Redox Properties of VPO Ammoxidation Catalysts

Abstract

The purpose of this study is to explore correlations between the molarity of V x IV/V O y proportions of (NH 4 ) 2 (V IV O) 3 (P 2 O 7 ) 2 catalysts, the vanadium valence states, and the reducibility of the vanadium on the one hand and the catalytic activity of the solids on the other. Pure (NH 4 ) 2 (V IV O) 3 (P 2 O 7 ) 2 and two ((NH 4 ) 2 (V IV O) 3 (P 2 O 7 ) 2 +V x IV/V O y ) solids (precursor V/P=1 and 1.5) are used as catalysts; the specimens are characterized by chemical analyses, different X-ray techniques (energy dispersive analysis of X-rays (EDX) and X-ray photoelectron spectroscopy (XPS)), temperature-programmed reduction (TPR), and catalytic measurements using the ammoxidation of toluene to benzonitrile as a model reaction.