Method for directly converting carbon-rich natural gas and used catalyst

Abstract

The invention provides a method for directly converting carbon-rich natural gas and a catalyst used in the method, conversion of carbon dioxide and methane in the carbon-rich natural gas is realized at a cathode and an anode by means of electro-catalysis, and co-conversion of the carbon-rich natural gas is realized by regulating and controlling an electrode material and applied voltage. The consumption molar ratio of CO2 / CH4 in the electro-catalytic reaction is 0.08-2.25, and the method can be suitable for all carbon-rich natural gases with the ratio of n (CO2) / n (CH4) being 0.09-1.45. The reaction conditions are mild, and conversion of inert methane and carbon dioxide in all carbon-rich natural gases can be realized under the conditions of normal temperature and normal pressure.

Description

Technical Field

[0001] This invention relates to the field of catalyst synthesis technology, and more specifically to a method for the direct conversion of carbon-rich natural gas and the catalyst used therein. Background Technology

[0002] Carbon-rich natural gas is an unconventional natural gas. Its biggest difference from conventional natural gas is its high carbon dioxide content, exceeding 20% ​​by mass and reaching as high as 90%. my country has abundant proven reserves of carbon-rich natural gas, including fields such as the Subei Oilfield, Shengli Oilfield, North China Oilfield, Dagang Oilfield, and the South China Sea region. The gas fields in the South my country Sea, in particular, exhibit significant carbon dioxide enrichment, with over 90% of the reservoirs containing more than 20% carbon dioxide by mass, and more than half exceeding 50%, with a CO2 / CH4 molar ratio of 0.09-1.45. According to my country's gas quality standards, the carbon dioxide content in commercial natural gas should not exceed 2%. Therefore, carbon-rich natural gas generally needs to be decarbonized before it can be used as conventional natural gas.

[0003] Currently, the main decarbonization processes for carbon-rich natural gas include: physical absorption, which selectively dissolves carbon dioxide by utilizing the difference in solubility between carbon dioxide and methane in certain solutions; chemical absorption, which uses alkaline liquids as absorbents to absorb and remove acidic carbon dioxide; pressure swing adsorption, which uses specific adsorbents to selectively adsorb carbon dioxide; and membrane separation, which relies on the concentration difference between methane and carbon dioxide to drive separation. All of these decarbonization methods are energy-intensive, and the separated carbon dioxide is generally directly released into the atmosphere, exacerbating the greenhouse effect. Therefore, co-converting methane and carbon dioxide from carbon-rich natural gas to produce high-value-added compounds is a more effective conversion method.

[0004] The co-conversion pathways of methane and carbon dioxide can be categorized based on their products into three types: methane-carbon dioxide co-conversion to syngas, methane-carbon dioxide co-conversion to C2 hydrocarbons, and methane-carbon dioxide co-conversion to C2 oxygen-containing compounds. The methane-carbon dioxide co-conversion to syngas was first proposed in 1928 by Fisher and Tropsch (Brennst. Chem. 1928, 3:39-46) and implemented on a Ni-based catalyst. Methane and carbon dioxide act as redox agents for each other, with a CH4 to CO2 conversion ratio of 1:1. The methane-carbon dioxide co-conversion to C2 hydrocarbons, including ethane and ethylene, was first reported in 1995. Asami et al. directly synthesized C2 hydrocarbons at 850℃ using 17 metal oxides as catalysts (Applied Catalysis A: General, 1995, 126:245-255), achieving a C2 hydrocarbon selectivity of up to 30% and a CH4 to CO2 conversion ratio of 1 or 0.5. The main product of the methane-carbon dioxide co-conversion to C2 oxygen-containing compounds is acetic acid. In 1995, Kurioka et al. first synthesized acetic acid under homogeneous conditions using palladium acetate and copper acetate as catalysts (Chem. Lett. 1995, 24:244), with a CH4 to CO2 conversion ratio of 1. However, in the above-mentioned traditional conversion pathways, methane and carbon dioxide act as redox agents for each other, so the methane / carbon dioxide conversion ratio is limited by the stoichiometric ratio and is difficult to apply to all carbon-rich natural gas.

[0005] Due to limitations imposed by the stoichiometric ratio of methane to carbon dioxide, current routes for the co-conversion of carbon-rich natural gas to produce high-value-added compounds still have many shortcomings. Developing a new technological route for the efficient utilization of carbon-rich natural gas is an urgent technical problem to be solved. Summary of the Invention

[0006] To address the problems of existing methods, this invention provides a method for the direct conversion of carbon-rich natural gas. This method utilizes electrocatalysis to convert carbon dioxide and methane in carbon-rich natural gas at the cathode and anode, respectively. The co-conversion of carbon-rich natural gas is achieved by controlling the electrode materials and the applied voltage. The molar ratio of CO2 / CH4 consumed in the electrocatalytic reaction is 0.08-2.25, making it applicable to all carbon-rich natural gas with n(CO2) / n(CH4) = 0.09-1.45.

[0007] The technical solution of the present invention is as follows:

[0008] This invention provides a method for the direct conversion of carbon-rich natural gas. A three-electrode system consisting of a cathode catalyst, an anode catalyst, and a reference electrode is constructed in an electrolytic cell. A mixture of CH4, CO2, and Ar is introduced into the reaction system at room temperature and pressure to carry out the reaction. The active metal of the cathode catalyst includes Cu, and the active metal of the anode catalyst includes Ni. The molar ratio of CO2 to CH4 consumed in the electrocatalytic reaction is 0.08-2.25.

[0009] Furthermore, the flow rate of the CH4, CO2, and Ar mixture is 20-40 mL / min. -1 .

[0010] Furthermore, the electrocatalytic reaction takes 1-2 hours.

[0011] Furthermore, the cathode catalyst is composed of a carbon nitride support and copper particles, wherein the copper particles are uniformly loaded on the sheet-like carbon nitride support, and the loading of the copper particles is approximately 26.46%.

[0012] Furthermore, the copper particles have a particle size of approximately 17.26 nm.

[0013] Furthermore, the cathode catalyst is copper particles supported on carbon nitride with adjustable pyridine nitrogen content. The carbon nitride support contains pyridine nitrogen and pyrrole nitrogen, with pyridine nitrogen accounting for 64%-88% of the mass of the carbon nitride support and pyrrole nitrogen accounting for 12%-36% of the mass of the carbon nitride support.

[0014] Furthermore, the cathode catalyst is any one of Cu / CN-0, Cu / CN-30, and Cu / CN-60.

[0015] Specifically, in the carbon nitride support of Cu / CN-0, the content of pyridine nitrogen is 64 wt% and the content of pyrrole nitrogen is 36 wt%; in the carbon nitride support of Cu / CN-30, the content of pyridine nitrogen is 88 wt% and the content of pyrrole nitrogen is 12 wt%; and in the carbon nitride support of Cu / CN-60, the content of pyridine nitrogen is 75 wt% and the content of pyrrole nitrogen is 25 wt%.

[0016] Furthermore, the anode catalyst is Fe. y Ni 10-y (OH) x , where y is independently 0, 1, 2, 3 or 5, and x is 2-2.74.

[0017] Furthermore, the anode catalyst is Fe1Ni9(OH). x At that time, x = 2.31; the anode catalyst is Fe2Ni8(OH). xAt that time, x = 2.46; the anode catalyst is Fe3Ni7(OH). x At that time, x = 2.69; the anode catalyst is Fe5Ni5(OH). x At time x = 2.74.

[0018] Furthermore, in the anode catalyst, Ni is in the form of Ni 3+ with Ni 2+ The valence state exists for Ni. 3+ / Ni 2+ The surface atomic ratio is 0.31-1.28.

[0019] Furthermore, the cathode catalyst activates carbon dioxide, and the main products obtained include H2, C2H5OH, and CO (selectivity less than 0.1%).

[0020] Furthermore, the anolyte catalyst activates methane, and the main products obtained include O2 and C2H5OH.

[0021] Furthermore, when the cathode catalyst is Cu / CN-0 and the anode catalyst is Fe3Ni7(OH) x When the applied working voltage is -0.40V (vs. RHE (reversible hydrogen electrode)), the molar ratio of CO2 / CH4 consumed in the electrocatalytic reaction is 0.08.

[0022] Furthermore, when the cathode catalyst is Cu / CN-30, the anode catalyst is Ni(OH)2, and the applied operating voltage is -0.40V (vs. RHE), the molar ratio of CO2 / CH4 consumed in the electrocatalytic reaction is 2.25.

[0023] Furthermore, the reference electrode is Hg / HgO.

[0024] Furthermore, in the electrocatalytic reaction, the applied operating voltage is 0.40-0.55V (vs. RHE).

[0025] Furthermore, in the electrocatalytic reaction, the electrolyte used is 0.1M KOH.

[0026] Furthermore, in the electrocatalytic reaction, the electrolytic cell used is an H-type single-chamber electrolytic cell.

[0027] The present invention also provides the aforementioned cathode catalyst, the preparation method of which includes the following steps:

[0028] Step 1): Dissolve urea and copper acetate monohydrate in deionized water and mix evenly. After rotary evaporation to remove water, grind evenly to obtain the precursor.

[0029] Step 2): Weigh the precursor and place it in a tube furnace. Under a nitrogen atmosphere, heat it to 400-500℃ and maintain it for 0-60 minutes. By adjusting the pyrolysis time, copper particles loaded with carbon nitride with adjustable pyridine nitrogen content are obtained, which is Cu / CN-t (t is the pyrolysis time).

[0030] Further, in step 1), the mass ratio of copper acetate monohydrate to urea is (0.2-0.4):1.

[0031] More preferably, in step 1), the mass ratio of copper acetate monohydrate to urea is 0.33:1.

[0032] Further, in step 2), when the pyrolysis time is 0 min, Cu / CN-0 is obtained, wherein the content of pyridine nitrogen is 64 wt% and the content of pyrrole nitrogen is 36 wt%; when the pyrolysis time is 30 min, Cu / CN-30 is obtained, wherein the content of pyridine nitrogen is 88 wt% and the content of pyrrole nitrogen is 12 wt%; when the pyrolysis time is 60 min, Cu / CN-60 is obtained, wherein the content of pyridine nitrogen is 75 wt% and the content of pyrrole nitrogen is 25 wt%.

[0033] The present invention also provides the aforementioned anode catalyst, the preparation method of which includes the following steps:

[0034] Step 1): Dissolve ferrous sulfate, nickel nitrate and urea in deionized water and stir until fully dissolved at room temperature. The Fe / Ni molar ratio can be any one of 0 / 10, 1 / 9, 2 / 8, 3 / 7 or 5 / 5.

[0035] Step 2): Transfer the above solution to an autoclave and react in an oven at 90-120℃ for 12-16 hours. Then cool the reaction solution to room temperature, collect the precipitate, wash it, and dry it to obtain Fe with an adjustable Fe / Ni ratio. y Ni 10-y (OH) x Nanosheets were obtained, and the resulting products included Ni(OH)2 and Fe1Ni9(OH). x Fe2Ni8(OH) x Fe3Ni7(OH) x Or Fe5Ni5(OH) x Any one of them, where x ranges from 2 to 2.74.

[0036] Further, in step 1), the molar ratio of the total amount of ferrous sulfate and nickel nitrate to the molar ratio of urea is 1:5.

[0037] Furthermore, in step 2), the drying is carried out at 60°C for 2 hours.

[0038] Furthermore, in the anode catalyst, electron transfer occurs between Fe and Ni, causing some Ni to... 2+ To Ni 3+ Transformation, Ni with Ni 3+ with Ni 2+ The valence state exists.

[0039] Furthermore, the Fe y Ni 10-y (OH) x In the process, as the Fe / Ni ratio changes, Ni... 3+ / Ni 2+ The range is 0.31-1.28.

[0040] The beneficial effects of this invention are as follows:

[0041] 1. In existing methane-carbon dioxide co-conversion pathways, the methane / carbon dioxide conversion ratio is limited by the stoichiometric ratio, making it difficult to apply to all carbon-rich natural gas. This invention proposes a method for directly converting carbon-rich natural gas. This method achieves co-conversion of carbon-rich natural gas by controlling the electrode material and applied voltage. The molar ratio of CO2 / CH4 consumed in the reaction is 0.08-2.25, making it applicable to all carbon-rich natural gas (n(CO2) / n(CH4) = 0.09-1.45).

[0042] 2. The reaction conditions of this invention are mild, enabling the conversion of inert methane and carbon dioxide in carbon-rich natural gas under normal temperature and pressure conditions.

[0043] 3. The successful implementation of the direct conversion of carbon dioxide and methane in carbon-rich natural gas through electrocatalysis will help promote the industrial utilization of carbon-rich natural gas and support global carbon emission reduction targets. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the electrocatalytic reaction apparatus of the present invention.

[0045] Figure 2 XPS plots of N1s for different cathode catalysts;

[0046] in, Figure 2 (a) is the spectrum of Cu / CN-0. Figure 2 (b) is the spectrum of Cu / CN-30. Figure 2 (c) is the spectrum of Cu / CN-60.

[0047] Figure 3 XPS plots of Ni 2p for different anode catalysts;

[0048] in, Figure 3(a) is the spectrum of Ni(OH)2; Figure 3 (b) is Fe1Ni9(OH) x Spectrum; Figure 3 (c) is Fe2Ni8(OH) x Spectrum; Figure 3 (d) is Fe3Ni7(OH) x Spectrum; Figure 3 (e) is Fe5Ni5(OH) x The spectrum.

[0049] Figure 4 To control the molar ratio of CO2 / CH4 consumed when a voltage of 0.40-0.55V (vs. RHE) is applied;

[0050] in, Figure 4 (A) represents the molar ratio of CO2 / CH4 consumed by Cu / CN-30||Ni(OH)2 in the voltage range of 0.40-0.55V (vs. RHE). Figure 4 (B) represents Cu / CN-30||Fe1Ni9(OH) x The molar ratio of CO2 / CH4 consumed within a voltage range of 0.40-0.55V (vs. RHE) Figure 4 (C) represents Cu / CN-30||Fe2Ni8(OH) x The molar ratio of CO2 / CH4 consumed in the voltage range of 0.40-0.55V (vs. RHE) Figure 4 (D) represents Cu / CN-30||Fe3Ni7(OH) x The molar ratio of CO2 / CH4 consumed in the voltage range of 0.40-0.55V (vs. RHE).

[0051] Figure 5 To control the molar ratio of CO2 / CH4 consumed by the cathode electrode material;

[0052] in, Figure 5 (A) is when the applied voltage is -0.40V (vs. RHE) and the anode catalyst is fixed as Fe3Ni7(OH). x The variation of the CO2 / CH4 consumption molar ratio obtained by controlling the cathode catalysts Cu / CN-0, Cu / CN-30 and Cu / CN-60; Figure 5 (B) is the case where the applied voltage is -0.45V (vs. RHE) and the anode catalyst is fixed as Fe3Ni7(OH). x The variation of the CO2 / CH4 consumption molar ratio obtained by controlling the cathode catalysts Cu / CN-0, Cu / CN-30 and Cu / CN-60; Figure 5(C) shows the application of a voltage of -0.50V (vs. RHE) with the anode catalyst fixed at Fe3Ni7(OH). x The variation of the CO2 / CH4 consumption molar ratio obtained by controlling the cathode catalysts Cu / CN-0, Cu / CN-30 and Cu / CN-60; Figure 5 (D) is the case where the applied voltage is -0.55V (vs. RHE) and the anode catalyst is fixed as Fe3Ni7(OH). x The variation of the CO2 / CH4 consumption molar ratio obtained by controlling the cathode catalysts Cu / CN-0, Cu / CN-30 and Cu / CN-60 was investigated.

[0053] Figure 6 To control the molar ratio of CO2 / CH4 consumed by the anode electrode material;

[0054] in, Figure 6 (A) is when a voltage of -0.40V (vs. RHE) is applied, with the cathode catalyst fixed at Cu / CN-30 and the anode catalyst adjusted to Ni(OH)2 and Fe1Ni9(OH). x Fe2Ni8(OH) x Fe3Ni7(OH) x With Fe5Ni5(OH) x The changing trend of the CO2 / CH4 consumption molar ratio; Figure 6 (B) is when a voltage of -0.45V (vs. RHE) is applied, with the cathode catalyst fixed at Cu / CN-30 and the anode catalyst adjusted to Ni(OH)2 and Fe1Ni9(OH). x Fe2Ni8(OH) x Fe3Ni7(OH) x With Fe5Ni5(OH) x The changing trend of the CO2 / CH4 consumption molar ratio; Figure 6 (C) is when a voltage of -0.50V (vs. RHE) is applied, with the cathode catalyst fixed at Cu / CN-30 and the anode catalyst adjusted to Ni(OH)2 and Fe1Ni9(OH). x Fe2Ni8(OH) x Fe3Ni7(OH) x With Fe5Ni5(OH) x The changing trend of the CO2 / CH4 consumption molar ratio; Figure 6 (D) is when a voltage of -0.55V (vs. RHE) is applied, with the cathode catalyst fixed at Cu / CN-30 and the anode catalyst adjusted to Ni(OH)2 and Fe1Ni9(OH). x Fe2Ni8(OH)x Fe3Ni7(OH) x With Fe5Ni5(OH) x The changing trend of the CO2 / CH4 consumption molar ratio. Detailed Implementation

[0055] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0056] Preparation Example 1

[0057] Cathode catalyst: Cu / CN-30, with a copper loading of 26.46% and a copper particle size of 17.26 nm. The carbon nitride support contains 88 wt% pyridine nitrogen and 12 wt% pyrrole nitrogen.

[0058] The preparation method is as follows:

[0059] Step 1): Dissolve urea and copper acetate monohydrate in deionized water at a mass ratio of 0.33:1, mix well, remove water by rotary evaporation, and then grind evenly.

[0060] Step 2): Weigh a certain amount of the precursor into a tube furnace, heat it to 500℃ under a nitrogen atmosphere, and hold it for 30 minutes to obtain Cu / CN-30.

[0061] Anode catalyst: Fe y Ni 10-y (OH) x Nanosheets, where y = 0, 1, 2 or 3.

[0062] The preparation method is as follows:

[0063] Step 1): Dissolve a certain amount of ferrous sulfate, nickel nitrate, and urea (the molar ratio of the total amount of ferrous sulfate and nickel nitrate to urea = 1:5) in deionized water and stir until fully dissolved at room temperature.

[0064] Step 2): Transfer the above solution to an autoclave and react in an oven at 90°C for 12 hours. Then cool the reaction solution to room temperature, collect the precipitate, wash it, and dry it at 60°C for 12 hours to obtain Fe. y Ni 10-y (OH) x Nanosheets.

[0065] Example 1-1

[0066] A method for the direct conversion of carbon-rich natural gas involves accurately measuring 15 mL of 0.1 M KOH electrolyte into an H-type single-chamber electrolytic cell. A three-electrode system is constructed using Cu / CN-30 as the cathode catalyst, Ni(OH)2 as the anode catalyst, and Hg / HgO as the reference electrode. The flow rate of the CH4, CO2, and Ar mixture is set to 40 mL / min. -1 The reaction time is 1 hour.

[0067] Liquid products were collected and analyzed after the reaction. The applied voltage was adjusted to -0.40V, -0.45V, -0.50V, and -0.55V (vs. RHE) to investigate the effect of voltage adjustment on the molar ratio of CO2 / CH4 consumed. At a voltage of -0.45V (vs. RHE), the CO2 conversion rate reached its maximum of 5.09 mmol / g. cat -1 h -1 At a voltage of -0.55V (vs. RHE), the conversion rate of CH4 reaches a maximum of 8.52 mmol / g. cat -1 h -1 .

[0068] from Figure 4 As can be seen from (A), the CO2 / CH4 consumption ratio ranges from 0.91 to 2.25, and the CO2 / CH4 consumption ratio decreases as the applied voltage increases.

[0069] Examples 1-2

[0070] A method for the direct conversion of carbon-rich natural gas involves accurately measuring 15 mL of 0.1 M KOH electrolyte into an H-type single-chamber electrolytic cell, using Cu / CN-30 as the cathode catalyst, and Fe1Ni9(OH)2. x Using Hg / HgO as the anode catalyst and Hg / HgO as the reference electrode, a three-electrode system was constructed. The flow rate of the CH4, CO2, and Ar mixture was set to 40 mL / min. -1 The reaction time is 1 hour.

[0071] Liquid products were collected and analyzed after the reaction. The applied voltage was adjusted to -0.40V, -0.45V, -0.50V, and -0.55V (vs. RHE) to investigate the effect of voltage adjustment on the molar ratio of CO2 / CH4 consumed. At a voltage of -0.45V (vs. RHE), the CO2 conversion rate reached its maximum of 5.06 mmol / g. cat -1 h -1 At a voltage of -0.55V (vs. RHE), the conversion rate of CH4 reaches a maximum of 11.58 mmol / g. cat -1 h-1 .

[0072] from Figure 4 As can be seen from (B), the CO2 / CH4 consumption ratio ranges from 0.35 to 0.74, and the CO2 / CH4 consumption ratio decreases as the applied voltage increases.

[0073] Examples 1-3

[0074] A method for the direct conversion of carbon-rich natural gas involves accurately measuring 15 mL of 0.1 M KOH electrolyte into an H-type single-chamber electrolytic cell, using Cu / CN-30 as the cathode catalyst, and Fe2Ni8(OH)2 as the cathode catalyst. x Using Hg / HgO as the anode catalyst and Hg / HgO as the reference electrode, a three-electrode system was constructed. The flow rate of the CH4, CO2, and Ar mixture was set to 40 mL / min. -1 The reaction time is 1 hour.

[0075] Liquid products were collected and analyzed after the reaction. The applied voltage was adjusted to -0.40V, -0.45V, -0.50V, and -0.55V (vs. RHE) to investigate the effect of voltage adjustment on the molar ratio of CO2 / CH4 consumed. At a voltage of -0.45V (vs. RHE), the CO2 conversion rate reached its maximum of 5.11 mmol / g. cat -1 h -1 At a voltage of -0.55V (vs. RHE), the conversion rate of CH4 reaches a maximum of 12.92 mmol / g. cat -1 h -1 .

[0076] from Figure 4 As can be seen from (C), the CO2 / CH4 consumption ratio ranges from 0.32 to 0.66, and the CO2 / CH4 consumption ratio decreases as the applied voltage increases.

[0077] Examples 1-4

[0078] A method for the direct conversion of carbon-rich natural gas involves accurately measuring 15 mL of 0.1 M KOH electrolyte into an H-type single-chamber electrolytic cell, using Cu / CN-30 as the cathode catalyst, and Fe3Ni7(OH)2 as the cathode catalyst. x Using Hg / HgO as the anode catalyst and Hg / HgO as the reference electrode, a three-electrode system was constructed. The flow rate of the CH4, CO2, and Ar mixture was set to 40 mL / min. -1 The reaction time is 1 hour.

[0079] Liquid products were collected and analyzed after the reaction. The applied voltage was adjusted to -0.40V, -0.45V, -0.50V, and -0.55V (vs. RHE) to investigate the effect of voltage adjustment on the molar ratio of CO2 / CH4 consumed. At a voltage of -0.45V (vs. RHE), the CO2 conversion rate reached its maximum of 5.09 mmol / g. cat -1 h -1 At a voltage of -0.55V (vs. RHE), the conversion rate of CH4 reaches a maximum of 17.89 mmol / g. cat -1 h -1 .

[0080] from Figure 4 As can be seen from (D), the CO2 / CH4 consumption ratio ranges from 0.23 to 0.48, and the CO2 / CH4 consumption ratio decreases as the applied voltage increases.

[0081] Preparation Example 2

[0082] Cathode catalyst: Cu / CN-t, t = 0, 30, or 60. In Cu / CN-0, the carbon nitride support contains 64 wt% pyridine nitrogen and 36 wt% pyrrole nitrogen; in Cu / CN-30, the carbon nitride support contains 88 wt% pyridine nitrogen and 12 wt% pyrrole nitrogen; and in Cu / CN-60, the carbon nitride support contains 75 wt% pyridine nitrogen and 25 wt% pyrrole nitrogen.

[0083] The preparation method is as follows:

[0084] Step 1): Dissolve urea and copper acetate monohydrate in deionized water at a mass ratio of 0.33:1, mix well, remove water by rotary evaporation, and then grind evenly.

[0085] Step 2): Weigh a certain amount of precursor into a tube furnace, heat it to 500℃ under a nitrogen atmosphere, and hold it for 0 min, 30 min or 60 min to obtain Cu / CN-0, Cu / CN-30 or Cu / CN-60 respectively.

[0086] Anode catalyst: Fe3Ni7(OH) x Nanosheets, x = 2.69, x is 2-2.74, their Ni 3+ / Ni 2+ The surface atomic ratio is 1.28.

[0087] The preparation method is as follows:

[0088] Step 1): Dissolve a certain amount of ferrous sulfate, nickel nitrate, and urea (the molar ratio of the total amount of ferrous sulfate and nickel nitrate to urea = 1:5) in deionized water and stir until fully dissolved at room temperature.

[0089] Step 2): Transfer the above solution to an autoclave and react in an oven at 90°C for 12 hours. Then cool the reaction solution to room temperature, collect the precipitate, wash it, and dry it at 60°C for 12 hours to obtain Fe3Ni7(OH). x Nanosheets.

[0090] Example 2-1

[0091] A method for the direct conversion of carbon-rich natural gas involves accurately measuring 15 mL of 0.1 M KOH electrolyte into an H-type single-chamber electrolytic cell. By adjusting the cathode electrode material, Cu / CN-0, Cu / CN-30, and Cu / CN-60 are used as the cathode catalysts, respectively, along with Fe3Ni7(OH). x Using Hg / HgO as the anode catalyst and Hg / HgO as the reference electrode, a three-electrode system was constructed. The flow rate of the CH4, CO2, and Ar mixture was set to 40 mL / min. -1 The applied voltage was -0.40V (vs. RHE), and the reaction time was 1h.

[0092] Liquid products were collected and analyzed after the reaction. The CO2 conversion rate reached a maximum of 3.88 mmol / g when the cathode catalyst was Cu / CN-30. cat -1 h -1 .from Figure 5 As can be seen from (A), the CO2 / CH4 consumption ratio ranges from 0.08 to 0.28.

[0093] Example 2-2

[0094] A method for the direct conversion of carbon-rich natural gas involves accurately measuring 15 mL of 0.1 M KOH electrolyte into an H-type single-chamber electrolytic cell. By adjusting the cathode electrode material, Cu / CN-0, Cu / CN-30, and Cu / CN-60 are used as the cathode catalysts, respectively, along with Fe3Ni7(OH). x Using Hg / HgO as the anode catalyst and Hg / HgO as the reference electrode, a three-electrode system was constructed. The flow rate of the CH4, CO2, and Ar mixture was set to 40 mL / min. -1 The applied voltage was -0.45V (vs. RHE), and the reaction time was 1h.

[0095] Liquid products were collected and analyzed after the reaction. The CO2 conversion rate reached a maximum of 4.75 mmol / g when the cathode catalyst was Cu / CN-30. cat -1 h-1 .from Figure 5 As can be seen from (B), the CO2 / CH4 consumption ratio ranges from 0.11 to 0.30.

[0096] Example 2-3

[0097] A method for the direct conversion of carbon-rich natural gas involves accurately measuring 15 mL of 0.1 M KOH electrolyte into an H-type single-chamber electrolytic cell. By adjusting the cathode electrode material, Cu / CN-0, Cu / CN-30, and Cu / CN-60 are used as the cathode catalysts, respectively, along with Fe3Ni7(OH). x Using Hg / HgO as the anode catalyst and Hg / HgO as the reference electrode, a three-electrode system was constructed. The flow rate of the CH4, CO2, and Ar mixture was set to 40 mL / min. -1 The applied voltage was -0.50V (vs. RHE), and the reaction time was 1h.

[0098] Liquid products were collected and analyzed after the reaction. The CO2 conversion rate reached a maximum of 5.60 mmol / g when the cathode catalyst was Cu / CN-30. cat -1 h -1 .from Figure 5 As can be seen from (C), the CO2 / CH4 consumption ratio ranges from 0.16 to 0.37.

[0099] Examples 2-4

[0100] A method for the direct conversion of carbon-rich natural gas involves accurately measuring 15 mL of 0.1 M KOH electrolyte into an H-type single-chamber electrolytic cell. By adjusting the cathode electrode material, Cu / CN-0, Cu / CN-30, and Cu / CN-60 are used as the cathode catalysts, respectively, along with Fe3Ni7(OH). x Using Hg / HgO as the anode catalyst and Hg / HgO as the reference electrode, a three-electrode system was constructed. The flow rate of the CH4, CO2, and Ar mixture was set to 40 mL / min. -1 The applied voltage was -0.55V (vs. RHE), and the reaction time was 1h.

[0101] Liquid products were collected and analyzed after the reaction. The CO2 conversion rate reached a maximum of 6.78 mmol / g when the cathode catalyst was Cu / CN-30. cat -1 h -1 .from Figure 5 As can be seen from (D), the CO2 / CH4 consumption ratio ranges from 0.24 to 0.48.

[0102] Preparation Example 3

[0103] Cathode catalyst: Cu / CN-30, with a copper loading of 26.46% and a copper particle size of 17.26 nm. The carbon nitride support contains 88 wt% pyridine nitrogen and 12 wt% pyrrole nitrogen.

[0104] The preparation method is as follows:

[0105] Step 1): Dissolve urea and copper acetate monohydrate in deionized water at a mass ratio of 0.33:1, mix well, remove water by rotary evaporation, and then grind evenly.

[0106] Step 2): Weigh a certain amount of the precursor into a tube furnace, heat it to 500℃ under a nitrogen atmosphere, and hold it for 30 minutes to obtain Cu / CN-30.

[0107] Anode catalyst: Fe y Ni 10-y (OH) x Nanosheets, where y = 0, 1, 2, 3 or 5.

[0108] The preparation method is as follows:

[0109] Step 1): Dissolve a certain amount of ferrous sulfate, nickel nitrate, and urea (the molar ratio of the total amount of ferrous sulfate and nickel nitrate to urea = 1:5) in deionized water and stir until fully dissolved at room temperature.

[0110] Step 2): Transfer the above solution to an autoclave and react in an oven at 90°C for 12 hours. Then cool the reaction solution to room temperature, collect the precipitate, wash it, and dry it at 60°C for 12 hours to obtain Fe. y Ni 10-y (OH) x Nanosheets.

[0111] Example 3-1

[0112] A method for the direct conversion of carbon-rich natural gas involves accurately measuring 15 mL of 0.1 M KOH electrolyte into an H-type single-chamber electrolytic cell, adjusting the cathode electrode material, using Cu / CN-30 as the cathode catalyst, and employing Ni(OH)2 and Fe1Ni9(OH)2 respectively. x Fe2Ni8(OH) x Fe3Ni7(OH) x With Fe5Ni5(OH) x Using Hg / HgO as the anode catalyst and Hg / HgO as the reference electrode, a three-electrode system was constructed. The flow rate of the CH4, CO2, and Ar mixture was set to 40 mL / min. -1 The applied voltage was -0.40V (vs. RHE), and the reaction time was 1h.

[0113] Liquid products were collected and analyzed after the reaction. This was observed when the anode catalyst was Fe3Ni7(OH). x At that time, the conversion rate of CH4 reached a maximum of 9.55 mmol / g. cat -1 h -1 .from Figure 6 As can be seen from (A), the CO2 / CH4 consumption ratio ranges from 0.48 to 2.25.

[0114] Example 3-2

[0115] A method for the direct conversion of carbon-rich natural gas involves accurately measuring 15 mL of 0.1 M KOH electrolyte into an H-type single-chamber electrolytic cell, adjusting the cathode electrode material, using Cu / CN-30 as the cathode catalyst, and employing Ni(OH)2 and Fe1Ni9(OH)2 respectively. x Fe2Ni8(OH) x Fe3Ni7(OH) x With Fe5Ni5(OH) x Using Hg / HgO as the anode catalyst and Hg / HgO as the reference electrode, a three-electrode system was constructed. The flow rate of the CH4, CO2, and Ar mixture was set to 40 mL / min. -1 The applied voltage was -0.45V (vs. RHE), and the reaction time was 1h.

[0116] Liquid products were collected and analyzed after the reaction. This was observed when the anode catalyst was Fe3Ni7(OH). x At that time, the conversion rate of CH4 reached a maximum of 13.68 mmol / g. cat -1 h -1 .from Figure 6 As can be seen from (B), the CO2 / CH4 consumption ratio ranges from 0.37 to 1.43.

[0117] Example 3-3

[0118] A method for the direct conversion of carbon-rich natural gas involves accurately measuring 15 mL of 0.1 M KOH electrolyte into an H-type single-chamber electrolytic cell, adjusting the cathode electrode material, using Cu / CN-30 as the cathode catalyst, and employing Ni(OH)2 and Fe1Ni9(OH)2 respectively. x Fe2Ni8(OH) x Fe3Ni7(OH) x With Fe5Ni5(OH) x Using Hg / HgO as the anode catalyst and Hg / HgO as the reference electrode, a three-electrode system was constructed. The flow rate of the CH4, CO2, and Ar mixture was set to 40 mL / min. -1The applied voltage was -0.50V (vs. RHE), and the reaction time was 1h.

[0119] Liquid products were collected and analyzed after the reaction. This was observed when the anode catalyst was Fe3Ni7(OH). x At that time, the conversion rate of CH4 reached a maximum of 15.43 mmol / g. cat -1 h -1 .from Figure 6 As can be seen from (C), the CO2 / CH4 consumption ratio ranges from 0.31 to 1.17.

[0120] Examples 3-4

[0121] A method for the direct conversion of carbon-rich natural gas involves accurately measuring 15 mL of 0.1 M KOH electrolyte into an H-type single-chamber electrolytic cell, adjusting the cathode electrode material, using Cu / CN-30 as the cathode catalyst, and employing Ni(OH)2 and Fe1Ni9(OH)2 respectively. x Fe2Ni8(OH) x Fe3Ni7(OH) x With Fe5Ni5(OH) x Using Hg / HgO as the anode catalyst and Hg / HgO as the reference electrode, a three-electrode system was constructed. The flow rate of the CH4, CO2, and Ar mixture was set to 40 mL / min. -1 The applied voltage was -0.50V (vs. RHE), and the reaction time was 1h.

[0122] Liquid products were collected and analyzed after the reaction. This was observed when the anode catalyst was Fe3Ni7(OH). x At that time, the conversion rate of CH4 reached a maximum of 17.89 mmol / g. cat -1 h -1 .from Figure 6 As can be seen from (D), the CO2 / CH4 consumption ratio ranges from 0.23 to 0.91.

[0123] Figure 1 This is a schematic diagram of the electrocatalytic reaction apparatus in all embodiments of the present invention.

[0124] Figure 2 XPS plots of N1s for different cathode catalysts;

[0125] in Figure 2 (a) is the spectrum of Cu / CN-0. The peaks can be fitted into two peaks. The peak at about 398.8 eV can be attributed to the characteristic peak of pyridine nitrogen, and the peak at about 399.9 eV can be attributed to the characteristic peak of pyrrole nitrogen. Through the analysis of the peak area, it can be found that the content of pyridine nitrogen in Cu / CN-0 is 64% and the content of pyrrole nitrogen is 36%. Figure 2 (b) is the spectrum of Cu / CN-30, whose characteristic peaks are assigned the same as those of Cu / CN-0, with pyridine nitrogen content of 88% and pyrrole nitrogen content of 12%. Figure 2 (c) is the spectrum of Cu / CN-60, whose characteristic peaks are assigned the same as those of Cu / CN-0, with pyridine nitrogen content of 75% and pyrrole nitrogen content of 25%.

[0126] Figure 3 XPS plots of N1s for different cathode catalysts;

[0127] in, Figure 3 (a) is the spectrum of Ni(OH)2, with the peak around 856.36 eV attributed to Ni. 2+ ; Figure 3 (b) is Fe1Ni9(OH) x The spectrum can be fitted into two peaks, with the peak around 856.36 eV belonging to Ni. 2+ The species, with a peak around 857.91 eV, is attributed to Ni. 3+ The species, Ni, can be obtained by analyzing the peak area. 3+ / Ni 2+ =0.31; Figure 3 (c) is Fe2Ni8(OH) x The spectrum, and the attribution of its characteristic peaks to Fe1Ni9(OH) x The same, Ni 3+ / Ni 2+ =0.48; Figure 3 (d) is Fe3Ni7(OH) x The spectrum, and the attribution of its characteristic peaks to Fe1Ni9(OH) x The same, Ni 3+ / Ni 2+ =1.28. Figure 3 (e) is Fe5Ni5(OH) x The spectrum, the assignment of characteristic peaks to Fe1Ni9(OH) x Same, Ni 3+ / Ni 2+ =0.91.

[0128] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A method for the direct conversion of carbon-rich natural gas, characterized in that, A three-electrode system consisting of a cathode catalyst, an anode catalyst, and a reference electrode is constructed in an electrolytic cell. A mixture of CH4, CO2, and Ar is introduced into the reaction system at room temperature and pressure to carry out the reaction. The active metal of the cathode catalyst is Cu, the active metal of the anode catalyst is Ni, and the molar ratio of CO2 / CH4 consumed in the electrocatalytic reaction is 0.08-2.

25.

2. The method according to claim 1, characterized in that, The flow rate of the CH4, CO2 and Ar mixture is 20-40 mL / min. -1 .

3. The method according to claim 1 or 2, characterized in that, The cathode catalyst consists of a carbon nitride support and copper particles, wherein the copper particles are uniformly loaded on the sheet-like carbon nitride support, and the loading of the copper particles is approximately 26.46%.

4. The method according to claim 1 or 2, characterized in that, The cathode catalyst is copper particles supported on carbon nitride with adjustable pyridine nitrogen content. The carbon nitride support contains pyridine nitrogen and pyrrole nitrogen, with pyridine nitrogen accounting for 64%-88% of the mass of the carbon nitride support and pyrrole nitrogen accounting for 12%-36% of the mass of the carbon nitride support.

5. The method according to claim 1 or 2, characterized in that, The anode catalyst is Fe. y Ni 10-y (OH) x , where y is independently 0, 1, 2, 3 or 5, and x is 2-2.

74.

6. The method according to claim 1 or 2, characterized in that, In the anode catalyst, Ni is in the form of Ni 3+ with Ni 2+ The valence state exists for Ni. 3+ / Ni 2+ The surface atomic ratio is 0.31-1.

28.

7. The method according to claim 1 or 2, characterized in that, In the electrocatalytic reaction, the applied operating voltage is 0.40-0.55V (vs. RHE).

8. The method according to claim 1 or 2, characterized in that, In the electrocatalytic reaction, the electrolyte used is 0.1M KOH.

9. A cathode catalyst for use in the method according to any one of claims 1-8, characterized in that, The method for preparing the cathode catalyst includes the following steps: Step 1): Dissolve urea and copper acetate monohydrate in deionized water and mix evenly. After rotary evaporation to remove water, grind evenly to obtain the precursor. Step 2): Weigh the precursor and place it in a tube furnace. Under a nitrogen atmosphere, heat it to 400-500℃ and maintain it for 0-60 minutes. By adjusting the pyrolysis time, copper particles loaded with carbon nitride with adjustable pyridine nitrogen content are obtained, which is Cu / CN-t, where t is the pyrolysis time.

10. An anode catalyst for use in the method according to any one of claims 1-8, characterized in that, The preparation method of the anode catalyst includes the following steps: Step 1): Dissolve ferrous sulfate, nickel nitrate, and urea in deionized water and stir until fully dissolved at room temperature. The Fe / Ni molar ratio can be any one of 0 / 10, 1 / 9, 2 / 8, 3 / 7, or 5 / 5. Step 2): Transfer the above solution to an autoclave and react in an oven at 90-120℃ for 12-16 hours. Then cool the reaction solution to room temperature, collect the precipitate, wash it, and dry it to obtain Fe with an adjustable Fe / Ni ratio. y Ni 10-y (OH) x Nanosheets were obtained, and the resulting products included Ni(OH)2 and Fe1Ni9(OH). x Fe2Ni8(OH) x Fe3Ni7(OH) x Or Fe5Ni5(OH) x Any one of them, where x ranges from 2 to 2.74.

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