Effect Of Cu/CeO₂ Catalyst On CO₂ Hydrogenation To Methano

In recent years,the excessive emissions of CO₂ from human production and living have caused increasingly serious climatic and environmental problems,which are harmful to the environment and the physical and mental health of the people on which human beings depend.One of the options for the resourceful use of CO₂ is the hydrogenation of CO₂ to methanol,where catalysts prepared with CeO₂ as a carrier are also often used in various catalytic reactions.In this paper,the catalytic performance of Cu/CeO₂ nanoparticle catalysts in the hydrogenation of CO₂ to methanol reaction was firstly pre-studied and it was shown that the loading of 40 wt.%Cu had the optimal catalytic performance.Based on the above experiments,CeO₂（nanoparticles,nanosheets,nanorods and nano-octahedra）carriers with different morphologies were prepared by hydrothermal method and then loaded with 40wt.%Cu by impregnation method to investigate the difference of CeO₂ morphology on the performance of Cu/CeO₂ catalysts for CO₂ hydrogenation to methanol.The experimental results show that after loading with copper,the catalyst and the carrier can maintain the same morphology,but there are differences in the size of the exposed crystalline surface and specific surface area,the H₂reduction temperature and the degree of activation of CO₂ on the catalyst surface.Among them,the nano-sheeted Cu/CeO₂ catalyst had a good catalytic effect with a CO₂ conversion of 8.56%and a methanol selectivity of 96.3%.In the CO₂ hydrogenation to methanol reaction,the relationship between CO₂ conversion and morphology is:Cu/CeO₂ nanosheets>Cu/CeO₂nanorods>Cu/CeO₂ nanoparticles>Cu/CeO₂ nanooctahedra.The Cu/CeO₂ nanosheet catalysts with controlled morphology were then prepared by a one-step method to investigate the difference in performance of Cu/CeO₂ nanosheet catalysts for methanol preparation by CO₂ hydrogenation.The experiments show that the CO₂conversion tends to increase and then decrease with increasing Cu loading,and the Cu/CeO₂nanosheet morphology remains unchanged at 15 wt.%Cu loading.At a Cu loading of 10 wt.%,the Cu/CeO₂ nanosheet catalyst had a maximum Ce³⁺of 34.25%,a maximum oxygen defect concentration,a maximum Cu dispersion of 29.7%,a CO₂ conversion of 6.16%and essentially no by-product CO formation.Finally,Cu/CeO₂ nanosheets and Cu/CeO₂ nanorods catalysts were prepared by the impregnation and one-step methods under the loading of 10 wt.%Cu to study the effect of the preparation methods on the performance of the Cu/CeO₂ catalysts for CO₂ hydrogenation to methanol.The one-step method was found to produce Cu/CeO₂ nanorod catalysts with uniform morphology and good dispersion,and the one-step method had higher Cu dispersion,lower H₂reduction temperature and improved CO₂ conversion and methanol selectivity than the impregnation method for the same morphology.