WO3-based porous MCM-48 catalysts for renewable acrolein synthesis by the dehydration of glycerol

Abstract

The gas-phase selective dehydration of glycerol to acrolein was studied over x%W (x: 5, 15, 25, and 35 %, w/w) supported on MCM-48. Microporous silica MCM-48 was synthesized to produce three-dimensional cubic crystals with a high surface area and resistance to hydrolytic pressure. Tungsten oxide (WO3) based solid acid catalysts supported on MCM-48 were prepared by two distinct synthesis methods, namely, oxalic acid added sol–gel (HSG) and nonhydrolytic sol–gel (NHSG) methods. The morphological and textural properties of catalysts were characterized by XRD, BET, SEM, Raman, XPS, and FT-IR techniques. The acidic properties of catalysts were elucidated by FTIR pyridine-adsorption and NH3-Temperature Programmed Desorption (NH3-TPD). The total surface acid sites’ concentration, Brønsted (B) and Lewis (L) acid concentrations, and B/(B+L) ratios were calculated from NH3-TPD and pyridine-FTIR. The steady acrolein yields were obtained with the optimal catalysts (15 %W and 25 %W loaded MCM-48 for HSG and NHSG, respectively). This study demonstrated that the medium-strength surface acidity and B/(B+L) ratios for glycerol dehydration to acrolein were correlated with both the activity and the selectivity of acrolein.