▎ 摘　　要

An efficient and recyclable heterogeneous acid catalyst based on sulfonic-reduced graphene oxide (rGO-SO3H) has been developed and tested for transesterification reaction of soybean oil to produce biodiesel. By combining various techniques we show a high amount of sulfonic groups (12.1 +/- 0.71 mmol g(-1)) were chemically bounded onto the surface of reduced graphene oxide sheets. The catalyst rGO-SO3H shows high biodiesel production (99% yield) and was used in five consecutive reactions without losing its activity. The excellent performance and recyclability of the catalyst can be related to the high content of sulfonic groups bounded to rGO, to the unique bi-dimensional structure of the catalyst, which facilitates mass transfer and to the formation of C-SO3H bonds in rGO which are stable enough to avoid leaching of the active sites up to the fifth cycle of reaction. Therefore, we demonstrate that the material rGO-SO3H is an efficient and promising heterogeneous catalyst for acid-catalyzed transesterification reactions.