Design of organosulfonic acid functionalized organosilica hollow nanospheres for efficient conversion of furfural alcohol to ethyl levulinate

A series of propylsulfonic or arenesulfonic acid functionalized ethane-or benzene-bridged organosilica hollow nanospheres (Pr/ArSO3H-Et/Ph-HNS) were demonstrated by a one-step condensation method combined with in situ H2O2 oxidation. The key preparation route included using nonionic surfactant F127 as the soft template, 1,3,5-trimethylbenzene as the micelle expanding agent and adjusting suitable molar ratios of total Si to F127 in the initial gel mixture. The inner diameter of the Pr/ArSO3H-Et/Ph-HNS materials was ca. 10 nm, and their shell thickness was ca. 3-5 nm. As the novel organic-inorganic hybrid solid acid catalysts, the catalytic activity of the Pr/ArSO3H-Et/Ph-HNS was evaluated by ethanolysis of biomass-derived furfural alcohol to ethyl levulinate. The obtained acid catalytic activity that was superior to that of their bulk mesoporous counterparts was explained in terms of their strong Bronsted acidity and unique hollow nanospherical morphology. Finally, the recyclability of the hybrid catalysts was studied through four consecutive catalytic runs.