Study On Hydrogenation Of CO₂ To Methane By Pyrolysis Ce-MOFs Supported Ru-Based Catalyst

Hydrogenation of CO₂ methanation can effectively utilize renewable carbon resources,alleviate the greenhouse effect,make up for the shortage of fossil fuels,promote the development of"low-carbon economy",and maintain the long-term sustainable development of society.In this paper,Ce-MOFs was used as the precursor to obtain Ce O₂ carrier through pyrolysis,and the influence of carrier properties on the catalytic performance of CO₂ hydrogenation methanation by supported Ru-based catalyst was explored.The specific research results are as follows:（1）Using Ce-MOFs（including Ce-BDC,Ce-MOF-808 and Ce-BTC）as precursors,the Ce O₂ carrier with specific topological structure and coordination environment was prepared by pyrolysis.Subsequently,the Ru/Ce O₂ catalyst was prepared by constant volume impregnation.The effects of the carrier properties on the hydrogenation of CO₂ to methanation of Ru/Ce O₂ catalyst were investigated,and the effects of the texture properties of Ce-MOFs precursor on the methanation of CO₂were compared.The results show that Ce-MOFs pyrolysis can form three-dimensional mesoporous structures,while retaining some MOFs texture properties.In addition,the Ru based catalyst prepared with Ce O₂ obtained from Ce-BDC pyrolysis as the support has the best low temperature conversion activity,because Ce O₂-B can form strong metal-carrier interaction with Ru metal nanoparticles,promote the dispersion of metal,but also inhibit the migration of active metal particles,and thus improve the catalytic efficiency.（2）The effect of Ce-MOFs pyrolysis temperature on Ru/Ce O₂ catalytic hydrogenation of CO₂ was investigated,and the effect of Ce-MOFs pyrolysis temperature on the morphology,pore structure,specific surface area and grain size of the carrier was investigated.The results show that high temperature pyrolysis can agglomerate Ce nodes,collapse MOFs skeleton and gradually transform into stacked CO₂ particles.The proper pyrolysis temperature（400℃）promoted the formation of more Ce³⁺,and made the catalyst have better low-temperature reduction performance,more abundant oxygen vacancies,more alkaline sites and better CO₂ adsorption capacity,thus improving the performance of CO₂ methanation.（3）Ce O₂ was prepared by different methods（Ce-BDC pyrolysis,precipitation and cerium nitrate pyrolysis）,and Ru/Ce O₂ catalyst was prepared by equivolumetric impregnation method using Ce O₂ as the support.The effects of different preparation methods on the catalytic CO₂ methanation performance of the three catalysts were investigated,and the effects of carrier preparation methods on the morphology and the effects of Ce node in MOF and traditional Ce O₂ on the CO₂ methanation performance were compared.The results showed that the regular octahedral shape of Ce-BDC precursor had a positive effect on the adsorption of CO₂.The Ce O₂ support obtained by Ce-BDC pyrolysis retains the regular octahedral structure of the precursor,and has a large specific surface area and a large average grain size.However,the specific surface area and pore volume of Ce O₂ in precipitation and cerium nitrate pyrolysis methods are small,which is not conducive to the diffusion of reactants and products.At the same time,the catalyst itself is seriously agglomerated,which will weaken the interaction between Ru and the carrier,thus reducing the catalytic activity of the catalyst.