Roles of molten salts in biomass pyrolysis: Heat and mass transfer, catalysis, and product regulation

Molten salt-assisted biomass pyrolysis is a promising way to fully utilize biomass resources for high value-added products. However, key aspects such as heat and mass transfer processes, catalytic pathway modulation and molten salt recovery have not yet been systematically reviewed. In this manuscript, the effects of molten salt-assisted pyrolysis on solid (biochar), liquid (bio-oil) and gas products are addressed, and the recovery of molten salt is analyzed on both technical routes and influence mechanisms. In particular, this review focuses on the catalytic characteristics of different molten salt ions and explores their effects on deconstructing biomass complex chemical composition and pyrolysis reaction kinetics. It is hoped that this review could summarize the current challenges and problems of molten salt-assisted biomass pyrolysis and provide theoretical convenience for research in the future.