ROLE OF ANIONS IN THE SURFACE-AREA STABILIZATION OF ZIRCONIA

Interest in the use of zirconia as both a catalyst and a support has been growing over the last few years. The use of sulphated zirconia as a superacid catalyst has generated considerable interest because of the need to reformulate gasoline using more environmentally friendly catalysts. The presence of sulphate has been shown to enhance the stability of both the surface area and tetragonal phase of the zirconia. The influence of anions (sulphate and carbonate) on the properties of zirconium hydroxide during calcination was studied. It was concluded that the crystallization of zirconia from zirconium hydroxide occurred via three stages. The overlap of these stages is determined by both the anions present and the drying conditions. In addition sulphate increases zirconium-zirconium separation which makes oxide formation more difficult.