Preparation and characterization of sulfated zirconia catalysts obtained via various procedures
(1999) Applied Catalysis A: General — Vol. 176, n° 1, p. 27-43 (1999)
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- Sulfated zirconia catalysts were prepared in two ways: (i) using colloidal sol-gel technique, when the peptization of Zr(OH)(4) precipitated with ammonia from a solution of ZrOCl2 was carried out with H2SO4 or with a solution of CH3COOH and H2SO4, respectively, and by (ii) impregnation of Zr(OH)(4). Impregnation was carried out using Zr(OH)(4) as such or using precipitated Zr(OH)(4) previously heated in suspension at 90 degrees C under reflux and strong stirring. Samples obtained following the above procedures were activated by heating in Ar or air at 550 degrees C or 650 degrees C. Sample characterization was carried out using chemical analysis, N-2 adsorption-desorption techniques, titration with propylamine in the presence of Hammet indicators, XRD, Raman spectroscopy, pyridine and CD3CN-FTIR and XPS. In the samples obtained via colloidal sol-gel technique the amount of retained sulfur was high and mono and polynucleate sulfate species as well as supported H2SO4 were found to coexist. In such conditions, both Lewis and Bronsted acid sites were identified and a large dispersion of acid strength was determined. Samples obtained via impregnation contained only a. small amount of sulfur compared with those obtained via colloidal sol-gel technique. In this case only mono and dinucleate sulfate species were found, and the acid strength exhibited a rather sharp distribution. It was also found that in that case Lewis acid sites predominate. Activation in air exhibited a positive effect upon the increase of the acidity, irrespective of the preparation variant, its presence "catalyzing" the nucleation of the superficial sulfate groups. (C) 1999 Elsevier Science B.V. All rights reserved.
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Parvulescu, V., Coman, S., Grange, P., & Parvelescu, V. (1999). Preparation and characterization of sulfated zirconia catalysts obtained via various procedures. Applied Catalysis A: General, 176(1), 27-43. https://doi.org/10.1016/S0926-860X(98)00219-1 (Original work published 1999)