V<sup>III</sup>V<sup>IV</sup><sub>3</sub>O<sub>3</sub>(PO<sub>4</sub>)<sub>3</sub>: A Novel Vanadium Phosphate for Selective
Oxidation of Light Hydrocarbons
posted on 2007-08-21, 00:00authored byErnst Benser, Robert Glaum, Thomas Dross, Hartmut Hibst
A novel vanadium(IV) phosphate V<sup>III</sup>V<sup>IV</sup><sub>3</sub>O<sub>3</sub>(PO<sub>4</sub>)<sub>3</sub> has been synthesized and crystallized (1073 K,
sealed silica tube, a few milligrams of PtCl<sub>2</sub> as mineralizer). According to the single-crystal structure
analysis [orthorhombic, <i>F</i>2<i>dd</i> (No. 63), <i>Z</i> = 24, <i>a</i> = 7.2596(8) Å, <i>b</i> = 21.786(2) Å, <i>c</i> = 38.904(4) Å
(lattice parameters from Guinier photographs), R<sub>1</sub> = 0.032, wR<sub>2</sub> = 0.067, κ-CCD diffractometer, 83 949
reflections measured, 6836 independent, 5986 with <i>I</i> > 2σ(<i>I</i>), 299 variables], V<sup>III</sup>V<sup>IV</sup><sub>3</sub>O<sub>3</sub>(PO<sub>4</sub>)<sub>3</sub> belongs
to the Lipscombite/Lazulite structure family. At 1073 K V<sup>III</sup>V<sup>IV</sup><sub>3</sub>O<sub>3</sub>(PO<sub>4</sub>)<sub>3</sub> is in thermodynamic equilibrium
with (VO)<sub>2</sub>P<sub>2</sub>O<sub>7</sub>, VO<sub>2</sub>, and VPO<sub>4</sub>. Substitution of V<sup>3+</sup> in V<sup>III</sup>V<sup>IV</sup><sub>3</sub>O<sub>3</sub>(PO<sub>4</sub>)<sub>3</sub> by Cr<sup>3+</sup> and Fe<sup>3+</sup> is possible.
Like vanadylpyrophosphate the oxide phosphates M<sup>III</sup>V<sup>IV</sup><sub>3</sub>O<sub>3</sub>(PO<sub>4</sub>)<sub>3</sub> (M<sup>III</sup>: V, Cr, Fe) show significant
catalytic activity in selective oxidation of <i>n</i>-butane and 1-butene to maleic acid anhydride.