Advances in Catalytic Pyrolysis of Lignin toward Aromatic Hydrocarbon Production
Aromatic hydrocarbons, essential chemical feedstocks for fuels, synthetic fibers, and pharmaceuticals, are predominantly derived from petroleum refining. The catalytic conversion of lignin, a major lignocellulosic component, offers a renewable route to these chemicals. This review systematically examines the influence of pyrolysis methods, catalysts, and reaction conditions on the catalytic pyrolysis of lignin to aromatic hydrocarbons. Key parameters include catalyst acidity and pore structure, which govern selectivity and yield. Reaction temperature, catalyst-to-lignin ratio, and residence time critically affect product distribution. The review outlines catalytic mechanisms, such as deoxygenation, cracking, and aromatization, and highlights the role of zeolite catalysts, particularly HZSM-5, in enhancing monocyclic aromatic hydrocarbon yields. Metal modification (e.g., Fe, Ni, Ga) and pretreatment strategies (e.g., torrefaction) are discussed for improving efficiency. Challenges remain in catalyst deactivation due to coking and the complexity of lignin structure. Future research directions include developing robust catalysts, optimizing reactor designs, and integrating processes for industrial viability. This review provides theoretical and technological guidance for advancing lignin-to-aromatics conversion.