On The Design And Synthesis Of Ni-based Catalysts With High Stability For Ethanol Steam Reforming

Nowadays,with the rapid development of economy,the limited reserves and environmental concerns have spurred extensive attention from the scientific,governmental and industrial communities toward the search for alternative green fuels.Hydrogen,as a clean alternative fuel,has attracted significant interests.Ethanol steam reforming for hydrogen production has become a research emphasis in energy fields since ethanol is a renewable raw material.Compared to the high cost of noble metals,nickel-based catalysts,as the classic catalysts in the methane steam reforming with high activity and relatively low costs,appear to be an excellent alternative.However,there exists severe deactivation due to the thermal sintering and carbon deposition over Ni-based catalysts.Additionally,in the low temperature reforming,an apparent drawback is its low hydrogen yield due to its thermodynamic limit.This dissertation designed and synthesized a series of highly active and stable Ni-based catalysts.The design of the meso-x La Ni Al catalysts with ordered mesoporous structure for ethanol steam reforming is first described in this thesis.The ordered mesostructure was beneficial to obtain and maintain the 4–6 nm Ni nanoparticles,and then meso-0La Ni Al catalyst exhibited excellent catalytic performance than 0La Ni Al catalyst prepared by impregnation.Additionally,the La promoter could enlarge the active surface areas,and further enhance the activity of meso-3La Ni Al catalyst.Besides,the presence of La-modifiers enhanced the basicity of the catalyst,cleaned the deposited carbon by reacting with H2 O and CO2,resulting in the suppression of carbon deposition and the improvement of stability.To develop a catalyst with high active surface area to retard deactivation and to increase the hydrogen production for low temperature ethanol steam reforming,we have also designed a highly loaded catalyst prepared by co-precipitation,which has a takovite structure before calcination.The loading of the catalyst could be up to 78%.Additionally,it obtained small nickel particles(6 nm)and large active nickel surface areas,and then exhibited excellent catalytic performance at 673 K in steam reforming of ethanol.No sintering occurred at 673 K.Despite the presence of carbon deposition,sufficient active nickel surface area maintained the catalyst with excellent activity and stability.