| Fast pyrolysis is a promising technology for effectively converting biomass into liquid fuels. Growing attention has been given to biomass thermochemical depolymerization for bio-oil production. Monomeric and oligomeric lignols derived from lignin during pyrolysis have been evaluated as precursors of transportation fuels; however, reaction mechanisms for the formation of these compounds have not been thoroughly investigated.;The main goal of this dissertation study is to advance our understanding of the mechanisms of lignin thermochemical reactions and the effect of pyrolysis conditions such as pretreatment, H2SO4 addition, temperature, vapor residence time, and particle size on lignin depolymerization.;The hypothesis is that lignin pyrolysis undergoes primary reactions that lead to the formation of a liquid intermediate mainly state by lignin oligomers. These lignin oligomers either evaporate or are thermally ejected from the biomass particle. It was proven in this work that lignin oligomers were the primary products of lignin pyrolysis and that the monomers observed in several Py-GC/MS studies were products of secondary reactions.;The formation and thermal ejection/evaporation of lignin oligomers is critical to explain the outcome of fast pyrolysis reactions. The effect of thermal pretreatment, addition of sulfuric acid, particle size, and pyrolysis temperature on the outcome of fast pyrolysis reacions can be explained by the high reactivity of lignin oligomers forming the liquid intermediates. The effect of vapor residence time and temperature on the composition of the lignin oligomers was further studied. By adding additives and controlling the reaction conditions, the reaction mechanism could be modified to maximize valuable products. The results obtained in this dissertation can be used to develop novel strategies to increase the yield of monomeric and/or oligomeric lignols and develop selective fast pyrolysis reactors. |
