Facile synthesis of chitosan-derived sulfonated solid acid catalysts for realizing highly effective production of biodiesel

Biodiesel, a significant kind of renewable clean energy source, has largely alleviated the environmental pressures that are now taking a sinister form. In this study, N-doped sulfonated hydrothermal carbon (NTC-SO3H) which came from chitosan, was fabricated by facile hydrothermal carbonization (HTC) technique and successfully applied to biodiesel production from oleic acid (OA). Notably, NTC-SO3H had abundant active sites (3.4 mmol/g), favorable specific surface area (15.4 m2/g), and suitable mesoporous structure (12.1 nm). Hence, NTC-SO3H showed a good catalytic efficiency under mild conditions (82.0 °C for 4.3 h, 98.6% yield) via response surface methodology optimization (RSM). Bracingly, the esterification reaction conformed to pseudo-first-order kinetics with a low activation energy (Ea) of 31.5 kJ/mol. Furthermore, NTC-SO3H showed good reusability after 5 cycles and great universality in substrate expansion, demonstrating its industrial-scale applications. Moreover, the cost analysis of catalyst preparation (6.5 $/kg) indicated that the developed catalyst has reduced production costs and proved profitable to commercialize. Therefore, NTC-SO3H prepared from renewable biomass by a facile HTC method has a high and stable activity and shows great potential in industrial biodiesel production, advancing the process of carbon neutrality.