Microwave-assisted catalyst-free hydrolysis of fibrous cellulose for deriving sugars and biochemicals

Microwave (MW) assisted catalyst-free hydrolysis of fibrous cellulose (FC, cellulolysis) at 200 °C promoted a cellulose conversion of ca. 37.2% and quantitative production of valuable C5/C6 sugars (e.g. glucose) and the according platform biochemicals (e.g. 5-hydroxymethylfurfural), corresponding to an overall selectivity of 96.5%. Conversely, conventional hydrothermal (HT) cellulolysis under similar conditions was not effective, even after 24 hours, carbonising the FC. Based on the systematic study of MW-assisted cellulolysis, the specific interaction between water molecules and macroscopic FC under the MW irradiation was proposed, accounting for the interpretation of the experimental observation. The kinetic energy of water molecules under the MW irradiation facilitated the C−C (in the non-hindered surface −CH2OH groups) and C−O−C bond breaking (inside the cellulose cavities) in FC, producing primary cellulolysis products of xylose, glucose and cellobiose.