Chemical modification of reduced graphene oxide with sulfonic acid groups: Efficient solid acids for acetalization and esterification reactions

Abstract

Surface chemical modification of reduced graphene oxide (rGO) with sulfonic acid groups produced two solid acids for acid-catalyzed reactions. One of the solid acids was prepared by covalent modification of rGO with oleum to achieve rGO-SO3H. The second solid acid obtained from the reaction of diazonium salt of para-amino benzene sulfonic acid with rGO. The prepared solid acids were characterized by various physicochemical methods which verified the successful modification of rGO with sulfonic acid groups. Catalytic activities of the obtained solid acids were evaluated and compared in the esterification of acetic acid with butanol and acetalization of benzaldehyde with ethylene glycol which indicated excellent catalytic efficiencies in both reactions. Both solid acids exhibited very high and almost identical conversion in esterification and acetalization reactions in short times, indicating the good catalytic efficiency of these solid acids for production of fine chemicals.