Aryldiazonium-grafted bamboo-derived activated carbon: a solid acid catalyst with stable C–C bonded sulfonic acid sites for biodiesel production <i>via</i> esterification

This study proposes a robust carbon-based solid acid catalyst (ACC600) prepared from bamboo waste for efficient biodiesel production <i>via</i> esterification. The catalyst was synthesised through phosphoric acid activation, followed by pyrolysis at 600 °C and subsequent functionalisation with sulfonic acid groups using an aryldiazonium sulfonation strategy. Under optimal conditions, ACC600 showed a high sulfonic acid density (1.295 mmol g^-1) and a well-developed porous structure. It exhibited excellent catalytic performance in the esterification of oleic acid, achieving 97.5% conversion under mild reaction conditions. Notably, ACC600 exhibited outstanding stability, maintaining 79.0% of its initial activity after 10 consecutive reuses, which was attributed to its rigid carbon framework effectively suppressing the leaching of active sites. The catalyst also showed promising results when applied to real-world soybean saponin acidified oil, confirming its potential for practical industrial application. This work provides a viable approach for designing highly stable solid acid catalysts from biomass for sustainable biofuel production.