Monaco, S.J. and E.I. Ko, “Preparation of Silica and Alumina Single Oxides from Commercial Preformed Sols”, Chemistry of Materials (Special Issue: Sol-Gel Derived Materials), Vol. 9(11), pp. 2404-2417, 1997. DOI: 10.1021/cm970271h
High surface area silica and alumina powders were prepared from four commercially available colloidal silicas (Nyacol 830, 2040, 9950, and 2034DI) and three colloidal aluminas (Dispal 23N4−20, 18N4−20, and 11N7−12). Particle size distributions of the sols were obtained from dynamic light-scattering experiments and found to deviate significantly from the nominal sizes reported by the manufacturer. The sols were gelled via several methods, dried, and calcined at 773 K and above. A spherical particle packing model based on the measured sol particle size distributions was found to account for important textural properties such as surface area and pore volume of the calcined silica powders. For the calcined alumina powders, a better predictor for the textural properties was the crystallites whose aggregates form the precursor alumina sol. Nitrogen adsorption, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, and X-ray diffraction studies of the calcined silica and alumina powders were used to characterize their structural features and transformations, hydroxyl populations, and acidic properties as a function of heat-treatment temperature. We show that the properties of metal oxides prepared from commercially available sols can be understood when such a systematic approach is taken, despite the inherent complexity of using nonmodel precursors.
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