CN113816831B - Method for preparing methanol by reforming plasma-thermal coupling methane and steam - Google Patents

Abstract

The invention relates to a method for preparing methanol by plasma-thermally coupling methane and steam reforming, and belongs to the technical field of methane resource utilization and plasma chemical synthesis. The active component of the metal-supported catalyst is Cu, and the carrier includes SiO ₂ , Al ₂ O ₃ , ZrO ₂ , CeO ₂ , TiO ₂ , Fe ₂ O ₃ , and zeolite molecular sieve; The weight percentage is 1%-10%. The discharge reaction zone is maintained at 170°C and 0.1MPa, the ratio of methane to water vapor is 1:4, and the selectivity of methanol can reach 58%. The method has mild conditions, and the used catalyst is highly dispersed and has stable catalytic activity, and belongs to a one-step direct synthesis process. The method is simple, the raw materials are cheap, and there is no pollution.

Description

A method of plasma-thermal coupling methane and steam reforming to make methanol

technical field

The invention belongs to the technical field of methane resource utilization and plasma chemical synthesis, and relates to a method suitable for plasma catalytic methane steam reforming to produce methanol, a metal-supported catalyst and a preparation method thereof.

Background technique

Methane, the main component of natural gas, is abundant in reserves and is an important carbon resource. At the same time, methane is also a greenhouse gas. Methanol is a liquid under normal temperature and pressure, which is convenient for storage and transportation. It is an important chemical raw material and can be used to produce high value-added chemical products such as olefins, aromatic hydrocarbons, gasoline additive methyl tertiary butyl ether, etc. Therefore, the conversion of methane to methanol is of great significance.

In the industry, a two-step method is mainly used to convert methane into methanol. The first step is to reform the methane and H ₂ O to produce synthesis gas (CO and H ₂ ) at a high temperature above 800 °C; Methanol was synthesized under the action of Cu-Zn-Al catalyst at about 100 atm. The key research is on the modification of Ni-based catalysts, by adding additives to improve catalyst activity, high temperature thermal stability and anti-coking performance, and to develop catalysts with high activity at low temperatures.

Published patent CN10738162A (patent number: CN201710187240.0) synthesized a core-shell structure Ni@Al ₂ O ₃ catalyst, using the nano-confinement effect of the core-shell structure catalyst to significantly improve the dispersion of Ni and prevent Ni nanoparticles from Aggregation under high temperature conditions improves the anti-carbon deposition ability of the catalyst.

Syngas can further produce methanol through Fischer-Tropsch synthesis, and the current published patent research mainly focuses on the morphology modification of Cu-Zn-Al catalysts;

The catalyst synthesized by the published patent CN112023933A (patent number: CN202010803153.5) uses hydrotalcite as a template, and utilizes the property of in-situ hydration after calcination of hydrotalcite to realize the orderly distribution of Cu and Zn components on the lamellar structure. The confinement of the hydrotalcite lamella structure makes the active components less likely to agglomerate during the high temperature reaction, and has better thermal stability.

The conversion of methane to methanol can also be carried out by thermal catalysis, photocatalysis, electrocatalysis and biomass conversion.

The reaction of methane oxidation to methanol can be divided into homogeneous catalysis and heterogeneous catalysis. Homogeneous catalysis is mostly a sulfuric acid-based reaction system, that is, using sulfuric acid as the reaction medium, using noble metals such as Pt, Pd, Hg, Rh as the central atom to activate methane and break the CH bond, and then functionalize the _CH3 coordinated to the central atom. for methanol.

The published document "J.Am.Chem.Soc.2016, 138, 12395-12400" reported that potassium tetrachloroplatinate (K ₂ PtCl ₄ ) is a highly active, selective and stable catalyst. The TOF in oleum is over 25000h ^-1 and the selectivity is higher than 98%.

For heterogeneous catalysis, various catalytic materials have developed rapidly in recent years. Au-Pd alloy catalyst coupled with H ₂ O ₂ can oxidize methane to methanol with high selectivity (>90%) at low temperature.

The published document "Science, 2020, 367, 193-197" reported a "molecular fence" strategy, in which H ₂ and O ₂ synthesized H ₂ O ₂ in situ on the catalyst of zeolite-immobilized Au-Pd alloy nanoparticles, which significantly improved the H 2 O 2 _The utilization rate of _2O2 , under mild conditions (70 °C), the methane conversion was 17.3%, and the methanol selectivity was 92 _% . Cu-based or Fe-based zeolite catalysts with N ₂ O as the oxidant are widely used in the oxidation of methane to methanol. For Cu molecular sieve catalysts, firstly activate at high temperature (>450°C) in _O2 or air; the activated catalyst reacts with methane at low temperature (~200°C) to generate adsorbed CH3O species _; Steam extraction to desorb the methanol yields the product. For Fe-based zeolite catalysts, _N2O first oxidizes Fe ^II species on the surface of Fe-based zeolite to Fe ^III species, and then reacts with methane to break its CH bond and generate adsorbed methanol. To avoid the deep oxidation of methanol, Cu-based and Fe-based molecular sieve catalysts mainly realize the oxidation of methane to methanol through multi-step non-catalytic stoichiometric reactions.

The publication "Angew.Chem.Int.Ed.2016, 55, 5467-5471" reported that the Cu-Mordenite catalyst can increase the methanol yield by increasing the partial pressure of methane during the isothermal chemical cycle process. When the methane pressure is 37 bar, the yield of methanol is 56.2 μmol/g _cat

The published document "ACS Catal.2017, 7, 1403-1412" proposes that the Cu-Mordenite molecular sieve prepared by solid-state ion exchange method can generate more different active sites than the catalyst prepared by liquid ion exchange method, thereby improving O ₂ catalysis of methane conversion efficiency.

The published document "J.Am.Chem.Soc., 2017, 139, 14961-14975" reported that the Cu-SSZ-13 catalyst achieved a methanol yield of 107 μmol/g _cat by prolonging the activation time and increasing the partial pressure of methane . After four cycles, the yield reached 125 μmol/g _cat .

The published literature "Science, 2021, 373, 327–331" compares the reaction results of Fe-BEA type molecular sieves and Fe-CHA type molecular sieves. The detailed spectral characterization and density functional theory calculations of the reaction intermediates show that the diffusion of small pore size is not hindered. It is beneficial to prematurely release CH _radicals from the active sites after CH activation, thereby promoting radical reorganization to form methanol.

Published patent CN111333487 A (patent number: CN202010298935.8) discloses a method for preparing methanol by photocatalytic oxidation of methane, using composite Au/ZnO as a photocatalyst, introducing methane and oxygen, and replacing the irradiation in the ultraviolet region with a full-spectrum Irradiation can not only meet the energy demand in the reaction, but also avoid the decomposition and oxidation of the generated methanol into formaldehyde caused by excessive light energy input, and the methanol selectivity reaches 100%.

Published patent CN101775614A (patent number: CN201010106288.2) proposes to use a closed electrolytic cell, with hollow porous graphite as the anode and stainless steel as the cathode, methane gas is directly passed into the porous graphite anode, and the current is turned on to generate electricity in the electrolyte. Methanol, NaOH, NaCl or NaF constituting the electrolyte are recycled in the whole process without consumption.

Published patent CN1580269A (patent number: CN03143797.4) discloses a method for preparing methanol from biocatalytic methane. Using methane-oxidizing bacterial cells as a catalyst and a mixed gas of methane, carbon dioxide and oxygen as a raw material gas, the methanol aqueous solution is obtained after the reaction at 32-40° C. and 0-1.2 MPa. It solves the problem that the cell activity is reduced due to the consumption of coenzyme NADH, and the reaction cannot be carried out continuously due to intermittent regeneration or adding other exogenous electron donors, and realizes the in-situ regeneration of coenzyme NADH in the reaction system.

There are many defects and deficiencies in the currently widely researched technologies: industrially, a two-step method is used to convert methane into methanol. The high temperature and high pressure conditions lead to high operating investment, equipment investment and equipment maintenance costs; in homogeneous catalysis, the catalyst cost is high and the reaction medium It is highly corrosive, has strict equipment requirements, and is difficult to separate products. In heterogeneous catalysis, high methane conversion and high methanol selectivity cannot be achieved simultaneously, and most of them use H ₂ O ₂ or N ₂ O as the oxidant to achieve the purpose of oxidation at low temperature, but the price is expensive. In the photocatalytic system, the methanol yield is low.

So far, there are very few published literatures and published patents on the one-step direct production of methanol from methane and steam.

The published document "Science, 2017, 356, 523–527" proposes to use water to selectively anaerobic oxidize methane to methanol, adopting an isothermal chemical cycle method, through the combination of Cu/MOR catalyst and oxidant H ₂ O to achieve anaerobic methanol production, methanol selectivity up to 97%. However, the reaction is limited by thermodynamics and has been questioned by many parties.

The published document "J.Am.Chem.Soc.2020, 142, 11962-11966" proposes a process of partially oxidizing methane into methanol using a Cu-SSZ-13 catalyst in a continuous flow reactor, and the main source of O is H ₂ O, not O ₂ . This process was confirmed experimentally in the absence of molecular oxygen and using ¹⁸ O-labeled water.

As the fourth state of matter, plasma is rich in high-energy electrons, which can activate inert raw material molecules (methane and H ₂ O) into active species such as free radicals, excited atoms and ions through inelastic collisions. At present, low temperature plasma technology has been widely used in the conversion of methane, but most of the products are syngas or hydrocarbon compounds. To date, only a few publications and published patents have reported the detection of methanol in the low temperature plasma conversion of methane and water vapor.

The publication "Phys.Chem.Chem.Phys., 2012, 14, 3444-3449" proposes that methanol is the main product when argon gas mixed with water and methane is discharged at 11K and condensed into a solid matrix. Experiments with ² H, ¹⁷ O, and ¹⁸ O-labeled compounds suggest that the mechanism of methanol production may be the insertion of excited oxygen atoms in the 1D state into the CH of the methane molecule.

The open document "Journal of Environmental Engineering and Technology, 2013, 2, 35-39" reported a method for converting methane and water vapor by DBD plasma, suggesting that the selectivity of methanol is very sensitive to the mixing ratio of methane and H ₂ O, When methane is mixed with H ₂ O at a gas mixing ratio of 1:5, the selectivity to methanol is about 20%.

Published patent CN111974393A (patent number: CN202010968347.0) discloses a preparation method of a catalyst for preparing methanol from low temperature plasma-optical coupling of methane and a method for preparing methanol. The plasma generates high-energy electrons, which activate methane at room temperature and pressure. The addition of Cu-C catalyst enables the light generated by the plasma to be utilized to activate H ₂ O, which further improves the yield of methanol.

For the disclosed plasma-catalyzed methane-to-methanol methods, there are many problems of excessive oxidation and low methanol yield.

To sum up, the existing published literatures and published patents involved in the one-step methanol production by steam reforming of methane have problems such as thermodynamic limitation, low methanol yield or harsh reaction conditions, and basically do not involve catalytic materials for the reaction results. Impact. Therefore, the use of plasma to synergize with catalysts at room temperature and pressure to realize one-step methanol production from steam reforming of methane has high application prospects.

SUMMARY OF THE INVENTION

The present invention aims to provide a method for preparing methanol by plasma-thermal coupling of methane and steam reforming.

Technical scheme of the present invention:

A method for producing methanol by plasma-thermal coupling of methane and water vapor. Methane, water vapor and argon are passed into a dielectric barrier discharge reactor, methane molecules and water molecules are activated through dielectric barrier discharge, and the The activated methane molecules and water molecules are converted into methanol under the action of the metal-supported catalyst; wherein, the metal-supported catalyst comprises an active component and a carrier, the active components are Cu, Ni, Zr, and the carrier is SiO ₂ or Zeolite molecular sieve, the mass percentage of active components in the metal-supported catalyst is 1-20%; the molar ratio of methane to water vapor is 1:0.1-10, and the residence time of the mixed gas in the reaction zone is 0.01-100s , The dielectric barrier discharge adopts high voltage AC power supply, the power supply frequency is 1kHz-50kHz, the discharge pressure is -0.06MPa-0.2Mpa, and the reaction temperature is 100-500℃.

Further, the method is realized by adopting the following dielectric barrier discharge reactors:

The dielectric barrier discharge reactor is a wire-cylinder type reactor, the reactor is cylindrical, and the outer surface is covered with aluminum foil, and then a metal wire is wound on the surface of the aluminum foil as a ground electrode; the upper end of the cylinder is provided with a central hole. The upper head is provided with a metal rod along the axis of the reactor through the central hole as a high-voltage electrode; the distance between the outer wall of the metal rod and the inner wall of the cylindrical reactor is 0.3-30mm; the cylindrical reactor is a single-layer medium Insulation Materials;

The upper end of the reactor is provided with methane, water vapor and argon inlets, located above the discharge zone, the lower end of the reactor is connected to the collector, the collector is placed in the cold trap, and the rear end of the collector is connected to the tail gas outlet; the catalyst is placed in the reactor. In the discharge area, the catalyst bed is supported by a quartz sand board; a heating furnace is set outside the discharge area as a heat preservation device.

Further, the residence time of the mixed gas in the reaction zone is 0.1-10s.

Further, the molar ratio of methane to water vapor is 1:2-6.

Further, the discharge pressure is taken as 0.1MPa.

Further, the reaction temperature is 150-250°C.

Further, the weight percentage of the active components in the catalyst is 3-10%.

Further, the weight percentage of the active components in the metal-supported catalyst is 3-10%.

Further, the distance between the outer wall of the metal rod and the inner wall of the cylindrical reactor is 1-5 mm.

Further, the dielectric barrier discharge adopts a high-voltage AC power supply, and the power supply frequency is 12kHz-15kHz.

Further, when the dielectric barrier discharge is used, the high voltage electrode and the ground electrode are made of copper, iron, tungsten, aluminum or stainless steel.

Further, the material of the reactor is made of quartz glass, hard glass, alumina ceramics, polytetrafluoroethylene or non-metallic composite materials.

The beneficial effects of the invention are as follows: the method has mild conditions, the used catalyst is highly dispersed and has stable catalytic activity, belongs to a one-step direct synthesis process, and has the advantages of simple method, cheap raw materials and no pollution. It is suitable for the synthesis of various organic compounds from C ₁ -C ₄ alkanes, alkenes, alkynes and steam. In addition to methanol, products such as ethanol, acetaldehyde, acetic acid, and acetone can also be obtained by plasma synthesis.

Description of drawings

Fig. 1 Diagram of experimental setup for CH ₄ /H ₂ O/Ar plasma reaction.

FIG. 2 is an analysis diagram of GC-MS results of methane steam reforming reaction products.

Detailed ways

The specific embodiments of the present invention will be described in detail below with reference to the technical solutions and the accompanying drawings.

Comparative Example 1

The reaction pressure is 0.1MPa, the external heating furnace is set to 200°C for heat preservation, and argon, methane and water vapor are in a molar ratio of 2:1:3 (wherein the argon flow rate is 40ml/min, and the methane flow rate is 20ml/min, The water vapor flow rate was 60 ml/min) into the discharge reactor. First, feed the reaction raw material gas to replace the air in the reaction system, and at the same time, the raw material gas is heated and premixed for 30 minutes. After the raw material gas is evenly mixed, the plasma power is turned on to start discharging. The reactor structure is a single medium barrier wire-barrel reactor. The stainless steel rod installed in the quartz tube is used as the internal electrode, and the aluminum foil wrapped around the outer wall of the quartz tube is used as the ground electrode. The diameter of the inner electrode was 2 mm, and the discharge gap was 3.5 mm. The length of the discharge zone is 50mm. A sieve plate is arranged at the lowest end of the discharge area in the quartz tube.

The plasma discharge parameters are: power 7W, frequency 14.5kHz. The discharge time is 2.5h. The reaction product includes gas-liquid two-phase, the gas-phase product is directly analyzed online by gas chromatography, and the liquid-phase product is collected by a cold trap and qualitatively and quantitatively analyzed by gas chromatography. The reaction results are: methane conversion rate is 3.4%, liquid phase product selectivity is 62%, methanol selectivity is 46.67%, and by-products include ethane, ethylene, propane, formaldehyde, ethanol, propanol, acetaldehyde, acetic acid, Propionaldehyde, Acetone.

Comparative Example 2

Comparative Example 1 was repeated, and 1.4 g of catalyst silica (SiO ₂ ) was charged into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, and the catalyst is calcined at 500°C for 5h before the reaction. The external heating furnace temperature was set to 200°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the methane conversion was 4.758%, the liquid phase product selectivity was 31.32%, and the methanol selectivity was 21.8799%.

Example 1:

Comparative Example 2 was repeated with 1.4 g of silica-supported copper catalyst (denoted as Cu/SiO ₂ ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Cu is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 200°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product was analyzed, and the conversion rate of methane was 7.0645%, the selectivity of liquid phase product was 67.7349%, and the selectivity of methanol was 51.7905%.

Example 2:

Comparative Example 2 was repeated with 1.4 g of silica-supported nickel catalyst (denoted as Ni/SiO ₂ ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount based on element Ni is 5% by weight, and the catalyst calcination temperature is 540°C. The temperature of the external heating furnace is set to 200°C. The discharge parameters are set to: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the methane conversion was 6.9371%, the liquid-phase product selectivity was 60.0491%, and the methanol selectivity was 42.9067%.

Example 3:

Comparative Example 2 was repeated with 1.4 g of silica-supported zirconium catalyst (denoted as Zr/SiO ₂ ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount based on element Zr is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 200°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the methane conversion was 6.5505%, the liquid phase product selectivity was 61.6109%, and the methanol selectivity was 46.4062%.

Comparative Example 3:

Comparative Example 2 was repeated with 1.4 g of silica-supported zinc catalyst (denoted as Zn/SiO ₂ ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount based on element Zn is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 200°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product was analyzed, and the conversion rate of methane was 5.6179%, the selectivity of liquid phase product was 45.2417%, and the selectivity of methanol was 32.5047%.

Comparative Example 4:

Comparative Example 2 was repeated with 1.4 g of silica-supported cerium catalyst (denoted as Ce/SiO ₂ ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Ce is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 200°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the methane conversion was 5.6425%, the liquid phase product selectivity was 50.3949%, and the methanol selectivity was 32.8805%.

Comparative Example 5:

Comparative Example 2 was repeated with 1.4 g of silica-supported indium catalyst (denoted as In/SiO ₂ ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element In is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 200°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product was analyzed, and the conversion rate of methane was 6.6447%, the selectivity of liquid phase product was 49.2487%, and the selectivity of methanol was 31.9472%.

Comparative Example 6:

Comparative Example 2 was repeated with 1.4 g of silica-supported molybdenum catalyst (denoted as Mo/SiO ₂ ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount based on element Mo is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 200°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the methane conversion was 5.8052%, the liquid-phase product selectivity was 53.6229%, and the methanol selectivity was 31.7457%.

Comparative Example 7:

Comparative Example 2 was repeated with 1.4 g of silica-supported vanadium catalyst (denoted as V/ _SiO2 ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount in terms of element V is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 200°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product was analyzed, and the conversion rate of methane was 5.9199%, the selectivity of liquid phase product was 60.9905%, and the selectivity of methanol was 18.1337%.

Comparative Example 8:

Comparative Example 2 was repeated with 1.4 g of silica-supported cobalt catalyst (denoted as Co/SiO ₂ ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as elemental Co is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 200°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the methane conversion was 6.6188%, the liquid-phase product selectivity was 41.5620%, and the methanol selectivity was 26.8252%.

Comparative Example 9:

Comparative Example 2 was repeated with 1.4 g of silica-supported iron catalyst (denoted as Fe/SiO ₂ ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount in terms of element Fe is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 200°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the methane conversion was 5.2315%, the liquid-phase product selectivity was 60.9101%, and the methanol selectivity was 39.0470%.

Comparative Example 10:

Comparative Example 2 was repeated with 1.4 g of silica-supported chromium catalyst (denoted as Cr/SiO ₂ ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as elemental Cr is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 200°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the methane conversion was 5.6511%, the liquid-phase product selectivity was 45.6455%, and the methanol selectivity was 31.7853%.

Comparative Example 11:

Comparative Example 2 was repeated with 1.4 g of silica-supported manganese catalyst (denoted as Mn/SiO ₂ ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading in element Mn is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 200°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the conversion rate of methane was 5.6437%, the selectivity of the liquid phase product was 49.0066%, and the selectivity of methanol was 34.8710%.

Table 1 Evaluation results of catalytic performance of different supported metal catalysts

The methane conversion and methanol selectivity were the highest when the active component was Cu.

Example 4:

Example 1 was repeated with 1.4 g of silica-supported copper catalyst (denoted as Cu/ _SiO2 ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Cu is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 130°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the methane conversion was 3.4212%, the liquid-phase product selectivity was 62.2659%, and the methanol selectivity was 46.6784%.

Example 5:

Example 1 was repeated with 1.4 g of silica-supported copper catalyst (denoted as Cu/ _SiO2 ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Cu is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 150°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product was analyzed, and the conversion rate of methane was 6.7758%, the selectivity of liquid phase product was 68.0023%, and the selectivity of methanol was 50.0876%.

Example 6:

Example 1 was repeated with 1.4 g of silica-supported copper catalyst (denoted as Cu/ _SiO2 ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Cu is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 170°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the methane conversion was 6.8823%, the liquid-phase product selectivity was 72.9074%, and the methanol selectivity was 55.4087%.

Example 7:

Example 1 was repeated with 1.4 g of silica-supported copper catalyst (denoted as Cu/ _SiO2 ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Cu is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 250°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product was analyzed, and the conversion rate of methane was 7.9023%, the selectivity of liquid phase product was 58.3080%, and the selectivity of methanol was 44.2637%.

Example 8:

Example 1 was repeated with 1.4 g of silica-supported copper catalyst (denoted as Cu/ _SiO2 ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:3 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 60ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Cu is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 300°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the methane conversion was 8.1125%, the liquid phase product selectivity was 54.4213%, and the methanol selectivity was 37.7455%.

Table ₂ Evaluation results of catalytic performance of Cu/SiO catalysts with different external heating temperatures

The external heating temperature is preferably 170°C.

Example 9:

Example 6 was repeated with 1.4 g of silica-supported copper catalyst (denoted as Cu/ _SiO2 ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:1 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 20ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Cu is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 170°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the methane conversion was 8.3874%, the liquid-phase product selectivity was 48.0491%, and the methanol selectivity was 27.5474%.

Example 10:

Example 6 was repeated with 1.5 g of silica-supported copper catalyst (denoted as Cu/ _SiO2 ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:2 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 40ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Cu is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 170°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the methane conversion was 7.9067%, the liquid-phase product selectivity was 68.5687%, and the methanol selectivity was 46.7642%.

Example 11:

Example 6 was repeated with 1.4 g of silica-supported copper catalyst (denoted as Cu/ _SiO2 ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:4 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 80ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Cu is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 170°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product was analyzed, and the conversion rate of methane was 6.3975%, the selectivity of liquid phase product was 75.2453%, and the selectivity of methanol was 58.7456%.

Example 12:

Example 6 was repeated with 1.4 g of silica-supported copper catalyst (denoted as Cu/ _SiO2 ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:5 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 100ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Cu is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 170°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product was analyzed, and the conversion rate of methane was 4.8026%, the selectivity of liquid phase product was 65.5188%, and the selectivity of methanol was 50.7685%.

Example 13:

Example 6 was repeated with 1.4 g of silica-supported copper catalyst (denoted as Cu/ _SiO2 ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:6 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 120ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Cu is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 170°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the methane conversion was 3.0401%, the liquid-phase product selectivity was 61.5096%, and the methanol selectivity was 48.8805%.

Example 14:

Example 4 was repeated with 1.4 g of silica-supported copper catalyst (denoted as Cu/ _SiO2 ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:7 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 140ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Cu is 5% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 170°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the methane conversion was 3.3680%, the liquid-phase product selectivity was 50.9281%, and the methanol selectivity was 42.5177%.

Table ₃ Evaluation results of catalytic performance of Cu/SiO catalysts with different methane water vapor ratios

The preferred ratio of methane to water vapor is 1:4.

Example 15:

Example 11 was repeated with 1.4 g of silica-supported copper catalyst (denoted as Cu/ _SiO2 ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:4 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 80ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Cu is 1% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 170°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product was analyzed, and the conversion rate of methane was 5.7289%, the selectivity of liquid phase product was 49.9668%, and the selectivity of methanol was 35.3669%.

Example 16:

Example 11 was repeated with 1.4 g of silica-supported copper catalyst (denoted as Cu/ _SiO2 ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:4 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 80ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Cu is 3% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 170°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product analysis showed that the methane conversion was 5.8084%, the liquid-phase product selectivity was 64.0302%, and the methanol selectivity was 46.5517%.

Example 17:

Example 11 was repeated with 1.4 g of silica-supported copper catalyst (denoted as Cu/ _SiO2 ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:4 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 80ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Cu is 7% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 170°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product was analyzed, and the conversion rate of methane was 6.2993%, the selectivity of liquid phase product was 69.4974%, and the selectivity of methanol was 53.6275%.

Example 18:

Example 11 was repeated with 1.4 g of silica-supported copper catalyst (denoted as Cu/ _SiO2 ) loaded into the discharge zone of the dielectric barrier discharge plasma reactor. The molar ratio of argon, methane and water vapor is 2:1:4 (wherein the flow rate of argon is 40ml/min, the flow rate of methane is 20ml/min, and the flow rate of water vapor is 80ml/min). The catalyst is 20-40 mesh particles, wherein the active ingredient loading amount calculated as element Cu is 10% by weight, and the catalyst calcination temperature is 540°C. The external heating furnace temperature was set to 170°C. The discharge parameters are set as: power 7W, frequency 14.5kHz. After 2.5 hours of discharge, the product was analyzed, and the conversion rate of methane was 6.3975%, the selectivity of liquid phase product was 75.2453%, and the selectivity of methanol was 58.7456%.

Table ₄ Evaluation results of catalytic performance of Cu/SiO catalysts with different copper loadings (weight)

The preferred Cu loading is 5% by weight.

Claims (10)

1. a method for plasma-thermally coupled methane and steam reforming to make methanol, is characterized in that, methane, water vapor and argon are passed into the dielectric barrier discharge reactor, and methane molecules and water are made by dielectric barrier discharge. The molecule is activated, and the activated methane molecules and water molecules are converted into methanol under the action of the metal-supported catalyst; wherein, the metal-supported catalyst includes an active component and a carrier, the active component is Cu, and the carrier is SiO ₂ or zeolite molecular sieve, the mass percentage of active components in the metal-supported catalyst is 1-20%; the molar ratio of methane to water vapor is 1:0.1-10, and the residence time of the mixed gas in the reaction zone is 0.01 For -100s, the dielectric barrier discharge adopts high-voltage AC power supply, the power supply frequency is 1kHz-50kHz, the discharge pressure is -0.06MPa-0.2Mpa, the discharge power is 7W, and the reaction temperature is 150-250℃; a heating furnace is set outside the discharge area for heat preservation device. 2. the method for a kind of plasma-thermal coupling methane and steam reforming to make methanol according to claim 1, is characterized in that, described method adopts following dielectric barrier discharge reactor to realize: The dielectric barrier discharge reactor is a wire-cylinder type reactor, the reactor is cylindrical, and the outer surface is covered with aluminum foil, and then a metal wire is wound on the surface of the aluminum foil as a ground electrode; the upper end of the cylinder is provided with a central hole. The upper head is provided with a metal rod along the axis of the reactor through the central hole as a high-voltage electrode; the distance between the outer wall of the metal rod and the inner wall of the cylindrical reactor is 0.3-30mm; the cylindrical reactor is a single-layer medium Insulation Materials; The upper end of the reactor is provided with methane, water vapor and argon inlets, located above the discharge zone, the lower end of the reactor is connected to the collector, the collector is placed in the cold trap, and the rear end of the collector is connected to the tail gas outlet; the catalyst is placed in the reactor. In the discharge area, the catalyst bed is supported by a quartz sand plate. 3. the method for a kind of plasma-thermal coupling methane and steam reforming to make methanol according to claim 1 and 2, is characterized in that, the residence time of mixed gas in reaction zone is 0.1-10s, methane and water The molar ratio of steam is 1:2-6; the discharge pressure is 0.1MPa. 4. the method for a kind of plasma-thermal coupling methane and steam reforming to make methanol according to claim 1 or 2, is characterized in that, the weight percent that described active component accounts for in catalyst is 3-10 %. 5. the method for a kind of plasma-thermal coupling methane and steam reforming to make methanol according to claim 3, is characterized in that, the weight percent of described active component in metal-supported catalyst is 3- 10%. 6. The method for producing methanol by plasma-thermal coupling methane and steam reforming according to claim 1, 2 or 5, wherein the distance between the outer wall of the metal rod and the inner wall of the cylindrical reactor It is 1-5mm; the dielectric barrier discharge adopts high-voltage AC power supply, and the power supply frequency is 12kHz-15kHz. 7. the method for a kind of plasma-thermal coupling methane and steam reforming to make methanol according to claim 3, is characterized in that, the distance between the outer wall of metal rod and cylindrical reactor inner wall is 1-5mm ; The dielectric barrier discharge adopts high voltage AC power supply, and the power supply frequency is 12kHz-15kHz. 8. the method for a kind of plasma-thermal coupling methane and steam reforming to make methanol according to claim 4, is characterized in that, the distance between the outer wall of metal rod and cylindrical reactor inner wall is 1-5mm ; The dielectric barrier discharge adopts high voltage AC power supply, and the power supply frequency is 12kHz-15kHz. 9. The method for producing methanol by plasma-thermal coupling of methane and steam reforming according to claim 1, 2, 5, 7 or 8, characterized in that, when dielectric barrier discharge is used, the high voltage electrode is connected to the ground. The material of the electrode is copper, iron, tungsten, aluminum or stainless steel; the material of the reactor is made of quartz glass, hard glass, alumina ceramic, polytetrafluoroethylene or non-metallic composite material. 10. The method for producing methanol by plasma-thermal coupling of methane and steam reforming according to claim 6, wherein when dielectric barrier discharge is adopted, the high-voltage electrode and the ground electrode are made of copper, iron, tungsten , aluminum or stainless steel; the blocking medium is made of quartz glass, hard glass, alumina ceramics, polytetrafluoroethylene or non-metallic composite materials.

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