Chapter 5.1 Characterization of V2O5/TiO2 catalysts by solid state NMR of 51V

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Fast magic angle spinning solid-state

Catalysts V2O5 supported on TiO2 (anatase) with different contents (between 8% and 1% wt V2O5) have been studied by fast magic angle spinning solid-state 51V NMR. Two commercial supports are used (Rhône-Poulenc and Tioxide). In both samples containing 8% and 3% wt V2O5, two vanadium species in a distorted octahedral environment are observed. In the case of the smallest content (1% wt V2O5), octahedral species are always present in one support (Rhône-Poulenc), but on the other (Tioxide), a tetrahedral vanadium species appears

EPR characterization of Cr

Similar to commercial anatase samples, a well-resolved EPR spectrum has been observed in anatase-TiO2 prepared by Rhône-Poulenc. Using the X and Q-band microwave frequencies, it has been demonstrated that the spectrum is formed by two signals. One, constituted by a fine structure, has been attributed to Cr3+ ions and the other to Cr5+. It seems that these species are responsible for the spectrum when they are simultaneously present in anatase

Étude par RMN à l'état solide de catalyseurs oxydes du type Mo-P-Al

La RMN du solide et notamment la méthode “MQMAS" de 27Al est utilisée pour caractériser en détail les catalyseurs d'hydrotraitement du type Mo-P-Al sous forme oxyde. Cette application montre que la RMN est un outil efficace pour déterminer la structure locale des éléments introduits dans les catalyseurs de caractère amorphe. Ainsi, elle permet d'établir que le Mo associé au P induit la formation de phosphates d'aluminium. Des différences de structure en fonction de la méthode de préparation sont également observées.