Hydrolysis of cellulose and woody biomass over sustainable weak-acid carbon catalysts from alkaline lignin

Abstract

Low-cost and sustainable weak-acid carbon catalysts were prepared from alkaline lignin (AL) by pyrolysis of AL followed by an acid solution treatment process, and applied for the hydrolysis of cellulose and woody biomass for the production of monomeric sugars such as glucose and xylose, which are important for production of industrial platform chemicals. The effect of pyrolysis temperature on the acidity of the final carbon catalyst was investigated. It is found that the AL-derived carbon catalysts at the pyrolysis temperature of 450 °C (denoted as AL-Py-450) exhibited the highest activity in the hydrolysis of ball-milled cellulose with a cellulose conversion of 70.8% and a glucose yield of 46.3% in a neat water reaction system. Furthermore, with the addition of 0.012 wt% hydrochloric acid (HCl) in the above reaction system, the cellulose conversion was increased to 96.1% with a glucose yield of 69.8%. In the same reaction conditions, the AL-Py-450 carbon catalyst also exhibited good catalytic activity for the hydrolysis of lignocellulosic biomass, i.e., Japanese cedar wood, with yields of glucose and xylose of 47.1% and 40.3%, respectively. Therefore, this study could provide a new perspective to utilize the wasted alkaline lignin as a source for the preparation of sustainable weak-acid carbon catalysts for the hydrolysis of cellulose and lignocellulosic biomass.