[en] Attempts to prepare and to characterize new catalysts belonging to the (V-P-Mo-O) system selective in the mild oxidation of butane or butene to maleic anhydride lead to the conclusion that molybdenum can be substituted up to 7% in VOPO₄ phases. Thermal analysis of the hydrated precursor, XRD, ESR spectroscopies, UV-visible and IR spectroscopies of both hydrated and anhydrous solid phases obtained show that the solid solutions isostructural with VOPO₄ 2H₂O and α₁-VOPO₄, respectively, can be formulated: [(VO)/sub 0.07/²⁺(VO)/sub 0.93/^3-(MoO₄)/sub 0.07/^2- nH₂O] (n = 1 to 2) and [(VO)/sub 0.93/³⁺(VO/sub 0.07/^3-(MoO₄)/sub 0.07/^2-]

[en] The influence of lanthanum aluminate, LaAlO₃, on the thermal stability of both alumina and platinum supported alumina catalysts is investigated. In the case of alumina, the stabilization is interpreted in terms of structural coherence between δ-Al₂O₃ and a three-fold superstructure of LaAlO₃. The addition of LaAlO₃, is shown to increase both the dispersion and the resistance to sintering of the platinum supported alumina catalyst. Moreover, lanthanum hexa-aluminate (La-β-Al₂O₃) is present in the platinum catalyst fired at 1150⁰C. These observations are assumed to result for the epitaxial relations between platinum and the lanthanum-alumina support. 23 refs.; 8 figs.; 2 tabs