1D Lignin-Based Solid Acid Catalysts for Cellulose Hydrolysis to Glucose and Nanocellulose

One-dimensional (1D) solid acid catalysts have been synthesized from lignin-based activated carbon fibers via sulfonation and hydrothermal treatment to be mesoporous and contain 0.56 mmol/g sulfonic and 0.88 mmol/g total acid for direct hydrolysis of highly crystalline rice straw cellulose (CrI = 72.2%). Under optimal hydrothermal conditions of 150 °C and 5 atm, 69.8% of cellulose was hydrolyzed in three consecutive runs, yielding 64% glucose at 91.7 selectivity as well as 8.1% cellulose nanofibrils (2.1 nm thick, 3.1 nm wide, and up to 1 μm long). These 1D acid catalysts could be used repetitively to hydrolyze the remaining cellulose as well as be easily separated from products for hydrolysis of additional cellulose. In essence, complete valorization of rice straw cellulose has been demonstrated by direct hydrolysis with these 1D acid catalysts to superior glucose selectivity while generating high value cellulose nanofibrils.