@

초록

Lignin is the most abundant renewable reservoir of aromatic carbon, yet its selective conversion into fuels and chemicals remains a central challenge for next-generation biorefineries. Among the many lignin valorization routes, solvothermal liquefaction has been gaining increased attention, because it couples lignin dissolution, depolymerization, and stabilization of reactive fragments within a single condensed-phase reaction environment, thereby mitigating repolymerization and char formation. This Review critically assesses recent advances in solvothermal lignin liquefaction, with particular emphasis on how solvent chemistry, catalytic functionality, and reaction severity jointly govern depolymerization pathways and product distributions. Solvent systems ranging from short-chain alcohols and aqueous mixtures to ionic liquids and deep eutectic solvents are evaluated in terms of lignin solubilization, hydrogen-transfer reactivity, and intermediate capping/stabilization. Progress in heterogeneous catalysis is discussed through the lens of solvent-catalyst synergy, highlighting how metal identity, support properties, and bifunctional acid-metal interactions control aryl-ether cleavage, suppress condensation, and tune hydrodeoxygenation extent. Beyond molecular-scale chemistry, emerging reactor configurations, and scale-up strategies for reductive catalytic depolymerization (RCD) and lignin-first fractionation are reviewed alongside techno-economic and life-cycle assessments, which consistently identify solvent recovery, operating pressure, and reactor design as dominant cost and environmental drivers. By integrating mechanistic insights with process-level constraints, this Review delineates key challenges and actionable design principles needed to translate solvothermal lignin liquefaction from laboratory studies to scalable, low-carbon biorefinery technologies.

키워드