Pore-scale study of phase transitions and humins coking in cellulose hydrolyzed to levulinic acid

Abstract

Hydrothermal depolymerization of cellulose has generated tremendous excitement as a promising pathway to sustainable chemistry. Among these biomass products, levulinic acid (LA), as one of the most promising platform chemicals with rich chemistry, can be used as various fuel additives or further refined into sustainable biofuel and high-value chemicals. However, hydrothermal conversion of cellulose into chemicals involves complex physicochemical processes, suffering currently from insufficient understanding of processes coupling mechanisms and carbon deposition caused by coking side reaction. Here, we developed a pore-scale multiphase reactive transport model based on the lattice Boltzmann method (LBM), coupling the multicomponent multiphase flow, heterogeneous reaction, cellulose dissolution, and humins coking, to systematically explore the conversion of cellulose to LA over acid catalyst. A relationship with a monotonic increase between the coking appearance time and H+ concentration has been found when the coking amount shows a linear decrease over acid concentration. Our results underscore the importance of in-depth elucidation of process coupling mechanisms for the establishment of efficient hydrothermal preparation strategies from cellulose to platform chemicals.