Study On The Reaction Of Catalytic Hydrogenation Of CO₂ To Ethanol

CO₂ hydrogenation to ethanol（C₂H₅OH）is considered a promising way for CO₂conversion and utilization.However,achieving high selectivity of C₂H₅OH production is a challenge because methanol or mixed alcohols is the main product for CO₂ hydrogenation.CO₂ and H₂ activization,as well as C-C coupling are the critical steps to control the yield of C₂H₅OH,which demand highly active,highly selective and stable catalysts.Here,a type of copper and molybdenum carbide supported on HZSM-5 zeolite catalysts（Cu-Mo₂C/HZSM-5）was developed in the CO₂hydrogenation to C2H5OH.The effects of catalyst composition and structure on the conversion of CO₂ and selectivity for C₂H₅OH were fully investigated and the efficiency of CO₂ hydrogenation was optimized.The main research contents are as follows:1.The highly dispersed M-Mo2C/HZSM-5 catalysts were prepared by temperature programmed carbonization method,and the effects of metal（M=Cu,Fe,Co,Ni）,catalyst composition,the ratio of Si/Al of supports and the reaction conditions on the yield of C₂H₅OH were investigated.The result showed that high selectivity for C2H5OH could be achieved over the 2Cu-10Mo2C/HZSM-5（Si:Al=130）catalyst,and the highest selectivity of 73.3%with a CO₂ conversion of 25.6%was obtained at 210 ^oC,3.0 MPa and GHSV 6000 h^-1.The high productivity of C₂H₅OH with 90 h stability showed that this catalyst is active and stable for CO₂ hydrogenation to ethanol.2.To understand the reaction mechanism on the solid solution catalyst,the surface species evolved in the reaction were monitored by in situ diffuse reflectance infrared Fourier transform spectroscopy.The result showed that Cu and Mo2C cooperated with each other in the reaction of CO₂ to ethanol.The active sites of the Cu⁺could promoted the HCOO*to*CH_xO intermediate species on the surface of catalyst and Cu⁰ dissociates H₂ into proton H*.*CH₃ from dissociative adsorption of CO₂ and*CO from non-dissociative adsorption of CO₂ were observed on the surface of Mo₂C,which migrate to the zeolite pore channel to form*CH₃CO,and then reduced to C₂H₅OH.3.The effect of supported M-WC/HZSM-5 catalysts with different metals on the activity of CO2 hydrogenation was also studied.The main products are CO and CH4and the highest ethanol selectivity was 32%over 2Ni-10WC/HZSM-5 catalyst.