Advances in Upgrading Lignin Pyrolysis Vapors by Ex Situ Catalytic Fast Pyrolysis

Abstract

AbstractLignin, a highly branched, substituted, mononuclear aromatic polymer, is one of the principal components of lignocellulosic biomass. Its valorization is considered an important part of the modern biorefinery scheme. However, as a result of the natural complexity and high stability of lignin, its depolymerization and the following conversion are challenging. The unique structure and composition of lignin offer many possible routes to produce liquid fuels and chemicals. Recognized as an efficient and feasible process, ex situ catalytic fast pyrolysis (CFP) has attracted much attention for upgrading lignin and lignin pyrolysis vapors. The main challenge of this process is the development of active and stable catalysts that can effectively break the C−O bond of lignin and decompose the intermediates. In this Review, we aim to provide an overview of recent advances on a related topic. The Review introduces ex situ CFP, the reactions and pathways of lignin vapors in the ex situ CFP process, and summarizes in detail recent progress in experimental studies on upgrading lignin‐derived model phenols, lignin, and lignin pyrolysis vapors to hydrocarbons by the ex situ CFP process over different catalysts.