PROPANE OXYDEHYDROGENATION REACTION ON A VPO TIO2 CATALYST - ROLE OF THE NATURE OF ACID SITES DETERMINED BY DYNAMIC IN-SITU IR STUDIES/

A VPO/TiO2 catalyst tested in the oxydehydrogenation reaction (ODH) of propane between 300 and 400 degrees C shows satisfactory performances (up to 80% of propene selectivity at 2% of propane conversion at 300 degrees C or 56% of propene selectivity at 9% of propane conversion at 400 degrees C). Addition of water or pyridine in the feed gas tends t o decrease the propane conversion and enhances the propene selectivity . It is shown that water increases the number of Bronsted surface acid sites by dissociative adsorption which, in turn, enhances propene sel ectivity at the expense of the COx selectivity. These results are in g ood agreement with spectroscopic IR observations performed under catal ytic conditions showing that the Lewis acid sites are linked to COx fo rmation, whereas it seems that Bronsted sites would rather be linked t o propene formation.