacuum pump were turned on, the temperature was set to 55 ° C, and ethanol was recovered by vacuum distillation. After almost no liquid dripped, the temperature was increased to 90 ° C, and 624.65 g of ethyl levulinate was collected by vacuum distillation. After deducting the ethyl levulinate added as a solvent, 224.63 g was obtained, with a yield of 78.0%.

[0040] Experimental Example 3

[0041] Weigh 196.67 g of furfuryl alcohol and 114.40 g of anhydrous ethanol, stir well, and set aside.

[0042] Add 402.90g of ethyl levulinate prepared in Experimental Example 2, 30.28g of anhydrous ethanol and 4.11g of concentrated sulfuric acid to a 1000mL four-necked reaction bottle, stir evenly, turn on the oil bath, and set the temperature to 135°C. After the internal temperature is heated to 120°C, start dripping the prepared anhydrous ethanol solution of furfuryl alcohol, and increase the dripping rate appropriately compared with Experimental Example 2. The dripping is completed in 2 hours and 44 minutes. During the dripping process, the internal temperature is maintained in the range of 120-130°C. After the dripping is completed, the internal temperature is 126°C, and the temperature is maintained for 2h. The reaction is fully controlled in the GC sampling.

[0043] After the reaction was completed, the reaction solution was cooled to room temperature, 10.16 g of triethylamine was added and stirred for 1 hour to quench the sulfuric acid. After sufficient quenching, the vacuum distillation apparatus was replaced, the oil bath pot and vacuum pump were turned on, the temperature was set to 55 ° C, and ethanol was recovered by vacuum distillation. After there was basically no liquid dripping, the temperature was increased to 90 ° C, and 638.02 g of ethyl levulinate was collected by vacuum distillation. After deducting the ethyl levulinate added as a solvent, 235.12 g was obtained, and the yield was 81.6%.

[0044] The ethyl levulinate obtained in Example 3 was tested, and its performance indicators are shown in the following table:

[0045]

[0046]

[0047] Comparative Example 1

[0048] Add 4.9g furfuryl alcohol, 230.02g anhydrous ethanol (molar ratio 1:100) and 0.15g concentrated sulfuric acid to a 500mL tetrafluoroethylene-lined autoclave, stir evenly, tighten the autoclave cover, set the temperature to 135℃, start the heat transfer oil circulation, and keep the internal temperature at 120℃ for 4h.

[0049] After the reaction was completed, the reaction solution was cooled to room temperature, and 0.31 g of triethylamine was added and stirred for 1 hour to quench the sulfuric acid. After sufficient quenching, the vacuum distillation apparatus was replaced, the oil bath pot and vacuum pump were turned on, the temperature was set to 55 ° C, and ethanol was recovered by vacuum distillation. After there was basically no liquid dripping, the temperature was increased to 90 ° C, and 5.41 g of ethyl levulinate was collected by vacuum distillation, with a yield of 74.7%.

[0050] Comparative Example 2

[0051] Add 24.62g furfuryl alcohol, 115g anhydrous ethanol (molar ratio 1:10) and 0.60g concentrated sulfuric acid to a 500mL tetrafluoroethylene-lined autoclave, stir evenly, tighten the autoclave cover, set the temperature to 135℃, start the heat transfer oil circulation, and keep the internal temperature at 120℃ for 4h.

[0052] After the reaction was completed, the reaction solution was cooled to room temperature, and 1.52 g of triethylamine was added and stirred for 1 hour to quench the sulfuric acid. After sufficient quenching, the vacuum distillation apparatus was replaced, the oil bath pot and vacuum pump were turned on, the temperature was set to 55 ° C, and the ethanol was recovered by vacuum distillation. After there was basically no liquid dripping, the temperature was increased to 90 ° C, and 20.88 g of ethyl levulinate was collected by vacuum distillation, with a yield of 57.66%.

[0053] By comparing the comparative example with the embodiment, it is not difficult to find that, using a mixture of anhydrous ethanol and ethyl levulinate as a solvent, from the perspective of large-scale industrial production, using a normal pressure reactor to replace a high pressure reactor reduces the cost of equipment and personnel, and reduces potential production risks; the greatly reduced amount of solvent further reduces production costs, reduces the loss and energy consumption of solvent recovery, and increases production capacity, making the entire production process more in line with the trend of the times of green chemistry. And by replacing the one-pot feeding method of the autoclave with dilution and dripping of furfuryl alcohol, the self-polymerization of furfuryl alcohol in a low solvent state is controlled, and the yield is also improved compared with the high pressure reactor.

[0054] The technical scope of the present invention is not limited to the contents in the above description. Those skilled in the art can make various deformations and modifications to the above embodiments without departing from the technical idea of ​​the present invention, and these deformations and modifications should all fall within the protection scope of the present invention.

Claims

1. A method for preparing ethyl levulinate, characterized in that: Using sugar alcohol as raw material and a mixture of anhydrous ethanol and ethyl levulinate as solvent, alcoholysis is carried out under the action of an acid catalyst at 110°C-130°C under normal pressure, and the obtained product is distilled and separated to obtain ethyl levulinate; In the solvent, the weight ratio of anhydrous ethanol to ethyl levulinate is 1:10-15.

2. The preparation method of ethyl levulinate according to claim 1, characterized in that The steps include: S1, adding sugar alcohol and part of anhydrous ethanol into a dropping kettle and stirring evenly to obtain an anhydrous ethanol solution of sugar alcohol; S2, add ethyl levulinate, concentrated sulfuric acid and the remainder of anhydrous ethanol into the synthesis kettle and start stirring, heat the temperature in the kettle to 110-130° C., dropwise add the solution obtained in S1 into the synthesis kettle and keep warm for reaction; S3. After the reaction is completed, the temperature is cooled to room temperature, sulfuric acid is quenched with triethylamine, and ethanol is recovered and then distilled under reduced pressure to obtain ethyl levulinate.

3. The preparation method of ethyl levulinate according to claim 2, characterized in that, In the anhydrous ethanol solution of the sugar alcohol, the weight ratio of anhydrous ethanol to the sugar alcohol is 1-3:2-5.

4. The preparation method of ethyl levulinate according to claim 3, characterized in that, In the preparation process of ethyl levulinate, the raw materials used, by mass fraction, include 20%-30% sugar alcohol, 15%-20% anhydrous ethanol, 50%-60% ethyl levulinate, 0.1%-1% concentrated sulfuric acid and 0.2%-2% triethylamine.

5. The preparation method of ethyl levulinate according to claim 2, characterized in that, The anhydrous ethanol solution of the sugar alcohol is added dropwise within 2-3 hours.

6. The method for preparing ethyl levulinate according to claim 2, wherein During the heat preservation reaction process, the temperature is kept at 110° C.-130° C. for 2-3 hours.

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