Method and system for preparing formic acid by catalyzing hydrolysis of methyl formate through ionic liquid

Abstract

According to the method and system for preparing formic acid by catalyzing hydrolysis of methyl formate through the ionic liquid, in the system and method, the reversible reaction of hydrolysis of methyl formate can be prevented through the basic ionic liquid, hydrolysis of methyl formate into methyl alcohol and formic acid is promoted, and the conversion rate of methyl formate is increased; meanwhile, the re-esterification reaction of the hydrolysis product formic acid and methanol can be inhibited, so that the concentration of formic acid in the hydrolysis product is improved, the energy consumption during formic acid concentration is reduced, and more favorable conditions are provided for subsequent formic acid concentration. In addition, the alkaline ionic liquid can break azeotropy of formic acid and water so as to realize efficient hydrolysis and product separation. In addition, through reasonable backflow and cyclic utilization of materials among the towers, unnecessary multiple rectification separation is avoided, energy consumption is reduced, and production efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of formic acid preparation technology, and relates to a method and system for producing formic acid by hydrolysis of methyl formate catalyzed by ionic liquid. Background Technology

[0002] Formic acid, as an important chemical raw material, is widely used in many fields such as textiles, leather, rubber processing, chemical industry, pharmaceuticals, pesticide industry and food industry.

[0003] Currently, formic acid is typically prepared by hydrolyzing methyl formate. Due to the low equilibrium constant of methyl formate hydrolysis, the formic acid and methanol generated during hydrolysis readily undergo re-esterification during distillation, regenerating methyl formate, resulting in a re-esterification rate >10%. Simultaneously, the formic acid product inhibits the forward reaction, leading to a conversion rate of less than 25%. Furthermore, the hydrolysis product requires multiple distillation separations to obtain formic acid, and the azeotropic effect of formic acid and water increases separation energy consumption and reduces production capacity.

[0004] For example, CN1086508A discloses a method for continuously hydrolyzing methyl formate at 80-100℃ in a displacement reactor filled with a strongly acidic sulfonic acid-based cation exchange resin as a heterogeneous catalyst, and then sending the entire mixture to a subsequent negative pressure separation tower to separate crude formic acid. While this invention reduces the water-to-ester ratio, improves the conversion rate, and allows for continuous production, the reaction mixture needs to be separated in a quaternary separation tower, which cannot effectively prevent the re-esterification of methanol and formic acid, and the investment is relatively high. Another example is CN106883121B, which discloses a method for preparing anhydrous formic acid by hydrolyzing methyl formate using a partitioned reactive distillation column, allowing for simultaneous hydrolysis and separation of methyl formate in a single column, simplifying the operation. However, partitioned distillation columns have extremely demanding operating conditions and have not yet been widely used in industry. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for the hydrolysis of methyl formate to formic acid using ionic liquid catalysis, in order to solve the problems of high re-esterification rate, low conversion rate and high energy consumption in existing preparation methods.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This application provides a method for producing formic acid by hydrolyzing methyl formate using an ionic liquid, the method comprising: S01: Methyl formate and a basic ionic liquid are contacted countercurrently in a hydrolysis distillation column and undergo a hydrolysis reaction. A methyl formate / methanol mixture is obtained at the top of the column, and a formic acid / basic ionic liquid mixture is obtained at the bottom of the column. The basic ionic liquid includes imidazole ionic liquids or pyridine ionic liquids.

[0007] A basic ionic liquid with a mass concentration of 20-30% is introduced into the hydrolysis distillation column from the upper section. Methyl formate, obtained from the carbonylation reaction of CO and methanol, is vaporized in a vaporizer and then introduced into the hydrolysis distillation column from the lower section. Under conditions of 65-75℃ and 0.05-0.12 MPa, the basic ionic liquid and methyl formate undergo counter-current contact and hydrolysis in the hydrolysis distillation column. This allows the basic ionic liquid to inhibit the reversible hydrolysis of methyl formate, promote its hydrolysis into methanol and formic acid, and simultaneously suppress the re-esterification reaction of the hydrolysis products formic acid and methanol, thereby increasing the concentration of formic acid in the hydrolysis products. The volume ratio of methyl formate to water is 1-1.5:2.

[0008] The top of the hydrolysis distillation column yields a methyl formate / methanol mixture, which is then discharged into a methanol distillation column for further distillation. The bottom of the hydrolysis distillation column yields a formic acid / alkaline ionic liquid mixture with a formic acid volume concentration of 50-60%, which is discharged into the first distillation column for further distillation.

[0009] In this application, the basic ionic liquid includes imidazole ionic liquids or pyridine ionic liquids, wherein the imidazole ionic liquid includes 1-butyl-3-methylimidazolium hydroxide ionic liquid, and the pyridine ionic liquid includes 1-butylpyridine tetrafluoroborate or 1-butylpyridine hydrogen sulfate.

[0010] S02: The methyl formate / methanol mixture is distilled in a methanol distillation column to obtain methyl formate at the top of the column and methanol at the bottom.

[0011] Under conditions of 60-70℃ and 0.005-0.015Mpa, the methyl formate / methanol mixture is distilled in a methanol distillation column. The methyl formate obtained from the top of the column is returned to the hydrolysis distillation column for re-hydrolysis reaction; the methanol obtained from the bottom of the column is returned to the carbonylation reactor.

[0012] S03: The formic acid / basic ionic liquid mixture is distilled in a first distillation column, and water is obtained at the top of the column, while a formic acid / basic ionic liquid concentrate is obtained at the bottom of the column.

[0013] At a temperature of 115-125℃ and a pressure of 0.2-0.3 MPa, a formic acid / basic ionic liquid mixture is distilled in a first distillation column. Because the basic ionic liquid can break the azeotropic reaction between formic acid and water, water is obtained at the top of the first distillation column and returned to the hydrolysis distillation column; a formic acid / basic ionic liquid concentrate with a formic acid volume concentration of 80-85% is obtained at the top of the column, and this concentrate is discharged into the second distillation column.

[0014] S04: The formic acid / alkaline ionic liquid concentrate is distilled in a second distillation column to obtain formic acid at the top of the column and alkaline ionic liquid at the bottom.

[0015] At a temperature of 60-70℃ and a pressure of -0.07 to -0.09 MPa, the formic acid / alkaline ionic liquid concentrate is distilled in a second distillation column. Formic acid with a volume concentration of 85-95% is obtained at the top of the column, and alkaline ionic liquid is obtained at the bottom of the column. This alkaline ionic liquid is returned to the hydrolysis distillation column for recycling.

[0016] This application also provides a system for the hydrolysis of methyl formate to formic acid using ionic liquid catalysis. The system includes a hydrolysis distillation column, an alkaline ionic liquid storage tank, a methyl formate storage tank, a methanol distillation column, and a first distillation column, the first distillation column being connected to a second distillation column, and the methanol distillation column being connected to the methyl formate storage tank.

[0017] The present invention has the following beneficial effects: (1) The alkaline ionic liquid in this application can prevent the reversible hydrolysis of methyl formate, promote the hydrolysis of methyl formate into methanol and formic acid, and improve the conversion rate of methyl formate; at the same time, it can also inhibit the re-esterification reaction of hydrolysis products formic acid and methanol, thereby increasing the concentration of formic acid in the hydrolysis products, reducing the energy consumption when concentrating formic acid, and providing more favorable conditions for subsequent concentration of formic acid.

[0018] (2) Alkaline ionic liquids can prevent the reversible hydrolysis of methyl formate during the entire reaction and separation process, and can break the azeotropic reaction between formic acid and water to achieve efficient hydrolysis and product separation.

[0019] (3) By rationally refluxing and recycling materials between towers, unnecessary multiple distillation separations are avoided, energy consumption is reduced, and production efficiency is improved. At the same time, equipment investment and operating costs are reduced, resulting in good economic benefits and promising industrial application prospects. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the system for producing formic acid by hydrolysis of methyl formate using ionic liquids, as provided in the embodiments of this application. Symbolic representation: 1-Alkaline ionic liquid storage tank, 2-Methyl formate storage tank, 3-Hydrolysis distillation column, 4-Methanol distillation column, 5-First distillation column, 6-Second distillation column. Detailed Implementation

[0021] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0022] Example 1 This application provides a system for the hydrolysis of methyl formate to formic acid using an ionic liquid catalytic method. The system mainly includes an alkaline ionic liquid storage tank 1, a methyl formate storage tank 2, a hydrolysis distillation column 3, a methanol distillation column 4, a first distillation column 5, and a second distillation column 6, as shown in the attached diagram. Figure 1 As shown.

[0023] The alkaline ionic liquid storage tank 1 is a component for storing alkaline ionic liquids with a mass concentration of 20-30%. In the embodiments of this application, the alkaline ionic liquid includes one of amine ionic liquids, imidazole ionic liquids, or pyridine ionic liquids. Specifically, the amine ionic liquid includes one or more of these, the imidazole ionic liquid includes one or more of 1-butyl-3-methylimidazolium hydroxide ionic liquid, and the pyridine ionic liquid includes one or more of these.

[0024] Methyl formate storage tank 2 is a component for storing methyl formate obtained by the carbonylation reaction of CO and methanol. The methyl formate is vaporized into methyl formate gas by a vaporizer and then enters the hydrolysis distillation column 3.

[0025] The hydrolysis distillation column 3 is a component where the alkaline ionic liquid and methyl formate undergo a hydrolysis reaction. It is connected to both the alkaline ionic liquid storage tank 1 and the methyl formate storage tank 2, facilitating the transport of both substances. In the hydrolysis distillation column 3, the alkaline ionic liquid and methyl formate come into counter-current contact and undergo a hydrolysis reaction. The alkaline ionic liquid prevents the reversible hydrolysis of methyl formate, promotes its hydrolysis into methanol and formic acid, and simultaneously inhibits the re-esterification reaction of the hydrolysis products formic acid and methanol, thus increasing the concentration of formic acid in the hydrolysis products. A methyl formate / methanol mixture is obtained at the top of the hydrolysis distillation column 3 and is discharged into the methanol distillation column 4 for further distillation. A formic acid / alkaline ionic liquid mixture with a formic acid volume concentration of 50-60% is obtained at the bottom of the hydrolysis distillation column 3 and is discharged into the first distillation column 5 for further distillation.

[0026] Methanol distillation column 4 is a component for distilling methyl formate / methanol mixtures. Under conditions of 60-70℃ and 0.005-0.015 MPa, the methyl formate / methanol mixture undergoes distillation in methanol distillation column 4. The methyl formate obtained from the top of the column is returned to the methyl formate storage tank 2, and then fed into the hydrolysis distillation column 3 for further hydrolysis. The methanol obtained from the bottom of the column is returned to the carbonylation reactor.

[0027] The first distillation column 5 is a component for distilling a formic acid / basic ionic liquid mixture. Under conditions of 115-125℃ and 0.2-0.3 MPa, the formic acid / basic ionic liquid mixture is distilled in the first distillation column 5. Since the basic ionic liquid can break the azeotropic reaction between formic acid and water, water is obtained at the top of the first distillation column 5 and returned to the hydrolysis distillation column 3; a formic acid / basic ionic liquid concentrate with a formic acid volume concentration of 80-85% is obtained at the top of the column, and this concentrate is discharged into the second distillation column 6.

[0028] The second distillation column 6 is a component for distilling formic acid / basic ionic liquid concentrate, and it is connected to the first distillation column 5. Under conditions of 60-70℃ and -0.07-0.09 MPa, the formic acid / basic ionic liquid concentrate is distilled in the second distillation column. Formic acid with a volume concentration of 85-95% is obtained at the top of the column, and basic ionic liquid is obtained at the bottom of the column. This basic ionic liquid is returned to the hydrolysis distillation column for recycling.

[0029] In this embodiment, feed pumps are provided in the material outflow direction of the alkaline ionic liquid storage tank 1, the methyl formate storage tank 2, the hydrolysis distillation column 3, the methanol distillation column 4, the first distillation column 5, and the second distillation column 6 to allow the material to enter the next connected component. Additionally, reboilers are provided at the bottom of the hydrolysis distillation column 3, the methanol distillation column 4, the first distillation column 5, and the second distillation column 6 to heat each distillation column to a preset temperature.

[0030] Furthermore, the tops of the hydrolysis distillation column 3, the methanol distillation column 4, the first distillation column 5, and the second distillation column 6 are all equipped with reflux tanks and reflux pumps to allow the top products of the columns to be refluxed.

[0031] Example 2 This application provides a method for producing formic acid by hydrolyzing methyl formate using an ionic liquid, the method comprising: S201: 1-Butyl-3-methylimidazolium hydroxide ionic liquid is prepared to a mass concentration of 20% and enters the hydrolysis distillation column from the upper section. Methyl formate obtained from the carbonylation reaction of CO and methanol is vaporized in a vaporizer and then enters the hydrolysis distillation column from the lower section. Under the conditions of 65℃ and 0.12 MPa, the alkaline ionic liquid and methyl formate are contacted in countercurrents in the hydrolysis distillation column at a volume ratio of methyl formate to water of 1.5:2 and undergo a hydrolysis reaction. A methyl formate / methanol mixture is obtained at the top of the column, and a formic acid / alkaline ionic liquid mixture with a volume concentration of 50% is obtained at the bottom of the column.

[0032] S202: Under the conditions of 60℃ and 0.015Mpa, the methyl formate / methanol mixture is distilled in a methanol distillation column. The methyl formate obtained from the top of the column is returned to the hydrolysis distillation column for re-hydrolysis reaction; the methanol obtained from the bottom of the column is returned to the carbonylation reactor.

[0033] S203: Under the conditions of temperature 115℃ and pressure 0.3Mpa, the formic acid / basic ionic liquid mixture is distilled in the first distillation column. Water is obtained at the top of the column and returned to the hydrolysis distillation column. A formic acid / basic ionic liquid concentrate with a formic acid volume concentration of 80% is obtained at the top of the column, and the concentrate is discharged into the second distillation column.

[0034] S204: Under conditions of 60℃ and -0.09 MPa, formic acid / alkaline ionic liquid concentrate is distilled in a second distillation column. Formic acid with a volume concentration of 85% is obtained at the top of the column, while an alkaline ionic liquid is obtained at the bottom. This alkaline ionic liquid is returned to the hydrolysis distillation column for recycling. Testing shows that the conversion rate of methyl formate reaches 35%, and the purity of the final formic acid product meets relevant industrial standards.

[0035] Example 3 This application provides a method for producing formic acid by catalytic hydrolysis of methyl formate using an ionic liquid. The method is the same as in Example 1, except that the alkaline ionic liquid used is 1-butylpyridine tetrafluoroborate with a concentration of 25%; the volume concentration of formic acid in the formic acid / alkaline ionic liquid mixture is 55%. Testing shows that the conversion rate of methyl formate reaches 40%, and the purity of the final formic acid product is 90%, which meets relevant industrial standards.

[0036] Example 4 This application provides a method for producing formic acid by catalytic hydrolysis of methyl formate using an ionic liquid. The method is the same as in Example 1, except that the alkaline ionic liquid used is 1-butylpyridine hydrogen sulfate at a concentration of 30%; and the volume concentration of formic acid in the formic acid / alkaline ionic liquid mixture is 60%. Testing showed that the conversion rate of methyl formate reached 41%, and the purity of the final formic acid product was 95%, meeting relevant industrial standards.

[0037] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for producing formic acid by hydrolyzing methyl formate using an ionic liquid catalysis, characterized in that, include: Methyl formate and a basic ionic liquid are brought into countercurrent contact in a hydrolysis distillation column and undergo a hydrolysis reaction. A methyl formate / methanol mixture is obtained at the top of the column, and a formic acid / basic ionic liquid mixture is obtained at the bottom of the column. The basic ionic liquid includes imidazole ionic liquids or pyridine ionic liquids. The methyl formate / methanol mixture is distilled in a methanol distillation column to obtain methyl formate at the top of the column and methanol at the bottom of the column. The formic acid / basic ionic liquid mixture is distilled in a first distillation column, with water obtained at the top and a formic acid / basic ionic liquid concentrate obtained at the bottom. The formic acid / basic ionic liquid concentrate is distilled in a second distillation column, yielding formic acid at the top and basic ionic liquid at the bottom.

2. The method for producing formic acid by hydrolysis of methyl formate catalyzed by ionic liquid according to claim 1, characterized in that, The imidazole ionic liquid includes 1-butyl-3-methylimidazolium hydroxide ionic liquid, and the pyridine ionic liquid includes 1-butylpyridine tetrafluoroborate or 1-butylpyridine hydrogen sulfate.

3. The method for producing formic acid by hydrolysis of methyl formate catalyzed by ionic liquid according to claim 1, characterized in that, The mass concentration of the alkaline ionic liquid is 20-30%.

4. The method for producing formic acid by hydrolysis of methyl formate catalyzed by ionic liquid according to claim 1, characterized in that, In the methanol distillation column, the volume ratio of methyl formate to water is 1-1.5:

2.

5. The method for producing formic acid by hydrolysis of methyl formate catalyzed by ionic liquid according to claim 1, characterized in that, The formic acid / basic ionic liquid mixture has a volume concentration of 50-60%, the formic acid / basic ionic liquid concentrate has a volume concentration of 80-85%, and the formic acid has a volume concentration of 85-95%.

6. The method for producing formic acid by hydrolysis of methyl formate catalyzed by ionic liquid according to claim 1, characterized in that, The temperature of the hydrolysis distillation column is 65-75℃ and the pressure is 0.05-0.12Mpa.

7. The method for producing formic acid by hydrolysis of methyl formate catalyzed by ionic liquid according to claim 1, characterized in that, The methanol distillation column has a temperature of 60-70℃ and a pressure of 0.005-0.015 MPa.

8. The method for producing formic acid by hydrolysis of methyl formate catalyzed by ionic liquid according to claim 1, characterized in that, The temperature of the first distillation column is 115-125℃ and the pressure is 0.2-0.3 MPa.

9. The method for producing formic acid by hydrolysis of methyl formate catalyzed by ionic liquid according to claim 1, characterized in that, The temperature of the second distillation column is 60-70℃ and the pressure is -0.07 to -0.09 MPa.

10. A system for the hydrolysis of methyl formate to formic acid catalyzed by ionic liquid, characterized in that, It includes a hydrolysis distillation column (3), an alkaline ionic liquid storage tank (1) connected to the hydrolysis distillation column (3), a methyl formate storage tank (2), a methanol distillation column (4), and a first distillation column (5). The first distillation column (5) is also connected to a second distillation column (6), and the methanol distillation column (4) is also connected to the methyl formate storage tank (2).

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