Study On Preparation Of Ni-based Mesoporous Catalysts And Methane Reforming Of Carbon Dioxide Performance

As one of the three major fossil energy sources,natural gas reserves are extremely abundant.As a chemical raw material,natural gas（main component methane（CH4））is currently mainly used in a series of important chemical products such as synthetic ammonia and methanol.With the long-term exploitation of petroleum resources and reserves becoming increasingly scarce,natural gas will certainly be the main carbon source for basic chemicals in the future.Nowadays,the chemical utilization of CH₄ mainly uses the indirect conversion method,which converts natural gas first into synthesis gas and then into other chemical products.The process of CH₄dry reforming（DRM）of CO₂ to syngas has significant advantages:（1）The H₂/CO ratio in the produced syngas is about 1,which can be directly used as an ideal raw material for deep conversion carbonyl synthesis and Fischer-Tropsch synthesis;（2）DRM is a reversible reaction with a large reaction heat,which can be used as an energy storage medium;（3）The main components of these two greenhouse gases（CH₄ and CO₂）are used as reactant at the same time,both from energy perspective and environmental perspective,have extremely Far-reaching significance.At present,the main problem faced by DRM is still the problem of catalyst surface carbon causing catalyst deactivation.Therefore,designing catalysts with good catalytic performance and carbon deposition resistance is a prerequisite for industrial application of DRM.In this paper,mesoporous NiO/MgO-ZrO₂,NiO/Al₂O₃ were selected as catalysts for DRM reactions.The catalyst performance was studied by DRM reactions.The phase structure and microstructure of the catalysts were analyzed by XRD,H₂-TPR,specific surface area and pore size distribution and TEM.SEM,Raman-Spectra and TG were used to analyze the carbon deposition of the catalyst after DRM reaction.The conclusion is as follows:1.Ni/MgO-ZrO₂catalyst prepared with P₁₂₃ as a surfactant has a typical mesoporous structure.The diameter of the pores is about 10 nm,and the specific surface area is 64.7 m²/g^-1.With different Ni loadings,the pore size distribution and specific surface area of the catalyst will change accordingly.10wt%NiO/MgO-ZrO₂ showed the best catalytic performance among the catalysts with different Ni contents.In the long-term stability test,the conversions rates of CH₄and CO₂ were 85%and 87%,the selectivity of H₂and CO were92%and 95%,respectively.After 60 hours,the conversion rates of CH₄ and CO₂ decreased to 82.0%and 84.2%.The selectivity of H₂ and CO dropped to 85%and 90%,respectively,indicating that the catalyst has excellent stability.After DRM,there were two types of carbon deposits on the catalyst surface,namely amorphous carbon and graphite carbon.After 20-hours of DRM testing,the carbon deposit on the surface of 10wt%NiO/MgO-ZrO₂ was about 6%.After 60 hours of DRM testing,the carbon deposition on the catalyst surface is about 21%weight loss.2.NiO/Al₂O₃ catalyst prepared with P₁₂₃ as a surfactant has a typical mesoporous structure.The pore size is about 9 nm,and the specific surface area is up to 283 m²/g.The pore size distribution is uniform.With different Ni content,the specific surface area and average pore size of the catalyst are changed accordingly.15wt%NiO/Al₂O₃ showed the best catalytic performance among catalysts with different Ni contents.The conversion rates of CH₄ and CO₂ were 82.7%and 83.1%,respectively,and the selectivity ratio of H₂ and CO was 0.84.20wt%NiO/Al₂O₃ lost its activity due to excessive carbon deposition after 8hours of DRM test.After the DRM test,there were two types of carbon deposits on the catalyst surface,namely amorphous carbon and graphite carbon.After 20-hours DRM test,the carbon deposition of 15wt%NiO/Al₂O₃ on the catalyst surface is about 12%weight loss.