Acid–base and oxidation catalysis on heteropolysalts with surface acid layers

Physicochemical and catalytic properties of heteropolyacids of the series H3 +nPVnMo12–nO40(n= 0–3), both pure and supported on the potassium salt K3PMo12O40, have been investigated. Thin acid coats formed on such a support display modified properties and enhanced thermal stability. In particular, it is postulated that the change in the acidic properties of the supported acids is a consequence of their modified hydration ability resulting from the epitaxial relationship with the support. Results of catalytic experiments for the oxidation of acrolein, methanol and alkanes are presented and compared for both series of the catalysts. Possible mechanisms of all these processes are proposed on the basis of experimental data and quantum-chemical calculations.