THERMALLY EFFECTED STRUCTURAL AND SURFACE TRANSFORMATIONS OF SULFATEDTIO2, ZRO2 AND TIO2-ZRO2 CATALYSTS

Preparations were characterized by specific surface area, thermogravim etry, and X-ray diffractometry. Thermal effects observed were (a) sulf ur loss, (b) sintering, (c) crystallization and transformation of the crystalline phase(s). Thermoanalytical curves indicate that decomposit ion of the sulfate occurs in two distinct steps. Decrease of surface a rea due to (b) and (c) is concomitant to decomposition of sulfate. Sul fate was found to hinder sintering, crystallization and phase transfor mations of ZrO2 and TiO2. In low-titania and -zirconia sulfated TiO2-Z rO2 the minor component enhances the effect of sulfate. In equimolar T iO2-ZrO2 sulfate decomposition is accompanied by rapid formation of cr ystalline TiZrO4.