Electron spin resonance studies of free and supported 12-heteropoly acids. Part 1.—Air and vacuum dehydrations of H3[PMo12O40]·xH2O and H4[SiMo12O40]·xH2O

Abstract

Air and vacuum dehydrations of SiMo₁₂ and PMo₁₂ heteropoly acids (HPA) have been studied, the sequence of Mo⁵⁺ signals detected under various conditions allowing the evaluation of different stages in the dehydration and destruction of the HPA. The stability of the HPA is shown to decrease when they are supported on Aerosil. The strong interaction of the HPA with an alumina support both influences and modifies properties characteristic of the HPA.