Facile Directional Conversion of Cellulose and Bamboo Meal Wastes over Low-Cost Sulfate and Polar Aprotic Solvent

Abstract

Directional depolymerization is a critical step for the integrated utilization of waste lignocellulosic biomass resources to produce value-added biofuels and biochemicals. Herein, we demonstrate an efficient and environmentally benign liquefied process for converting cellulose and waste lignocellulosic residues into levulinic acid (LA) in a polar aprotic solvent using a low-cost sulfate as catalyst. Due to the synergistic effect between the γ-valerolactone (GVL) and an active acid center derived from sulfate, more than 77 mol % and 61 mol % of biochemicals were obtained from cellulose and bamboo meal wastes in GVL/H2O (m/m = 9:1) solvent at 200 °C for 2 h, respectively. A combination of 27Al NMR spectroscopy and electrospray quadrupole time-of-flight tandem mass spectrometry (ESI-Q-TOF-MS/MS) revealed that the [Al(OH)2(aq)]+ species significantly contributed to cellulose depolymerization under cationic polarization of polar aprotic solvents. Besides, the existence of an appropriate amount of water was believed to be responsible for promoting the destruction of cellulose and the restraint of humin formation. Notably, all solvents and byproducts could be efficiently retrieved during this process, which shed light on its considerable industrial application prospects and facilitated the high value-added utilization of waste biomass resources.