Synthesis of bio-additive fuels from acetalization of glycerol with benzaldehyde over molybdenum promoted green solid acid catalysts

摘要

The heterogeneous green solid acid catalyzed acetalization of glycerol with various benzaldehydes was investigated under solvent-free conditions. The investigated catalysts namely ZrO2 and TiO2-ZrO2, and the respective MoO3 promoted catalysts were prepared by a facile precipitation and wet-impregnation method, respectively. The physicochemical characteristics were achieved using X-ray diffraction, BET surface area, ammonia-temperature programmed desorption, Raman spectroscopy and FT-infrared spectroscopy techniques. Characterization results revealed that addition of MoO_x enhances the surface acidic properties of the oxide supports. The MoO_x/TiO2-ZrO2 catalyst exhibited a superior 74% glycerol conversion with 51% 1,3-dioxane product selectivity. Various reaction parameters were investigated to enhance the glycerol conversion as well as product selectivity. Particularly, the reaction temperature showed a significant influence on the glycerol conversion, whereas the effect of solvents was negligible. The conversion of glycerol was considerably decreased with substituted benzaldehydes due to steric hindrance. On the other hand, a high selectivity (71%) of 1,3-dioxane was obtained in the case of p-anisaldehyde. These interesting results suggest that MoO_x/TiO2-ZrO2 is a highly promising green solid acid catalyst for environmentally benign synthesis of bio-additive fuels from glycerol.