Process for reducing catalyst precipitation of acetic acid device
By increasing the partial pressure of carbon monoxide in the pipeline of the acetic acid unit, the catalyst precipitation problem was reduced, thus solving the problem of increased production costs caused by catalyst precipitation and achieving reduced catalyst loss and improved production efficiency.
Patent Information
- Application Number
- CN202510755113.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-06
- Publication Date
- 2025-10-21
AI Technical Summary
In industrial acetic acid production, catalyst precipitation in pipelines leads to losses and reduced production efficiency. Existing technologies cannot effectively solve this problem by periodically replenishing expensive catalysts, thus increasing production costs.
By increasing the partial pressure of carbon monoxide in the pipeline of the acetic acid unit, the precipitation rate of the catalyst is reduced. Carbon monoxide is introduced into the pipeline at different locations to reduce the risk of catalyst precipitation in the pipeline.
It effectively reduces catalyst precipitation, lowers production costs, reduces catalyst loss, improves production efficiency, and saves 2.4 million yuan per year in capital costs.
Smart Images
Figure CN120817852A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of acetic acid production, and in particular to a process for reducing catalyst precipitation in an acetic acid plant. Background Art
[0002] Acetic acid is an important organic chemical raw material widely used in the pharmaceutical, pesticide, dye, textile, and food industries. Currently, the primary method for industrial acetic acid production is the methanol carbonylation process, which uses methanol and carbon monoxide as raw materials over a catalyst to synthesize acetic acid. This process typically uses rhodium- or iridium-based catalysts, which are expensive and contribute significantly to the production cost of acetic acid.
[0003] The carbonylation reaction is an exothermic reaction, and the reaction heat needs to be removed by cooling the reaction through external circulation and flash evaporation. When removing heat through external circulation and flash evaporation, due to the high temperature and long path, the catalyst is prone to precipitation in the pipeline and adheres to the inner wall of the pipeline and equipment. This not only causes the loss of expensive catalyst, but also reduces the reaction rate and affects production efficiency. At present, the industry usually adopts the method of regularly replenishing rhodium or iridium catalysts to solve this problem, but these catalysts are expensive, and regular replenishment will greatly increase production costs. In addition, the recovery rate of the catalyst cannot reach 100%, and the long-term cumulative loss is significant.
[0004] Therefore, there is an urgent need for a process that can effectively reduce catalyst precipitation in acetic acid plants to reduce catalyst loss, lower production costs, and improve the economic benefits of acetic acid production. Summary of the Invention
[0005] The present invention aims to provide a process for reducing catalyst precipitation in an acetic acid plant by increasing the carbon monoxide partial pressure in the pipeline to reduce the precipitation rate of the catalyst, thereby reducing the production cost of acetic acid.
[0006] In order to achieve the above object, the technical solution of the present invention is as follows:
[0007] The present invention provides a process for reducing catalyst precipitation in an acetic acid device. The acetic acid device comprises a reactor, a flash unit, a distillation unit, and a heat recovery unit. Carbon monoxide and methanol are used as raw materials and are contacted with a catalyst in the reactor to react. The reaction temperature and pressure are controlled. A portion of the reaction liquid in the reactor is removed of reaction heat by the heat recovery unit. The reaction liquid after heat exchange is returned to the reactor to continue the circulating reaction. Another portion of the reaction liquid enters the flash unit for flash separation. Crude acetic acid enters the distillation unit for purification, and mother liquor containing the catalyst is returned to the reactor. The device further comprises a carbon monoxide pipeline I and a carbon monoxide pipeline II. The carbon monoxide pipeline I is connected to a reaction liquid circulation pipeline at an outlet of the heat recovery unit; and the carbon monoxide pipeline II is connected to a mother liquor circulation pipeline at a mother liquor outlet of the flash unit.
[0008] In the above technical solution, further, the reaction temperature is 180-195° C., and the reaction pressure is 2.5-3.5 MPa.
[0009] In the above technical solution, further, the temperature of the reaction liquid after heat exchange is 150-160°C.
[0010] In the above technical solution, further, the carbon monoxide flow rate in the carbon monoxide pipeline I is 50-200Nm 3 / h.
[0011] In the above technical solution, further, the pressure of flash separation is 0.1-0.2 MPa.
[0012] In the above technical solution, further, the carbon monoxide flow rate in the carbon monoxide pipeline II is 10-60Nm 3 / h.
[0013] The beneficial effects of the present invention are:
[0014] The present invention introduces a stream of CO into the outer circulation pipeline of the reaction liquid to increase the CO partial pressure in the mother liquor in the pipeline and reduce the risk of catalyst precipitation; and introduces a stream of CO into the outlet of the mother liquor circulation pump to reduce the risk of catalyst precipitation in the pipeline, thereby reducing catalyst loss and lowering production costs.
[0015] The present invention can effectively reduce catalyst precipitation. If the catalyst precipitation is 5 ppm (5 mg) per ton of acetic acid and the annual output is 400,000 tons of acetic acid, about 2,000 g of catalyst will be precipitated each year. If the catalyst costs 1,200 yuan per gram, 2.4 million yuan can be saved annually. While reducing catalyst consumption, the production cost of acetic acid is also reduced. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 This is a process flow chart for reducing catalyst precipitation in an acetic acid plant according to the present invention;
[0017] In the figure: 1. Reactor, 2. Flash evaporator, 3. Distillation tower, 4. Heat recovery device, 5. Condenser, 6. Reflux tank, 7. External circulation pump, 8. Mother liquor circulation pump, 9. Reflux pump, 10. Carbon monoxide pipeline I, 11. Carbon monoxide pipeline II, 12. Reaction liquid circulation pipeline, 13. Mother liquor circulation pipeline. DETAILED DESCRIPTION
[0018] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.
[0019] Unless otherwise specified, the materials used in the examples of the present invention can be obtained from commercial sources or prepared according to conventional methods well known to those skilled in the art.
[0020] Example 1
[0021] A process for reducing catalyst precipitation in an acetic acid plant is used in an acetic acid production plant. Figure 1 As shown, it includes a reactor 1, a flash unit, a distillation unit, and a heat recovery unit; the heat recovery unit includes a heat recovery device 4, an external circulation pump 7, and a reaction liquid circulation pipeline 12; the flash unit includes a flash evaporator 2, and the flash pressure is 0.2 MPa; the distillation unit includes a distillation tower 3, a condenser 5, and a reflux tank 6.
[0022] Carbon monoxide and methanol are used as raw materials and are in contact with the catalyst in the reactor 1 to react at 191°C and 3.0 MPa to produce acetic acid. A portion of the reaction liquid in the reactor 1 is removed from the heat of reaction by the heat recovery device 4 through the external circulation pump 7. After the heat exchange, the temperature of the reaction liquid is reduced to 160°C and is returned to the reactor 1 through the reaction liquid circulation pipeline 12 to continue the circulation reaction. At the same time, 100Nm 3 / h of carbon monoxide to increase the partial pressure in the pipeline; the other part of the reaction liquid enters the flash evaporation unit to separate the catalyst from the crude acetic acid. The pressure of the flash evaporator 2 is 0.2MPa. The mother liquid containing the catalyst after separation is pressurized to 3.0MPa by the mother liquid circulation pump 8 and returned to the reactor 2. At the same time, a 40Nm 3 / h of carbon monoxide returns to reactor 1 from the bottom of reactor 2 together with the mother liquor to continue participating in the reaction; the crude acetic acid separated by flash evaporator 2 enters the distillation unit for purification.
[0023] Example 2
[0024] A process for reducing catalyst precipitation in an acetic acid production plant is disclosed. The process uses carbon monoxide and methanol as raw materials, which react with the catalyst in a reactor 1 at 180°C and 2.5 MPa to produce acetic acid. A portion of the reaction liquid in the reactor 1 is passed through an external circulation pump 7 and a heat recovery device 4 to remove the reaction heat. After heat exchange, the temperature of the reaction liquid is reduced to 150°C and the reaction liquid is returned to the reactor 1 through a reaction liquid circulation line 12 to continue the circulation reaction. At the same time, a 50Nm2 reaction liquid is introduced into the reaction liquid circulation line 12 at the outlet of the heat recovery unit. 3 / h of carbon monoxide to increase the partial pressure in the pipeline; the other part of the reaction liquid enters the flash evaporation unit to separate the catalyst from the crude acetic acid. The pressure of the flash evaporator 2 is 0.1MPa. The mother liquid containing the catalyst after separation is pressurized to 2.5MPa by the mother liquid circulation pump 8 and returned to the reactor 2. At the same time, 10Nm 3 / h of carbon monoxide returns to reactor 1 from the bottom of reactor 2 together with the mother liquor to continue participating in the reaction; the crude acetic acid separated by flash evaporator 2 enters the distillation unit for purification.
[0025] Example 3
[0026] A process for reducing catalyst precipitation in an acetic acid production unit is disclosed. The process uses carbon monoxide and methanol as raw materials, which react with the catalyst in a reactor 1 at 195°C and 3.5 MPa to produce acetic acid. A portion of the reaction liquid in the reactor 1 is passed through an external circulation pump 7 and a heat recovery device 4 to remove the reaction heat. After heat exchange, the temperature of the reaction liquid is reduced to 160°C and the reaction liquid is returned to the reactor 1 through a reaction liquid circulation line 12 to continue the circulation reaction. At the same time, 200 Nm3 of heat is introduced into the reaction liquid circulation line 12 at the outlet of the heat recovery unit. 3 / h of carbon monoxide to increase the partial pressure in the pipeline; the other part of the reaction liquid enters the flash evaporation unit to separate the catalyst from the crude acetic acid. The pressure of the flash evaporator 2 is 0.2MPa. The mother liquid containing the catalyst after separation is pressurized to 3.5MPa by the mother liquid circulation pump 8 and returned to the reactor 2. At the same time, a 60Nm 3 / h of carbon monoxide returns to reactor 1 from the bottom of reactor 2 together with the mother liquor to continue participating in the reaction; the crude acetic acid separated by flash evaporator 2 enters the distillation unit for purification.
[0027] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the scope defined in the claims. Other variations or modifications may be made based on the above description. Obvious variations or modifications derived therefrom shall remain within the scope of protection of the present invention.
Claims
1. A process for reducing catalyst precipitation in an acetic acid plant, comprising a reactor, a flash unit, a distillation unit, and a heat recovery unit. Carbon monoxide and methanol are used as raw materials and react with a catalyst in the reactor. The reaction temperature and pressure are controlled. A portion of the reaction liquid in the reactor is removed from the heat of reaction by the heat recovery unit. The heat-exchanged reaction liquid is returned to the reactor to continue the cyclic reaction. Another portion of the reaction liquid enters the flash unit for flash separation. Crude acetic acid enters the distillation unit for purification, and a mother liquor containing the catalyst is returned to the reactor. The process is characterized by: The device also includes a carbon monoxide pipeline I and a carbon monoxide pipeline II. The carbon monoxide pipeline I is connected to the reaction liquid circulation pipeline at the outlet of the heat recovery unit; the carbon monoxide pipeline II is connected to the mother liquid circulation pipeline at the mother liquid outlet of the flash unit.
2. The process for reducing catalyst precipitation in an acetic acid plant according to claim 1, wherein: The reaction temperature is 180-195°C, and the reaction pressure is 2.5-3.5 MPa.
3. The process for reducing catalyst precipitation in an acetic acid plant according to claim 1, wherein: The temperature of the reaction liquid after heat exchange is lower than 150-160°C.
4. The process for reducing catalyst precipitation in an acetic acid plant according to claim 1, wherein: The carbon monoxide flow rate in the carbon monoxide pipeline I is 50-200Nm 3 / h.
5. The process for reducing catalyst precipitation in an acetic acid plant according to claim 1, wherein: The pressure of flash separation is 0.1-0.2MPa.
6. The process for reducing catalyst precipitation in an acetic acid plant according to claim 1, wherein: The carbon monoxide flow rate in the carbon monoxide pipeline II is 10-60Nm 3 / h.