Preparation and Characterization of Porous SiO2-Al2O3-ZrO2 Prepared by the Sol-Gel Process

Abstract

An experimental strategy was developed to obtain Si—Al—Zr transparent sols via the sol-gel process. The sol was prepared from Al(OBus)3 (OBus: C2H5CH(CH3)O), Zr(OPrn)4 (OPrn: OCH2CH2CH3) and Si(OEt)4. The chelating agents acetylacetone (2, 4 pentanedione, acacH), and itaconic anhydride (2-methylenesuccinic anhydride, anhH) were employed separately to stabilize Al and Zr precursors in order to control their chemical reactivity, avoiding precipitation. In all cases a prehydrolyzed tetraethyl orthosilicate (TEOS) sol was the Si source. We use the Partial Charge Model as a theoretical indication of the stabilization of the Al and Zr species derived from the reaction with anhH and acacH. The sols were polymerized at room temperature (293 K) to obtain gels and these were dried and calcined at 673, 773 and 873 K in air. The characterization techniques were Small Angle X-ray Scattering (SAXS), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Thermal Gravimetric (TGA) and Differential Thermal Analyses (DTA). The porosity and surface area of solids calcined at 673, 773 and 873 K were determined by N2 adsorption/desorption isotherms. The corresponding average pore diameter was evaluated using the methods BJH, HK and DA. These models were used because all together cover the full range of the pore size.