Depolymerization of cellulosic feedstocks using magnetically separable functionalized graphene oxide

Abstract

Hydrolysis of cellulose into saccharides using a magnetically separable functionalized graphene is reported for potential applications in the environmentally benign saccharification of cellulose. Crystalline pure cellulose is hydrolyzed by graphene bearing –SO₃H, –COOH and –OH functional groups in combination with iron nanoparticles. We observed nearly complete hydrolysis of cellulose into glucose and small (4–5 unit size) oligomers using low (1 : 1) catalyst to cellulose ratio. The apparent activation energy for the hydrolysis of cellulose into glucose using these catalysts is estimated to be 12 kJ mol⁻¹, several times smaller than that for sulfuric acid under optimal conditions (170 kJ mol⁻¹). The catalyst can be readily magnetically separated from the saccharide solution after the reaction for reuse in the reaction without loss of activity. Nearly complete hydrolysis of sugarcane bagasse into water soluble saccharides with repeated recycling was also possible. The catalytic performance of the graphene-based catalyst is attributed to the ability of the water soluble nanostructured material with a large concentration of polar groups (–OH, –COOH) which readily adsorb cellulose, while providing a large concentration of acidic functionality to hydrolyze the cellulose.