Study Of Cu-based Catalysts For Ethanol Dehydrogenation To Acetaldehyde

Production of high value-added chemicals from abundant,renewable biomass and its derivatives provides a viable route to alleviate our dependence on depleting fossil fuels.For this purpose,bioethanol is particularly attractive because of its facile synthesis by biomass fermentation,and expected reduced cost.Bioethanol can be converted into acetaldehyde and hydrogen through a direct dehydrogenation process,with the advantages of high atomic economy and easy separation of products,and it is considered as the most promising acetaldehyde production route.In this thesis,we explored the effect of Cu-C-Si interface structure on ethonal dehydrogenation based on the concept of function-oriented nanostructure customization and the goal of designing highly selective ethanol dehydrogenation catalyst.Firstly,we synthesized a uniform mesoporous carbon material?MC?with high specific surface area(1640 m² g^-1)and large pore volume(3.28 cm² g^-1)by hydrothermal method.After loading copper,we prepared Cu/MC catalyst to study the effect of carbon surface properties on Cu nanoparticles,and further explore the effect of ethanol dehydrogenation performance.Compared with oxide supports such as SiO₂ and Al₂O₃,acetaldehyde selectivity on Cu/MC catalyst is really excellent?>95%?.Combined with the characterization results,it was found that Cu nanoparticles on Cu/MC catalyst have higher dispersion and more active sites,thus leading to excellent ethanol conversion.Particularly,at 280°C,ethanol conversion on Cu/MC catalyst is 65.8%,while only 35%-50%reported in the literatures.Furthermore,we modified the surface of the silicon carbide?SiC?to alter the properties of the interface and prepared a series of Cu catalysts?Cu/SiC,Cu/SiO₂/SiC,and Cu/C/SiC?with the aim of insight into the effect of the interface structure and composition on catalytic dehydrogenation of ethanol.At 280°C,the Cu/SiO₂/SiC catalyst exhibits high ethanol conversion due to the excellent dispersion of Cu nanoparticles promoted by silica-rich interface.In contrast,Cu nanoparticles dispersed on C/SiC shows somewhat lower activity but excellent acetaldehyde selectivity under the same condition.This difference is attributed to the fast removal of acetaldehyde because of its low affinity for the relatively inert carbon-rich interface?Cu/SiC?.This chapter provides an in-depth understanding of Cu-Si-C multi-interfacial structure and the ethanol dehydrogenation behavior,which may shed light on the design of novel catalysts with tailored interfacial structures.