Study On The Effect Of Pore Channel And Morphology Control Of Support On The Catalytic Performance Of Ni-based Catalysts For CO₂ Methanation

In the context of rapid industrial development,the burning of a large number of fossil fuels emits much carbon dioxide,causing global warming,sea level rise and other environmental problems.According to reports,global carbon dioxide emissions will be approximately 34 billion tons in 2020.Therefore,exploring the ways for resource utilization of carbon dioxide has become a research hotspot in recent years.Among them,CO₂methanation reaction shows the advantages of fast speed,less pollution,and low production cost,etc.Therefore,it has important strategic significance in realizing the recycling of carbon resources.Ni-based catalysts are suitable for CO₂methanation reaction due to their relatively low cost and high conversion rate under constant temperature conditions.However,carbon deposition and metal sintering during the reaction limit its feasibility in large-scale industrial applications.Therefore,it is necessary to explore ways to improve the low-temperature activity and sintering resistance of Ni-based catalysts.This article starts with the factors that affect the activity of catalysts for CO₂methanation,and focuses on the development of catalysts with excellent low-temperature activity and resistance to sintering,with supports,active centers and additives as the research direction,laying the foundation for the realization of the industrialization of carbon dioxide hydrogenation to methane.The focus of this article is on the pore structure and morphology of the support and the effects of rare earth additives(Pr,Sm,Ce,La)on the catalytic performance of Ni-based catalysts.The specific research content is as follows:1.The fibrous silica microspheres are prepared by the microemulsion hydrothermal method and used as the support of the Ni-based catalyst for the CO₂methanation reaction.In the meanwhile,the effects of Ni loadings on the activities of catalysts are investigated.Studies have shown that the open pore structure of the fibrous silica microsphere is beneficial to the high content of active metal Ni.In addition,the N₂adsorption-desorption characterization(BET)indicates that the support provides the large accessible surface area for the Ni species,which is beneficial to promote the uniform distribution of the active metal and increase the reaction rate.In the meanwhile,the catalyst with the 20 wt.%Ni loadings exhibits the highest catalytic activity.2.Ni-based catalysts doped with rare earth additives are prepared by co-impregnation method and the catalysts are systematically characterized by transmission electron microscopy characterization(TEM),X-ray diffraction characterization(XRD),hydrogen temperature programmed reduction test(H₂-TPR),etc.Studies have found that adding different rare earth metal oxides can significantly improve the interaction between the active metal and support,adjust the distribution of reactants and inhibit side reactions.In addition,the in-situ diffused reflectance infrared fourier transform spectroscopy(DRIFTS)results show that Ni-based catalysts doped with Sm₂O₃additives produce carbonates faster than other catalysts.Therefore,this series of catalysts perform excellent activity under low temperature.3.Ni-based catalysts supported by cerium oxides with different morphologies are prepared by the impregnation method to explore the influence of the morphological effect of supports on the catalytic performances of catalysts for CO₂methanation.Studies have found that cerium oxides with different morphologies will be exposed to different crystal faces,which may affect the metal-support interactions,reducing abilities,and oxygen vacancy formation of the catalysts,thereby changing the catalytic performances of catalysts.Among them,5Ni/NPS shows the best catalytic performance due to the high oxygen vacancy concentration and strong adsorption capacity.