Preparation Of Pt/Al2O3 Catalysts By Sol-Gel Process And Its Application To Uranyl Ion Reduction

Abstract

ABSTRACTVarious kinds of active alumina supports were obtained in the following steps: (1) preparation of alumina sols by extraction of nitrates with Primene JMT from aluminium nitrate solution, (2) gelation to spherical particles (with diameter < 100 μm) by extraction of water from sol emulsion in 2-ethyl -1-hexanol, (3) sometimes conversion of NO3− stabilized gel to OH− form by reaction with ammonia, (4) calcination of gels to γ-Al2O3 with specific surface area >100 m2/g at 500°C . The powders were then impregnated with chloroplatinic acid and recalcined at 500°C. Catalysts were also prepared by direct gelation of alumina sol containing hydroplatinic acid followed by steps (3) and (4). Pt/Al2O3 catalysts were used for reduction of 1M UO2(NO3-0.5M HCOOH solution with hydrogen at atmospheric pressure. The course of the reduction was controlled analytically and by measuring the U(VI)/U(IV) redox potential. It was concluded that the catalysts obtained by impregnation of supports prepared from nitrate stabilized gels exhibit the best activity and stability.