Reaction device and process for producing oxalate by oxidative coupling of nitrous ester and CO

Abstract

The present invention relates to a reaction device and process for the oxidative coupling of nitrite and CO to produce oxalate ester, which includes a fluidized bed reactor (100) and a fixed bed reactor (200) connected in series, and the fluidized bed reactor (100) is located upstream of the fixed bed reactor (200). The nitrite and CO are successively subjected to two reactions in the fluidized bed reactor and the fixed bed reactor. By using the fluidized bed, good heat removal and temperature control can be achieved, and medium conversion efficiency can be obtained. Then, by connecting a fixed bed reactor in series, high productivity of a single reactor system can be realized, the investment, energy consumption and total cost per unit output can be reduced, and its competitiveness with the petrochemical route can be improved; a large amount of by-product carbonic acid diester can be produced, further improving the economic benefits of the device.

Description

Technical Field

[0001] The present invention relates to a device and a process for producing ethylene glycol intermediate oxalate by a coal chemical route, and particularly to a method suitable for large-scale production of oxalate by coupling CO with nitrite ester and combining a fluidized bed reactor and a fixed bed reactor. Background Art

[0002] Ethylene glycol is an important basic organic chemical raw material and is mainly used as a polycondensation monomer for polyester. Due to the rapid growth of the polyester industry, the global production capacity of ethylene glycol is close to 40 million tons per year. The traditional production route is based on the petroleum route of ethylene-ethylene oxide. The production in China far cannot meet the demand, and the import volume is very large. The import dependence has been above 70% in the past decade, which seriously restricts the development of China's polyester industry.

[0003] The resource characteristics of China are rich in coal, scarce in oil and poor in gas. Developing a coal chemical route for ethylene glycol production has strategic and practical significance. The coal chemical route for ethylene glycol production includes three reaction steps: (1) Coupling: CO and nitrite ester (methyl ester or ethyl ester) are coupled to produce oxalate ester and co-produce NO. (2) Hydrogenation: Oxalate ester is hydrogenated to produce ethylene glycol and co-produce methyl (ethyl) alcohol. (3) Esterification: NO and methyl (ethyl) alcohol are oxidized and esterified to produce methyl (ethyl) nitrite and co-produce water. The three reactions form a cycle of NO and methyl (ethyl) alcohol. The overall reaction is:

[0004] 2CO + 4H 2 + 0.5O 2 =(CH 2 OH) 2 + H 2 O

[0005] Obviously, this reaction is very close to the reaction of methanol. Therefore, compared with the traditional ethylene-ethylene oxide route, the coal chemical route has significant resource advantages.

[0006] The coal chemical route for ethylene glycol was first invented by Union Carbide Chemicals in the United States and Ube Industries in Japan in the 1980s. Chinese scientists began basic research in the 1990s. Especially since this century, many domestic units have carried out technology development and industrialized in the past decade and developed rapidly. The built + under construction + planned production capacity will reach 15 million tons per year. However, in recent years, due to the low oil price, the coal chemical ethylene glycol route has large losses due to small single-unit production capacity, large investment and high energy consumption, and it is difficult to compete with the petroleum route.

[0007] Therefore, the technical development direction of coal chemical ethylene glycol is how to reduce investment, increase the single-unit (i.e., the production capacity of a single reactor), reduce investment, reduce energy consumption, and improve the competitiveness with the petroleum route.

[0008] In the current technology, the coupling reaction is a bottleneck, with low reaction efficiency, a large recycle of raw materials, and the production capacity of a single reactor being about 50,000 tons per year. The reason is that the shell-and-tube fixed-bed reactor used has low conversion efficiency, generally between 50% and 60%, due to the low reaction temperature (110 - 130°C) and strict control, as well as the limitation of low heat transfer efficiency, resulting in high concentrations of CO and nitrous esters (methyl nitrite MN, ethyl nitrite EN) in the raw material gas. The characteristic of this reaction is that too high a concentration of reactants will instead inhibit the reaction rate due to the adsorption damping effect on the catalyst surface, and the conversion rate will further decrease. Therefore, the traditional shell-and-tube heat-exchanging fixed-bed reactor restricts the efficiency of the existing ethylene glycol coal chemical route, making it difficult to reduce production costs.

[0009] According to the principles of chemical reaction engineering, different reactors have their own advantages and disadvantages. In a gas-solid reaction system, the solution to the heat transfer problem is preferably a fluidized bed reactor. However, for different reactions, there are different specific implementation schemes in combination with the characteristics of the reaction.

[0010] For the CO coupling reaction, Patent Document 201110045611 (Fluidized bed catalyst for preparing oxalate by CO coupling) discloses a palladium catalyst modified with additives such as rhenium, praseodymium, or bismuth, with the selectivity of oxalate increased to more than 99%; 201110045196 (Method for producing oxalate by CO coupling) uses a fluidized bed reactor, and the catalyst is modified with bismuth; 201110045202 (Method for producing oxalate by gas-phase coupling of CO) uses a fluidized bed reactor, and the catalyst is modified with rhenium and silver; 201110045220 (Method for catalytic reaction of gas-phase coupling of CO to produce oxalate) and 201110045609 (Method for gas-phase catalytic coupling of CO gas to produce oxalate) disclose a fluidized bed reactor with a regenerator and a steam stripper, and there is a heat exchanger on the catalyst downcomer, a reactor similar to the traditional petroleum catalytic cracking reactor. The above disclosed technical solutions use the reactor type of traditional petroleum catalyst cracking, which is not suitable for the characteristics of the CO coupling reaction, with a too complex structure, high investment cost, and the conversion efficiency generally not exceeding 80%. Second, the catalyst used has complex components and high costs. Compared with the existing fixed-bed reactor and catalyst technology, the advantages are not obvious, and so far there has been no further development and industrial application. In addition, since the coupling reaction can also produce dimethyl (ethyl) carbonate, which is in high market demand as a solvent for lithium-ion batteries, maximizing the by-production of carbonic diester in the oxalate plant is also a direction for the technological development in this field. Summary of the Invention

[0011] The object of the present invention is to overcome the problems existing in the prior art, such as complex reactor structure, low production capacity, low conversion rate, large investment, and low yield of by-product dimethyl carbonate. A reaction device and process for the oxidative coupling of nitrite and CO to produce oxalate are provided, which have the advantages of simple structure, high production capacity, high conversion efficiency, and high yield of carbonate ester.

[0012] The object of the present invention can be achieved by the following technical solutions: A reaction device for the oxidative coupling of nitrite and CO to produce oxalate, comprising a fluidized bed reactor and a fixed bed reactor connected in series. The fluidized bed reactor is located upstream of the fixed bed reactor, combining the advantages of high heat transfer capacity of the fluidized bed reactor and high conversion rate of the fixed bed reactor, and can simultaneously achieve good temperature control and stable operation of the reactor.

[0013] A filter is also provided on the connecting pipeline between the fluidized bed reactor and the fixed bed reactor for gas-solid separation of fine particle catalysts, which not only completely recovers the catalysts and reduces waste, but also eliminates the blockage of the subsequent fixed bed reaction, ensuring stable and safe operation.

[0014] The fluidized bed reactor includes a bottom gas distribution area, an intermediate reaction area, and a top gas-solid separation area. A gas distributor a is provided in the gas distribution area, catalyst a and heat exchange tubes are filled in the intermediate reaction area, and a gas-solid separator is provided in the gas-solid separation area, ensuring heat transfer to control the reactor temperature while the reaction is carried out, and ensuring uniform distribution of reaction gases and stable reaction operation.

[0015] The heat exchange tubes form a circulation loop with a steam drum through an inlet water pipeline and an outlet water pipeline; multiple parallel heat exchange tubes are uniformly arranged in the reaction area, and catalyst a is filled between the heat exchange tubes, ensuring that excess heat released during the reaction produces steam.

[0016] The particle size of the catalyst a is between 20 and 1000 microns, preferably between 50 and 500 microns.

[0017] Catalyst b and a gas distributor b are installed in the fixed bed reactor, and the particle size of the catalyst b is between 2 and 10 mm, preferably between 4 and 8 mm, reducing the resistance and ensuring high reaction efficiency.

[0018] The fixed bed reactor is an adiabatic reactor, and the catalyst b is spherical, cylindrical, annular or porous cylindrical, preferably annular, with low gas resistance and reduced energy consumption.

[0019] The filter is equipped with a filter tube, which is a microporous metal sintered tube, a ceramic tube, a glass fiber bag or an organic polymer fiber bag, and has three interfaces, which are respectively connected to the top of the upstream fluidized bed reactor through a dusty gas pipeline, connected to the downstream fixed bed reactor through a clean gas pipeline, and then connected to the lower part of the fluidized bed reactor through a catalyst particle reflux pipeline, ensuring rapid and continuous recovery of the catalyst, purification of the reaction gas, and reducing blockage of the downstream fixed bed reactor.

[0020] The device is used to carry out a reaction process for producing oxalic acid ester by oxidative coupling of nitrite and CO, comprising the following steps:

[0021] 1. Primary reaction: the raw gas enters the lower cavity of the fluidized bed reactor through the raw material pipeline, and after being evenly distributed by the gas distributor a, enters the fluidized section (also called the reaction zone) containing the catalyst a, and contacts with the catalyst a to cause a catalytic coupling reaction of CO and methyl nitrite or ethyl nitrite to generate dimethyl oxalate or diethyl oxalate and co-produce NO;

[0022] 2. Heat transfer: The heat released by the coupled reaction in the fluidized bed reactor raises the temperature of the reaction gas to the temperature of the reactor. On the other hand, the excess reaction heat is removed through the heat exchange between the reaction gas and the heat exchange tube, and a water cycle is formed with the steam drum through the inlet and outlet water pipelines to produce steam in the drum.

[0023] 3. Gas-solid separation: The reaction gas obtained by the coupling reaction in the fluidized bed reactor enters the upper gas-solid separation zone for gas-solid separation. The larger catalyst particles entrained by the reaction gas are separated by gravity settling, and the smaller catalyst particles are separated by cyclone in the gas-solid separator. The fine-grained catalyst is transported by the dust-containing gas pipeline to the filter outside the reactor for thorough filtration and separation. The fine-particle catalyst obtained by filtration is returned to the fluidized section of the fluidized bed reactor through the catalyst reflux pipeline for recycling. The clean reaction gas obtained enters the downstream fixed bed reactor through the clean pipeline.

[0024] 4. Secondary reaction: The clean reaction gas undergoes a second reaction in the fixed bed reactor to achieve high conversion efficiency.

[0025] Step 1 The volume composition of the raw gas entering the fluidized bed reactor is CO 10-30%, methyl nitrite or ethyl nitrite 10-30%, N 2 40-80%, and the remaining components include NO or methanol, etc.; the raw gas is a configured mixed gas.

[0026] The top pressure of the fluidized bed reactor is 0.15 - 0.55 Mpa, as both too high and too low are not conducive to the reaction. The top temperature is 120 - 150 °C. If the temperature is too low, the reaction rate is low, and if it is too high, side reactions occur. Moreover, the fixed bed reactor operates adiabatically, causing the reaction temperature to continuously increase, which is beneficial to improving the conversion efficiency.

[0027] After gas-solid separation in step 3, the solid content in the clean reaction gas entering the fixed bed reactor is less than 5 mg / Nm 3 ; The fixed bed reactor operates adiabatically;

[0028] The conversion rate of methyl nitrite or ethyl nitrite in the fluidized bed reactor is 80 - 90%, the total conversion rate of the total nitrite in the two reactors is between 95 - 99%, and the selectivity for producing ethylene glycol dimethyl ether or ethylene glycol diethyl ether is between 90 - 98%, and the selectivity for the by-product dimethyl carbonate is between 5 - 8%.

[0029] The catalysts used in the above fluidized bed reactor and fixed bed reactor are the commonly used catalysts for the reaction of CO with nitrite to produce oxalate in the prior art, which are supported palladium catalysts, and the carrier is inert alfa-alumina.

[0030] Compared with the prior art, the present invention has the following advantages: The present invention connects the fluidized bed and the fixed bed in series, making use of the respective advantages of the fluidized bed and fixed bed reactions and overcoming their respective disadvantages. The heat release of this reaction is not high, belonging to a medium and small heat release system. The catalyst has good stability and the reaction rate is not very high. The present invention first uses the fluidized bed to achieve good heat removal and temperature control, which can increase the flow rate of the reaction material per unit volume, thereby improving the production capacity, that is, a high-capacity reaction device is proposed to obtain a medium conversion efficiency. Then, by connecting a fixed bed reactor in series, high production capacity of a single reactor system can be achieved, reducing the investment, energy consumption and total cost per unit output, and improving its competitiveness with the petrochemical route; It can produce a large amount of by-product carbonic acid diester, further improving the economic benefits of the device. Since the gas outlet of the fluidized bed reactor will entrain a large amount of catalyst dust, simply connecting the fixed bed in series will block the subsequent fixed bed reactor. Therefore, the present invention provides a filter between the two reactors, improving the service life of the device. Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the reaction device for the oxidative coupling of nitrite and CO to produce oxalate ester according to the present invention.

[0032] Identifications in the figure: fluidized bed reactor 100, catalyst a 101, gas distributor a 102, heat exchange tube 103, gas-solid separator 104, fixed bed reactor 200, catalyst b 201, gas distributor b 202, filter 300, steam drum 400;

[0033] Raw material pipeline 1, dust-containing gas pipeline 2, clean gas pipeline 3, catalyst particle return pipeline 4, total water inlet pipeline 6, steam product pipeline 7, water inlet pipeline 8, and water outlet pipeline 9. Specific embodiments

[0034] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0035] Example 1:

[0036] As Figure 1 shown, this embodiment corresponds to a production capacity of 100,000 tons of dimethyl oxalate. The reaction device for producing dimethyl oxalate by oxidative coupling of dimethyl nitrite and CO includes a fluidized bed reactor 100 and a fixed bed reactor 200, and the fluidized bed reactor 100 is located upstream of the fixed bed reactor 200, that is, a fixed bed reactor is connected in series behind the fluidized bed reactor. The diameter of the fluidized bed reactor is 1.8 meters and the height is 15 meters. The diameter of the fixed bed reactor is 1.3 meters and the height is 6 meters. At the same time, a filter 300 is also connected between the fluidized bed reactor 100 and the fixed bed reactor 200 through the dust-containing gas pipeline 2 and the clean gas pipeline 3 to achieve gas-solid separation. The material of this filter is a stainless steel metal particle sintered microporous tube, which can effectively filter and separate fine particle catalysts. The fluidized bed reactor 100 includes a bottom gas distribution area, an intermediate reaction area, and a top gas-solid separation area. Among them, a gas distributor a102 is provided in the gas distribution area, and catalyst a101 is filled in the intermediate reaction area. The filling amount of the catalyst is 5m 3 , and the particle size of the catalyst a101 is between 50 and 350 microns. Multiple parallel heat exchange tubes 103 are evenly arranged in the reaction area, and the catalyst a101 is filled between the heat exchange tubes 103. The gas distributor a102 is an orifice plate distributor, and the heat exchange tubes are stainless steel tubes with a total area of 100m 2 , the diameter of the heat exchange tube is 50 mm, the length is 6 meters, and there are 100 parallel heat exchange tubes in total. A gas-solid separator 104 is provided in the gas-solid separation area, and the gas-solid separator 104 is a cyclone separator. The heat exchange tube 103 forms a circulation loop with the steam drum 400 through the water inlet pipeline 8 and the water outlet pipeline 9, and can produce 2.8 tons / hr of steam.

[0037] The fixed bed reactor 200 is filled with catalyst b201 and gas distributor b202, and the catalyst b201 is a circular ring catalyst with a diameter of 6 mm, a ring wall thickness of 1.5 mm, and a ring height of 6 mm. The filling amount is 5m 3; The fixed-bed reactor 200 is an adiabatic reactor, and the catalyst b 201 is in the shape of a circular ring; The filter 300 is equipped with filter tubes, and the filter tubes are micro-porous sintered metal tubes. The filter has three interfaces, which are respectively connected to the top of the upstream fluidized-bed reactor 100 through the dust-containing gas pipeline 2, connected to the downstream fixed-bed reactor 200 through the clean gas pipeline 3, and then connected to the lower part of the fluidized-bed reactor 100 through the catalyst particle return pipeline 4. The recovered fine particle catalyst is returned to the fluidized-bed reaction.

[0038] The reaction process for the oxidative coupling of methyl nitrite and CO to produce dimethyl oxalate according to the above device includes the following steps:

[0039] (1) Primary reaction: The raw material gas enters the lower cavity of the fluidized-bed reactor 100 through the raw material pipeline 1, and is evenly distributed by the gas distributor a 102, enters the fluidized section containing the catalyst a 101, and contacts with the catalyst a 101 to carry out the catalytic coupling reaction of CO and methyl nitrite, generating dimethyl oxalate and co-producing NO. The volume composition of the raw material gas is CO = 15%, methyl nitrite = 10%, N 2 = 70%, and the remaining components include NO and methanol;

[0040] (2) Heat removal: The heat released by the coupling reaction increases the temperature of the reaction gas from 40°C to the temperature of the fluidized-bed reactor 100, 140°C on the one hand, and on the other hand, the excess reaction heat is removed through the heat exchange between the reaction gas and the heat exchange tube 103, and a water circulation is formed with the steam drum 400 through the inlet water pipeline 8 and the outlet water pipeline 9. Steam is produced in the steam drum 400, and the steam output is 2.8 tons / hr, which is discharged from the steam product pipeline 7. Fresh desalted and deoxygenated soft water is added to the steam drum through the total inlet water pipeline 6 to maintain the stable liquid level of the steam drum;

[0041] (3) Gas-solid separation: The reaction gas generated by the coupling reaction enters the upper space of the fluidized-bed reactor 100. Larger-sized catalyst particles entrained by the reaction gas are separated by gravitational sedimentation, smaller-sized catalyst particles are separated by a cyclone through the gas-solid separator 104, and fine-sized catalyst is transported to the filter 300 through the dust-containing gas pipeline 2 for thorough filtration. The filtered fine particle catalyst is returned to the fluidized section of the fluidized-bed reactor 100 through the catalyst return pipeline 4 for recycling, and the obtained clean reaction gas enters the downstream fixed-bed reactor 200 through the clean gas pipeline 3. The solid content in the clean reaction gas is 3mg / Nm 3 ;

[0042] (4) Secondary reaction: The product gas obtained from step (3) leaves the filter 300 and enters the fixed-bed reactor 200 through the clean gas pipeline 3 for a second reaction. The unreacted CO and dimethyl nitrite further react to achieve a high conversion efficiency.

[0043] In addition, the top pressure of the fluidized-bed reactor 100 is 0.35 Mpa, and the top temperature is 140 °C. The fixed-bed reactor 200 operates adiabatically. The conversion rate of methyl nitrite in the fluidized-bed reactor 100 is 82%. The total conversion rate of the total nitrite in the two reactors is about 96%, the selectivity for dimethyl oxalate is 93%, the selectivity for by-product dimethyl carbonate is 6%, and the remaining by-products are 1%.

[0044] Example 2:

[0045] As Figure 1 shown, this example corresponds to a production capacity of 300,000 tons of dimethyl oxalate. The reaction device for producing dimethyl oxalate by oxidative coupling of dimethyl nitrite and CO includes a fluidized-bed reactor 100 and a fixed-bed reactor 200. The fluidized-bed reactor 100 is located upstream of the fixed-bed reactor 200, that is, a fixed-bed reactor is connected in series behind the fluidized-bed reaction. The diameter of the fluidized-bed reactor is 3.15 meters and the height is 15 meters. The diameter of the fixed-bed reactor is 2.25 meters and the height is 6 meters. At the same time, a filter 300 is also connected between the fluidized-bed reactor 100 and the fixed-bed reactor 200 through the dust-containing gas pipeline 2 and the clean gas pipeline 3 to achieve gas-solid separation. The material of this filter is a sintered microporous tube of stainless steel metal particles, which can effectively filter and separate fine particle catalysts. The fluidized-bed reactor 100 includes a catalyst a101, with a catalyst loading of 15 m 3 , a gas distributor a102, heat exchange tubes 103 and a gas-solid separator 104. The particle size of the catalyst a101 is between 50 - 350 microns. The gas distributor a102 is an orifice plate distributor. The heat exchange tubes are made of stainless steel tubes, with a total area of 300 m 2 , the diameter of the heat exchange tubes is 50 mm, the length is 6 meters, and there are 300 heat exchange tubes in parallel. The fixed-bed reactor 200 is filled with a catalyst b201 and a gas distributor b202. The catalyst b201 is a circular ring catalyst with a diameter of 6 mm, a ring wall thickness of 1.5 mm, a ring height of 6 mm, and a loading of 15 m 3; It also includes a steam bag 400, which is connected to the heat exchange tube 103 in the fluidized bed reactor 100 through an inlet pipeline 8 and an outlet pipeline 9, and can produce 9.0 tons / hr of steam; the fixed bed reactor 200 is an adiabatic reactor, and the catalyst b201 is annular; the filter 300 is equipped with a filter tube, and the filter tube is a microporous metal sintered tube, and the filter has three interfaces, which are respectively connected to the top of the upstream fluidized bed reactor 100 through a dusty gas pipeline 2, connected to the downstream fixed bed reactor 200 through a clean gas pipeline 3, and then connected to the lower part of the fluidized bed reactor 100 through a catalyst particle reflux pipeline 4, and the recovered fine particle catalyst is refluxed to the fluidized bed reaction.

[0046] The reaction process for producing dimethyl oxalate by oxidative coupling of methyl nitrite and CO according to the above device comprises the following steps:

[0047] (1) Primary reaction: The raw gas enters the lower cavity of the fluidized bed reactor 100 through the raw material pipeline 1, and is evenly distributed through the gas distributor a102, and enters the fluidized section containing the catalyst a101, where it contacts the catalyst a101 to cause a catalytic coupling reaction of CO and methyl nitrite to generate dimethyl oxalate and co-produce NO. The volume composition of the raw gas is CO = 18%, methyl nitrite = 13%, N 2 =70%, the remaining components include NO and methanol;

[0048] (2) Heat removal: On the one hand, the heat released by the coupling reaction raises the temperature of the reaction gas from 40°C to the temperature of the reactor 100, 140°C. On the other hand, the excess reaction heat is removed through the heat exchange between the reaction gas and the heat exchange tube 103, and a water cycle is formed with the steam drum 400 through the inlet water pipeline 8 and the outlet water pipeline 9. Steam is produced in the steam drum 400, and the steam output is 9.0 tons / hr. The steam is discharged from the steam product pipeline 7, and fresh desalted and deoxygenated soft water is added to the steam drum through the main water inlet pipeline 6 to maintain the stable liquid level of the steam drum;

[0049] (3) Gas-solid separation: The reaction gas from step 2 enters the upper space of the reactor 100, and the larger catalyst particles entrained by the reaction gas are separated by gravity settling. The smaller catalyst particles are separated by cyclone in the gas-solid separator 104. The fine-particle catalyst is transported to the filter 300 through the dust-containing gas pipeline 2 for thorough filtration. The fine-particle catalyst obtained by filtration is returned to the fluidized section of the fluidized bed reactor 100 through the catalyst reflux pipeline 4 for recycling. The clean reaction gas obtained enters the downstream fixed bed reactor 200 through the clean gas pipeline 3. The solid content in the clean reaction gas is 2.5 mg / Nm 3 ;

[0050] (4) Second - stage reaction: The product gas obtained from step (3) leaves the filter 300 and enters the fixed - bed reactor 200 through the clean gas pipeline 3 for a second reaction to achieve a high conversion efficiency.

[0051] In addition, the top pressure of the fluidized - bed reactor 100 is 0.35 Mpa, and the top temperature is 140 °C. The fixed - bed reactor 200 operates adiabatically; the conversion rate of methyl nitrite in the fluidized - bed reactor 100 is 85%. The total conversion rate of the total nitrite in the two reactors is between 97%, the selectivity for dimethyl oxalate formation is 92%, the selectivity for by - product dimethyl carbonate is 7%, and the rest of the by - products are 1%.

[0052] Example 3

[0053] The particle size of the catalyst a is between 20 - 250 microns, and the particle size of the catalyst b is a sphere with a diameter of 2 mm.

[0054] The top pressure of the fluidized - bed reactor 100 is 0.55 Mpa, and the top temperature is 150 °C. The rest is the same as in Example 1.

[0055] The conversion rate of methyl nitrite in the fluidized - bed reactor 100 is 86%. The total conversion rate of the total nitrite in the two reactors is 99%, the selectivity for dimethyl oxalate formation is 95%, the selectivity for by - product dimethyl carbonate is 8%, and the rest of the by - products are 0.8%.

[0056] Example 4

[0057] The particle size of the catalyst a is between 850 - 1000 microns, and the particle size of the catalyst b is a cylinder with a diameter of 10 mm.

[0058] The top pressure of the fluidized - bed reactor 100 is 0.15 Mpa, and the top temperature is 120 °C. The rest is the same as in Example 1.

[0059] The conversion rate of methyl nitrite in the fluidized - bed reactor 100 is 84%. The total conversion rate of the total nitrite in the two reactors is between 96%, the selectivity for dimethyl oxalate formation is 90%, the selectivity for by - product dimethyl carbonate is 7%, and the rest of the by - products are 1%.

Claims

1. A reaction process for the oxidative coupling of nitrite and CO to produce oxalate ester, characterized in that, the device used includes a fluidized bed reactor (100), a fixed bed reactor (200), a filter (300) and a steam drum (400) connected in series, and the fluidized bed reactor (100) is located upstream of the fixed bed reactor (200); the fluidized bed reactor (100) includes a bottom gas distribution area, an intermediate reaction area, and a top gas-solid separation area. A gas distributor a (102) is provided in the gas distribution area, a catalyst a (101) and heat exchange tubes (103) are filled in the intermediate reaction area, and a gas-solid separator (104) is provided in the gas-solid separation area; The reaction process for the oxidative coupling of nitrite and CO to produce oxalate ester using the above device is as follows: (1) Primary reaction: The raw material gas enters the lower cavity of the fluidized bed reactor (100) through the raw material pipeline (1), and after being evenly distributed by the gas distributor a (102), it enters the fluidized section containing the catalyst a (101), and contacts the catalyst a (101) to undergo a catalytic coupling reaction of CO and methyl nitrite or ethyl nitrite to generate dimethyl oxalate or diethyl oxalate and by-product NO; (2) Heat removal: The heat released by the coupling reaction in the fluidized bed reactor (100) is removed through the heat exchange tubes and transported to the steam drum (400), and steam is produced in the steam drum (400); (3) Gas-solid separation: The reaction gas obtained from the coupling reaction in the fluidized bed reactor (100) enters the upper gas-solid separation area for gas-solid separation, and then is transported to the filter (300) through the dust-containing gas pipeline (2) for thorough filtration. The fine particle catalyst obtained by filtration returns to the fluidized section of the fluidized bed reactor (100) through the catalyst particle return pipeline (4) for recycling, and the obtained clean reaction gas enters the downstream fixed bed reactor (200) through the clean gas pipeline (3); (4) Secondary reaction: The clean reaction gas undergoes a second reaction in the fixed bed reactor (200) to achieve a high conversion efficiency.

2. The reaction process for the oxidative coupling of nitrite and CO to produce oxalate ester according to claim 1, characterized in that, the heat exchange tubes (103) form a circulation loop with the steam drum (400) through the water inlet pipeline (8) and the water outlet pipeline (9); Multiple parallel heat exchange tubes (103) are evenly arranged in the reaction area, and the catalyst a (101) is filled between the heat exchange tubes.

3. The reaction process for the oxidative coupling of nitrite and CO to produce oxalate ester according to claim 1, characterized in that, the particle size of the catalyst a (101) is between 20 and 1000 microns.

4. The reaction process for the oxidative coupling of nitrite and CO to produce oxalate ester according to claim 3, characterized in that, the particle size of the catalyst a (101) is between 50 and 500 microns.

5. The reaction process for the oxidative coupling of nitrite and CO to produce oxalate ester according to claim 1, characterized in that, The fixed-bed reactor (200) is filled with catalyst b (201) and gas distributor b (202), and the particle size of the catalyst b (201) is between 2 and 10 millimeters.

6. The reaction process for the oxidative coupling of nitrite and CO to produce oxalate ester according to claim 5, characterized in that, the particle size of the catalyst b (201) is between 4 and 8 millimeters.

7. The reaction process for the oxidative coupling of nitrite and CO to produce oxalate ester according to claim 5, characterized in that, the fixed-bed reactor (200) is an adiabatic reactor, and the catalyst b (201) is spherical, cylindrical, annular or porous cylindrical.

8. The reaction process for the oxidative coupling of nitrite and CO to produce oxalate ester according to claim 7, characterized in that, the catalyst b (201) is annular.

9. The reaction process for the oxidative coupling of nitrite and CO to produce oxalate ester according to claim 1, characterized in that, the filter (300) is filled with filter tubes, which are micro-porous metal sintered tubes, ceramic tubes, glass fiber cloth bags or organic polymer fiber cloth bags, and are provided with three interfaces, which are respectively connected to the top of the upstream fluidized-bed reactor (100) through the dust-containing gas pipeline (2), connected to the downstream fixed-bed reactor (200) through the clean gas pipeline (3), and then connected to the lower part of the fluidized-bed reactor (100) through the catalyst particle return pipeline (4).

10. The reaction process for the oxidative coupling of nitrite and CO to produce oxalate ester according to claim 1, characterized in that, Step (1): The volume composition of the raw material gas entering the fluidized bed reactor (100) is 10-30% CO, 10-30% methyl nitrite or ethyl nitrite, N 2 40-80%, and the remaining components include NO or methanol; the top pressure of the fluidized-bed reactor (100) is 0.15 - 0.55 Mpa, and the top temperature is 120 - 150 °C; The solid content in the clean reaction gas entering the fixed-bed reactor (200) after gas-solid separation in step (3) is less than 5 mg / Nm 3 ; The fixed-bed reactor (200) operates adiabatically; the conversion rate of methyl nitrite or ethyl nitrite in the fluidized-bed reactor (100) is 80 - 90%, the total conversion rate of the total nitrite esters in the two reactors is between 95 - 99%, and the selectivity for producing dimethyl oxalate or diethyl oxalate is between 90 - 98%, and the selectivity for the by-product dimethyl carbonate is between 5 - 8%.

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