Acetalization of glycerol over silicotungstic acid supported in silica

The acetalization of glycerol with butanal was carried out in the presence of silicotungstic acid (HSiW) immobilized in silica, by sol-gel technique, at 70° C. 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 N 2 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 observed. Catalytic stability of the HSiW2@S material was studied. After the third use, the catalytic activity stabilized.