Preparation Of Ni - Based Catalysts By Microwave Heating And Its Application In Hydrogen Production From Ethanol Steam Reforming

Energy and environment is the most major problem for the human society sustainable development in future. Hydrogen is an efficient and clean energy, which can simultaneously solve the energy crisis and environment pollution. Meanwhile, ethanol, which can be prepared from fermentation of biomass fermentation, is a non-toxic and renewable resource. Ethanol Steam Reforming for hydrogen has attracted more attention owing to its features of lower reaction temperature and relatively higher H₂ production.Due to its high H₂ selectivity and low cost, the nickel catalyst is considered as one kind of the most promising catalysts for steam reforming of ethanol. The Ni-based catalysts were further investigated for steam reforming of ethanol. The influences of preparation method, Ni loading, promoter, support and Ni precursors as well as EtOH/H₂O molar ratio and reaction temperature on catalytic performance of Ni-based catalysts were studied. The characterization techniques of ICP, BET, XRD, H₂-TPR and Raman were applied to study the structure, morphology, reducibility and the interaction of Ni and support. The main conclusions were summarized as follow:In the first part, the comparisons of different preparation methods on catalytic performances of Ni-based catalysts were investigated. The result indicated the catalyst prepared by microwave method not only easy energy-saving but also exhibit excellent performance. The effects of Ni loading and reaction temperature on catalytic performances were researched. The best H₂ selectivity was obtained at 6% Ni loading. Meanwhile, the catalytic activity of catalyst increased with reaction temperature and reached the maximum at 600 ℃. The stability of Ni-based catalyst, prepared by microwave method, was studied. And it showed the preferable stability on 240 h long-term test. The microwave method greatly shorted the time and reduced the cost of preparation.In the second part, the effects of the addition of rare metals on the catalytic performance were researched. It showed that the addition of rare metal could improve catalytic activity of Ni-based catalyst, especially La and Er. Then, the effects of Er amount and reaction temperature on catalytic performance of Ni-based catalyst were investigated. The catalyst with 6% of Er exhibited the best hydrogen selectivity and, the catalytic activity increased with reaction temperature, acquired the maximum of selectivity at 600 ℃. At 550 ℃, the catalyst showed the excellent stability on 500 h on-line test. The result of characterization indicated that the addition of rare metal is beneficial to the dispersion of Ni active component, smaller particle size and suppress the carbon deposition.In third part, the comparisons of catalytic performances of Ni-based catalysts with different supports were studied. The result showed the best catalytic performance was obtained over the catalyst with SiO₂ as support. What is more, SiO₂ is cheap and with good prospect in application. Then, the comparisons of catalytic performances of Ni-based catalysts with different Ni precursor were studied. The Ni-based catalyst with nickel citrate as precursor showed the best catalytic activity. At last, the effects of nickel citrate loading on catalytic performance were investigated. The highest hydrogen selectivity was obtained with 6% loading.