Impacts of torrefaction and ash reduction on the catalytic fast pyrolysis of energy crops

Energy crops containing a large fraction of alkaline metals produce low-quality bio-oil during pyrolysis. In this study, effects of alkali metal reduction on catalytic fast pyrolysis of Napier grass were investigated. Also, a thermal pretreatment, torrefaction, was investigated for its effect on reducing coke formation and oxygen content of pyrolysis oil produced from demineralized feedstock. An in-situ catalytic fast pyrolysis process was developed using red mud, a waste material from aluminum production, as a catalyst. A simple water washing method reduced total ash content and alkaline metals content by more than 50% (wt). Reduction of alkaline metal in biomass increased levoglucosan concentration up to 200+ g/L in bio-oil without a catalyst. Alternatively, overall concentrations of levoglucosan, acetate, and formate were reduced with torrefaction pretreatment and catalytic pyrolysis. Further research is required to optimize the yields of water soluble fractions in bio-oil with reduced alkaline metals in the energy crops.