Quantitative evaluation of ball-milling effects on the hydrolysis of cellulose catalysed by activated carbon

The synthesis of glucose from cellulose is a critical roadblock for establishing a new sustainable cycle of biorefinery to produce bio-based and environmentally-benign chemicals. We have previously demonstrated that the pre-treatment ball-milling of solid cellulose and a solid catalyst (mix-milling) drastically improves the yield of glucose and oligosaccharides; however, the effect of this type of ball-milling has not been quantitatively evaluated. In this study, we performed several model reactions and found that the mix-milling method drastically enhanced the solid-solid reactions, such as the hydrolysis of insoluble cellulose to soluble oligomers on the solid catalyst, but not liquid-solid reactions. The kinetic study indicated that the rate constant of hydrolysis of cellulose to oligomers using mix-milling was 13-fold higher than that using individual milling. Owing to the fast depolymerisation of cellulose, we achieved a 72% yield of glucose with 97% conversion of cellulose and 74% selectivity at 418 K.