Method for improving quality of rectified finished product of propyl acetate

Abstract

The invention provides a method for improving the quality of a propyl acetate rectification finished product. The method for improving the quality of the rectified finished product of propyl acetate comprises the following steps: L1, adding propyl alcohol and acetic acid into an esterification tower, and carrying out esterification reaction under the catalysis of a blend of a solid acid catalyst and an inorganic filler to obtain crude propyl acetate at the top of the esterification tower; l2, crude propyl acetate is output from a discharging port of the esterification tower and then enters a rectifying tower to be purified; wherein the middle part of the esterification tower is provided with an inorganic filler area, and the inorganic filler area is filled with a blend of a solid acid catalyst and an inorganic filler; the catalyst containing a large number of sulfonic acid groups is prepared by adding KH-560 modified silicon dioxide, sequentially reacting with polyethyleneimine and oxidized bamboo fibers and then treating with chlorosulfonic acid.

Description

Technical Field

[0001] This invention belongs to the field of propyl acetate production technology, and specifically relates to a method for improving the quality of propyl acetate distillation product. Background Technology

[0002] Propyl acetate is an important organic solvent and chemical intermediate, widely used in coatings, inks, pharmaceuticals, fragrances, and other fields. Its traditional industrial production mainly relies on the esterification reaction of acetic acid and propanol under the action of strong liquid acid catalysts such as concentrated sulfuric acid.

[0003] In existing technologies, the main production and distillation processes are as follows: Liquid acid catalysis: This is the most classic method, using concentrated sulfuric acid as a catalyst. Although this method has high catalytic activity and low cost, it has a series of inherent drawbacks: concentrated sulfuric acid is highly corrosive, requiring high-quality materials for the reaction equipment, increasing equipment investment and maintenance costs; after the reaction, it needs to be neutralized with alkali and washed with water to remove residual acid, generating a large amount of saline organic wastewater, which is environmentally unfriendly and has high subsequent treatment costs; the neutralization and washing processes may cause propyl acetate to hydrolyze, reducing product yield, and the introduction of water-soluble impurities increases the difficulty of subsequent distillation and purification.

[0004] Solid acid catalysis: To address the environmental pollution and equipment corrosion problems caused by liquid acids, solid acid catalysts have been applied to esterification reactions in recent years. These methods offer advantages such as easy catalyst separation, reusability, low corrosivity, and no acidic wastewater generation. However, existing solid acid catalysts still face some challenges when applied to the synthesis of propyl acetate: for example, some catalysts lack sufficient activity at the reaction temperature or are easily deactivated by moisture carried in the raw materials, resulting in low conversion rates; catalyst particles may cause increased bed pressure drop or insufficient contact with reactants, requiring improvement in mass transfer efficiency.

[0005] Distillation purification process: Regardless of whether the crude ester product is obtained through liquid or solid acid catalysis, it must be purified by distillation to obtain a high-purity final product. Current distillation processes typically treat the reaction and distillation as relatively independent unit operations. Trace amounts of catalyst residue, unreacted alcohols, water, and light component impurities such as ethers and olefins generated by side reactions may be present in the crude ester, posing challenges to the operational stability of the distillation column and the quality of the final product. In particular, the presence of trace amounts of moisture can form an azeotrope with propyl acetate, greatly increasing the difficulty of distillation separation. If not effectively removed, it will directly affect key quality indicators of the final product, such as acidity, moisture content, and color.

[0006] Existing technologies mainly suffer from the following problems: Environmental unfriendliness and high cost: Liquid acid catalysis generates large amounts of wastewater, placing significant environmental pressure on the environment. Catalyst performance bottlenecks: Existing solid acid catalysts may have insufficient activity, selectivity, or stability, affecting reaction efficiency and catalyst lifespan. Process integration and efficiency issues: The coupling between the reaction and distillation processes is not high; impurities generated in the reaction stage directly burden subsequent distillation stages, increasing energy consumption and purification difficulty. Difficulty in product quality control: Due to the above reasons, the propyl acetate product obtained from final distillation still has room for improvement in key quality indicators such as purity, acid value, and moisture content, making it difficult to consistently meet the requirements of high-end applications.

[0007] Therefore, developing a new method that can overcome the above-mentioned defects and significantly improve the quality of propyl acetate distillation products has important industrial application value. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention develops a method for improving the quality of propyl acetate distillation products. This method involves adding a catalyst containing a large number of sulfonic acid groups, prepared by reacting KH-560 modified silica with polyethyleneimine and oxidized bamboo fiber sequentially, followed by treatment with chlorosulfonic acid. This method combines highly efficient catalysis with distillation purification, significantly improving the efficiency and selectivity of the esterification reaction using a solid acid catalyst. It reduces the generation of byproducts and impurities at the source, effectively lowering the load and difficulty of subsequent distillation processes, ultimately achieving a stable and high-quality propyl acetate product. This method boasts advantages such as high catalytic efficiency, environmental friendliness, and high product purity.

[0009] The purpose of this invention is to provide a method for improving the quality of propyl acetate distillation product, comprising the following steps: L1. Propanol and acetic acid are added to the esterification tower, and the esterification reaction is carried out under the catalysis of a blend of solid acid catalyst and inorganic packing material. Crude propyl acetate is obtained at the top of the esterification tower. L2. Crude propyl acetate is discharged from the outlet of the esterification tower and then enters the distillation tower for purification. The esterification tower has an inorganic packing zone in the middle, which is filled with a blend of solid acid catalyst and inorganic packing. The solid acid catalyst is a product obtained by reacting polyethyleneimine-modified silica with oxidized bamboo fiber, then reacting it with polydopamine, and then treating it with chlorosulfonic acid. The inorganic filler is selected from ceramic fillers.

[0010] Furthermore, the mass ratio of the solid acid catalyst to the inorganic filler is 1-4:3-5.

[0011] Furthermore, the preparation method of the solid acid catalyst includes the following steps: S1. KH-560 modified silica is mixed with polyethyleneimine and heated to react, yielding polyethyleneimine modified silica; S2. Mix bamboo fiber and Na1O4, heat to react, and obtain oxidized bamboo fiber; S3. Mix polyethyleneimine-modified silica with oxidized bamboo fiber, react, then add polydopamine and continue the reaction to obtain an intermediate product; S4. Mix the intermediate product with chlorosulfonic acid and react at room temperature to obtain a solid acid catalyst.

[0012] Further, in step S1, the mass ratio of silicon dioxide to KH-560 is 2-5:0.5-1; In step S2, the mass ratio of bamboo fiber to Na1O4 is 1-2:3-7; In step S3, the mass ratio of the polyethyleneimine-modified silica, oxidized bamboo fiber, and polydopamine is 0.5-1:8-10:4-7. In step S4, the mass ratio of chlorosulfonic acid to intermediate product is 5-7:1-2.

[0013] Furthermore, the particle size of the silica is 5-30 μm.

[0014] Furthermore, the molecular weight of the polyethyleneimine is 600-15000 Da.

[0015] Furthermore, the lower part of the distillation column is provided with a separation section, which is connected to the bottom of the column below the separation section. The separation section is used to separate propyl propionate and propyl acetate, and the propyl acetate is collected in the separation section.

[0016] Furthermore, in step L1, the temperature of the esterification reaction is 75-105°C.

[0017] Furthermore, the molar ratio of propanol to acetic acid is 1.0-1.5:1.

[0018] Furthermore, the specific surface area of ​​the ceramic filler is 70-260 m². 2 / m 3 ; The porosity of the ceramic filler is 70-85%.

[0019] The beneficial effects of this invention are as follows: This invention improves catalytic efficiency, reduces byproduct formation, and enhances the quality of propyl acetate by filling the inorganic packing zone of the esterification tower with a blend of solid acid catalyst and inorganic packing material. First, silica is modified with KH560 to introduce epoxy groups, which then react with amino groups in polyethyleneimine to obtain polyethyleneimine-modified silica. Next, excess Na1O4 is used to oxidize bamboo fiber, resulting in oxidized bamboo fiber. This oxidized bamboo fiber then reacts with the polyethyleneimine-modified silica to introduce aldehyde-containing oxidized bamboo fiber. Polydopamine is then added to react with the aldehyde groups, followed by sulfonation with chlorosulfonic acid to obtain a solid acid catalyst containing high-density, uniformly loaded sulfonic acid groups.

[0020] On the one hand, by introducing oxidized bamboo fiber, polydopamine, and polyethyleneimine into the solid acid catalyst, a cross-linked network can be formed, which enhances the stability of the solid acid catalyst and prevents the structure of the solid acid catalyst from being destroyed at high temperatures. In addition, oxidized bamboo fiber introduces a large number of porous structures, which not only increases the specific surface area of ​​the solid acid catalyst, but also prevents the reaction raw materials from being blocked in the esterification tower, so that the reaction raw materials can be fully contacted, while promoting the diffusion of reaction raw materials and reaction products and inhibiting the occurrence of side reactions.

[0021] Secondly, the amino groups on the polydopamine chain can react with chlorosulfonic acid, thereby introducing sulfonic acid groups to catalyze the esterification reaction. This results in a uniform and dense distribution of the introduced sulfonic acid groups, promoting the formation of propyl acetate, reducing the amount of propyl propionate produced as a byproduct, reducing the generation of impurities in the crude ester from the source, alleviating the purification pressure in the separation section of the subsequent distillation column, and improving the purity of the extracted propyl acetate. Furthermore, within the distillation column, the temperature gradually decreases from the bottom to the top. Propyl acetate differs in boiling point from other byproducts. By setting a collection outlet in the separation section in the middle of the distillation column, a region with a relatively stable composition and the highest propyl acetate concentration can be formed within the column. Compared to the traditional method of collecting all the fraction from the top of the column and then performing secondary separation, this method can obtain high-purity propyl acetate in one step, simplifying the process and ensuring the excellent quality of the finished product directly from a physical separation level. Attached Figure Description

[0022] Figure 1 A schematic diagram of the esterification reaction apparatus in the method for improving the quality of propyl acetate distillation product is shown.

[0023] In the diagram: 110, esterification column; 111, inorganic packing zone; 112, distillation column; 113, column bottom; 114, separation section. Detailed Implementation

[0024] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided, but the present invention is not limited thereto.

[0025] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0026] Bamboo fiber, bamboo virgin fiber, purchased from Suzhou Lifeng Textile Co., Ltd., with an average linear density of 7.33 dtex.

[0027] Ceramic packing, ceramic Pall ring packing Dg25, with a specific surface area of ​​210 m². 2 / m 3 The porosity is 73%.

[0028] Polydopamine, catalog number 104785, particle size 100-200nm, purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.

[0029] KH-560, γ-glycidoxypropyltrimethoxysilane.

[0030] Polyethyleneimine, S24088, molecular weight 10000, was purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0031] Silica, FF-FXD-50, particle size 6-10μm, purchased from Hangzhou Jiayou New Materials Co., Ltd.

[0032] Example 1 A method for improving the quality of propyl acetate distillation product includes the following steps: L1. Under normal pressure and a reflux ratio of 1.8:1, propanol and acetic acid are added from the bottom of the esterification tower and the esterification reaction is carried out under the catalysis of a blend of solid acid catalyst and inorganic packing. Crude propyl acetate is obtained at the top of the esterification tower and the temperature of the bottom of the tower is controlled at 105℃. The molar ratio of propanol to acetic acid is 1.1:1. L2. Crude propyl acetate is discharged from the outlet of the esterification column and enters the distillation column through the inlet of the distillation column for purification. The separation section 114 is used to separate propyl propionate and propyl acetate. The propyl acetate is collected in the separation section 114, and the propyl propionate in the crude propyl acetate is enriched as a by-product in the bottom 113 of the column.

[0033] The esterification tower 110 has an inorganic packing zone 111 in the middle, which is filled with a blend of solid acid catalyst and inorganic packing. The esterification column 110 has a discharge port at its top, and the distillation column 112 has a feed port in its middle. The discharge port is connected to the feed port through a pipe. The distillation column has a separation section 114 at its bottom, which is connected to the bottom of the column 113 below the separation section 114. The separation section 114 is used to separate propyl propionate and propyl acetate, and the propyl acetate is collected in the separation section 114.

[0034] The inorganic filler is a ceramic filler; The mass ratio of the solid acid catalyst to the inorganic filler is 1:4; The preparation method of the solid acid catalyst includes the following steps: S1-1. Under nitrogen protection, silica and KH-560 were mixed in a mixture of ethanol and water with a volume ratio of 5:1 as solvent, heated to 115℃ and reacted for 24h. The mixture was then filtered, washed and dried to obtain KH-560 modified silica. The mass ratio of silicon dioxide to KH-560 is 3:0.5; S1-2. Under nitrogen protection, KH-560 modified silica was mixed with polyethyleneimine using a 1:1 volume ratio of ethanol and water as solvent, heated to 65°C and reacted for 12 hours. The mixture was then filtered, washed, and dried to obtain polyethyleneimine modified silica. The mass ratio of KH-560 modified silica to polyethyleneimine is 2:1; S2. Using water with a pH of 2.5 as a solvent, bamboo fiber and Na1O4 were mixed, heated to 40°C and reacted for 4 hours. After filtration, washing, and drying, oxidized bamboo fiber was obtained. The mass ratio of water, bamboo fiber, and Na1O4 is 65:1:3; S3. Polyethyleneimine-modified silica was added to water, then oxidized bamboo fiber was added and mixed. The mixture was reacted at 20°C for 8 hours, then polydopamine was added and the mixture was reacted at 20°C for another 10 hours. The mixture was washed to remove the solvent and obtain the intermediate product. The mass ratio of the polyethyleneimine-modified silica, oxidized bamboo fiber, polydopamine, and water is 0.8:8.5:6:200. S4. Chlorosulfonic acid, intermediate product and dichloromethane in a mass ratio of 5:1:150 were mixed and stirred at room temperature for 24 h. After washing and drying, a solid acid catalyst was obtained.

[0035] Example 2 A method for improving the quality of propyl acetate distillation product includes the following steps: L1. Under normal pressure and a reflux ratio of 2.0:1, propanol and acetic acid are added from the lower part of the esterification tower and the esterification reaction is carried out under the catalysis of a blend of solid acid catalyst and inorganic packing. Crude propyl acetate is obtained at the top of the esterification tower and the temperature of the bottom of the tower is controlled at 105℃. The molar ratio of propanol to acetic acid is 1.1:1. L2. Crude propyl acetate is discharged from the outlet of the esterification column and enters the distillation column through the inlet of the distillation column for purification. The separation section 114 is used to separate propyl propionate and propyl acetate. The propyl acetate is collected in the separation section 114, and the propyl propionate in the crude propyl acetate is enriched as a by-product in the bottom 113 of the column.

[0036] The esterification tower 110 has an inorganic packing zone 111 in the middle, which is filled with a blend of solid acid catalyst and inorganic packing. The esterification column 110 has a discharge port at its top, and the distillation column 112 has a feed port in its middle. The discharge port is connected to the feed port through a pipe. The distillation column has a separation section 114 at its bottom, which is connected to the bottom of the column 113 below the separation section 114. The separation section 114 is used to separate propyl propionate and propyl acetate, and the propyl acetate is collected in the separation section 114.

[0037] The inorganic filler is a ceramic filler; The mass ratio of the solid acid catalyst to the inorganic filler is 1:4; The preparation method of the solid acid catalyst includes the following steps: S1-1. Under nitrogen protection, silica and KH-560 were mixed in a mixture of ethanol and water with a volume ratio of 5:1 as solvent, heated to 115℃ and reacted for 24h. The mixture was then filtered, washed and dried to obtain KH-560 modified silica. The mass ratio of silicon dioxide to KH-560 is 3:0.5; S1-2. Under nitrogen protection, KH-560 modified silica was mixed with polyethyleneimine using a 1:1 volume ratio of ethanol and water as solvent, heated to 65°C and reacted for 12 hours. The mixture was then filtered, washed, and dried to obtain polyethyleneimine modified silica. The mass ratio of KH-560 modified silica to polyethyleneimine is 2:1; S2. Using water with a pH of 2.5 as a solvent, bamboo fiber and Na1O4 were mixed, heated to 40°C and reacted for 4 hours. After filtration, washing, and drying, oxidized bamboo fiber was obtained. The mass ratio of water, bamboo fiber, and Na1O4 is 65:1:3; S3. Polyethyleneimine-modified silica was added to water, then oxidized bamboo fiber was added and mixed. The mixture was reacted at 20°C for 8 hours, then polydopamine was added and the mixture was reacted at 20°C for another 10 hours. The mixture was washed to remove the solvent and obtain the intermediate product. The mass ratio of the polyethyleneimine-modified silica, oxidized bamboo fiber, polydopamine, and water is 0.8:9:5:200. S4. Chlorosulfonic acid, intermediate product and dichloromethane in a mass ratio of 5:1:150 were mixed and stirred at room temperature for 24 h. After washing and drying, a solid acid catalyst was obtained.

[0038] Example 3 A method for improving the quality of propyl acetate distillation product includes the following steps: L1. Under normal pressure and a reflux ratio of 2.2:1, propanol and acetic acid are added from the lower part of the esterification tower and the esterification reaction is carried out under the catalysis of a blend of solid acid catalyst and inorganic packing. Crude propyl acetate is obtained at the top of the esterification tower and the temperature of the tower bottom is controlled at 105℃. The molar ratio of propanol to acetic acid is 1.1:1. L2. Crude propyl acetate is discharged from the outlet of the esterification column and enters the distillation column through the inlet of the distillation column for purification. The separation section 114 is used to separate propyl propionate and propyl acetate. The propyl acetate is collected in the separation section 114, and the propyl propionate in the crude propyl acetate is enriched as a by-product in the bottom 113 of the column.

[0039] The esterification tower 110 has an inorganic packing zone 111 in the middle, which is filled with a blend of solid acid catalyst and inorganic packing. The esterification column 110 has a discharge port at its top, and the distillation column 112 has a feed port in its middle. The discharge port is connected to the feed port through a pipe. The distillation column has a separation section 114 at its bottom, which is connected to the bottom of the column 113 below the separation section 114. The separation section 114 is used to separate propyl propionate and propyl acetate, and the propyl acetate is collected in the separation section 114.

[0040] The inorganic filler is a ceramic filler; The mass ratio of the solid acid catalyst to the inorganic filler is 2:5; The preparation method of the solid acid catalyst includes the following steps: S1-1. Under nitrogen protection, silica and KH-560 were mixed in a mixture of ethanol and water with a volume ratio of 5:1 as solvent, heated to 115℃ and reacted for 24h. The mixture was then filtered, washed and dried to obtain KH-560 modified silica. The mass ratio of silicon dioxide to KH-560 is 4:0.8; S1-2. Under nitrogen protection, KH-560 modified silica was mixed with polyethyleneimine using a 1:1 volume ratio of ethanol and water as solvent, heated to 65°C and reacted for 12 hours. The mixture was then filtered, washed, and dried to obtain polyethyleneimine modified silica. The mass ratio of KH-560 modified silica to polyethyleneimine is 2:0.8; S2. Using water with a pH of 2.5 as a solvent, bamboo fiber and Na1O4 were mixed, heated to 40°C and reacted for 4 hours. After filtration, washing, and drying, oxidized bamboo fiber was obtained. The mass ratio of water, bamboo fiber, and Na1O4 is 70:2:5; S3. Polyethyleneimine-modified silica was added to water, then oxidized bamboo fiber was added and mixed. The mixture was reacted at 20°C for 8 hours, then polydopamine was added and the mixture was reacted at 20°C for another 10 hours. The mixture was washed to remove the solvent and obtain the intermediate product. The mass ratio of the polyethyleneimine-modified silica, oxidized bamboo fiber, polydopamine, and water is 0.8:10:5:200. S4. Chlorosulfonic acid, intermediate product and dichloromethane in a mass ratio of 5:1:150 were mixed and stirred at room temperature for 24 h. After washing and drying, a solid acid catalyst was obtained.

[0041] Comparative Example 1 The difference between this comparative example and Example 1 is that steps S2 and S3 are removed, and in step S4, polyethyleneimine-modified silica is used to replace an equal amount of intermediate product. All other components and preparation methods are the same.

[0042] Comparative Example 2 The difference between this comparative example and Example 1 is that step S1 is removed, and in step S3, polydopamine is used to replace an equal mass of polyethyleneimine-modified silica. All other components and preparation methods are the same.

[0043] Comparative Example 3 The difference between this comparative example and Example 1 is that the separation section in the distillation column is removed, and a conventional distillation column is used for distillation. All other components and preparation methods are the same.

[0044] Test Example 1 The content of each component in the crude propyl acetate product discharged from the top outlet of the esterification tower 110 in Example 1 and Comparative Examples 1-2 was detected.

[0045] The test results are shown in Table 1.

[0046] Table 1. Detection results of the content of each component in the crude propyl acetate product from the top outlet of the column in Examples 1 and Comparative Examples 1-2. As can be seen from the data comparison in Table 1, Example 1, due to the use of a highly efficient solid acid catalyst, has a higher catalytic efficiency and a higher content of propyl acetate, which can significantly reduce the content of other by-products.

[0047] Test Example 2 The content of each component in the separation section of the distillation column of Example 1 and Comparative Example 3 was detected.

[0048] The test results are shown in Table 2.

[0049] Table 2. Detection results of the content of each component of propyl acetate in the separation section of the distillation column of Example 1 and Comparative Example 3. As can be seen from the data comparison in Table 2, the propyl acetate content after distillation in Example 1 is higher than that in Comparative Example 3, while the propyl propionate and water content are lower than those in Comparative Example 3. This shows that the separation section can retain high-boiling-point propyl propionate, thus avoiding the propyl propionate from being extracted along with propyl acetate in conventional distillation.

[0050] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0051] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for improving the quality of a propyl acetate distillation product, characterized by, The method for improving the product quality of propyl acetate rectification comprises the following steps: L1. Propyl alcohol and acetic acid are added into an esterification tower to perform esterification reaction under the catalysis of a blend of solid acid catalyst and inorganic filler, and crude propyl acetate is obtained at the top of the esterification tower; L2. The crude propyl acetate is output from the discharge port of the esterification tower and then enters a rectification tower for purification treatment; The middle part of the esterification tower is provided with an inorganic filler area filled with a blend of solid acid catalyst and inorganic filler. The solid acid catalyst is a product obtained by reacting polyethyleneimine modified silicon dioxide and oxidized bamboo fiber, then reacting with polydopamine, and then treating with chlorosulfonic acid. The inorganic filler is selected from ceramic fillers.

2. The method of claim 1, wherein the improvement in the quality of the propyl acetate distillate product is characterized by, The mass ratio of the solid acid catalyst to the inorganic filler is 1-4:3-5.

3. The method of claim 1, wherein the improvement in the quality of the propyl acetate distillate product is characterized by, The preparation method of the solid acid catalyst comprises the following steps: S1. KH-560 modified silicon dioxide is mixed with polyethyleneimine and heated to react to obtain polyethyleneimine modified silicon dioxide; S2. Bamboo fiber is mixed with NalO4 and heated to react to obtain oxidized bamboo fiber; S3. Polyethyleneimine modified silicon dioxide is mixed with oxidized bamboo fiber to react, and then polydopamine is added to continue the reaction to obtain an intermediate product; S4. The intermediate product is mixed with chlorosulfonic acid to react at room temperature to obtain the solid acid catalyst.

4. The method according to claim 3, wherein In step S1, the mass ratio of the KH-560 modified silicon dioxide to the polyethyleneimine is 2-5:0.5-1; In step S2, the mass ratio of the bamboo fiber to NalO4 is 1-2:3-7; In step S3, the mass ratio of the polyethyleneimine modified silicon dioxide, the oxidized bamboo fiber and the polydopamine is 0.5-1:8-10:4-7; In step S4, the mass ratio of the chlorosulfonic acid to the intermediate product is 5-7:1-2.

5. The method according to claim 3, wherein The particle size of the silicon dioxide is 5-30 μm.

6. The method according to claim 3, wherein The molecular weight of the polyethyleneimine is 600-15000 Da.

7. The method of claim 1, wherein the improvement in the quality of the propyl acetate distillate product is characterized by, The lower part of the rectification tower is provided with a separation section which is communicated with a tower kettle below the separation section, and the separation section is used for separating propyl propionate and propyl acetate, and the propyl acetate is extracted in the separation section.

8. The method of claim 1, wherein the improvement in the quality of the propyl acetate distillate product is characterized by, In step L1, the temperature of the esterification reaction is 75-105℃.

9. The method of claim 1, wherein the improvement in the quality of the propyl acetate distillate product is characterized by, The molar ratio of the propyl alcohol to the acetic acid is 1.0-1.5:

1.

10. The method of claim 1, wherein the improvement in the quality of the propyl acetate distillate product is characterized by, The specific surface area of the ceramic filler is 70-260 m 2 / m 3 ; The porosity of the ceramic filler is 70-85%.

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