Catalytic hydrolysis rectification system and method for methyl propionate
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-12-17
- Publication Date
- 2026-06-19
Smart Images
Figure CN122230359A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a catalytic hydrolysis distillation system and method for methyl propionate, specifically, to a heterogeneous catalytic distillation hydrolysis process for methyl propionate, and the catalytic distillation equipment used in the hydrolysis process, in the field of fine chemical preparation technology. Background Technology
[0002] Propionic acid is an important fine chemical product and raw material for organic synthesis, widely used in agriculture, textiles, food, and pharmaceutical industries. Particularly in the application of food preservatives, among the three most widely used food preservatives—benzoic acid, propionic acid, and sorbic acid—propionic acid is recognized as the most economical, safe, and effective. Propionic acid and its propionate salts have good inhibitory effects on Gram-negative bacteria, Aspergillus flavus, certain aerobic Bacillus species, and Salmonella. Their mechanism of action involves creating a high osmotic pressure outside the cells of molds or bacteria, causing dehydration and loss of reproductive capacity within the mold cells; or penetrating the cell walls of molds, inhibiting intracellular enzyme activity, and thus preventing mold growth. Furthermore, propionic acid and its propionate salts are harmless to humans and animals, and are therefore widely used in the preservation of grains, feed, and food.
[0003] Currently, the main hydrolysis method for methyl propionate both domestically and internationally is the fixed-bed hydrolysis process using cation exchange resin. Its disadvantages include: low single-pass hydrolysis rate (23%–25% when the water-to-ester ratio is 0.9 / 1.0 moles), resulting in a propionic acid concentration of approximately 10%–20% in the hydrolysate and an acid-to-water weight ratio of approximately 1.3); the low hydrolysis rate necessitates the recycling of a large amount of unhydrolyzed methyl propionate, leading to bulky equipment and high energy consumption; and the presence of azeotropes in the hydrolysate complicates the separation process. Summary of the Invention
[0004] To overcome the shortcomings of existing hydrolysis processes and apparatus, the present invention aims to provide a method and apparatus for heterogeneous catalytic distillation hydrolysis of methyl propionate. This process and apparatus improve the hydrolysis rate to achieve any desired ester hydrolysis rate within the range of 35% to 98%, yielding a high concentration of propionic acid while simultaneously recovering methanol.
[0005] The technical solution adopted by this invention to solve its technical problem is as follows: On the one hand, a methyl propionate catalytic hydrolysis distillation system is provided, comprising: a methyl propionate hydrolysis distillation device, a propionic acid separation device, a propionic acid refining device, and a methanol distillation device: the methyl propionate hydrolysis distillation device includes a hydrolysis distillation column; the propionic acid separation device includes a propionic acid dehydration column; the propionic acid refining device includes a propionic acid refining column; the methanol distillation device includes a methanol distillation column; the top of the hydrolysis distillation column is connected to the methanol distillation column; the bottom of the hydrolysis distillation column is connected to the propionic acid dehydration column; and the bottom of the propionic acid dehydration column is connected to the propionic acid refining column.
[0006] The methyl propionate hydrolysis unit is used to hydrolyze raw materials to obtain an aqueous solution of propionic acid and a methyl propionate solution of methanol. A metered amount of methyl propionate, after preheating, enters the bottom of the reaction zone of a catalytic distillation column filled with cation exchange resin. Metered water, after preheating, is simultaneously added from the top of the reaction zone. The methyl propionate and water undergo a hydrolysis reaction within the reaction zone. Unhydrolyzed methyl propionate and water undergo azeotropic condensation, which is then metered and returned to the reaction zone in the column to continue the reaction. The resulting aqueous solution of propionic acid is drawn from a distillation vessel at the bottom of the column. In the reactive distillation step, a portion (60%–85%) of the condensate from the methyl propionate and methanol is refluxed to the top of the reactive distillation column.
[0007] The hydrolysis distillation column is a Hastelloy distillation column, connected by column sections. The lengths of the rectifying section, reaction section, and stripping section can be determined by adjusting the number of column sections. Furthermore, the feed and temperature measurement positions can be determined by selecting feed inlet and temperature measuring inlet sections. As a preferred embodiment, the hydrolysis distillation column has 30-50 trays. From top to bottom, the column is configured with a rectifying section, a hydrolysis reaction section, and a stripping section. The rectifying section has 5-10 trays, the hydrolysis reaction section has 20-35 trays, and the stripping section has 5-10 trays. The hydrolysis reaction section is composed of multiple catalyst sections and multiple packed sections connected alternately. The hydrolysis reaction section has 3-10 feed inlets from top to bottom, preferably 5-7. The catalyst is preferably a cation exchange resin, and the entire hydrolysis reaction section is filled with cation exchange resin. The packing material is preferably glass spring packing.
[0008] The propionic acid separation unit is used to separate and obtain high-concentration propionic acid. The bottom liquid of the hydrolysis distillation column is sent to the propionic acid dehydration column for separation. The propionic acid aqueous solution is obtained at the top of the column and sent to the reactive distillation column. Propionic acid is distilled out at the bottom of the column. The distilled propionic acid is purified by the propionic acid refining column to remove heavy components.
[0009] As a preferred technical solution, the propionic acid dehydration tower has 25 to 40 trays.
[0010] The propionic acid refining unit is used to remove heavy components from propionic acid to reduce the acid content in the hydrolysis system. The propionic acid refining process involves further refining high-concentration propionic acid, obtaining the final product at the top of the column, and collecting the heavy components in the bottom of the column.
[0011] As a preferred technical solution, the propylene refining tower has 15 to 30 trays, and the propionic acid outlet of the propionic acid refining tower is located at the 3rd to 10th tray.
[0012] A methanol distillation column is used to distill a methanol-methyl propionate solution to obtain a high concentration of methanol. The condensate from the top of the hydrolysis distillation column is sent to the methanol distillation column for separation, and a high concentration of methanol is distilled off at the top of the column.
[0013] As a preferred technical solution, the methanol distillation column has 20 to 30 trays; the methanol outlet of the methanol distillation column is located at the 5th to 10th tray.
[0014] As a preferred technical solution, the methyl propionate hydrolysis distillation apparatus further includes a heat exchanger I and a reflux buffer tank I; the top of the hydrolysis distillation column, heat exchanger I, and reflux buffer tank I are sequentially connected; the outlet of reflux buffer tank I is connected to a methanol distillation column and a reflux hydrolysis distillation column, respectively; the bottom of the hydrolysis distillation column is connected to a propionic acid dehydration column and a reflux hydrolysis distillation column, respectively. Distillation process: The raw material is fed to the hydrolysis distillation column for hydrolysis distillation. An aqueous solution of propionic acid is obtained in the bottom of the column, and methanol and methyl propionate vapors are distilled off at the top of the column. These vapors are condensed through heat exchanger I, and the condensed methyl propionate and methanol then enter the separation step.
[0015] As a preferred technical solution, the propionic acid separation unit also includes a heat exchanger II and a reflux buffer tank II; the top of the propionic acid dehydration tower, the heat exchanger II, and the reflux buffer tank II are connected in sequence; the outlet of the reflux buffer tank II is connected to the hydrolysis distillation tower and the reflux propionic acid dehydration tower respectively; the bottom of the propionic acid dehydration tower is connected to the propionic acid refining unit and the reflux propionic acid dehydration tower respectively.
[0016] The invention also includes a collection device for collecting a portion of the mixture from a high-concentration solution of propionic acid and methanol, thereby reducing the acid and methanol content in the device. Propionic acid and other heavy components such as acids are collected from the propionic acid refining tower; methanol is collected from the methanol tower to reduce the methanol and acid content in the hydrolysis system. The propionic acid refining device is used to remove heavy components from propionic acid. The method for collecting the material is as follows: it is taken out after the heat exchanger in the process flow, and nitrogen is purged at the top of the tank containing the mixture to reduce the volatilization of organic matter.
[0017] As a preferred technical solution, the propionic acid refining unit also includes heat exchanger III, a propionic acid product tank, and a distillation tank I; the top of the propionic acid refining tower is refluxed through heat exchanger III; the propionic acid outlet is connected to the propionic acid product tank; and the bottom of the propionic acid refining tower is connected to the distillation tank I and the reflux propionic acid refining tower respectively.
[0018] As a preferred technical solution, the methanol distillation unit also includes heat exchanger IV and distillation tank II; the top of the methanol distillation column is refluxed through heat exchanger IV; the methanol outlet is connected to the methanol product tank; and the bottom of the methanol distillation column is connected to the hydrolysis distillation column and the reflux methanol distillation column respectively.
[0019] On the other hand, the present invention provides a method for preparing propionic acid by hydrolysis of methyl propionate, using any of the above-described methyl propionate catalytic hydrolysis distillation systems; the raw material containing methyl propionate and water is hydrolyzed and distilled to obtain a mixed solution containing propionic acid, methanol, water and methyl propionate.
[0020] As a preferred technical solution, the conditions for the hydrolysis distillation include: a hydrolysis temperature of 60–110°C; a molar ratio of water to methyl propionate of 1–6:1; a reflux ratio of 1–5; an empty column velocity of 0.2–1 cubic meter per cubic meter of catalyst per hour; a top temperature of 50–75°C and a pressure of 0.1–0.2 MPa at the top of the hydrolysis distillation column; a bottom temperature of 80–160°C and a pressure of 0.1–0.2 MPa at the bottom of the hydrolysis distillation column; and a reflux ratio of 1–5 at the top of the hydrolysis distillation column.
[0021] As a preferred technical solution, the top of the hydrolysis distillation column is connected to a reflux buffer tank I. The outlet of the reflux buffer tank I is divided into two streams, one of which is connected to the methanol column and the other is returned to the hydrolysis distillation column. The flow ratio is from the methanol column to the hydrolysis distillation column = 1:2 to 1:5.
[0022] As a preferred technical solution, the bottom of the hydrolysis distillation column is divided into two streams: one stream connects to the propionic acid dehydration column, and the other stream returns to the hydrolysis distillation column, with a flow ratio of 1:2 to 1:4.
[0023] As a preferred technical solution, the method further includes propionic acid separation, wherein the conditions for propionic acid separation include: the top temperature of the propionic acid dehydration tower is 100-120℃ and the pressure is 0.1-0.2 MPa; the bottom temperature of the propionic acid dehydration tower is 140-170℃ and the pressure is 0.1-0.2 MPa; and the reflux ratio of the propionic acid dehydration tower is 2-4.
[0024] As a preferred technical solution, the top of the propionic acid dehydration tower is connected to reflux buffer tank II. The outlet of reflux buffer tank II is divided into two streams: one stream connects to the hydrolysis distillation tower, and the other stream refluxes back to the propionic acid dehydration tower, with a flow ratio of 1:2 to 1:5.
[0025] As a preferred technical solution, the bottom of the propionic acid dehydration tower is divided into two streams, one of which is connected to the propionic acid refining unit, and the other is returned to the propionic acid dehydration tower. The flow ratio of the stream to the propionic acid refining unit and the stream to the propionic acid dehydration tower is 1:2 to 1:4.
[0026] As a preferred technical solution, the method further includes propionic acid purification, wherein the conditions for propionic acid purification include: the top temperature of the propylene purification tower is 135-150℃ and the pressure is 0.1-0.2 MPa; the bottom temperature of the propylene purification tower is 145-155℃ and the pressure is 0.1-0.2 MPa; and the reflux ratio of the propylene purification tower is 2-4.
[0027] As a preferred technical solution, returning the stream to the propionic acid refining tower can improve separation efficiency and separation degree, and ensuring high-concentration propionic acid by controlling the reflux rate and the output rate. Reflux rate: Output rate = 2:1 to 5:1 (volume ratio).
[0028] As a preferred technical solution, the method further includes methanol distillation, wherein the conditions for methanol distillation include: the top temperature of the methanol distillation column is 60-70℃ and the pressure is 0.1-0.2 MPa; the bottom temperature of the methanol distillation column is 80-90℃ and the pressure is 0.1-0.2 MPa; and the reflux ratio of the methanol distillation column is 2-4.
[0029] As a preferred technical solution, the bottom of the methanol distillation column is connected to a hydrolysis distillation column, and high-concentration methanol is ensured by controlling the reflux rate and the output rate. Reflux rate:output rate = 2:1 to 5:1
[0030] As a preferred technical solution, the method for preparing propionic acid by hydrolysis of methyl propionate includes the following steps:
[0031] S1 Methyl propionate hydrolysis distillation: The raw material containing methyl propionate and water is hydrolyzed and distilled in a hydrolysis distillation column. The bottom of the hydrolysis distillation column yields an aqueous solution containing propionic acid, and the top of the hydrolysis distillation column yields vapor containing methanol and methyl propionate.
[0032] S2 Propionic acid separation: The aqueous solution containing propionic acid enters the propionic acid dehydration tower for separation. 95% to 99% propionic acid is obtained from the bottom of the propionic acid dehydration tower, and the propionic acid aqueous solution is distilled from the top of the propionic acid dehydration tower and returned to the hydrolysis reaction distillation tower.
[0033] S3 Propionic Acid Refining: 95% to 99% of propionic acid enters the propylene refining tower for distillation and purification. Propionic acid product is obtained at the top of the propylene refining tower, and heavy components are obtained at the bottom of the propylene refining tower.
[0034] S4 Methanol Distillation: Vapor containing methanol and methyl propionate enters a methanol distillation column for separation. 95% to 98% methanol is distilled from the top of the methanol distillation column; methyl propionate is distilled from the bottom of the methanol distillation column and returned to the hydrolysis distillation column.
[0035] The beneficial effects of this invention are:
[0036] (1) Using the side line of the extraction device to extract reduces the methanol and acid content in the device, increases the hydrolysis rate of methyl propionate, maintains the utilization rate of the tower equipment, and can obtain high-purity propionic acid.
[0037] (2) Traditional glass distillation columns are integrally molded, with fixed column height and feed position, resulting in low hydrolysis conversion rate. The stainless steel distillation column used in this invention is connected by column sections. The lengths of the rectification section, reaction section, and stripping section can be determined by adjusting the number of column sections. Furthermore, the feed position and temperature measurement position can be determined by selecting column sections with feed inlets and temperature measuring inlets, thereby improving the efficiency of the hydrolysis process and achieving complete hydrolysis of methyl propionate.
[0038] (3) Stainless steel distillation columns can be filled with bulk or structured packing, and the tray form can be designed by the user. For catalytic distillation processes in which solid catalysts participate in the reaction, the diversity of catalyst packing forms is increased, which can better simulate industrial experiments.
[0039] (4) The process and apparatus improve the hydrolysis rate of the reaction to obtain any desired ester hydrolysis rate in the range of 35% to 98%, to obtain high concentration (>99%) propionic acid, and to recover methanol. Attached Figure Description
[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0041] Figure 1a , Figure 1b , Figure 1c The effect of each reaction parameter on the hydrolysis reaction;
[0042] Figure 2 This is a diagram of a catalytic distillation and hydrolysis apparatus for methyl propionate;
[0043] In Figure 1, 1 is a hydrolysis distillation column; 11 is heat exchanger I; 12 is reflux buffer tank I; 2 is a propionic acid dehydration column; 21 is heat exchanger II; 22 is reflux buffer tank II; 3 is a propionic acid refining column; 31 is heat exchanger III; 32 is a propionic acid finished product tank; 33 is a distillation tank I; 4 is a methanol distillation column; 41 is heat exchanger IV; and 42 is a distillation tank II. Detailed Implementation
[0044] Organic compounds were quantitatively analyzed using a Varian-3800 gas chromatograph with FID as the detector and area normalization method for quantitative calculation.
[0045] Substance identification and analysis were performed using a Shimadzu GC / MS-QP2010 gas chromatograph-mass spectrometer with an E1 source.
[0046] Moisture content was analyzed using a Metrohm 756KF Coulometer moisture analyzer.
[0047] The hydrolysis distillation column sample separated into layers at room temperature, so the upper and lower layers were taken for analysis separately.
[0048] Methyl propionate conversion rate (%) = Mole fraction of methanol at the top of the reactive distillation column / (Mole fraction of methanol at the top of the reactive distillation column + Mole fraction of methyl propionate at the top of the reactive distillation column)
[0049] In a 100 mL reaction flask, add 5 mL of methyl propionate, 5–20 mL of water, and a catalyst (as shown in Table 1, manufactured by Kerry Environmental Technology Co., Ltd.). Heat and stir at 60–100 °C for 6–12 h. Take samples every 0.5–1 h, add an internal standard, and determine the conversion of methyl propionate by gas chromatography. Record the reaction conversion rate as a function of time. After the reaction is complete, distill to obtain propionic acid.
[0050] Table 1 Effects of different types of catalysts on the hydrolysis reaction
[0051] catalyst none S940 C150H NKC-9 K23 PCC20H 6-hour conversion rate 0 <5％ 23％ 35％ 41％ <5％
[0052] Example 1: Methyl propionate hydrolysis apparatus
[0053] like Figure 2 As shown, the methyl propionate hydrolysis system includes: a methyl propionate hydrolysis distillation unit, a propionic acid separation unit, a propionic acid purification unit, and a methanol distillation unit.
[0054] The methyl propionate hydrolysis distillation unit consists of a hydrolysis distillation column 1, a heat exchanger I12, a reflux buffer tank I12, and a pump. The top of the hydrolysis distillation column, heat exchanger I, and reflux buffer tank I are connected sequentially. The hydrolysis distillation column has 40 trays. The outlet of reflux buffer tank I is split into two streams: one connects to the methanol distillation column, and the other returns to the hydrolysis distillation column, with a flow ratio of 1:3 (to methanol distillation column:back to hydrolysis distillation column), which improves separation efficiency and resolution. The bottom of the hydrolysis distillation column is also split into two streams: one connects to the propionic acid dehydration column, and the other returns to the hydrolysis distillation column, with a flow ratio of 1:2. The hydrolysis distillation column (40 trays in total) is divided into a rectification section (7 trays), a hydrolysis reaction section (28 trays), and a stripping section (5 trays) from top to bottom. The methyl propionate inlet is located at tray 35, the water inlet is located at tray 8, the returned propionic acid aqueous solution is located at tray 12, and the temperature measuring ports are located at trays 10 and 30.
[0055] The propionic acid separation unit consists of a propionic acid dehydration tower 2, a heat exchanger II 21, a reflux buffer tank II 22, and a pump. The propionic acid dehydration tower has 30 trays. The top of the tower, the heat exchanger, and the reflux buffer tank II are connected sequentially. The outlet of the reflux buffer tank II is connected to both the hydrolysis distillation tower and the reflux propionic acid dehydration tower, with a flow rate ratio of 1:3. The bottom of the propionic acid dehydration tower splits into two streams: one connects to the propionic acid refining unit, and the other returns to the propionic acid dehydration tower. The flow rate ratio from the refining unit to the returning unit is 1:2, which improves separation efficiency and resolution.
[0056] The propionic acid refining unit consists of a propionic acid refining column 3, a heat exchanger III 31, a propionic acid product tank 32, a distillation tank I 33, and pumps. The propionic acid refining column has 20 trays. The top of the column is refluxed via the heat exchanger; the propionic acid outlet (located at the 5th tray) is connected to the propionic acid product tank; and the bottom of the column is connected to the distillation tank. The return stream to the propionic acid refining column improves separation efficiency and resolution. High-concentration propionic acid is ensured by controlling the reflux rate and the output rate; the reflux rate to output rate is 3:1 (volume ratio).
[0057] The methanol distillation unit consists of a methanol distillation column 4, a heat exchanger IV41, a distillation tank II42, and a pump. It has 25 trays. The top of the methanol distillation column is refluxed via the heat exchanger; the methanol outlet (located at the 5th tray) is connected to a methanol product tank; the bottom of the column is connected to a hydrolysis distillation column. High-concentration methanol is ensured by controlling the reflux and production rates; the reflux to production rate ratio is 3:1 (volume ratio). The methanol distillation unit and propionic acid refining unit include process pipelines and a nitrogen purging system for propionic acid, methanol, and heavy components collected from the process pipelines. Nitrogen is purged at the top of the production tank to reduce organic matter volatilization.
[0058] Example 2: Hydrolysis process of methyl propionate
[0059] The process of hydrolyzing methyl propionate using the apparatus described in Example 1 includes:
[0060] (1) Hydrolysis distillation: Pure water and methyl propionate were mixed at a molar ratio of 1.3:1 and fed from the top of the hydrolysis distillation column (methyl propionate was prepared by the carbonylation process of ethylene, which also contained methanol and other impurities). The hydrolysis reaction section was filled with hydrolysis catalyst #3 from Kerry Environmental Protection Technology Co., Ltd. Under the conditions of a bottom temperature of 107.2℃, a bottom pressure of 0.15 MPa, a top temperature of 64.1℃, and a top pressure of 0.11 MPa, methyl propionate was hydrolyzed into propionic acid and methanol, as shown in the following reaction formula:
[0061]
[0062] The hydrolysis distillation column has a reflux ratio of 3, a hydrolysis temperature of 90°C at the lower section (30th tray) and 80°C at the upper section (10th tray), a water to methyl propionate molar ratio of 1.3:1, and an empty column velocity of 0.8 cubic meters of catalyst per hour. The methyl propionate inlet is at the 35th tray, the water inlet is at the 8th tray, and the returned propionic acid solution is at the 12th tray.
[0063] This is a typical reversible reaction. The hydrolysis distillation column separates propionic acid and methanol from the mixture, shifting the equilibrium towards the products. The bottom of the hydrolysis distillation column yields an aqueous solution (bottom liquid) containing a high concentration of propionic acid; the top of the column distills methanol and methyl propionate vapors, i.e., a methyl propionate solution containing 84.6% (wt) methanol (top vapor), which is condensed in a heat exchanger (exchanging heat with cooling water) and then enters the methanol distillation column.
[0064] Table 2. Composition and Temperature Distribution of Methyl Propionate in Catalytic Distillation
[0065]
[0066] (2) Propionic acid dehydration: The bottom liquid is pumped to the propionic acid dehydration tower, and high-concentration propionic acid (99wt%) is obtained in the bottom of the tower (bottom liquid). Water containing a small amount of propionic acid (18.1wt%) is distilled off from the top of the tower. After being condensed by a heat exchanger (exchanging heat with cooling water), it is pumped to the hydrolysis distillation tower. Water is used as a raw material to continue to participate in the reaction.
[0067] (3) Propionic acid refining: The bottom liquid of the propionic acid dehydration tower enters the propionic acid refining tower for distillation. The bottom liquid of the tower is taken out as acid and other heavy components. The side stream of the tower section is taken out as high-purity propionic acid product through the heat exchanger and enters the propionic acid product tank. Nitrogen gas is charged on the top of the product tank to reduce the volatilization of organic matter.
[0068] (4) Methanol distillation: The overhead vapor from the hydrolysis distillation column enters the methanol distillation column for distillation purification. The bottom of the column yields a methyl propionate solution containing trace amounts of methanol (bottom liquid), which is pumped as feed to the hydrolysis distillation column to continue participating in the reaction. The side stream of the column section yields high-concentration methanol (>98%), which is condensed at 35°C in a heat exchanger. The condensate is collected in the methanol product tank, and nitrogen gas is purged at the top of the product tank to reduce the volatilization of organic matter.
[0069] The hydrolysis method of this invention involves a catalytic hydrolysis reaction of metered water and methyl propionate in a distillation column filled with cation exchange resin. Unhydrolyzed reactants are condensed, metered again, and refluxed into the reaction zone. The hydrolysate is extracted from a distillation vessel at the bottom of the column. The catalytic distillation hydrolysis apparatus includes a reactive distillation unit, a propionic acid separation unit, a propionic acid purification unit, and a methanol distillation unit. The hydrolysis distillation equipment uses a stainless steel distillation column with a cylindrical column body connected by column sections. It can be filled with bulk or structured packing materials, and the tray configuration can be customized. For catalytic distillation processes involving solid catalysts, this increases the diversity of catalyst packing methods. This invention can achieve any desired ester decomposition rate within the range of 35% to 98%.
[0070] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, or time, is stated as 50-90, in this specification it means specifically listing values such as 51-89, 52-88, ..., 69-71, and 70-71. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically specified examples. In this application, in a similar manner, all possible combinations of numerical values between the listed minimum and maximum values are considered to have been disclosed.
[0071] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. All equivalent changes and modifications made in accordance with the scope of the patent application and the description should still fall within the scope of the patent. It should be noted that the above-described embodiments are only for explaining the invention and do not constitute any limitation on the invention. The invention has been described with reference to typical embodiments, but it should be understood that the terms used are descriptive and explanatory, not limiting. Modifications can be made to the invention within the scope of the claims, and revisions can be made without departing from the scope and spirit of the invention. Although the invention described herein relates to specific methods, materials, and embodiments, it does not mean that the invention is limited to the specific examples disclosed herein. On the contrary, the invention can be extended to all other methods and applications with the same function.
Claims
1. A methyl propionate catalytic hydrolysis distillation system, characterized in that, The system includes: Methyl propionate hydrolysis distillation unit, propionic acid separation unit, propionic acid refining unit, and methanol distillation unit: The methyl propionate hydrolysis distillation apparatus includes a hydrolysis distillation column; The propionic acid separation unit includes a propionic acid dehydration tower; The propionic acid refining unit includes a propionic acid refining tower; A methanol distillation unit includes a methanol distillation column; The top of the hydrolysis distillation column is connected to the methanol distillation column; the bottom of the hydrolysis distillation column is connected to the propionic acid dehydration column; and the bottom of the propionic acid dehydration column is connected to the propionic acid refining column.
2. The methyl propionate catalytic hydrolysis distillation system according to claim 1, characterized in that, The methyl propionate hydrolysis distillation apparatus also includes heat exchanger I and reflux buffer tank I; The top of the hydrolysis distillation column, heat exchanger I, and reflux buffer tank I are connected in sequence; the outlet of reflux buffer tank I is connected to the methanol distillation column and the reflux hydrolysis distillation column respectively; the bottom of the hydrolysis distillation column is connected to the propionic acid dehydration column and the reflux hydrolysis distillation column respectively. The propionic acid separation unit also includes heat exchanger II and reflux buffer tank II; The top of the propionic acid dehydration tower, heat exchanger II, and reflux buffer tank II are connected in sequence; the outlet of reflux buffer tank II is connected to the hydrolysis distillation tower and the reflux propionic acid dehydration tower respectively. The bottom of the propionic acid dehydration tower is connected to both the propionic acid refining unit and the reflux propionic acid dehydration tower. The propionic acid refining unit also includes heat exchanger III, a propionic acid finished product tank, and distillation tank I; The top of the propionic acid refining column is refluxed via heat exchanger III; the propionic acid outlet is connected to the propionic acid finished product tank; the bottom of the propionic acid refining column is connected to distillation tank I and the reflux propionic acid refining column respectively. The methanol distillation unit also includes heat exchanger IV and distillation tank II; The top of the methanol distillation column is refluxed via heat exchanger IV; the methanol outlet is connected to the methanol product tank; and the bottom of the methanol distillation column is connected to both the hydrolysis distillation column and the reflux methanol distillation column.
3. The methyl propionate catalytic hydrolysis distillation system according to claim 1 or 2, characterized in that, The number of trays in the hydrolysis distillation column is 30 to 50; And / or, the hydrolysis distillation column is provided with a rectification section, a hydrolysis reaction section and a stripping section from top to bottom; the number of trays in the rectification section is 5 to 10, the number of trays in the hydrolysis reaction section is 20 to 35, and the number of trays in the stripping section is 5 to 10; Preferably, the hydrolysis reaction section is composed of multiple catalyst tower sections and multiple packed tower sections connected alternately; The hydrolysis reaction section has 3 to 10 feed inlets from top to bottom, preferably 5 to 7.
4. The methyl propionate catalytic hydrolysis distillation system according to claim 1, 2, or 3, characterized in that, The propionic acid dehydration tower has 25 to 40 trays; The propylene refining tower has 15 to 30 trays, and the propionic acid outlet of the propionic acid refining tower is located at the 3rd to 10th tray.
5. The catalytic hydrolysis distillation system for methyl propionate according to any one of claims 1-4, characterized in that, The methanol distillation column has 20 to 30 trays; The methanol outlet of the methanol distillation column is located at the 5th to 10th tray.
6. A method for preparing propionic acid by hydrolysis of methyl propionate, characterized in that, The methyl propionate catalytic hydrolysis distillation system according to any one of claims 1-5 is used; the raw material containing methyl propionate and water is hydrolyzed and distilled to obtain a mixed solution containing propionic acid, methanol, water and methyl propionate.
7. The method according to claim 6, characterized in that, The conditions for the hydrolysis distillation include: The hydrolysis temperature is 60–110℃; The molar ratio of water to methyl propionate is 1 to 6:1; The reflux ratio is 1 to 5; The empty tower velocity is 0.2 to 1 cubic meter per hour per cubic meter of catalyst; The top temperature of the hydrolysis distillation column is 50–75℃, and the pressure is 0.1–0.2 MPa. The reboiler temperature of the hydrolysis distillation column is 80–160℃, and the pressure is 0.1–0.2 MPa. The reflux ratio of the hydrolysis distillation column is 1 to 5.
8. The method according to claim 6 or 7, characterized in that, The method further includes propionic acid separation, wherein the conditions for propionic acid separation include: The top temperature of the propionic acid dehydration tower is 100–120℃, and the pressure is 0.1–0.2 MPa. The temperature of the bottom of the propionic acid dehydration tower is 140–170℃, and the pressure is 0.1–0.2 MPa. The reflux ratio of the propionic acid dehydration tower is 2-4; The method further includes the purification of propionic acid, wherein the conditions for the purification of propionic acid include: The top temperature of the propylene refining tower is 135–150℃, and the pressure is 0.1–0.2 MPa. The bottom temperature of the propylene refining tower is 145–155℃, and the pressure is 0.1–0.2 MPa. The reflux ratio of the propylene refining tower is 2 to 4.
9. The method according to any one of claims 6-8, characterized in that, The method further includes methanol distillation, wherein the conditions for methanol distillation include: The top temperature of the methanol distillation column is 60–70℃, and the pressure is 0.1–0.2 MPa. The reboiler temperature of the methanol distillation column is 80–90℃, and the pressure is 0.1–0.2 MPa. The reflux ratio of the methanol distillation column is 2 to 4.
10. The method according to any one of claims 6-9, characterized in that, The method for preparing propionic acid by hydrolysis of methyl propionate includes the following steps: S1 Methyl propionate hydrolysis distillation: The raw material containing methyl propionate and water is hydrolyzed and distilled in a hydrolysis distillation column. The bottom of the hydrolysis distillation column yields an aqueous solution containing propionic acid, and the top of the hydrolysis distillation column yields vapor containing methanol and methyl propionate. S2 Propionic acid separation: The aqueous solution containing propionic acid enters the propionic acid dehydration tower for separation. 95% to 99% propionic acid is obtained from the bottom of the propionic acid dehydration tower, and the propionic acid aqueous solution is distilled from the top of the propionic acid dehydration tower and returned to the hydrolysis reaction distillation tower. S3 Propionic Acid Refining: 95% to 99% of propionic acid enters the propylene refining tower for distillation and purification. Propionic acid product is obtained at the top of the propylene refining tower, and heavy components are obtained at the bottom of the propylene refining tower. S4 Methanol Distillation: Vapor containing methanol and methyl propionate enters a methanol distillation column for separation. 95% to 98% methanol is distilled from the top of the methanol distillation column; methyl propionate is distilled from the bottom of the methanol distillation column and returned to the hydrolysis distillation column.