Acidity, sulphur coverage and XPS analyses of ZrO2-SO4 powders by different procedures

ZrO2-SO4 powders have been prepared by following either hydrothermal or room temperature precursor preparative routes and adopting different sulphation procedures. All the samples have been calcined at the same temperature (470 degrees C) and for the same time length (5 h), and have been characterised as to phase composition (XRD) and surface area (BET). The determinations of the actual acidity (pK(a)) and density of the oxide surface sites have been obtained by a revised Hammett-Bertolacini technique. The powder sulphur contents were obtained by elemental analyses. XPS analyses of the samples have been obtained by elaboration of the S 2p and Zr 3d spectral regions. XPS data are discussed with respect to the conditions of the powders preparation and cross-compared with acidity characterisations and sulphur contents. (C) 1999 Elsevier Science B.V. All rights reserved.