Design Of Heterogeneous Catalysts For Carbon Dioxide Hydrogenation To Formic Acid

Effective development and utilization of CO₂ and converting it into valuable fuels or chemicals has become an important direction of sustainable development strategy.The synthesis of formic acid by CO₂ hydrogenation is an atomic economic reaction,and formic acid is an important intermediate species of CO₂ hydrogenation to produce methanol and methyl formate.The formation of formic acid is often the step of speed control.Therefore,the in-depth study of CO₂ hydrogenation to formic acid is of practical significance not only to the activation and utilization of inert molecules CO₂ and small molecule hydrogen,but also of important to environmental and economic significance.Based on the activation mechanism of CO₂,two kinds of heterogeneous catalysts were designed to investigate the catalytic performance of CO₂ hydrogenation to formic acid.The main outlines are as follows:1.Ru catalysts supported on different oxides were prepared by wet impregnation method,and the catalytic performance of CO₂ hydrogenation to formic acid was investigated.Through the investigation of the active components,metal loading,base,gas pressure and other factors,it is found that the turnover number（TON）of formic acid reached 3976 over 0.28%Ru/CeO₂catalyst under the condition of DBU as additive base,methanol as solvent,at 140 ^oC for 10 h,with 1.5 MPa CO₂,2.5 MPa H₂.The results of XRD and HRTEM show that sub nano Ru is highly dispersed on the surface of CeO₂.2.The Schiff base functionalized silica supported Au based bimetallic catalyst was prepared by NaBH₄ reduction,and the catalytic performance of the hydrogenation of CO₂ to formic acid was investigated.The results show that the TON of formic acid achieved 11953over hydrothermal treatment Co_1.0-Au_0.5/SiO₂-Schiff catalyst at 80 ^oC for 8 h with 3 MPa CO₂,5 MPa H₂.The results of STEM,XRD and XPS demonstrated that there was interaction between the Au and Co bimetal.Besides,the metal particals are well-distributed,which probably responsible for the high activity of Co_1.0-Au_0.5/SiO₂-Schiff catalyst.