Process for preparing methyl methacrylate by using riser reaction system

Abstract

The invention discloses a process for preparing methyl methacrylate by using a riser reaction system, and belongs to the technical field of methyl methacrylate production. According to the invention, methyl methacrylate is produced through one-step oxidation esterification reaction of methanol and methylacrolein by using a riser reaction system; the reaction system mainly comprises a liquid inlet, a gas-liquid mixing inlet, a riser reactor, a three-phase rapid separator, a settling separator, a gas outlet, a particle baffle, a liquid outlet, a particle return pipe, a particle control valve and other main components. According to the process, the riser reactor is used for replacing a traditional continuous stirring kettle and a slurry bed reactor, so that the backmixing degree in the reactor is reduced, the reaction efficiency is improved, the reaction time is shortened, the methylacrolein conversion rate, the methyl methacrylate selectivity and the oxygen utilization rate are increased, and the economic benefit and the safety of the device are improved; the device is more beneficial to amplification and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of methyl methacrylate production and relates to a process for preparing methyl methacrylate by using a riser reaction system. Background Art

[0002] Methyl methacrylate (MMA) is an important organic chemical raw material, primarily used in the production of organic glass (polymethyl methacrylate, PMMA), coatings, and emulsion resins. PMMA boasts higher light transmittance than ordinary glass, and its high-temperature tolerance, chemical stability, ease of processing, and high wear resistance make it widely used in industries such as high-end lighting, aerospace, home appliances, and construction. As of 2024, my country's methyl methacrylate production capacity will be approximately 2.655 million tons, and is projected to exceed 3 million tons by 2025. After nearly 100 years of development, MMA is synthesized using the acetone cyanohydrin (ACH) method, the isobutylene method, and the ethylene method.

[0003] The ACH process was first industrialized by Brunner Mond in the UK in 1937. It remains the oldest and most widely used process today. This process uses HCN and acetone as the main raw materials. Acetone cyanohydrin is produced over an alkaline catalyst, then reacts with excess sulfuric acid to form methacrylamide sulfate. Finally, methacrylamide sulfate undergoes hydrolysis and esterification with water and methanol to produce MMA. This process is simple, technically mature, and highly competitive. However, the HCN raw material is highly toxic, presenting significant limitations in its use and transportation. Furthermore, every ton of MMA produced produces 1.2 tons of ammonium bisulfite as a byproduct, significantly polluting the environment. Consequently, new ACH-based methyl methacrylate production facilities are no longer being built in China.

[0004] There are two ethylene-based routes: the BASF process, which converts ethylene into MMA via propionaldehyde, and the Alpha process, which converts ethylene into methyl propionate. The BASF process uses ethylene as a raw material, first reacting it with synthesis gas in a hydroformylation reaction to produce propionaldehyde. Propionaldehyde then reacts with methanol in an aldol condensation reaction to produce methacrolein. Methacrolein is oxidized to produce methacrylic acid, which is then esterified with methanol to produce methyl methacrylate. This method has a high atomic efficiency of up to 64%, and the raw materials, such as ethylene, synthesis gas, and methanol, are widely available, making the production process environmentally friendly. However, this process involves numerous production steps and the presence of methacrylic acid, which requires high equipment investment and production costs. The Alpha process, on the other hand, uses ethylene as a raw material, reacting it with methanol and carbon monoxide over a palladium-based homogeneous catalyst to produce methyl propionate. Methyl propionate then reacts with formaldehyde in an aldol condensation reaction to produce MMA. This method requires high catalyst performance.

[0005] The isobutylene route for the synthesis of MMA was first developed by Asahi Kasei in Japan in 1976 and achieved industrialization in 1983. After decades of development, the isobutylene route has become the second most popular production method for MMA, second only to the ACH process. Currently, two isobutylene processes have been developed. The two-step isobutylene process produces methacrolein over a Mo-Bi catalyst. The methacrolein is then oxidized to methacrylic acid over a phosphorus-molybdenum catalyst, and then esterified with methanol to produce MMA. To address the long process and equipment corrosion associated with the methacrylic acid intermediate produced by the three-step isobutylene process, Asahi Kasei developed the two-step isobutylene process in 1992. This process combines the last two steps into a single-step oxidative esterification of methanol and methacrolein to produce MMA, significantly shortening the process and increasing MMA yield. However, the one-step oxidative esterification process requires a high catalyst requirement, and the isobutylene raw material is relatively scarce, making it unsuitable for large-scale production.

[0006] A comparative analysis of the above methods reveals that the ACH method, due to its use of highly toxic HCN and its severe pollution, will eventually be phased out of the market. The Alpha method has high technical barriers, while the other ethylene and isobutylene methods both use methacrolein as an intermediate. If the production of MMA through the one-step oxidative esterification of methacrolein can be achieved, it will help improve MMA production efficiency and increase the economic efficiency of the plant operation. Methacrolein can be obtained simultaneously from both ethylene and isobutylene, and the technology is relatively mature. Flexible planning can also be implemented based on local ethylene or isobutylene resources. The key lies in achieving efficient production of MMA through the one-step oxidative esterification of methacrolein.

[0007] CN108607550A discloses a gold catalyst for producing methyl methacrylate and its application. This catalyst is used to directly oxidize and esterify methanol, methacrolein, oxygen, or air to produce methyl methacrylate (MMA), featuring a green and simple process. CN109331839A discloses a preparation method for a catalyst for producing methyl methacrylate and its application. The catalyst has outstanding reaction performance, a low gold loading, a simple preparation process, convenient operation, excellent activity and stability, and is inexpensive. The catalyst also has high methacrolein conversion and MMA selectivity, making it suitable for industrial production. CN109395732B discloses a catalyst for the low-cost and efficient production of methyl methacrylate and its preparation method. The catalyst has a gold loading of only 0.05 wt% to 0.98 wt%, resulting in uniform catalyst particles, high activity, and low cost, making it suitable for industrial production. CN112823876A discloses a catalyst for preparing MMA by direct oxidative esterification and its preparation method. The disclosed catalyst consists of a support and an active component modified by an oxidant and supported on the support, wherein the support is mostly porous porcelain balls embedded with alkaline earth metals, and the active component is a composite oxide of gold and nickel. The catalyst is applied to the catalytic direct oxidative esterification reaction to prepare MMA, with high catalytic activity and high selectivity, and the mechanical strength and chemical stability of the catalyst are also greatly improved. The above invention patent mainly discloses a series of catalysts for the one-step oxidative esterification of methacrolein to produce methyl methacrylate, but existing research has remained at the catalyst development level, and there has been no report on industrial production of the above process. There is little research related to the reactor for the one-step oxidative esterification of MMA. The one-step oxidative esterification reaction process of methacrolein is a typical gas-liquid-solid three-phase reaction process, but its reaction process has a strong exothermicity and the risk of explosion in the system. Therefore, the concentration of oxygen in the gas phase space in the reactor must be strictly controlled. Common gas-liquid-solid three-phase reactors mainly include stirred tank reactors, fixed bed reactors, and slurry bed reactors. Research has found that stirred tank reactors often use agitators to mix liquid materials and break up bubbles, but agitators require high catalyst strength. Experiments have shown that continuous operation for more than 500 hours can lead to catalyst breakage, increasing production costs and impacting subsequent liquid-solid filtration systems. Fixed-bed reactors, on the other hand, have high catalyst concentrations and large catalyst particle sizes, resulting in slow heat and mass transfer rates and difficult temperature control within the reactor. Methacrolein also tends to self-aggregate, attaching to the catalyst surface or pores. This not only reduces the catalyst's service life but also increases the reactor's pressure drop, ultimately leading to unplanned downtime.The slurry bed reactor is a commonly used gas-liquid-solid three-phase reactor characterized by its simple structure, lack of mechanical equipment, and high heat and mass transfer rates. It is a novel gas-liquid-solid three-phase reactor and has been widely used in heavy oil catalyst hydrogenation, low-carbon hydrocarbon oxidation, and industrial waste gas and wastewater treatment. However, in the one-step oxidative esterification of methacrolein to methyl methacrylate, due to the fully mixed flow in the slurry bed reactor, the liquid requires sufficient residence time to achieve the required methacrolein conversion rate. Furthermore, prolonged contact between the catalyst and materials such as MMA can shorten the catalyst's service life. Summary of the Invention

[0008] In view of this, an object of the present invention is to provide a process for producing methyl methacrylate using a gas-liquid-solid riser reactor system. In this reactor, the gas, liquid, and solid phases all move upward along the riser reactor, contacting and reacting during the movement, and having high interphase contact efficiency. This reactor can effectively reduce the degree of backmixing of the liquid and solid phases in the reactor, shorten the reaction time, and improve the reaction efficiency and product selectivity. At the same time, it can also improve the utilization rate of oxygen, reduce the safety hazards caused by excessively high oxygen concentration at the top of the reactor, and is more conducive to industrial scale-up, and has great application value.

[0009] In order to achieve the above object, the present invention provides the following technical solutions: The present invention provides a process for preparing methyl methacrylate by using a riser reaction system. The reaction system mainly comprises a liquid inlet 1, a gas-liquid mixing inlet 2, a riser reactor 3, a three-phase rapid separator 4, a sedimentation separator 5, a gas outlet 6, a particle baffle 7, a liquid outlet 8, a particle return pipe 9 and a particle control valve 10; the riser reactor 3, the three-phase rapid separator 4, the sedimentation separator 5 and the particle return pipe 9 are connected in series in sequence, the bottom end of the riser reactor 3 is provided with a gas-liquid mixing inlet 2, and a liquid drive valve is provided at the gas-liquid mixing inlet 2. A movable bubble generator is provided, a liquid inlet 1 is provided on the connecting pipeline between the particle return pipe 9 and the riser reactor 3, and a particle control valve 10 is provided at the bottom of the particle return pipe 9; the inlet of the three-phase rapid separator 4 is connected to the top outlet of the riser reactor 3, the outlet of the three-phase rapid separator 4 is located inside the sedimentation separator 5, a gas outlet 6 is provided on the top of the sedimentation separator 5, a liquid outlet 8 is provided on the side wall of the sedimentation separator 5, a particle baffle 7 is provided at the liquid outlet 8, and the bottom of the sedimentation separator 5 is connected to the particle return pipe 9; The process comprises the following steps: (1) A mixture of methanol and methacrolein enters the riser reactor in two streams. A mixture with a volume percentage of 5 to 40% is introduced into the liquid phase inlet 1 downstream of the particle control valve 10 to deliver catalyst particles to the bottom of the riser reactor 3. The catalyst concentration in the riser reactor is controlled by the particle control valve 10. (2) After the operation is stabilized, the gas-liquid mixture consisting of the remaining mixed material in step (1) and the oxidizing gas is introduced into the gas-liquid mixing inlet 2 at the bottom of the riser reactor 3. After being fully mixed, the mixture moves upward along the riser reactor 3 and an oxidative esterification reaction occurs. At the top of the riser reactor 3, the mixture passes through the three-phase rapid separator 4 to achieve preliminary separation of the gas, liquid and solid phases, and then enters the sedimentation separator 5 for sedimentation separation. The gas is discharged from the gas outlet 6 at the top of the sedimentation separator 5, and the liquid phase passes over the particle baffle 7 and is discharged through the liquid outlet 8. The catalyst particles are returned to the riser reactor 3 from the bottom of the sedimentation separator 5 through the particle return pipe 9 to participate in the reaction again.

[0010] Based on the above technical solution, further, the structure of the bubble generator is one or a combination of two or more of Venturi type, double tangential type, swirl type, dissolved air-release type, jet type, porous mode, vortex type and ejector array type.

[0011] Based on the above technical solution, further, the three-phase rapid separator 4 is a three-phase cyclone separator, and the sedimentation separator 5 is composed of a hollow cylinder with a sealed top and a conical bottom.

[0012] Based on the above technical solution, a three-phase cyclone separator is further installed on the top of the riser reactor 3, and its structure is one or a combination of two or more of column type, tube column type, multi-tube bundle type, and volute type. Preferably, a volute type three-phase cyclone separator is used.

[0013] Based on the above technical solution, further, the molar ratio of methanol to methacrolein is 1:1~1:50.

[0014] Based on the above technical solution, further, the oxidizing gas is oxygen or a mixture of oxygen and nitrogen, wherein the volume fraction of oxygen is 10% to 100%; the bubble diameter is controlled to be 1 to 5000 μm; Based on the above technical solution, further, the catalyst is a supported catalyst, the active component of which is one or a combination of two or more of copper oxide, zinc oxide, gold, palladium, gold-palladium alloy, and palladium-copper alloy, the catalyst particle size is 30-1000 μm, and the particle density is 1500-5000 kg / m 3 .

[0015] Based on the above technical solution, further, the diameter of the riser reactor 3 is 20-500 mm, and the height is 0.5-50 m.

[0016] Based on the above technical solution, further, the superficial velocity of the liquid in the riser reactor 3 is 0.5-800 m / h, and the catalyst concentration is 0.1-30 wt%.

[0017] Based on the above technical solution, further, the pressure of the riser reactor 3 is normal pressure to 25 MPa, and the temperature is 20 to 200°C.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) The catalyst particles in the riser reactor of the present invention move upward under the drag force of the liquid phase. Compared with the conventional slurry bed reactor, the degree of backmixing is extremely small, and a higher conversion rate can be achieved in a reactor of the same volume, or the desired conversion rate can be achieved in a reactor of smaller size, thereby improving the space utilization of the reactor.

[0019] (2) In the riser reactor described in the present invention, the gas moves upward in the form of bubbles along the riser. By controlling the bubble generator at the liquid-solid phase inlet, the size of the bubbles in the bed can be effectively controlled to be small and uniform. Under the combined action of buoyancy and drag, the bubbles move at a faster speed, and the gas phase is fully in contact with the liquid-solid phase, thereby increasing the contact area and mass transfer rate between the gas and liquid phases, thereby improving the efficiency of the reactor.

[0020] (3) The riser reactor of the present invention is used for the one-step oxidative esterification of methacrolein to produce methyl methacrylate, which can increase the reaction rate, shorten the reaction time, improve the conversion rate of methacrolein and the selectivity of methyl methacrylate, reduce the degree of self-polymerization of a large amount of methacrolein in the reactor, improve the effective utilization rate of raw materials, and increase the economy of the device.

[0021] (4) The riser reactor of the present invention is used for the one-step oxidative esterification of methacrolein to produce methyl methacrylate. The reactor has high space utilization, and the catalyst can circulate. This can extend the service life of the catalyst. The reactor has a simple structure, flexible and easy operation, and the riser reactor facilitates reactor scale-up. Therefore, the present invention has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention, the drawings related to the embodiments are briefly introduced below.

[0023] Figure 1This is a schematic diagram of the one-step oxidative esterification process for producing methyl methacrylate using a riser reactor in Example 1. In the figure, 1 is a liquid inlet, 2 is a gas-liquid mixed inlet, 3 is a riser reactor, 4 is a three-phase rapid separator, 5 is a sedimentation separator, 6 is a gas outlet, 7 is a particle baffle, 8 is a liquid outlet, 9 is a particle return pipe, and 10 is a particle control valve.

[0024] Figure 2 This is a schematic diagram of the one-step oxidative esterification process for producing methyl methacrylate using a gas-liquid-solid three-phase slurry bed reactor in Comparative Example 1. In the figure, 201 is a liquid feed port, 202 is a gas inlet, 203 is a bubble generator, 204 is a gas outlet, 205 is a liquid outlet, and 206 is a catalyst filter.

[0025] Figure 3 This is a schematic diagram of the one-step oxidative esterification process for producing methyl methacrylate using a gas-liquid-solid three-phase stirred tank reactor in Comparative Example 2. In the figure, 301 is a liquid feed port, 302 is a gas inlet, 303 is a bubble generator, 304 is a gas outlet, 305 is a liquid outlet, 306 is a catalyst filter, 307 is a stirring paddle, and 308 is a motor. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments obtained without creative work all fall within the scope of protection of the present invention.

[0027] Example 1 This embodiment provides a process for preparing methyl methacrylate by one-step oxidative esterification using a riser reaction system, as shown in the schematic diagram. Figure 1, the figure shows the main structure of the reactor and the inlets and outlets of related materials. The reactor mainly includes liquid inlet 1, gas-liquid mixing inlet 2, riser reactor 3, three-phase rapid separator 4, sedimentation separator 5, gas outlet 6, particle baffle 7, liquid outlet 8, particle return pipe 9 and particle control valve 10 and other main components; the riser reactor 3, three-phase rapid separator 4, sedimentation separator 5 and particle return pipe 9 are connected in series in sequence, the bottom end of the riser reactor 3 is provided with a gas-liquid mixing inlet 2, the gas-liquid mixing inlet 2 is provided with a liquid-driven bubble generator, the particle return pipe 9 is provided with a liquid-driven bubble generator, the particle return pipe 9 is provided with a liquid-driven bubble generator, the particle return pipe 9 is provided with a liquid-driven bubble generator, the particle return pipe 9 is provided with a liquid-liquid mixing inlet 2, the gas-liquid mixing inlet 2 is provided with a liquid-driven bubble generator, the particle return pipe 9 is provided with a liquid-liquid mixing inlet 2, the gas-liquid mixing inlet 2 is provided with a liquid-driven bubble generator, the particle return pipe 9 is provided with a gas ... A liquid inlet 1 is provided on the connecting pipeline between the pipe 9 and the riser reactor 3, and a particle control valve 10 is provided at the bottom of the particle return pipe 9; the inlet of the three-phase rapid separator 4 is connected to the top outlet of the riser reactor 3, and the outlet of the three-phase rapid separator 4 is located inside the sedimentation separator 5. The sedimentation separator 5 consists of a hollow cylinder with a sealed top and a conical bottom. The top of the sedimentation separator 5 is provided with a gas outlet 6, and the side wall of the sedimentation separator 5 is provided with a liquid outlet 8. A particle baffle 7 is provided at the liquid outlet 8. The bottom of the sedimentation separator 5 is connected to the particle return pipe 9; The liquid phase in the reactor is a mixture of methanol and methacrolein, with a molar ratio of methanol to methacrolein of 10:1. The gas used in the reaction is a mixture of oxygen and nitrogen, with an oxygen volume fraction of 50%. The gas feed flow rate is 10 ml / min, and the diameter of most bubbles is controlled to be 50-500 μm. The catalyst used in the reaction is a supported nano-gold catalyst with a particle size of 50-200 μm, a median particle size of approximately 85 μm, and a particle density of 2100 kg / m 3 The riser reactor had an inner diameter of 50 mm and a height of 15 m. The superficial velocity of the liquid in the riser reactor was 30 m / h, and the catalyst concentration was 15 wt%. The operating pressure of the riser reactor was 0.5 MPa, and the reactor temperature was controlled at 80°C. The specific process of preparing methyl methacrylate by one-step oxidative esterification using a riser reactor is as follows: A mixture of methanol and methacrolein (methanol and methacrolein are mixed in a molar ratio of 10:1) enters the reactor in two streams, 1 / 5 of which is introduced through the liquid phase inlet 1 downstream of the particle control valve to deliver catalyst particles to the bottom of the riser reactor 3, and the remaining mixed liquid is introduced through the gas-liquid mixing inlet 2 at the bottom of the riser reactor 3. The catalyst concentration in the reactor is controlled by the particle control valve 10 to achieve a catalyst concentration of 15 wt%. After the operation stabilizes, the gas-liquid mixture (the volume ratio of oxygen to nitrogen in the mixed gas is 5:5) introduced through the gas-liquid mixing inlet 2 at the bottom of the riser reactor 3 is fully contacted and mixed, and then moves upward along the riser, contacting and reacting while moving, and the pressure of the reactor is controlled at 0.5 MPa, and the reactor temperature was controlled at 80°C. At the top of the riser reactor, the gas, liquid, and solid phases were initially separated by a three-phase rapid separator 4 before entering a sedimentation separator 5 for further sedimentation separation. Gas was discharged from the top gas outlet 6, while the liquid phase passed through a particle baffle 7 and was discharged through a liquid outlet 8 to enter the subsequent separation system. Catalyst particles were returned to the reactor from the bottom of the sedimentation separator 5 through a particle return pipe 9 to participate in the reaction again. After the device operated continuously for one hour, samples were taken from both the gas outlet 6 and the liquid outlet 8 for composition analysis, and the reaction performance was calculated, primarily including parameters such as methacrolein conversion, methyl methacrylate selectivity, and oxygen utilization. The device operated continuously for at least 24 hours, with sampling and analysis conducted once per hour. The final test results were averaged. The specific results are shown in Table 1.

[0028] Comparative Example 1 This comparative example adopts a gas-liquid-solid three-phase slurry bed reactor, the structure of which is as follows Figure 2 As shown, the reactor diameter is 200 mm, and the effective volume (below the liquid outlet) is the same as that of the downer reactor in Example 1. Liquid feedstock enters through a liquid feed port 201 at the bottom of the reactor, while gas enters through a gas inlet 202 on the sidewall of the reactor bottom. Bubbles are formed by a bubble generator 203 before entering the reactor and mixing with the liquid. The catalyst is uniformly mixed within the reactor under the action of the bubbles and catalyzes the oxidative esterification reaction. After the reaction, the gas exits the system through a gas outlet 204 at the top of the reactor, while the liquid exits through a liquid outlet 205. A catalyst filter 206 is installed at the liquid outlet to allow the catalyst to remain in the reactor. In this comparative example, to ensure a high methacrolein conversion rate, a liquid residence time of 60 minutes was required. The liquid feed rate was 6.25 L / h. Other parameters, such as the feedstock ratio, catalyst concentration, reaction temperature, and pressure, remained the same as in Example 1. Samples were taken at the gas and liquid outlets for analysis, and the methacrolein conversion, methyl methacrylate selectivity, and oxygen utilization were calculated. The results are shown in Table 1.

[0029] Comparative Example 2 In this comparative example, a gas-liquid-solid three-phase stirred tank reactor was used. The reactor structure is as follows: Figure 3 As shown, the basic structure of the reactor is the same as that of the slurry bed reactor used in Comparative Example 1, except that a stirring paddle 307 driven by a motor 308 is added to the reactor. The liquid raw material enters from the liquid phase feed port 301 at the bottom of the reactor, and the gas enters from the gas inlet 302 on the side wall of the bottom of the reactor. After forming bubbles through the bubble generator 303, it enters the reactor and mixes with the liquid. The catalyst is evenly mixed in the reactor under the action of bubbles and stirring and catalyzes the oxidative esterification reaction; after the reaction, the gas is discharged from the gas outlet 304 at the top of the reactor, and the liquid is discharged from the liquid outlet 305. A catalyst filter 306 is installed at the liquid outlet position so that the catalyst can remain in the reactor. Other parameters such as raw material ratio, feed rate, catalyst concentration, reaction temperature and pressure are consistent with those in Example 1. Sampling and analysis are performed at the gas and liquid phase outlets, and the methacrolein conversion rate, methyl methacrylate selectivity and oxygen utilization rate are calculated. The specific results are shown in Table 1.

[0030] Table 1. Comparison of the effects of one-step oxidative esterification of methanol and methacrolein to methyl methacrylate using different reactors

[0031] As shown in Table 1, the riser reactor of the present invention achieves a methacrolein conversion rate of 87.3%, a methyl methacrylate selectivity of 98.1%, and an oxygen utilization rate of 42.8% for the one-step oxidative esterification of methanol and methacrolein to methyl methacrylate. Compared with existing continuous stirred tank reactors and slurry bed reactors, the reaction time is significantly shortened and the reaction efficiency is significantly improved.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for preparing methyl methacrylate using a riser reaction system, characterized in that: The reaction system mainly includes a liquid inlet, a gas-liquid mixing inlet, a riser reactor, a three-phase rapid separator, a sedimentation separator, a gas outlet, a particle baffle, a liquid outlet, a particle return pipe and a particle control valve; the riser reactor, the three-phase rapid separator, the sedimentation separator and the particle return pipe are connected in series in sequence, the bottom end of the riser reactor is provided with a gas-liquid mixing inlet, a bubble generator is provided at the gas-liquid mixing inlet, a liquid inlet is provided on the connecting pipeline between the particle return pipe and the riser reactor, and a particle control valve is provided at the bottom of the particle return pipe; the inlet of the three-phase rapid separator is connected to the top outlet of the riser reactor, the outlet of the three-phase rapid separator is located inside the sedimentation separator, the top of the sedimentation separator is provided with a gas outlet, the side wall of the sedimentation separator is provided with a liquid outlet, a particle baffle is provided at the liquid outlet, and the bottom of the sedimentation separator is connected to the particle return pipe; The process comprises the following steps: (1) The mixture of methanol and methacrolein enters the riser reactor in two streams. The mixture with a volume percentage of 5-40% is introduced into the liquid phase inlet downstream of the particle control valve to deliver catalyst particles to the bottom of the riser reactor. The catalyst concentration in the riser reactor is controlled by the particle control valve. (2) After the operation is stabilized, the gas-liquid mixture consisting of the remaining mixed material in step (1) and the oxidizing gas is introduced into the gas-liquid mixing inlet at the bottom of the riser reactor. After being fully mixed, the mixture moves upward along the riser reactor and an oxidative esterification reaction occurs. At the top of the riser reactor, the mixture passes through a three-phase rapid separator to achieve preliminary separation of the gas, liquid and solid phases. The mixture then enters the sedimentation separator for sedimentation separation. The gas is discharged from the gas outlet at the top of the sedimentation separator, and the liquid phase passes over the particle baffle and is discharged through the liquid outlet. The catalyst particles are returned to the riser reactor from the bottom of the sedimentation separator through the particle return pipe to participate in the reaction again.

2. The process according to claim 1, characterized in that The structure of the bubble generator is one or a combination of two or more of the following: Venturi type, double tangential type, swirl type, dissolved air-release type, jet type, multi-hole mode, vortex type and ejector array type.

3. The process according to claim 1, characterized in that The three-phase rapid separator is a three-phase cyclone separator, and the sedimentation separator consists of a hollow cylinder with a sealed top and a conical bottom.

4. The process according to claim 1, characterized in that A three-phase cyclone separator is installed on the top of the riser reactor. Its structure is one of column type, tube column type, multi-tube bundle type, and volute type or a combination of two or more. Preferably, a volute type three-phase cyclone separator is used.

5. The process according to claim 1, characterized in that The molar ratio of methanol to methacrolein is 1:1~1:

50.

6. The process according to claim 1, characterized in that The oxidizing gas is oxygen or a mixture of oxygen and nitrogen, wherein the volume fraction of oxygen is 10% to 100%; the bubble diameter is controlled to be 1 to 5000 μm.

7. The process according to claim 1, characterized in that The catalyst is a supported catalyst, and its active component is one or a combination of two or more of copper oxide, zinc oxide, gold, palladium, gold-palladium alloy, and palladium-copper alloy. The catalyst particle size is 30-1000 μm; the particle density is 1500-5000 kg / m 3 .

8. The process according to claim 1, characterized in that The diameter of the riser reactor is 20~500 mm and the height is 0.5~50 m.

9. The process according to claim 1, characterized in that The liquid superficial velocity in the riser reactor is 0.5~800 m / h, and the catalyst concentration is 0.1~30 wt%.

10. The process according to claim 1, characterized in that The pressure of the riser reactor is atmospheric pressure ~ 25MPa, and the temperature is 20 ~ 200℃.

Images