PS-SO3H@phenylenesilica with yolk–double-shell nanostructures as efficient and stable solid acid catalysts

Abstract

Efficient and stable solid acids have been successfully synthesized by sulfonation of polystyrene (PS) in the hollow interiors of silica-based hollow nanostructures. It was found that larger and smaller inner void spaces result in the formation of PS-SO3H@phenylenesilica respectively with double-shell (DSNs) and yolk–double-shell nanostructure (YDSNs). PS-SO3H@phenylenesilica with DSNs and YDSNs nanostructure shows comparable activity and is more active than Amberlyst-15 in the esterification reaction. PS-SO3H@phenylenesilica with YDSNs nanostructure affords higher activity than that with DSNs nanostructure in the Friedel–Crafts alkylation of toluene with 1-hexene, which is mainly attributed to the fact that the unique YDSNs nanostructure could slow down the swelling rate of PS-SO3H during the catalytic process. More importantly, PS-SO3H@phenylenesilica with YDSNs nanostructure showed much higher recycle stability than Amberlyst-15 in the Friedel–Crafts alkylation of toluene with 1-hexene, probably due to the high thermal stability of the sulfonic acid group and the unique YDSNs nanostructure.