Influence of small amounts of tungsten on the physico-chemical and catalytic properties of PMo11–xWxVO4–40 heteropolyanions
- 1 January 1993
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions
- Vol. 89 (17) , 3301-3306
- https://doi.org/10.1039/ft9938903301
Abstract
The preparation, characterization and catalytic properties of acids with the general formula H4PMo11–xWxVO40, x= 0–6, and their pyridinium salts are described. The 31P NMR spectra reveal that the solids synthesized are mixtures of species with different x values. Three distinct stoichiometric ratios of W : Mo (1 : 10, 2 : 9, 3 : 8) have been used to vary the proportion of each species in these solids (labelled y= 1, 2 and 3). Their thermal stabilities and redox properties in solution are close to those of pure H4PMo11 VO40. Their Brønsted acidity increases in the order y= 1 < y= 2 < y= 3. Their catalytic properties for the oxydehydrogenation of isoubtyric acid methacrylic acid are modified drastically. An important decrease in oxidative activity and an increase in acid activity are observed even with small amounts of tungsten. Tungsten may modify either the electronic transfer between the Keggin units or the oxygen lability.Keywords
This publication has 19 references indexed in Scilit:
- Polyoxometalates catalyst materials: X-ray thermal stability study of phosphorus-containing heteropolyacids H3 +xPM12 –xVxO40·13–14H2O (M = Mo,W; x= 0–1)Journal of Materials Chemistry, 1992
- Mo/W interchange of heteropolyanions as a measure of stability: a 31P NMR studyJournal of Molecular Catalysis, 1990
- Über die thermischen Eigenschaften von Heteropolysäuren des Typs H3+n[PVnMo12−nO40] · x H2O (n = 0, 1, 2, 3) I. Thermogravimetrische, UV‐VIS‐ und röntgenographische UntersuchungenZeitschrift für anorganische und allgemeine Chemie, 1985
- 12-Heteropolymolybdates as catalysts for vapor-phase oxidative dehydrogenation of isobutyric acid 3. Molybdotungstophosphoric and molybdovanadophosphoric acidsJournal of Catalysis, 1984
- Application of temperature-programmed desorption to the study of heteropoly compounds: Desorption of water and pyridineJournal of Catalysis, 1984
- Phosphorus-31 NMR studies on molybdic and tungstic heteropolyanions. Correlation between structure and chemical shiftInorganic Chemistry, 1977
- Spectres i.r. et Raman d'hétéropolyanions α - XM12O40n− de structure de type Keggin (X = BIII, SiIV, GeIV, PV, AsV et M = WVI et MoVI)Spectrochimica Acta Part A: Molecular Spectroscopy, 1976
- Complex hydrogen bonded cationsJournal of Molecular Structure, 1973
- Differential Thermal Analysis of Some Heteropoly Acids of Molybdenum and Tungsten.The Journal of Physical Chemistry, 1955
- The structure and formula of 12-phosphotungstic acidProceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character, 1934