This review summarizes published data on catalytic performances of different vanadium-containing oxides, including unsupported and supported V2O5, vanadates, solid solutions and mixed phases, in the oxidative dehydrogenation of C2–C5 alkanes. The analysis of the structure-activity relationships shows that various species characterized by a different reactivity exist on the surface of these catalysts. There are some indications that tetrahedral vanadium species are the most favourable for alkane oxidehydrogenation. Its intrinsic activity seems to be largely dependent on the structure of the nearest surrounding and, therefore, can be modified by changing the nature and number of the neighbouring ions. Although the reaction mechanism is generally accepted to be through the redox cycle between V5+ and V4+, opposite relationships between catalyst activity/selectivity and reducibility have been established, even for the same catalytic systems. No clear interpretation regarding the mode of alkane activation can be derived from a survey of the literature. This and some other aspects of the reaction mechanism need further studies at a molecular level.

Oxidative dehydrogenation of lower alkanes on vanadium oxide-based catalysts. The present state of the art and outlooks

The present review analyses the literature data reported on the partial oxidation of propane to organic compounds (acrolein, acrylic acid and acrylonitrile) over mixed metal oxides, mainly magnesium vanadates, vanadia bismuth molybdates and vanadia antimony. The data were compared to those reported on the partial oxidation of propylene over bismuth molybdate and antimony—tin multicomponent oxides and over cuprous simple oxide. For both reactions, we analyzed the involved reaction mechanisms, intermediate species, active phases and active sites. The role of water produced during the reaction and that of the Bronsted acid sites were shown to be important in the determination of the selectivity of the expected products. The main conclusion of our study is that a good mix of acid-base and redox properties of the oxide surface should permit a controlled orientation of the reaction towards selective products.

On the partial oxidation of propane and propylene on mixed metal oxide catalysts

The use of mild hydrothermal methods to synthesize vanadium oxides is reviewed, with particular emphasis on those with layer and 3-dimensional structures. A wide range of studies has been performed predominantly in the past decade to grow new materials that might have interesting electrochemical and magnetic properties. Most emphasis has been placed on vanadium oxides that contain organic species or simple cations such as the alkali metals, alkaline earths, zinc and copper. The key parameters determining the structures formed are reviewed, including pH and the organic structure-directing ion. Some initial electrochemical studies are described.

Hydrothermal Synthesis of Vanadium Oxides

Oxidative dehydrogenation of propane over VMgO catalysts

The present work is dedicated to a crystal-chemical and topographical analysis of vanadium oxides with open structures. The review covers, apart from a few exceptions, only pure vanadium oxide structures with vanadium in oxidation states greater than +3. Purely tetrahedral frameworks are not discussed because of their traditional, well known crystal chemistry and only a few examples of cluster compounds are provided. Structural classification and notation of vanadium oxide frameworks are proposed based on the following scheme: polyhedra → chain → layer → three-dimensional framework. Thus, approximately 60 types of vanadium oxide frameworks are divided into five classes by type of coordination polyhedra present and into 14 subclasses by a more complex structural formation. Details are also given of the analysis of vanadium–oxygen coordination polyhedra and their metamorphosis: tetrahedron–trigonal bipyramid–square pyr­amid–octahedron, as well as the combinatorial deduction of possible structures for the most common framework types.

Structural chemistry of vanadium oxides with open frameworks

Bidimensional magnetic properties of β-Sr2MnO4

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Jean-Claude Bouloux

Papers

Bidimensional magnetic properties of β-Sr2MnO4

Structure cristalline de l'hypovanadate CaV4O9

Les hypovandates alcalinoterreux. Evolution structurale de la série CaVnO2n+1(n = 1, 2, 3, 4)

Proprietes magnetiques de la phase Sr1,50La0,50MnO4

Les hypovanadates de magnésium MgVO3 et MgV2O5. Structure cristalline de MgVO3