A method for producing C2 hydrocarbons and benzene by coupling oxidation of methane with carbon dioxide

Abstract

This invention relates to a method for the coupling production of C2 hydrocarbons and benzene from methane via carbon dioxide oxidation, belonging to the field of chemical production technology. Specifically, a mixture of methane and carbon dioxide is passed through a reactor equipped with a catalyst to produce C2 hydrocarbons and benzene, with carbon monoxide and water as byproducts. In this method, the selective production of C2 hydrocarbons and benzene is achieved by changing the type and composition of the catalyst and simultaneously adjusting the reaction conditions. This invention features a short process flow, simple operation, and uses an inexpensive, readily available, and stable catalyst, making it easy to scale up industrially and showing promising prospects for industrial application.

Description

Technical Field

[0001] This invention relates to a method and catalyst for the coupling production of C2 hydrocarbons and benzene by oxidizing methane with carbon dioxide, belonging to the field of chemical production technology. Background Technology

[0002] Methane (CH4) is a major component of natural gas, shale gas, coalbed methane, and combustible ice. Its abundant reserves and low price have made it a crucial pillar of modern global economic development, following oil. As an important chemical raw material, its efficient conversion and utilization has been a research hotspot in the field of catalysis for decades. Among these, the oxidative coupling of methane to prepare hydrocarbons has attracted considerable attention due to its potential applications. However, methane is the most inert molecule among hydrocarbons. If oxygen is used in its oxidative coupling, deep oxidation of methane is inevitable, producing carbon monoxide (CO) or carbon dioxide (CO2), which reduces the selectivity of hydrocarbon products (J. Catal. 2022, 408, 173-178). Mild oxidants such as H2O, N2O, NO, S2, SO2, and SO3 suffer from high costs, low selectivity of hydrocarbon products, or low methane conversion rates (Angew. Chem., Int. Ed. 2021, 60, 10502-10515). Carbon dioxide, as a major greenhouse gas, can also act as a mild oxidant. Furthermore, it, along with methane, belongs to an important and abundant C1 resource. Converting both into high-value-added chemicals simultaneously can not only efficiently utilize C1 resources but also help solve environmental problems, which is of great significance for achieving sustainable development in both the environmental and energy sectors.

[0003] Generally, the oxidative coupling reaction of methane follows a heterogeneous-homogeneous catalytic reaction mechanism. Methane is activated on the catalyst surface to generate methyl radicals, which then undergo homogeneous coupling in the gas phase to produce ethane. Ethane is then dehydrogenated to products such as ethylene. If oxygen is used as the oxidant, the generated methyl radicals readily react with oxygen to undergo deep oxidation, producing carbon monoxide or carbon dioxide. However, the characteristic of carbon dioxide oxidative methane coupling is that carbon dioxide does not induce gas-phase radical reactions; carbon monoxide is the only byproduct, meaning the reaction is mainly controlled by heterogeneous catalysis. Currently, the catalyst systems used for carbon dioxide oxidative methane coupling are mainly complexes of alkali (earth) metal oxides (Li₂O, Na₂O, MgO, CaO, SrO, BaO) and variable-valence metal oxides (ZnO, Cr₂O₃, MnO₂, CeO₂). The challenge is that the products are mainly gaseous C2 hydrocarbons, and the catalyst stability and catalytic performance do not have a significant advantage over those using oxygen as an oxidant (Appl. Catal., A1998, 172, L203-L206; Chem. Lett. 1998, 27, 1209-1210; J. Catal. 2000, 192, 252-255; Appl. Catal., A2001, 219, 183-193; Chem. Lett. 2002, 31, 828-829; Catal. Lett. 2003, 86, 191-195; Curr. Org. Synth. 2010, 7, 533-542; Energy Environ. Sci. 2012, 5, 9419-9437; Sci. Rep. 2019, 9, 15454). Currently, the conversion of methane to long-chain hydrocarbons or aromatics is mostly achieved through anaerobic coupling, a process in which catalysts are prone to rapid deactivation due to carbon deposition. However, research on the generation of long-chain hydrocarbons or aromatics via oxidative coupling is challenging, and there is currently no method for controlling the catalyst or reaction conditions to regulate the oxidative coupling products between C2 hydrocarbons and aromatics. Conventional catalysts also often suffer from carbon deposition leading to catalyst deactivation during the carbon dioxide-to-methane coupling process. Summary of the Invention

[0004] The purpose of this invention is to develop a method for the coupling production of C2 hydrocarbons and benzene by oxidizing methane with carbon dioxide, so as to solve the above-mentioned technical problems.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for the coupling production of C2 hydrocarbons and benzene using carbon dioxide to oxidize methane involves passing a mixture of methane and carbon dioxide through a reactor equipped with a catalyst to produce C2 hydrocarbons and benzene, with carbon monoxide and water as byproducts. In this method, the selectivity of C2 hydrocarbons and benzene is achieved by changing the type and composition of the catalyst and simultaneously adjusting the reaction conditions. This is because using a suitable catalyst and changing the flow rate or pressure can alter the residence time of reactants or intermediates, thereby changing the product distribution.

[0007] Furthermore, the reaction temperature for the carbon dioxide oxidation of methane coupling is 800–1100 °C; the reaction pressure is 0–1.0 MPa (gauge pressure); the molar ratio of methane to carbon dioxide in the reaction mixture is 6:1–1:1; and the total mass hourly space velocity of the reaction mixture is 1 × 10⁻⁶. 3 ~1×10 7 ml·g -1 ·h -1 .

[0008] Furthermore, the reactor is a fixed-bed reactor.

[0009] Furthermore, the catalyst is: a composite catalyst composed of alkaline earth metal oxides and rare earth metal oxides, a composite catalyst composed of Na2WO4 and rare earth metal oxides, a composite catalyst composed of different rare earth metal oxides, or a composite catalyst composed of rare earth metal oxides and alkali metal oxides.

[0010] Furthermore, when using a composite catalyst composed of alkaline earth metal oxides and rare earth metal oxides, the mass fraction of the alkaline earth metal oxides in the composite catalyst ranges from 0.1% to 8.5%. The mass hourly space velocity (HHSV) under the reaction conditions is in the range of 1 × 10⁻⁶. 4 ~1×10 7 ml·g -1 ·h -1 Simultaneously, at a reaction pressure of 0.5–1.0 MPa (gauge pressure), the total hydrocarbon product selectivity is >60%. The alkaline earth metal oxides are magnesium oxide, calcium oxide, strontium oxide, or barium oxide, and the rare earth metal oxides are one or more of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, and yttrium oxide. The catalyst selected in this scheme exhibits good stability during the carbon dioxide-methane coupling process, and no carbon deposition was observed on the catalyst.

[0011] Preferably, the mass fraction of magnesium oxide in the composite catalyst formed with the rare earth metal oxide is 0.1% to 4%; the mass fraction of calcium oxide in the composite catalyst formed with the rare earth metal oxide is 0.5% to 5%; the mass fraction of strontium oxide in the composite catalyst formed with the rare earth metal oxide is 1% to 6%; and the mass fraction of barium oxide in the composite catalyst formed with the rare earth metal oxide is 2% to 8.5%.

[0012] Furthermore, when using a composite catalyst composed of Na₂WO₄ and rare earth metal oxides, the mass fraction of Na₂WO₄ in the composite catalyst is 1%–8%. The mass hourly space velocity (HHSV) ranges from 1 × 10⁻⁶ in the reaction conditions. 4 ~1×10 7 ml·g -1 ·h -1 Simultaneously, when the reaction pressure is 0–0.5 MPa (gauge pressure), the selectivity of C2 hydrocarbons in the hydrocarbon products reaches over 50%. The rare earth metal oxides mentioned are one or more of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, and yttrium oxide.

[0013] Furthermore, when using composite catalysts composed of different rare earth metal oxides, the mass hourly space velocity (WHSV) ranges from 6 × 10⁻⁶ in the reaction conditions. 3 ~1×10 7 ml·g -1 ·h -1 Simultaneously, at a reaction pressure of 0–0.2 MPa (gauge pressure), the molar fraction of C2 hydrocarbons in the hydrocarbon products reaches over 92%. The rare earth metal oxides are two or more selected from lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, and yttrium oxide. The catalyst selected in this scheme exhibits good stability during the carbon dioxide-methane coupling process, and no carbon deposition was observed on the catalyst.

[0014] Preferably, the main component of the composite catalyst is a catalyst containing lanthanum oxide, cerium oxide, or samarium oxide.

[0015] Furthermore, when a composite catalyst composed of rare earth metal oxides and alkali metal oxides is used, the mass fraction of the alkali metal oxide in the composite catalyst is 0.1% to 7.5%. And the mass hourly space velocity (HHSV) under the reaction conditions is in the range of 1 × 10⁻⁶. 3 ~6×10 3 ml·g -1 ·h -1Simultaneously, at a reaction pressure of 0–1.2 MPa (gauge pressure), the molar fraction of benzene in the hydrocarbon products reaches 33.6%. The rare earth metal oxides are one or more selected from lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, and yttrium oxide. The alkali metal oxides are lithium oxide, sodium oxide, potassium oxide, rubidium oxide, or cesium oxide. The catalyst selected in this scheme exhibits good stability during the carbon dioxide-methane coupling process, and no carbon deposition was observed on the catalyst.

[0016] Preferably, the mass fraction of lithium oxide in the composite catalyst formed with the rare earth metal oxide is 0.1% to 0.8%; the mass fraction of sodium oxide in the composite catalyst formed with the rare earth metal oxide is 0.2% to 2%; the mass fraction of potassium oxide in the composite catalyst formed with the rare earth metal oxide is 0.3% to 2.6%; the mass fraction of rubidium oxide in the composite catalyst formed with the rare earth metal oxide is 0.6% to 5%; and the mass fraction of cesium oxide in the composite catalyst formed with the rare earth metal oxide is 0.9% to 7.5%.

[0017] Furthermore, the catalyst is prepared using the sol-gel method. The resulting catalyst is used after being directly or by mixing multiple components, then compressed into tablets and sieved.

[0018] Furthermore, the complexing agent in the sol-gel method is one or more of the following: citric acid, ammonium citrate, maleic acid, oxalic acid, ammonium oxalate, ascorbic acid, ethanolamine, diethanolamine, and triethanolamine.

[0019] Furthermore, before the reaction, the gas is heated to the reaction temperature in an inert gas atmosphere (nitrogen, argon, or helium) and then switched to the feed gas for the reaction. The gas after the reaction is analyzed online by a combination of a thermal conductivity detector and a flame ionization detector in a gas chromatograph.

[0020] The beneficial effects of this invention are as follows:

[0021] Compared with the prior art, the beneficial effects of the method and catalyst for methane oxidation using carbon dioxide provided by this invention are mainly reflected in the following aspects:

[0022] (1) The catalyst raw materials of this invention are inexpensive and readily available, the preparation method is simple, and it is easy to scale up industrially.

[0023] (2) Using milder carbon dioxide as an oxidant can effectively avoid deep oxidation of the target product compared with oxygen as an oxidant, and has the advantage of inhibiting catalyst deactivation by carbon deposition compared with methane oxygen-free coupling.

[0024] (3) The process is simple. By controlling the catalyst and reaction conditions, the selectivity of C2 and benzene in hydrocarbon products can be controlled, which is beneficial to industrial applications.

[0025] (4) The raw materials are abundant methane and greenhouse gas carbon dioxide. The two are directly converted into hydrocarbons with higher added value. Compared with the traditional dry reforming and synthesizer route, the process is simpler and requires less investment. This method is of great significance from both energy and environmental perspectives.

[0026] In summary, the method and catalyst process for methane coupling using carbon dioxide provided by this invention are simple, low-cost, and have good prospects for industrial application. Attached Figure Description

[0027] Figure 1 This is a process flow diagram of the present invention utilizing carbon dioxide to oxidize methane coupling;

[0028] Figure 2 This is a stability test diagram of the carbon dioxide oxidation-methane coupling catalyst in Example 6 of the present invention;

[0029] Figure 3 Photograph of the catalyst after stability test in Example 6 of this invention;

[0030] Figure 4 The image shows the thermogravimetric-mass spectrometry (TG-DTA-MS) analysis of the catalyst after the stability test in Example 6 of this invention. Detailed Implementation

[0031] The entire process will be described in detail below through examples, but the scope of the claims of the present invention is not limited to these examples.

[0032] Example 1

[0033] 86.6 g of lanthanum nitrate (La(NO3)3·6H2O), 17.8 g of samarium nitrate (Sm(NO3)3·6H2O), and 55.4 g of citric acid were dissolved together in 350 mL of deionized water. The resulting solution was stirred at 80 °C until it became gel-like, and then placed in an oven at 120 °C for 24 h to obtain a porous foam-like structure. The pulverized powder was calcined in a muffle furnace at 950 °C for 2 h in an air atmosphere. The resulting powdered catalyst was pressed into tablets and sieved to obtain 40-80 mesh particles, denoted as LaSmOx.

[0034] Take 1g of LaSmOx catalyst and place it in the isothermal section of the reaction tube using quartz wool. A schematic diagram of the reactor is shown below. Figure 1As shown in the figure. Under an argon atmosphere at a flow rate of 100 mL / min, the reactor temperature was increased from room temperature to 875 °C over 175 min. After pretreatment at this temperature for 60 min, the reaction gas was switched to: 48% CH4, 48% CO2, and 4% N2, with N2 used as an internal standard. The flow rate was maintained at 200 mL / min, and the reaction pressure was 0 MPa (gauge pressure). Sampling and analysis began after 60 min. The methane conversion rate, product selectivity, and hydrocarbon product distribution are shown in Table 1.

[0035] Example 2

[0036] 76.6 g of yttrium nitrate hydrate (Y(NO3)3·6H2O), 43.3 g of cerium nitrate (Ce(NO3)3·6H2O), and 69.2 g of citric acid were dissolved together in 300 mL of deionized water. The resulting solution was stirred at 80 °C until it became gel-like, and then placed in an oven at 120 °C for 24 h to obtain a porous foam-like structure. The pulverized powder was calcined in a muffle furnace at 950 °C for 2 h in an air atmosphere. The resulting powdered catalyst was pressed into tablets and sieved to obtain 40-80 mesh particles, denoted as YCeOx.

[0037] Take 1g of YCeOx catalyst and place it in the isothermal section of the reaction tube using quartz wool. A schematic diagram of the reactor is shown below. Figure 1 As shown in the figure. Under an argon atmosphere at a flow rate of 100 mL / min, the reactor temperature was increased from room temperature to 900 °C over 180 min. After pretreatment at this temperature for 60 min, the reaction gas was switched to: 48% CH4, 48% CO2, and 4% N2, with N2 used as an internal standard. The flow rate was maintained at 100 mL / min, and the reaction pressure was 0 MPa (gauge pressure). Sampling and analysis began after 60 min. The methane conversion rate, product selectivity, and hydrocarbon product distribution are shown in Table 1.

[0038] Example 3

[0039] 88.9 g of samarium nitrate hydrate (Sm(NO3)3·6H2O), 43.3 g of lanthanum nitrate (La(NO3)3·6H2O), 3.2 g of strontium nitrate (Sr(NO3)2), and 72.6 g of citric acid were dissolved together in 380 mL of deionized water. The resulting solution was stirred at 80 °C until it became gel-like, and then placed in an oven at 120 °C for 24 h to obtain a porous foam-like structure. The pulverized powder was calcined in a muffle furnace at 950 °C for 2 h in an air atmosphere. The resulting powdered catalyst was pressed into tablets and sieved to obtain 40-80 mesh particles, denoted as SrLaSmOx.

[0040] 0.8g of SrLaSmOx catalyst was placed in the isothermal section of the reaction tube using silica wool. A schematic diagram of the reactor is shown below. Figure 1As shown in the figure. Under an argon atmosphere at a flow rate of 100 mL / min, the reactor temperature was increased from room temperature to 900 °C over 180 min. After pretreatment at this temperature for 60 min, the reaction gas was switched to: 64% CH4, 32% CO2, and 4% N2, with N2 used as an internal standard. The flow rate was maintained at 800 mL / min, and the reaction pressure was 0.5 MPa (gauge). Sampling and analysis began after 60 min. The methane conversion rate, product selectivity, and hydrocarbon product distribution are shown in Table 1.

[0041] Example 4

[0042] 43.3 g of lanthanum nitrate (La(NO3)3·6H2O), 43.5 g of praseodymium nitrate hydrate (Pr(NO3)3·6H2O), and 69.2 g of citric acid were dissolved together in 300 mL of deionized water. The resulting solution was stirred at 80 °C until it became gel-like, and then placed in an oven at 120 °C for 24 h to obtain a porous foam-like structure. The pulverized powder was calcined in a muffle furnace at 450 °C for 2 h in an air atmosphere, and the resulting sample was labeled LaPrOx. The obtained powder was then impregnated with 2.6 g of sodium tungstate (Na2WO4) using an equal-volume impregnation method. The resulting sample was dried at 80 °C and then calcined at 950 °C for 2 h in an air atmosphere. The resulting powdered catalyst was tableted and sieved to obtain 40-80 mesh particles, denoted as Na2WO4 / LaPrOx.

[0043] 0.8 g of Na₂WO₄ / LaPrOx catalyst was placed in the isothermal section of the reaction tube using quartz wool. A schematic diagram of the reactor is shown below. Figure 1 As shown in the figure. Under an argon atmosphere at a flow rate of 100 mL / min, the reactor temperature was increased from room temperature to 900 °C over 180 min. After pretreatment at this temperature for 60 min, the reaction gas was switched to: 33% CH4, 33% CO2, and 34% N2, with N2 used as an internal standard. The flow rate was maintained at 800 mL / min, and the reaction pressure was 0 MPa (gauge pressure). Sampling and analysis began after 60 min. The methane conversion rate, product selectivity, and hydrocarbon product distribution are shown in Table 1.

[0044] Example 5

[0045] 43.4 g of hydrated cerium nitrate (Ce(NO3)3·6H2O) and 43.8 g of citric acid were dissolved together in 150 mL of deionized water. The resulting solution was stirred at 80 °C until it became gel-like, and then placed in an oven at 120 °C for 24 h to obtain a porous foam-like structure. The pulverized powder was calcined in a muffle furnace at 600 °C for 4 h in an air atmosphere to obtain cerium oxide (CeO2) support. 0.32 g of lithium nitrate (LiNO3) was loaded onto CeO2 using an equal-volume impregnation method. The resulting sample was dried at 60 °C for 12 h and then calcined in a muffle furnace at 950 °C for 2 h in an air atmosphere. The obtained powdered catalyst was pressed into tablets and sieved to obtain 40-80 mesh particles, denoted as Li2O / CeO2.

[0046] 0.8g of Li₂O / CeO₂ catalyst was placed in the isothermal section of the reaction tube using quartz wool. A schematic diagram of the reactor is shown below. Figure 1 As shown in the figure. Under an argon atmosphere at a flow rate of 100 mL / min, the reactor temperature was increased from room temperature to 900 °C over 180 min. After pretreatment at this temperature for 60 min, the reaction gas was switched to: 64% CH4, 32% CO2, and 4% N2, with N2 used as an internal standard. The flow rate was maintained at 80 mL / min, and the reaction pressure was 0.8 MPa (gauge). Sampling and analysis began after 60 min. The methane conversion rate, product selectivity, and hydrocarbon product distribution are shown in Table 1.

[0047] Example 6

[0048] This embodiment examines the stability of the catalyst. First, the SrLaSmOx catalyst was prepared using the same method as in Example 3. Then, 1g of the SrLaSmOx catalyst was placed in the isothermal section of the reaction tube using silica wool. A schematic diagram of the reactor is shown below. Figure 1 As shown. Under an argon atmosphere at a flow rate of 100 mL / min, the reactor temperature was increased from room temperature to 900 °C over 180 min. After pretreatment at this temperature for 60 min, the reaction gas was switched to: 64% CH4, 32% CO2, and 4% N2, with N2 used as an internal standard. The flow rate was maintained at 100 mL / min, and the reaction pressure was atmospheric pressure. The reaction products were continuously analyzed to test the catalyst stability. The changes in methane conversion and hydrocarbon (HC) selectivity over time are shown in the figure. Figure 2 See the sample photos after stability testing. Figure 3 The fact that the sample remains white indicates the absence of significant carbon buildup. Thermogravimetric analysis of the samples before and after the stability test is shown below. Figure 4 The absence of CO2 signal detected by mass spectrometry indicates that no carbon was deposited in the sample after the reaction.

[0049] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0050] Table 1 Catalyst performance evaluation results

[0051]

Claims

1. A method for producing C2 hydrocarbons and benzene by coupling the oxidation of methane with carbon dioxide, characterized in that, Specifically, a mixture of methane and carbon dioxide is passed through a reactor containing a catalyst to produce C2 hydrocarbons and benzene, with carbon monoxide and water as byproducts. The method of using carbon dioxide to oxidize methane and couple to produce C2 hydrocarbons and benzene involves selectively controlling the C2 hydrocarbons and benzene by changing the type and composition of the catalyst and adjusting the reaction conditions. The reaction temperature for the carbon dioxide oxidation of methane coupling is 800–1100 °C; the reaction pressure is 0–1.0 MPa (gauge pressure); the molar ratio of methane to carbon dioxide in the reaction mixture is 6:1 to 1:1; and the total mass hourly space velocity (MHV) of the reaction mixture is 1 × 10⁻⁶. 3 ~1×10 7 ml·g -1 ·h -1 The reactor is a fixed-bed reactor; the catalyst is a composite catalyst composed of alkaline earth metal oxides and rare earth metal oxides, a composite catalyst composed of Na2WO4 and rare earth metal oxides, a composite catalyst composed of different rare earth metal oxides, or a composite catalyst composed of rare earth metal oxides and alkali metal oxides.

2. The method for producing C2 hydrocarbons and benzene by coupling methane with carbon dioxide oxidation according to claim 1, characterized in that, When a composite catalyst composed of alkaline earth metal oxides and rare earth metal oxides is used, the mass fraction of alkaline earth metal oxides in the composite catalyst is 0.1% to 8.5%; the mass hourly space velocity (HHSV) in the reaction conditions is in the range of 1 × 10⁻⁶. 4 ~1×10 7 ml·g -1 ·h -1 Meanwhile, when the reaction pressure is 0.5 to 1.0 MPa (gauge pressure), the selectivity of total hydrocarbon products is >60%; the alkaline earth metal oxides are magnesium oxide, calcium oxide, strontium oxide, or barium oxide, and the rare earth metal oxides are one or more of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, and yttrium oxide.

3. The method for producing C2 hydrocarbons and benzene by coupling methane with carbon dioxide oxidation according to claim 2, characterized in that, The mass fraction of magnesium oxide in the composite catalyst formed with the rare earth metal oxide is 0.1% to 4%; the mass fraction of calcium oxide in the composite catalyst formed with the rare earth metal oxide is 0.5% to 5%; the mass fraction of strontium oxide in the composite catalyst formed with the rare earth metal oxide is 1% to 6%; and the mass fraction of barium oxide in the composite catalyst formed with the rare earth metal oxide is 2% to 8.5%.

4. The method for producing C2 hydrocarbons and benzene by coupling methane oxidation with carbon dioxide according to claim 1, characterized in that, When using a composite catalyst composed of Na2WO4 and rare earth metal oxides, the mass fraction of Na2WO4 in the composite catalyst is 1%–8%; the mass hourly space velocity (HHSV) in the reaction conditions is in the range of 1 × 10⁻⁶. 4 ~1×10 7 ml·g -1 ·h -1 Simultaneously, when the reaction pressure is 0-0.5 MPa (gauge pressure), the C2 hydrocarbon selectivity in the hydrocarbon products reaches more than 50%; the rare earth metal oxide is one or more of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, and yttrium oxide.

5. The method for producing C2 hydrocarbons and benzene by coupling methane with carbon dioxide oxidation according to claim 1, characterized in that, When using a composite catalyst composed of different rare earth metal oxides, the mass space velocity range in the reaction conditions is 6 × 10⁻⁶. 3 ~1×10 7 ml·g -1 ·h -1 Simultaneously, when the reaction pressure is 0-0.2 MPa (gauge pressure), the molar fraction of C2 hydrocarbons in the hydrocarbon products reaches 92%; the rare earth metal oxides are two or more of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, and yttrium oxide.

6. The method for producing C2 hydrocarbons and benzene by coupling methane oxidation with carbon dioxide according to claim 5, characterized in that, The composite catalyst preferably has lanthanum oxide, cerium oxide, or samarium oxide as its main component.

7. The method for producing C2 hydrocarbons and benzene by coupling methane oxidation with carbon dioxide according to claim 1, characterized in that, When a composite catalyst composed of rare earth metal oxides and alkali metal oxides is used, the mass fraction of the alkali metal oxides in the composite catalyst is 0.1% to 7.5%; and the mass hourly space velocity (HHSV) under the reaction conditions is in the range of 1 × 10⁻⁶. 3 ~6×10 3 ml·g -1 ·h -1 Simultaneously, when the reaction pressure is 0-1.2 MPa (gauge pressure), the molar fraction of benzene in the hydrocarbon products reaches 33.6%; the rare earth metal oxide is one or more of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, and yttrium oxide; the alkali metal oxide is lithium oxide, sodium oxide, potassium oxide, rubidium oxide, or cesium oxide.

8. The method for producing C2 hydrocarbons and benzene by coupling methane with carbon dioxide oxidation according to claim 7, characterized in that, The mass fraction of lithium oxide in the composite catalyst formed with the rare earth metal oxide is 0.1% to 0.8%; the mass fraction of sodium oxide in the composite catalyst formed with the rare earth metal oxide is 0.2% to 2%; the mass fraction of potassium oxide in the composite catalyst formed with the rare earth metal oxide is 0.3% to 2.6%; the mass fraction of rubidium oxide in the composite catalyst formed with the rare earth metal oxide is 0.6% to 5%; and the mass fraction of cesium oxide in the composite catalyst formed with the rare earth metal oxide is 0.9% to 7.5%.

9. A method for producing C2 hydrocarbons and benzene by coupling methane with carbon dioxide oxidation according to any one of claims 2-8, characterized in that, The catalyst is prepared by the sol-gel method; the obtained catalyst is used after being directly or by mixing multiple components, pressing into tablets, and sieving.

10. A method for producing C2 hydrocarbons and benzene by coupling methane with carbon dioxide oxidation according to any one of claims 9, characterized in that, The complexing agent in the sol-gel method is one or more of the following: citric acid, ammonium citrate, maleic acid, oxalic acid, ammonium oxalate, ascorbic acid, ethanolamine, diethanolamine, and triethanolamine. Before the reaction, the mixture is heated to the reaction temperature under an inert gas atmosphere and then switched to the raw material gas for the reaction. The gas after the reaction is analyzed online by a combination of a thermal conductivity detector and a flame ionization detector in a gas chromatograph.

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