WO2021047391A1

WO2021047391A1 - Method for synthesizing acetic acid by low-pressure methanol carbonylation

Info

Publication number: WO2021047391A1
Application number: PCT/CN2020/111551
Authority: WO
Inventors: 毕永胜
Original assignee: 上海浦景化工技术股份有限公司
Priority date: 2019-09-10
Filing date: 2020-08-27
Publication date: 2021-03-18
Also published as: CN111646894B; CN111646894A

Abstract

The present invention relates to a method for synthesizing acetic acid by low-pressure methanol carbonylation. The method comprises: (1) in the presence of a catalyst, introducing methanol and CO into a non-stir reactor to undergo a carbonylation reaction, and then feeding a liquid phase portion in a middle part of the non-stir reactor into a flash evaporator to undergo flash evaporation, thereby separating and obtaining a liquid phase component and a gas phase component; (2) performing heat exchange on the liquid phase component with a mother liquid flash evaporation heat exchanger, and once heated, performing secondary flash evaporation, thereby separating and obtaining a secondary liquid phase component and a secondary gas phase component; (3) feeding the separated and obtained primary gas phase and secondary gas phase components into a catalyst trap, returning the trapped and recovered catalyst back into the flash evaporator, and allowing the gas phase components to enter into a light component fractionating column to undergo fractionation, thereby obtaining light components and heavy components; (4) feeding the liquid phase components from steps (1) and (2) back into the non-stir reactor to undergo reaction; (5) feeding the heavy components from step (3) into a heavy component fractionating column to undergo fractionation, thereby obtaining an acetic acid product. The present invention utilizes self-produced reaction heat to perform advanced separation of a reaction liquid, reduces ineffective circulation, and lowers electricity consumption and steam consumption.

Description

Method for synthesizing acetic acid by low-pressure methanol carbonylation

Technical field

The invention relates to a method for synthesizing acetic acid, in particular to a method for synthesizing acetic acid by low-pressure methanol carbonylation.

Background technique

Acetic acid is one of the important organic chemical raw materials, mainly used in the production of vinyl acetate, acetic anhydride, cellulose acetate, acetates, terephthalic acid, chloroacetic acid, etc. It can be widely used in chemicals, light industry, textiles, medicine, etc. Printing and dyeing and other fields. At present, the main methods for producing acetic acid are acetaldehyde oxidation method, olefin direct oxidation method and methanol carbonylation method. Among them, the methanol carbonylation method has the advantages of high methanol conversion rate and small by-products, and has gradually become one of the main methods for producing acetic acid.

The process of methanol carbonylation to produce acetic acid mainly includes two parts: CO gas production and acetic acid production. Taking coke as a raw material to produce CO as an example, the CO gas production part mainly includes gas production, desulfurization, CO ₂ removal, compression and other processes. The acetic acid production part can be further divided into processes such as carbonylation reaction, flash evaporation, distillation high-pressure and low-pressure methyl iodide absorption system, and catalyst preparation.

In the prior art, the reaction of methanol carbonylation to produce acetic acid is based on CO and methanol as raw materials, product acetic acid as solvent, precious metal Ir-Ru or Rh as the main catalyst, and adding methyl iodide, lithium iodide, acetic acid and water to form a homogeneous reaction. Phase catalytic reaction system. The steps of methanol carbonylation to produce acetic acid generally include: methanol and CO are fed into the reactor to contact with the homogeneous catalyst solution, CO and methanol react under the catalysis of the catalyst and the co-catalyst to produce acetic acid, and the heat of reaction is released at the same time. The solution is sent to the flash tower for flash evaporation. After flash evaporation, the mixture is separated into a gas phase component containing acetic acid and a liquid phase component containing the main catalyst. The liquid phase component containing the catalyst is circulated back to the reactor to continue to participate in the reaction, and the gas phase component containing acetic acid is sent to the light The component rectification tower carries out rectification to separate the light components: water, methyl acetate and promoter methyl iodide, and the light components are returned to the reactor through a pump to continue to participate in the reaction. The heavy phase of the light component removal tower mainly contains impurities such as water, acetic acid and propionic acid. This material then enters the dehydration tower for dehydration. After dehydration, it is sent to the heavy component tower to remove propionic acid and other heavy components to obtain the acetic acid product. The flashing efficiency of the existing process is low, the flashing rate is about 20%, and the gasification rate is low, causing the acetic acid to continue to circulate in the reaction liquid, increasing the circulation amount of the mother liquor, and causing the residence time of the reactor to change after the circulation is fast. Short, short residence time will reduce the time-space conversion rate of the catalyst, and the reaction efficiency will be low, so the load is not high; a large amount of flash evaporation will cause the precious metal catalyst to be taken out of the flash vapor phase, causing an increase in loss, an increase in the unit cost of acetic acid, and a large amount of flash After steaming, a large amount of light components (water, methyl iodide, methyl acetate) are returned, which will cause an increase in power consumption.

In the early 1970s, Paulik and others of Monsanto Company's invention of a homogeneous rhodium catalyst for oxo synthesis (US3769329) opened up a new way for the oxo synthesis process. After continuous improvement and perfection, the oxo synthesis technology with rhodium as the catalyst has become the most important and most productive production process route in the acetic acid industry. The reaction process is that methanol reacts with carbon monoxide to produce acetic acid through the action of a rhodium catalyst, and the catalyst adopts [Rh(CO) ₂ I ₂ ]-anionic small molecule complex. The traditional rhodium process requires high water as a stabilizer for the catalyst. Generally, the water in the reaction liquid is 9-14%. The high water in the reaction liquid will cause the steam effect of the subsequent rectification to be high. The traditional acetic acid consumes steam. At 1.5-1.8t/t acetic acid, the large steam consumption causes high production costs of acetic acid, which is not conducive to market competition.

Summary of the invention

The purpose of the present invention is to provide a low-pressure methanol carbonylation method to synthesize acetic acid in order to overcome the above-mentioned defects in the prior art.

The purpose of the present invention can be achieved through the following technical solutions:

A method for low-pressure methanol carbonylation to synthesize acetic acid, including:

(1) In the presence of a catalyst, pass methanol and CO into a non-stirred reactor to carry out the carbonylation reaction, and send the liquid phase part of the middle part of the non-stirred reactor to the flash evaporator for flash evaporation, and separate liquid components and gas phases. Component

(2) The liquid phase component and the mother liquid flash heat exchanger are heat exchanged, and the secondary flash evaporation is performed after heating to separate the secondary liquid phase component and the secondary gas phase component;

(3) The separated primary gas phase and secondary gas phase components are sent to the catalyst trap, the trapped and recovered catalyst is returned to the flash evaporator, and the gas phase components enter the light component rectification tower for rectification and separation to obtain light Components and heavy components;

(4) Return the liquid phase components in steps (1) and (2) to the non-stirred reactor for reaction;

(5) The heavy component in step (3) is sent to the heavy component rectification tower for rectification and separation to obtain an acetic acid product.

The non-stirred reactor adopts a self-operated circulating mixing system. The methanol and liquid phase components are mixed outside the non-stirred reactor to form an external mixed liquid and then enter the reactor. After mixing, the liquid phase components are cooled, and the methanol feed is also The temperature rise is achieved, and the purpose of preheating the feed is achieved;

The CO is injected into the non-stirred reactor at different angles from the external mixed liquid by feeding and ejecting, so that the mixed liquid enters the reactor and turns over to achieve the effect of agitator. The conventional agitated reactor is 200,000-400,000 tons. Take a large-scale acetic acid reactor as an example. The power of the stirrer is 75kw. If it is changed to no stirring, it can save electricity by 75 degrees per hour.

There are three types of heat sources for the flash evaporator:

The reaction liquid from the reactor (the reaction is an exothermic reaction, and the heat needs to be continuously removed during the production process and introduced from the outlet of the external circulation pump;

The steam produced by the external circulation heat exchanger makes full use of its own reaction heat to achieve the purpose of energy saving and consumption reduction;

Steam in the steam pipe network.

Through the combination of the above process conditions, the reaction liquid is deeply separated by its own reaction heat, which reduces ineffective circulation and saves electricity consumption and steam consumption.

The reaction solution in the non-stirring reactor includes the following components and contents by weight: Group VIII metal catalyst 10-21600ppm, water: 2-8, hydrogen iodide: 1-25, methyl iodide: 5-25, iodide Lithium: 1-12, lithium acetate: 0.5-6, methyl acetate: 0.5-25, propionic acid: 20-8000 ppm, acetic acid: 30-80.

The group VIII metal catalyst is selected from one, a combination of two or more of ruthenium, palladium, rhodium, indium, iridium, cobalt or platinum.

The components and contents of the group VIII metal catalyst are preferably the following contents: 100-15000 ppm of iridium, 50-5000 ppm of ruthenium, 50-500 ppm of palladium, 10-200 ppm of platinum, and 50-900 ppm of rhodium.

The components and contents of the Group VIII metal catalyst are preferably the following contents:

Ruthenium: 50-500ppm, Iridium: 500-15000ppm, or,

Rhodium: 50-900ppm, Iridium: 500-15000ppm, or,

Palladium: 50-500ppm, Iridium: 500-15000ppm, or,

Ruthenium: 50-500ppm, Iridium: 500-15000ppm, Rhodium: 50-900ppm, or,

Platinum: 50-500ppm, iridium: 500-15000ppm.

The reaction temperature of the non-stirred reactor is 180-220°C, and the pressure is 2.5-3.4MpaG.

The flash evaporator has a flash temperature of 100-160°C, a pressure of 0.05-0.15MpaG, and a flash ratio (ratio of the amount of flash to the feed methanol) 15-5; the flash temperature of the second flash is 100-160°C, The pressure is 0.05-0.15MpaG.

The light component rectification tower is provided with 40-80 trays, the operating pressure is 0.05-0.30MPaG, the top temperature is 90-140°C, the bottom temperature is 145-165°C, and the reflux ratio is 0.3-1.5.

The heavy component rectification tower is provided with 60-100 trays, the operating pressure is -0.5-0.35MPaG, the top temperature is 80-140°C, the bottom temperature is 145-165°C, and the reflux ratio is 1-4.

Compared with the prior art, the present invention has the following advantages:

(1) The reactants in the reactor adopt two parts: external mixing and internal mixing. The external mixing means that the extracted high-temperature reaction liquid is mixed with the low-temperature feed. After mixing, the reaction liquid is cooled and the feed is heated to achieve The purpose of preheating the feed in advance; the internal mixing is the CO feed injection, entraining the external mixed liquid phase into the reactor through different angles, so that the mixed liquid enters the reactor and then turns over. The combination of equipment and process pipelines achieves no The effect of mixing saves energy consumption.

(2) Use its own reaction heat to deeply separate the reaction liquid, reduce ineffective circulation, and save electricity and steam consumption;

(3) After adopting the catalyst formula, the catalyst concentration is more than 5 times higher than that of the conventional single rhodium catalyst. The conventional rhodium catalyst system: the rhodium concentration is below 800ppm, and the total catalyst concentration is increased to 6000-9000ppm after using the combined catalyst, and the space-time yield is From 7-8mol/(Lh) of conventional rhodium system to 20-35mol/(Lh). Therefore, the output is increased. Ruthenium, palladium, rhodium, iridium, platinum, and indium are added to the conventional rhodium catalyst. After adding other metal catalysts, the two or more metal catalysts complement each other. The activity of the catalyst can still be exerted in water, and the stability is enhanced under the action of the co-catalyst lithium iodide salt, and precipitation is not easy to occur;

(4) The traditional primary flash vaporization rate of acetic acid is 20%. The mother liquor after flash vaporization through the new process exchanges heat with the mother liquor flash vaporization heat exchanger. After heating, the second flash vaporization is performed to increase the vaporization rate of acetic acid from 20%. To 25%, the heat of reaction is removed at the same time. After the flash evaporation rate is improved, the space-time yield of the catalyst can be increased under the same reactor volume by the process, and the output can be increased by 10-30%. At the same time, the heat released by the reaction is utilized without additional consumption. The process is suitable for device expansion The transformation project realizes the utilization of the original reactor.

Description of the drawings

Figure 1 is a process flow diagram of low-pressure methanol carbonylation to synthesize acetic acid.

In the figure, 1-non-stirred reactor, 2-flash evaporator, 3-mother liquor flash heat exchanger, 4-catalyst trap, 5-light component rectification tower, 6-heavy component rectification tower.

detailed description

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be pointed out that for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

A method for synthesizing acetic acid by low-pressure methanol carbonylation. The process flow is shown in Figure 1, and includes the following steps:

(1) In the presence of a catalyst, pass methanol and CO into the non-stirred reactor 1 for the carbonylation reaction. The used non-stirred reactor 1 adopts a self-operated circulating mixing system. The methanol and liquid phase components are in the non-stirred reactor. The external mixture is mixed to form an external mixed liquid and then enters the reactor. After mixing, the liquid phase components are cooled down, and the methanol feed is also heated, achieving the purpose of preheating the feed in advance; CO uses the feed injection method to interact with the external The mixed liquid enters the non-stirred reactor at different angles. The mixed liquid enters the reactor and is turned over to achieve the effect of a stirrer. The conventional agitated reactor is an acetic acid reactor with a scale of 200,000 to 400,000 tons as an example. The power is 75kw. If it is changed to no stirring, it can save electricity 75 degrees per hour. The reaction liquid in the no stirring reactor 1 includes the following components and parts by weight content: Group VIII metal catalyst 10-21600ppm, water: 2-8, Hydrogen iodide: 1-25, methyl iodide: 5-25, lithium iodide: 1-12, lithium acetate: 0.5-6, methyl acetate 0.5-25, propionic acid: 20-8000ppm, acetic acid: 30-80, The above-mentioned group VIII metal catalyst is selected from one, two or more combinations of ruthenium, palladium, rhodium, indium, iridium, cobalt or platinum, and the reaction temperature of the reaction liquid for the carbonylation reaction in the non-stirred reactor 1 is 180 -220℃, pressure 2.5-3.4MpaG, the liquid phase part obtained from the reaction is sent to flash evaporator 2 for flash evaporation, flashing temperature 100-160℃, pressure 0.05-0.15MpaG, flash ratio (flash volume and feed methanol The ratio) 15-5, the liquid phase component and the gas phase component are separated;

(2) The liquid phase component exchanges heat with the mother liquor flash heat exchanger 3, and then flashes twice after heating. The flash temperature of the second flash is 100-160℃, the pressure is 0.05-0.15MpaG, and the second is separated. Liquid phase components and secondary gas phase components;

(3) The separated primary gas phase and secondary gas phase components are sent to the catalyst trap 4, the trapped and recovered catalyst is returned to the flash evaporator 2, and the gas phase components enter the light component rectification tower 5 for rectification and separation , The light fraction rectification tower 5 is equipped with 40-80 trays, the operating pressure is 0.05-0.15MPaG, the top temperature is 90-140℃, the bottom temperature is 145-165℃, and the reflux ratio is 0.3-1.5. Light component and heavy component;

(4) Return the liquid phase components in steps (1) and (2) to the non-stirred reactor 1 for reaction;

(5) The heavy component in step (3) is sent to the heavy component rectification tower 6 for rectification and separation. The heavy component rectification tower 6 is provided with 60-100 trays, and the operating pressure is -0.5-0.2MPaG, The temperature at the top of the tower is 80-140°C, the temperature of the tower bottom is 145-165°C, and the reflux ratio is 1-4 to obtain the acetic acid product.

The following are more detailed implementation cases, and the technical solutions of the present invention and the technical effects that can be obtained are further explained through the following implementation cases.

Example 1

(1) In the presence of a catalyst, pass methanol and CO into the non-stirred reactor 1 for the carbonylation reaction. The used non-stirred reactor 1 adopts a self-operated circulating mixing system. The methanol and liquid phase components are in the non-stirred reactor. The external mixture is mixed to form an external mixed liquid and then enters the reactor. After mixing, the liquid phase components are cooled down, and the methanol feed is also heated, achieving the purpose of preheating the feed in advance; CO uses the feed injection method to interact with the external The mixed liquid enters the non-stirred reactor at different angles, so that the mixed liquid enters the reactor and is turned over to achieve the effect of a stirrer, so that no mechanical stirring or other stirring methods are required, which can save energy. The reaction solution in the non-stirred reactor 1 includes the following components and contents by weight: 60 ppm ruthenium, a group VIII metal catalyst, water 2, hydrogen iodide 1, methyl iodide 5, lithium iodide 1, lithium acetate 0.5, and methyl acetate 0.5 , Propionic acid 20ppm, Acetic acid 30, the reaction liquid in the non-stirred reactor 1 for the carbonylation reaction temperature 180 ℃, pressure 2.5MpaG, the liquid phase obtained by the reaction is sent to the flash evaporator 2 for flashing, the flashing temperature is 100 ℃, pressure 0.05MpaG, flash ratio (ratio of flash volume to feed methanol) 15, separated into liquid phase component and gas phase component;

(2) The liquid phase component exchanges heat with the mother liquor flash heat exchanger 3, and then flashes twice after heating. The flash temperature of the second flash is 100°C, the pressure is 0.05MpaG, and the secondary liquid component is separated. And secondary gas phase components;

(3) The separated primary gas phase and secondary gas phase components are sent to the catalyst trap 4, the trapped and recovered catalyst is returned to the flash evaporator 2, and the gas phase components enter the light component rectification tower 5 for rectification and separation , The light component rectification tower 5 is equipped with 40 trays, the operating pressure is 0.05MPaG, the top temperature is 90°C, the bottom temperature is 145°C, and the reflux ratio is 0.3 to obtain light and heavy components;

(5) The heavy component in step (3) is sent to the heavy component rectification tower 6 for rectification and separation. The heavy component rectification tower 6 is equipped with 60 trays, the operating pressure is -0.5MPaG, and the top temperature is At 80°C, the temperature of the tower bottom is 145°C, and the reflux ratio is 1 to obtain an acetic acid product.

Example 2

(1) In the presence of a catalyst, pass methanol and CO into the non-stirred reactor 1 for the carbonylation reaction. The used non-stirred reactor 1 adopts a self-operated circulating mixing system. The methanol and liquid phase components are in the non-stirred reactor. The external mixture is mixed to form an external mixed liquid and then enters the reactor. After mixing, the liquid phase components are cooled down, and the methanol feed is also heated, achieving the purpose of preheating the feed in advance; CO uses the feed injection method to interact with the external The mixed liquid enters the non-stirred reactor at different angles, so that the mixed liquid enters the reactor and is turned over to achieve the effect of a stirrer, so that no mechanical stirring or other stirring methods are required, which can save energy. The reaction solution in the non-stirred reactor 1 includes the following components and contents by weight: group VIII metal catalyst iridium 100ppm, rhodium 900ppm, water 3, hydrogen iodide 10, methyl iodide 10, lithium iodide 8, lithium acetate 5, acetic acid Methyl 20, propionic acid 1000ppm, acetic acid 40, the reaction liquid is subjected to the carbonylation reaction in the non-stirred reactor 1, the reaction temperature is 200°C, the pressure is 3MpaG, the liquid phase obtained from the reaction is sent to the flash evaporator 2 for flash evaporation, flash evaporation The temperature is 120°C, the pressure is 0.12MpaG, the flash ratio (ratio of the flash volume to the feed methanol) is 10, and the liquid phase component and the gas phase component are separated;

(2) The liquid phase component exchanges heat with the mother liquor flash heat exchanger 3, and then flashes twice after heating. The flash temperature of the second flash is 120℃, the pressure is 0.12MpaG, and the secondary liquid phase component is separated. And secondary gas phase components;

(3) The separated primary gas phase and secondary gas phase components are sent to the catalyst trap 4, the trapped and recovered catalyst is returned to the flash evaporator 2, and the gas phase components enter the light component rectification tower 5 for rectification and separation , The light component rectification tower 5 is equipped with 60 trays, the operating pressure is 0.1MPaG, the top temperature is 100°C, the bottom temperature is 155°C, and the reflux ratio is 0.8 to obtain light and heavy components;

(5) The heavy component in step (3) is sent to the heavy component rectification tower 6 for rectification and separation. The heavy component rectification tower 6 is equipped with 90 trays, the operating pressure is 0.1 MPaG, and the top temperature is 120 ℃, the temperature of the tower kettle is 150℃, and the reflux ratio is 3 to obtain the acetic acid product.

Example 3

(1) In the presence of a catalyst, pass methanol and CO into the non-stirred reactor 1 for the carbonylation reaction. The used non-stirred reactor 1 adopts a self-operated circulating mixing system. The methanol and liquid phase components are in the non-stirred reactor. The external mixture is mixed to form an external mixed liquid and then enters the reactor. After mixing, the liquid phase components are cooled down, and the methanol feed is also heated, achieving the purpose of preheating the feed in advance; CO uses the feed injection method to interact with the external The mixed liquid enters the non-stirred reactor at different angles, so that the mixed liquid enters the reactor and is turned over to achieve the effect of a stirrer, so that no mechanical stirring or other stirring methods are required, which can save energy. The reaction liquid in the non-stirred reactor 1 includes the following components and contents by weight: 500 ppm palladium, a group VIII metal catalyst, 15000 ppm of iridium, 8, hydrogen iodide 25, methyl iodide 25, lithium iodide 12, lithium acetate 6, acetic acid Methyl 25, propionic acid 6000ppm, acetic acid 50, the reaction liquid in the non-stirred reactor 1 for the carbonylation reaction temperature 220 ℃, pressure 3.4MpaG, the liquid phase part obtained by the reaction is sent to the flasher 2 for flashing, flashing Steam temperature is 150°C, pressure is 0.13MpaG, flash ratio (ratio of flash volume to feed methanol) 10, liquid phase component and gas phase component are separated;

(2) The liquid phase component exchanges heat with the mother liquor flash heat exchanger 3, and then flashes twice after heating. The flash temperature of the second flash evaporation is 160℃, the pressure is 0.15MpaG, and the secondary liquid phase component is separated. And secondary gas phase components;

(3) The separated primary gas phase and secondary gas phase components are sent to the catalyst trap 4, the trapped and recovered catalyst is returned to the flash evaporator 2, and the gas phase components enter the light component rectification tower 5 for rectification and separation , The light component rectification tower 5 is equipped with 80 trays, the operating pressure is 0.15MPaG, the top temperature is 140°C, the bottom temperature is 160°C, and the reflux ratio is 1.2 to obtain light and heavy components;

(5) The heavy component in step (3) is sent to the heavy component rectification tower 6 for rectification and separation. The heavy component rectification tower 6 is equipped with 100 trays, the operating pressure is 0.2MPaG, and the top temperature is 140 ℃, the temperature of the tower bottom is 160℃, and the reflux ratio is 4 to obtain the acetic acid product.

Example 4

(1) In the presence of a catalyst, pass methanol and CO into the non-stirred reactor 1 for the carbonylation reaction. The used non-stirred reactor 1 adopts a self-operated circulating mixing system. The methanol and liquid phase components are in the non-stirred reactor. The external mixture is mixed to form an external mixed liquid and then enters the reactor. After mixing, the liquid phase components are cooled down, and the methanol feed is also heated, achieving the purpose of preheating the feed in advance; CO uses the feed injection method to interact with the external The mixed liquid enters the non-stirred reactor at different angles, so that the mixed liquid enters the reactor and is turned over to achieve the effect of a stirrer, so that no mechanical stirring or other stirring methods are required, which can save energy. The reaction solution in the non-stirred reactor 1 includes the following components and contents by weight: Group VIII metal catalyst iridium 100ppm, ruthenium 5000ppm, palladium 100ppm, platinum 10ppm, rhodium 50ppm, water 6, hydrogen iodide 22, methyl iodide 20, iodine Lithium 6, Lithium Acetate 0.8, Methyl Acetate 20, Propionic Acid 8000ppm, Acetic Acid 80, the reaction solution is carbonylation reaction temperature 190℃, pressure 3MpaG in the non-stirred reactor 1, the liquid phase part obtained from the reaction is fed into Flash evaporator 2 performs flash evaporation, flashing temperature is 160°C, pressure is 0.15MpaG, flashing ratio (ratio of flashing volume to feed methanol) 5, and separating liquid and gaseous components;

(2) The liquid phase component exchanges heat with the mother liquor flash heat exchanger 3, and then flashes twice after heating. The flash temperature of the second flash is 130°C, the pressure is 0.1MpaG, and the secondary liquid component is separated. And secondary gas phase components;

(3) The separated primary gas phase and secondary gas phase components are sent to the catalyst trap 4, the trapped and recovered catalyst is returned to the flash evaporator 2, and the gas phase components enter the light component rectification tower 5 for rectification and separation , The light component rectification tower 5 is equipped with 50 trays, the operating pressure is 0.1MPaG, the top temperature is 100°C, the bottom temperature is 165°C, and the reflux ratio is 1.5 to obtain light and heavy components;

(5) The heavy component in step (3) is sent to the heavy component rectification tower 6 for rectification and separation. The heavy component rectification tower 6 is equipped with 100 trays, the operating pressure is -0.3MPaG, and the top temperature is 100°C, tower bottom temperature of 165°C, reflux ratio of 2 to obtain acetic acid product.

Example 5

A method for synthesizing acetic acid by low-pressure methanol carbonylation. The process flow is roughly the same as that of Example 3. The difference is that in the reaction solution used in this example, the composition and content of the Group VIII metal catalyst is 100 ppm ruthenium and 100 ppm iridium. 500ppm, rhodium 50ppm.

Example 6

A low-pressure methanol carbonylation method to synthesize acetic acid. The process flow is roughly the same as that of Example 3. The difference is that in the reaction solution used in this example, the component and content of the Group VIII metal catalyst is 500 ppm platinum and 500 ppm iridium. 15000ppm.

Example 7

A method for low-pressure methanol carbonylation to synthesize acetic acid. The process flow is roughly the same as that of Example 4. The difference is that in the reaction solution used in this example, the component and content of the Group VIII metal catalyst is 50 ppm rhodium and 50 ppm iridium. 15000ppm.

Example 8

A method for low-pressure methanol carbonylation to synthesize acetic acid. The process flow is roughly the same as that of Example 4. The difference is that in the reaction solution used in this example, the composition and content of the Group VIII metal catalyst is 50 ppm ruthenium and 50 ppm iridium. 500ppm, rhodium 50ppm.

Example 9

Using the process scheme of Example 4, based on the existing 200,000 tons of reactor volume, after using the new catalyst, the output of the reaction volume can be increased to 500,000 tons of production capacity.

Advantages: a. The main catalyst is cheap; b. The stability is good. It can maintain a higher catalyst concentration (2000-8000ppm) and has a higher space-time yield of 20-35mol acetic acid/(Lh); c. Investment cost savings 10-30%; d. Because the water concentration in the system is reduced to 1-8wt%, the by-product propionic acid is less, so the consumption of public works is reduced by 20-50%; e. Using this technology, the original device capacity can be increased by 35% the above.

In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific feature, structure, material, or characteristic described in combination with the embodiment or example is included in the utility model. In at least one embodiment or example. In this specification, the schematic representation of the above-mentioned terms does not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner.

The above description of the embodiments is to facilitate those of ordinary skill in the technical field to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described here to other embodiments without creative work. Therefore, the present invention is not limited to the above-mentioned embodiments. According to the disclosure of the present invention by those skilled in the art, all improvements and modifications made without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

A method for low-pressure methanol carbonylation to synthesize acetic acid, characterized in that the method comprises:

(1) In the presence of a catalyst, pass methanol and CO into a non-stirred reactor to carry out the carbonylation reaction, and send the liquid phase part of the middle part of the non-stirred reactor to the flash evaporator for flash evaporation, and separate liquid components and gas phases. Component

(2) The liquid phase component and the mother liquid flash heat exchanger are heat exchanged, and the secondary flash evaporation is performed after heating to separate the secondary liquid phase component and the secondary gas phase component;

(3) The separated primary gas phase and secondary gas phase components are sent to the catalyst trap, the trapped and recovered catalyst is returned to the flash evaporator, and the gas phase components enter the light component rectification tower for rectification and separation to obtain light Components and heavy components;

(4) Return the liquid phase components in steps (1) and (2) to the non-stirred reactor for reaction;

(5) The heavy component in step (3) is sent to the heavy component rectification tower for rectification and separation to obtain an acetic acid product.
The method for synthesizing acetic acid by low-pressure methanol carbonylation according to claim 1, characterized in that the non-stirred reactor adopts a self-operated circulating mixing system, and methanol and liquid phase components are mixed outside the non-stirred reactor to form an external After the mixed liquid enters the reactor, the CO is injected into the non-stirred reactor at different angles from the external mixed liquid by means of feed injection.
The method for synthesizing acetic acid by low-pressure methanol carbonylation according to claim 1, wherein the reaction liquid in the non-stirred reactor comprises the following components and parts by weight content: Group VIII metal catalyst 10-21600 ppm, water : 2-8, hydrogen iodide: 1-25, methyl iodide: 5-25, lithium iodide: 1-12, lithium acetate: 0.5-6, methyl acetate 0.5-25, propionic acid: 20-8000ppm, acetic acid : 30-80.
The method for synthesizing acetic acid by low-pressure methanol carbonylation according to claim 1, wherein the group VIII metal catalyst is selected from one or two of ruthenium, palladium, rhodium, indium, iridium, cobalt or platinum Or a combination of multiple.
The method for synthesizing acetic acid by low-pressure methanol carbonylation according to claim 4, characterized in that the components and content of the group VIII metal catalyst are preferably the following content: iridium 100-15000ppm, ruthenium 50-5000ppm, palladium 50 -500ppm, platinum 10-200ppm, rhodium 50-900ppm.
The method for synthesizing acetic acid by low-pressure methanol carbonylation according to claim 4 or 5, wherein the components and content of the group VIII metal catalyst are preferably the following content:

Ruthenium: 50-500ppm, Iridium: 500-15000ppm, or,

Rhodium: 50-900ppm, Iridium: 500-15000ppm, or,

Palladium: 50-500ppm, Iridium: 500-15000ppm, or,

Ruthenium: 50-500ppm, Iridium: 500-15000ppm, Rhodium: 50-900ppm, or,

Platinum: 50-500ppm, iridium: 500-15000ppm.
The method for synthesizing acetic acid by low-pressure methanol carbonylation according to claim 1, wherein the reaction temperature of the non-stirred reactor is 180-220°C and the pressure is 2.5-3.4MpaG.
A method of low-pressure methanol carbonylation to synthesize acetic acid according to claim 1, characterized in that the flash temperature of the flash evaporator is 100-160°C, the pressure is 0.05-0.15MpaG, and the flash ratio (flash volume and intake The ratio of feed methanol) 15-5; the flashing temperature of the second flashing is 100-160℃, and the pressure is 0.05-0.15MpaG.
The method for synthesizing acetic acid by low-pressure methanol carbonylation according to claim 1, wherein the light component rectification tower is provided with 40-80 trays, the operating pressure is 0.05-0.30MPaG, and the tower top temperature It is 90-140°C, the tower bottom temperature is 145-165°C, and the reflux ratio is 0.3-1.5.
The method for synthesizing acetic acid by low-pressure methanol carbonylation according to claim 1, wherein the heavy component rectification tower is provided with 60-100 trays, the operating pressure is -0.5-0.35MPaG, and the top temperature It is 80-140℃, the temperature of the tower bottom is 145-165℃, and the reflux ratio is 1-4.