▎ 摘　　要

In this study we report on sulfonated graphene, obtained by chemical exfoliation of inexpensive graphite and functionalization of the resulting graphene sheets with benzene sulfonic acid, as a new active catalyst for the transesterification of palm oil with methanol into biodiesel. The experimental conditions for obtaining fatty acid methyl esters were carefully optimized through the evaluation of several parameters including the catalyst loading, temperature, reaction time and methanol-to-oil molar ratio. Of particular relevance, we noticed that an excess of methanol was required to allow high transesterification yield, but an excessive dilution proved to be deleterious for the reaction yield due to lower interactions between the reactants and the catalyst. The heterogeneous catalyst showed a high thermal robustness and was successfully recycled without significant erosion of the reaction yield. Our catalytic system yields biodiesel with a high purity (>98%) after a single filtration and do not produce aqueous waste. (C) 2017 Elsevier Ltd. All rights reserved.