Improvement of the catalytic performance of supported (NH4)3HPMo11VO40 catalysts in isobutane selective oxidation

Structural Evolution under Reaction Conditions of Supported (NH4)3HPMo11VO40 Catalysts for the Selective Oxidation of Isobutane

“…At 540 °C, the very small V2p3/2 peak was detected at around 516 eV, which was assigned to V 4+ species. The comparison with the same catalyst, but after reaction [17], shows that the proportion of V 4+ was greater. ).…”

“…It is well known that both acid and redox properties are indispensable to catalyze the oxidation of isobutane [19]. The important role of the acidic sites has been discussed elsewhere [17,18]. The absence of acid sites at the surface of the CPM support is responsible for its inertness.…”

“…(NH4)3HPMo11VO40 (APMV) was prepared by co-precipitation at 45 °C, using stoichiometric amounts of NH4NO3 (Sigma-Aldrich, Lyon, France) and H4PMo11VO40·8H2O as precursors [17]. The resulting precipitate was dried at 70 °C to obtain the APMV precursor.…”

“…The cesium salt of 12-molybdophosphoric acid, employed as a support in the following, was prepared by controlled precipitation method [17]. An appropriate amount of Cs2CO3 (Sigma-Aldrich) was dissolved in water (0.1 M) and pumped into a 0.1 M aqueous solution of H3PMo12O40 (Sigma-Aldrich) under vigorous stirring at 45 °C, generating a yellow suspension.…”

“…In an attempt to increase the surface specific reaction rate, APMV was dispersed on different types of SiO2-based supports with high surface area, and on the cesium salt of 12-molybdophosphoric acid, Cs3PMo12O40 (CPM). Only the latter was found to increase the catalytic performance as well as to stabilize the APMV active phase [17,18]. Indeed, from the catalytic point of view, it is mandatory to maintain the integrity of [PMo11VO40] or [PMo12O40] polyanions, which are known as constituting the Keggin units, also called the "primary structure".…”