Acetalization of glycerol over silicotungstic acid supported in silica

Abstract

The acetalization of glycerol with butanal was carried out in the presence of silicotungstic acid (HSiW) immobilized in silica, by sol-gel technique, at 70ºC. The products of glycerol acetalization with butanal were (Z + E)-(2-propyl-1,3-dioxolan-4-yl) methanol and (Z + E)-2-propyl-1,3-dioxan-5-ol. Catalysts with different amount of HSiW were prepared. The catalysts were characterized by FTIR, XRD, ICP and N2 adsorption. It was observed that the catalytic activity increases with the amount of HSiW in silica, being the HSiW2@S (with 5.7 wt. %) the most active material. All catalysts showed high values of selectivity to (Z + E)-(2-propyl-1,3-dioxolan-4-yl) methanol (about 78-83%). As the catalyst HSiW2@S exhibited the highest activity, it was also used in acetalization of glycerol with hexanal, heptanal and octanal. A decrease of catalytic activity with the length of aldehyde was ob-served. Catalytic stability of the HSiW2@S material was studied. After the third use, the catalytic activity stabilized.