Abstract
<p>Vanadyl pyrophosphate (VO)<sub>2</sub>P<sub>2</sub>O<sub>7</sub> catalysts synthesized via VOPO<sub>4</sub>·2H<sub>2</sub>O were investigated by using BET surface area measurement, X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Temperature-Programmed Techniques (TPD and TPRS). H<sub>3</sub>PO<sub>4</sub> and H<sub>4</sub>P<sub>2</sub>O<sub>7</sub> were used as the phosphorus source. Only pyrophosphate phase was observed for both final catalysts after 75 hours of calcination in a reaction flow of <em>n</em>-butane/air mixture (0.75% <em>n</em>-butane/air). However, catalyst derived from H<sub>4</sub>P<sub>2</sub>O<sub>7</sub> based preparation (denoted VPD<sub>pyro</sub>) exhibit better crystallinity and slightly higher BET surface area compared to the H<sub>3</sub>PO<sub>4</sub> based preparation (denoted VPD<sub>ortho</sub>). The nature of the oxidants for both catalysts was investigated by O<sub>2</sub>-TPD. For VPD<sub>pyro</sub>, TPD showed an oxygen peak maximum at 986 K and a shoulder at 1003 K, whereas for VPD<sub>ortho</sub>, the oxygen was desorbed as two peaks maxima at 966 and 994 K. The total amount of oxygen desorbed thermally from VPD<sub>pyro</sub> (3.60×10<sup>20</sup> atom×g<sup>-1</sup>) is higher than that obtained for VPD<sub>ortho</sub> (3.07×10<sup>20</sup> atom×g<sup>-1</sup>). VPD<sub>pyro</sub> displayed a slightly improved activity and selectivity for <em>n</em>-butane oxidation. A proper amount of V<sup>5+</sup> species may have an effect on the enhancement of the catalytic activity.</p>
Highlights
Vanadyl pyrophosphate, (VO)2P2O7 catalysts currently are the most active phase to transform the only alkane used commercially in selective oxidation process from n-butane to maleic anhydride (MA)
The phosphorus sources employed for the synthesis of VOHPO4·0.5H2O reported to give a strong influence in the synthesis of vanadium phosphate catalysts [3]
The purpose of this paper is to investigate the physico-chemical properties of the vanadyl pyrophosphate, (VO)2P2O7 catalyst prepared by using two different
Summary
Vanadyl pyrophosphate, (VO)2P2O7 catalysts currently are the most active phase to transform the only alkane used commercially in selective oxidation process from n-butane to maleic anhydride (MA). The Effect of Using H4P2O7 for Synthesizing Vanadyl Pyrophosphate Catalysts washed with cold water and dried in air for 24 hours at 373 K. VOPO4·2H2O was refluxed with isobutanol for 16 hours to obtain the VOHPO4·0.5H2O precursor (denoted as Orthopre).
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