Water-saving type methanol carbonylation for acetic acid production enhanced reaction system
By employing a series reaction section and enhanced mass transfer device design in the methanol carbonylation process to produce acetic acid, the problems of catalyst precipitation and water-gas reforming were solved, achieving efficient and low-energy acetic acid production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- NANJING YANCHANG REACTION TECH RES INST CO LTD
- Filing Date
- 2025-05-30
- Publication Date
- 2026-07-14
AI Technical Summary
In the existing methanol carbonylation process for producing acetic acid, the catalyst is prone to precipitation, and the water-gas reforming reaction is frequent, resulting in low catalytic efficiency, reduced selectivity and yield, as well as high energy consumption and production costs.
The reactors are designed with a series of pre-reaction and main reaction sections, combined with enhanced mass transfer devices and circulation pipelines to improve the reaction path and mass transfer area, reduce the moisture content of the catalyst, avoid precipitation, and enhance the mixing and distribution of raw materials.
It improves the conversion rate of raw materials and the yield of products, reduces reaction energy consumption and production costs, and simplifies subsequent processing procedures.
Smart Images
Figure CN224485937U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of acetic acid preparation technology, and more specifically, to an enhanced reaction system for the production of acetic acid by methanol carbonylation, which is a water-saving process. Background Technology
[0002] Acetic acid, with the molecular formula CH3COO and a relative molecular mass of 60.05, is a colorless liquid with a pungent, acidic odor and corrosive properties. It contains the carbonyl group, a functional group characteristic of organic acids. Due to its very low freezing point, acetic acid is also known as glacial acetic acid. As a widely used and important chemical raw material, acetic acid is extensively applied in industrial production. It is primarily used to synthesize the monomer VAM for vinyl acetate, as a raw material for the synthesis of acetic anhydride, and as a solvent for the production of refined terephthalic acid. It can also be used to produce acetate esters, chloroacetic acid, and other substances. Hundreds of downstream products can be derived from it. Because acetic acid is widely used in basic organic synthesis, pharmaceuticals, pesticides, printing and dyeing, textiles, and food industries, the development of the acetic acid industry is closely related to all sectors of the national economy.
[0003] The main methods for producing acetic acid include acetaldehyde oxidation, direct olefin oxidation, and methanol carbonylation. Acetaldehyde oxidation achieves a conversion rate of 95% at atmospheric pressure and 60°C, but it is gradually being phased out due to the severe environmental pollution caused by the organomercury catalyst used. Direct olefin oxidation's competitiveness is limited by its low feedstock (butane, naphtha, etc.) conversion rate, complex product separation process, and high cost. The methanol carbonylation method for synthesizing acetic acid has advantages such as high methanol conversion rate and fewer byproducts, and is gradually becoming the mainstream method for acetic acid synthesis.
[0004] The methanol carbonylation process primarily uses methanol and CO as raw materials. Under a rhodium-iodine catalytic system, the methanol and CO are homogeneously mixed in the reactor and react to produce acetic acid. The reaction temperature and pressure are 185–190℃ and 2.9 MPa, respectively. Unreacted CO and organic vapors are discharged from the top of the reactor and then pass through a gas distributor at the bottom of the conversion vessel to react with methanol and methyl acetate in the reaction liquid, ultimately producing acetic acid. Currently, the most commonly used catalyst system is rhodium, with iodomethane as the co-catalyst and lithium iodide as the catalyst additive. However, this catalyst system easily forms trivalent rhodium precipitate, and both rhodium and iodides readily precipitate, significantly affecting catalytic efficiency. To reduce rhodium precipitation, approximately 15% water is added to the catalyst system, which needs to be removed by distillation, increasing reaction energy consumption and production costs. Simultaneously, the reaction produces byproducts such as propionic acid, CO2, and H2, reducing the final selectivity and yield. Furthermore, the process using this catalyst system is prone to water-gas reforming, resulting in low selectivity and further affecting the yield of the reaction products.
[0005] In view of the above, this utility model is hereby proposed. Utility Model Content
[0006] The primary objective of this invention is to provide a water-saving enhanced reaction system for the carbonylation of methanol to acetic acid. This system effectively extends the reaction path and improves the conversion rate of the reactants by dividing the reactor into two reaction sections connected in series. Furthermore, by installing two enhanced mass transfer devices with staggered outlets within the main reaction section, the interphase mass transfer area between the reactants can be increased, thereby further increasing the reactant conversion rate and product yield. In addition, this design ensures the catalytic effect of the rhodium catalyst even when the water content in the catalyst system is low, which helps reduce the probability of water-gas reforming reactions, lowering reaction energy consumption and production costs.
[0007] The second objective of this invention is to provide a water-saving enhanced reaction method for the production of acetic acid by methanol carbonylation. This method, by employing the above-mentioned system, can achieve efficient production of acetic acid under low energy consumption conditions.
[0008] In order to achieve the above-mentioned objectives of this utility model, the following technical solution is adopted:
[0009] This invention provides a water-saving enhanced reaction system for methanol carbonylation to acetic acid, comprising: a reactor, a first catalyst pipeline, a second catalyst pipeline, a first methanol pipeline, a second methanol pipeline, and a carbon monoxide pipeline; the first catalyst pipeline and the second catalyst pipeline are both used to transport a catalyst mixture, the catalyst mixture comprising a rhodium catalyst and lithium propionate;
[0010] The reactor includes a pre-reaction section and a main reaction section, with the pre-reaction section located above the main reaction section. The central axis of the main reaction section coincides with that of the pre-reaction section, and the diameter of the main reaction section is 1.5-2 times the diameter of the pre-reaction section. The upper part of the main reaction section is connected to the pre-reaction section via a venting pipe, and the bottom of the pre-reaction section is connected to the main reaction section via a liquid delivery pipe.
[0011] The outlets of the first catalyst pipeline and the first methanol pipeline are both connected to the pre-reaction section, and the second catalyst pipeline and the second methanol pipeline are both connected to the main reaction section;
[0012] The main reaction section is equipped with a first enhanced mass transfer device and a second enhanced mass transfer device. The first enhanced mass transfer device and the second enhanced mass transfer device are located at the same height and their outlets are staggered. The outlet of the carbon monoxide pipeline is connected to the first enhanced mass transfer device, and the bottom of the main reaction section is connected to the second enhanced mass transfer device via a first forced circulation pipeline.
[0013] In the above scheme, by dividing the reactor into two reaction sections connected in series, the reactants can pass through the pre-reaction section and the main reaction section sequentially, which effectively extends the reaction path and improves the conversion rate of the reactants. By aligning the central axis of the main reaction section with that of the pre-reaction section, and with the diameter of the main reaction section being 1.5-2 times that of the pre-reaction section, the transition of the fluid between the pre-reaction section and the main reaction section is smoother, which helps the reactants to mix more thoroughly in the main reaction section, thereby improving the reaction efficiency. Furthermore, due to the larger diameter of the main reaction section, the change in flow velocity is more gradual when the fluid enters the main reaction section, reducing turbulence and pressure loss caused by abrupt diameter changes, allowing the fluid to enter the main reaction section more smoothly. By setting two enhanced mass transfer devices in the main reaction section, carbon monoxide can be dispersed and broken into micron-sized microbubbles, improving the solubility of carbon monoxide in the reaction liquid and increasing the gas-liquid mass transfer area, thereby improving the utilization and conversion rate of carbon monoxide. Simultaneously, the enhanced mass transfer devices can transfer the circulating fluid from the bottom of the main reaction section... The liquid flow is dispersed into microdroplets, which helps to further increase the mass transfer area at the phase interface. By staggering the two enhanced mass transfer devices, the two staggered liquid flows can be used to stir the liquid flow in the horizontal direction, which helps to ensure uniform distribution of raw materials and can, to some extent, avoid catalyst precipitation and improve catalyst utilization. In addition, since the use of two enhanced mass transfer devices improves the raw material conversion rate and catalyst utilization rate, the water content in the catalyst system can be appropriately reduced, which helps to reduce the energy consumption and cost required for water separation in subsequent processes. By setting up a first forced circulation pipeline, the reaction liquid in the main reaction section can be stirred in the vertical direction, which helps to further promote uniform distribution of raw materials and avoid catalyst precipitation. By setting up a venting pipeline, the unreacted carbon monoxide in the main reaction section can be reacted in the pre-reaction section, improving the carbon monoxide conversion rate. In summary, this scheme can effectively improve the raw material conversion rate and product yield, and helps to reduce reaction energy consumption and reaction cost.
[0014] Preferably, a third enhanced mass transfer device and a fourth enhanced mass transfer device are provided in the pre-reaction section, the third enhanced mass transfer device and the fourth enhanced mass transfer device are located at the same height and the outlets of the third enhanced mass transfer device and the fourth enhanced mass transfer device are staggered; the outlet of the venting pipeline is connected to the third enhanced mass transfer device; the bottom of the pre-reaction section is connected to the fourth enhanced mass transfer device via a second forced circulation pipeline.
[0015] In the above scheme, the third enhanced mass transfer device can disperse and break down the carbon monoxide transported in the ventilation pipeline into micron-sized microbubbles, thereby increasing the gas-liquid mass transfer area and improving the raw material conversion rate; the fourth enhanced mass transfer device can disperse the circulating liquid flow into microdroplets, which helps to further increase the phase boundary mass transfer area; by staggering the two enhanced mass transfer devices, the two staggered liquid flows can be used to stir the liquid flow in the horizontal direction, which helps to ensure uniform distribution of raw materials and can avoid catalyst precipitation to a certain extent, thereby improving the catalyst utilization rate; the second forced circulation pipeline can stir the reaction liquid in the pre-reaction section in the vertical direction, which helps to further promote uniform distribution of raw materials and avoid catalyst precipitation.
[0016] Preferably, both the third and fourth enhanced mass transfer devices are equipped with a first arc-shaped guide tube at their outlets. The gas-liquid mixture output from both devices is guided by this first arc-shaped guide tube and output in either a clockwise or counterclockwise direction. The first arc-shaped guide tube allows the two enhanced mass transfer devices to output the gas-liquid mixture along the same circumferential direction, causing the reaction liquid between the two devices to be agitated clockwise or counterclockwise, improving the agitation effect, further promoting uniform distribution of raw materials, and preventing catalyst precipitation.
[0017] Preferably, the pre-reaction section is provided with multiple layers of sieve plates, which are vertically positioned between the third enhanced mass transfer device and the liquid surface in the pre-reaction section. The outlet of the first catalyst pipeline is vertically not lower than the lowest sieve plate of the multiple layers of sieve plates, and not higher than the liquid surface in the pre-reaction section. By setting the sieve plates, the flow rate of the reaction liquid in the upper part of the pre-reaction section can be reduced, the reaction path of carbon monoxide can be extended, and thus the raw material conversion rate can be improved. At the same time, setting the outlet of the first catalyst pipeline in the sieve plate area can reduce the catalyst precipitation rate and improve the catalyst utilization rate.
[0018] Preferably, the system further includes a first circulating heat exchange pipeline; the inlet of the first circulating heat exchange pipeline is connected to the pre-reaction section and located between the liquid surface of the pre-reaction section and the sieve plate, and the outlet of the first circulating heat exchange pipeline is connected to the fourth enhanced mass transfer device. On one hand, the first circulating heat exchange pipeline can cool the reaction liquid, maintain a stable temperature in the reaction system, and ensure reaction efficiency. On the other hand, the first circulating heat exchange pipeline can circulate the reaction liquid from the top of the pre-reaction section to the fourth enhanced mass transfer device, which can both vertically stir the reaction liquid and further increase the phase boundary mass transfer area of the reactants in the reaction liquid using the fourth enhanced mass transfer device.
[0019] Preferably, both the first and second enhanced mass transfer devices are equipped with second arc-shaped guide tubes at their outlets. The gas-liquid mixtures output from the first and second enhanced mass transfer devices are guided by these second arc-shaped guide tubes and output in either a clockwise or counterclockwise direction. The second arc-shaped guide tubes allow the two enhanced mass transfer devices to output the gas-liquid mixture along the same circumferential direction, causing the reaction liquid between the two enhanced mass transfer devices to be agitated in either a clockwise or counterclockwise direction, improving the agitation effect, further promoting uniform distribution of raw materials, and preventing catalyst precipitation.
[0020] Preferably, the system further includes a second circulating heat exchange pipeline; the inlet of the second circulating heat exchange pipeline is connected to the main reaction section and located between the liquid surface of the main reaction section and the first enhanced mass transfer device, and the outlet of the second circulating heat exchange pipeline is connected to the second enhanced mass transfer device. On the one hand, the second circulating heat exchange pipeline can cool the reaction liquid, maintain the temperature stability of the reaction system, and ensure reaction efficiency. On the other hand, the second circulating heat exchange pipeline can circulate the reaction liquid at the top of the main reaction section to the second enhanced mass transfer device, which can both stir the reaction liquid in the vertical direction and further increase the phase boundary mass transfer area of the reactants in the reaction liquid using the fourth enhanced mass transfer device.
[0021] It will be understood by those skilled in the art that the enhanced mass transfer device used in this utility model has been reflected in the inventor's prior patents, such as patents with application numbers CN201610641119.6, CN201610641251.7, CN201710766435.0, CN106187660A, CN105903425A, CN205833127U and CN207581700U. The prior patent CN201610641119.6 details the specific product structure and working principle of a micron-sized bubble generator (i.e., a bubble breaker). This application document states that "the micron-sized bubble generator includes a main body and a secondary breaking component. The main body has a cavity, and an inlet communicating with the cavity is provided on the main body. The first and second ends of the cavity are both open, and the cross-sectional area of the cavity decreases from the middle of the cavity towards the first and second ends. The secondary breaking component is located at at least one of the first and second ends of the cavity, with a portion of the secondary breaking component located within the cavity. A ring-shaped channel is formed between the secondary breaking component and the open through-holes at both ends of the cavity. The micron-sized bubble generator also includes an air inlet pipe and a liquid inlet pipe." From the specific structure disclosed in this application document, its specific working principle can be understood as follows: liquid enters the micron-sized bubble generator tangentially through the liquid inlet pipe, rotates at ultra-high speed, and cuts the gas, causing the gas bubbles to break into micron-sized microbubbles, thereby increasing the mass transfer area between the liquid and gas phases. Moreover, the micron-sized bubble generator in this patent is a pneumatic bubble breaker.
[0022] Furthermore, prior patent 201610641251.7 describes a primary bubble breaker with a circulating liquid inlet, a circulating gas inlet, and a gas-liquid mixture outlet, while a secondary bubble breaker connects the feed inlet to the gas-liquid mixture outlet. This indicates that both bubble breakers require a gas-liquid mixture to enter. Additionally, as shown in the accompanying drawings, the primary bubble breaker primarily utilizes the circulating liquid as its power source, thus classifying it as a hydraulically driven enhanced reactor. The secondary bubble breaker simultaneously introduces the gas-liquid mixture into an elliptical rotating sphere for rotation, thereby achieving bubble breakage during rotation. Therefore, the secondary bubble breaker is actually a gas-liquid linkage bubble breaker. In fact, both hydraulically driven and gas-liquid linkage bubble breakers are specific forms of bubble breakers. However, the enhanced mass transfer device used in this invention is not limited to these forms; the specific structure of the bubble breaker described in the prior patent is merely one possible form for this invention.
[0023] Furthermore, prior patent 201710766435.0 states that "the principle of the bubble breaker is to achieve mutual collision of gases by high-speed jetting"; and prior patent CN106187660 also describes the specific structure of the bubble breaker, as detailed in paragraphs
[0031] -
[0041] of the specification and the attached drawings. It elaborates on the specific working principle of the bubble breaker S-2. The top of the bubble breaker is the liquid phase inlet, and the side is the gas phase inlet. The liquid phase entering from the top provides the entrainment force, thereby achieving the effect of crushing into ultrafine bubbles. The attached drawings also show that the bubble breaker has a conical structure, with the upper diameter being larger than the lower diameter, which is also to allow the liquid phase to provide better entrainment force.
[0024] Because the bubble breaker was newly developed in the early stages of the prior patent application, it was initially named a micron bubble generator (CN201610641119.6), etc. With continuous technological improvements, it was later renamed a bubble breaker. The enhanced mass transfer device in this utility model is equivalent to the previous micron bubble generator, micro-interface generator, etc., only with different names. In summary, the enhanced mass transfer device of this utility model belongs to the prior art.
[0025] Preferably, it also includes a discharge pipe, the inlet of which is connected to the main reaction section and the inlet of which is located between the first enhanced mass transfer device and the liquid surface of the main reaction section. This facilitates product extraction.
[0026] Preferably, a condenser is connected to the top of the pre-reaction section, and the bottom of the condenser is connected to the pre-reaction section via a return pipe. After the gas at the top of the pre-reaction section is condensed by the condenser, the liquid phase material flows back to the pre-reaction section via the return pipe. By setting up a condenser, some unreacted reactants carried in the top gas phase can be recovered, which helps to improve the utilization rate of reactants.
[0027] This invention also provides a water-saving enhanced reaction method for the carbonylation of methanol to produce acetic acid, which uses the system described in any of the above embodiments to prepare acetic acid.
[0028] Compared with the prior art, the beneficial effects of this utility model are as follows:
[0029] 1. By dividing the reactor into two reaction sections connected in series, the reactants can pass through the pre-reaction section and the main reaction section in sequence, which can effectively extend the reaction path and improve the conversion rate of the reactants.
[0030] 2. By setting two enhanced mass transfer devices in the main reaction section, carbon monoxide can be dispersed and broken into micron-sized microbubbles, which can improve the solubility of carbon monoxide in the reaction liquid and increase the gas-liquid mass transfer area, thereby improving the utilization and conversion rate of carbon monoxide. At the same time, the enhanced mass transfer devices can disperse the liquid flow circulating from the bottom of the main reaction section into microdroplets, which helps to further improve the phase boundary mass transfer area.
[0031] 3. By staggering the two enhanced mass transfer devices, the two staggered liquid flows can be used to stir the liquid flow in the horizontal direction. This helps to ensure uniform distribution of raw materials and can avoid catalyst precipitation to a certain extent, thereby improving the utilization rate of the catalyst. In addition, since the use of two enhanced mass transfer devices improves the conversion rate of raw materials and the utilization rate of catalyst, the water content in the catalyst system can be appropriately reduced. This helps to reduce the energy consumption and cost required for water separation in subsequent processes.
[0032] 4. By setting up the first forced circulation pipeline, the reaction liquid in the main reaction section can be stirred in the vertical direction, which helps to further promote the uniform distribution of raw materials and avoid catalyst precipitation; by setting up the aeration pipeline, the unreacted carbon monoxide in the main reaction section can be reacted in the pre-reaction section, thereby improving the carbon monoxide conversion rate.
[0033] 5. In summary, this scheme can effectively improve the conversion rate of raw materials and the yield of products, and helps to reduce reaction energy consumption and reaction costs. Attached Figure Description
[0034] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:
[0035] Figure 1 A schematic diagram of the system according to Embodiment 1 of this utility model is shown;
[0036] Figure 2 A schematic diagram showing the positional arrangement of the third and fourth enhanced mass transfer devices in Embodiment 1 of this utility model is provided.
[0037] Figure 3 This diagram shows the positional arrangement of the first and second enhanced mass transfer devices in Embodiment 1 of the present invention.
[0038] In the diagram: 1. First catalyst pipeline; 2. First methanol pipeline; 3. Light component pipeline; 4. Sieve plate; 5. Pre-reaction section; 6. Fourth enhanced mass transfer device; 7. Third enhanced mass transfer device; 8. Liquid delivery pipeline; 9. Second catalyst pipeline; 10. Second methanol pipeline; 11. Main reaction section; 12. Carbon monoxide pipeline; 13. Carbon monoxide storage tank; 14. First enhanced mass transfer device; 15. Second enhanced mass transfer device; 16. Drain pipe 17. First forced circulation pipeline; 18. Discharge pipeline; 19. Second circulating heat exchange pipeline; 20. Conveying pipeline; 21. Second forced circulation pipeline; 22. First circulating heat exchange pipeline; 23. Vent pipeline; 24. Condenser; 25. Return pipeline; 26. First heat exchanger; 27. Third heat exchanger; 28. Second heat exchanger; 29. Fourth heat exchanger; 30. First arc-shaped guide pipe; 31. Second arc-shaped guide pipe. Detailed Implementation
[0039] The technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are only some embodiments of this utility model, not all embodiments, and are only used to illustrate this utility model, and should not be regarded as limiting the scope of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.
[0040] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0041] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.
[0042] The inventors discovered through research that the processes for preparing acetic acid in related technologies mainly have the following problems:
[0043] 1. The commonly used catalyst system in related technologies is rhodium, the co-catalyst is iodomethane, and the catalyst additive is lithium iodide. However, this catalyst system is prone to forming trivalent rhodium precipitate. Both rhodium and iodide readily form precipitates, significantly affecting catalytic efficiency. To reduce rhodium precipitation, approximately 15% water is added to the catalyst system. This water needs to be removed by distillation, increasing reaction energy consumption and production costs. Simultaneously, the reaction produces byproducts such as propionic acid, CO2, and H2, reducing the final selectivity and yield.
[0044] 2. Because the catalyst system contains about 15% water, it is prone to undergo water-gas reforming reaction with the reaction raw material CO, resulting in low selectivity and further affecting the yield of the reaction product.
[0045] 3. The catalyst system also contains iodides, which can cause severe equipment corrosion and increase production costs;
[0046] 4. The content of propionic acid, a byproduct, is relatively high, making subsequent removal of the byproduct difficult and the removal process complex.
[0047] 5. This reaction process is exothermic. The higher the reaction rate, the more heat of reaction occurs. The heat of reaction affects the progress of the reaction and leads to an increase in by-products.
[0048] 6. The current system connects two reactors in series, which occupies a large area and greatly increases production energy consumption and difficulty.
[0049] To address at least one of the aforementioned technical problems, this invention provides a water-saving enhanced reaction system and method for the carbonylation of methanol to produce acetic acid. Applying this system to acetic acid preparation can improve raw material conversion rate and product yield, while reducing reaction energy consumption and production costs. The system and method are described in detail below.
[0050] To more clearly illustrate the technical solution of this utility model, the following description is provided in the form of specific embodiments.
[0051] Example 1
[0052] See also Figure 1-3 This embodiment provides a water-saving enhanced reaction system for the carbonylation of methanol to acetic acid. The system includes: a reactor, a first catalyst line 1, a second catalyst line 9, a first methanol line 2, a second methanol line 10, and a carbon monoxide line 12. Both the first catalyst line 1 and the second catalyst line 9 are used to transport a catalyst mixture, which includes a rhodium catalyst and lithium propionate. Lithium propionate serves as a catalyst co-solvent (i.e., promoter). The catalyst mixture also includes water, and the water content in the catalyst mixture is within the range of [0.8%, 1.5%].
[0053] like Figure 1 As shown, the reactor includes a pre-reaction section 5 and a main reaction section 11. The pre-reaction section 5 is located above the main reaction section 11. The central axis of the main reaction section 11 coincides with that of the pre-reaction section 5, and the diameter of the main reaction section 11 is 1.5-2 times the diameter of the pre-reaction section 5. The upper part of the main reaction section 11 is connected to the pre-reaction section 5 via a venting pipe 23. The bottom of the pre-reaction section 5 is connected to the main reaction section 11 via a liquid delivery pipe 8. The liquid levels in the pre-reaction section 5 and the main reaction section 11 occupy 2 / 3-4 / 5 of the corresponding reaction section volumes.
[0054] In this embodiment, the outlets of the first catalyst pipeline 1 and the first methanol pipeline 2 are both connected to the pre-reaction section 5, and the second catalyst pipeline 9 and the second methanol pipeline 10 are both connected to the main reaction section 11. A first enhanced mass transfer device 14 and a second enhanced mass transfer device 15 are installed within the main reaction section 11. The inlet of the carbon monoxide pipeline 12 is connected to the carbon monoxide storage tank 13, and the outlet is connected to the first enhanced mass transfer device 14. The bottom of the main reaction section 11 is connected to the second enhanced mass transfer device 15 via a first forced circulation pipeline 17. A first heat exchanger 26 is installed on the first forced circulation pipeline 17.
[0055] Continue reading Figure 1The pre-reaction section 5 is equipped with a third enhanced mass transfer device 7 and a fourth enhanced mass transfer device 6, which are located at the same height and have staggered outlets. The outlet of the ventilation pipe 23 is connected to the third enhanced mass transfer device 7. The bottom of the pre-reaction section 5 is connected to the fourth enhanced mass transfer device 6 via a second forced circulation pipe 21. In this embodiment, as shown... Figure 2 As shown, the outlets of the third enhanced mass transfer device 7 and the fourth enhanced mass transfer device 6 are both equipped with a first arc-shaped guide tube 30. The gas-liquid mixture output from the third enhanced mass transfer device 7 and the fourth enhanced mass transfer device 6 is output in a clockwise or counterclockwise direction under the guidance of the first arc-shaped guide tube 30 (clockwise in the figure).
[0056] A condenser 24 is connected to the top of the pre-reaction section 5. The bottom of the condenser 24 is connected to the pre-reaction section 5 via a return pipe 25. The gas at the top of the pre-reaction section 5 is condensed by the condenser 24, and the liquid phase material flows back to the pre-reaction section 5 via the return pipe 25. A multi-layer sieve plate 4 is installed in the pre-reaction section 5. The multi-layer sieve plate 4 is located vertically between the third enhanced mass transfer device 7 and the liquid surface in the pre-reaction section 5. The outlet of the first catalyst pipeline 1 is vertically not lower than the lowest sieve plate 4 of the multi-layer sieve plate 4, and not higher than the liquid surface in the pre-reaction section 5.
[0057] In this embodiment, the system further includes a first circulating heat exchange pipeline 22; the inlet of the first circulating heat exchange pipeline 22 is connected to the pre-reaction section 5 and is located between the liquid surface of the pre-reaction section 5 and the sieve plate 4, and the outlet of the first circulating heat exchange pipeline 22 is connected to the fourth enhanced mass transfer device 6. Figure 1 As shown, the outlet of the first circulating heat exchange pipeline 22 is connected to the fourth enhanced mass transfer device 6 via the second forced circulation pipeline 21. The reaction liquid circulating in the first circulating heat exchange pipeline 22 flows into the fourth enhanced mass transfer device 6 after being heated by the first heat exchanger 26 on the second forced circulation pipeline 21.
[0058] A delivery pipeline 20 is also connected to the first circulating heat exchange pipeline 22, and the outlet of the delivery pipeline 20 is connected to the main reaction section 11. A third heat exchanger 27 is installed on the delivery pipeline 20. In this embodiment, during the middle and later stages of the reaction, the reaction liquid circulating on the first circulating heat exchange pipeline 22 can be input into the main reaction section 11 through the delivery pipeline 20.
[0059] Continue reading Figure 1 The system also includes a light component pipeline 3. This light component pipeline 3 is used to transport the refluxed light components. It is understood that in actual processes, the products generated by the reactor need to be separated to obtain a purer final product, and light components can be obtained during the separation process. These light components can be refluxed back to the pre-reaction section 5 to continue participating in the reaction.
[0060] See also Figure 1 , Figure 3 The first enhanced mass transfer device 14 and the second enhanced mass transfer device 15 are located at the same height and their outlets are staggered. The outlets of the first enhanced mass transfer device 14 and the second enhanced mass transfer device 15 are both provided with a second arc-shaped guide tube 31. The gas-liquid mixture output by the first enhanced mass transfer device 14 and the second enhanced mass transfer device 15 is output in a clockwise or counterclockwise direction under the guidance of the second arc-shaped guide tube 31 (clockwise in the figure).
[0061] Continue reading Figure 1 The system in this embodiment also includes a second circulating heat exchange pipeline 19; the inlet of the second circulating heat exchange pipeline 19 is connected to the main reaction section 11 and is located between the liquid surface of the main reaction section 11 and the first enhanced mass transfer device 14, and the outlet of the second circulating heat exchange pipeline 19 is connected to the second enhanced mass transfer device 15. A second heat exchanger 28 is provided on the second circulating pipeline. In this embodiment, the outlet of the first forced circulation pipeline 17 is connected to the second enhanced mass transfer device 15 via the second circulating heat exchange pipeline 19, and a fourth heat exchanger 29 is provided on the first forced circulation pipeline 17.
[0062] Continue reading Figure 1 The system in this embodiment also includes a discharge pipe 18, the inlet of which is connected to the main reaction section 11 and is located between the first enhanced mass transfer device 14 and the liquid surface of the main reaction section 11. In this embodiment, the inlet of the discharge pipe 18 is connected to the main reaction section 11 via a second circulating heat exchange pipe 19.
[0063] Continue reading Figure 1 The bottom of the main reaction section 11 is also connected to an emptying pipe 16. In this embodiment, the inlet of the first forced circulation pipe 17 is connected to the main reaction section 11 via the emptying pipe 16.
[0064] It is understandable that pumps, valves, etc. can be installed on each pipeline as needed to facilitate the flow of materials in the pipelines and to control the pipelines. This will not be elaborated on further.
[0065] This embodiment also provides a water-saving enhanced reaction method for the carbonylation of methanol to produce acetic acid, which uses the system described in the above embodiment to prepare acetic acid.
[0066] The specific steps of this embodiment are as follows: First, the pre-reaction section reaction begins. Industrial methanol with a purity >99.5% (containing a small amount of water or other impurities) is used. The rhodium complex and the co-catalyst iodomethane are mixed in a specific ratio in the catalyst co-solvent lithium propionate to form a homogeneous catalytic system (water content 1%). The catalyst concentration is 850ppm-950ppm. Both the raw materials and the catalyst are preheated to 160-180℃. After reaching the temperature, they are fed into the pre-reaction section via the first catalyst pipeline and the first methanol pipeline, respectively. CO gas is pressurized to 10-20 atm and introduced into the main reaction section via the carbon monoxide pipeline. The venting pipeline is opened to allow CO to enter the pre-reaction section. The first circulating heat exchange pipeline and the second forced circulation pipeline are opened, and the reaction is allowed to proceed for 20 minutes. The CO partial pressure is stabilized (10-20 atm) to ensure that CO is fully dissolved in the liquid phase. The rhodium complex and the co-catalyst iodomethane are then mixed in a specific ratio in the catalyst co-solvent lithium propionate to form a homogeneous catalytic system, with a catalyst concentration also of 850ppm-950ppm. After 20 minutes, the second catalyst pipeline was opened to begin the main reaction section. The infusion pipeline was opened to allow the pre-reaction section reaction solution to enter the main reaction section. Simultaneously, the second circulating heat exchange pipeline and the first forced circulation pipeline were opened. After the reaction was completed, the methanol conversion rate and acetic acid yield were measured.
[0067] Table 1 below shows the methanol conversion rate and acetic acid yield at different catalyst concentrations and reaction temperatures in this example.
[0068] Table 1. Reaction results of Example 1
[0069]
[0070] Example 2
[0071] The only difference between this embodiment and Embodiment 1 is that the outlets of the third and fourth enhanced mass transfer devices are opposite each other, and the first arc-shaped guide tube is not provided.
[0072] Table 2 below shows the methanol conversion rate and acetic acid yield at different catalyst concentrations and reaction temperatures in this example.
[0073] Table 2 Reaction results of Example 2
[0074]
[0075] Example 3
[0076] The only difference between this embodiment and Embodiment 1 is that a second arc-shaped guide tube is not provided.
[0077] Table 3 below shows the methanol conversion rate and acetic acid yield at different catalyst concentrations and reaction temperatures in this example.
[0078] Table 3 Reaction results of Example 3
[0079]
[0080] Example 4
[0081] The only difference between this embodiment and Example 1 is the water content in the catalyst system. This embodiment was applied under the conditions of a catalyst concentration of 850 ppm, a reaction temperature of 160°C, a pre-reaction zone reaction time of 40 min, and a main reaction zone reaction time of 2.5 h. The results are shown in Table 4.
[0082] Table 4 Reaction results of Example 4
[0083]
[0084] Comparative Example 1
[0085] The only difference between this embodiment and Embodiment 1 is that the outlets of the first enhanced mass transfer device and the second enhanced mass transfer device are opposite each other, and the first arc-shaped guide tube is not provided.
[0086] Table 5 below shows the methanol conversion rate and acetic acid yield at different catalyst concentrations and reaction temperatures in this example.
[0087] Table 5 Results of the reaction in Comparative Example 1
[0088]
[0089] As can be seen from the data in Tables 1-5 above, the technical solution of this application can achieve better methanol conversion and acetic acid yield under the premise of low catalyst water content. Furthermore, according to the data shown in Table 4, the technical solution of this application can still achieve a methanol conversion rate of over 97% under a water content of 0.8%, which is 12% higher than the traditional technology, and the experimental temperature is controlled below 180℃, saving reaction energy consumption. At the same time, due to the reduced water content, the time and cost of subsequent product distillation can be greatly reduced, simplifying post-processing operations.
[0090] Comparing Tables 1 and 2, it can be seen that the methanol conversion rate and acetic acid yield under each experimental condition in Table 1 are better than those in Table 2. This may be because the relative arrangement of the two enhanced mass transfer devices in Example 2 resulted in a dead zone in the pre-reaction section, which accelerated catalyst precipitation and led to poor reaction performance in the pre-reaction section.
[0091] Comparing Tables 1 and 3, it can be seen that the methanol conversion rate and acetic acid yield under each experimental condition in Table 1 are better than those in Table 3. This may be because the use of an arc-shaped guide tube in Example 1 improved the guiding effect on the microbubble flow output from the enhanced mass transfer device, thereby increasing the stirring effect on the reaction solution and enhancing the reaction effect.
[0092] Comparing Tables 1 and 5, it can be seen that the methanol conversion rate and acetic acid yield under each experimental condition in Table 1 are better than those in Table 5. This may be because the relative arrangement of the two enhanced mass transfer devices in Comparative Example 1 resulted in a dead zone in the main reaction section, which accelerated catalyst precipitation and led to poor reaction performance in the main reaction section.
[0093] In summary, the system of this invention can achieve better methanol conversion and acetic acid yield under conditions of lower catalyst water content, which can effectively reduce the energy consumption and cost of acetic acid production. Applying this system to the mass production of acetic acid can significantly improve economic benefits.
[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.
Claims
1. A water-saving enhanced reaction system for the carbonylation of methanol to produce acetic acid, characterized in that, include: The reactor, the first catalyst pipeline, the second catalyst pipeline, the first methanol pipeline, the second methanol pipeline, and the carbon monoxide pipeline; both the first catalyst pipeline and the second catalyst pipeline are used to transport a catalyst mixture, the catalyst mixture including a rhodium catalyst and lithium propionate; The reactor includes a pre-reaction section and a main reaction section, with the pre-reaction section located above the main reaction section. The central axis of the main reaction section coincides with that of the pre-reaction section, and the diameter of the main reaction section is 1.5-2 times the diameter of the pre-reaction section. The upper part of the main reaction section is connected to the pre-reaction section via a venting pipe, and the bottom of the pre-reaction section is connected to the main reaction section via a liquid delivery pipe. The outlets of the first catalyst pipeline and the first methanol pipeline are both connected to the pre-reaction section, and the second catalyst pipeline and the second methanol pipeline are both connected to the main reaction section; The main reaction section is equipped with a first enhanced mass transfer device and a second enhanced mass transfer device. The first enhanced mass transfer device and the second enhanced mass transfer device are located at the same height and their outlets are staggered. The outlet of the carbon monoxide pipeline is connected to the first enhanced mass transfer device, and the bottom of the main reaction section is connected to the second enhanced mass transfer device via a first forced circulation pipeline.
2. The enhanced reaction system according to claim 1, characterized in that, The pre-reaction section is equipped with a third enhanced mass transfer device and a fourth enhanced mass transfer device, which are located at the same height and have staggered outlets. The outlet of the ventilation pipeline is connected to the third enhanced mass transfer device. The bottom of the pre-reaction section is connected to the fourth enhanced mass transfer device via a second forced circulation pipeline.
3. The enhanced reaction system according to claim 2, characterized in that, The outlets of the third and fourth enhanced mass transfer devices are both equipped with first arc-shaped guide tubes. The gas-liquid mixtures output by the third and fourth enhanced mass transfer devices are both output in a clockwise or counterclockwise direction under the guidance of the first arc-shaped guide tubes.
4. The enhanced reaction system according to claim 3, characterized in that, The pre-reaction section is provided with multiple layers of sieve plates, which are located vertically between the third enhanced mass transfer device and the liquid surface in the pre-reaction section; the outlet of the first catalyst pipeline is not lower than the lowest sieve plate of the multiple layers of sieve plates, and not higher than the liquid surface in the pre-reaction section.
5. The enhanced reaction system according to claim 4, characterized in that, It also includes a first circulating heat exchange pipeline; the inlet of the first circulating heat exchange pipeline is connected to the pre-reaction section and is located between the liquid surface of the pre-reaction section and the sieve plate, and the outlet of the first circulating heat exchange pipeline is connected to the fourth enhanced mass transfer device.
6. The enhanced reaction system according to claim 1, characterized in that, The outlets of the first and second enhanced mass transfer devices are both provided with second arc-shaped guide tubes. The gas-liquid mixtures output by the first and second enhanced mass transfer devices are both output in a clockwise or counterclockwise direction under the guidance of the second arc-shaped guide tubes.
7. The enhanced reaction system according to claim 1, characterized in that, It also includes a second circulating heat exchange pipeline; the inlet of the second circulating heat exchange pipeline is connected to the main reaction section and is located between the liquid surface of the main reaction section and the first enhanced mass transfer device, and the outlet of the second circulating heat exchange pipeline is connected to the second enhanced mass transfer device.
8. The enhanced reaction system according to any one of claims 1-7, characterized in that, It also includes a discharge pipeline, the inlet of which is connected to the main reaction section and the inlet of which is located between the first enhanced mass transfer device and the liquid surface of the main reaction section.
9. The enhanced reaction system according to any one of claims 1-7, characterized in that, A condenser is connected to the top of the pre-reaction section, and the bottom of the condenser is connected to the pre-reaction section via a return pipe. After the gas at the top of the pre-reaction section is condensed by the condenser, the liquid phase material flows back to the pre-reaction section via the return pipe.