A composite catalyst with high resistance to coking in methane dry gas reforming and its application

Abstract

This invention discloses a composite catalyst with high resistance to coking in methane dry gas reforming. The composite catalyst is composed of three components: a supported nickel-based catalyst, a nitrogen-doped carbon-supported molybdenum catalyst, and an inert support. The invention also discloses its application in methane dry gas reforming. After hydrogen reduction, the composite catalyst exhibits excellent activity and stability under high space velocity reaction conditions in methane dry gas reforming, overcoming the deficiency of Ni-based catalysts in methane dry gas reforming that are prone to coking and deactivation under high-temperature conditions.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a composite catalyst for the reforming reaction of methane dry gas with high resistance to carbon deposition and its application. Background Technology

[0002] Methane dry gas reforming is an effective way to simultaneously utilize methane and carbon dioxide, two greenhouse gases. The resulting syngas (a mixture of hydrogen and carbon monoxide) can be directly used as a feedstock for carbonyl synthesis, hydroformylation, and Fischer-Tropsch synthesis, offering both economic and environmental benefits. A crucial step in realizing methane dry gas reforming technology is the preparation of a highly efficient and inexpensive catalyst. Ni-based catalysts offer a perfect balance between economic efficiency and catalytic activity, and are considered the most ideal catalysts. However, this process has not yet been industrialized, with the bottleneck being the high temperatures leading to coking of Ni-based catalysts and sintering of active components.

[0003] To address the above issues, researchers have conducted extensive research and proposed various solutions. Bimetallic catalysts, due to their synergistic effect, often exhibit superior catalytic performance compared to monometallic catalysts. Previous studies have shown that although Mo itself has low activity in dry gas reforming, introducing Mo species into Ni-based catalysts can significantly modulate their reaction performance, particularly enhancing catalyst stability. Research indicates that the strong interaction between the partially filled d orbitals of Mo₂C and C atoms helps disperse and migrate carbon species on the adsorption surface. This interaction reduces the deposition and aggregation of carbon species on the catalyst surface, thereby effectively inhibiting coke formation. The mechanism of action of the Ni-Mo dual-active-site system in dry gas reforming is: metallic Ni and MoO₂... x C y These sites serve as activation sites for CH4 and CO2, respectively, while the carbon produced by CH4 cracking on metallic Ni is activated by MoO. x with MoO x C y Carbon removal is achieved through a cycle. The design of bimetallic sites is crucial for maintaining the equilibrium of this system. Studies by da Silva et al. on Ni-Mo systems on different supports revealed that, compared to SiO2 and Al2O3, catalysts on SiC exhibited superior performance and minimal filamentous carbon within a wider Ni:Mo ratio range. The authors suggest that the strong interaction between Ni and SiC is beneficial for suppressing Ni component migration and propose that the close contact between Ni and Mo2C is a key factor in forming a carbon removal cycle (see Journal of Catalysis, 2019, 375, 507-518). Furthermore, Ishikawa et al., in their study of chemical looping dry gas reforming using Ni-(α-MoC) / Al2O3 as an oxygen storage material for periodic reduction and re-oxidation cycles, found that the MoC generated in situ during the reaction... x Oy and Ni-MoC x O y The interface significantly reduces the CH4 activation temperature and maintains extremely high activity and stability even after 1140 cycles (see Chem, 2023, 9, 102-116). It should be noted that previous studies have generally followed the approach of constructing tightly contacted Ni-Mo active sites as a starting point for overcoming the coking problem. However, establishing a delicate balance between coking and decoking on Ni-Mo bifunctional sites remains challenging. To date, no Ni-Mo catalytic system possessing both high activity and high resistance to coking has been reported. Summary of the Invention

[0004] The purpose of this invention is to provide a composite catalyst with high resistance to carbon deposition in methane dry gas reforming and its application, in order to solve the problem that Ni-based catalysts used in current methane dry gas reforming reactions are prone to carbon deposition, leading to rapid catalyst deactivation.

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

[0006] A composite catalyst for the reforming reaction of methane dry gas with high resistance to carbon deposition is provided. The composite catalyst is composed of three components: a supported nickel-based catalyst, a nitrogen-doped carbon-supported molybdenum catalyst, and an inert support.

[0007] Furthermore, in the supported nickel-based catalyst, the active component is Ni, existing in elemental or / and oxide form; or the first active component is Ni, existing in elemental or / and oxide form, and the second active component includes one or more of Zn, Mn, Fe, La, In, and Ga, existing in elemental or / and oxide form; the support includes activated alumina, magnesium oxide, silicon dioxide, or zirconium oxide.

[0008] Furthermore, in the supported nickel-based catalyst, the mass fraction of Ni is 5-40%.

[0009] Furthermore, in the nitrogen-doped carbon-supported molybdenum catalyst, the active component is Mo, which exists in the form of oxides and / or carbides and / or carbon oxides; the support is nitrogen-doped carbon.

[0010] Furthermore, in the nitrogen-doped carbon-supported molybdenum catalyst, the mass fraction of Mo is 5-40%.

[0011] Furthermore, the nitrogen in the nitrogen-doped carbon has a nitrogen mass fraction of 0.5% to 9%.

[0012] Furthermore, the inert carrier includes activated alumina, silicon dioxide, or zirconium oxide.

[0013] Furthermore, in the composite catalyst, the mass ratio of the supported nickel-based catalyst to the nitrogen-doped carbon-supported molybdenum catalyst is 0.5 to 5:1, and the mass fraction of the inert support is 10% to 80%.

[0014] When the composite catalyst is compounded, the three components of supported nickel-based catalyst, nitrogen-doped carbon-supported molybdenum catalyst and inert support are mixed and ground evenly in proportion, and then formed by powder pressing or extrusion. The powder is crushed and sieved to obtain 20-40 mesh for use in the reaction.

[0015] The above-mentioned high-carbon-resistant composite catalyst for methane dry gas reforming is applied in the methane dry gas reforming reaction. In application, the composite catalyst is loaded into a fixed-bed reactor. First, the composite catalyst is reduced in situ with hydrogen. Then, a mixture of methane and carbon dioxide is introduced into the fixed-bed reactor for gas-solid phase reaction to obtain syngas.

[0016] Furthermore, the reduction conditions are as follows: hydrogen flow rate of 30–100 ml / min, reduction temperature of 400–800 °C, reduction time of 3–12 h, and reduction pressure of atmospheric pressure;

[0017] The reaction conditions were as follows: the molar ratio of methane to carbon dioxide in the gas mixture was 0.8–1.2:1, and the gas hourly space velocity (GHSV) was 36,000–144,000 mL·g. cat -1 ·h -1 The reaction temperature is 750–900℃, and the reaction pressure is atmospheric pressure.

[0018] The beneficial effects of this invention are:

[0019] This invention discloses a composite catalyst composed of a supported nickel-based catalyst, a nitrogen-doped carbon-supported molybdenum catalyst, and an inert support. After hydrogen reduction, this catalyst exhibits excellent activity and stability under high space velocity conditions in methane dry gas reforming, overcoming the deficiency of Ni-based catalysts in methane dry gas reforming that are prone to coking and deactivation under high-temperature conditions. Compared to the corresponding single Ni-based catalyst, this composite catalyst has significant performance advantages, specifically in that it can greatly improve the catalyst's resistance to coking and extend its service life while maintaining comparable methane and carbon dioxide conversion rates.

[0020] The innovation of this composite catalyst lies in proposing a strategy of dispersing Ni and Mo active components on different supports, particularly the first-time proposal to disperse Mo on nitrogen-doped carbon. This strategy of separating the two active components, Ni and Mo, is entirely different from previous approaches that synthesize Ni-Mo active components with close contact on the same support or directly disperse Ni on a Mo2C support. Because the Mo active component on the nitrogen-doped carbon support possesses excellent carbonization capabilities, it can promptly remove coke deposits on the surface of the Ni active component during the methane dry gas reforming reaction, while simultaneously preventing the oxidative deactivation of the Mo active component itself, thus maintaining both high activity and high stability. Attached Figure Description

[0021] Figure 1 It is Ni / ZrO2-MnO x Stability test of ZnO‖Mo / NC-4‖ZrO2 catalyst in methane dry gas reforming reaction for 250 h (Example 11). Detailed Implementation

[0022] The present invention will be further explained below with reference to embodiments and accompanying drawings. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0023] A composite catalyst for the reforming reaction of methane dry gas with high resistance to carbon deposition is provided. The composite catalyst is composed of three components: a supported nickel-based catalyst, a nitrogen-doped carbon-supported molybdenum catalyst, and an inert support.

[0024] The supported nickel-based catalyst is prepared by impregnation, ion exchange, or co-precipitation methods, with Ni as the active component, existing in elemental or / and oxide form; or the first active component is Ni, existing in elemental or / and oxide form, and the second active component includes one or more of Zn, Mn, Fe, La, In, and Ga, existing in elemental or / and oxide form; the support includes activated alumina, magnesium oxide, silica, or zirconium oxide. In the supported nickel-based catalyst, the mass fraction of Ni is 5–40%.

[0025] The nitrogen-doped carbon-supported molybdenum catalyst (Mo / NC catalyst) is prepared by impregnation method, with Mo as the active component, existing in the form of oxides and / or carbides and / or carbon oxides; the support is nitrogen-doped carbon. In the nitrogen-doped carbon-supported molybdenum catalyst, the mass fraction of Mo is 5-40%. In the nitrogen-doped carbon, the mass fraction of nitrogen is 0.5-9%.

[0026] The inert carrier includes activated alumina, silicon dioxide, or zirconium oxide.

[0027] In the composite catalyst, the mass ratio of the supported nickel-based catalyst to the nitrogen-doped carbon-supported molybdenum catalyst is 0.5 to 5:1, and the mass fraction of the inert support is 10% to 80%.

[0028] The composite catalyst is prepared by mixing and grinding three components—supported nickel-based catalyst, nitrogen-doped carbon-supported molybdenum catalyst, and inert support—in a certain proportion, then forming the catalyst into tablets or extrusion strips, and finally crushing and sieving it to obtain a 20-40 mesh sample for use in the reaction.

[0029] The above-mentioned high-carbon-resistant composite catalyst for methane dry gas reforming is applied in the methane dry gas reforming reaction. In application, the composite catalyst is loaded into a fixed-bed reactor. First, the composite catalyst is reduced in situ with hydrogen. Then, a mixture of methane and carbon dioxide is introduced into the fixed-bed reactor for a gas-solid phase reaction to obtain syngas. The reduction conditions are: hydrogen flow rate of 30–100 ml / min, reduction temperature of 400–800℃, reduction time of 3–12 h, and reduction pressure at atmospheric pressure; the reaction conditions are: a methane to carbon dioxide molar ratio of 0.8–1.2:1 in the mixed gas, and a gas space velocity of 36000–144000 mL·g. cat -1 ·h -1 The reaction temperature is 750–900℃, and the reaction pressure is atmospheric pressure.

[0030] In each embodiment, the conversion rate and selectivity are calculated using the following formulas (all units of measurement are molar amounts):

[0031] Methane conversion rate = (methane in feed gas – methane in product) / methane in feed gas × 100%

[0032] Carbon dioxide conversion rate = (Carbon dioxide in feed gas – Carbon dioxide in product) / Carbon dioxide in feed gas × 100%

[0033] Hydrogen to carbon monoxide ratio = Hydrogen in products / Carbon monoxide in products

[0034] The qualitative and quantitative analysis of the raw materials and products before and after the methane dry gas reforming reaction was performed on an Agilent gas chromatograph 7890, and the component analysis was performed using a TDX-01 packed column with a Porapak Q and a TCD detector.

[0035] Example 1

[0036] Ni / ZrO2 catalyst: 50g Zr(NO3)4·5H2O was added to a flask containing 290g deionized water. The flask was placed in a water bath at 30℃, and stirring was started. Then, a 2mol / L sodium hydroxide aqueous solution was added dropwise. When the pH of the solution reached 9, stirring was stopped, and the water bath temperature was increased to 90℃ for aging for another 4 hours. The solution was then filtered and washed with deionized water until neutral to obtain a filter cake. The filter cake was dried at 110℃ for 16 hours and then calcined in a muffle furnace at 450℃ for 4 hours to obtain a ZrO2 support. A 1mol / L nickel nitrate aqueous solution was prepared and used to impregnate the ZrO2 support overnight. The impregnation was then dried at 110℃ for 16 hours and calcined in a muffle furnace at 400℃ for 4 hours to obtain Ni / ZrO2 with a Ni content of 10wt%.

[0037] Mo / NC-1 catalyst: 40g of polyaniline was placed in a tube furnace and calcined at 800℃ for 4h under nitrogen protection to obtain nitrogen-doped carbon, denoted as NC-1 support. Elemental analysis showed that its nitrogen mass fraction was 9%. 7.2g of ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O) 24 Dissolve 4H2O in 20mL of deionized water, then add 10g of NC-1, stir and impregnate at room temperature for 0.5h, then dry in an oven at 100℃ for 12h, then transfer the sample to a tube furnace and calcine at 800℃ for 5h under a nitrogen atmosphere to obtain Mo / NC-1 with a Mo content of 30wt%.

[0038] Ni / ZrO2‖Mo / NC-1‖ZrO2 catalyst: Ni / ZrO2, Mo / NC-1 and ZrO2 in a mass ratio of 4:4:2 are mixed, ground evenly, and then pressed into tablets. The tablets are crushed, sieved and 20-40 mesh are used for reaction performance evaluation.

[0039] The catalyst was placed in a quartz fixed-bed reactor (10 mm inner diameter) and first reduced and activated at 800 °C for 3 h under a pure hydrogen atmosphere (flow rate 30 ml / min) at atmospheric pressure. Then, the temperature was lowered to 750 °C, and a mixture of methane and carbon dioxide in an equimolar ratio was introduced, with a gas hourly space velocity (GHSV) set at 144,000 mL·g⁻¹. cat -1 ·h -1 The reaction pressure was atmospheric pressure, and the catalyst activity and stability were evaluated.

[0040] Example 2

[0041] Ni / ZrO2-MnO xCatalyst: 50g Zr(NO3)4·5H2O and 41.86g of 50wt% Mn(NO3)2 aqueous solution were added to a flask containing 290g of deionized water. The flask was placed in a water bath at 30℃, and stirring was started. Then, a 2mol / L sodium hydroxide aqueous solution was added dropwise. When the pH of the solution reached 9, stirring was stopped, and the water bath temperature was increased to 90℃ for aging for another 4 hours. The solution was then filtered and washed with deionized water until neutral to obtain a filter cake. The filter cake was dried at 110℃ for 16 hours and then calcined in a muffle furnace at 450℃ for 4 hours to obtain ZrO2-MnO. x Carrier. Prepare a 1 mol / L nickel nitrate aqueous solution and impregnate the ZrO2-MnO prepared above. x The carrier was impregnated overnight, dried at 110°C for 16 hours, and then calcined in a muffle furnace at 400°C for 4 hours to obtain Ni / ZrO2-MnO with a Ni content of 10 wt%. x .

[0042] Mo / NC-2 catalyst: NC-2 was synthesized according to the NC-1 support synthesis method in Example 1. The calcination temperature of polyaniline was changed to 1000℃, and the nitrogen mass fraction of NC-2 was 4%. The Mo / NC-2 catalyst was synthesized according to the Mo / NC-1 catalyst method, only replacing NC-1 with NC-2.

[0043] Ni / ZrO2-MnO x Mo / NC-2 ZrO2 catalyst: Ni / ZrO2-MnO2 with a mass ratio of 4:4:2 x Mo / NC-2 and ZrO2 were mixed and ground evenly, then compressed into tablets, crushed and sieved, and a sample of 20-40 mesh was used for reaction performance evaluation. Activation and reaction conditions were the same as in Example 1.

[0044] Example 3

[0045] Ni / ZrO2-ZnO catalyst: 50g Zr(NO3)4·5H2O and 41.86g Zn(NO3)2·6H2O were added to a flask containing 290g deionized water. The flask was placed in a water bath at 30℃, and stirring was started. Then, a 2mol / L sodium hydroxide aqueous solution was added dropwise. When the pH of the solution reached 9, stirring was stopped, and the water bath temperature was increased to 90℃ for aging for another 4 hours. The solution was then filtered and washed with deionized water until neutral to obtain a filter cake. The filter cake was dried at 110℃ for 16 hours and then calcined in a muffle furnace at 450℃ for 4 hours to obtain the ZrO2-ZnO support. Prepare a 1 mol / L nickel nitrate aqueous solution, impregnate the ZrO2-ZnO support prepared above, impregnate overnight, dry at 110℃ for 16 h, and then calcine at 400℃ in a muffle furnace for 4 h to obtain Ni / ZrO2-ZnO with a Ni content of 10 wt%.

[0046] Mo / NC-3 catalyst: NC-3 was synthesized according to the NC-1 support synthesis method in Example 1. The calcination temperature of polyaniline was changed to 1500℃, and the nitrogen mass fraction of NC-3 was 0.5%. The Mo / NC-3 catalyst was synthesized according to the Mo / NC-1 catalyst method, only replacing NC-1 with NC-3.

[0047] Ni / ZrO2-ZnO‖Mo / NC-3‖ZrO2 catalyst: Ni / ZrO2-ZnO, Mo / NC-3 and ZrO2 in a mass ratio of 4:4:2 were mixed, ground evenly, and then pressed into tablets. The tablets were crushed, sieved, and 20-40 mesh samples were used for reaction performance evaluation. Activation and reaction conditions were the same as in Example 1.

[0048] Example 4

[0049] Ni / ZrO2-MnO x -ZnO catalyst: 50g Zr(NO3)4·5H2O, 41.86g 50wt% Mn(NO3)2 aqueous solution, and 41.86g Zn(NO3)2·6H2O were added to a flask containing 290g deionized water. The flask was placed in a water bath at 30℃, and stirring was started. Then, a 2mol / L sodium hydroxide aqueous solution was added dropwise. When the pH of the solution reached 9, stirring was stopped, and the water bath temperature was increased to 90℃ for aging for 4 hours. The solution was then filtered and washed with deionized water until neutral to obtain a filter cake. The filter cake was dried at 110℃ for 16 hours and then calcined in a muffle furnace at 450℃ for 4 hours to obtain ZrO2-MnO. x -ZnO support. Prepare a 1 mol / L nickel nitrate aqueous solution and impregnate the ZrO2-MnO prepared above. x -ZnO support, impregnated overnight, dried at 110℃ for 16 h, and then calcined in a muffle furnace at 400℃ for 4 h to obtain Ni / ZrO2-MnO with a Ni content of 10 wt%. x -ZnO catalyst.

[0050] Mo / NC-4 catalyst: NC-4 was synthesized according to the NC-1 support synthesis method in Example 1. The calcination temperature of polyaniline was changed to 1200℃, and the nitrogen mass fraction of NC-4 was 1%. The Mo / NC-4 catalyst was synthesized according to the Mo / NC-1 catalyst method, only replacing NC-1 with NC-4.

[0051] Ni / ZrO2-MnO x -ZnO‖Mo / NC-4‖ZrO2 catalyst: Ni / ZrO2-MnO with a mass ratio of 4:4:2 xZnO, Mo / NC-4, and ZrO2 were mixed and ground evenly, then compressed into tablets, crushed, sieved, and a 20-40 mesh sample was taken for reaction performance evaluation. Activation and reaction conditions were the same as in Example 1.

[0052] Example 5

[0053] Ni / Al2O3 catalyst: The Ni / Al2O3 catalyst was prepared according to the Ni / ZrO2 catalyst synthesis method in Example 1. The ZrO2 support was replaced with active Al2O3.

[0054] Ni / Al2O3‖Mo / NC-1‖Al2O3 catalyst: Ni / Al2O3, Mo / NC-1 and activated Al2O3 in a mass ratio of 3:3:4 were mixed, ground evenly, and then extruded into strips. The strips were crushed, sieved, and 20-40 mesh were used for reaction performance evaluation. The reaction temperature was changed to 850℃, and the other activation and reaction conditions were the same as in Example 1.

[0055] Example 6

[0056] Ni / MgO catalyst: The Ni / MgO catalyst was prepared according to the Ni / ZrO2 catalyst synthesis method in Example 1. The ZrO2 support was replaced with MgO.

[0057] Ni / MgO‖Mo / NC-3‖Al2O3 catalyst: Ni / MgO, Mo / NC-3 and activated Al2O3 in a mass ratio of 3:3:4 were mixed, ground evenly, and then extruded into strips. The strips were crushed, sieved, and 20-40 mesh were used for reaction performance evaluation. The reaction temperature was changed to 900℃, and the other activation and reaction conditions were the same as in Example 1.

[0058] Example 7

[0059] Ni / SiO2 catalyst: The Ni / SiO2 catalyst was prepared according to the Ni / ZrO2 catalyst synthesis method in Example 1. The ZrO2 support was replaced with SiO2.

[0060] Ni / SiO2‖Mo / NC-2‖SiO2 catalyst: Ni / SiO2, Mo / NC-2 and SiO2 in a mass ratio of 4:4:2 were mixed, ground evenly, and then pressed into tablets. The tablets were crushed, sieved, and a sample of 20-40 mesh was used for reaction performance evaluation. The reaction temperature was changed to 800℃, and the other activation and reaction conditions were the same as in Example 1.

[0061] Example 8

[0062] Ni-Fe-La / Al2O3 catalyst: Prepare 1 mol / L nickel nitrate aqueous solution, 0.5 mol / L iron nitrate aqueous solution and 1 mol / L lanthanum nitrate aqueous solution, and impregnate the active alumina support together overnight. Dry at 110℃ for 16 h, and then calcine in a muffle furnace at 400℃ for 4 h to obtain Ni-Fe-La / Al2O3 catalyst with Ni content of 10 wt%, Fe content of 2 wt%, and La content of 4 wt%.

[0063] Ni-Fe-La / Al2O3‖Mo / NC-2‖Al2O3 catalyst: Ni-Fe-La / Al2O3, Mo / NC-2, and activated Al2O3 in a mass ratio of 3:3:4 were mixed, ground evenly, and then extruded into strips. The strips were crushed, sieved, and 20-40 mesh were used for reaction performance evaluation. The reaction temperature was changed to 850℃, and the other activation and reaction conditions were the same as in Example 1.

[0064] Example 9

[0065] Ni-In / Al2O3 catalyst: Prepare 1 mol / L nickel nitrate aqueous solution and 1 mol / L indium nitrate aqueous solution, impregnate the active alumina support together, impregnate overnight, dry at 110℃ for 16 h, and then calcine in a muffle furnace at 400℃ for 4 h to obtain Ni-In / Al2O3 catalyst with Ni content of 10 wt% and In content of 4 wt%.

[0066] Ni-In / Al2O3‖Mo / NC-3‖Al2O3 catalyst: Ni-In / Al2O3, Mo / NC-3 and activated Al2O3 in a mass ratio of 3:3:4 were mixed, ground evenly, and then extruded into strips. The strips were crushed, sieved, and 20-40 mesh were used for reaction performance evaluation. The reaction temperature was changed to 850℃, and the other activation and reaction conditions were the same as in Example 1.

[0067] Example 10

[0068] Ni-Ga / Al2O3 catalyst: Prepare 1 mol / L nickel nitrate aqueous solution and 1 mol / L gallium nitrate aqueous solution, impregnate the active alumina support together, impregnate overnight, dry at 110℃ for 16 h, and then calcine in a muffle furnace at 400℃ for 4 h to obtain Ni-Ga / Al2O3 catalyst with Ni content of 10 wt% and Ga content of 4 wt%.

[0069] Ni-Ga / Al2O3‖Mo / NC-3‖Al2O3 catalyst: Ni-Ga / Al2O3, Mo / NC-3 and activated Al2O3 in a mass ratio of 3:3:4 were mixed, ground evenly, and then extruded into strips. The strips were crushed, sieved, and 20-40 mesh were used for reaction performance evaluation. The reaction temperature was changed to 850℃, and the other activation and reaction conditions were the same as in Example 1.

[0070] Example 11

[0071] Ni / ZrO2-MnO x Long-term stability test of the ZnO‖Mo / NC-4‖ZrO2 catalyst (prepared in Example 4). Activation conditions were the same as in Example 1. Reaction conditions: temperature 850℃, equimolar ratio of methane and carbon dioxide as raw materials, and gas hourly space velocity set at 36000 mL·g⁻¹. cat -1 ·h -1 The reaction pressure is atmospheric pressure.

[0072] Comparative Example 1

[0073] The catalyst in Example 1 was replaced with Ni / ZrO2‖ZrO2 with a mass ratio of 6:4, while the other conditions remained unchanged.

[0074] Comparative Example 2

[0075] The catalyst in Example 2 was replaced with Ni / ZrO2-MnO at a mass ratio of 6:4. x ||ZrO2, with all other conditions remaining unchanged.

[0076] Comparative Example 3

[0077] The catalyst in Example 3 was replaced with Ni / ZrO2-ZnO‖ZrO2 at a mass ratio of 6:4, while the other conditions remained unchanged.

[0078] Comparative Example 4

[0079] The catalyst in Example 4 was replaced with Ni / ZrO2-MnO at a mass ratio of 6:4. x -ZnO‖ZrO2, with all other conditions remaining unchanged.

[0080] Comparative Example 5

[0081] The catalyst in Example 5 was replaced with Ni / Al2O3‖Al2O3 at a mass ratio of 3:7, while the other conditions remained unchanged.

[0082] Comparative Example 6

[0083] The catalyst in Example 6 was replaced with Ni / MgO‖Al2O3 at a mass ratio of 3:7, while the other conditions remained unchanged.

[0084] Comparative Example 7

[0085] The catalyst in Example 7 was replaced with Ni / SiO2‖SiO2 at a mass ratio of 4:6, while the other conditions remained unchanged.

[0086] Comparative Example 8

[0087] The catalyst in Example 8 was replaced with Ni-Fe-La / Al2O3‖Al2O3 at a mass ratio of 3:7, while the other conditions remained unchanged.

[0088] Comparative Example 9

[0089] The catalyst in Example 9 was replaced with Ni-In / Al2O3‖Al2O3 at a mass ratio of 3:7, while the other conditions remained unchanged.

[0090] Comparative Example 10

[0091] The catalyst in Example 10 was replaced with Ni-Ga / Al2O3‖Al2O3 at a mass ratio of 3:7, while the other conditions remained unchanged.

[0092] Comparative Example 11

[0093] Ni-Mo / Al2O3 catalyst: A 1 mol / L nickel nitrate aqueous solution and a 2 mol / L ammonium heptamolybdate aqueous solution were prepared and co-impregnated onto an activated alumina support. The impregnation was carried out overnight, dried at 110°C for 16 h, and then calcined in a muffle furnace at 400°C for 4 h to obtain a Ni-Mo / Al2O3 catalyst with a Ni content of 10 wt% and a Mo content of 30 wt%. The activation and reaction conditions were the same as in Example 1.

[0094] The reaction performance results of the catalysts in the dry reforming of methane in each embodiment and comparative example are shown in Table 1 and Figure 1 As shown.

[0095] Table 1. Results of catalyst performance in methane dry gas reforming in each example and comparative example.

[0096]

[0097]

[0098] Comparative Examples 1-10 show that the conversion rates of both methane and carbon dioxide decreased when different types of supported Ni-based catalysts were used alone, indicating varying degrees of catalyst deactivation. Conversely, the novel catalysts obtained by combining different types of supported Ni-based catalysts with Mo / NC catalysts in Examples 1-10 exhibited an increasing activity trend in the methane dry gas reforming reaction, demonstrating that the presence of Mo / NC catalysts can significantly enhance the catalyst's resistance to coking, thereby improving its stability.

[0099] Comparative Example 11 shows that when Ni and Mo are simultaneously loaded onto the active alumina support, the reactivity is much lower than that of Ni / Al2O3, thus failing to achieve both high activity and high stability. This further confirms the role of NC in the composite catalytic system.

[0100] As can be seen from Example 11, Ni / ZrO2-MnO x The ZnO|Mo / NC-4|ZrO2 composite catalyst exhibits an induction period in the methane dry gas reforming reaction, followed by a long-term stable activity, demonstrating the excellent anti-coking performance and great application potential of this novel catalytic system.

Claims

1. A composite catalyst for the reforming reaction of methane dry gas with high resistance to carbon deposition, characterized in that, The composite catalyst is composed of three components: a supported nickel-based catalyst, a nitrogen-doped carbon-supported molybdenum catalyst, and an inert support. In the supported nickel-based catalyst, the active component is Ni, existing in elemental or / and oxide form; or the first active component is Ni, existing in elemental or / and oxide form, and the second active component includes one or more of Zn, Mn, Fe, La, In, and Ga, existing in elemental or / and oxide form; the support includes activated alumina, magnesium oxide, silicon dioxide, or zirconium oxide. In the nitrogen-doped carbon-supported molybdenum catalyst, the active component is Mo, which exists in the form of oxides and / or carbides and / or carbon oxides; the support is nitrogen-doped carbon.

2. The composite catalyst for high resistance to coking in methane dry gas reforming according to claim 1, characterized in that, In the supported nickel-based catalyst, the mass fraction of Ni is 5-40%.

3. The composite catalyst for high resistance to coking in methane dry gas reforming according to claim 1, characterized in that, In the nitrogen-doped carbon-supported molybdenum catalyst, the mass fraction of Mo is 5-40%.

4. The composite catalyst for high resistance to coking in methane dry gas reforming according to claim 1, characterized in that, The nitrogen-doped carbon contains nitrogen at a mass fraction of 0.5-9%.

5. The composite catalyst for high resistance to coking in methane dry gas reforming according to claim 1, characterized in that, The inert carrier includes activated alumina, silicon dioxide, or zirconium oxide.

6. The composite catalyst for high resistance to coking in methane dry gas reforming according to claim 1, characterized in that, In the composite catalyst, the mass ratio of the supported nickel-based catalyst to the nitrogen-doped carbon-supported molybdenum catalyst is 0.5~5:1, and the mass fraction of the inert support is 10%~80%. When the composite catalyst is compounded, the three components of supported nickel-based catalyst, nitrogen-doped carbon-supported molybdenum catalyst and inert support are mixed and ground evenly in proportion, and then formed by powder compression or extrusion, crushed and sieved to obtain 20-40 mesh for reaction.

7. The application of the high-coking-resistant composite catalyst for methane dry gas reforming according to any one of claims 1-6 in the methane dry gas reforming reaction, characterized in that, In application, the composite catalyst is loaded into a fixed-bed reactor. First, the composite catalyst is reduced in situ with hydrogen. Then, a mixture of methane and carbon dioxide is introduced into the fixed-bed reactor for a gas-solid phase reaction to obtain syngas.

8. The application according to claim 7, characterized in that, The reduction conditions are: hydrogen flow rate of 30~100mL / min, reduction temperature of 400~800℃, reduction time of 3~12h, and reduction pressure of atmospheric pressure; The reaction conditions were as follows: the molar ratio of methane to carbon dioxide in the gas mixture was 0.8–1.2:1, and the space velocity of the gas mixture was 36,000–144,000 mL·g. cat -1 ·h -1 The reaction temperature is 750~900℃ and the reaction pressure is atmospheric pressure.

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