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

Abstract Catalytic functions of Cs 2.5 H 0.5 PW 12 O 40 , an acidic salt of dodecatungstophosphoric acid, were investigated for hydration of olefins in large excess water and pinacol rearrangement in a solvent-free solid–solid system. Cs 2.5 H 0.5 PW 12 O 40 worked as insoluble fine particles constructed by aggregated microcrystallites during the hydration; the particle size was determined to be 40–200 nm when dispersed in water. Hydration of 2,3-dimethyl-2-butene was efficiently catalyzed by the fine particles at 343 K. Furthermore, the heteropoly compound catalyzed solid–solid pinacol rearrangement at room temperature, the mesoporous structure of Cs 2.5 H 0.5 PW 12 O 40 being retained. The catalytic activities of Cs 2.5 H 0.5 PW 12 O 40 for these reactions were found to be higher than those of other conventional solid catalysts.