Apparatus and method for producing methanol by low-temperature plasma in cooperation with catalyst

Abstract

The application discloses a device and method for preparing methanol by using low-temperature plasma and catalysts. The device uses low-temperature plasma to generate discharge and activate H2 and CO2 in a plasma reactor, so that the thermal catalytic reaction rate is improved and the energy consumption is reduced. Condensed water is introduced outside the low-temperature plasma to improve the conversion rate and selectivity of the reaction. The gas treated by the low-temperature plasma is sent into a thermal catalytic reactor, the thermal catalytic reactor is provided with a partition plate, so that a reflux is formed at a local position in the thermal catalytic reactor, and a plurality of catalyst outer bed layers are arranged outside and inside the partition plate, so that different kinds of solid catalysts can be filled at different positions. The application can make the CO2 methanol reaction be carried out at normal pressure, reduce the energy consumption, activate the raw material gas by using a low-temperature plasma array, improve the thermal catalytic reaction rate, and reduce the energy consumption of the thermal catalysis. The multi-layer catalyst outer bed layer structure is used to control the reaction path and the product and improve the methanol yield.

Description

Technical Field

[0001] This invention relates to the field of methanol preparation technology, and in particular to an apparatus and method for producing methanol using a low-temperature plasma-assisted catalyst. Background Technology

[0002] Methanol, as a fundamental organic chemical raw material, is widely used in traditional chemical industries and has broad application prospects in emerging alternative energy fields. Converting CO2 to methanol via thermocatalysis, electrocatalysis, photocatalysis, and plasma catalysis, and then supplying it with renewable energy, is an important measure for hydrogen storage and energy conservation, and has received widespread attention and research. Among the many CO2 catalytic conversion methods, thermocatalysis, due to its simple process and mature technology, has been put into engineering use in many parts of the world. The reaction of CO2 to methanol via thermocatalysis is usually carried out under high pressure, but this results in a large amount of energy consumption. Currently, industrial CO2 hydrogenation to methanol typically uses copper-based catalysts, but these catalysts have low CO2 conversion rates at atmospheric pressure and are prone to reverse water-gas reaction (RWGS), leading to increased selectivity for the byproduct CO. In summary, improving the conversion rate and methanol selectivity of the CO2 to methanol reaction at atmospheric pressure is the key issue for this technology.

[0003] Currently, common strategies include modifying catalysts to improve CO2 conversion and methanol selectivity. Patent CN 110694631A discloses a catalyst for methanol synthesis, its preparation method, and its application. The catalyst comprises Cu, Zn, Zr, Al, Ce, and La, and is prepared using a co-precipitation-ultrasonic impregnation method. This effectively suppresses CO generation during CO2-to-methanol synthesis and improves methanol selectivity. Patent CN202210513534 discloses a method for CO2 hydrogenation to methanol, using a precipitation method to prepare a Cu / ZnO / Al2O3 precursor, followed by silanization modification to obtain a Cu / ZnO / Al2O3 / Si catalyst. This effectively reduces the selectivity of the byproduct CO and improves the catalyst's high-temperature stability and anti-sintering properties. However, most of these catalysts operate at pressures above 0.5 MPa. At atmospheric pressure, CO2 conversion and methanol selectivity decrease significantly, the amount of byproduct CO generation increases, and the energy consumption for pressurization is high. To reduce energy consumption and increase yield, patent CN115259997A discloses a self-heating carbon dioxide hydrogenation process for methanol synthesis. The reacted gas is fed into waste heat boiler byproduct steam, then into a feed gas preheater to preheat the mixed feed gas. A first turbulence mechanism is incorporated within the reactor, thereby improving the thermal efficiency and reaction conversion rate. However, the catalyst bed temperature gradually decreases from top to bottom, which can easily lead to low conversion rates in the upper catalyst layer and slow reaction rates in the lower catalyst layer. Summary of the Invention

[0004] The technical problem to be solved by this invention is to improve the CO2 conversion rate and methanol selectivity in the CO2-to-methanol reaction, suppress the generation of byproduct CO, and reduce the energy consumption of the reaction, in order to overcome the shortcomings of the existing technology.

[0005] To solve the technical problem, the solution of the present invention is: to propose an apparatus for producing methanol by low-temperature plasma synergistic catalyst, the apparatus comprising a low-temperature plasma reactor, a first circulating water pump, a thermal catalytic reactor, a partition, an outer catalyst bed, and an inner catalyst bed;

[0006] The low-temperature plasma reactor is used to activate hydrogen and CO2, and the activated gas is then introduced into the thermal catalytic reactor.

[0007] The outer side of the low-temperature plasma reactor contains condensate, which is supplied by a first circulating water pump;

[0008] The thermocatalytic reactor contains a cylindrical baffle. The gas inlet is inside the baffle, and the gas outlet is outside the baffle. The gas enters the space inside the baffle from the bottom of the thermocatalytic reactor, and after reaching the top of the thermocatalytic reactor, it flows out from the bottom gas outlet outside the baffle. The gas forms a backflow at a local position outside the baffle.

[0009] Several outer catalyst beds are fixed on the outside of the partition of the thermocatalytic reactor, and several inner catalyst beds are fixed on the inside. Each outer and inner catalyst bed is filled with the same or different types of catalyst to control the reaction path and products of each section of the outer catalyst bed. After the catalyst on the outer catalyst bed is reduced by non-thermodynamically balanced hydrogen active particles, non-thermodynamically balanced carbon and oxygen active particles are introduced to produce methanol.

[0010] Furthermore, a low-temperature plasma electrode is installed inside the low-temperature plasma reactor, and circulating condensate is provided on the outer layer of the low-temperature plasma reactor.

[0011] Furthermore, the gas inlet and outlet pipes of the thermocatalytic reactor are wrapped with heating tape.

[0012] On the other hand, the present invention also provides a method for producing methanol using a low-temperature plasma-co-catalyst, comprising the following steps:

[0013] Step (1): Measure the saturated water absorption of the carrier; place the carrier in a glass dish and add deionized water drop by drop until it just completely covers the sample. After standing, remove the water from the sample surface. The mass difference before and after adding water is the saturated water absorption of the carrier.

[0014] Step (2): Weigh out the corresponding mass of deionized water according to the carrier mass and saturated water absorption capacity, and dissolve the active component and auxiliary agent solid in the deionized water according to the ratio of deionized water mass: carrier mass = carrier saturated water absorption capacity to obtain the metal precursor solution.

[0015] Step (3): The above metal precursor solution is added dropwise to the carrier so that the solution just impregnates all the carrier. After impregnation, the carrier is allowed to stand, dried, and calcined to obtain the catalyst, which is then ground into particles.

[0016] Step (4): According to actual needs, repeat steps (1) to (3) several times to obtain several kinds of catalysts, which are then filled into different catalyst outer beds in the thermocatalytic reactor; the different catalyst outer beds are separated by partitions.

[0017] Step (5): Hydrogen gas is introduced into the low-temperature plasma reactor to generate hydrogen active particles, which are then introduced into the thermocatalytic reactor to reduce the catalyst; the gas enters the space inside the partition from the bottom of the thermocatalytic reactor, and flows out from the bottom gas outlet outside the partition after reaching the top of the thermocatalytic reactor; the gas forms a backflow at a local position outside the partition.

[0018] Step (6): CO2 is introduced into a low-temperature plasma reactor to generate carbon and oxygen active particles, which are then introduced into a thermocatalytic reactor to produce methanol.

[0019] Furthermore, the active component is copper nitrate, nickel nitrate, or cobalt nitrate.

[0020] Furthermore, the additives are zinc nitrate hexahydrate, gallium nitrate, or zirconium oxynitrate.

[0021] Furthermore, the carrier is mesoporous alumina or mesoporous silica.

[0022] Furthermore, the catalysts obtained include: Cu / Zn / Al2O3 catalyst, Ni / Ga / SiO2 catalyst and Co / Ga / SiO2 catalyst.

[0023] The beneficial effects of this invention are:

[0024] (1) Reduced reaction energy consumption. By utilizing the non-equilibrium characteristics of plasma, carbon-oxygen double bonds and HH covalent bonds can be broken under normal pressure, resulting in a lower reaction temperature and reducing the additional energy consumption caused by pressurization and heating;

[0025] (2) Improved reaction rate, conversion rate, and selectivity. A breakdown arc is formed using a low-temperature plasma array, creating an excited-state carbon, hydrogen, and oxygen active particle region, lowering the energy barrier for subsequent thermocatalytic reactions and increasing the reaction rate. Circulating condensate water is introduced outside the plasma reactor to promote a forward shift in the methanol production equilibrium, improving the reaction conversion rate and selectivity. A reflux high-pressure region is formed in a localized area within the thermocatalytic reactor, thereby increasing the reaction rate and promoting a forward shift in the reaction equilibrium.

[0026] (3) The generation of by-products was suppressed and the methanol yield was increased. By using specific types of catalysts, the methanol selectivity of CO2 hydrogenation reaction was improved, the generation of by-products such as CO was suppressed, or CO was hydrogenated into methanol. Through the multi-layer catalyst outer bed structure, different types of particulate solid catalysts can be filled at different positions to control the reaction path and products of each bed section, thereby controlling the methanol yield. Attached Figure Description

[0027] The invention will be further described below with reference to the accompanying drawings.

[0028] Figure 1 This is a schematic diagram of a device for producing methanol using a low-temperature plasma-catalyst co-catalyst.

[0029] In the diagram, 1. CO2 cylinder, 2. Hydrogen generator, 3. CO2 mass flow meter, 4. H2 mass flow meter, 5. Low-temperature plasma reactor, 6. Plasma power supply, 7. Oscilloscope, 8. First circulating water pump, 9. First heating zone, 10. Thermocatalytic reactor, 11. Thermocouple, 12. Baffle, 13. Outer catalyst bed, 14. Inner catalyst bed, 15. Second heating zone, 16. Liquid phase collection device, 17. Second circulating water pump, 18. Ball valve, 19. Waste gas cylinder.

[0030] Figure 2 This is a top view of the thermocatalytic reactor and the outer bed of the catalyst.

[0031] In the figure, 10 is the thermocatalytic reactor, 12 is the baffle, 13 is the outer catalyst bed, 14 is the inner catalyst bed, 20 is the filling hole, 21 is the gas inlet, and 22 is the gas outlet. Detailed Implementation

[0032] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0033] like Figure 1As shown, the present invention provides an apparatus for producing methanol using a low-temperature plasma co-catalyst, comprising a CO2 cylinder 1, a hydrogen generator 2, a CO2 mass flow meter 3, an H2 mass flow meter 4, a low-temperature plasma reactor 5, a plasma power supply 6, an oscilloscope 7, a first circulating water pump 8, a first heating belt 9, a thermal catalytic reactor 10, a thermocouple 11, a partition 12, an outer catalyst bed 13, an inner catalyst bed 14, a second heating belt 15, a liquid phase collection device 16, a second circulating water pump 17, a ball valve 18, and a waste gas cylinder 19.

[0034] A CO2 cylinder and a hydrogen generator are used as raw materials for gas supply. The flow rate and ratio of the two gases are controlled by a CO2 mass flow meter and an H2 mass flow meter. The gas exiting the mass flow meter enters the low-temperature plasma reactor. CO2 cylinder 1 has a capacity of 50 L and an operating pressure of 15 MPa. The pressure of the outlet pressure reducing valve is controlled at 0.3~0.5 MPa. The outlet flow rate of hydrogen generator 2 is 0~300 mL / min and the operating pressure is 0.3 MPa. The flow control range of CO2 mass flow meter 3 and H2 mass flow meter 4 is 0~50 mL / min.

[0035] Specifically, a low-temperature plasma reactor is employed to obtain excited-state hydrocarbon active particles and lower the energy barrier for subsequent reactions. A plasma power supply powers the low-temperature plasma, creating an arc breakdown region between the low-temperature plasma electrodes and the reactor wall, generating non-thermodynamically equilibrium hydrocarbon active particles, thus increasing the thermocatalytic reaction rate and reducing energy consumption. The plasma power supply is connected to an oscilloscope to measure discharge voltage, current, frequency, and power. Cooling water is circulated around the outer ring of the plasma reactor to absorb the heat released by the reaction. This cooling water is supplied by a circulating water pump to improve the conversion rate and selectivity of the reaction. The low-temperature plasma reactor 5 consists of two layers: an inner layer is a glass column with a diameter of 20–30 mm and a height of 80–120 mm, equipped with a gas inlet and outlet for gaseous reactions; the outer layer is a glass column with a diameter of 40–60 mm and a height of 80–120 mm, equipped with a cooling water inlet and outlet for cooling the inner layer. Cooling water is supplied by a first circulating water pump 8, whose temperature control range is -5 to 99.9 °C. The inner layer is equipped with discharge electrodes with a diameter of 10-25 mm and a length of 70-110 mm. These discharge electrodes are connected to a plasma power supply 6, which has an output voltage of 0-1 kV and a current of 0-100 A. The output frequency and power of the plasma power supply 6 are measured using an oscilloscope 7. The gas outlet of the inner layer of the low-temperature plasma reactor 5 is connected to the thermocatalytic reactor 10 via a pipe wrapped with a first heating belt 9. The heating temperature of the first heating belt 9 is set to 70-90 °C to increase the gas temperature within the pipe and prevent methanol condensation. The thermocatalytic reactor 10 is a glass tube with an outer diameter of 11-15 mm, a wall thickness of 1 mm, and a length of 300-600 mm. It is heated by a tube furnace at a temperature of 20-800 °C. A type K thermocouple 11 with an accuracy of ±0.1 °C is installed at the top of the reactor.

[0036] Specifically, to improve the reaction rate and equilibrium conversion rate of CO2 to methanol, a baffle structure is used inside the thermocatalytic reactor 10. The outlet gas from the low-temperature plasma reactor enters the thermocatalytic reactor through a pipeline wrapped with heating tape to prevent methanol condensation within the pipeline. The thermocatalytic reactor is equipped with a baffle; gas enters the space within the baffle from the bottom of the reactor and exits from the bottom gas outlet outside the baffle after reaching the top of the reactor. This design facilitates the formation of reflux in localized areas outside the baffle, increasing the pressure in those areas and thus improving the reaction rate and promoting a forward shift in the CO2 to methanol reaction equilibrium. Multiple catalyst beds are located both inside and outside the baffle, which can be filled with different types of granular solid catalysts to control the reaction path and products in each bed section. A thermocouple is installed at the top of the reactor to measure the temperature inside the baffle. Figure 2The diagram shows a top view of the thermocatalytic reactor 10 and the outer catalyst bed 13, including the thermocatalytic reactor 10, a baffle plate 12, the outer catalyst bed 13, the inner catalyst bed 14, a filling hole 20, a gas inlet 21, and a gas outlet 22. The baffle plate 12 is a glass tube with an outer diameter of 6-8 mm and a wall thickness of 1 mm, welded to the bottom of the thermocatalytic reactor 10, dividing the reactor into an inner and outer layer. The top of the baffle plate 12 is 10-200 mm above the top of the thermocatalytic reactor 10. The gas inlet 21 has an inner diameter of 8-10 mm. Gas enters the inner layer of the thermocatalytic reactor 10 through the gas inlet 21, then flows to the outer layer, and finally exits from the gas outlet 22 at the bottom of the outer layer. The gas outlet 22 also has an inner diameter of 8-10 mm.

[0037] Specifically, to ensure sufficient contact between the catalyst and the gas, and to control the reaction pathway and products, the catalyst bed adopts a segmented inner and outer layer structure. For example... Figure 2 As shown, the outer catalyst bed 13 is a metal ring with an outer diameter of 10-14 mm, an inner diameter of 5-7 mm, and a thickness of 2-4 mm, which is fixed to the space between the thermocatalytic reactor 10 and the partition plate 12 by screws. The inner catalyst bed 14 is a metal ring with an outer diameter of 4-6 mm, an inner diameter of 0.5 mm, and a thickness of 2-4 mm, which is fixed to the space inside the partition plate 12 by screws. There are 12 small holes with a diameter of 1-2 mm inside the bed for placing particulate catalyst. 3-6 inner catalyst beds 14 are installed inside the space of the partition plate 12, and 3-6 outer catalyst beds 13 are installed outside the space of the partition plate 12. The specific number is controlled according to the actual reaction requirements.

[0038] like Figure 1 As shown, a liquid-phase collection device is used to collect methanol from the outlet of the thermocatalytic reactor. The outlet pipe of the thermocatalytic reactor is wrapped with a heating belt to prevent methanol condensation in the pipe. Low-boiling-point organic compounds in the gas exiting the thermocatalytic reactor are condensed into liquid after entering the liquid-phase collection device, and the remaining gas flows out of the liquid-phase collection device and into the waste gas cylinder. The condensate in the liquid-phase collection device is supplied by a circulating water pump. After the reaction is complete, the ball valve at the bottom of the liquid-phase collection device is opened to collect the liquid-phase products. Gas flowing out of gas outlet 22 enters the liquid-phase collection device 16 through a pipe wrapped with a second heating belt 15. The liquid-phase collection device 16 has a capacity of 300 mL and is supplied with condensate by a second circulating water pump 17, whose temperature control range is -5 to 99.9 ℃. Low-boiling-point organic components in the gas entering the liquid-phase collection device 16 are condensed into liquid and accumulate in the liquid-phase collection device 16. After the reaction is complete, the ball valve 18 at the bottom of the liquid-phase collection device 16 is opened to collect the liquid-phase products in the liquid-phase collection device 16. The gas exiting the liquid phase collection device 16 is collected by the waste gas bottle 19, which has a volume of 10~40 L.

[0039] This invention further provides a method for producing methanol using a low-temperature plasma-assisted catalyst, comprising the following steps:

[0040] (1) The materials used include active components, additives and carriers. Copper nitrate, nickel nitrate or cobalt nitrate are used as active components, zinc nitrate hexahydrate, gallium nitrate, zirconium oxynitrate and other additives are used, and mesoporous alumina, mesoporous silica and other carriers are used.

[0041] (2) Measure the saturated water absorption of the carrier. Take 1 g or less of the carrier and place it in a beaker. Heat the carrier to 45°C and add the pre-prepared impregnation solution with a metal ion concentration of 0.5 mol / L dropwise until it just completely covers the sample. After standing for 4-5 h, filter it and carefully remove the water from the sample surface until there are no obvious water droplets on the sample surface. The mass difference before and after adding the impregnation solution is the saturated water absorption of the carrier.

[0042] (3) Weigh a certain mass of active component, auxiliary agent and carrier solid according to a certain active component: auxiliary agent: carrier (mass ratio). Based on the carrier mass and saturated water absorption, weigh a certain mass of deionized water according to the ratio of deionized water mass: carrier mass = carrier saturated water absorption, dissolve the active component and auxiliary agent solid in the deionized water to obtain the metal precursor solution;

[0043] (4) The above metal precursor solution is added dropwise to the support, and the support heating temperature is maintained at 45 °C so that the solution just impregnates all the support. After impregnation, it is left to stand in a cool place for 12~48 h, then dried at 120 °C for 12 h, and calcined at 400~500 °C for 4 h. Through the above steps, the types of catalysts that can be obtained include, but are not limited to: Cu / Zn / Al2O3 catalyst, Ni / Ga / SiO2 catalyst, Co / Ga / SiO2 catalyst, etc.

[0044] (5) Grind the catalyst obtained through the above steps (1) to (4) into particles of 80 to 200 mesh and fill them into the catalyst bed. Different types of catalysts can be filled into the catalyst bed at different locations according to actual needs.

[0045] (6) Hydrogen gas is introduced into the thermocatalytic reactor filled with catalyst and heated at 300~400 °C for 1 h to reduce the catalyst. After the reduction is completed, CO2 is introduced to react and produce methanol. The reaction temperature is 200~300 °C and the flow rate ratio of CO2 to H2 is 1.0~5.0.

[0046] The foregoing embodiments are used to explain and illustrate the present invention, but not to limit it. Any modifications and changes made to the disclosure of the present invention within the spirit and scope of the claims should be considered as being within the scope of protection of the present invention.

Claims

1. An apparatus for producing methanol using a low-temperature plasma-co-catalyst, characterized in that: The device includes a low-temperature plasma reactor (5), a first circulating water pump (8), a thermal catalytic reactor (10), a partition (12), an outer catalyst bed (13), and an inner catalyst bed (14). The low-temperature plasma reactor (5) is used to activate hydrogen and CO2, and the activated gas is introduced into the thermocatalytic reactor (10). The outer side of the low-temperature plasma reactor (5) contains condensate water, which is supplied by a first circulating water pump (8); a low-temperature plasma electrode is installed inside the low-temperature plasma reactor (5), and the outer layer of the low-temperature plasma reactor (5) has circulating condensate water; The thermocatalytic reactor (10) contains a cylindrical partition (12). The gas inlet is inside the partition (12), and the gas outlet is outside the partition (12). Gas enters the space inside the partition (12) from the bottom of the thermocatalytic reactor (10), and after reaching the top of the thermocatalytic reactor (10), it flows out from the bottom gas outlet outside the partition (12). The gas forms a backflow at a local position outside the partition (12). The gas inlet pipe and outlet pipe of the thermocatalytic reactor (10) are wrapped with heating tape. Several catalyst outer beds (13) are fixed on the outside of the partition (12) of the thermocatalytic reactor (10), and several catalyst inner beds (14) are fixed on the inside. Each catalyst outer bed (13) and catalyst inner bed (14) is filled with the same or different types of catalyst to control the reaction path and products of each catalyst outer bed (13). After the catalyst on the catalyst outer bed (13) is reduced by non-thermodynamic equilibrium hydrogen active particles, non-thermodynamic equilibrium carbon and oxygen active particles are introduced to produce methanol.

2. A method for producing methanol using a low-temperature plasma-co-catalyst based on the apparatus of claim 1, characterized in that, Includes the following steps: Step (1): Measure the saturated water absorption of the carrier; place the carrier in a glass dish and add deionized water drop by drop until it just completely covers the sample. After standing, remove the water from the sample surface. The mass difference before and after adding water is the saturated water absorption of the carrier. Step (2): Weigh out the corresponding mass of deionized water according to the carrier mass and saturated water absorption capacity, and dissolve the active component and auxiliary agent solid in the deionized water according to the ratio of deionized water mass: carrier mass = carrier saturated water absorption capacity to obtain a metal precursor solution; the active component is copper nitrate, nickel nitrate or cobalt nitrate; the auxiliary agent is zinc nitrate hexahydrate, gallium nitrate or zirconium oxynitrate. Step (3): The above metal precursor solution is added dropwise to the support, so that the solution just impregnates all the support. After impregnation, the solution is allowed to stand, dried, and calcined to obtain the catalyst, which is then ground into particles. The support is mesoporous alumina or mesoporous silica. Step (4): According to actual needs, repeat steps (1) to (3) several times to obtain several catalysts, which are then filled into different catalyst outer beds (13) of the thermocatalytic reactor (10); Different catalyst outer beds (13) are separated by partitions (12); the catalysts obtained include: Cu / Zn / Al2O3 catalyst, Ni / Ga / SiO2 catalyst and Co / Ga / SiO2 catalyst; Step (5): Hydrogen gas is introduced into the low-temperature plasma reactor (5) to generate hydrogen active particles, which are then introduced into the thermocatalytic reactor (10) to reduce the catalyst. Gas enters the space inside the partition (12) from the bottom of the thermocatalytic reactor (10), and flows out from the bottom gas outlet outside the partition (12) after reaching the top of the thermocatalytic reactor (10); gas forms a backflow at a local position outside the partition (12); Step (6): CO2 is introduced into the low-temperature plasma reactor (5) to generate carbon and oxygen active particles, which are then introduced into the thermocatalytic reactor (10) to produce methanol.

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