Nickel-based And Ni-Co Bimetallic Catalysts For Steam Reforming Of Ethanol To Produce Hydrogen

Currently,the catalysts for steam reforming of ethanol reported in literature generally have good activity and selectivity of hydrogen,so the research focus is how to improve the stability of the catalyst and to reduce the cost.The paper selected transition metal Ni and Co as the active component of the catalyst,which has a low cost.In SRE reaction,sintering of the active component at high temperature and carbon deposition on the catalyst surface at low temperature are the main causes of catalyst deactivation.For these two problems,this paper proposes three catalysts design ideas to improve the stability of the catalyst:?1?add an alkaline additive to the catalyst;?2?prepare bimetallic Ni-Co alloy catalysts;?3?load metal Ni on high surface area support,then study the relationship between the structure and properties of the catalyst.Firstly,La_1-x K_xFe_0.7Ni_0.3O₃?x =0,0.05,0.1?with perovskite structure was prepared by citric acid complexation method,and after reduction K-doped Ni/LaFeO₃ catalysts were obtained.The catalytic performance including the ability to prevent coking and sintering over the catalysts was investigated.The results indicate that the K-doped catalysts are very active,highly selective to hydrogen,as well very stable for SRE reaction.The doping of potassium can also restrain the sintering of nickel.The doping of K improved the ability to prevent coking of the catalyst markedly,which is attributed to the electron donation effect of potassium to nickel and this donation effect can enhance C-Ni bond and weaken C-C bond,then promote the ability for breaking C-C bond on the metal nickel sites.Secondly,a series of zirconia-supported LaNi_1-xCo_xO₃ catalysts were prepared by impregnating ZrO₂ with a mixed solution composed of ions consisting of nickel,cobalt,lanthanum and citric acid.The Ni and Co metals formed in one reduction peak,which is beneficial for the formation of Ni-Co alloy.After reduction,the Ni-Co alloy nanoparticles were highly dispersed on ZrO₂ and modified with La₂O₃.The bimetallic catalyst exhibited very good catalytic performance for SRE,including high activity,high selectivity to hydrogen and very good stability due to the synergistic catalysis of cobalt and nickel.The synergy between cobalt and nickel led to a higher anti-coking ability compared to the corresponding monometal catalysts,and the bimetallic catalyst exhibited very good anti-sintering ability.This preparation scheme could be extended to the preparation of many other supported bimetallic catalysts because many transitional metal ions can act as the ions of a perovskite-type oxide.Finally,loading nickel on different structure supports as catalysts for steam reforming of ethanol was investigated.Ce_0.5Zr_0.5O₂ and macroporous Ce_1-xZr_x O₂?x=0,0.5?supported Ni catalysts were successfully synthesized by impregnation method in this work.NiO/Ce_1-x Zr_xO₂ catalysts were characterized by using SEM,XRD,H₂-TPR,TG and TEM characterization methods.After reduction,the catalyst precursor favored to form nanoparticles of Ni/Ce_1-xZr_xO₂.The macropore Ce_0.5Zr_0.5O₂ contributed to the excellent conversion of ethanol as well as the very good stability.