Method for preparing methanol and hydrogen by catalyzing synergistic conversion of methane and water under plasma condition

Abstract

The invention relates to the technical field of plasma catalysis, in particular to a method for preparing methanol and hydrogen by catalyzing synergistic conversion of methane and water under a plasma condition, a used device and a used catalyst. The bubbling-fluidizing plasma reactor is formed by serially connecting and combining a bubbling type corona discharge plasma reactor positioned at the lower part and a fluidized bed dielectric barrier discharge reactor positioned at the upper part through a connecting channel, and the discharge channel is filled with a catalyst. Methane and argon are mixed and preheated and then enter a gas bubbling column from a raw material inlet, the bubbling tip generates corona discharge in bubbles to form plasmas, and methane-water is subjected to preliminary synergistic conversion; the gas subjected to preliminary synergistic conversion enters a discharge channel, and reacts under the action of a catalyst to obtain hydrogen and methanol through conversion.

Description

Technical Field

[0001] The invention relates to the field of plasma catalysis technology, and in particular to a method for catalyzing the coordinated conversion of methane and water to produce methanol and hydrogen under plasma conditions, and a device and a catalyst used therein. Background Art

[0002] At present, with the advancement of technology, the sources of natural gas are becoming more and more extensive, the mining costs of shale gas, combustible ice, etc. are becoming increasingly reduced, and related applications are becoming increasingly abundant. Therefore, the status of methane in the energy structure and chemical industry is increasing. However, since the CH bond of methane is very stable and the dissociation energy is as high as 435kJ / mol. This poses a challenge to the activation and conversion of methane, which usually requires harsh conditions such as high temperature, superacid or free radicals. For this reason, catalytic directional conversion of methane under mild conditions, especially with methanol as the target product, is called the Holy Grail reaction. Due to the harsh conditions required for methane conversion and the protection of methanol from excessive oxidation, the reaction currently adopts a two-step process. The route that has been adopted in industry is the synthesis gas process, that is, firstly preparing synthesis gas by steam reforming of methane, and then synthesizing methanol by the Fischer-Tropsch process. Among them, the steam reforming process of methane has thermodynamic obstacles and consumes huge energy.

[0003] At present, there are two methods for methane steam reforming reaction with methane and water as raw materials: high-temperature thermal catalysis and plasma catalysis, and the products are mostly hydrogen and carbon monoxide. Summary of the invention

[0004] The technical problem to be solved by the present invention is a method for catalyzing the coordinated conversion of methane and water to produce methanol and hydrogen under plasma conditions, as well as the device and catalyst used.

[0005] In order to solve the above problems, the present invention provides a method for preparing a graphene-supported copper-silver-niobium nanoalloy catalyst, which is characterized by comprising the following steps:

[0006] 1) dispersing graphene oxide in deionized water (and ultrasonically treating) to obtain a graphene oxide dispersion (uniformly dispersed graphene oxide dispersion);

[0007] Dissolving a metal precursor in a graphene oxide dispersion, adding urea (excess urea) and stirring (and ultrasonic treatment) to form a mixed system;

[0008] The metal precursor is composed of a copper precursor, a silver precursor, and a niobium precursor; the molar ratio of Cu:Ag:Nb=(1-2):(1-2):(1-2);

[0009] 1.5-2.5 g of graphene oxide and 5-7 g of urea are used for every 3 mmol of metal atoms, wherein the metal atoms are composed of Cu, Ag and Nb;

[0010] 2) Transfer the mixed system to an autoclave (autoclave with polytetrafluoroethylene lining) for aging reaction; the reaction temperature is 100-180° C. (160-180° C.); the reaction time is 12-48 hours;

[0011] 3) subjecting the product obtained in step 2) to solid-liquid separation (centrifugation or suction filtration), and washing and drying the obtained solid;

[0012] Note: Wash with deionized water and transfer to an oven to dry;

[0013] 4) placing the product obtained in step 3) in a muffle furnace and calcining in an air atmosphere; cooling naturally after calcination;

[0014] The calcination temperature is 300-800°C and the calcination time is 1-12h;

[0015] 5) placing the product obtained in step 4) in a tubular furnace and calcining it in a reducing gas atmosphere, and cooling it naturally after the calcination to obtain a graphene-supported nano-alloy catalyst;

[0016] The calcination temperature is 300-800°C, and the calcination time is 1-12h.

[0017] Note: The particle size of the graphene-supported nano-alloy catalyst is 10 to 100 nm.

[0018] As an improvement of the preparation method of the graphene-supported copper-silver-niobium nanoalloy catalyst of the present invention:

[0019] In the step 1), the copper precursor is copper nitrate, the silver precursor is silver nitrate, and the niobium precursor is ammonium niobium oxalate.

[0020] As a further improvement of the preparation method of the graphene-supported copper-silver-niobium nanoalloy catalyst of the present invention:

[0021] In the step 1), the stirring temperature is 10 to 60°C; the stirring time is 12 to 48 hours; and the ultrasonic treatment time is 1 to 8 hours;

[0022] In the step 3), washing with deionized water (washing times are 3 to 6 times); drying temperature is 50 to 120° C.; drying time is 12 to 48 hours;

[0023] The heating rate of step 2) is 3 to 10°C / min, the heating rate of step 4) is 3 to 10°C / min, and the heating rate of step 5) is 3 to 10°C / min.

[0024] As a further improvement of the preparation method of the graphene-supported copper-silver-niobium nanoalloy catalyst of the present invention: in the step 5), the reducing gas atmosphere is a mixed gas of any of the following:

[0025] The volume percentage content of hydrogen in the mixed gas of argon and hydrogen, the mixed gas of nitrogen and hydrogen, and the mixed gas of helium and hydrogen is 1% to 10% (preferably 5 to 10%).

[0026] The present invention also provides a bubbling-fluidized plasma reactor: a bubbling corona discharge plasma reactor located below and a fluidized bed dielectric barrier discharge reactor located above are connected in series through a connecting channel;

[0027] The shell of the bubbling corona discharge plasma reactor is composed of a cylindrical lower shell with a bottom surface, a tapered upper bundle tube of the lower shell, and a tapered lower bundle tube of the lower shell. The tapered upper bundle tube of the lower shell and the tapered lower bundle tube of the lower shell are respectively arranged at the upper and lower ends of the cylindrical lower shell; a gas bubbling column is arranged in the cylindrical lower shell; the gas bubbling column is a cylindrical hollow gas channel with a top but no bottom, a through hole is arranged on the tube wall of the gas channel, a tapered bubbling tip shell is matched and arranged at the through hole, the tapered bubbling tip shell has no bottom surface, and a small through hole is arranged at the top of the tapered bubbling tip shell; the bottom of the gas bubbling column is sealed through the bottom surface of the cylindrical lower shell and is connected with the tapered lower bundle tube of the lower shell; water is filled in the cylindrical lower shell;

[0028] The shell of the fluidized bed dielectric barrier discharge reactor is composed of a cylindrical upper shell, an upper shell conical upper bundle tube and an upper shell conical lower bundle tube; the upper shell conical upper bundle tube and the upper shell conical lower bundle tube are respectively arranged at the upper and lower ends of the cylindrical upper shell; a stainless steel rod is sleeved in the cylindrical upper shell, and the axis of the cylindrical upper shell coincides with the axis of the stainless steel rod; a quartz tube is tightly sleeved on the outer wall of the stainless steel rod, and the inner wall of the cylindrical shell and the outer wall of the quartz tube form a discharge channel, and a catalyst is arranged in the discharge channel as a filler (the discharge area serves as a catalyst filling area and a gas channel);

[0029] The conical upper bundle tube of the upper shell is connected to the product outlet; the conical lower bundle tube of the upper shell is connected to the conical upper bundle tube of the lower shell through a connecting channel; the conical lower bundle tube of the lower shell is connected to the raw material inlet;

[0030] The high-voltage wire is electrically connected to any one of the shell of the bubbling corona discharge plasma reactor, the shell of the fluidized bed dielectric barrier discharge reactor, and the connecting channel;

[0031] The grounding wire is electrically connected to the stainless steel rod.

[0032] As an improvement of the bubbling-fluidized plasma reactor of the present invention:

[0033] The height of the cylindrical upper shell is the same as the length of the stainless steel rod;

[0034] The shell of the bubbling corona discharge plasma reactor, the shell of the fluidized bed dielectric barrier discharge reactor, and the connecting channel are all made of metal (such as stainless steel).

[0035] As a further improvement of the bubbling-fluidized plasma reactor of the present invention:

[0036] The gas enters the conical lower bundle tube of the lower shell from the raw material inlet, and then enters the gas channel of the bubbling column from bottom to top and is discharged through the top small through hole of the conical bubbling tip shell.

[0037] That is, the top small through hole is connected with the inner cavity (gas channel) of the gas bubbling column through the conical inner cavity of the conical bubbling tip shell and the corresponding through holes arranged on the wall of the gas channel of the gas bubbling column in sequence.

[0038] As a further improvement of the bubbling-fluidized plasma reactor of the present invention:

[0039] On the tube wall of the gas channel of the gas bubbling column, four through holes are evenly arranged on the same horizontal plane. Therefore, four rows of conical bubbling tip shell assemblies are evenly and symmetrically arranged longitudinally on the surface of the gas bubbling column, and each row of conical bubbling tip shell assemblies consists of conical bubbling tip shells arranged from top to bottom.

[0040] The present invention also provides a method for catalyzing the coordinated conversion of methane and water to produce methanol and hydrogen under plasma conditions: using the graphene-supported copper-silver-niobium nanoalloy catalyst prepared by any of the above methods, and using the above bubbling-fluidized plasma reactor;

[0041] The discharge channel is filled with a catalyst, and the air in the reactor is exhausted by introducing nitrogen from the raw material inlet; the cylindrical lower shell is filled with water, and the liquid level is substantially flush with the top of the cylindrical lower shell;

[0042] Methane and argon are mixed in a volume ratio of 1:9, and after being preheated (preheated to 120-140°C), they enter the gas bubbling column from the raw material inlet through the conical lower beam tube of the lower shell, and then are discharged from the top small through hole of the conical bubbler tip shell to generate bubbles; the bubbler tip generates corona discharge in the bubble to form plasma, so that methane-water is initially converted synergistically;

[0043] The gas after the initial synergistic conversion passes through the conical upper bundle tube of the lower shell, the connecting channel, the conical lower bundle tube of the upper shell in sequence, and then enters the discharge channel in the cylindrical upper shell, and reacts under the action of the catalyst to convert into hydrogen and methanol;

[0044] The voltage peak is 12-18 kV;

[0045] The time that the mixed gas composed of methane and argon stays in the gas bubbling column is about 0.05 to 0.1 minutes;

[0046] The gas after the initial synergistic conversion stays in the discharge channel for about 2 to 4 minutes;

[0047] Reaction temperature 100~180℃;

[0048] The flow rate of the methane-argon mixed gas is 100-180 mL / min, and the input frequency of the high-voltage power supply is 9 kHz.

[0049] The present invention provides a method for catalyzing the synergistic conversion of methane and water under plasma conditions in combination with a graphene-supported copper-silver-niobium nano-alloy catalyst to directly produce methanol and hydrogen, thereby realizing the comprehensive utilization of methane under mild conditions, that is, efficiently catalyzing the synergistic conversion of methane and water to produce methanol and hydrogen with high selectivity. The present invention enables methane and water vapor to be directly converted into methanol and co-produce hydrogen under mild conditions, which not only shortens the process route, but also reduces the reaction conditions and saves energy, and is a feasible and ideal method.

[0050] The present invention has the following beneficial effects:

[0051] 1. Developed a method to directly synthesize methanol and hydrogen using methane and water as raw materials, realizing the direct conversion of methane into high-value chemicals.

[0052] 2. The proposed catalyst has high activity and selectivity for the target product, and has good life and stability. The proposed plasma reaction device can continuously carry out plasma catalytic reaction at a constant temperature.

[0053] 3. Plasma inputs high-quality energy into the reaction, allowing methane to be converted under mild conditions, avoiding high temperature conditions.

[0054] In summary, the present invention has developed a reaction system that combines a nano-alloy catalyst under plasma conditions to efficiently catalyze the synergistic conversion of methane and water to produce methanol and hydrogen under mild conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings.

[0056] Figure 1 Schematic diagram of the plasma reactor device used in the present invention.

[0057] Figure 2 for Figure 1 Enlarged schematic diagram of the AA section. DETAILED DESCRIPTION

[0058] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0059] Device example, a bubbling-fluidized plasma reactor, as a reaction device for catalyzing the synergistic conversion of methane and water to produce methanol and hydrogen under plasma conditions; the specific structure is as follows:

[0060] The bubbling-fluidized plasma reactor is formed by connecting a bubbling corona discharge plasma reactor 12 located at the bottom and a fluidized bed dielectric barrier discharge reactor 11 located at the top in series via a connecting channel 10 .

[0061] The shell of the bubbling corona discharge plasma reactor 12 is composed of a cylindrical lower shell 121 with a bottom surface, a lower shell conical upper beam tube 122 and a lower shell conical lower beam tube 123, that is, the cylindrical lower shell 121 is provided with a bottom surface, and the lower shell conical upper beam tube 122 and the lower shell conical lower beam tube 123 are respectively arranged at the upper and lower ends of the cylindrical lower shell 121; the cylindrical lower shell 121, the lower shell conical upper beam tube 122 and the lower shell conical lower beam tube 123 are all made of stainless steel.

[0062] A number of gas bubbling columns 3 are evenly distributed in the cylindrical lower shell 121. The gas bubbling columns 3 are in contact with the cylindrical lower shell 121 and connected to a high-voltage power supply. Each gas bubbling column 3 is a cylindrical, hollow gas channel with a top but no bottom (i.e., a cylindrical gas channel). The bottom of the gas bubbling column 3 is sealed through the bottom surface of the cylindrical lower shell 121 and is connected to the conical lower bundle tube 123 of the lower shell. Water is filled in the cylindrical lower shell 121. The liquid level in the cylindrical lower shell 121 is substantially flush with the top of the cylindrical lower shell 121. A corresponding water inlet switch may be provided at the top of the cylindrical lower shell 121 for adding water during the reaction. For the clarity of the drawing, this water adding switch is located at Figure 1 Omitted in the.

[0063] A through hole is provided on the tube wall of the gas channel. On the same horizontal plane, 4 through holes are evenly provided, that is, the angle between two adjacent through holes is 90°; the through hole is connected to the inner cavity of the gas channel. A conical bubbling tip shell 2 is provided at each through hole. The conical bubbling tip shell 2 has no bottom surface. A top small through hole is provided at the top of the conical bubbling tip shell 2. The top small through hole is connected to the inner cavity (gas channel) of the gas bubbling column 3 through the conical inner cavity of the conical bubbling tip shell 2 and the corresponding through holes provided on the tube wall of the gas channel in sequence. The bottom end of the conical bubbling tip shell 2 can be sealed and fixedly connected to the gas bubbling column 3 in the form of conventional welding. Therefore, the surface of the gas bubbling column 3 is evenly and symmetrically longitudinally provided with 4 rows of conical bubbling tip shell assemblies, and each row of conical bubbling tip shell assemblies is composed of conical bubbling tip shells 2 arranged from top to bottom.

[0064] The shell of the fluidized bed dielectric barrier discharge reactor 11 is composed of a cylindrical upper shell 111, an upper shell conical upper bundle tube 112 and an upper shell conical lower bundle tube 113; the upper shell conical upper bundle tube 112 and the upper shell conical lower bundle tube 113 are respectively arranged at the upper and lower ends of the cylindrical upper shell 111, and a stainless steel rod 5 is inserted into the cylindrical upper shell 111, and the axis of the cylindrical upper shell 111 coincides with the axis of the stainless steel rod 5; the height of the cylindrical upper shell 111 is the same as the length of the stainless steel rod 5, that is, the two are flush in the horizontal direction. The cylindrical upper shell 111, the upper shell conical upper bundle tube 112 and the upper shell conical lower bundle tube 113 are all made of stainless steel.

[0065] A quartz tube 6 made of quartz medium is tightly sleeved on the outer wall of the stainless steel rod 5, and the inner wall of the quartz tube 6 fits the outer surface of the stainless steel rod 5 as closely as possible, that is, the distance between the two is ≤0.05mm.

[0066] The inner wall of the cylindrical upper shell 111 maintains a certain distance from the outer wall of the quartz tube 6, that is, the inner wall of the cylindrical shell 111 and the outer wall of the quartz tube 6 form a discharge channel 7, and a catalyst filler is arranged in the discharge channel 7. The function of the catalyst filler is to improve the discharge effect and catalyze the reaction.

[0067] The upper shell conical upper bundle pipe 112 is connected to the product outlet 13 ; the upper shell conical lower bundle pipe 113 is connected to the lower shell conical upper bundle pipe 122 through the connecting channel 10 . The lower shell conical lower bundle pipe 123 is connected to the raw material inlet 14 .

[0068] The gas enters the conical lower bundle tube 123 of the lower shell from the raw material inlet 14, and then enters the bubbling column 3 from bottom to top and generates bubbles through the top small through hole of the conical bubbling tip shell 2.

[0069] The high-voltage wire 8 is connected to the device shell, that is, the high-voltage wire 8 is connected to any one of the shell of the bubbling corona discharge plasma reactor 12, the shell of the fluidized bed dielectric barrier discharge reactor 11, and the connecting channel 10. The device shell is connected to a high-voltage power supply through the high-voltage wire 8. Since the gas bubbling column 3 is in contact with the cylindrical lower shell 121, the high-voltage power supply is turned on, and corona discharge is generated in the bubble through the tip at the bubbling port to form plasma, so that methane-water is initially synergistically converted.

[0070] The grounding wire 9 is connected to the stainless steel rod 5 .

[0071] The product outlet 13 is the gas outlet, and the raw material inlet 14 is the gas inlet.

[0072] In actual use:

[0073] The stainless steel shell 1 is used as a high-voltage electrode, the stainless steel rod 5 is used as a grounding electrode, the conical bubble tip shell 2 is used as a corona discharge tip, and the quartz tube 6 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.

[0074] Specific:

[0075] The cylindrical lower shell 121 is 100mm-1000mm long, 30mm-200mm in inner diameter, and made of 022Cr17Ni12Mo2 stainless steel; the cylindrical upper shell 111 is 100mm-1000mm long, 30mm-200mm in inner diameter, and made of 022Cr17Ni12Mo2 stainless steel. The quartz tube 6 has a wall thickness of 1mm-3mm and an outer diameter of 20-100mm.

[0076] The length of the stainless steel rod 5 is equal to the length of the cylindrical lower shell 121; the material of the stainless steel rod 5 is 022Cr17Ni12Mo2 stainless steel.

[0077] The length of the bubbling column 3 = the length of the cylindrical lower shell 121, that is, the bubbling column 3 is 100mm-1000mm long, has an inner diameter of 1mm-3mm, and is made of 022Cr17Ni12Mo2 stainless steel.

[0078] The dimensions of the conical bubbler tip housing 2 are 1-3 mm in diameter at the base and 2-10 mm in height.

[0079] The thickness of the stainless steel casing of the device is 1mm-3mm.

[0080] The plasma high voltage power supply can generate a stable alternating current with a voltage peak of 0-30 kV and a frequency of 1 kHz-50 kHz. The width of the discharge channel 7 is 5 mm-50 mm.

[0081] Example 1: A method for catalyzing the synergistic conversion of methane and water to produce methanol and hydrogen under plasma conditions

[0082] 1. A bubbling-fluidized plasma reactor as described in the device example:

[0083] The cylindrical lower shell 121 is 300 mm long and has an inner diameter of 100 mm; the cylindrical upper shell 111 is 300 mm long and has an inner diameter of 100 mm. The quartz tube 6 has a wall thickness of 2 mm and an outer diameter of 90 mm. The stainless steel rod 5 is 300 mm long and has a diameter of 86 mm. The thickness of the stainless steel shell 1 (cylindrical upper shell 111, upper shell conical upper beam tube 112 and upper shell conical lower beam tube 113, cylindrical lower shell 121, lower shell conical upper beam tube 122 and lower shell conical lower beam tube 123, and connecting channel 10) is 2 mm. The width of the discharge channel 7 is 5 mm. The length of the bubbling column 3 is 300 mm, the inner diameter is 2 mm, the aperture of the through hole on the tube wall of the gas channel of the bubbling column 3 (the bottom diameter of the conical bubbling tip shell 2) is about 1-2 mm, the aperture of the top small through hole of the conical bubbling tip shell 2 is about 0.1-0.2 mm, the height of the conical bubbling tip shell 2 is about 6 mm, and the spacing of the conical bubbling tip shell 2 in each column of the conical bubbling tip shell assembly is about 5-6 mm. On the horizontal plane, the top small through holes of adjacent conical bubbling tip shells 2 are kept at a spacing of about 5-6 mm.

[0084] 2. Preparation of graphene-supported copper-silver-niobium nanoalloy catalyst: Prepare Cu1Ag1Nb1 / graphene catalyst (x=1, y=1, z=1); perform the following steps in sequence:

[0085] 1) Disperse 2 g of graphene oxide in 200 mL of deionized water and treat with ultrasound for 1 h to obtain a uniformly dispersed graphene oxide dispersion;

[0086] 0.13 g copper nitrate (1 mmol), 0.17 g silver nitrate (1 mmol), and 0.2 g ammonium niobium oxalate (1 mmol) were added to the graphene oxide dispersion and dissolved; 6 g urea was then added, stirred at 25° C. for 12 h, and ultrasonically treated for 2 h to form a mixed system;

[0087] 2) Transfer the mixed system to an autoclave with a polytetrafluoroethylene liner, raise the temperature to 160°C at 5°C / min, and react for 24 hours;

[0088] 3) After centrifugal filtration, the obtained solid was washed with deionized water for 3 times (until the pH of the eluent was neutral); transferred to an oven and dried at 110°C for 24 hours;

[0089] Then, the sample was placed in a muffle furnace, heated to 500°C at 5°C / min in an air atmosphere, kept at that temperature for 3 hours, and cooled naturally to room temperature.

[0090] Then, the mixture was placed in a tube furnace, heated to 500°C at 5°C / min in a mixed atmosphere of argon and hydrogen (hydrogen accounts for 5%), kept warm for 3 hours, and cooled naturally to room temperature; a graphene-supported copper-silver-niobium nanoalloy catalyst (hereinafter referred to as catalyst) was obtained, and the particle size of the graphene-supported copper-silver-niobium nanoalloy catalyst was confirmed by scanning electron microscopy. The particle size of the graphene-supported nanoalloy catalyst obtained by the present invention is 10 to 100 nm.

[0091] 3. During the reaction, assemble the reactor, fill the discharge channel 7 with the catalyst, continuously introduce nitrogen from the raw material inlet 14 for 30 minutes, exhaust the air in the reactor (the air is discharged from the reactor from the product outlet 13); and add water into the cylindrical lower shell 121 through the water adding switch, and the liquid level is substantially flush with the top of the cylindrical lower shell 121. Note: The water is located outside the gas bubbling column 3.

[0092] Methane and argon are mixed in a volume ratio of 1:9, with a total flow rate of 100 mL / min, and are preheated to 130° C. and introduced into the reaction device from the raw material inlet 14; the temperature in the entire reaction device is controlled to be 100° C. The high-voltage power supply input frequency is 9 kHz, and the voltage peak is 12 kV AC, which generates plasma and catalyzes the reaction; the products are separated by condensation gas and liquid, and then detected by gas chromatography-mass spectrometry.

[0093] The specific reaction process is:

[0094] The mixed gas composed of methane and argon enters the gas bubbling column 3 from the raw material inlet 14 through the tapered lower bundle tube 123 of the lower shell, and then is discharged from the top small through hole of the tapered bubbling tip shell 2 to generate bubbles. Since the gas bubbling column 3 is in contact with the cylindrical lower shell 121 and is connected to the high-voltage power supply through the high-voltage wire 8, the bubble tip generates corona discharge in the bubble to form plasma, so that the methane-water is initially synergistically converted. The mixed gas stays in the gas bubbling column 3 for about 0.1 minutes. During the reaction, when the water level in the cylindrical lower shell 121 drops by more than 5%, water is added to the cylindrical lower shell 121 through the water adding switch so that the liquid level is basically flush with the top of the cylindrical lower shell 121.

[0095] Then, the gas after the initial synergistic conversion (hydrogen and carbon monoxide as well as unconverted methane and water, etc.) passes through the lower shell conical upper bundle tube 122, the connecting channel 10, and the upper shell conical lower bundle tube 113 in sequence, and then enters the discharge channel 7 in the cylindrical upper shell 111, and further reacts under the action of the catalyst, and further converts to obtain hydrogen and methanol. Explanation: Methane and water undergo steam reforming to obtain synthesis gas, and the synthesis gas obtains methanol and hydrogen.

[0096] The gas after the initial synergistic conversion stays in the discharge channel 7 for about 4 minutes.

[0097] The products generated by the reaction are methanol, hydrogen, etc. (due to the high temperature of the gas flow, it is a gas), which is then condensed and separated, so that the separated liquid is methanol, and pressure swing adsorption is performed to separate hydrogen. This separation method is a conventional technology in this industry, so it will not be elaborated in detail in the present invention.

[0098] Example 2 series:

[0099] Compared with Example 1, the molar amount of copper nitrate was changed to change the proportion of copper in the alloy, that is, x was changed, and the other operations were the same as those in Example 1 to obtain the series of Example 2. The comparison of process parameters and reaction results with those of Example 1 is shown in Table 1.

[0100] Table 1

[0101]

[0102]

[0103] Embodiment 3 series:

[0104] Compared with Example 1, the molar amount of silver nitrate was changed to change the proportion of silver in the alloy, that is, y was changed, and the other operations were the same as those in Example 1 to obtain the series of Example 3. The comparison of process parameters and reaction results with those of Example 1 is shown in Table 2.

[0105] Table 2

[0106]

[0107] Embodiment 4 series:

[0108] Compared with Example 1, the molar amount of ammonium niobium oxalate was changed to change the proportion of niobium in the alloy, that is, z was changed, and the other operations were the same as Example 1 to obtain the series of Example 4. The comparison of process parameters and reaction results with Example 1 is shown in Table 3.

[0109] Table 3

[0110]

[0111]

[0112] Embodiment 5 series:

[0113] Compared with Example 1, the reaction temperature of the autoclave was changed, and other operations were the same as Example 1 to obtain the series of Example 5. The comparison of process parameters and reaction results with Example 1 is shown in Table 4.

[0114] Table 4

[0115]

[0116] Embodiment 6 series:

[0117] Compared with Example 1, the calcination temperature of the muffle furnace was changed, and other operations were the same as Example 1, to obtain the series of Example 6. The comparison of process parameters and reaction results with Example 1 is shown in Table 5.

[0118] Table 5

[0119]

[0120] Embodiment 7 series:

[0121] Compared with Example 1, the calcination temperature in the tubular furnace was changed, and other operations were the same as those in Example 1, thereby obtaining Example 7 series. The comparison of process parameters and reaction results with those in Example 1 is shown in Table 6.

[0122] Table 6

[0123]

[0124]

[0125] Embodiment 8 series:

[0126] Compared with Example 1, the proportion of hydrogen in the reducing gas was changed, and other operations were the same as Example 1, to obtain the series of Example 8. The comparison of process parameters and reaction results with Example 1 is shown in Table 7.

[0127] Table 7

[0128]

[0129] Embodiment 9 series:

[0130] Compared with Example 1, the voltage peak-to-peak value was changed (twice the voltage peak value), and other operations were the same as Example 1, to obtain the series of Example 9. The comparison of process parameters and reaction results with Example 1 is shown in Table 8.

[0131] Table 8

[0132]

[0133] Embodiment 10 series:

[0134] Compared with Example 1, the flow rate of the methane-argon mixed gas was changed to change the residence time, and the other operations were the same as Example 1 to obtain the series of Example 10. The comparison of the process parameters and reaction results with those of Example 1 is shown in Table 9.

[0135] Table 9

[0136]

[0137] Embodiment 11 series:

[0138] Compared with Example 1, the reactor temperature was changed, and other operations were the same as Example 1 to obtain the series of Example 11. The comparison of process parameters and reaction results with Example 1 is shown in Table 10.

[0139] Table 10

[0140]

[0141] Comparative Example 1-1: x in Example 1 is changed to 0, and the rest is the same as Example 1.

[0142] The results are shown in Table 11 below.

[0143] Comparative Example 1-2: Change y in Example 1 to 0, and the rest is the same as Example 1.

[0144] The results are shown in Table 11 below.

[0145] Comparative Example 1-3: Change z in Example 1 to 0, and the rest is the same as Example 1.

[0146] The results are shown in Table 11 below.

[0147] Comparative Example 2-1: The catalyst in Example 1 was replaced with quartz sand, and the rest was the same as Example 1.

[0148] The results are shown in Table 11 below.

[0149] Comparative Example 2-2: The catalyst in Example 1 was changed to none, and the rest was the same as Example 1.

[0150] The results are shown in Table 11 below.

[0151] Comparative Example 3: The AC input in Example 1 is changed to none, and the rest is the same as Example 1. This case cannot be reacted.

[0152] Comparative Example 4: The "initial co-conversion of methane and water" was cancelled, that is, the specific steps were as follows: only the upper part of the reactor was retained, and a mixed gas of methane and water was directly introduced. The rest was referred to Example 1.

[0153] Table 11

[0154] Comparative Example Hydrogen concentration (ppm) Methane conversion rate (%) Methanol selectivity (%) Comparative Example 1-1 12854 63 70 Comparative Example 1-2 11963 61 69 Comparative Examples 1-3 11526 59 64 Comparative Example 2-1 7625 35 21 Comparative Example 2-2 4007 28 12 Comparative Example 3 0 0 0 Comparative Example 4 1675 15 9

[0155] Finally, it should be noted that the above examples are only some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. A method for preparing a graphene-supported copper-silver-niobium nanoalloy catalyst, characterized in that The steps include: 1) dispersing graphene oxide in deionized water to obtain a graphene oxide dispersion; Dissolving a metal precursor in a graphene oxide dispersion, adding urea and stirring to form a mixed system; The metal precursor consists of a copper precursor, a silver precursor, and a niobium precursor; Cu: Ag:Nb=(1-2):(1-2):(1-2) molar ratio; 1.5-2.5 g of graphene oxide and 5-7 g of urea are used for every 3 mmol of metal atoms, wherein the metal atoms are composed of Cu, Ag and Nb; 2) Transfer the mixed system to an autoclave for aging reaction; the reaction temperature is 100-180°C; the reaction time is 12-48h; 3) subjecting the product obtained in step 2) to solid-liquid separation, and washing and drying the obtained solid; 4) placing the product obtained in step 3) in a muffle furnace and calcining in an air atmosphere; cooling naturally after calcination; The calcination temperature is 300-800°C and the calcination time is 1-12h; 5) placing the product obtained in step 4) in a tubular furnace and calcining it in a reducing gas atmosphere, and cooling it naturally after the calcination to obtain a graphene-supported nano-alloy catalyst; The calcination temperature is 300-800°C, and the calcination time is 1-12h.

2. The method for preparing the graphene-supported copper-silver-niobium nanoalloy catalyst according to claim 1, characterized in that: In the step 1), the copper precursor is copper nitrate, the silver precursor is silver nitrate, and the niobium precursor is ammonium niobium oxalate.

3. The method for preparing the graphene-supported copper-silver-niobium nanoalloy catalyst according to claim 2, characterized in that: In the step 1), the stirring temperature is 10 to 60° C. and the stirring time is 12 to 48 hours; In the step 3), washing with deionized water (washing times are 3 to 6 times); drying temperature is 50 to 120° C.; drying time is 12 to 48 hours; The heating rate of step 2) is 3 to 10°C / min, the heating rate of step 4) is 3 to 10°C / min, and the heating rate of step 5) is 3 to 10°C / min.

4. The method for preparing the graphene-supported copper-silver-niobium nanoalloy catalyst according to any one of claims 1 to 3, characterized in that: In the step 5), the reducing gas atmosphere is a mixed gas of any of the following: The mixed gas of argon and hydrogen, the mixed gas of nitrogen and hydrogen, and the mixed gas of helium and hydrogen, the volume percentage content of hydrogen in the above three mixed gases is 1% to 10%.

5. A bubbling-fluidized plasma reactor, characterized in that: It is composed of a bubbling corona discharge plasma reactor (12) located at the bottom and a fluidized bed dielectric barrier discharge reactor (11) located at the top, which are connected in series via a connecting channel (10); The shell of the bubbling corona discharge plasma reactor (12) is composed of a cylindrical lower shell (121) with a bottom surface, a lower shell conical upper bundle tube (122) and a lower shell conical lower bundle tube (123), wherein the lower shell conical upper bundle tube (122) and the lower shell conical lower bundle tube (123) are respectively arranged at the upper and lower ends of the cylindrical lower shell (121); a gas bubbling column (3) is arranged in the cylindrical lower shell (121); the gas The bubbling column (3) is a cylindrical, hollow gas passage with a top but no bottom. A through hole is provided on the tube wall of the gas passage. A conical bubbling tip shell (2) is arranged at the through hole. The conical bubbling tip shell (2) has no bottom surface. A top small through hole is arranged at the top of the conical bubbling tip shell (2). The bottom of the gas bubbling column (3) is sealed through the bottom surface of the cylindrical lower shell (121) and is connected to the conical lower bundle tube (123) of the lower shell. The shell of the fluidized bed dielectric barrier discharge reactor (11) is composed of a cylindrical upper shell (111), an upper shell conical upper bundle tube (112) and an upper shell conical lower bundle tube (113); the upper shell conical upper bundle tube (112) and the upper shell conical lower bundle tube (113) are respectively arranged at the upper and lower ends of the cylindrical upper shell (111); a stainless steel rod (5) is sleeved in the cylindrical upper shell (111), and the axis of the cylindrical upper shell (111) and the stainless steel rod (5) coincide with each other; a quartz tube (6) is tightly sleeved on the outer wall of the stainless steel rod (5), and the inner wall of the cylindrical shell (111) and the outer wall of the quartz tube (6) form a discharge channel (7), and a catalyst is arranged in the discharge channel (7) as a filler; The conical upper bundle tube (112) of the upper shell is connected to the product outlet (13); the conical lower bundle tube (113) of the upper shell is connected to the conical upper bundle tube (122) of the lower shell through the connecting channel (10); the conical lower bundle tube (123) of the lower shell is connected to the raw material inlet (14); The high voltage wire (8) is electrically connected to any one of a shell of a bubbling corona discharge plasma reactor (12), a shell of a fluidized bed dielectric barrier discharge reactor (11), and a connecting channel (10); The grounding wire (9) is electrically connected to the stainless steel rod (5).

6. The bubbling-fluidizing plasma reactor according to claim 5, characterized in that: The height of the cylindrical upper shell (111) is the same as the length of the stainless steel rod (5); The shell of the bubbling corona discharge plasma reactor (12), the shell of the fluidized bed dielectric barrier discharge reactor (11), and the connecting channel (10) are all made of metal.

7. The bubbling-fluidizing plasma reactor according to claim 6, characterized in that: The gas enters the conical lower bundle tube (123) of the lower shell from the raw material inlet (14), then enters the gas channel of the bubbling column (3) from bottom to top and is discharged through the top small through hole of the conical bubbling tip shell (2).

8. A bubbling-fluidizing plasma reactor according to any one of claims 5 to 7, characterized in that: Four through holes are evenly arranged on the same horizontal plane on the wall of the gas channel of the gas bubbling column (3), so that four rows of conical bubbling tip shell assemblies are evenly and symmetrically arranged longitudinally on the surface of the gas bubbling column (3), and each row of conical bubbling tip shell assemblies is composed of conical bubbling tip shells (2) arranged from top to bottom.

9. A method for catalyzing the synergistic conversion of methane and water to produce methanol and hydrogen under plasma conditions, characterized in that: A graphene-supported copper-silver-niobium nanoalloy catalyst prepared by any of the methods of claims 1 to 4, and a bubbling-fluidized plasma reactor according to any of claims 5 to 8; characterized in that: The discharge channel (7) is filled with a catalyst, and the air in the reactor is discharged by introducing nitrogen from the raw material inlet (14); the cylindrical lower shell (121) is filled with water, and the liquid level is substantially flush with the top of the cylindrical lower shell (121); Methane and argon are mixed in a volume ratio of 1:9, and after being preheated (preheated to 120-140° C.), they enter the gas bubbling column (3) from the raw material inlet (14) through the conical lower bundle tube (123) of the lower shell, and then are discharged from the top small through hole of the conical bubbling tip shell (2) to generate bubbles; the bubbling tip generates corona discharge in the bubbles to form plasma, so that methane-water is initially synergistically converted; The gas after the preliminary synergistic conversion passes through the conical upper bundle tube (122) of the lower shell, the connecting channel (10), the conical lower bundle tube (113) of the upper shell in sequence, and then enters the discharge channel (7) in the cylindrical upper shell (111), reacts under the action of the catalyst, and is converted into hydrogen and methanol.

10. The method for preparing methanol and hydrogen by catalytic conversion of methane and water under plasma conditions according to claim 9, characterized in that: The voltage peak is 12-18 kV; The residence time of the mixed gas composed of methane and argon in the gas bubbling column (3) is about 0.05 to 0.1 minutes; The gas after the initial synergistic conversion stays in the discharge channel (7) for about 2 to 4 minutes; Reaction temperature 100~180℃.

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