Solvent free cyclodehydration of sorbitol to isosorbide over mesoporous sulfated titania with enhanced catalytic performance

Mesoporous sulfated titania (MST), a solid acid catalyst has been prepared in one step by organic template free straightforward hydrolysis of titanium oxysulfate and subsequent calcination at different temperatures. The resultant nano-sized MST catalysts showed remarkable catalytic performances in solvent free cyclodehydration of sorbitol as compared to sulfated TiO₂ prepared by conventional method. The catalyst activity of MST catalysts varied with calcination temperature and MST-450 (calcined at 450 °C) exhibited highest catalytic activity and isosorbide selectivity. The MST-450 catalyzed this dehydration reaction at comparatively lower reaction temperature and produced isosorbide with high selectivity in short reaction time. The complete conversion of sorbitol with 70% isosorbide selectivity was achieved in 2 h at 180 °C. The high catalytic activity of MST catalyst attributes to its high specific surface area, large pore size and hence facile diffusion of reactants into the pores and ease to access acid sites. Moreover, the effects of calcination temperature, sulfur content, catalyst amount, reaction temperature and reaction time on conversion and selectivity were studied and the catalyst was also reused.