Preparation And Study Of Ni-based Catalyst For Hydrogen Production By Ethanol Steam Reforming

As an efficient and clean energy,hydrogen can simultaneously solve the energy crisis and environmental pollution which are the most challenging problems for people.Ethanol is a prosperous renewable energy carrier mainly produced from biomass fermentation.Reforming of ethanol provides a promising method for hydrogen production from renewable resources,which has attracted much attention due to the fact that the stock is renewable and the CO₂ can form a closed circulatory system in nature.For ethanol steam reforming,supported Cu,Ni,Co and noble metal catalysts have been extensively investigated.Due to its remarkable capability in C-C bond cleavage and low cost,the nickel catalyst is considered as one kind of the most promising catalysts for steam reforming of ethanol.However,deactivation by sintering and carbon deposition is the greatest obstacles for most Ni-based catalyst.The supported Ni-based catalysts were further investigated for steam reforming of ethanol,the effects of metal loading,promoters,nickel precursors,supports and preparation methods as well as reaction temperature,EtOH/H2O molar ratio and GHSV were focused on in this thesis;Characterization studies were also performed by employing versatile characterization techniques such as ICP?BET?XRD?H2-TPR and TEM to gain insights to the catalyst structure,morphology,reducibility and the interaction between active particle and supports,and integrated with the experimental results obtained.The principal results were summarized as follows:The effects of metal loading and reaction temperature were investigated,the best hydrogen selectivity was reached at 6 wt%of Ni loading,and the hydrogen selectivity increased with the reaction temperature,reached the maximum at 650 ?;The influence of Au addition on the catalytic performance was further studied,the 6Ni/SBA-15 catalyst modified with 1.2 wt%of Au exhibited the highest activity and excellent long-term stability in ethanol steam reforming.In light of the characterization results,it could be concluded that the addition of Au strengthened the interaction between the SBA-15 support and nickel particles to form well-dispersed,smaller nickel particles,suppress the carbon deposition,due to these synergetic effects,the catalyst showed excellent hydrogen selectivity and long-term stability.The Ni-based catalyst prepared with different nickel precursors were tested for ethanol steam reforming,the catalysts prepared from nickel citrate as precursors performed excellent activity and high stability.For the catalysts used citrate salts as precursors,there was new reduction peaks occurred at the higher temperature,this suggested that the interaction between the SBA-15 support and nickel particles has been strengthened,and it could also be seen that the NiO diffraction peaks of the catalysts became broader and shifted to a higher angle,this suggested that the citrate salts is favorable toward the formation of the smaller NiO particles.The Ni-based catalyst prepared with SiO₂,SBA-15 and MCM-41 as supports were studied for ethanol steam reforming,the catalytic performances of Ni/SiO₂ and Ni/SBA-15 were similar,and were excellent than that of Ni/MCM-41,however,the preparation cost of SBA-15 material was expensive and the production process was complex,based on these,the SiO₂ had bright prospect in industrial applications.Finally,following the previous study,the catalysts used citrate salts as precursors were prepared by microwave technology and were tested for ethanol steam reforming,excitingly,this catalyst was as effective as the catalyst prepared with traditional calcination technology.The stability of the two catalysts were also examined at 550 ? for 120 h,the two catalysts showed excellent long-term stability in the same way,but for microwave technology,it could drastically shorten the time required for catalyst preparation while greatly reduced the production cost,therefore,this preparation method was much more likely for large-scale industrial applications.