抄録
In this presentation emphasis has been placed on heterogeneous catalysts where phosphorous is a determining element. These correspond to phosphate based materials as vanadyl pyrophosphate used industrially for the oxidation of butane to maleic anhydride in the 630-670 K, iron phosphates and hydrogeno/hydroxy-phosphates for the oxidative dehydrogenation (ODH) of isobutyric acid to methacrylic acid in the 650-680K temperature range, zirconium hydrogeno-phosphates as layered compounds used to stabilise/entrappe catalytically active compounds as Al, Zr, or Cr, V hydroxy or hydroy-oxy macrocations species used in acid-type reactions as alkane cracking or partial oxidation reactions as ODH of light alkanes, respectively, microporous aluminophosphate molecular sieves (AIPO, MeAPO,EIAPO,..).
It is shown that the catalyst surface behave as a rather dynamic and labile surface, reconstructing under activation and/or catalytic reaction conditions and adapting itself to the stereochemistry of the reactants. In partial oxidation reactions the active sites are shown to have a molecular size and have several catalytic functions. The hydrocarbon molecule is first adsorbed, then activated, some of its hydrogen atoms are extracted while lattice oxygens are incorporated into it and electron transfer did occur through the solid material to allow oxidation reaction mechanism to proceed. The metal M cations are the active species and the role of the phosphate tetrahedra is not only to bind the MO6, octahedra together to constitute a dense or layered compound but also to bring some specific redox and acid-base properties. In the case of microporous phosphates, the active sites are more localised and static, while their chemical (redox and/or acid-base) properties, molecular and spatial structures (porosity inducing shape selectivity) turned out to be the determining factors for their catalytic properties.
