Variation of Conditions of ZrO2•nH2O Precipitation and Aging as a Method for Controlling the Phase Composition and Texture of ZrO2

Abstract

The effect exerted by precipitation method, temperature and duration of ZrO2·nH2O aging on the porous texture, phase composition and thermal transformations of ZrO2·nH2O and ZrO2 has been studied. It was found that variation of precipitation method makes it possible to change the specific surface area, volume and mean pore size of ZrO2·nH2O and ZrO2, increase the contribution of mesopores to the pore space of ZrO2·nH2O, and alter the particle size of ZrO2. An increase in the aging temperature of ZrO2·nH2O led to a considerable development of the mesoporous structure, an increase in the specific surface area of ZrO2·nH2O and ZrO2, and a decrease in the ZrO2 particle size. However, the ratio of ZrO2 phases changed non-monotonically with extending the aging time. Selection of precipitation and aging conditions provided a twofold increase in the pore volume of ZrO2 as compared to the sulfated zirconia isomerization catalyst and allowed extending the surface area without the introduction of additional components. The best characteristics of the ZrO2 pore structure – Ssp = 140 m2/g and Vpore = 0.404 cm3/g – are achieved when precipitation is performed at a constant pH and is followed by ZrO2·nH2O aging at 90 °С for 12 h.