Vanadium oxide catalysts supported on titania and zirconia: II. Selective oxidation of ethane to acetic acid and ethylene Original Research Article

The performances in ethane oxidation of VOx/zirconia and VOx/titania (anatase) catalysts prepared by various procedures (see part I) are compared with a reference to H4PMo11VO40 (HPA) supported on the same supports. Acetic acid is produced in small amounts (yield <0.2 mol%) between 200 and 350 °C in the decreasing order HPA/titania > HPA/zirconia > VOx/titania. In the case of VOx/zirconia, no acetic acid is produced; this is ascribed to the more basic character of zirconia, which strongly holds adsorbed acetic acid (HPA covers completely zirconia). The performance in ethylene production is determined by the type and content of the active phases, the nature of the support and the preparation procedure (impregnation by a colloidal vanadia solution, by ammonium metavanadate or by HPA, grafting of vanadylacetylacetonate). The dispersion of VOx entities depends on the deposition procedure and the production of ethylene decreases along colloid deposition > grafting > impregnation. The best performances are obtained on VOx/zirconia catalysts prepared by colloid deposition, with 75 mol% ethylene selectivity and 16 mol% ethylene yield.