Enhancing the efficiency of microcrystalline cellulose depolymerization through a sono-catalytic approach using Fe-kaolin as a heterogeneous catalyst

Microcrystalline cellulose (MCC) poses a significant challenge for biorefinery applications due to its recalcitrant nature. This study investigated a novel sono-catalytic Fenton pretreatment using Fe-modified kaolin (Fe-kaolin) to enhance MCC depolymerization. Systematic investigation of operational parameters (MCC loading, temperature, sonication time, and ultrasonic power) revealed optimal conditions for maximizing MCC solubilization (5 g loading, 80 °C, 3 h sonication, 80 W power). The pretreatment effectively reduced the degree of polymerization of MCC, as confirmed by viscometry. Kinetic analysis demonstrated that the ultrasonic depolymerization follows first-order kinetics, with an activation energy of 6.7 kJ/mol, suggesting a predominantly physical mechanism driven by acoustic cavitation. Subsequent hydrolysis of the pretreated MCC using H-kaolin catalyst achieved a glucose yield of 23% and a conversion of 55% at 200 °C for 3 h. The H-kaolin catalyst exhibited excellent recyclability over four consecutive cycles, maintaining consistent performance. This combined sono-catalytic Fenton pretreatment and solid acid hydrolysis approach offers a promising strategy for efficient and sustainable cellulose valorization.

Graphical abstract