KINETIC INVESTIGATION OF THE OXIDATIVE DEHYDROGENATION OF ISOBUTYRIC ACID ON A FE-P-O CATALYST - ROLE OF WATER

The oxydehydrogenation of isobutyric acid (IBA) on a Fe-P-O catalyst leads to mainly acetone, propene and methacrylic acid (MAA), all of them being primary products. Presence of water in the feed is essential for activating the catalyst. Good selectivity in MAA is obtained when p(H2O)/p(IBA) is higher than 6. The catalytic performances are also dependent on the oxygen partial pressure. All the kinetic data are interpreted with a preliminary step involving the activation of the Fe-P-O phase by water and a Mars-Van Krevelen mechanism related to the presence of a Fe2+/Fe3+ redox couple.