Catalytic Enhancement of the Alkaline Thermal Treatment of Cellulose to H2 in the Presence of Ca(OH)2 and Low-Loading Catalysts

Concerns over climate change have led to the development of renewable technologies that can produce energy without the associated carbon-footprint of fossil fuels. Biomass is a suitable feedstock for energy conversion since it is inherently a carbon neutral feedstock, yet its low energy density and high moisture content exclude its use in conventional power generation facilities. Consequently, a simple conversion technology is investigated that can convert biomass to H₂ at moderate temperature and ambient pressure, in a distributed manner. Previous work has shown that NaOH or Ca(OH)₂ combined a 10% Ni/ZrO₂ catalyst, are effective in converting cellulose to H₂, while significantly suppressing CO₂ production. Ca(OH)₂ is an attractive substitute to NaOH due to its relative abundance as CaO in industrial waste sources (steel-slag) and lower price. Research has focused on utilizing Ca(OH)₂ with low-loading Ni, Pt, Pd, Co, Fe, and Cu supported on  α-Al₂O₃ to enhance H₂ production from cellulose. Ni has shown to enhance H₂ when in direct contact with the solid reactants (4% to 10% H₂ yield), however 40% to 50% of enhancement in yield was due to gas phase reforming. Relatively constant CO and CH₄ formation rates have suggested that reactions such as steam reforming and the water-gas shift are not likely mechanisms for H₂ production. It is possible that Ni enhances H₂ production in the gas phase through the reforming of higher molecular weight hydrocarbons to H₂ and CO₂. In this study the reaction pathways are elucidated in order to provide insight into the alkaline thermal treatment of cellulose in the presence of a Ni catalyst.