Unique catalysis of an acidic salt of heteropoly acid, Cs2.5H0.5PW12O40, consisting of microcrystallites

Catalytic functions of Cs2.5H0.5PW12O40, an acidic salt of dodecatungstopho sphoric acid, were investigated for hydration of olefins in large excess wa ter and pinacol rearrangement in a solvent-free solid-solid system. Cs2.5H0 .5PW12O40 worked as insoluble fine particles constructed by aggregated micr ocrystallites during the hydration; the particle size was deternined to be 40-200 nm when dispersed in water. Hydration of 2,3-dimethyl-2-butene was e fficiently catalyzed by the fine particles at 343 K, Furthermore, the heter opoly compound catalyzed solid-solid pinacol rearrangement at room temperat ure, the mesoporous structure of Cs2.5H0.5PW12O40 being retained. The catal ytic activities of Cs2.5H0.5PW12O40 for these reactions were found to be hi gher than those of other conventional solid catalysts. (C) 1999 Elsevier Sc ience B.V. All rights reserved.