Preparation Of Mesoporous CeO₂ Nanospheres With Large Specific Surface And Their Application In CO₂ Methanation And CO Catalytic Oxidatio

With the continuous development of CO₂ methanation catalytic conversion and CO low-temperature catalytic oxidation technology,researchers hope to develop a low-cost environmental material to replace the efficient role of precious metals in catalytic technology.Among many catalytic materials,CeO₂ material has attracted extensive research and attention due to its high oxygen storage capacity and unique redox characteristics.Generally speaking,the specific surface area of the catalyst determines the number of active sites of the catalyst,so the specific surface area should be increased to improve the activity of the catalyst.In this paper,mesoporous CeO₂ nanospheres with large specific surface area were synthesized by hydrothermal method,and Ni-based and CuO-based catalysts were prepared by using them as carriers,which were applied to CO₂ methanation reaction and CO catalytic oxidation reaction respectively.The research work is mainly divided into these sections:（1）Mesoporous CeO₂ nanospheres with large specific surface area,strong thermal stability and excellent structural properties were prepared by solvothermal method as the support of Ni-based CO₂ methanation catalyst.The effects of Ni loading and calcination temperature on the catalytic activity of CO₂ methanation were investigated.In addition,comparison catalysts supported on commercial CeO₂,Al₂O₃ and SiO₂ were prepared for CO₂ methanation to illustrate the effects of mesoporous channel topology,metal-support interaction and redox properties.It was found that the catalyst supported on mesoporous CeO₂ nanospheres with large specific surface area exhibited better metal Ni dispersion and higher CO₂ conversion than the control catalyst.Among them,the catalyst with a nickel loading of 20%and a calcination temperature of 400℃ showed the best catalytic performance,especially at a low temperature of 300℃,the CO₂ conversion rate reached 87.38%.In addition,the temperature-programmed surface reaction of CO₂ methanation and in-situ infrared experiments of catalyst precursor calcination process were carried out to study the reaction pathways and intermediates of calcination process on different catalysts.（2）CuO-based catalysts have the advantages of low cost and good catalytic activity,and are often used in CO catalytic oxidation reactions.In this study,mesoporous CeO₂ nanospheres were used as the support of CuO-based catalysts for CO catalytic oxidation.The effects of CuO loading and calcination temperature on the catalytic activity of CO catalytic oxidation were investigated.In addition,CuO-based catalysts prepared with commercial CeO₂,Al₂O₃ and SiO₂as supports were compared to investigate the effects of mesoporous channel topology,metal-support interaction and redox properties.The results showed that the 10CuO/N-CeO₂-500catalyst still maintains 100%CO conversion even at 120-150℃,which may be because the large specific surface area of CeO₂ nanospheres is beneficial to the dispersion of CuO species.（3）Metal oxides（PrO₂,La₂O₃,Sm₂O₃,Yb₂O₃,Fe₂O₃,MnO₂ and Co₂O₃）doped CuO-based mesoporous CeO₂ nanospheres catalysts were prepared by incipient wetness impregnation method using mesoporous CeO₂ nanospheres as support for CO catalytic oxidation.The synergistic effect of bimetallic on CO catalytic performance was explored.It is found that the high dispersion of rare earth or transition metal oxides could prevent the thermal sintering and aggregation of CuO-based catalysts during calcination,and could adjust the oxygen mobility and reduction ability of the catalysts.The results showed that the CuO-based catalyst with MnO₂ addition did not deactivate during the stability experiment at 12 h and 80℃,and maintained a CO conversion rate of about 90%,showing good thermal stability.