Pyrolysis offers pathways to convert lignocellulosic biomass to liquid transportation fuels.  Though pyrolysis generates high yields of liquid, the quality of the biofuel has been a major challenge.  Pyrolysis oils have relatively low energy density, low pH, high viscosity and age rapidly during storage.  Upgrading strategies such as hydropyrolysis, catalytic upgrading, esterification, micro-emulsification and many others have been developed, but these often lower liquid yields because of gas and char/coke formation.  In situ catalytic pyrolysis is a promising approach to address the oil quality issue but this approach also produces low liquid yields, large quantities of gas, and aqueous phase products.  Using fractional catalytic pyrolysis, we produced a range of pyrolysis oils with varying degrees of viscosity and different rates of aging.  Polarity-based solvent extraction was used to investigate the factors that contribute to viscosity associated aging of pyrolysis oils; we discovered that oligomeric products from lignin and carbohydrates as well as levoglucosan play major roles in the aging of the pyrolysis oils during storage.  Pyrolysis oils quality was greatly improved by developing new catalysts that decomposed the oligomeric products and thus making pyrolysis oils stable and could be co-processed with standard gas oils to infrastructure ready oils.  The co-processing depended on hydrogen transfer reactions that deoxygenated the pyrolysis oils.  The overall yields of stable pyrolysis oils were also improved by recycling of the gaseous products which reacted to increase liquid yield and decreased char yield.  This improvement through recycling was attributed to the lowering of the activation energy of the pyrolysis reaction.  The reactive pyrolysis gases such as hydrogen, carbon monoxide, and carbon dioxide lowered the activation energy of the pyrolysis reaction in the absence of catalysts.   Thus, catalytic pyrolysis coupled with gas recycling and development of advanced catalysts has the potential to produce infrastructure-ready biofuels.

Progress towards infrastructure- ready thermochemical biofuels

246th National Meeting (2013)

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