Michel Fournier

Bio: Michel Fournier is an academic researcher from university of lille. The author has contributed to research in topics: Catalysis & Reverse transcriptase. The author has an hindex of 29, co-authored 94 publications receiving 3741 citations. Previous affiliations of Michel Fournier include Lille University of Science and Technology & National Chemical Laboratory.

Acidic and catalytic properties of CsxH3−xPW12O40 heteropolyacid compounds

Abstract: The heteropolyacid of Keggin structure (H3PW12O40) and several of its cesium salts have been synthesized and characterized for their acidic properties. Chemical analysis, TGA, NH3 adsorption-desorption and31P MAS-NMR techniques permit the characterization of the Bronsted acidity. The catalytic properties were studied forn-butane isomerization and for methanol conversion to dimethyl ether at 200 and 180°C, respectively. Our conclusion is that, in term of conversion, the more acidic catalysts are in the range Cs2/2.7 if considering a wide range of acid strengths evidenced by methanol conversion. The range is Cs2/Cs2.1 if one considers only very strong acidity as evidenced byn-butane isomerization.

Catalysis by polyoxometalates. Part 3.—Influence of vanadium(V) on the thermal stability of 12-metallophosphoric acids from in situ infrared studies

Abstract: The 12-molybdo(tungsto)phosphoric acids, and the related compounds 1-vanado-11-molybdo(tungsto)phosphoric acids, all having the Keggin structure, have been studied at different temperatures in a special infrared cell allowing experiments in a controlled atmosphere. The effects of dehydration and the thermal stability are discussed. The anhydrous acids are evidenced only for the two 12-molybdo- and 12-tungsto-phosphoric acids: for the vanado compounds, the results are in agreement with the release of vanadium from the host Keggin structure, when increasing the temperature and duration of the treatments in a dry atmosphere. The effect of exposure to water vapour after the thermal treatments is also discussed.

Polyoxometalates Catalyst Materials. X-Ray Thermal Stability Study of Phosphorus-containing Heteropolyacids H3+xPM12-xVxO40 13-14H2O (M=Mo,W; x=0-1).

Abstract: The phase evolution, under thermal treatment, of the 12-molybdo(tungsto)phosphoric acids and their related 1-vanado-substituted compounds has been studied by in situ X-ray diffraction methods. The anhydrous acid temperature range is clearly observed for the 12-molybdo(tungsto)phosphoric acid parents via formation of a tetragonal phase. However, the vanadium monosubstituted acids seem to transform into the 12-metallo parents. In the case of the 1-vanado-11-tungstophosphoric acid a curious evolution, via a very stable cubic lattice, suggests thermal stabilization of the 12-tungstophosphate anion through the formation of an anhydrous VO2+ salt.

Location of Protons in Anhydrous Keggin Heteropolyacids H3PMo12O40 and H3PW12O40 by 1H{31P}/31P{1H} REDOR NMR and DFT Quantum Chemical Calculations

Abstract: HeteroPolyAcids (HPA's) are a class of solid acids that have broad applications in many fields of science and technology, including catalysis and chemical engineering. The proton locations within the thermally stable and commonly known Keggin unit, which is the primary structure building unit/block, has remained undetermined in anhydrous HPAs, despite numerous theoretical and experimental efforts. However, Rotational Echo DOuble Resonance (REDOR) NMR and Density Functional Theory (DFT) quantum chemical calculations offer a new opportunity to determine the exact locations of protons within the Keggin unit. The crucial experimental evidence is provided for the basic and very extensively studied acidic form of H(8-n)X(n+)M(12)O(40), X = Si, P and M = Mo, W, belonging to the Keggin structure. While showing that the acidic protons are located in the bridging oxygen positions (R(P-H) = 520 +/- 20 pm) in H(3)PMo(12)O(40) and in the terminal oxygen positions (R(P-H) = 570 +/- 20 pm) in H(3)PW(12)O(40), REDOR measurements also provide for the first time the structural basis to consistently rank the acid strength for the important class of Keggin solid catalysts.

Catalytic Chemistry of Heteropoly Compounds

Abstract: Publisher Summary This chapter describes the essence of the catalytic chemistry of heteropoly compounds in solution and in the solid state. The catalytic properties of heteropoly compounds have drawn wide attention, owing to the versatility of these compounds as catalysts, which has been demonstrated both by successhl large-scale applications and by promising laboratory results. Heteropolyanions are polymeric oxoanions formed by condensation of more than two different mononuclear oxoanions. Heteropolyanions formed from one kind of polyanion are called isopolyanions. Acidic elements such as Mo, W, V, Nb and Ta, which are present as oxoanions in aqueous solution, tend to polymerize by dehydration at low pH, forming polyanions and water.Heteropoly catalysts can be applied in various ways. They are used as acid as well as oxidation catalysts. They are used in various phases, as homogeneous liquids, in two-phase liquids (in phase-transfer catalysis), and in liquid-solid and in gas-solid combinations, etc.