Reactor, reaction system and method for directly synthesizing dimethyl carbonate from methanol and carbon dioxide

Abstract

The invention discloses a reactor for directly synthesizing dimethyl carbonate from methanol and carbon dioxide, comprising an inner tube and an outer tube, wherein the two ends of the outer tube are respectively connected with an upper flange and a lower flange, and the inner tube penetrates from the upper flange and penetrates from the lower flange; an inner metal electrode and an outer metal electrode are respectively fixedly wound at the same positions outside the inner tube wall and the outer tube wall; the metal ferrule is connected to the ground electrode through an electric wire; a screw hole is also provided on the outer tube wall; the lower end of the inner metal electrode is connected with a screw penetrated from the screw hole through a metal wire, and the screw is connected with a high-voltage electrode, and the high-voltage electrode is controlled by a controller; a catalyst bed is provided in the annular gap between the inner tube and the outer tube and between the inner metal electrode and the outer metal electrode. At the same time, the invention also discloses a reaction system and a reaction method for directly synthesizing dimethyl carbonate from methanol and carbon dioxide, which are combined with a plasma system and a membrane system, and the reaction conditions are mild and the yield of the product is high.

Description

Technical Field

[0001] The invention belongs to the technical field of dimethyl carbonate synthesis, and particularly relates to a reactor, a reaction system and a method for directly synthesizing dimethyl carbonate from methanol and carbon dioxide. Background Art

[0002] Dimethyl carbonate (DMC) is one of the world's recognized green chemicals. Its molecule (CH3O—CO—OCH3) contains methyl, methoxy, carbonyl and other functional groups. It is an important intermediate synthesis body and can be used as a methylating agent, methoxylating agent and carbonylating agent to replace highly toxic phosgene, dimethyl sulfate and methyl chloride. Therefore, it is also known as the "new building block" in the field of organic green chemical synthesis. Due to its low toxicity and low viscosity, DMC is also used to replace organic volatile substances as a green solvent. It has a wide range of applications in electronic chemicals, medicines, pesticides, dyes, synthetic materials, oil additives, food additives, automotive fuels and other fields.

[0003] The direct synthesis of DMC from CO2 and methanol is not only a green synthesis route for DMC, but also effectively reduces CO2 emissions. Especially when high-concentration CO2 in crude synthesis gas is used as raw material, it can greatly reduce the burden of energy conservation and emission reduction, and truly realize the capture, storage and utilization of CO2. At the same time, it can also effectively utilize the downstream product methanol with excess production capacity, increase the economic benefits of coal chemical industry, increase the industrial chain, and accelerate the industrial transformation and upgrading of related enterprises. At present, the main synthesis methods for industrial production of DMC are phosgene method, methanol oxidation carbonylation method and ester exchange method; the synthesis methods in the pilot process include urea alcoholysis method and one-step synthesis method of alkylene oxide, methanol and CO2; the synthesis methods in laboratory research include dimethyl ether oxidation carbonylation method, methanol electrochemical carbonylation method, methanol and CO2 direct synthesis method, etc. The main production method of DMC industry in China is that CO2 first reacts with alkylene oxide to form propylene carbonate, and then reacts with methanol through ester exchange reaction to form DMC, and the by-product is diol. Alkylene oxide is mostly made of petroleum cracking products, so the DMC produced by this route is greatly affected by crude oil price fluctuations.

[0004] The direct synthesis of DMC from CO2 and methanol can utilize greenhouse gas CO2 and methanol, a primary downstream product of coal chemical industry, natural gas chemical industry and biochemical industry, so this route has broad development prospects. However, this reaction is difficult to carry out. r G at 0-800 o C range is positive, only when the temperature is 80 o C, when pressure ≥ 2.41×104MPa, Δ rG<0. The difficulty in activating CO2 is also the main reason why the reaction is difficult to proceed. In order to improve the yield of DMC, it is necessary to study the kinetics and breaking the thermodynamic equilibrium. Therefore, the focus of this route research is on the application of catalysts, dehydrating agents or coupling agents and the research of reaction devices. Summary of the invention

[0005] In view of the defects of the prior art, the present invention provides a reactor, a reaction system and a method for directly synthesizing DMC from CH3OH and CO2, which combines a plasma system with a membrane reaction, can efficiently activate CO2 and accelerate the reaction rate.

[0006] A reactor for directly synthesizing dimethyl carbonate from methanol and carbon dioxide comprises an inner tube and an outer tube, the two ends of the outer tube are respectively connected with an upper flange and a lower flange, the inner tube passes through the upper flange and passes through the lower flange, and the upper flange, the lower flange, the inner tube and the outer tube are sealed and connected;

[0007] The upper flange and the lower flange are respectively provided with an air inlet and an air outlet; the inner tube wall and the outer tube wall are respectively fixedly wound with an inner metal electrode and an outer metal electrode at the same position outside; the upper end of the outer metal electrode is fixed by a metal ferrule; the metal ferrule is connected to the ground electrode by an electric wire; the outer tube wall is also provided with a screw hole;

[0008] The lower end of the inner metal electrode is connected to a screw inserted into the screw hole through a metal wire, and the screw is connected to a high-voltage electrode, and the high-voltage electrode is controlled by a controller; the screw hole is sealed by a gasket;

[0009] A catalyst bed is provided in the annular gap between the inner tube and the outer tube and between the inner metal electrode and the outer metal electrode;

[0010] A heating furnace is arranged outside the outer metal electrode.

[0011] Preferably, the catalyst bed layers are, from bottom to top, a quartz wool layer, a first acid-washed quartz sand layer, a catalyst and acid-washed quartz sand mixture layer, and a second acid-washed quartz sand layer.

[0012] Preferably, the inner metal electrode and the outer metal electrode are both metal meshes.

[0013] Preferably, the metal screen is a 304 stainless steel screen or a 316 stainless steel screen with a mesh size of 150 or more.

[0014] The metal wire is 304 stainless steel wire or 316 stainless steel wire.

[0015] Preferably, the outer tube is a corundum tube; and the inner tube is a polyimide tube.

[0016] Preferably, the quartz wool in the quartz wool layer has a particle size of 1-3 μm; the quartz sand in the first acid-washed quartz sand layer and the second acid-washed quartz sand layer are both sieved through a 40-60 mesh sieve; the catalyst and quartz sand in the catalyst and acid-washed quartz sand mixture layer are both sieved through a 40-60 mesh sieve.

[0017] A reaction system for directly synthesizing dimethyl carbonate from methanol and carbon dioxide comprises a methanol tank, a carbon dioxide tank, and a reactor, wherein the reactor is the above reactor; the reaction system further comprises a nitrogen tank and a reducing gas tank; the reducing gas tank is a 10% H2-Ar tank;

[0018] The nitrogen tank is connected to the top end of the inner tube of the reactor through a first mass flow meter;

[0019] The carbon dioxide tank is connected to the inlet of the preheater through a second mass flow meter;

[0020] The pipeline between the nitrogen tank and the first mass flow meter, and the pipeline between the carbon dioxide pipe and the second mass flow meter are connected through an intermediate pipeline; the first bypass valve and the second bypass valve are sequentially arranged on the intermediate pipeline;

[0021] The reducing gas tank is connected to the intermediate pipeline between the first bypass valve and the second bypass valve;

[0022] The methanol tank is connected to the inlet of the preheater via a micro-metering pump;

[0023] The outlet of the preheater is connected to the air inlet of the upper flange in the reactor, and the lower end of the inner tube of the reactor and the air outlet of the lower flange are both connected to a chromatographic analyzer.

[0024] The method for synthesizing dimethyl carbonate using the above reaction system comprises the following steps:

[0025] (1) Reducing the catalyst;

[0026] (2) Turn on the preheater and set the temperature to 120°C;

[0027] (3) Open the nitrogen tank, control the nitrogen flow rate through the first mass flow meter, introduce N2 into the inner tube, then open the first bypass valve and the second bypass valve, control the inside of the reactor to purge for 10 minutes through the second mass flow meter, and then close the first bypass valve and the second bypass valve;

[0028] (4) The high voltage electrode is adjusted by the controller to control the voltage to 70-110V and the current to 1.0-2.0A, and the reaction temperature is controlled by the heating furnace to 20-150 oC, reaction pressure 0.1-0.5MPa; the molar ratio of carbon dioxide and methanol is controlled to be 1:2 by the second mass flow meter and the micro-metering pump, and the reaction space velocity after the carbon dioxide and methanol are mixed is 500-2000 h -1 ; Carbon dioxide and methanol first pass through the preheater, then enter the annular gap between the inner tube and the outer tube, pass through the catalyst bed, react, and the reaction products flow out from the outlet of the lower flange;

[0029] The catalyst is reduced outside the reactor or in situ in the reactor.

[0030] The catalyst of the present invention is a catalyst used in the prior art for synthesizing dimethyl carbonate from carbon dioxide and methanol, and can be prepared by using the prior art.

[0031] Preferably, the catalyst is a metal-supported catalyst, comprising a carrier and a transition metal supported on the carrier, wherein the transition metal is at least one of Cu, Fe, Ni, Co, and Zn; the carrier is at least one of CeO2, ZrO2, MgO, and Al2O3; and the loading amount of the transition metal is 0-30wt% calculated as its corresponding oxide.

[0032] Preferably, the reduction operation outside the reactor is: in a 10% H2 / Ar atmosphere, according to 2 o C / min increased to 550 o C for 3 h for reduction, and after cooling to room temperature under the protection of an inert atmosphere, the reduced catalyst is loaded into the catalyst bed in the reactor.

[0033] Preferably, the operation of performing in-situ reduction in the reactor is as follows: firstly loading the catalyst into the catalyst bed in the reactor, starting the reactor, opening the second bypass valve, using 10% H2-Ar to purge for 10 min, while introducing N2 into the inner tube, setting the reduction temperature to 150 o C, voltage 120V, current 2.5A, reduction 1h; stop introducing 10% H2-Ar, open the first bypass valve to introduce N2 protection; close the first bypass valve and the second bypass valve.

[0034] More preferably, the reducing of the catalyst is performed in situ in the reactor.

[0035] Advantages of the present invention:

[0036] (1) The present invention forms a plasma system by designing electrodes in the reactor and connecting them with the ground electrode and the high-voltage electrode. The inner tube adopts a polyimide tube to form a membrane system. By combining the plasma system and the membrane system, the reaction conditions are mild and the yield of the product is high.

[0037] (2) Use dielectric barrier discharge to excite electrons, efficiently activate CO2, and accelerate the reaction rate;

[0038] (3) The experimental device of the present invention uses an inexpensive metal-supported catalyst, the catalyst can be recycled and regenerated, and the reaction can be carried out continuously. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The reactor of the present invention;

[0040] Figure 2 The reaction system of the present invention;

[0041] Among them, 1-upper flange, 3-outer tube, 4-metal ferrule, 5-heating furnace, 6-screw, 7-lower flange, 8-inner tube, 101-second pickled quartz sand layer, 9-catalyst and pickled quartz sand mixture layer, 10-first pickled quartz sand layer, 11-quartz wool layer, 12-high voltage electrode, 13-ground electrode, 14-nitrogen tank, 15-reducing gas tank, 16-carbon dioxide tank, 17-methanol tank, 18-micro metering pump, 19-preheater, 20-first mass flowmeter, 21-second mass flowmeter, 23-first bypass valve, 24-second bypass valve. DETAILED DESCRIPTION

[0042] Example 1

[0043] A reactor for directly synthesizing dimethyl carbonate from methanol and carbon dioxide comprises an inner tube 8 and an outer tube 3, wherein the two ends of the outer tube 3 are respectively connected with an upper flange 1 and a lower flange 7, wherein the inner tube 8 passes through the upper flange 1 and passes through the lower flange 7, and the upper flange 1, the lower flange 7, the inner tube 8 and the outer tube 3 are sealedly connected;

[0044] The upper flange 1 and the lower flange 7 are respectively provided with an air inlet and an air outlet;

[0045] An inner metal electrode and an outer metal electrode are fixedly wound on the same positions outside the inner tube wall and the outer tube wall respectively; the upper end of the outer metal electrode is fixed by a metal ferrule 4; the metal ferrule 4 is connected to the ground electrode 13 through an electric wire; a screw hole is also provided on the outer tube wall;

[0046] The lower end of the inner metal electrode is connected to a screw 6 inserted into the screw hole through a metal wire, and the screw 6 is connected to a high-voltage electrode 12, and the high-voltage electrode 12 is controlled by a controller; the screw hole is sealed by a gasket;

[0047] A catalyst bed is provided in the annular gap between the inner tube 8 and the outer tube 3 and between the inner metal electrode and the outer metal electrode;

[0048] A heating furnace 5 is arranged outside the outer metal electrode.

[0049] Example 2

[0050] On the basis of Example 1, the catalyst bed layers are, from bottom to top, a quartz wool layer 11 , a first acid-washed quartz sand layer 10 , a catalyst and acid-washed quartz sand mixture layer 9 , and a second acid-washed quartz sand layer 101 .

[0051] The inner metal electrode and the outer metal electrode are both metal meshes.

[0052] Example 3

[0053] The metal screen is a 304 stainless steel screen or a 316 stainless steel screen with a mesh size of 150 or more.

[0054] The metal wire is 304 stainless steel wire or 316 stainless steel wire.

[0055] The outer tube 3 is a corundum tube; the inner tube 8 is a polyimide tube.

[0056] The quartz wool in the quartz wool layer 11 has a particle size of 1-3 μm; the quartz sand in the first acid-washed quartz sand layer 10 and the second acid-washed quartz sand layer 101 are both sieved through a 40-60 mesh sieve; the catalyst and quartz sand in the catalyst and acid-washed quartz sand mixture layer 9 are both sieved through a 40-60 mesh sieve.

[0057] Example 4

[0058] A reaction system for directly synthesizing dimethyl carbonate from methanol and carbon dioxide comprises a methanol tank 17, a carbon dioxide tank 16, and a reactor, wherein the reactor is the reactor described in Example 3; the reaction system further comprises a nitrogen tank 14 and a reducing gas tank 15; the reducing gas tank 15 is a 10% H2-Ar tank;

[0059] The nitrogen tank 14 is connected to the top of the inner tube of the reactor through a first mass flow meter 20;

[0060] The carbon dioxide tank 16 is connected to the inlet of the preheater 19 through a second mass flow meter 21;

[0061] The pipeline between the nitrogen tank 14 and the first mass flow meter 20, and the pipeline between the carbon dioxide pipe and the second mass flow meter 21 are connected through an intermediate pipeline; the first bypass valve 23 and the second bypass valve 24 are sequentially arranged on the intermediate pipeline;

[0062] The reducing gas tank 15 is connected to the intermediate pipeline between the first bypass valve 23 and the second bypass valve 24;

[0063] The methanol tank 17 is connected to the inlet of the preheater 19 via a micro-metering pump 18;

[0064] The outlet of the preheater 19 is connected to the air inlet of the upper flange in the reactor, and the lower end of the inner tube of the reactor and the air outlet of the lower flange are both connected to a chromatographic analyzer.

[0065] Example 5

[0066] The method for synthesizing dimethyl carbonate using the reaction system described in Example 4 comprises the following steps:

[0067] (1) Reducing the catalyst;

[0068] (2) Turn on the preheater 19 and set the temperature to 120°C;

[0069] (3) Open the nitrogen tank 14, control the nitrogen flow rate through the first mass flow meter 20, introduce N2 into the inner tube 8, then open the first bypass valve 23 and the second bypass valve 24, control the inside of the reactor to be purged for 10 minutes through the second mass flow meter 21, and then close the first bypass valve 23 and the second bypass valve 24;

[0070] (4) The high voltage electrode 12 is adjusted by the controller to control the voltage to 70-110V, the current to 1.0-2.0A, and the reaction temperature to 20-150 o C, reaction pressure 0.1-0.5MPa; the molar ratio of carbon dioxide and methanol is controlled by the second mass flow meter 21 and the micro-metering pump 18 to be 1:2, and the reaction space velocity of carbon dioxide and methanol after mixing is 500-2000 h -1 ; Carbon dioxide and methanol first pass through the preheater 19, then enter the annular gap between the inner tube 8 and the outer tube 3, pass through the catalyst bed, react, and the reaction products flow out from the outlet of the lower flange;

[0071] The catalyst is reduced outside the reactor or in situ in the reactor.

[0072] Example 6

[0073] Based on Example 5, the catalyst is a metal-loaded catalyst, including a carrier and a transition metal loaded on the carrier, the transition metal is at least one of Cu, Fe, Ni, Co, and Zn; the carrier is at least one of CeO2, ZrO2, MgO, and Al2O3; the loading amount of the transition metal is 0-30wt% calculated as its corresponding oxide.

[0074] Example 7

[0075] Based on Example 6, the catalyst used is Cu-Fe / CeZrO x ; The preparation method is as follows:

[0076] Weigh 29.40 g Ce(NO3)3·6H2O and 29.06 g Zr(NO3)4·5H2O and dissolve them in 100 mL deionized water. Slowly add ammonia water until the pH is 8. Stir at room temperature for 2 h, then transfer to a hydrothermal reactor and heat at 140 o C for 24 h, cool and take out, filter, wash with water, 110 o C for 12 h and dried at 2 o C / min increased to 550 o C, calcined for 6h to obtain Ce 0.5 Zr 0.5 O2 carrier; weigh 3.80g Cu(NO3)2·3H2O and 0.63g Fe(NO3)3·9H2O and dissolve them in 25mL 30% ammonia water, weigh 3.5g of the above Ce 0.5 Zr 0.5 O2 carrier, stirred at room temperature for 24 h, ultrasonically dispersed for 3 h, 70 o C rotary evaporation, 110 o C for 12 h and dried at 2 o C / min increased to 550 o C, calcined for 6h, pressed into 40-60 mesh tablets; the Cu and Fe loading rates were 25% and 5% (based on the mass of each oxide), and the carrier was Ce. 0.5 Zr 0.5 O2 supported catalyst.

[0077] Example 8

[0078] Method for synthesizing dimethyl carbonate:

[0079] (1) Reduction of the catalyst outside the reactor: 1.0 g of the catalyst described in Example 7 was used in a tube furnace under a 10% H2 / Ar atmosphere for 2 o C / min increased to 550 o C and reduced for 3h; under the protection of an inert atmosphere, after cooling to room temperature, mixed evenly with 2.0g of 40-60 mesh quartz sand to form a catalyst and acid-washed quartz sand mixture layer 9, which was then loaded into the reactor;

[0080] (2) Turn on the preheater 19 and set the temperature to 120°C;

[0081] (3) Open the nitrogen tank 14, control the nitrogen flow rate through the first mass flow meter 20, and introduce N2 into the inner tube 8 at a flow rate of 30 mL / min. Then open the first bypass valve 23 and the second bypass valve 24, and purge the inside of the reactor for 10 min through the second mass flow meter 21. Then close the first bypass valve 23 and the second bypass valve 24.

[0082] (4) The controller adjusts the high voltage electrode 12 to control the voltage to 0V, the current to 0A, and the reaction temperature to 100 o C, reaction pressure 0.5MPa; the molar ratio of carbon dioxide and methanol introduced is controlled by the second mass flow meter 21 and the micro-metering pump 18 to be 1:2, and the reaction space velocity of carbon dioxide and methanol after mixing is 500h -1 ; Carbon dioxide and methanol first pass through the preheater 19, then enter the annular gap between the inner tube 8 and the outer tube 3, pass through the catalyst bed, react, and the reaction product flows out from the outlet of the lower flange; the reaction results are detected online, and the results are shown in Table 1.

[0083] Example 9

[0084] N2 was introduced into the inner tube 8, and the flow rate of N2 was 30 mL / min. Other conditions were the same as those in Example 8. The reaction results were detected online. The results are shown in Table 1.

[0085] Example 10

[0086] Airspeed is 2000h -1 , the rest is the same as in Example 9; the reaction results are detected online, and the results are shown in Table 1.

[0087] Embodiment 11

[0088] The voltage was 100 V, the current was 2.0 A, and the rest was the same as in Example 9. The reaction results were detected online, and the results are shown in Table 1.

[0089] Example 12

[0090] The reaction temperature was 90° C., and the other parameters were the same as those in Example 11. The reaction results were detected online, and the results are shown in Table 1.

[0091] Embodiment 13

[0092] The voltage was 90 V, and the rest was the same as in Example 11. The reaction results were detected online, and the results are shown in Table 1.

[0093] Embodiment 14

[0094] The voltage is 100V and the air speed is 2000h -1 , the rest is the same as Example 11; the reaction results are detected online, and the results are shown in Table 1.

[0095] Embodiment 15

[0096] Method for synthesizing dimethyl carbonate:

[0097] (1) In-situ reduction of the catalyst in the reactor: 1.0 g of the catalyst described in Example 7 was mixed evenly with 2.0 g of quartz sand of 40-60 mesh to form a catalyst and acid-washed quartz sand mixture layer 9, which was then loaded into the reactor; the reactor was started, the second bypass valve 24 was opened, 10% H2-Ar was used for purging for 10 min, and N2 was introduced into the inner tube 8 at the same time, and the reduction temperature was set to 150°C. o C, voltage 120V, current 2.5A, reduction 1h; stop introducing 10% H2-Ar, open the first bypass valve 23 to introduce N2 protection; close the first bypass valve 23 and the second bypass valve 24;

[0098] (2) Turn on the preheater 19 and set the temperature to 120°C;

[0099] (3) Open the nitrogen tank 14, control the nitrogen flow rate through the first mass flow meter 20, introduce N2 into the inner tube 8, and adjust the N2 flow rate to 30 mL / min. Then open the first bypass valve 23 and the second bypass valve 24, and control the N2 purge inside the reactor for 10 min through the second mass flow meter 21. Then close the first bypass valve 23 and the second bypass valve 24.

[0100] (4) The controller adjusts the high voltage electrode 12 to control the voltage to 100 V, the current to 2.0 A, and the reaction temperature to 90 o C, reaction pressure 0.5MPa; the molar ratio of carbon dioxide and methanol is controlled by the second mass flow meter 21 and the micro-metering pump 18 to be 1:2, and the reaction space velocity of carbon dioxide and methanol after mixing is 500 h -1 ; Carbon dioxide and methanol first pass through the preheater 19, then enter the annular gap between the inner tube 8 and the outer tube 3, pass through the catalyst bed, react, and the reaction product flows out from the outlet of the lower flange; the reaction results are detected online, and the results are shown in Table 1.

[0101] Example 16

[0102] The reaction temperature is 100°C and the space velocity is 2000h -1 , the rest is the same as Example 15; the reaction results are detected online, and the results are shown in Table 1.

[0103] Embodiment 17

[0104] The voltage is 110V, the current is 1.0A, the reaction pressure is 0.3MPa, the reaction temperature is 120℃, and the space velocity is 2000h -1 , the rest is the same as Example 15; the reaction results are detected online, and the results are shown in Table 1.

[0105] Embodiment 18

[0106] The voltage is 70V, the current is 1.0A, the reaction pressure is 0.1MPa, the reaction temperature is 150℃, and the space velocity is 2000h -1 , the rest is the same as Example 15; the reaction results are detected online, and the results are shown in Table 1.

[0107] The implementation process of the reaction system of the present invention is as follows:

[0108] First, the catalyst is reduced; the preheater 19 is opened and the temperature is set to 120°C; the first bypass valve 23 and the second bypass valve 24 are opened, N2 is introduced to purge the reactor for 10 minutes, and N2 is introduced into the inner tube 8, and the flow rate of nitrogen is controlled by the first mass flow meter 20 and the second mass flow meter 21, and then the first bypass valve 23 and the second bypass valve 24 are closed; the high voltage electrode 12 is adjusted by the controller to control the voltage to 70-110V and the current to 1.0-2.0A, and the reaction temperature is controlled by the reactor to 20-150 o C, reaction pressure 0.1-0.5MPa; the molar ratio of carbon dioxide and methanol is controlled by the second mass flow meter 21 and the micro-metering pump 18 to be 1:2, and the reaction space velocity of carbon dioxide and methanol after mixing is 500-2000 h -1 The CO2 gas and methanol first pass through the preheater 19, and then enter the annular gap between the inner tube 8 and the outer tube 3, that is, enter the discharge area and catalytic reaction area of ​​the reactor, pass through the catalyst bed, react, and the reaction product flows out from the gas outlet of the lower flange and enters the chromatograph for online detection; the gas flowing out from the lower end of the inner tube also alternately enters the chromatograph for analysis.

[0109] The catalyst can be reduced by pre-reduction outside the reactor and then loaded into the reactor, or it can be directly reduced in situ in the reactor. It is more preferred to directly reduce in situ in the reactor. The operation of reducing outside the reactor is: in a 10% H2 / Ar atmosphere, according to 2 o C / min increased to 550 o C and then maintained for 3 hours for reduction. Under the protection of an inert atmosphere, the temperature is lowered to room temperature and the reduced catalyst is loaded into the catalyst bed in the reactor. The operation of the in-situ reduction in the reactor is as follows: the catalyst is first loaded into the catalyst bed in the reactor, the reactor is started, the second bypass valve 24 is opened, 10% H2-Ar is used for purging for 10 minutes, and N2 is introduced into the inner tube 8 at the same time. The reduction temperature is set to 150 o C, voltage 120V, current 2.5A, reduction 1h; stop introducing 10% H2-Ar, open the first bypass valve 23 to introduce N2 for protection; close the first bypass valve 23 and the second bypass valve 24.

[0110] The reaction principle of the present invention is as follows:

[0111] The CH3OH and CO2 gas flows enter the preheater 19. After the CH3OH is vaporized and mixed evenly with the CO2, it enters the annular gap between the inner tube 8 and the outer tube 3 in the reactor from top to bottom, enters the discharge area, and uses the dielectric barrier discharge method to excite electrons, is ionized and forms plasma, and then enters the catalytic reaction area to react to generate dimethyl carbonate and water. Because the inner tube 8 is a polyimide tube and a membrane system, the generated water diffuses into the inner tube 8 through the membrane (polyimide) and is carried out of the reaction system by the purge gas nitrogen. The flow rate of the purge gas is controlled by the first mass flowmeter 20.

[0112] Table 1 Reaction results

[0113] .

Claims

1. A reactor for directly synthesizing dimethyl carbonate from methanol and carbon dioxide, comprising an inner tube (8) and an outer tube (3), characterized in that: The two ends of the outer tube (3) are respectively connected to an upper flange (1) and a lower flange (7); the inner tube (8) passes through the upper flange (1) and passes through the lower flange (7); the upper flange (1), the lower flange (7), the inner tube (8) and the outer tube (3) are sealedly connected; The upper flange (1) and the lower flange (7) are respectively provided with an air inlet and an air outlet; An inner metal electrode and an outer metal electrode are fixedly wound on the same positions outside the inner tube wall and the outer tube wall respectively; the upper end of the outer metal electrode is fixed by a metal ferrule (4); the metal ferrule (4) is connected to the ground electrode (13) by an electric wire; and a screw hole is also provided on the outer tube wall; The lower end of the inner metal electrode is connected to a screw (6) inserted into the screw hole via a metal wire, the screw (6) is connected to a high-voltage electrode (12), and the high-voltage electrode (12) is controlled by a controller; the screw hole is sealed by a gasket; A catalyst bed is provided in the annular gap between the inner tube (8) and the outer tube (3) and between the inner metal electrode and the outer metal electrode; A heating furnace (5) is arranged on the outer side of the outer metal electrode; The catalyst bed layers are, from bottom to top, a quartz wool layer (11), a first acid-washed quartz sand layer (10), a catalyst and acid-washed quartz sand mixture layer (9), and a second acid-washed quartz sand layer (101); The outer tube (3) is a corundum tube; and the inner tube (8) is a polyimide tube.

2. The reactor for directly synthesizing dimethyl carbonate from methanol and carbon dioxide according to claim 1, characterized in that: The inner metal electrode and the outer metal electrode are both metal meshes.

3. The reactor for directly synthesizing dimethyl carbonate from methanol and carbon dioxide according to claim 2, characterized in that: The metal screen is a 304 stainless steel screen or a 316 stainless steel screen with a mesh size of 150 or more.

4. The reactor for directly synthesizing dimethyl carbonate from methanol and carbon dioxide according to claim 1, characterized in that: The quartz wool in the quartz wool layer (11) has a particle size of 1-3 μm; the quartz sand in the first acid-washed quartz sand layer (10) and the second acid-washed quartz sand are both sieved through a 40-60 mesh sieve; and the catalyst and quartz sand in the catalyst and acid-washed quartz sand mixture layer (9) are both sieved through a 40-60 mesh sieve.

5. A reaction system for directly synthesizing dimethyl carbonate from methanol and carbon dioxide, comprising a methanol tank (17), a carbon dioxide tank (16), and a reactor, characterized in that: The reactor is the reactor according to any one of claims 1 to 4; the reaction system further comprises a nitrogen tank (14) and a reducing gas tank (15); the reducing gas tank (15) is a 10% H2-Ar tank; The nitrogen tank (14) is connected to the top end of the inner tube (8) of the reactor via a first mass flow meter (20); The carbon dioxide tank (16) is connected to the inlet of the preheater (19) via a second mass flow meter (21); The pipeline between the nitrogen tank (14) and the first mass flow meter (20), and the pipeline between the carbon dioxide tube and the second mass flow meter (21) are connected via an intermediate pipeline; a first bypass valve (23) and a second bypass valve (24) are sequentially arranged on the intermediate pipeline; The reducing gas tank (15) is connected to the intermediate pipeline between the first bypass valve (23) and the second bypass valve (24); The methanol tank (17) is connected to the inlet of the preheater (19) via a micro-metering pump (18); The outlet of the preheater (19) is connected to the air inlet of the upper flange of the reactor, and the lower end of the inner tube (8) of the reactor and the air outlet of the lower flange are both connected to a chromatographic analyzer.

6. A method for synthesizing dimethyl carbonate using the reaction system of claim 5, characterized in that: The following steps are involved: (1) Reducing the catalyst; (2) Turn on the preheater (19) and set the temperature to 120°C; (3) opening the nitrogen tank (14), controlling the nitrogen flow rate through the first mass flow meter (20), introducing N2 into the inner tube (8), then opening the first bypass valve (23) and the second bypass valve (24), controlling the inside of the reactor to be purged for 10 minutes through the second mass flow meter (21), and then closing the first bypass valve (23) and the second bypass valve (24); (4) The high voltage electrode (12) is adjusted by the controller to control the voltage to 70-110V and the current to 1.0-2.0A, and the reaction temperature is controlled by the heating furnace (5) to 20-150 o C, reaction pressure 0.1-0.5 MPa; the molar ratio of carbon dioxide and methanol is controlled to be 1:2 by the second mass flow meter (21) and the micro-metering pump (18), and the reaction space velocity after the carbon dioxide and methanol are mixed is 500-2000 h -1 The carbon dioxide and methanol first pass through the preheater (19), then enter the annular gap between the inner tube (8) and the outer tube (3), pass through the catalyst bed, react, and the reaction products flow out from the outlet of the lower flange; The catalyst is reduced outside the reactor or in situ in the reactor.

7. The method according to claim 6, characterized in that: The reduction operation outside the reactor is as follows: in a 10% H2 / Ar atmosphere, according to 2 o C / min increased to 550 o C for 3 h for reduction, and after cooling to room temperature under the protection of an inert atmosphere, the reduced catalyst is loaded into the catalyst bed in the reactor.

8. The method according to claim 6, characterized in that: The operation of the in-situ reduction in the reactor is as follows: the catalyst is first loaded into the catalyst bed in the reactor, the reactor is started, the second bypass valve (24) is opened, 10% H2-Ar is used for purging for 10 minutes, and N2 is introduced into the inner tube (8) at the same time, and the reduction temperature is set to 150 o C, voltage 120V, current 2.5A, reduction for 1h; stop introducing 10% H2-Ar, open the first bypass valve (23) and introduce N2 for protection; close the first bypass valve (23) and the second bypass valve (24).

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