Hydrogen Production From Steam Reforming Of Biomass-derived Alcohols And Sorption Enhanced Process On Ni-based Catalysts

With the diminishing reserves of fossil fuels, it is urgent to develop sustainableenergy. As a clean and efficient secondary energy, hydrogen opens new space forenergy supply and environmental protection. The production of hydrogen frombiomass-derived alcohols attracts increased interest considering the economicdevelopment and environmental impacts. This thesis describes the development ofseveral types of nickel-based catalysts for hydrogen production from steam reformingof biomass-derived alcohols and sorption enhanced process.This thesis first described an investigation regarding the influence of Niprecursors on catalytic performances of Ni/Al2O3catalysts in glycerol steamreforming. The results showed that reduction degrees of nickel, nickel dispersion andparticle sizes of Ni/Al2O3catalysts were closely dependent on the anion size andnature of the nickel precursors, and these properties significantly affected the catalyticperformance of the catalyts in reforming process. Ni/Al2O3prepared by nickel acetatepossessed the moderate Ni reduction degree, high Ni dispersion and small nickelparticle size, which presented the highest H2yield and best catalysis stability.Reaction parameters were also examined, and550oC and a steam-to-carbon ratio of3were optimized. Moreover, coke deposition, mainly graphite species, led to thedeactivation of Ni/Al2O3catalysts in glycerol steam reforming.The La1-xCaxNiO3perovskite-type oxides were also synthesized and investigatedin glycerol steam reforming. The results indicated that the containing elements couldbe uniformly distributed in the perovskite-type oxides after reduction treatment, andthus produced smaller Ni metallic particles and stronger metal-support interactionthan Ni/La2O3catalyst prepared by impregnation method. Effects of lanthanumsubstitution by calcium were also studied and it proved to significantly affect theproperties of the perovskite-type oxides. La0.5Ca0.5NiO3was the optimizedcomposition, owing to its strongest metal-support interaction and best metaldispersion. These properties could highly affect the catalytic performance of preparedcatalysts in glycerol steam reforming: the reaction activity was closely related withthe metal dispersion, and more active sites and stronger metal-support interactioncontributed to better reaction stability. Furthermore, smaller Ni particle size and stronger metal-support interaction were beneficial to reduce the amount of carbondeposition, and thus improved the stability in glycerol reforming.Additionally, we had investigated the sorption of carbon dioxide for enhancedsteam reforming of ethanol to produce hydrogen via Ni-CaO-Al2O3multifunctionalcatalysts derived from hydrotalcite-like compounds. The Ni-CaO-Al2O3catalystspossessed uniform distribution of Ni, Ca and Al, contributing significantly to theexcellent CO2adsorbent capacity and reforming activity in sorption enhancedreforming process. The effect of Ca/Al ratios on Ni dispersion, CaO particle size andcatalytic reactivity were also examined, and a Ca/Al ratio of3.0was optimized. TheNi-CaO-Al2O3catalysts outperform the conventional mixture of CaO adsorbents andNi/Al2O3catalysts for sorption enhanced steaming reforming of ethanol.