V2O5 – SmVO4 mechanical mixture: oxidative dehydrogenation of propane.

B. P. BARBERO; L. E. CADÚS

APPLIED CATALYSIS A-GENERAL

Elsevier

Año: 2002 vol. 237 p. 263 - 273

0926-860X

V2O5, SmVO4 and the mechanical mixtures of them in two different mass ratios were studied in the reaction of oxidative dehydrogenation of propane to propene. The results of the catalytic activity indicate the presence of a synergy effect in the yield to propene at reaction temperatures lower than 450°C. This synergy effect disappears when the reaction temperature increases. When the catalysts tested at 500°C were re-evaluated at low temperatures (350–400°C), a significant decrease in yield to propenewas observed. By the results of physicochemical characterization (BET, X-ray diffraction (XRD), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS)), it can be inferred that the synergy would be due to a transient state of the catalytic system. In it, surface vanadium species adsorbed on the SmVO4 and originated by V2O5 migration would constitute active and selective centers for the oxidative dehydrogenation of propane. The reason for the loss of synergy when the reaction temperature increases would be that the transformation of the catalytic system continues towards the coverage of SmVO4 phase by V2O5. Thus, the surface of SmVO4 is covered by conglomerates of surface VOx species and even recrystallized V2O5. This surface transformation modifies the catalytic performance of the system.