WO2024040783A1 - Method and system for preparing acetic acid by regulating and controlling methanol carbonylation - Google Patents

Abstract

The present invention provides a method and system for preparing acetic acid by regulating and controlling methanol carbonylation. The method comprises: producing acetic acid by using a methanol carbonylation method, and when a stable state of a catalyst is kept, regulating and controlling the yield of the acetic acid by regulating and controlling one or more selected from rhodium concentration, lithium iodide concentration, and a flash evaporation temperature. The present invention provides a method and system for preparing acetic acid by regulating and controlling methanol carbonylation, and relates to a continuous production method and device; the flash evaporation efficiency is high and controllable, a catalyst system is stable, and the accumulation of byproducts in the system can be effectively prevented.

Description

A method and system for regulating the carbonylation of methanol to prepare acetic acid Technical field

The invention relates to the field of large-scale chemical production, and in particular to a method and system for regulating the carbonylation of methanol to prepare acetic acid.

Background technique

Acetic acid, i.e. acetic acid, is an important raw material widely used in chemical industry, medicine, textile and other fields. The industrial production methods of acetic acid mainly include fermentation, liquid phase oxidation of low carbon alkanes, acetaldehyde oxidation, direct oxidation of ethylene and methanol carbonylation. Among them, the methanol carbonylation method has the advantages of high methanol conversion rate and low by-products, and has become one of the main methods for producing acetic acid.

The reaction of methanol carbonylation to produce acetic acid uses CO and methanol as raw materials, the product acetic acid as solvent, the precious metal rhodium, Rh, as the main catalyst, methyl acetate, methyl iodide, lithium iodide, acetic acid and water as auxiliaries, and the composition is uniform Phase catalytic reaction system. According to the water content in the reaction system, it can be divided into high water method and low water method. In the high water method, the water content is about 14 to 15%. In the low water method, patents such as Celanese pointed out that when the reaction system has a low water concentration, such as 4% or less, by adding lithium iodide substances, the catalyst stability and reaction rate are maintained at a high level. That is, the catalyst does not precipitate at lower water concentrations. However, at such a low water concentration, the impurity content in acetic acid products is increased, such as propionic acid, acetaldehyde, and aldehydes and ketones derived from acetaldehyde (such as acetone, methyl ethyl ketone, butyraldehyde, crotonaldehyde, 2 -Ethylcrotonaldehyde, 2-ethylbutyraldehyde) and multi-carbon alkyl iodides, etc. The steps for the carbonylation of methanol to produce acetic acid generally include: feeding methanol and CO into a reactor to contact with a homogeneous catalyst solution, and reacting at a temperature of 175-200°C, a total pressure of 2.8-3Mpa, and a carbon monoxide partial pressure of 1-1.5Mpa. Under the catalytic action of the catalyst and cocatalyst, acetic acid is generated, and at the same time, the heat of reaction (about 117kJ/mol) is released. The gas discharged from the top of the reactor contains carbon monoxide, methyl iodide, hydrogen and methane and is sent to the tail gas scrubber. The reaction liquid is drawn out from the side line of the reactor, and the reacted solution is sent to the flash evaporation 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 mother liquor containing the catalyst is recycled back to the reactor to continue participating in the reaction, and the gas phase component containing acetic acid is sent to the light removal tower. Distillation is carried out to separate the light components (after layering, they mainly include upper layer water, methyl acetate, and lower layer cocatalyst methyl iodide), and the light components are returned to the reactor through a pump to continue participating in the reaction. The non-condensable gas at the top of the light removal tower (containing methyl iodide, methyl acetate, and a small amount of methanol) enters the scrubber tower through the condensation tank of the distillation tower. The heavy phase of the light component removal tower mainly contains impurities such as water, acetic acid and propionic acid and enters the dehydration tower for dehydration. After dehydration, it is sent to the weight removal tower to remove propionic acid and other heavy components to obtain an acetic acid product. The combined gases discharged from each distillation tower and reaction kettle have a composition of CO 40-80%, including H ₂ , CO ₂ , CH ₄ and trace amounts of acetic acid and methyl iodide, which are together washed and recovered with cold methanol in the tail gas scrubber. After iodine is burned and vented. A large number of useful components (CO, _H2, etc.) in the exhaust gas have not been effectively utilized, which is not conducive to reducing production costs, and the large amount of greenhouse gases produced by incineration has caused environmental pollution.

The rhodium-based catalyst mentioned above is unstable in high temperature or low CO partial pressure environments and is prone to generate trivalent rhodium precipitation. In fact, the existing process uses a lower temperature during flash evaporation, such as lower than 150°C, which results in low flash evaporation efficiency and low gasification rate. It increases the circulation volume of acetic acid mother liquor, leads to higher system energy consumption, and reduces Reaction efficiency is low. At the same time, since a large amount of light components (water, methyl iodide, methyl acetate) must be recycled after flash evaporation, power consumption will also increase. All these make the product less competitive in the market.

In order to solve the above problems, patent CN111646894A discloses a method for synthesizing acetic acid through low-pressure carbonylation of methanol. The liquid phase part in the reactor is sent to a flash evaporator for flash evaporation, and the liquid phase component and the gas phase component are separated; the liquid phase component is The fraction is then flashed twice to separate the secondary liquid phase component and the secondary gas phase component; all the above liquid phase components are recycled back to the reactor for reaction; all the gas phase components enter the light component rectification tower for processing Distillation and separation are performed to obtain light components and heavy components; the heavy components are sent to the heavy component distillation tower for distillation and separation to obtain acetic acid products. Although this method deepens the separation and reduces ineffective cycles through secondary flash evaporation, the high temperature and low CO partial pressure during the flash evaporation process will cause the deactivation and precipitation of the rhodium catalyst, reducing the catalyst concentration and catalytic efficiency as well as the yield of acetic acid.

Patent CN114133324A discloses a method to deeply utilize tail gas and improve flash evaporation efficiency. By performing first-level flash evaporation on part of the liquid phase in the first-level reactor, the gas phase components generated by flash evaporation are sent to the light removal tower for subsequent acetic acid purification. After treatment, the flashed liquid phase is sent to the secondary reactor. The gas phase components discharged from the top of the primary reactor and the tail gas components of the light removal tower (including CO and other components) are returned to the secondary reactor for secondary reaction, that is, deep reaction, so that a large amount of CO (tail gas) present in the tail gas components is The medium CO content is 40-80%) can be further utilized to improve the utilization rate of CO in the reaction system. At the same time, the methyl acetate and cocatalysts such as methyl iodide present in the tail gas components can be further brought into the reaction system to reduce the subsequent tail gas Absorb system load and avoid environmental pollution caused by exhaust gas venting and incineration. Part of the liquid phase in the secondary reactor is sent to the secondary flash evaporation, the generated gas phase is sent to the light removal tower for subsequent acetic acid purification, and the flashed liquid phase is returned to the primary reactor. After secondary flash evaporation, this invention improves the separation efficiency of the system, reduces the circulation volume of mother liquor, reduces the energy consumption of the system and the content of by-products, and increases the acetic acid yield of the system. However, in this patent, since the concentrated high-concentration acetaldehyde is returned to the reactor, not only the removal amount of acetaldehyde is reduced, the acetaldehyde removal efficiency is reduced, but also the acetaldehyde in the reaction solution is reduced. As the concentration increases, the amount of impurities derived from acetaldehyde increases. Moreover, in the flash evaporation process, sufficient CO partial pressure cannot be ensured to keep the rhodium-based catalyst stable, which has the same problem as the above-mentioned patent CN111646894A.

Contents of the invention

In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a method and system for the continuous production of acetic acid through the carbonylation of methanol with high and controllable flash evaporation efficiency, stable catalyst system and preventing the accumulation of by-products in the system. To solve the problems in the existing technology.

In order to achieve the above objects and other related objects, the present invention is obtained through the following technical solutions.

The first aspect of the present invention discloses a method for regulating the carbonylation of methanol to produce acetic acid. The methanol carbonylation method is used to produce acetic acid. While maintaining the stable state of the catalyst, the method is selected from the group consisting of rhodium concentration, lithium iodide concentration and flash evaporation temperature. One or more to control acetic acid yield.

According to the technical solution of the present application, the method is a continuous production method.

According to the technical solution of the present application, in the stable state of the catalyst, the rhodium concentration, lithium iodide concentration and flash evaporation temperature are all proportional to the acetic acid yield.

Preferably, the methanol carbonylation method uses CO and methanol as raw materials, the product acetic acid as a solvent, a rhodium-based catalyst as the main catalyst, methyl acetate, methyl iodide, lithium iodide, acetic acid and water as auxiliaries, and the composition is homogeneous. Catalytic reaction system.

According to the technical solution of the present application, the process of producing acetic acid using the methanol carbonylation method includes reaction, flash evaporation, light removal, dehydration and weight removal.

According to the technical solution of the present application, the stable state of the catalyst means that the catalyst does not precipitate, and maintaining the stability of the catalyst is achieved through certain flash evaporation conditions; the certain flash evaporation conditions means that the flash evaporation temperature is less than 160°C, or the flash evaporation temperature is less than 160°C. When the temperature is not less than 160°C, gas containing CO is introduced into the flash evaporation system. Add fresh CO to the flash evaporation system, such as the bottom of the flash tank, to increase the stability of the catalyst so that it does not precipitate at higher temperatures of 160 to 180°C, thus increasing the temperature from the traditional about 140°C to 160 to 160°C in the flash evaporation step. At 180°C, the flash evaporation efficiency is increased to achieve the purpose of increasing production and removing the reaction heat at the same time.

According to the technical solution of the present application, the feed molar ratio of methanol to CO is 1: (1-1.5).

According to the technical solution of the present application, the amount of methanol used is 10 to 20 wt% of the total mass of the homogeneous catalytic reaction system.

According to the technical solution of the present application, the rhodium-based catalyst is rhodium iodide.

According to the technical solution of the present application, based on the total mass of the homogeneous catalytic reaction system, the amount of the rhodium-based catalyst is 500 to 3000 ppm.

According to the technical solution of the present application, the amount of water used is 2 to 5 wt% of the total mass of the homogeneous catalytic reaction system.

According to the technical solution of the present application, the amount of methyl iodide used is 0.1 to 4 wt% of the total mass of the homogeneous catalytic reaction system. The method in this application reduces the dosage of methyl iodide and reduces the ineffective evaporation and circulation of methyl iodide in the system.

According to the technical solution of the present application, the amount of lithium iodide used is 5 to 20 wt% of the total mass of the homogeneous catalytic reaction system.

According to the technical solution of the present application, the dosage of methyl acetate is 1 to 5 wt% of the total mass of the homogeneous catalytic reaction system.

According to the technical solution of the present application, the amount of acetic acid used is 30 to 80 wt% of the total mass of the homogeneous catalytic reaction system.

According to the technical solution of the present application, the flash evaporation temperature is 100-180°C.

According to the technical solution of this application, the flash pressure is 0.05-0.35Mpa.

According to the technical solution of the present application, the reaction includes a first-level reaction and a second-level reaction. The homogeneous catalytic reaction system is subjected to a first-level reaction to obtain the first-level reaction gas phase components and the first-level reaction liquid phase components; The overflow liquid phase of the reaction serves as the liquid phase of the secondary reaction, and the gas phase components of the secondary reaction include non-condensable gases discharged from other steps. According to the technical solution of the present application, the temperature of the first-stage reaction is 180-200°C, and the pressure is 2.5-3MPa.

According to the technical solution of the present application, the temperature of the secondary reaction is 160-180°C, and the pressure is 2.5-3MPa. According to the technical solution of this application, the partial pressure of CO in the secondary reaction is not less than 1.5MPa.

According to the technical solution of the present application, the liquid phase produced by the secondary reaction is flash evaporated.

According to the technical solution of the present application, the gas phase components produced by flash evaporation are delighted.

According to the technical solution of the present application, the liquid phase generated by the flash evaporation enters the reaction system for circulation reaction.

According to the technical solution of the present application, the CO in the flash evaporation system includes CO-containing non-condensable gas discharged from other steps.

According to the technical solution of the present application, the flash evaporation is performed in a flash tank.

According to the technical solution of the present application, the light removal is carried out in a light removal tower, and the light removal tower is a plate tower or a packed tower.

According to the technical solution of the present application, the low-boiling-point fraction separated by light removal is separated into phases after condensation, and the liquid phase obtained by phase-separation is recycled. The low-boiling-point fraction includes one selected from the group consisting of methyl iodide, methyl acetate and acetaldehyde. Kind or variety.

According to the technical solution of the present application, the high boiling point fraction separated by light removal is recycled in the reaction step, and the high boiling point fraction includes water, acetic acid, propionic acid and lithium iodide.

According to the technical solution of the present application, the acetic acid obtained by lightening is dehydrated to remove water.

According to the technical solution of the present application, the dehydration is performed in a dehydration tower, which is a plate tower or a packed tower.

According to the technical solution of the present application, the degravity is carried out in a degravity tower, which is a plate tower or a packed tower.

According to the technical solution of the present application, the process parameters of the plate tower in the light removal process are selected from one or more of the following: the number of theoretical plates is 5 to 45; the reflux ratio is 0.5 to 5; the tower top temperature is 90～130℃, gauge pressure is 80～160kPa; tower reactor temperature is 130～160℃, gauge pressure is 85～180kPa.

According to the technical solution of the present application, the process parameters of the plate tower in the dehydration process are selected from one or more of the following: the number of theoretical plates is 5 to 45; the reflux ratio is 0.5 to 5; the tower top temperature is 130 to 150℃, the gauge pressure is 150~250kPa; the tower kettle temperature is 150~180℃, the gauge pressure is 200~300kPa.

According to the technical solution of the present application, the process parameters of the plate tower in the deduplication process are selected from one or more of the following: the number of theoretical plates is 5 to 45, the reflux ratio is 0.5 to 5; the tower top temperature is 60 ~160℃, the gauge pressure is -100~150kPa; the tower kettle temperature is 80~180℃, the gauge pressure is -90~190kPa; acetic acid is extracted from the middle part of the degravity tower in the degravity process.

A second aspect of the present invention discloses a system for regulating the carbonylation of methanol to produce acetic acid. The system at least includes a primary reaction kettle, a secondary reaction kettle, a flash tank and a light removal tower that are connected in sequence through pipeline materials.

In one embodiment, the first-stage reaction kettle includes a first condenser and a first heat exchanger; the first condenser is used to condense the top gas flow of the first-stage reaction kettle; the first heat exchanger The device acts on the first-level reactor.

In one embodiment, the secondary reactor includes a second condenser and a second heat exchanger. The second condenser is used to condense the top gas flow of the secondary reactor. The second heat exchanger The device acts on the secondary reactor.

In one embodiment, the light removal tower includes a third condenser, a third heat exchanger and a phase separator; the third condenser is used to condense the overhead fraction of the light removal tower; the third heat exchanger Acting on the light removal tower; the phase separator is located downstream of the third condenser and is in fluid communication with the third condenser through a pipeline.

In one embodiment, a first liquid outlet is provided in the middle of the primary reactor, and the first liquid outlet is connected to the feed port of the secondary reactor through a pipeline.

In one embodiment, a second liquid outlet is provided in the middle of the secondary reactor, and the second liquid outlet is connected to the flash tank through a pipeline.

In one embodiment, the first condenser is provided with a first outlet and a first liquid return pipe connected to the first-stage reactor.

In one embodiment, the second condenser is provided with a second outlet and a second liquid return pipe connected to the secondary reactor.

In one embodiment, the third condenser is provided with a third non-condensable gas discharge port.

In one embodiment, the phase separator is provided with an upper liquid reflux pipe and/or a lower liquid reflux pipe connected to the light removal tower.

In one embodiment, a first gas-liquid separation tank is further included. The first gas-liquid separation tank is in fluid communication with the first outlet of the first condenser. The first gas-liquid separation tank is provided with a first row. The liquid port and the first exhaust port are connected with the first liquid return pipe.

In one embodiment, a second gas-liquid separation tank is further included. The second gas-liquid separation tank is in fluid communication with the second outlet of the second condenser. The second gas-liquid separation tank is provided with a second row. a liquid port and a second exhaust port, and the second liquid exhaust port is connected to the second liquid return pipe.

In one embodiment, it also includes a dehydration tower located downstream of the light removal tower and in communication with the material of the light removal tower.

In one embodiment, several fresh CO feed channels are also included, and the fresh CO feed channels are connected to the bottom of the primary reactor, the secondary reactor or the flash tank.

In one embodiment, the dehydration tower is provided with a fourth condenser and a fourth heat exchanger; the fourth condenser is used to condense the top gas flow of the dehydration tower, and the fourth heat exchanger acts on The dehydration tower.

In one embodiment, a degravity tower is also provided downstream of the dehydration tower, and the degravity tower is in material communication with the dehydration tower.

In one embodiment, the fourth condenser is provided with a fourth non-condensable gas outlet and a third liquid return pipe connected to the dehydration tower.

In one embodiment, the degravity tower is provided with a fifth condenser and a fifth heat exchanger, and the fifth condenser is used to condense the top gas flow of the degravity tower; the fifth heat exchanger Act on the degravity tower.

In one embodiment, the fifth condenser is provided with a fifth non-condensable gas outlet and a fourth liquid return pipe connected with the degravity tower.

In one embodiment, it also includes a heavy component reflux pipe, one end of which is respectively connected to a flash tank, a light removal tower, the phase separator, the fourth condenser, and the fifth condenser. One or more connections are connected, and the other end is connected with the first-level reactor.

In one embodiment, the system further includes a non-condensable gas pipeline selected from the first exhaust port of the first condenser, the second exhaust port, and the third non-condensable gas outlet of the third condenser. One or more of the gas discharge port, the fourth non-condensable gas discharge port of the fourth condenser, and the fifth non-condensable gas discharge port of the fifth condenser are connected to one end of the non-condensable gas pipeline, and the The other end of the non-condensable gas pipeline is connected to the secondary reaction kettle and/or the flash tank.

The invention provides a method and system for regulating the carbonylation of methanol to prepare acetic acid. It is a continuous production method and production device. The flash evaporation efficiency is high and controllable, the catalyst system is stable, and the by-products can be effectively prevented from entering the system. accumulated within.

Description of drawings

Figure 1 shows a schematic diagram of one embodiment of the control method of the present invention.

Figure 2 shows one of the schematic diagrams of an implementation method of the method in the embodiment of the present invention.

Figure 3 shows the second schematic diagram of the implementation of the method in the embodiment of the present invention.

Figure 4 shows the relationship between rhodium concentration, lithium iodide concentration, flash evaporation temperature and acetic acid yield in the present invention.

The labels in Figures 1 to 3 are explained as follows:

1 First level reactor 1a first condenser 1b first heat exchanger 1c The first gas-liquid separation tank 2 Secondary reactor 2a Second condenser 2b Second heat exchanger 2c Second gas-liquid separation tank 3 flash tank

4 Tuo Qing Pagoda 4a Third condenser 4b Third heat exchanger 4c phase separator 5 Dehydration tower 5a Fourth condenser 5b Fourth heat exchanger 6 weight removal tower 6a Fifth condenser 6b Fifth heat exchanger

Detailed ways

The implementation of the present invention is described below with specific embodiments. Those familiar with this technology can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

Before further describing the specific embodiments of the present invention, it should be understood that the protection scope of the present invention is not limited to the following specific specific embodiments; it should also be understood that the terms used in the embodiments of the present invention are for describing specific specific embodiments, It is not intended to limit the scope of the present invention. Test methods without specifying specific conditions in the following examples usually follow conventional conditions or conditions recommended by each manufacturer.

When the examples give numerical ranges, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints can be selected. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, equipment, and materials used in the embodiments, those skilled in the art can also use methods, equipment, and materials described in the embodiments of the present invention based on their understanding of the prior art and the description of the present invention. Any methods, equipment and materials similar or equivalent to those in the prior art may be used to implement the present invention.

The embodiments of the present invention provide a specific method for regulating the carbonylation of methanol to produce acetic acid. The methanol carbonylation method is used to produce acetic acid. While maintaining the stable state of the catalyst, the method is selected from the group consisting of rhodium concentration, lithium iodide concentration and flash temperature. One or more of them are used to regulate acetic acid yield. The applicant has confirmed the methods and key technical means to keep the catalyst in a stable state through extensive practice, and found that in the stable state of the catalyst, the rhodium concentration, lithium iodide concentration and flash evaporation temperature are all proportional to the acetic acid yield.

In a preferred embodiment, the methanol carbonylation method uses CO and methanol as raw materials, the product acetic acid as a solvent, a rhodium-based catalyst as the main catalyst, and methyl acetate, methyl iodide, lithium iodide, acetic acid and water as auxiliary agents. agent to form a homogeneous catalytic reaction system.

In a preferred embodiment, the process of producing acetic acid by methanol carbonylation includes reaction, flash evaporation, light removal, dehydration and weight removal.

In a preferred embodiment, the stable state of the catalyst means that the catalyst does not precipitate, and maintaining the stability of the catalyst is achieved through certain flash evaporation conditions; the certain flash evaporation conditions means that the flash evaporation temperature is less than 160°C, or When the flash evaporation temperature is not less than 160°C, gas containing CO is introduced into the flash evaporation system. Add fresh CO to the flash evaporation system, such as the bottom of the flash tank, to increase the stability of the catalyst so that it does not precipitate at higher temperatures of 160 to 180°C, thus increasing the temperature from the traditional about 140°C to 160 to 160°C in the flash evaporation step. At 180°C, the flash evaporation efficiency is increased to achieve the purpose of increasing production and removing the reaction heat at the same time.

In a preferred embodiment, the feed molar ratio of methanol to CO is 1: (1-1.5).

In a preferred embodiment, the amount of methanol used is 10 to 20 wt% of the total mass of the homogeneous catalytic reaction system.

In a preferred embodiment, the rhodium-based catalyst is rhodium iodide.

In a preferred embodiment, based on the total mass of the homogeneous catalytic reaction system, the amount of the rhodium-based catalyst is 500 to 3000 ppm. For example, it can be 500ppm～600ppm, 600ppm～700ppm, 700ppm～800ppm, 800ppm～900ppm, 900ppm～1000ppm, 1000ppm～1100ppm, 1100ppm～1200ppm, 1200ppm～1300ppm, 1300ppm～1400ppm, 1400 ppm～1500ppm, 1500ppm～1600ppm, 1600ppm～1700ppm , 1700ppm～1800ppm, 1800ppm～1900ppm, 1900ppm～2000ppm, 2000～2100ppm, 2100～2200ppm, 2200～2300ppm, 2300～2400ppm, 2400～2500ppm, 2500～2600ppm, 2600～270 0ppm, 2700～2800ppm, 2800～2900ppm or 2900 ~3000ppm. When other production conditions remain unchanged, the greater the amount of rhodium catalyst used, the higher the acetic acid yield.

In a preferred embodiment, the amount of water used is 2 to 5 wt% of the total mass of the homogeneous catalytic reaction system.

In a preferred embodiment, the amount of methyl iodide used is 0.1 to 4 wt% of the total mass of the homogeneous catalytic reaction system. The method in this application reduces the dosage of methyl iodide and reduces the ineffective evaporation and circulation of methyl iodide in the system.

In a preferred embodiment, the amount of lithium iodide used is 5 to 20 wt% of the total mass of the homogeneous catalytic reaction system. For example, it can be 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt% or 20wt% . When other production conditions remain unchanged, the greater the dosage of lithium iodide, the higher the acetic acid yield.

In a preferred embodiment, the amount of methyl acetate used is 1 to 5 wt% of the total mass of the homogeneous catalytic reaction system.

In a preferred embodiment, the amount of acetic acid used is 30 to 80 wt% of the total mass of the homogeneous catalytic reaction system.

In a preferred embodiment, the flash evaporation temperature is 100 to 180°C. For example, it can be 100℃～110℃, 110℃～120℃, 120℃～130℃, 130℃～140℃, 140℃～150℃, 150℃～160℃, 160℃～170℃ or 170℃～180℃ . When other production conditions remain unchanged, the higher the flash evaporation temperature, the higher the acetic acid yield.

In a preferred embodiment, the flash pressure is 0.05-0.35Mpa.

In a preferred embodiment, the reaction includes a primary reaction and a secondary reaction, and the homogeneous catalytic reaction system is subjected to a primary reaction to obtain a primary reaction gas phase component and a primary reaction liquid phase component; The overflow liquid phase of the primary reaction serves as the liquid phase of the secondary reaction, and the gas phase components of the secondary reaction include non-condensable gases discharged from other steps.

In a preferred embodiment, the temperature of the first-stage reaction is 180-200°C, and the pressure is 2.5-3MPa.

In a preferred embodiment, the temperature of the secondary reaction is 160-180°C, and the pressure is 2.5-3MPa.

In a preferred embodiment, the CO partial pressure in the secondary reaction is not less than 1.5MPa.

In a preferred embodiment, the liquid phase produced by the secondary reaction is flash evaporated.

In a preferred embodiment, the gas phase components produced by flash evaporation are delighted.

In a preferred embodiment, the liquid phase generated by flash evaporation enters the reaction system for circulation reaction.

In a preferred embodiment, the CO in the flash evaporated system includes CO-containing non-condensable gas discharged from other steps.

In a preferred embodiment, the flash evaporation is performed in a flash tank.

In a preferred embodiment, the lightening is carried out in a lightening tower, and the lightening tower is a plate tower or a packed tower.

In a preferred embodiment, the low-boiling-point fraction separated by light removal is condensed and then phase-separated, and the liquid phase obtained by phase-separation is recycled. The low-boiling-point fraction is selected from the group consisting of methyl iodide, methyl acetate, and acetaldehyde. of one or more.

In a preferred embodiment, the high boiling point fraction separated by light removal is recycled in the reaction step, and the high boiling point fraction includes water, acetic acid, propionic acid and lithium iodide.

In a preferred embodiment, the acetic acid obtained by lightening is dehydrated to remove water.

In a preferred embodiment, the dehydration is performed in a dehydration tower, which is a plate tower or a packed tower.

In a preferred embodiment, the degravity is carried out in a degravity tower, which is a plate tower or a packed tower.

In a preferred embodiment, the process parameters of the plate tower in the light removal process are selected from one or more of the following: the number of theoretical plates is 5 to 45; the reflux ratio is 0.5 to 5; the tower top The temperature is 90~130℃, and the gauge pressure is 80~160kPa; the temperature of the tower kettle is 130~160℃, and the gauge pressure is 85~180kPa.

In a preferred embodiment, the process parameters of the plate tower in the dehydration process are selected from one or more of the following: the number of theoretical plates is 5 to 45; the reflux ratio is 0.5 to 5; the tower top temperature is 130～150℃, the gauge pressure is 150～250kPa; the tower kettle temperature is 150～180℃, the gauge pressure is 200～300kPa.

In a preferred embodiment, the process parameters of the plate tower in the deduplication process are selected from one or more of the following: the number of theoretical plates is 5 to 45, the reflux ratio is 0.5 to 5; the tower top temperature The temperature is 60~160℃, the gauge pressure is -100~150kPa; the tower kettle temperature is 80~180℃, the gauge pressure is -90~190kPa; acetic acid is extracted from the middle part of the degravity tower in the degravity process.

As shown in Figures 1 to 3, embodiments of the present invention also provide a specific system for regulating the carbonylation of methanol to produce acetic acid. The system at least includes a primary reactor 1 and a secondary reactor 2 that are connected in sequence through pipelines. , flash tank 3 and light removal tower 4. In this application, by setting up a two-stage reactor and combining it with a flash tank and a light removal tower, the temperature of each process can be effectively adjusted to ensure the stable state of the catalyst.

In a preferred embodiment as shown in Figures 1 to 3, the first-stage reactor 1 includes a first condenser 1a and a first heat exchanger 1b; the first condenser 1a is used to condense the The top gas flow of the first-stage reaction kettle 1 is condensed; the first heat exchanger 1b acts on the first-stage reaction kettle 1 . The first condenser 1a processes the light components of the primary reactor 1 to form liquid and non-condensable gas for reflux, thereby realizing the recovery and reuse of the light components.

In a preferred embodiment as shown in Figures 1 to 3, the secondary reactor 2 includes a second condenser 2a and a second heat exchanger 2b, and the second condenser 2a is used to convert the The top gas flow of the secondary reaction kettle 2 is condensed, and the second heat exchanger 2b acts on the secondary reaction kettle 2 . The light components of the secondary reactor 2 are processed by the second condenser 2a to form liquid and non-condensable gas for reflux, thereby realizing the recovery and reuse of the light components.

In a preferred embodiment as shown in Figures 1 to 3, the light removal tower 4 includes a third condenser 4a, a third heat exchanger 4b and a phase separator 4c; the third condenser 4a is The overhead fraction of the light removal tower 4 is condensed; the third heat exchanger 4b acts on the light removal tower 4; the phase separator 4c is located downstream of the third condenser 4a and connected with the third condenser 4a. The three condensers 4a are connected through pipelines. The light components of the light removal tower 4 are processed through the third condenser 4a, and the condensed liquid phase obtained enters the phase separator 4c for stratification, and the non-condensable gas obtained can be recycled and reused.

In a preferred embodiment as shown in Figures 1 to 3, a first liquid outlet is provided in the middle of the first-level reaction kettle 1, and the first liquid outlet is connected to the second-level reaction kettle 2 The feed inlet is connected through a pipeline. The first liquid outlet located in the middle can effectively ensure the residence time of the reaction raw materials in the first-level reactor 1, thereby ensuring the speed and completion of the reaction during continuous production.

In a preferred embodiment as shown in Figures 1 to 3, a second liquid outlet is provided in the middle of the secondary reactor 2, and the second liquid outlet and the flash tank 3 pass through Pipeline connection. The second liquid outlet located in the middle can effectively ensure the residence time of the reaction raw materials in the secondary reactor 2, thereby ensuring the speed and completion of the reaction during continuous production.

In a preferred embodiment as shown in FIGS. 1 to 3 , the first condenser 1 a is provided with a first outlet and a first liquid return pipe connected to the first-stage reactor 1 . The condensate thus formed by the first condenser 1a is returned to the first-stage reaction kettle 1 through the first liquid return pipe.

In a preferred embodiment as shown in FIGS. 1 to 3 , the second condenser 2 a is provided with a second outlet and a second liquid return pipe connected with the secondary reactor 2 . As a result, the condensate formed by the second condenser 2a is returned to the secondary reaction kettle 2 through the second liquid return pipe.

In a preferred embodiment as shown in Figures 1 to 3, the third condenser 4a is provided with a third non-condensable gas discharge port.

In a preferred embodiment as shown in Figures 1 to 3, the phase separator 4c is provided with an upper liquid reflux pipe and/or a lower liquid reflux pipe connected to the light removal tower 4. The phases are separated by the phase separator 4c to form an upper liquid located in the upper layer and a lower liquid located in the lower layer. According to specific production needs, part of the upper layer liquid can enter the light removal tower 4 through the upper liquid reflux pipe, and part of the lower layer can also enter the light removal tower 4 through the lower liquid reflux pipe.

In a preferred embodiment as shown in Figures 1 to 3, it also includes a first gas-liquid separation tank 1c. The first gas-liquid separation tank 1c is located between the first outlet of the first condenser 1a. Fluid communication, the first gas-liquid separation tank 1c is provided with a first liquid drain port and a first exhaust port, and the first liquid drain port is connected to the first liquid return pipe. The first gas-liquid separation tank 1c shown is used to prevent the non-condensable gas formed by the first condenser 1a from being mixed with part of the condensate.

In a preferred embodiment as shown in Figures 1 to 3, a second gas-liquid separation tank 2c is also included, which is in fluid communication with the second outlet of the second condenser 2a. The second gas-liquid separation tank 2c 2c is provided with a second liquid drain port and a second exhaust port, and the second liquid drain port is connected to the second liquid return pipe. The second gas-liquid separation tank 2c shown is used to prevent the non-condensable gas formed through the second condenser 2a from being mixed with part of the condensate.

In a preferred embodiment as shown in Figure 1, it also includes a dehydration tower 5 located downstream of the light removal tower 4 and in material communication with the light removal tower 4.

In a preferred embodiment as shown in Figures 1 to 3, it also includes several fresh CO feed channels, and the fresh CO feed channels are connected with the first-level reactor 1 and the second-level reactor 2. Or the bottom of flash tank 3 is connected. The CO introduced through the fresh CO feed channel ensures the stable state of the catalyst during the continuous production process. The stable state of the catalyst means that the catalyst does not precipitate, and maintaining the stability of the catalyst is achieved through certain flash evaporation conditions; the certain flash evaporation conditions refer to when the flash evaporation temperature is less than 160°C, or when the flash evaporation temperature is not less than 160°C , introduce CO-containing gas into the flash evaporation system. Add fresh CO to the flash evaporation system, such as the bottom of the flash tank, to increase the stability of the catalyst so that it does not precipitate at higher temperatures of 160 to 180°C, thus increasing the temperature from the traditional about 140°C to 160 to 160°C in the flash evaporation step. At 180°C, the flash evaporation efficiency is increased to achieve the purpose of increasing production and removing the reaction heat at the same time.

In an embodiment as shown in Figure 1, the dehydration tower 5 is provided with a fourth condenser 5a and a fourth heat exchanger 5b; the fourth condenser 5a is used to condense the top of the still water of the dehydration tower 5. The air flow is condensed, and the fourth heat exchanger 5b acts on the dehydration tower 5. In this application, the heat exchanger is used to promote mass and heat transfer.

In an embodiment as shown in Figure 1, a degravity tower 6 is also provided downstream of the dehydration tower 5, and the degravity tower 6 is in material communication with the dehydration tower 5.

In a preferred embodiment as shown in Figure 1, the fourth condenser 5a is provided with a fourth non-condensable gas discharge port and a third liquid return pipe connected with the dehydration tower 5. The liquid phase formed through the fourth condenser 5a is refluxed to the dehydration tower 5 through the third liquid reflux pipe.

In a preferred embodiment as shown in Figure 1, the degravity tower 6 is provided with a fifth condenser 6a and a fifth heat exchanger 6b. The fifth condenser 6a is used to condense the degravity tower. The top gas flow of the boiler 6 is condensed; the fifth heat exchanger 6b acts on the degravity tower 6.

In a specific embodiment as shown in FIG. 1 , the fifth condenser 6 a is provided with a fifth non-condensable gas discharge port and a fourth liquid reflux pipe connected with the degravity tower 6 . The liquid phase formed through the fifth condenser 6a can be returned to the degravity tower 6 through the fourth liquid reflux pipe as needed.

In a specific embodiment as shown in Figure 1, a heavy component reflux pipeline is also included, one end of the heavy component reflux pipeline is connected to a flash tank 3, a light removal tower 4 and the phase separator 4c, One or more of the fourth condenser 5a and the fifth condenser 6a are connected to each other, and the other end is connected to the first-stage reactor 1. As a result, heavy components from each process can be returned through the heavy component return pipeline for reuse.

In a specific preferred embodiment as shown in Figure 1, the system further includes a non-condensable gas pipeline selected from the first exhaust port of the first condenser 1a, the first exhaust port of the second condenser 2a The second exhaust port, the third non-condensable gas discharge port of the third condenser 4a, the fourth non-condensable gas discharge port of the fourth condenser 5a, and the fifth non-condensable gas discharge port of the fifth condenser 6a One or more of the mouths are connected to one end of the non-condensable gas pipeline, and the other end of the non-condensable gas pipeline is connected to the secondary reaction kettle 2 and/or the flash tank 3 . As a result, non-condensable gas can be recycled and reused through non-condensable gas pipelines, thereby reducing costs and saving energy.

As in the specific embodiment shown in Figure 1, Figure 2 or Figure 3, the reaction process is divided into two stages of reaction, which may specifically include the following processes and parameters:

1) Carry out a first-level reaction of methanol, CO, methyl acetate and the activated catalyst mother liquor to obtain the first-level reaction gas phase components and the first-level reaction liquid phase components. Among them, the parameters of the first-level reaction adopt one of the following methods. One or more implementations:

The temperature of the first-stage reaction is 180~200℃, and the pressure is 2.5~3MPa;

The feed molar ratio of methanol to CO is 1:1 to 1:1.5, and the mass of methanol accounts for 10 to 20% of the total mass of the reaction liquid phase;

The first-level reaction is carried out in reaction kettle 1. The liquid phase components in the kettle are 500 to 2000 ppm rhodium catalyst, 2 to 5% moisture, 0.1 to 4% methyl iodide, 5 to 20% lithium iodide, and 1 to methyl acetate. 5%, acetic acid 30~80%;

The first heat exchanger 1b of the first-stage reactor 1 plays the role of heat exchange and enhanced mixing, making the gas-liquid reaction proceed more thoroughly and reducing the production of by-products;

The first condenser 1a at the top of the first-level reaction kettle 1 condenses part of the gas phase components and refluxes them into the first-level reaction kettle 1, while the non-condensable gas components are sent to the non-condensable gas main pipe.

The residence time of materials in the first-level reactor is 10 to 20 minutes.

2) Continuously send the liquid phase in the first-level reaction kettle 1 to the second-level reaction kettle 2 to perform the second-level reaction to obtain the second-level reaction gas phase components and the second-level reaction liquid phase components, wherein the parameters of the second-level reaction are Implemented in one or more of the following ways:

The temperature of the secondary reaction is 160~180℃ and the pressure is 2.5~3MPa;

The secondary reaction is carried out in the secondary reactor 2, the gas phase feed comes from the non-condensable gas main pipe, and the CO in it is deeply utilized;

Fresh CO is replenished in a timely manner to ensure that the partial pressure of CO is not less than 1.5MPa;

The second heat exchanger 2b external to the secondary reactor 2 has the effect of heat exchange and enhanced mixing, making the gas-liquid reaction proceed more thoroughly and reducing the production of by-products;

The external second condenser 2a on the top of the secondary reaction kettle 2 condenses part of the gas phase components and refluxes them into the secondary reaction kettle, while the non-condensable gas components are sent to the non-condensable gas main pipe.

The residence time of materials in the secondary reactor is 10 to 20 minutes.

3) Continuously send the liquid phase in the secondary reactor 2 to the flash tank 3 for flash evaporation, where the parameters of the flash evaporation are as follows

One or more implementations of:

The flash evaporation temperature is 100~180℃ and the pressure is 0.05~0.35MPa;

The gas phase components produced by flash evaporation, including acetic acid, water, methyl iodide, methyl acetate, etc., are sent to the light removal tower for acetic acid purification;

The remaining liquid phase after flash evaporation, because part of the heat is taken away by the latent heat of phase change, its temperature drops to 80-160°C, and is sent to the first-level reactor 1 to participate in the first-level reaction as circulating mother liquor. Before entering the primary reactor 1, it can exchange heat with the first heat exchanger 1b to balance the heat generated by the primary reaction;

Flash evaporation is carried out in the flash evaporation tank 3. At the bottom of the flash evaporation tank 3, the CO-containing gas from the non-condensable gas pipeline is continuously and evenly introduced through the aeration head and other devices, and fresh CO is replenished in a timely manner to ensure that the rhodium system is maintained at high temperature. The catalyst will not precipitate out.

4) Lightening removal, in which lightening removal is implemented in one or more of the following ways:

The light removal is carried out in the light removal tower 4;

The gas phase components from the flash tank 3 (including acetic acid, water, methyl iodide, methyl acetate, acetaldehyde, etc.) are sent to the middle and lower part of the light removal tower 4;

The form of the light removal tower 4 can be a plate tower or a packed tower. If it is a plate column, the number of theoretical plates is 5 to 45, and the reflux ratio is 0.5 to 5. The temperature at the top of the tower is 90~130℃, and the pressure is 80~160kPa (gauge pressure); the temperature of the tower kettle is 130~160℃, and the pressure is 85~180kPa (gauge pressure);

The low boiling point fraction (containing methyl iodide, methyl acetate, acetaldehyde, etc.) is separated from the top of the light removal tower 4, sent to the third condenser 4a at the top of the tower, and then sent to the phase separator 4c. The non-condensable gas is collected into the non-condensable gas main pipe and sent to the bottom of the secondary reactor 2 and flash tank 3;

The liquid phase collected in the phase separator 4c is divided into layers, including an upper liquid containing water, methyl acetate, acetic acid, and acetaldehyde, and a lower liquid containing methyl iodide, acetic acid, acetaldehyde, and their derivatives. These liquid phases are partially refluxed to the top of the light removal tower 4, partially discharged to the subsequent acetaldehyde removal process (not shown), and the remaining portion is recycled back to the primary reaction kettle 1;

The crude acetic acid stream (containing acetic acid, water, methyl iodide, etc.) mainly containing acetic acid is extracted from the side line and sent to the dehydration process;

The high-boiling fraction (containing water, acetic acid, propionic acid, entrained catalyst such as lithium iodide, etc.) is discharged from the bottom of the light removal tower 4 and recycled to the first-stage reactor 1.

The third heat exchanger 4b external to the light removal tower 4 has the effect of heat exchange and enhanced mixing.

5) Dehydration, wherein dehydration is implemented in one or more of the following ways:

Dehydration is carried out in dehydration tower 5;

The acetic acid stream from the light removal tower 4 is sent to the middle of the dehydration tower 5 to further separate low-boiling components such as water in the acetic acid stream;

The dehydration tower 5 can be in the form of a plate tower or a packed tower. If it is a plate column, the number of theoretical plates is 5 to 45, and the reflux ratio is 0.5 to 5. The temperature at the top of the tower is 130~150℃, and the pressure is 150~250kPa (gauge pressure); the temperature of the tower kettle is 150~180℃, and the pressure is 200~300kPa (gauge pressure);

The low boiling point fraction (containing water, methyl iodide, methyl acetate, acetaldehyde, etc.) is separated from the top of the tower and sent to the fourth condenser 5a at the top of the tower. The non-condensable gas is collected into the non-condensable gas main pipe and sent to the bottom of the secondary reactor 2 and the flash tank 3. The condensate part is refluxed to the dehydration tower 5, and the remaining part is recycled to the primary reactor 1;

The main component of the liquid at the bottom of the dehydration tower 5 is acetic acid with a relatively high concentration, and also contains propionic acid and entrained catalyst. This liquid is continuously sent to the degravity process.

The fourth heat exchanger 5b external to the dehydration tower 5 has the effect of heat exchange and enhanced mixing.

6) Deduplication, in which deduplication is implemented in one or more of the following ways:

The acetic acid stream from the bottom of the degravity tower 6 is further purified and separated in the degravity tower 6;

The degravity tower 6 can be in the form of a plate tower or a packed tower;

If it is a plate column, the number of theoretical plates is 5 to 45, and the reflux ratio is 0.5 to 5. The temperature at the top of the tower is 60~160℃, and the pressure is -100~150kPa (gauge pressure); the temperature of the tower kettle is 80~180℃, and the pressure is -90~190kPa (gauge pressure);

The low boiling point fraction (containing water, methyl iodide, methyl acetate, acetaldehyde, etc.) is separated from the top of the tower and sent to the top condenser 6;

The non-condensable gas is collected into the non-condensable gas main pipe and sent to the bottom of the secondary reactor 2 and the flash tank 3. The condensate part is refluxed to the degravity tower 6, and the remaining part is recycled to the primary reactor 1;

The acetic acid product is extracted from the middle of the tower and sent to the subsequent ion resin purification link (not shown);

The acetic acid stream containing heavy components such as propionic acid at the bottom of the tower is sent to other heavy component processing links (not shown) and then recycled to the system (not shown).

The fifth heat exchanger 5b external to the dehydration tower 6 has the effect of heat exchange and enhanced mixing.

7) About non-condensable gas main pipe

According to the pressure adjustment of the entire reaction system, part of the non-condensable gas is sent to the tail gas treatment link (not shown), and the remaining non-condensable gas is sent to the bottom of the secondary reactor 2 and the flash tank 3, and the CO and H ₂ in it are Recycle and reuse.

Example 1

Use the experimental setup shown in Figure 2.

Rhodium iodide (calculated as rhodium element content, 800ppm), methyl iodide (2wt%), lithium iodide (10wt%), methyl acetate (4wt%), water (4wt%), acetic acid (65wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation (that is, after mixing evenly), the catalyst mother liquor is sent to the first-level reactor 1. Based on the total mass of the reaction liquid in the first-level reaction, methanol was fed into the first-level reactor, and the mass percentage of the feed amount was 15 wt%. Pass CO into the primary reaction kettle 1 to perform the primary reaction, that is, the carbonylation reaction. The molar ratio of methanol and CO feed is controlled to 1:1, the temperature of the first-stage reaction is 190°C, and the pressure of the first-stage reaction is 2.8Mpa. After the primary reaction gas phase components pass through the first external condenser 1a on the top of the kettle, the non-condensable gas flows into the non-condensable gas main pipe.

The first-level reaction liquid phase components are exported from the 50% liquid level of the first-level reaction kettle 1 and sent to the second-level reaction kettle 2. The temperature of the secondary reaction is 170°C, and the pressure of the secondary reaction is 2.5Mpa. The reaction raw material CO and a trace amount of hydrogen are provided to the reactor through the non-condensable gas main pipe to carry out a deep reaction and consume the CO in the non-condensable gas. And add fresh CO to the kettle in a timely manner. After the secondary reaction gas phase components pass through the second external condenser 2a, the non-condensable gas flows into the non-condensable gas main pipe.

The secondary reaction liquid phase components are exported at the 50% liquid level of the secondary reaction kettle 2 and sent to the flash tank 3. The flash evaporation temperature is controlled to 140°C, and the flash evaporation pressure is 0.05Mpa. There is no condensable gas or fresh CO flowing into the bottom of the flash tank 3. The flash vapor phase components are sent to the light removal tower 4, and the liquid phase components are recycled back to the primary reactor 1. No precipitation occurred in the rhodium-based catalyst.

The gas phase components from the flash tank 3 are fed from the lower part of the light removal tower 4, and the feeding position is the fourth tray from the bottom. The top pressure of the light removal tower 4 is 80kpa (gauge pressure), and the reflux ratio is 2 (the flow ratio of the return liquid to the distillate after distillation). The crude acetic acid is extracted from the middle of the tower, and the acetic acid product yield is 23.6 mol/Lh (the number of moles of acetic acid extracted per liter of reaction solution per hour).

Example 2

Use the experimental setup shown in Figure 2.

Rhodium iodide (calculated as rhodium element content, 800ppm), methyl iodide (10wt%), lithium iodide (10wt%), methyl acetate (4wt%), water (4wt%), acetic acid (57wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation, the catalyst mother liquor is sent to the primary reaction kettle. Based on the total mass of the reaction liquid in the first-level reaction, methanol was fed into the first-level reactor 1, and the mass percentage of the feed amount was 15 wt%. Pass CO into the primary reaction kettle 1 to perform the primary reaction, that is, the carbonylation reaction. Control the molar ratio of methanol to CO feed to 1:1.

The remaining operating conditions are the same as in Example 1. No precipitation occurred in the rhodium-based catalyst. The acetic acid product yield is 23.8 mol/Lh (the number of moles of acetic acid produced per liter of reaction solution per hour).

Example 3

Use the experimental setup shown in Figure 2.

Rhodium iodide (calculated as rhodium element content, 1000ppm), methyl iodide (10wt%), lithium iodide (10wt%), methyl acetate (4wt%), water (4wt%), acetic acid (57wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation, the catalyst mother liquor is sent to the primary reaction kettle. Based on the total mass of the reaction liquid in the first-level reaction, methanol was fed into the first-level reactor 1, and the mass percentage of the feed amount was 15 wt%. Pass CO into the primary reaction kettle 1 to perform the primary reaction, that is, the carbonylation reaction. Control the molar ratio of methanol to CO feed to 1:1.5.

The remaining operating conditions are the same as in Example 1. No precipitation occurred in the rhodium-based catalyst. The acetic acid product yield is 25.5 mol/Lh (the number of moles of acetic acid produced per liter of reaction solution per hour).

Example 4

Use the experimental setup shown in Figure 2.

Rhodium iodide (calculated as rhodium element content, 1000ppm), methyl iodide (15wt%), lithium iodide (15wt%), methyl acetate (4wt%), water (4wt%), acetic acid (47wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation, the catalyst mother liquor is sent to the primary reaction kettle. Based on the total mass of the reaction liquid in the first-level reaction, methanol was fed into the first-level reactor 1, and the mass percentage of the feed amount was 15 wt%. Pass CO into the primary reaction kettle 1 to perform the primary reaction, that is, the carbonylation reaction. Control the molar ratio of methanol to CO feed to 1:1.5.

The flash evaporation temperature is 140℃ and the flash evaporation pressure is 0.25MPa. The remaining operating conditions are the same as in Example 1. No precipitation occurred in the rhodium-based catalyst. The acetic acid product yield is 27.6 mol/Lh (the number of moles of acetic acid produced per liter of reaction solution per hour).

Example 5

Use the experimental setup shown in Figure 2.

Rhodium iodide (calculated as rhodium element content, 1000ppm), methyl iodide (5wt%), lithium iodide (5wt%), methyl acetate (1wt%), water (2wt%), acetic acid (67wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation, the catalyst mother liquor is sent to the primary reaction kettle. Based on the total mass of the reaction liquid in the first-level reaction, methanol was fed into the first-level reactor 1, and the mass percentage of the feed amount was 15 wt%. Pass CO into the primary reaction kettle 1 to perform the primary reaction, that is, the carbonylation reaction. Control the molar ratio of methanol to CO feed to 1:1.5.

The flash evaporation temperature is 130℃ and the flash evaporation pressure is 0.25MPa. The remaining operating conditions are the same as in Example 1. No precipitation occurred in the rhodium-based catalyst. The acetic acid product yield is 23.5 mol/Lh (the number of moles of acetic acid produced per liter of reaction solution per hour).

Example 6

Use the experimental setup shown in Figure 2.

Rhodium iodide (calculated as rhodium element content, 1000ppm), methyl iodide (5wt%), lithium iodide (15wt%), methyl acetate (6wt%), water (6wt%), acetic acid (48wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation, the catalyst mother liquor is sent to the primary reaction kettle. Based on the total mass of the reaction liquid in the first-level reaction, methanol was fed into the first-level reactor 1, and the mass percentage of the feed amount was 20 wt%. Pass CO into the primary reaction kettle 1 to perform the primary reaction, that is, the carbonylation reaction. Control the molar ratio of methanol to CO feed to 1:1.2.

The flash evaporation temperature is 100℃ and the flash evaporation pressure is 0.1MPa. The remaining operating conditions are the same as in Example 1. No precipitation occurred in the rhodium-based catalyst. The acetic acid product yield is 22.1 mol/Lh (the number of moles of acetic acid produced per liter of reaction solution per hour).

Example 7

Use the experimental setup shown in Figure 2.

Rhodium iodide (based on rhodium element content, 1000ppm), methyl iodide (20wt%), lithium iodide (5wt%), methyl acetate (1wt%), water (2wt%), acetic acid (62wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation, the catalyst mother liquor is sent to the primary reaction kettle. Based on the total mass of the reaction liquid in the first-level reaction, methanol was fed into the first-level reactor 1, and the mass percentage of the feed amount was 10 wt%. Pass CO into the primary reaction kettle 1 to perform the primary reaction, that is, the carbonylation reaction. Control the molar ratio of methanol to CO feed to 1:1.2.

The flash evaporation temperature is 120℃ and the flash evaporation pressure is 0.1MPa. The remaining operating conditions are the same as in Example 1. No precipitation occurred in the rhodium-based catalyst. The acetic acid product yield is 22.9 mol/Lh (the number of moles of acetic acid produced per liter of reaction solution per hour).

Example 8

Use the experimental setup shown in Figure 2.

Rhodium iodide (calculated as rhodium element content, 1000ppm), methyl iodide (2wt%), lithium iodide (10wt%), methyl acetate (4wt%), water (4wt%), acetic acid (65wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation, the catalyst mother liquor is sent to the primary reaction kettle. Based on the total mass of the reaction liquid in the first-level reaction, methanol was fed into the first-level reactor, and the mass percentage of the feed amount was 15 wt%. CO is introduced into the primary reactor 1 to perform the primary reaction, that is, the carbonylation reaction. Control the molar ratio of methanol to CO feed to 1:1.

The flash evaporation temperature is 150℃ and the flash evaporation pressure is 0.1MPa. The remaining operating conditions are the same as in Example 1. No precipitation occurred in the rhodium-based catalyst. The acetic acid product yield is 27.9 mol/Lh (the number of moles of acetic acid produced per liter of reaction solution per hour).

Example 9

Use the experimental setup shown in Figure 3.

Rhodium iodide (calculated as rhodium element content, 1000ppm), methyl iodide (2wt%), lithium iodide (10wt%), methyl acetate (4wt%), water (4wt%), acetic acid (65wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation, the catalyst mother liquor is sent to the primary reaction kettle. Based on the total mass of the reaction liquid in the first-level reaction, methanol was fed into the first-level reactor 1, and the mass percentage of the feed amount was 15 wt%. Pass CO into the primary reaction kettle 1 to perform the primary reaction, that is, the carbonylation reaction. Control the molar ratio of methanol to CO feed to 1:1.

The flash evaporation temperature is 160°C, the flash evaporation pressure is 0.1MPa, and part of the non-condensable gas and CO are passed into the lower part of the flash evaporation tank to protect the rhodium catalyst. The remaining operating conditions are the same as in Example 1. No precipitation occurred in the rhodium-based catalyst. The acetic acid product yield is 30.6 mol/Lh (the number of moles of acetic acid produced per liter of reaction solution per hour).

Example 10

Use the experimental setup shown in Figure 3.

Rhodium iodide (calculated as rhodium element content, 1000ppm), methyl iodide (2wt%), lithium iodide (10wt%), methyl acetate (4wt%), water (4wt%), acetic acid (65wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation, the catalyst mother liquor is sent to the primary reaction kettle. Based on the total mass of the reaction liquid in the first-level reaction, methanol was fed into the first-level reactor 1, and the mass percentage of the feed amount was 15 wt%. Pass CO into the primary reaction kettle 1 to perform the primary reaction, that is, the carbonylation reaction. Control the molar ratio of methanol to CO feed to 1:1.

The flash evaporation temperature is 170°C, the flash evaporation pressure is 0.1MPa, and part of the non-condensable gas and CO are passed into the lower part of the flash evaporation tank to protect the rhodium catalyst. The remaining operating conditions are the same as in Example 1. No precipitation occurred in the rhodium-based catalyst. The acetic acid product yield is 32.1 mol/Lh (the number of moles of acetic acid produced per liter of reaction solution per hour).

Example 11

Use the experimental setup shown in Figure 3.

Rhodium iodide (calculated as rhodium element content, 1000ppm), methyl iodide (2wt%), lithium iodide (10wt%), methyl acetate (4wt%), water (4wt%), acetic acid (65wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation, the catalyst mother liquor is sent to the primary reaction kettle. Based on the total mass of the reaction liquid in the first-level reaction, methanol was fed into the first-level reactor 1, and the mass percentage of the feed amount was 15 wt%. Pass CO into the primary reaction kettle 1 to perform the primary reaction, that is, the carbonylation reaction. Control the molar ratio of methanol to CO feed to 1:1.

The flash evaporation temperature is 180°C, the flash evaporation pressure is 0.1MPa, and part of the non-condensable gas and CO are passed into the lower part of the flash evaporation tank to protect the rhodium catalyst. The remaining operating conditions are the same as in Example 1. No precipitation occurred in the rhodium-based catalyst. The acetic acid product yield is 33.4 mol/Lh (the number of moles of acetic acid produced per liter of reaction solution per hour).

Example 12

Use the experimental setup shown in Figure 3.

Rhodium iodide (based on rhodium element content, 1200ppm), methyl iodide (2wt%), lithium iodide (10wt%), methyl acetate (4wt%), water (4wt%), acetic acid (65wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation, the catalyst mother liquor is sent to the primary reaction kettle. Based on the total mass of the reaction liquid in the first-level reaction, methanol was fed into the first-level reactor 1, and the mass percentage of the feed amount was 15 wt%. Pass CO into the primary reaction kettle 1 to perform the primary reaction, that is, the carbonylation reaction. Control the molar ratio of methanol to CO feed to 1:1.

The flash evaporation temperature is 160°C, the flash evaporation pressure is 0.1MPa, and part of the non-condensable gas and CO are passed into the lower part of the flash evaporation tank to protect the rhodium catalyst. The remaining operating conditions are the same as in Example 1. No precipitation occurred in the rhodium-based catalyst. The acetic acid product yield is 33.3 mol/Lh (the number of moles of acetic acid produced per liter of reaction solution per hour).

Example 13

Use the experimental setup shown in Figure 3.

Rhodium iodide (based on rhodium element content, 1500ppm), methyl iodide (2wt%), lithium iodide (10wt%), methyl acetate (4wt%), water (4wt%), acetic acid (65wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation, the catalyst mother liquor is sent to the primary reaction kettle. Based on the total mass of the reaction liquid of the first-level reaction, methanol was fed into the first-level reactor 1, and the mass percentage of the feed amount was 15 wt%. Pass CO into the primary reaction kettle 1 to perform the primary reaction, that is, the carbonylation reaction. Control the molar ratio of methanol to CO feed to 1:1.

The flash evaporation temperature is 160°C, the flash evaporation pressure is 0.1MPa, and part of the non-condensable gas and CO are passed into the lower part of the flash evaporation tank to protect the rhodium catalyst. The remaining operating conditions are the same as in Example 1. No precipitation occurred in the rhodium-based catalyst. The acetic acid product yield is 37.2 mol/Lh (the number of moles of acetic acid produced per liter of reaction solution per hour).

Example 14

Use the experimental setup shown in Figure 3.

Rhodium iodide (based on rhodium element content, 1500ppm), methyl iodide (2wt%), lithium iodide (10wt%), methyl acetate (4wt%), water (4wt%), acetic acid (65wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation, the catalyst mother liquor is sent to the primary reactor 1. Based on the total mass of the reaction liquid in the first-level reaction, methanol was fed into the first-level reactor 1, and the mass percentage of the feed amount was 15 wt%. Pass CO into the primary reaction kettle 1 to perform the primary reaction, that is, the carbonylation reaction. Control the molar ratio of methanol to CO feed to 1:1.

The flash evaporation temperature is 180°C, the flash evaporation pressure is 0.1MPa, and part of the non-condensable gas and CO are passed into the lower part of the flash evaporation tank to protect the rhodium catalyst. The remaining operating conditions are the same as in Example 1. No precipitation occurred in the rhodium-based catalyst. The acetic acid product yield is 40.6 mol/Lh (the number of moles of acetic acid produced per liter of reaction solution per hour).

Comparative example 1

Use the experimental setup shown in Figure 2.

Rhodium iodide (calculated as rhodium element content, 800ppm), methyl iodide (2wt%), lithium iodide (10wt%), methyl acetate (4wt%), water (4wt%), acetic acid (65wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation, the catalyst mother liquor is sent to the primary reactor 1. Based on the total mass of the reaction liquid in the first-level reaction, methanol was fed into the first-level reactor 1, and the mass percentage of the feed amount was 15 wt%. Pass CO into the primary reaction kettle 1 to perform the primary reaction, that is, the carbonylation reaction. Control the molar ratio of methanol to CO feed to 1:1.

The flash evaporation temperature is 160℃ and the flash evaporation pressure is 0.1MPa. The remaining operating conditions are the same as in Example 1. The rhodium catalyst precipitated, resulting in a serious drop in reaction efficiency. The acetic acid product yield was 10.2 mol/Lh (the number of moles of acetic acid produced per liter of reaction solution per hour).

Comparative example 2

Use the experimental setup shown in Figure 2.

Rhodium iodide (based on rhodium element content, 1500ppm), methyl iodide (2wt%), lithium iodide (10wt%), methyl acetate (4wt%), water (4wt%), acetic acid (65wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation, the catalyst mother liquor is sent to the primary reactor 1. Based on the total mass of the reaction liquid in the first-level reaction, methanol was fed into the first-level reactor 1, and the mass percentage of the feed amount was 15 wt%. Pass CO into the primary reaction kettle 1 to perform the primary reaction, that is, the carbonylation reaction. Control the molar ratio of methanol to CO feed to 1:1.

The flash evaporation temperature is 160℃ and the flash evaporation pressure is 0.1MPa. The remaining operating conditions are the same as in Example 1. The rhodium-based catalyst precipitated, resulting in a serious drop in reaction efficiency. The acetic acid product yield was 16.7 mol/Lh (the number of moles of acetic acid produced per liter of reaction solution per hour).

Comparative example 3

Use the experimental setup shown in Figure 2.

Rhodium iodide (based on rhodium element content, 1500ppm), methyl iodide (2wt%), lithium iodide (10wt%), methyl acetate (4wt%), water (4wt%), acetic acid (65wt%) in proportion Configuration (based on the total mass of the reaction solution in the first-level reaction). After activation, the catalyst mother liquor is sent to the primary reactor 1. Based on the total mass of the reaction liquid in the first-level reaction, methanol was fed into the first-level reactor 1, and the mass percentage of the feed amount was 15 wt%. Pass CO into the primary reaction kettle 1 to perform the primary reaction, that is, the carbonylation reaction. Control the molar ratio of methanol to CO feed to 1:1.

The flash evaporation temperature is 180℃ and the flash evaporation pressure is 0.1MPa. The remaining operating conditions are the same as in Example 1. The rhodium-based catalyst precipitated, resulting in a serious decrease in reaction efficiency. The acetic acid product yield was 17.3 mol/Lh (the number of moles of acetic acid produced per liter of reaction solution per hour). Summary of Examples and Comparative Examples

According to the experimental results in Table 1, the following conclusions can be drawn.

1. Regarding the stability of the catalyst. It depends on the flash evaporation temperature and whether there is CO protection during flash evaporation. When the temperature is lower than 140°C, the catalyst system is stable and there is no need to introduce CO-containing gas at the bottom of the flash tank. When the temperature is higher than 160°C, CO-containing gas needs to be introduced into the flash tank to maintain the stable state of the catalyst. Otherwise, the catalyst will precipitate, resulting in a serious decrease in reaction efficiency.

2. On the premise that the catalyst system is stable, the yield of acetic acid can be controlled mainly through three factors, including rhodium concentration, lithium iodide concentration and flash evaporation temperature. All three have a strong positive correlation with acetic acid yield. The specific logical relationship is shown in Figure 4. According to this logical relationship, the reaction conditions can be flexibly adjusted to achieve the required product yield.

Table 1.

The above embodiments only illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed in the present invention shall still be covered by the claims of the present invention.

Claims (20)

A method for regulating the carbonylation of methanol to produce acetic acid, which is characterized in that the methanol carbonylation method is used to produce acetic acid, while maintaining the stable state of the catalyst, by regulating one selected from the group consisting of rhodium concentration, lithium iodide concentration and flash evaporation temperature. or more to control acetic acid yield. The method according to claim 1, characterized in that, the method is a continuous production method; and/or, under the steady state of the catalyst, the rhodium concentration, lithium iodide concentration and flash temperature are all proportional to the acetic acid yield; And/or, the methanol carbonylation method uses CO and methanol as raw materials, the product acetic acid as a solvent, a rhodium-based catalyst as the main catalyst, methyl acetate, methyl iodide, lithium iodide, acetic acid and water as auxiliaries, and the composition is uniform Phase catalytic reaction system; And/or, the process of producing acetic acid by methanol carbonylation includes reaction, flash evaporation and light removal. The method according to claim 1 or 2, characterized in that the stable state of the catalyst means that the catalyst does not precipitate, and maintaining the stability of the catalyst is achieved through certain flash evaporation conditions; the certain flash evaporation conditions means that the catalyst does not precipitate. When the evaporation temperature is less than 160°C, or the flash evaporation temperature is not less than 160°C, gas containing CO is introduced into the flash evaporation system. The method according to claim 2, characterized in that the feed molar ratio of methanol and CO is 1: (1~1.5); And/or, the amount of methanol used is 10 to 20 wt% of the total mass of the homogeneous catalytic reaction system; And/or, the rhodium-based catalyst is rhodium iodide; And/or, based on the total mass of the homogeneous catalytic reaction system, the amount of the rhodium-based catalyst is 500 to 3000 ppm; And/or, the amount of water used is 2 to 5 wt% of the total mass of the homogeneous catalytic reaction system; And/or, the amount of methyl iodide used is 0.1 to 4 wt% of the total mass of the homogeneous catalytic reaction system; And/or, the amount of lithium iodide used is 5 to 20 wt% of the total mass of the homogeneous catalytic reaction system; And/or, the dosage of methyl acetate is 1 to 5 wt% of the total mass of the homogeneous catalytic reaction system; And/or, the amount of acetic acid used is 30 to 80 wt% of the total mass of the homogeneous catalytic reaction system; And/or, the flash evaporation temperature is 100-180°C; And/or, the flash pressure is 0.05-0.35Mpa. The method according to claim 2, characterized in that the reaction includes a primary reaction and a secondary reaction, and the homogeneous catalytic reaction system is subjected to a primary reaction to obtain the primary reaction gas phase components and the primary reaction liquid. Phase components; use the overflow liquid phase of the primary reaction as the liquid phase of the secondary reaction; and/or, the gas phase components of the secondary reaction include non-condensable gas discharged from other steps. The method according to claim 5, characterized in that it includes one or more of the following features: The temperature of the first-stage reaction is 180-200°C, and the pressure is 2.5-3MPa; The temperature of the secondary reaction is 160-180°C, and the pressure is 2.5-3MPa; The CO partial pressure in the secondary reaction is not less than 1.5MPa; The liquid phase produced by the secondary reaction is flash evaporated. The method according to claim 2, characterized in that it includes one or more of the following features: The gas phase components produced by the flash evaporation are delighted; The liquid phase produced by the flash evaporation enters the reaction system for circulation reaction; The CO in the flash evaporated system includes CO-containing non-condensable gas discharged from other steps; The flash evaporation is carried out in a flash tank; The light removal is carried out in a light removal tower, which is a plate tower or a packed tower; The low boiling point fraction separated by light removal is separated into phases after condensation, and the liquid phase obtained by phase separation is recycled. The low boiling point fraction includes one or more selected from the group consisting of methyl iodide, methyl acetate and acetaldehyde; The high boiling point fraction separated by light removal is recycled in the reaction step, and the high boiling point fraction includes water, acetic acid, propionic acid and lithium iodide. The method according to claim 7, characterized in that the process parameters of the plate tower in the light removal process are selected from one or more of the following: the number of theoretical plates is 5 to 45; the reflux ratio is 0.5 ~5; the tower top temperature is 90~130℃, and the gauge pressure is 80~160kPa; the tower kettle temperature is 130~160℃, and the gauge pressure is 85~180kPa. The method according to claim 2, characterized in that, after dehydration, it also includes dehydration, and the acetic acid obtained by dehydration flows through dehydration to remove water; preferably, the dehydration is performed in a dehydration tower, and the dehydration tower It is a plate tower or packed tower; The dehydration also includes weight removal. Preferably, the weight removal is performed in a weight removal tower, and the weight removal tower is a plate tower or a packed tower. The method according to claim 9, characterized in that the process parameters of the plate tower in the dehydration process are selected from one or more of the following: the number of theoretical plates is 5 to 45; the reflux ratio is 0.5 to 5 ;The tower top temperature is 130~150℃, and the gauge pressure is 150~250kPa; the tower kettle temperature is 150~180℃, and the gauge pressure is 200~300kPa; And/or, the process parameters of the plate tower in the deduplication process are selected from one or more of the following: the number of theoretical plates is 5 to 45, the reflux ratio is 0.5 to 5; the tower top temperature is 60 to 160 ℃, the gauge pressure is -100~150kPa; the tower kettle temperature is 80~180℃, the gauge pressure is -90~190kPa; acetic acid is extracted from the middle part of the degravity tower in the degravity process. A system for regulating the carbonylation of methanol to produce acetic acid, characterized in that the system at least includes a primary reaction kettle (1) and a secondary reaction kettle (2), a flash tank (3) and a decontamination tank that are connected in sequence through pipeline materials. Light Tower(4). The system according to claim 11, characterized in that the first-stage reactor (1) includes a first condenser (1a) and a first heat exchanger (1b); the first condenser (1a) is Condensing the top airflow of the first-level reaction kettle (1); the first heat exchanger (1b) acts on the first-level reaction kettle (1); And/or, the secondary reaction kettle (2) includes a second condenser (2a) and a second heat exchanger (2b), and the second condenser (2a) is used to condense the secondary reaction kettle (2). 2) The top air flow of the kettle is condensed, and the second heat exchanger (2b) acts on the secondary reaction kettle (2); And/or, the light removal tower (4) includes a third condenser (4a), a third heat exchanger (4b) and a phase separator (4c); the third condenser (4a) is used for light removal. The overhead fraction of the light tower (4) is condensed; the third heat exchanger (4b) acts on the light removal tower (4); the phase separator (4c) is located in the third condenser (4a) downstream and connected to the third condenser (4a) through pipeline flow; And/or, a first liquid outlet is provided in the middle of the first-level reaction kettle (1), and the first liquid outlet is connected with the feed port of the second-level reaction kettle (2) through a pipeline; And/or, a second liquid outlet is provided in the middle of the secondary reaction kettle (2), and the second liquid outlet is connected to the flash tank (3) through a pipeline. The system according to claim 12, characterized in that the first condenser (1a) is provided with a first outlet and a first liquid return pipe connected with the first-stage reactor (1); And/or, the second condenser (2a) is provided with a second outlet and a second liquid return pipe connected with the secondary reaction kettle (2); And/or, the third condenser (4a) is provided with a third non-condensable gas discharge port; And/or, the phase separator (4c) is provided with an upper liquid reflux pipe and/or a lower liquid reflux pipe connected with the light removal tower (4). The system according to claim 13, further comprising a first gas-liquid separation tank (1c), the first gas-liquid separation tank (1c) and the first outlet of the first condenser (1a) Fluid communication, the first gas-liquid separation tank (1c) is provided with a first liquid drain port and a first exhaust port, and the first liquid drain port is connected to the first liquid return pipe; And/or, it also includes a second gas-liquid separation tank (2c), which is in fluid communication with the second outlet of the second condenser (2a), and the second gas-liquid separation tank (2c) is in fluid communication with the second outlet of the second condenser (2a). The separation tank (2c) is provided with a second liquid discharge port and a second exhaust port, and the second liquid discharge port is connected with the second liquid return pipe. The system according to claim 11, further comprising a dehydration tower (5) located downstream of the light removal tower (4) and in material communication with the light removal tower (4); And/or, it also includes several fresh CO feed channels, the fresh CO feed channels are connected with the bottom of the first-level reaction kettle (1), the second-level reaction kettle (2) or the flash tank (3). Connected. The system according to claim 15, characterized in that the dehydration tower (5) is provided with a fourth condenser (5a) and a fourth heat exchanger (5b); the fourth condenser (5a) is used for To condense the top gas flow of the dehydration tower (5), the fourth heat exchanger (5b) acts on the dehydration tower (5); And/or, a degravity tower (6) is further provided downstream of the dehydration tower (5), and the degravity tower (6) is in material communication with the dehydration tower (5). The system according to claim 16, characterized in that the fourth condenser (5a) is provided with a fourth non-condensable gas discharge port and a third liquid return pipe connected with the dehydration tower (5); And/or, the degravity tower (6) is provided with a fifth condenser (6a) and a fifth heat exchanger (6b), and the fifth condenser (6a) is used to condense the degravity tower (6). ), the top gas flow of the kettle is condensed; the fifth heat exchanger (6b) acts on the degravity tower (6). The system according to claim 17, characterized in that the fifth condenser (6a) is provided with a fifth non-condensable gas discharge port and a fourth liquid return pipe connected with the degravity tower (6). The system according to claim 12 or 17, further comprising a heavy component reflux pipeline, one end of the heavy component reflux pipeline is connected to a flash tank (3), a light removal tower (4) and the One or more of the phase separator (4c), the fourth condenser (5a), and the fifth condenser (6a) are connected, and the other end is connected with the first-stage reaction kettle (1). The system according to claim 13, 17 or 18, characterized in that the system further includes a non-condensable gas pipeline selected from the first exhaust port, the second exhaust port, the third condenser ( One or more of the third non-condensable gas outlet of 4a), the fourth non-condensable gas outlet of the fourth condenser (5a), and the fifth non-condensable gas outlet of the fifth condenser (6a) It is connected to one end of the non-condensable gas pipeline, and the other end of the non-condensable gas pipeline is connected to the secondary reaction kettle (2) and/or the flash tank (3).

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