Aerogel and xerogel WO3/ZrO2 samples for fine chemicals production

WO3/ZrO2 systems were prepared by sol–gel technique using different procedures for the solvent extrac- tion: evaporation in vacuum at room temperature (xerogel) and extraction in supercritical conditions (aerogel). Two reactions of industrial interest were investigated under mild conditions: (i) acylation of veratrole with acetic anhydride; (ii) acylation of anisole with benzoic anhydride. Several techniques were employed in order to study the influence of the synthetic parameters on texture and catalytic activity: N 2 physisorption, Fourier transformed-infrared spectroscopy, X-ray photoelectron spectroscopy, tempera- ture programmed reduction and temperature programmed oxidation analyses. The solvent extraction strongly influences metal reducibility, surface area, pores organisation, W/Zr surface density and metallic interactions. The aerogel sample shows the best catalytic results for both conversion and yield. The super- critical extraction plays a central role especially in the recycling: by proper air activation, the aerogel sample attains the complete restoration of the catalytic activity even after three runs.