Sulfonated carbon is a green, solid acid catalyst but its surface area, separation, and recovery after utilization need to be improved. The objective of the present study was to provide an environmentally friendly and economical method to prepare magnetic sulfonated carbon composite catalyst with a large surface area using palygorskite (Plg) as the support. A magnetic sulfonated carbon/Fe3O4/Plg composite catalyst was prepared via simultaneous calcination and sulfonation of the mixture of source, p-toluenesulfonic acid (TsOH), and Fe3O4/Plg. Fe3O4 nanoparticles and Plg nanorods were encased by a carbon layer derived from sucrose and TsOH. The composite catalyst exhibited good magnetic properties and high catalytic performance for the esterification of oleic acid with methanol. Oleic acid conversion reached 88.69% after the first catalytic cycle. Plg nanorods replaced sucrose and increased the catalyst’s surface area. The introduction of Fe3O4 nanoparticles improved further the acid content and oleic-acid conversion and achieved 70.31% after five cycles. The catalyst was recycled easily using an external magnetic field and its magnetic property remained unchanged due to the protection of the carbon layer.

Here we report a facile and mild synthesis of the sulfonated graphene (PSS-RGO) catalysts by in situ polymerization of sodium p-styrenesulfonate. Graphene sheets can be used as the flat backbones to graft abundant sulfonate groups on both sides. The PSS-RGO catalysts were characterized by 1H Nuclear Magnetic Resonance (1H NMR), energy dispersive spectrometer, Raman spectroscopy, X-ray photoelectron spectroscopy, and so on. The catalytic properties of the PSS-RGO catalysts for the hydrolysis of ethyl acetate and the esterification of acetic acid with ethanol were evaluated, showing that the as-made PSS-RGO catalysts were active for both probe reactions. The possible deactivation mechanism involved in the surface catalysis of the graphene-based acid catalysts has been addressed.