Efficient Catalytic Conversion of Cellulose to Platform Chemicals Using Mechanical Treatment

Mechanical treatment of cellulose is an emerging concept for dramatically increasing the hydrolytic reactivity of cellulose. We report here the recent developments in the field of mix-milling and mechanocatalysis for cellulose pre-treatment. Mix-milling enhances the solid-solid contact between cellulose and carbon catalyst during hydrolysis reaction. Kinetic study shows that mix-milling specifically enhances the rate of cellulose to oligomer hydrolysis (13 fold), whereas the rate of oligomer to glucose hydrolysis is not influenced. Very high glucose yield of 88 % was obtained by mix-milling cellulose with K26 and using trace amount of HCl. Mix-milling was also applicable for single-pot hydrolytic hydrogenation of cellulose to sugar alcohols. RU/AC catalyst was stable under mix-milling condition and 68 % of sugar alcohol was obtained using only 9 atm H-2 pressure. Unlike mixmilling, mechanocatalysis takes advantage of presence of strong acid catalyst during milling to depolymerize cellulose. Completely soluble glucans were obtained after 7.5 h of milling in the presence of 0.25 mmol of acid g(-1) cellulose. The glucans were highly reactive towards conventional and transfer hydrogenation reaction, affording ca. 90 % sugar alcohol yield in both cases after 1 h reaction. The transfer hydrogenation of cellulosic glucans was successfully upgraded to a lab-scale fixed-bed reactor.