Process for the catalytic co-conversion of methane-nitrogen-water to methanol and ammonia under plasma conditions

Abstract

The present application relates to the field of low-temperature plasma catalysis, and particularly relates to a method for catalytic conversion of methane-nitrogen-water to methanol and ammonia under plasma conditions.The present application discloses a preparation method of a high-entropy alloy catalyst, comprising the following steps: mixing powdery iron, nickel, vanadium, niobium, silver, copper and titanium, and then smelting the mixture into an alloy ingot under an inert gas atmosphere, and then performing annealing treatment and grinding, and then using a nitric acid solution as an etching solution to obtain a high-entropy alloy powder.The present application combines an efficient high-entropy alloy catalyst under plasma conditions to efficiently catalyze the collaborative conversion of methane-nitrogen-water, and directly prepare methanol and ammonia, thereby realizing comprehensive utilization of methane and nitrogen under mild conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of low-temperature plasma catalysis, and particularly relates to a method for catalyzing the collaborative conversion of methane-nitrogen-water into methanol and ammonia under plasma conditions. BACKGROUND

[0002] Ammonia and methanol are both important chemical raw materials and products. At present, the global synthetic ammonia industry is still mostly based on the Haber-Bosch process which has a history of more than 100 years. This process is a significant capital and energy-intensive industry, and about 2% of the world's energy is used for synthetic ammonia every year. In industrial ammonia synthesis, according to the source of hydrogen, synthetic ammonia is divided into a petroleum route, a coal route and a natural gas route. Among them, the route taking natural gas as the hydrogen source is the most popular ammonia production process in the world. In terms of methanol synthesis, the route adopted in industry is the synthesis gas process, that is, first, synthesis gas is prepared by steam reforming of methane, and then methanol is synthesized by the Fischer-Tropsch process. Since the C-H bond of methane is very stable and the dissociation energy is as high as 435 kJ / mol. This brings challenges to the activation and conversion of methane, which usually requires harsh conditions such as high temperature, super strong acid or free radicals. Therefore, under mild conditions, catalytic directional conversion of methane, especially with methanol as the target product, is a long-sought holy grail reaction. This also leads to the fact that the traditional synthetic ammonia process has a long process route, requires high temperature and high pressure conditions, has huge energy consumption, and has great safety hazards; the steam reforming process of methane has a huge thermodynamic barrier and consumes a large amount of energy. SUMMARY

[0003] The technical problem to be solved by the present application is to realize the efficient catalytic collaborative conversion of methane-nitrogen-water under mild conditions, and to continuously produce methanol and ammonia with high selectivity based on a plasma-based method.

[0004] In order to solve the above technical problems, the present application provides a preparation method of a high-entropy alloy catalyst, comprising the following steps:

[0005] 1) mixing powdery iron, nickel, vanadium, niobium, silver, copper and titanium according to a molar ratio of (1-2):(1-2):(1-2):(1-2):(1-2):(1-2):(1-2) as alloy raw material powder;

[0006] melting the alloy raw material powder into an alloy ingot under an inert gas (such as argon) atmosphere;

[0007] Note: the above melting can be carried out in a vacuum arc melting furnace;

[0008] 2) annealing the alloy ingot, and then naturally cooling it to obtain an annealed alloy ingot;

[0009] The annealing temperature is 1000-1500K, and the annealing time is 1-4h.

[0010] Note: K = °C + 273.15

[0011] 3) Under the atmosphere of inert gas (such as argon), the alloy ingot after annealing treatment is ground (a high-energy ball mill can be used) to obtain an alloy powder;

[0012] 4) The alloy powder is treated using a nitric acid solution as an etching liquid (de-alloying operation, so that the surface roughness of the alloy powder is increased); and then washed and dried to obtain a high-entropy alloy powder.

[0013] As an improvement of the preparation method of the high-entropy alloy catalyst of the present application, in the step 1), the alloy ingot is repeatedly melted for multiple times to ensure the uniformity of the components (alloy components); the number of melting times is 2-10 times.

[0014] As an improvement of the preparation method of the high-entropy alloy catalyst of the present application,

[0015] The purity of iron, nickel, vanadium, niobium, silver, copper and titanium is all ≥ 99.9%.

[0016] That is, the high-purity metal powder is selected as the catalyst raw material.

[0017] As an improvement of the preparation method of the high-entropy alloy catalyst of the present application,

[0018] In the step 3), the particle size of the obtained alloy powder is 20-100 μm.

[0019] As an improvement of the preparation method of the high-entropy alloy catalyst of the present application,

[0020] In the step 4), the concentration of the nitric acid solution is 0.1-2 mol / L (preferably 0.6-1 mol / L); and the treatment time (de-alloying operation time) is 12-48 h.

[0021] The present application also simultaneously provides a method for catalyzing the collaborative conversion of methane-nitrogen-water to produce methanol and ammonia under plasma conditions: using the high-entropy alloy catalyst according to any one of the above methods, and using a plasma reactor device.

[0022] The plasma reactor device comprises a stainless steel rod as a high-voltage electrode, a copper sheet as a grounding electrode, a quartz tube as a dielectric material, the stainless steel rod is sleeved in the inner cavity of the quartz tube, and the quartz tube is coaxial with the axis of the stainless steel rod; the outer surface of the stainless steel rod is kept a certain distance from the inner wall of the quartz tube, thereby forming a channel; the raw material inlet branch pipe and the product outlet branch pipe which are both connected with the channel are arranged on the wall of the quartz tube; the copper sheet is wrapped (tightly wrapped) on the outer wall of the quartz tube between the raw material inlet branch pipe and the product outlet branch pipe, thereby forming a copper sheet layer, and the copper sheet layer is a discharge area; the channel in the quartz tube covered by the copper sheet layer is a catalyst filling area;

[0023] The plasma high-voltage power supply is connected with the stainless steel rod through a high-voltage lead and connected with the copper sheet layer through a grounding lead;

[0024] Filler is arranged in the channel between the raw material inlet branch pipe and the product outlet branch pipe (in the catalyst filling area); the filler is a high-entropy alloy catalyst (which functions to improve the discharge effect and catalyze the reaction);

[0025] The method for synergistically converting methane-nitrogen-water to produce methanol and ammonia comprises the following steps:

[0026] Before the reaction, nitrogen is used to remove air in the channel; the water temperature in the constant-temperature water tank is controlled at 70-95℃ (for example, 90℃);

[0027] Methane and nitrogen are mixed to form a mixed gas, and the volume content of methane in the mixed gas is 15%-75%; the mixed gas is first preheated to 120-150℃, and then is passed into the water in the constant-temperature water tank at a set flow rate, so as to bubble and carry out water vapor; the mixed gas together with the water vapor as the reaction raw gas is passed into the channel through the raw material inlet branch pipe, and the temperature in the channel is controlled at 100-180℃ (i.e., the reaction system is maintained at 100-180℃, preferably 120-180℃);

[0028] The plasma high-voltage power supply generates stable alternating current with a voltage peak value of 0-30kV and a frequency of 1kHz-50kHz, and high-voltage discharge is generated on the reaction raw gas to produce plasma, and catalytic reaction is carried out under the action of the high-entropy alloy catalyst;

[0029] The reaction gas is discharged from the product outlet branch pipe; the reaction gas comprises methanol and ammonia.

[0030] As an improvement of the method for catalytically converting methane-nitrogen-water to produce methanol and ammonia under the plasma condition of the present application: the reaction gas discharged from the product outlet branch pipe is subjected to gas-liquid separation through condensation, so as to realize the separation of methanol and ammonia.

[0031] As a further improvement of the method for catalyzing the methane-nitrogen-water collaborative conversion under the plasma condition of the application to produce methanol and ammonia: the flow rate of the mixed gas is 100-180 mL / min; the residence time of the reaction raw gas in the channel is 0.01-0.03 min.

[0032] The application is a method for catalyzing the methane-nitrogen-water collaborative conversion under the plasma condition, combining with the high-efficiency high-entropy alloy catalyst, to directly produce methanol and ammonia, realizing the comprehensive utilization of methane and nitrogen under mild conditions.

[0033] The device of the application adopts a coaxial tube type dielectric barrier discharge plasma reactor as the reaction device for catalyzing the methane-nitrogen-water collaborative conversion under the plasma condition to produce methanol and ammonia.

[0034] The catalyst of the application comprises a high-entropy alloy containing elements such as iron, nickel, vanadium, niobium, silver, copper and titanium, which is mixed with pure metals, repeatedly melted under vacuum and granulated, and used for catalyzing the methane-water-nitrogen collaborative conversion under the plasma condition to produce methanol and ammonia.

[0035] The application has the following beneficial effects:

[0036] 1. A method for directly synthesizing methanol and ammonia using methane, nitrogen and water as raw materials is developed, realizing the comprehensive utilization of methane and nitrogen.

[0037] 2. The proposed plasma reaction device can continuously perform the plasma catalytic reaction at a constant temperature.

[0038] 3. The proposed catalyst is simple to prepare, easy to regenerate, and has high selectivity and activity for target products.

[0039] In summary, the application adopts the low-temperature plasma catalysis method, introduces high-quality energy into the reaction system, and directly converts methane, nitrogen and water vapor into methanol and ammonia under mild conditions, which not only shortens the process route, but also reduces the reaction conditions, saves energy, realizes the comprehensive utilization of methane and nitrogen, and is a feasible and ideal way. BRIEF DESCRIPTION OF DRAWINGS

[0040] The specific embodiments of the application will be further described in detail below with reference to the accompanying drawings.

[0041] Figure 1 The schematic diagram of the plasma reactor device used in the application.

[0042] Figure 1Middle: 1 is a stainless steel rod, 2 is a quartz tube, 3 is a copper sheet layer, 4 is a channel, 5 is a filler, 6 is a sealing and insulating fastener, 7 is a raw material inlet branch pipe, 8 is a product outlet branch pipe, 9 is a high-voltage wire, 10 is a grounding wire, and 11 is a quartz heat insulation sleeve. DETAILED DESCRIPTION

[0043] The application will be further described in conjunction with specific embodiments, but the protection scope of the application is not limited to this:

[0044] Device Example 1: A plasma reactor device is a coaxial tube type dielectric barrier discharge plasma reactor used as a reaction device for catalytic methane-water-nitrogen gas cooperative conversion to produce methanol and ammonia under plasma conditions; the specific structure is as follows:

[0045] The stainless steel rod 1 is sleeved in the inner cavity of the quartz tube 2, and the axis lines of the quartz tube 2 and the stainless steel rod 1 coincide; the length of the quartz tube 2 is slightly shorter than the length of the stainless steel rod 1, and both ends of the stainless steel rod 1 are located outside the inner cavity of the quartz tube 2.

[0046] The outer surface of the stainless steel rod 1 and the inner wall of the quartz tube 2 maintain a certain distance, that is, the stainless steel rod 1 and the inner wall of the quartz tube 2 form a channel 4.

[0047] A raw material inlet branch pipe 7 (for gas raw material inlet) and a product outlet branch pipe 8 are respectively arranged on the pipe wall near both ends of the quartz tube 2, and the raw material inlet branch pipe 7 and the product outlet branch pipe 8 are respectively connected with the channel 4; the raw material inlet branch pipe 7 and the product outlet branch pipe 8 are both quartz branch pipes.

[0048] A copper sheet layer 3 is tightly coated on the outer wall of the quartz tube 2 between the raw material inlet branch pipe 7 and the product outlet branch pipe 8, so as to form a copper sheet layer 3, and the outer wall of the quartz tube 2 and the inner surface of the copper sheet layer 3 are as close as possible, that is, the distance between them is ≤0.05 mm. The copper sheet layer 3 forms a discharge area.

[0049] The channel 4 in the quartz tube 2 covered by the copper sheet layer 3 is a catalyst filling area.

[0050] A filler 5 is arranged in the channel 4 (in the catalyst filling area) between the raw material inlet branch pipe 7 and the product outlet branch pipe 8. The filler 5 acts as a catalyst, which improves the discharge effect and catalyzes the reaction.

[0051] A sealing and insulating fastener 6 is arranged at each end of the quartz tube 2, and the sealing and insulating fastener 6 is used for sealing the quartz tube 2 and the stainless steel rod 1 from each other. The sealing and insulating fastener 6 is a sealing and insulating fastener made of polytetrafluoroethylene with a sealing ring, which fixes the quartz tube 2 and the stainless steel rod 1 and insulates them from each other, and ensures the air tightness of the device.

[0052] The high-voltage wire 9 is connected to the stainless steel rod 1 outside the quartz tube 2.

[0053] The quartz sleeve 11 is arranged between the two sealing and insulating fasteners 6, and the quartz tube 2 is sleeved in the quartz sleeve 11. The quartz sleeve 11 is divided into two semicircular tubes along the central axis by a complete quartz tube, and the two ends of the two semicircular tubes are embedded in the grooves of the sealing and insulating fasteners 6 when the quartz sleeve 11 is sleeved, so as to be fixed and embraced into a complete straight tube. The quartz sleeve 11 is respectively provided with branch sleeve one 111 and branch sleeve two 112 corresponding to the raw material inlet branch pipe 7 and the product outlet branch pipe 8, and the branch sleeve one 111 and the branch sleeve two 112 are connected with the inner cavity of the quartz sleeve 11; the raw material inlet branch pipe 7 and the product outlet branch pipe 8 are located in the corresponding branch sleeve one 111 and branch sleeve two 112, and the top of the raw material inlet branch pipe 7 is flush with the top of the branch sleeve one 111, and similarly, the top of the product outlet branch pipe 8 is flush with the top of the branch sleeve two 112. The quartz sleeve 11 is also provided with branch sleeve three 113 connected with the inner cavity of the quartz sleeve 11, and the grounding wire 10 is connected with the copper sheet layer 3 after passing through the branch sleeve three 113.

[0054] Specifically:

[0055] The stainless steel rod 1 is used as a high-voltage electrode, the copper sheet 3 is used as a grounding electrode, and the quartz tube 2 is used as a dielectric material. A plasma high-voltage power supply is used to provide high-voltage alternating current with adjustable frequency and voltage peak value.

[0056] The quartz tube 2 has a wall thickness of 1mm-3mm and an outer diameter of 15-20mm.

[0057] The stainless steel rod 1 has a length of 300mm-600mm and a diameter of 5mm-10mm, and is made of 022Cr17Ni12Mo2 stainless steel.

[0058] The length of the quartz tube 2 is slightly shorter than the length of the stainless steel rod 1, that is, about 10-60mm of each end of the stainless steel rod 1 is exposed outside the quartz tube 2, so as to facilitate the connection of the wire to connect the stainless steel rod 1 with the high-voltage power supply.

[0059] The copper sheet 3 has a thickness of 0.05mm-0.3mm and a wrapping length of 50mm-500mm.

[0060] The plasma high-voltage power supply can generate stable alternating current with a voltage peak value of 0-30kV and a frequency of 1kHz-50kHz. The discharge gap (the distance between the stainless steel rod 1 and the inner wall of the quartz tube 2) is 1.5mm-11mm, that is, the distance of the channel 4 is 1.5mm-11mm, the length of the discharge area is the wrapping length of the copper sheet 3, which is 50mm-500mm, and the catalyst filling area is the discharge area.

[0061] The wall thickness of the quartz sleeve 11 is 1mm-3mm, and the outer diameter is 17-23mm.

[0062] In actual use, the stainless steel rod 1 is used as a high-voltage electrode, the copper sheet 3 is used as a grounding electrode, and the quartz tube 2 is used as a dielectric material. A plasma high-voltage power supply is used to provide high-voltage alternating current with adjustable frequency and voltage peak value. The mixed gas composed of methane and nitrogen in a certain proportion (the proportion of methane is 15%-75%) is preheated to a temperature of 120-150℃, flows through the water storage tank to bubble out water vapor, and the water in the water storage tank is maintained at 70-95℃; the methane-nitrogen and water vapor enter the plasma reactor for catalytic conversion; the outer side of the quartz sleeve 11 and its branch pipes (branch sleeve one 111 and branch sleeve two 112) are insulated and wound with heating wires to maintain the reaction system at 100-180℃.

[0063] Preparation of catalyst example 1, high-entropy alloy catalyst.

[0064] The high-entropy alloy prepared in this scheme contains elements such as iron, nickel, vanadium, niobium, silver, copper, and titanium, and is used for catalyzing the synergistic conversion of methane-water-nitrogen to methanol and ammonia under plasma conditions.

[0065] The main steps are as follows:

[0066] (1) A certain amount of high-purity iron, nickel, vanadium, niobium, silver, copper, and titanium powder is weighed as alloy raw material; the alloy raw material powder is placed in a vacuum arc melting furnace and melted into an alloy ingot under an argon atmosphere; the alloy ingot is repeatedly melted for multiple times to ensure uniform alloy composition;

[0067] The molar ratio of Fe, Ni, V, Nb, Ag, Cu, and Ti is (1-2):(1-2):(1-2):(1-2):(1-2):(1-2):(1-2);

[0068] (2) The alloy ingot is annealed at a predetermined annealing temperature for a certain time, and then naturally cooled.

[0069] (3) The alloy ingot is ground using a high-energy ball mill under an argon atmosphere to prepare alloy powder.

[0070] (4) The alloy powder is screened and etched using a specific concentration of nitric acid as an etching liquid (to increase the surface roughness of the alloy powder); after complete washing and drying, high-entropy alloy powder is obtained.

[0071] The high-entropy alloy material is represented as Fe t Ni u V v Nb w Ag x Cu yTi z wherein t, u, v, w, x, y, z are the molar ratios of Fe, Ni, V, Nb, Ag, Cu, Ti elements respectively; and the molar ratio of the substance is t:u:v:w:x:y:z=(1-2):(1-2):(1-2):(1-2):(1-2):(1-2):(1-2).

[0072] In the step (1), the purity of the high-purity metal powder as the base raw material should be greater than 99.9%;

[0073] In the step (1), the alloy ingot smelting times are 2-10 times;

[0074] In the step (2), the annealing temperature is 1000-1500K, and the annealing time is 1-4h;

[0075] Note: K=℃+273.15.

[0076] In the step (4), the screened particle size is 20-100μm;

[0077] In the step (4), the concentration of the nitric acid solution is 0.1-2mol / L; and the operation time of the dealloying is 12-48h.

[0078] Example 1: A method for catalyzing the collaborative conversion of methane-nitrogen-water to produce methanol and ammonia under plasma conditions

[0079] I. Using the device described in device example 1:

[0080] The stainless steel rod 1 is 300mm long and 8mm in diameter; the inner diameter of the quartz tube 2 is 12mm, the wall thickness of the quartz tube 2 is 2mm, and the length of the quartz tube 2 is 200mm; thus the width of the channel 4 is 2mm; that is, the distance between the stainless steel rod 1 and the quartz tube 2 is 2mm; the thickness of the copper sheet 3 is 0.05mm, and the cladding length is 50mm; the wall thickness of the quartz sleeve 11 is 2mm, and the outer diameter is 21mm.

[0081] II. The high-entropy alloy catalyst is prepared according to the method described in catalyst example 1, and FeNiVNbAgCuTi (i.e., t, u, v, w, x, y, z=1) is set:

[0082] The following steps are performed in sequence:

[0083] 1) High-purity iron, nickel, vanadium, niobium, silver, copper, and titanium powders (all with a purity greater than 99.95%) are mixed in an equimolar ratio, i.e., weighed according to the same atomic proportion, a total of 30g, and then placed into a vacuum arc melting furnace to be smelted into an alloy ingot under an argon atmosphere; naturally cooled, and the alloy ingot is repeatedly smelted 5 times;

[0084] 2) annealing at 1373K for 2h, natural cooling to room temperature; then under argon atmosphere, grinding and high-energy ball milling, screening the particle size between 30-60μm; then soaking in 1mol / L nitric acid for 24h, washing thoroughly (water washing until the eluent is neutral) and drying (120-150℃ drying to constant weight) to obtain the desired high-entropy alloy catalyst.

[0085] FeNiVNbAgCuTi(t, u, v, w, x, y, z = 1) high-entropy alloy catalyst was obtained.

[0086] III. Reaction:

[0087] During the reaction, the reactor was assembled and the catalyst (high-entropy alloy catalyst) was filled into the discharge area. Nitrogen was continuously introduced into the channel 4 through the raw material inlet branch 7 for 30min, so that the air in the channel 4 was discharged through the product outlet branch 8 (so as to discharge the air in the reactor).

[0088] The water temperature in the constant-temperature water tank was controlled at 90℃;

[0089] Then, methane and nitrogen were mixed in a volume ratio of 3:1 to form a mixed gas, which was preheated to 130℃, and then introduced into the water (90℃) in the constant-temperature water tank at a flow rate of 100mL / min, so as to bubble and carry out water vapor; the mixed gas of methane and nitrogen together with water vapor as the reaction raw gas was introduced into the channel 4 through the raw material inlet branch 7, and the quartz sleeve 11 and its branch were heated to 120℃ by the heating wire and kept constant; the high-voltage power supply provided by the high-voltage lead 9 was an alternating current with a frequency of 9kHz and a peak voltage of 12kV, which generated plasma and catalyzed the reaction.

[0090] The residence time of the reaction raw gas (i.e. methane, nitrogen and water vapor) in the channel 4 was 0.03min;

[0091] The main reaction formula is:

[0092] 3CH4+N2+3H2O→3CH3OH+2NH3

[0093] The reaction gas was discharged from the product outlet branch 8. After condensation and gas-liquid separation, gas chromatography-mass spectrometry was used for detection.

[0094] Note: The reaction gas contains methanol and ammonia as products, unreacted methane, nitrogen and water vapor, and by-products produced during the reaction. After condensation and gas-liquid separation, methanol and part of the water are condensed into liquid. Then gas chromatography-mass spectrometry is used for detection of the liquid and gas obtained by condensation and gas-liquid separation.

[0095] For the gas obtained by gas-liquid separation, the concentration of ammonia is detected, and the residual amount of methane is detected, so as to obtain the methane conversion rate.

[0096]

[0097] For the liquid obtained by gas-liquid separation, the amount of methanol is detected, so as to obtain the methanol selectivity.

[0098]

[0099] Example 2 series:

[0100] Compared with Example 1, the proportion of iron in the alloy is changed, that is, t is changed, and other operations are equivalent to those of Example 1, to obtain the Example 2 series. The comparison of process parameters and reaction results with Example 1 is shown in Table 1.

[0101] Table 1

[0102]

[0103]

[0104] Example 3 series:

[0105] Compared with Example 1, the proportion of nickel in the alloy is changed, that is, u is changed, and other operations are equivalent to those of Example 1, to obtain the Example 3 series. The comparison of process parameters and reaction results with Example 1 is shown in Table 2.

[0106] Table 2

[0107]

[0108] Example 4 series:

[0109] Compared with Example 1, the proportion of vanadium in the alloy is changed, that is, v is changed, and other operations are equivalent to those of Example 1, to obtain the Example 4 series. The comparison of process parameters and reaction results with Example 1 is shown in Table 3.

[0110] Table 3

[0111]

[0112] Example 5 series:

[0113] Compared with Example 1, the proportion of niobium in the alloy is changed, that is, w is changed, and other operations are equivalent to those of Example 1, to obtain the Example 5 series. The comparison of process parameters and reaction results with Example 1 is shown in Table 4.

[0114] Table 4

[0115]

[0116] Example 6 series:

[0117] In comparison with Example 1, the proportion of silver in the alloy, i.e. the change of x, is changed, and other operations are equivalent to Example 1 to obtain Example 6 series. The process parameters and reaction results are compared with those of Example 1, and see Table 5.

[0118] Table 5

[0119]

[0120] Example 7 series:

[0121] In comparison with Example 1, the proportion of copper in the alloy, i.e. the change of y, is changed, and other operations are equivalent to Example 1 to obtain Example 7 series. The process parameters and reaction results are compared with those of Example 1, and see Table 6.

[0122] Table 6

[0123]

[0124]

[0125] Example 8 series:

[0126] In comparison with Example 1, the proportion of titanium in the alloy, i.e. the change of z, is changed, and other operations are equivalent to Example 1 to obtain Example 8 series. The process parameters and reaction results are compared with those of Example 1, and see Table 7.

[0127] Table 7

[0128]

[0129] Example 9 series:

[0130] In comparison with Example 1, the annealing temperature is changed, and other operations are equivalent to Example 1 to obtain Example 9 series. The process parameters and reaction results are compared with those of Example 1, and see Table 8.

[0131] Table 8

[0132]

[0133] Example 10 series:

[0134] In comparison with Example 1, the number of melting is changed, and other operations are equivalent to Example 1 to obtain Example 10 series. The process parameters and reaction results are compared with those of Example 1, and see Table 9.

[0135] Table 9

[0136]

[0137] Example 11 series:

[0138] Compared with Example 1, the concentration of nitric acid was changed, and other operations were equivalent to those of Example 1 to obtain Example 11 series. The process parameters and reaction results compared with those of Example 1 are shown in Table 10.

[0139] Table 10

[0140]

[0141] Example 12 series:

[0142] Compared with Example 1, the volume ratio of methane and nitrogen was changed, and the flow rate of the mixed gas was kept unchanged; and other operations were equivalent to those of Example 1 to obtain Example 12. The process parameters and reaction results compared with those of Example 1 are shown in Table 11.

[0143] Table 11

[0144]

[0145] Example 13 series:

[0146] Compared with Example 1, the peak-to-peak voltage (2 times of the peak voltage) was changed, and other operations were equivalent to those of Example 1 to obtain Example 13. The process parameters and reaction results compared with those of Example 1 are shown in Table 12.

[0147] Table 12

[0148]

[0149] Example 14 series:

[0150] Compared with Example 1, the flow rate of the methane-argon mixed gas was changed, so as to change the residence time of the reaction raw gas in the channel 4 correspondingly, and other operations were equivalent to those of Example 1 to obtain Example 14. The process parameters and reaction results compared with those of Example 1 are shown in Table 13.

[0151] Table 13

[0152]

[0153] Example 15 series:

[0154] Compared with Example 1, the reactor temperature was changed, and other operations were equivalent to those of Example 1 to obtain Example 15. The process parameters and reaction results compared with those of Example 1 are shown in Table 14.

[0155] Table 14

[0156]

[0157]

[0158] Comparative Example 1-1, change t in Example 1 to 0, and the rest is the same as Example 1.

[0159] The results obtained are shown in Table 15 below.

[0160] Comparative Example 1-2, change u in Example 1 to 0, and the rest is the same as Example 1.

[0161] The results obtained are shown in Table 15 below.

[0162] Comparative Example 1-3, change v in Example 1 to 0, and the rest is the same as Example 1.

[0163] The results obtained are shown in Table 15 below.

[0164] Comparative Example 1-4, change w in Example 1 to 0, and the rest is the same as Example 1.

[0165] The results obtained are shown in Table 15 below.

[0166] Comparative Example 1-5, change x in Example 1 to 0, and the rest is the same as Example 1.

[0167] The results obtained are shown in Table 15 below.

[0168] Comparative Example 1-6, change y in Example 1 to 0, and the rest is the same as Example 1.

[0169] The results obtained are shown in Table 15 below.

[0170] Comparative Example 1-7, change z in Example 1 to 0, and the rest is the same as Example 1.

[0171] The results obtained are shown in Table 15 below.

[0172] Comparative Example 2, change the number of melting in Example 1 to 1, and the rest is the same as Example 1.

[0173] The results obtained are shown in Table 15 below.

[0174] Comparative Example 3, cancel the annealing treatment in Example 1, and the rest is the same as Example 1.

[0175] The results obtained are shown in Table 15 below.

[0176] Comparative Example 4-1, change the catalyst in Example 1 to quartz sand, and the rest is the same as Example 1.

[0177] The results obtained are shown in Table 15 below.

[0178] Comparative Example 4-2, change the catalyst in Example 1 to none, and the rest is the same as Example 1.

[0179] The results obtained are shown in Table 15 below.

[0180] Comparative Example 5-1: The AC power input in Example 1 was changed to none, and the rest was the same as Example 1. Since there was no high voltage electricity, there was no plasma, and thus the reaction could not be carried out.

[0181] The results obtained are shown in Table 15 below.

[0182] Comparative Example 5-2: The AC power input in Example 1 was changed to none, and the heating temperature was changed to 300°C, and the rest was the same as Example 1; the reaction could not be carried out. This comparative example 5-2 shows that since there was no high voltage electricity, there was no plasma, and even if the reaction temperature was raised to 300°C, the reaction could not be carried out. However, the plasma of the present application can efficiently carry out gas conversion at low temperature.

[0183] Table 15

[0184] Comparative Example Methane conversion (%) Methanol selectivity (%) Comparative Example 1-1 66 71 Comparative Example 1-2 73 76 Comparative Example 1-3 75 77 Comparative Example 1-4 72 75 Comparative Example 1-5 72 74 Comparative Example 1-6 69 71 Comparative Example 1-7 68 72 Comparative Example 2 56 49 Comparative Example 3 53 46 Comparative Example 4-1 41 36 Comparative Example 4-2 20 14 Comparative Example 5-1 0 0 Comparative Example 5-2 0 0

[0185] Finally, it should be noted that the above only lists several specific embodiments of the present application. Obviously, the present application is not limited to the above embodiments, and there can be many variations. All variations that can be directly derived or inferred from the disclosure of the present application by those of ordinary skill in the art should be considered within the scope of the present application.

Claims

1. A method for preparing a high-entropy alloy catalyst, characterized by It comprises the following steps: 1) mix powdery iron, nickel, vanadium, niobium, silver, copper and titanium according to the molar ratio of (1~2):(1~2):(1~2):(1~2):(1~2):(1~2):(1~2) as alloy raw material powder; melt the alloy raw material powder into alloy ingot under inert gas atmosphere; 2) anneal the alloy ingot, and then cool it naturally to obtain the alloy ingot after annealing treatment; the annealing temperature is 1000~1500K, and the annealing time is 1~4h; 3) grind the alloy ingot after annealing treatment under inert gas atmosphere to obtain alloy powder; 4) treat the alloy powder with nitric acid solution as etching solution, and then wash and dry to obtain high-entropy alloy powder.

2. The preparation method of the high-entropy alloy catalyst according to claim 1, characterized in that: in step 1), the alloy ingot is repeatedly melted for multiple times to ensure uniform composition; the number of melting times is 2~10.

3. The preparation method of the high-entropy alloy catalyst according to claim 1 or 2, characterized in that: the purity of iron, nickel, vanadium, niobium, silver, copper and titanium is all ≥99.9%.

4. The preparation method of the high-entropy alloy catalyst according to claim 3, characterized in that: in step 3), the particle size of the obtained alloy powder after grinding is 20~100μm.

5. The preparation method of the high-entropy alloy catalyst according to claim 4, characterized in that: in step 4), the concentration of the nitric acid solution is 0.1~2mol / L; and the treatment time is 12~48h.

6. A process for the catalytic methane-nitrogen-water co-conversion to methanol and ammonia under plasma conditions, characterized in that: The high-entropy alloy catalyst prepared by any one of the methods of claims 1~5, and a plasma reactor device; The plasma reactor device comprises a stainless steel rod (1) as a high-voltage electrode, a copper sheet as a grounding electrode, and a quartz tube (2) as a dielectric material. The stainless steel rod (1) is sleeved in the inner cavity of the quartz tube (2), and the axis lines of the stainless steel rod (1) and the quartz tube (2) coincide. The outer surface of the stainless steel rod (1) and the inner wall of the quartz tube (2) maintain a certain distance, thereby forming a channel (4). The raw material inlet branch pipe (7) and the product outlet branch pipe (8) are respectively arranged on the tube wall of the quartz tube (2) and are connected with the channel (4). The copper sheet is coated on the outer wall of the quartz tube (2) between the raw material inlet branch pipe (7) and the product outlet branch pipe (8), thereby forming a copper sheet layer (3), which is a discharge area. The channel (4) in the quartz tube (2) covered by the copper sheet layer (3) is a catalyst filling area. The plasma high-voltage power supply is connected with the stainless steel rod (1) through a high-voltage lead (9), and the grounding lead (10) is connected with the copper sheet layer (3). The filler (5) is arranged in the channel (4) between the raw material inlet branch pipe (7) and the product outlet branch pipe (8), and the filler (5) is a high-entropy alloy catalyst. The method for co-conversion of methanol and ammonia comprises the following steps: Before the reaction, the air in the channel (4) is removed by nitrogen; and the water temperature in the constant-temperature water tank is controlled at 70~95℃. The methane and nitrogen are mixed to form a mixed gas, and the volume content of the methane in the mixed gas is 15% to 75%; the mixed gas is preheated to 120 to 150 DEG C first, and then is passed into water in a constant-temperature water tank at a set flow rate to bubble and carry out water vapor; the mixed gas together with the water vapor is taken as a reaction raw material gas and is passed into the passage (4) through the raw material inlet branch pipe (7), and the temperature in the passage (4) is controlled to be 100 to 180 DEG C; The ion plasma high-voltage power supply generates stable alternating current with a voltage peak value of 0 to 30 kV and a frequency of 1 kHz to 50 kHz, high-voltage discharge is generated on the reaction raw material gas to generate plasma, and catalytic reaction is carried out under the action of the high-entropy alloy catalyst; The reaction obtained gas is discharged from the product outlet branch pipe (8); the reaction obtained gas contains methanol and ammonia.

7. The process for catalytic methane-nitrogen-water co-conversion to methanol and ammonia under plasmonic conditions according to claim 6, characterized by: The reaction obtained gas discharged from the product outlet branch pipe (8) is subjected to gas-liquid separation through condensation, so that the methanol and ammonia are separated.

8. The method according to claim 6 or 7, characterized in that: The flow rate of the mixed gas is 100 to 180 mL / min; The residence time of the reaction raw material gas in the passage (4) is 0.01 to 0.03 minutes.

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