"HPA" - Heteropolyacids


Catalytic behaviour of heteropolyanions (Keggin, Dawson, etc...) in oxidation reactions
Heteropolyanions (HPA) are composed of one (or two) central XO4 tetrahedrons surrounded by MO6 octahedra. The coordination of the heteropolyanion with cations (H+, NH4+, Fe2+, Cu2+), and water molecules of hydratation stabilize the crystal. Heteropolycompounds have been proven to be useful catalytic materials in fundamental studies. This is mainly because their acid-base (Brönsted and Lewis) and redox properties can be systematically controlled by a proper choice of constituting elements of polyanions and counter cations. However, heteropolyanions are thermally less stable.
The project aims at studying the interest of using HPA's as "sacrificial matrices", taking advantage of their tendency to decompose, in order to obtain oxidation reaction catalysts which would be hard to prepare in another way.
The project is based, (i) on the one hand, on a study about the tuning of HPCs properties: 1) the primary structure (Keggin, Dawson), 2) the nature of heteroatom, its oxidation states, 3) the use or not of a support, the support's nature and texture, the HPA deposition technique, 4) "sacrifice" conditions (t° and gas); (ii) on the other hand, on a deep physico-chemical characterization of the initial matrices, of the partially sacrificed metals and of the final oxides.