Levulinic acid production process capable of circularly applying acid solution

Abstract

The invention belongs to the technical field of production of chemicals, and particularly relates to a levulinic acid production process for circularly applying an acid solution. The levulinic acid production process comprises the following steps: adding hydrochloric acid into a hydrolysis kettle, then dropwise adding furfuryl alcohol, controlling the reaction temperature and the dropwise adding time, and after the reaction is finished, cooling to obtain a reaction solution; heating and concentrating the reaction liquid, condensing a gas phase, absorbing by a falling film absorber to obtain a hydrochloric acid solution, and continuing to hydrolyze and recycle; continuously distilling the concentrated solution under vacuum, carrying out hydrolysis reaction on the front fraction, and continuously crystallizing and centrifuging the collected fraction; and continuously melting the centrifuged solid to obtain a levulinic acid product. According to the levulinic acid production process capable of recycling the acid solution, hydrogen chloride is recycled, and the produced levulinic acid is high in purity and yield.

Description

Technical Field

[0001] The invention belongs to the technical field of production of chemical products, and in particular relates to a levulinic acid production process by circulating an acid solution. Background Art

[0002] Levulinic acid As a multifunctional compound containing carbonyl, α-hydrogen and carboxyl groups, it has a wide range of uses in organic synthesis, industry, agriculture and medicine. Its application areas include medicine, fragrance, pesticide, cosmetics and other industries. With the continuous growth of market demand, the production process of levulinic acid will continue to be improved and expanded.

[0003] At present, the processes for producing levulinic acid mainly include the following: (1) Direct biomass hydrolysis method, which uses cellulose, starch and other biomass as raw materials and performs hydrolysis reaction under acidic conditions to produce levulinic acid. However, a variety of by-products such as furfural and formic acid will be produced during the hydrolysis process, which increases the difficulty of product separation and purification. (2) Furfuryl alcohol catalytic hydrolysis method, which uses furfuryl alcohol as raw material and performs hydrolysis reaction under the action of catalyst to produce levulinic acid. However, the amount of hydrochloric acid used is large and cannot be recovered, and the product purity and yield are low. (3) Continuous catalytic hydrolysis method, which uses a continuous reactor and an automated control system to achieve continuous hydrolysis of biomass raw materials and continuous separation and purification of products. This method has the advantages of high production efficiency and large processing capacity. (4) Solid acid catalysis method, which uses solid acid catalysts instead of traditional liquid acid catalysts for hydrolysis reaction, reduces equipment corrosion and environmental pollution, but has high preparation costs. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art, provide a levulinic acid production process by recycling acid solution, recycle hydrogen chloride, and produce levulinic acid with high purity and high yield.

[0005] The process for producing levulinic acid by recycling an acid solution of the present invention comprises the following steps:

[0006] (1) Hydrolysis reaction: Add hydrochloric acid aqueous solution into a hydrolysis kettle, then add furfuryl alcohol dropwise, control the reaction temperature and the addition time, and after the reaction is completed, cool down to obtain a reaction solution;

[0007] (2) Concentration and deacidification: The reaction solution is heated and concentrated, and the gas phase is condensed and absorbed by a falling film absorber to become a hydrochloric acid solution, which then continues to enter step (1) for hydrolysis and recycling;

[0008] (3) The concentrated solution of step (2) is further distilled under vacuum, the front fraction is used as the mother liquor to continue to enter the hydrolysis reaction of step (1), the collected fraction is further crystallized and centrifuged, and the reaction solution after centrifugation is further entered into the hydrolysis reaction of step (1);

[0009] (4) The solid after centrifugation is further subjected to chemical reaction to obtain levulinic acid product.

[0010] In step (1), the reaction temperature is controlled to be 92-98°C, the dropwise addition time is 7-9h, and the reaction is continued for 8-10h after the dropwise addition is completed. The temperature is lowered to below 60°C after the reaction is completed.

[0011] The mass concentration of the hydrochloric acid aqueous solution in step (1) is 5.5-6.5%, the mass ratio of the hydrochloric acid aqueous solution to furfuryl alcohol is (1.1:1)-(1.2:1), and the molar ratio of furfuryl alcohol to water in the hydrochloric acid aqueous solution is 1:12-1:15.

[0012] The heating and concentration temperature in step (2) is 120-130° C., and the concentration time is 3-4 hours.

[0013] The hydrochloric acid solution in step (2) is adjusted to have a mass concentration of 5.5-6.5%.

[0014] In step (2), the gas phase condensation process is to condense in the condenser through the vacuum pipeline, and the condensate enters the receiving tank. The gas phase continues to enter the primary falling film absorber, and the primary falling film absorption liquid is continuously circulated by a circulation pump to absorb hydrogen chloride. The gas phase that is not completely absorbed continues to be sent to the secondary falling film absorber through the vacuum pipeline, and the secondary falling film absorption liquid is continuously circulated by a circulation pump to absorb hydrogen chloride. The gas phase that is not completely absorbed continues to be sent to the tertiary falling film absorber through the vacuum pipeline, and the tertiary falling film absorption liquid is continuously circulated by a circulation pump to absorb hydrogen chloride. The primary falling film absorber, the secondary falling film absorber, and the tertiary falling film absorber described above are all switching absorption under negative pressure.

[0015] The secondary falling film absorption liquid and the tertiary falling film absorption liquid are all pumped into the primary falling film absorption liquid. When the specific gravity of the primary falling film absorption liquid is 1.1-1.15, the absorption liquid is pumped into the acid preparation for standby use.

[0016] The distillation in step (3) collects the fraction with a temperature of 160-170°C.

[0017] The crystallization in step (3) is carried out by introducing salt water into the jacket of the crystallization kettle to cool and crystallize.

[0018] The liquid after centrifugation in step (4) is used as the mother liquor to continue entering the hydrolysis reaction in step (1).

[0019] Specifically, the levulinic acid production process by recycling the acid solution comprises the following steps:

[0020] (1) Hydrolysis reaction: Add hydrochloric acid (5.5-6.5%) of a certain mass concentration into a hydrolysis kettle, then add furfuryl alcohol dropwise, control the mass ratio of hydrochloric acid to furfuryl alcohol to be (1.1:1)-(1.2:1), and simultaneously add an appropriate amount of water so that the molar ratio of furfuryl alcohol to water is 1:12-1:15; during the reaction, strictly control the reaction temperature at 92-98°C, the dropwise addition time is 7-9h, and after the dropwise addition is completed, continue to keep the temperature for reaction for 8-10h; after the reaction is completed, cool to below 60°C to obtain a preliminary reaction solution.

[0021] (2) Concentration and deacidification: The reaction liquid is heated to 120-130°C and concentrated for 3-4 hours. During the concentration process, the gas phase condenses and enters the falling film absorption system through a vacuum pipeline. The system includes a primary, secondary, and tertiary falling film absorber. A circulating pump is used to continuously circulate the absorption liquid at each level to fully absorb the hydrogen chloride. The incompletely absorbed gas phase is continuously sent to the next absorber through a vacuum pipeline until the hydrogen chloride is completely absorbed. Finally, a hydrochloric acid solution that meets the requirements is obtained, and its mass concentration is adjusted to 5.5-6.5%, and it is reused in the hydrolysis reaction to achieve the recycling of hydrochloric acid.

[0022] (3) Distillation and reprocessing: The concentrated liquid is further distilled under vacuum conditions, and the fraction with a temperature of 160-170°C is collected. The front fraction is returned to the hydrolysis reaction as the mother liquor for further use. The collected fraction is further crystallized by passing brine through the jacket of the crystallization kettle to cool and crystallize. The crystallized solid is centrifuged to obtain the levulinic acid product. The liquid after centrifugation is also returned to the hydrolysis reaction as the mother liquor.

[0023] (4) Product collection and mother liquor recycling: The levulinic acid product obtained by centrifugation can be dried and then treated to obtain the final product. The liquid after centrifugation and the front fraction during distillation are returned to the hydrolysis reaction as mother liquor to maximize the utilization of materials.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The levulinic acid production process of the present invention realizes the recycling of hydrochloric acid by optimizing the steps of hydrolysis, concentration and deacidification, and distillation, thereby effectively reducing production costs and improving economic benefits.

[0026] (2) The levulinic acid production process of the present invention with circulating acid solution fully absorbs hydrogen chloride through a multi-stage falling film absorption system, thereby improving the recovery rate of hydrochloric acid and reducing environmental pollution. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with specific embodiments.

[0028] The raw materials used in the following examples and comparative examples are all commercial products.

[0029] Example 1

[0030] The levulinic acid production process by recycling the acid solution comprises the following steps:

[0031] (1) Hydrolysis reaction: 500 kg of 6% hydrochloric acid was added to the hydrolysis kettle, followed by dropwise addition of 450 kg of furfuryl alcohol and an appropriate amount of water so that the molar ratio of furfuryl alcohol to water was 1:13. The reaction temperature was controlled at 95° C. and the dropwise addition time was 8 h. After the dropwise addition was completed, the reaction was continued at a temperature of 9 h. After the reaction was completed, the temperature was lowered to 55° C. to obtain a preliminary reaction solution.

[0032] (2) Concentration and deacidification: The reaction liquid is heated to 125°C and concentrated for 3.5 hours. During the concentration process, the gas phase is condensed and enters the falling film absorption system through a vacuum pipeline. The system includes a primary, secondary, and tertiary falling film absorber, and a circulating pump is used to continuously circulate the absorption liquid at each level to fully absorb the hydrogen chloride. The incompletely absorbed gas phase continues to be sent to the next absorber through a vacuum pipeline until the hydrogen chloride is completely absorbed. Finally, a hydrochloric acid solution that meets the requirements is obtained, and its mass concentration is adjusted to 6%, and it is reused in the hydrolysis reaction to achieve the recycling of hydrochloric acid.

[0033] (3) Distillation and reprocessing: The concentrated liquid is further distilled under vacuum conditions, and the fraction with a temperature of 160-170°C is collected. The front fraction is returned to the hydrolysis reaction as the mother liquor for further use. The collected fraction is further crystallized by passing brine through the jacket of the crystallization kettle to cool and crystallize. The crystallized solid is centrifuged to obtain the levulinic acid product. The liquid after centrifugation is also returned to the hydrolysis reaction as the mother liquor.

[0034] (4) Product collection and mother liquor recycling: The levulinic acid product obtained by centrifugation can be dried and then treated to obtain the final product levulinic acid. After gas phase detection, its purity is 99.5% and the yield is 87%. The liquid after centrifugation and the front fraction during the distillation process are returned to the hydrolysis reaction as mother liquor to maximize the utilization of materials.

[0035] Example 2

[0036] The levulinic acid production process by recycling the acid solution comprises the following steps:

[0037] (1) Hydrolysis reaction: 500 kg of 5.5% hydrochloric acid was added to the hydrolysis kettle, followed by dropwise addition of 450 kg of furfuryl alcohol and an appropriate amount of water so that the molar ratio of furfuryl alcohol to water was 1:12. The reaction temperature was controlled at 92° C. and the dropwise addition time was 9 h. After the dropwise addition was completed, the reaction was continued at the temperature for 10 h. After the reaction was completed, the temperature was lowered to 50° C. to obtain a preliminary reaction solution.

[0038] (2) Concentration and deacidification: The reaction liquid is heated to 120°C and concentrated for 4 hours. During the concentration process, the gas phase is condensed and enters the falling film absorption system through a vacuum pipeline. The system includes a primary, secondary, and tertiary falling film absorber, and a circulating pump is used to continuously circulate the absorption liquid at each level to fully absorb the hydrogen chloride. The incompletely absorbed gas phase continues to be sent to the next absorber through a vacuum pipeline until the hydrogen chloride is completely absorbed. Finally, a hydrochloric acid solution that meets the requirements is obtained, and its mass concentration is adjusted to 5.5%, and it is reused in the hydrolysis reaction to achieve the recycling of hydrochloric acid.

[0039] (3) Distillation and reprocessing: The concentrated liquid is further distilled under vacuum conditions, and the fraction with a temperature of 160-170°C is collected. The front fraction is returned to the hydrolysis reaction as the mother liquor for further use. The collected fraction is further crystallized by passing brine through the jacket of the crystallization kettle to cool and crystallize. The crystallized solid is centrifuged to obtain the levulinic acid product. The liquid after centrifugation is also returned to the hydrolysis reaction as the mother liquor.

[0040] (4) Product collection and mother liquor recycling: The levulinic acid product obtained by centrifugation can be dried and then treated to obtain the final product levulinic acid. After gas phase detection, its purity is 99.3% and the yield is 85%. The liquid after centrifugation and the front fraction during distillation are returned to the hydrolysis reaction as mother liquor to maximize the utilization of materials.

[0041] Example 3

[0042] The levulinic acid production process by recycling the acid solution comprises the following steps:

[0043] (1) Hydrolysis reaction: 500 kg of 6.5% hydrochloric acid was added to the hydrolysis kettle, followed by dropwise addition of 450 kg of furfuryl alcohol and an appropriate amount of water so that the molar ratio of furfuryl alcohol to water was 1:15. The reaction temperature was controlled at 98° C. and the dropwise addition time was 7 h. After the dropwise addition was completed, the reaction was continued at a temperature of 8 h. After the reaction was completed, the temperature was lowered to 55° C. to obtain a preliminary reaction solution.

[0044] (2) Concentration and deacidification: The reaction liquid is heated to 130°C and concentrated for 3 hours. During the concentration process, the gas phase is condensed and enters the falling film absorption system through a vacuum pipeline. The system includes a primary, secondary, and tertiary falling film absorber, and a circulating pump is used to continuously circulate the absorption liquid at each level to fully absorb the hydrogen chloride. The incompletely absorbed gas phase continues to be sent to the next absorber through a vacuum pipeline until the hydrogen chloride is completely absorbed. Finally, a hydrochloric acid solution that meets the requirements is obtained, and its mass concentration is adjusted to 6%, and it is reused in the hydrolysis reaction to achieve the recycling of hydrochloric acid.

[0045] (3) Distillation and reprocessing: The concentrated liquid is further distilled under vacuum conditions, and the fraction with a temperature of 160-170°C is collected. The front fraction is returned to the hydrolysis reaction as the mother liquor for further use. The collected fraction is further crystallized by passing brine through the jacket of the crystallization kettle to cool and crystallize. The crystallized solid is centrifuged to obtain the levulinic acid product. The liquid after centrifugation is also returned to the hydrolysis reaction as the mother liquor.

[0046] (4) Product collection and mother liquor recycling: The levulinic acid product obtained by centrifugation can be dried and then treated to obtain the final product levulinic acid. After gas phase detection, its purity is 99.2% and the yield is 86%. The liquid after centrifugation and the front fraction during distillation are returned to the hydrolysis reaction as mother liquor to maximize the utilization of materials.

[0047] Of course, the above contents are only preferred embodiments of the present invention and cannot be considered to limit the scope of the embodiments of the present invention. The present invention is not limited to the above examples, and equal changes and improvements made by ordinary technicians in the technical field within the essential scope of the present invention should all fall within the scope of the patent coverage of the present invention.

Claims

1. A process for producing levulinic acid by recycling an acid solution, characterized in that: The following steps are involved: (1) Hydrolysis reaction: Add hydrochloric acid aqueous solution into a hydrolysis kettle, then add furfuryl alcohol dropwise, control the reaction temperature and the addition time, and after the reaction is completed, cool down to obtain a reaction solution; (2) Concentration and deacidification: The reaction solution is heated and concentrated, and the gas phase is condensed and absorbed by a falling film absorber to become a hydrochloric acid solution, which then continues to enter step (1) for hydrolysis and recycling; (3) The concentrated solution of step (2) is further distilled under vacuum, the front fraction is used as the mother liquor to continue to enter the hydrolysis reaction of step (1), the collected fraction is further crystallized and centrifuged, and the reaction solution after centrifugation is further entered into the hydrolysis reaction of step (1); (4) The solid after centrifugation is further subjected to chemical reaction to obtain levulinic acid product.

2. The process for producing levulinic acid by recycling acid solution according to claim 1, characterized in that: In step (1), the reaction temperature is controlled to be 92-98°C, the dropwise addition time is 7-9h, and the reaction is continued for 8-10h after the dropwise addition is completed. The temperature is lowered to below 60°C after the reaction is completed.

3. The process for producing levulinic acid by recycling acid solution according to claim 1, characterized in that: The mass concentration of the hydrochloric acid aqueous solution in step (1) is 5.5-6.5%, the mass ratio of the hydrochloric acid aqueous solution to furfuryl alcohol is (1.1:1)-(1.2:1), and the molar ratio of furfuryl alcohol to water in the hydrochloric acid aqueous solution is 1:12-1:

15.

4. The process for producing levulinic acid by recycling acid solution according to claim 1, characterized in that: The heating and concentration temperature in step (2) is 120-130° C., and the concentration time is 3-4 hours.

5. The process for producing levulinic acid by recycling acid solution according to claim 1, characterized in that: The hydrochloric acid solution in step (2) is adjusted to have a mass concentration of 5.5-6.5%.

6. The process for producing levulinic acid by recycling acid solution according to claim 1, characterized in that: In step (2), the gas phase condensation process is to condense in the condenser through the vacuum pipeline, and the condensate enters the receiving tank. The gas phase continues to enter the primary falling film absorber, and the primary falling film absorption liquid is continuously circulated by a circulation pump to absorb hydrogen chloride. The gas phase that is not completely absorbed continues to be sent to the secondary falling film absorber through the vacuum pipeline, and the secondary falling film absorption liquid is continuously circulated by a circulation pump to absorb hydrogen chloride. The gas phase that is not completely absorbed continues to be sent to the tertiary falling film absorber through the vacuum pipeline, and the tertiary falling film absorption liquid is continuously circulated by a circulation pump to absorb hydrogen chloride. The primary falling film absorber, the secondary falling film absorber, and the tertiary falling film absorber described above are all switching absorption under negative pressure.

7. The process for producing levulinic acid by recycling acid solution according to claim 6, characterized in that: The secondary falling film absorption liquid and the tertiary falling film absorption liquid are all pumped into the primary falling film absorption liquid. When the specific gravity of the primary falling film absorption liquid is 1.1-1.15, the absorption liquid is pumped into the acid preparation for standby use.

8. The process for producing levulinic acid by recycling acid solution according to claim 1, characterized in that: The distillation in step (3) collects the fraction with a temperature of 160-170°C.

9. The process for producing levulinic acid by recycling acid solution according to claim 1, characterized in that: The crystallization in step (3) is carried out by introducing salt water into the jacket of the crystallization kettle to cool and crystallize.

10. The process for producing levulinic acid by recycling acid solution according to claim 1, characterized in that: The liquid after centrifugation in step (4) is used as the mother liquor to continue entering the hydrolysis reaction in step (1).