Pathways for biomass‐derived lignin to hydrocarbon fuels

Abstract

Production of hydrocarbon fuel from biomass‐derived lignin sources with current vision of biorefinery infrastructure would significantly improve the total carbon use in biomass and make biomass conversion more economically viable. Thus, developing specialty and commodity products from biomass derived‐lignin has been an important industrial and scientific endeavor for several decades. However, deconstruction of lignin's complex polymeric framework into low molecular weight reactive moieties amenable for deoxygenation and subsequent processing into hydrocarbons has proven challenging. This review offers a comprehensive outlook on the existing body of work that has been devoted to catalytic processing of lignin derivatives into hydrocarbon fuels, focusing on: (i) the intrinsic complexity and characteristic structural features of biomass‐derived lignin; (ii) existing processing technologies for the isolation and depolymerization of bulk lignin (including detailed mechanistic considerations); (iii) approaches aimed at significantly improving the yields of depolymerized lignin species amenable to catalytic upgrading; and (iv) catalytic upgrading, using aqueous phase processes for transforming depolymerized lignin to hydrocarbon derivatives. Technical barriers and challenges to the valorization of lignin are highlighted throughout. The central goal of this review is to present an array of strategies that have been reported to obtain lignin, deconstruct it to reactive intermediates, and reduce its substantial oxygen content to yield hydrocarbon liquids. In this regard, reaction networks with reference to studies of lignin model compounds are exclusively surveyed. Special attention is paid to catalytic hydrodeoxygenation, hydrogenolyis, and hydrogenation. Finally, this review addresses important features of lignin that are vital to economic success of hydrocarbon production. Published in 2013 by John Wiley & Sons, Ltd