Tail gas treatment system for methyl propionate synthesis process

Abstract

The utility model relates to a tail gas treatment system for a methyl propionate synthesis process. The system comprises a reaction kettle (1), a gas-liquid separator (2), an evaporator (3), a rectifying tower (4) and a washing tower (5), wherein a tail gas pipeline of the methyl propionate synthesis process is connected with the reaction kettle (1); the reaction kettle (1) is connected with the gas-liquid separator (2); a gas phase outlet is formed in the top of the gas-liquid separator (2) and is connected with the washing tower (5); a liquid phase material flow outlet is formed in the bottom of the gas-liquid separator (2) and is connected with the evaporator (3); a liquid phase outlet in the bottom of the evaporator (3) is connected with the reaction kettle (1), and a gas phase material flow outlet in the top of the evaporator (3) is connected with the rectifying tower (4). The methyl propionate recycling device can effectively recycle methyl propionate products in recycle gas and purge gas, methanol entering the reaction kettle along with the recycle gas can be used as a reaction raw material, and the methyl propionate recycling device is simple in process, economical, efficient and good in application prospect.

Description

Technical Field

[0001] The utility model belongs to the technical field of olefin carbonylation synthesis of organic chemical products, in particular to a tail gas treatment system for a methyl propionate synthesis process. Background Art

[0002] Methyl methacrylate (MMA) is the basic raw material for high-end materials such as aerospace, electronic information, optical fiber, optical lenses, robots, etc. By the end of 2021, my country's MMA production capacity will exceed 1.7 million tons / year. MMA industrial production methods include acetone cyanohydrin (ACH) method, isobutylene oxidation method, C2 method, etc. The ACH method is mature in technology and has always been the main route for MMA production in my country. In 2021, the total production capacity will reach 1.16 million tons / year, accounting for about 68% of the total production capacity. From 2023 to 2026, many domestic companies will plan to build or expand MMA production facilities, and the more competitive isobutylene method and ethylene method will usher in good market opportunities.

[0003] The ACH method was developed by the British Imperial Chemical Industries (ICI) and industrialized in 1937. At present, my country has mastered the ACH method MMA production technology. However, this technology uses highly toxic hydrocyanic acid and sulfuric acid as raw materials, which puts great pressure on environmental protection. At present, the methyl methacrylate production device using the acetone cyanohydrin method (excluding by-products) has been listed as a restricted category in the guidance catalogue of industrial structure adjustment, and the resistance to new production capacity using this route will become increasingly greater.

[0004] The isobutylene process was developed by Nippon Catalyst Chemical Industry Co., Ltd. and Mitsubishi Rayon Co., Ltd. in 1982. More than 20% of the world's MMA production capacity uses the isobutylene process, mainly for the Japanese market. This route has a long process flow, complex equipment, low overall MMA selectivity, and high investment and production costs.

[0005] C2 MMA synthesis technology, represented by Lucite (now acquired by Mitsubishi Chemical) α-MMA technology, was developed by Shell and transferred to Lucite through ICI. The latter further developed and industrialized it, and built the first 120,000 tons / year industrial unit on Jurong Island, Singapore in 2008. The 250,000 tons / year MMA production unit built in Saudi Arabia has also been put into operation. This route has mild process conditions, is safe and environmentally friendly, and can save 40% of investment and production costs compared to traditional routes. Currently, this technology is monopolized by Japan's Mitsubishi Chemical and has not been transferred to the Chinese market.

[0006] The two-step process for synthesizing MMA by ethylene route includes ethylene carbonylation to produce methyl propionate and condensation of methyl propionate and formaldehyde to produce MMA. There are not many patents disclosed about the reaction device and process for ethylene carbonylation to produce methyl propionate.

[0007] Lucite International UK Ltd. disclosed in CN 102741213 A a continuous method for carbonylating ethylene with CO in the presence of a co-reactant with mobile hydrogen atoms and a suitable catalyst system in a liquid phase. Southwest Chemical Research and Design Institute Co., Ltd. disclosed in CN201410797826 a reaction device for producing methyl propionate, comprising a static mixer, a carbonylation reactor and a flash evaporator connected in sequence, wherein the top of the flash evaporator is connected to a light removal tower, and the bottom of the flash evaporator is connected to a catalyst recovery reactor; the bottom of the light removal tower is connected to a rectification and refining system; the catalyst recovery reactor is connected to a liquid-liquid separation tower, and the upper layer material separated by the liquid-liquid separation tower enters a tar incineration system, and the obtained heavy phase returns to the carbonylation reactor.

[0008] In the ethylene carbonylation process for producing methyl propionate, ethylene, CO and methanol are converted into methyl propionate under the action of a catalyst, with a large amount of circulating gas and a small amount of purge gas. Since the saturated vapor pressure of the product methyl propionate is relatively high at normal temperature and pressure, the circulating gas and purge gas contain a large amount of methyl propionate that has not been fully condensed and separated. This part of the methyl propionate product is returned to the reactor after being pressurized by the compressor with the circulating gas or is discharged with the purge gas, causing a series of problems such as increased system load and product loss. Utility Model Content

[0009] The purpose of the utility model is to solve the above problems and propose a tail gas treatment system for methyl propionate synthesis process. In the system, circulating gas and purge gas are sent to a washing tower with methanol as absorbent. After the methyl propionate carried is fully separated, the circulating gas is returned to the reactor through a compressor, and the purge gas is discharged. The system can effectively recover the methyl propionate product in the circulating gas and the purge gas, and the methanol entering the reactor with the circulating gas can be used as a reaction raw material. The process is simple, economical and efficient, and has good application prospects.

[0010] In order to achieve the purpose of the above utility model, the technical solution of the utility model is as follows:

[0011] A tail gas treatment system for a methyl propionate synthesis process comprises a reactor, a gas-liquid separator, an evaporator, a distillation tower and a washing tower; wherein a tail gas pipeline of the methyl propionate synthesis process is connected to the reactor; the reactor is connected to the gas-liquid separator; the top of the gas-liquid separator is a gas phase outlet, which is connected to the washing tower; the bottom of the gas-liquid separator is a liquid phase logistics outlet, which is connected to the evaporator; the liquid phase outlet at the bottom of the evaporator is connected to the reactor, and the gas phase logistics outlet at the top of the evaporator is connected to the distillation tower; a liquid phase extraction logistics outlet is provided at the top of the distillation tower, which is connected to the reactor, and a gas phase extraction logistics outlet is also provided at the top of the distillation tower, which is connected to the washing tower.

[0012] As a better implementation in the present application, in the tail gas treatment system for the methyl propionate synthesis process, the number of washing towers is 1-2, and each washing tower is connected in parallel.

[0013] As a better implementation method in the present application, a compressor is also provided in the tail gas treatment system for the methyl propionate synthesis process.

[0014] As a better embodiment of the present application, in the tail gas treatment system for the methyl propionate synthesis process, a washing tower is provided with a methanol feed port at the top, a gas inlet at the bottom, a gas outlet at the top, and a liquid outlet at the bottom; the washing tower is provided with two gas outlet pipelines through the gas outlet arranged at the top, one of which is connected to the compressor and then to the reactor; the other gas outlet pipeline is connected to the purge gas device.

[0015] As a better embodiment of the present application, in the tail gas treatment system for the methyl propionate synthesis process, a liquid outlet is provided at the bottom of the washing tower, and the liquid outlet is connected to the distillation tower. The liquid part of the lower part of the washing tower is used as a circulating spray liquid, and part of it is sent to the distillation tower or the reactor, that is, the lower part of the washing tower is connected to the distillation tower or the reactor.

[0016] As a better embodiment of the present application, in the tail gas treatment system for the methyl propionate synthesis process, the gas phase outlet at the top of the gas-liquid separator and the top gas phase extraction flow outlet of the distillation tower are connected to the same washing tower or are respectively connected to different washing towers.

[0017] As a better embodiment of the present application, in the tail gas treatment system for the methyl propionate synthesis process, a cooling separator is further provided after the evaporator, and the gas phase logistics outlet provided at the top of the evaporator is connected to the cooling separator; the cooling separator is provided with a gas phase logistics outlet and a liquid phase logistics outlet; wherein the liquid phase logistics outlet is connected to the distillation tower, and the gas phase logistics outlet is connected to the washing tower.

[0018] As a better implementation method in the present application, the bottom of the distillation tower is connected to the methyl propionate product tank.

[0019] As a preferred embodiment of the present application, the methanol used as absorbent entering the scrubbing tower has a temperature of -30°C to 50°C.

[0020] As a preferred embodiment of the present application, the operating pressure of the washing tower is 1 to 15 bar.

[0021] As a better embodiment of the present application, the tail gas treatment system for the methyl propionate synthesis process is used in the methyl propionate synthesis process. In the process, ethylene, carbon monoxide and methanol are subjected to carbonylation reaction to synthesize methyl propionate. The carbonylation reaction temperature is 60 to 150° C. and the pressure is 5 to 30 bar. The catalyst system used is composed of a palladium salt, a phosphine ligand and a co-catalyst.

[0022] Compared with the existing technology, the beneficial effects of the utility model are:

[0023] In the tail gas treatment system for the methyl propionate synthesis process described in the utility model, the circulating gas and the purge gas are sent to a washing tower with methanol as an absorbent, and after the methyl propionate carried is fully separated, the circulating gas is returned to the reactor through a compressor, and the purge gas is discharged. The system solves a series of problems such as a large amount of methyl propionate product that is not fully condensed and separated in the circulating gas and the purge gas in the ethylene carbonylation process for preparing methyl propionate, resulting in increased system load and product loss. The methyl propionate product in the circulating gas and the purge gas can be effectively recovered, and the methanol entering the reactor together with the circulating gas can be used as a reaction raw material. The process is simple, economical and efficient, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic structural diagram of a tail gas treatment system for a methyl propionate synthesis process as described in Example 1 of the utility model;

[0025] Among them, 1 is the reactor, 2 is the gas-liquid separator, 3 is the evaporator, 4 is the distillation tower, 5 is the washing tower, 5-1 is the methanol feed port, 5-2 is the gas inlet, 5-3 is the gas outlet, 5-4 is the liquid outlet, and 6 is the compressor.

[0026] Figure 2 This is a schematic structural diagram of a tail gas treatment system for a methyl propionate synthesis process as described in Example 2 of the present utility model;

[0027] Among them, 1 is a reactor, 2 is a gas-liquid separator, 3 is an evaporator, 4 is a distillation tower, 5A is a washing tower, 5A-1 is a methanol feed inlet of (washing tower one), 5A-2 is a gas inlet of (washing tower one), 5A-3 is a gas outlet of (washing tower one), 5A-4 is a liquid outlet of (washing tower one), 5B is a washing tower, 5B-1 is a methanol feed inlet of (washing tower two), 5B-2 is a gas inlet of (washing tower two), 5B-3 is a gas outlet of (washing tower two), 5B-4 is a liquid outlet of (washing tower two), and 6 is a compressor. DETAILED DESCRIPTION

[0028] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0029] Any feature disclosed in this specification (including claims and abstract), unless otherwise stated, may be replaced by other equivalent or alternative features having similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0030] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0031] Embodiment 1:

[0032] like Figure 1 As shown, a tail gas treatment system for a methyl propionate synthesis process comprises a reactor 1, a gas-liquid separator 2, an evaporator 3, a distillation tower 4 and a washing tower 5; wherein, the tail gas pipeline of the methyl propionate synthesis process is connected to the reactor 1; the reactor 1 is connected to the gas-liquid separator 2; the top of the gas-liquid separator 2 is a gas phase outlet, and the gas phase outlet (gas phase logistics, i.e., high-pressure tail gas) is connected to the washing tower 5; the bottom of the gas-liquid separator 2 is a liquid phase logistics outlet, and the liquid phase logistics outlet is connected to the evaporator 3; the liquid phase outlet at the bottom of the evaporator 3 is connected to the reactor 1, and the gas phase logistics outlet at the top of the evaporator 3 is connected to the distillation tower 4; the top of the distillation tower 4 is provided with a liquid phase production logistics outlet, and the liquid phase production logistics outlet is connected to the reactor 1, and the top of the distillation tower 4 is also provided with a gas phase production logistics outlet (gas phase logistics, i.e., low-pressure tail gas), and the gas phase production logistics outlet is connected to the washing tower 5, and the bottom of the distillation tower 4 is connected to the methyl propionate product tank.

[0033] Furthermore, in the tail gas treatment system for the methyl propionate synthesis process, the number of the washing tower 5 is one.

[0034] Furthermore, the washing tower 5 is provided with a methanol feed port 5-1 at the top, a gas inlet 5-2 at the bottom, a gas outlet 5-3 at the top, and a liquid outlet 5-4 at the bottom; the washing tower 5 is provided with two gas outlet pipelines through the gas outlet 5-3 at the top, one of which is connected to the compressor 6 and then connected to the reactor 1; the other gas outlet pipeline is connected to the purge gas device. That is, the gas discharged from the washing tower 5 is divided into two parts, one part is returned to the reactor 1 through the compressor, and the other part is discharged as purge gas.

[0035] Furthermore, a liquid outlet is provided at the bottom of the washing tower 5, and the liquid outlet is connected to the distillation tower 4. The liquid part at the bottom of the washing tower (5) is used as a circulating spray liquid, and part of it is sent to the distillation tower or the reactor.

[0036] Furthermore, the gas phase outlet at the top of the gas-liquid separator 2 and the gas phase extraction flow outlet at the top of the distillation tower 4 are both connected to the washing tower, that is, the high-pressure tail gas and the low-pressure tail gas enter the same washing tower.

[0037] Furthermore, a cooling separator is provided after the evaporator 3, and the gas phase logistics outlet provided at the top of the evaporator 3 is connected to the cooling separator; a gas phase logistics outlet and a liquid phase logistics outlet are provided on the cooling separator; wherein the liquid phase logistics outlet is connected to the distillation tower 4, and the gas phase logistics outlet is connected to the washing tower 5.

[0038] The specific steps are:

[0039] Methanol, ethylene and CO raw materials as well as the materials returned from the separation and refining unit are transported to a 2L reactor 1. A gas-liquid separator 2 is arranged behind the reactor 1. The gas phase logistics (high-pressure tail gas) outlet is connected to a washing tower 5, and the liquid phase logistics outlet is connected to an evaporator 3. The liquid phase outlet of the evaporator 3 is connected to the reactor. The gas phase logistics outlet is connected to a distillation tower 4. The liquid phase production logistics outlet of the distillation tower 4 is connected to the reactor 1. The gas phase production logistics (low-pressure tail gas) outlet at the top of the tower is connected to the washing tower 5. The methyl propionate product is produced from the bottom of the tower.

[0040] The operating temperature of the reactor 1 is 100°C and the operating pressure is 15 bar. The operating temperature of the evaporator 3 is about 63°C and the pressure is normal. The high-pressure tail gas and the low-pressure tail gas are mixed and enter the washing tower 5. The mixed gas temperature is 40°C and the flow rate is 100L / h. The volume fraction of methyl propionate is 4%. The inner diameter of the washing tower is 60mm. The tower is filled with 1.5m high glass spring packing. The operating pressure is 1.2bar, the absorption methanol feed is 240g / h, and the temperature is -5°C. The volume fraction of methyl propionate in the gas discharged from the washing tower 5 is 0.1%.

[0041] It can be seen that after the tail gas treatment system, the saturated methyl propionate in the gas is effectively separated.

[0042] Embodiment 2:

[0043] like Figure 2As shown, a tail gas treatment system for a methyl propionate synthesis process comprises a reactor 1, a gas-liquid separator 2, an evaporator 3, a distillation tower 4 and a washing tower 5A / B; wherein, the tail gas pipeline of the methyl propionate synthesis process is connected to the reactor 1; the reactor 1 is connected to the gas-liquid separator 2; the top of the gas-liquid separator 2 is a gas phase outlet, and the gas phase outlet (gas phase logistics, i.e., high-pressure tail gas) is connected to the washing tower 5A; the bottom of the gas-liquid separator 2 is a liquid phase logistics outlet, and the liquid phase logistics The outlet is connected to the evaporator 3; the liquid phase outlet at the bottom of the evaporator 3 is connected to the reactor 1, and the gas phase logistics outlet at the top of the evaporator 3 is connected to the distillation tower 4; the top of the distillation tower 4 is provided with a liquid phase production logistics outlet, and the liquid phase production logistics outlet is connected to the reactor 1, and the top of the distillation tower 4 is also provided with a gas phase production logistics outlet (gas phase logistics, i.e. low-pressure tail gas), and the gas phase production logistics outlet is connected to the washing tower 5B, and the bottom of the distillation tower 4 is connected to the methyl propionate product tank.

[0044] Furthermore, a liquid outlet is provided at the bottom of the washing tower 5A / B, and the liquid outlet is connected to the distillation tower 4. The liquid part of the lower part of the washing tower (5) is used as a circulating spray liquid, and part of it is sent to the distillation tower or the reactor.

[0045] Furthermore, a cooling separator is provided after the evaporator 3, and the gas phase logistics outlet provided at the top of the evaporator 3 is connected to the cooling separator; a gas phase logistics outlet and a liquid phase logistics outlet are provided on the cooling separator; wherein the liquid phase logistics outlet is connected to the distillation tower 4, and the gas phase logistics outlet is connected to the washing tower 5B.

[0046] The specific steps are:

[0047] Methanol, ethylene and CO raw materials as well as the materials returned from the separation and refining unit are transported to a 2L reactor 1. A gas-liquid separator 2 is arranged behind the reactor 1. The gas phase logistics (high-pressure tail gas) outlet is connected to a washing tower 5A, and the liquid phase logistics outlet is connected to an evaporator 3. The liquid phase outlet of the evaporator 3 is connected to the reactor. The gas phase logistics outlet is connected to a distillation tower 4. The liquid phase production logistics outlet of the distillation tower 4 is connected to the reactor 1. The gas phase production logistics (low-pressure tail gas) outlet at the top of the tower is connected to a washing tower 5B. The methyl propionate product is produced from the bottom of the tower.

[0048] The operating temperature of the reactor 1 is 100°C and the operating pressure is 15 bar. The operating temperature of the evaporator 3 is about 63°C and the pressure is normal. The volume fraction of methyl propionate in the gas discharged from the washing tower 5A is 0.01%, and the volume fraction of methyl propionate in the gas discharged from the washing tower 5B is 0.1%.

[0049] It can be seen that after the tail gas treatment system, the saturated methyl propionate in the gas is effectively separated.

[0050] The above-mentioned embodiments only express the specific implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the protection scope of the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the technical solution concept of the present application, and these all belong to the protection scope of the present application.

[0051] This background technology section is provided to generally present the context of the present invention, and the work of the currently named inventors, the work to the extent described in this background technology section, and aspects of this section that did not constitute prior art at the time of application are neither explicitly nor implicitly admitted to be prior art of the present invention.

Claims

1. A tail gas treatment system for a methyl propionate synthesis process, characterized in that: The system comprises a reactor (1), a gas-liquid separator (2), an evaporator (3), a distillation tower (4) and a washing tower (5); wherein the tail gas pipeline of the methyl propionate synthesis process is connected to the reactor (1); the reactor (1) is connected to the gas-liquid separator (2); the top of the gas-liquid separator (2) is a gas phase outlet, which is connected to the washing tower (5); the bottom of the gas-liquid separator (2) is a liquid phase logistics outlet, which is connected to the evaporator (3); the bottom of the evaporator (3) is a liquid phase outlet, which is connected to the reactor (1); the top of the evaporator (3) is a gas phase logistics outlet, which is connected to the distillation tower (4); the top of the distillation tower (4) is provided with a liquid phase extraction logistics outlet, which is connected to the reactor (1); the top of the distillation tower (4) is also provided with a gas phase extraction logistics outlet, which is connected to the washing tower (5).

2. The tail gas treatment system for the methyl propionate synthesis process according to claim 1, characterized in that: The number of washing towers (5) is 1-2, and the washing towers (5) are connected in parallel.

3. The tail gas treatment system for the methyl propionate synthesis process according to claim 2, characterized in that: The washing tower (5) is provided with a methanol feed port (5-1) at the top, a gas inlet (5-2) at the bottom, a gas outlet (5-3) at the top, and a liquid outlet (5-4) at the bottom; the washing tower (5) is provided with two gas outlet pipelines through the gas outlet (5-3) at the top, one of which is connected to the reaction kettle (1); and the other is connected to the purge gas device.

4. The tail gas treatment system for the methyl propionate synthesis process according to claim 2, characterized in that: The bottom of the washing tower (5) is provided with a liquid outlet, which is connected to the distillation tower (4).

5. The tail gas treatment system for the methyl propionate synthesis process according to claim 2, characterized in that: The gas phase outlet at the top of the gas-liquid separator (2) and the gas phase extraction flow outlet at the top of the distillation tower (4) are connected to the same washing tower or are respectively connected to different washing towers.

6. The tail gas treatment system for the methyl propionate synthesis process according to claim 2, characterized in that: A cooling separator is also arranged after the evaporator (3), and a gas phase flow outlet arranged at the top of the evaporator (3) is connected to the cooling separator.

7. The tail gas treatment system for the methyl propionate synthesis process according to claim 1, characterized in that: The bottom of the distillation tower (4) is connected to the methyl propionate product tank.

8. The tail gas treatment system for the methyl propionate synthesis process according to claim 3, characterized in that: A compressor (6) is arranged on the pipeline between one of the gas outlet pipelines of the washing tower (5) and the reaction kettle (1).

9. The tail gas treatment system for the methyl propionate synthesis process according to claim 4, characterized in that: The bottom of the washing tower (5) is connected to the reaction kettle (1).

10. The tail gas treatment system for the methyl propionate synthesis process according to claim 6, characterized in that: The cooling separator is provided with a gas phase logistics outlet and a liquid phase logistics outlet; The liquid phase logistics outlet is connected to the distillation tower (4), and the gas phase logistics outlet is connected to the washing tower (5).

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