Abstrakt:
The catalitic performance of FeMFI zeolites in oxidative dehydrogenation of propane (ODHP) with N2O and O2 is discussed in this paper. A set of Fe-MFI samples was investigated which differed in the concentration of iron, ways of preparation and activation. Iron species in zeolites do not significantly activate molecular oxygen, as all the investigated zeolites exhibited low activity in the propane oxidation with molecular oxygen. The yield of propene reached a maximum of 2 %. On the other hand, particularly over steamed Fe-zeolites, propane oxidation with nitrous oxide resulted in high propene yields, and formation of propanal and acetone. The reaction pathway. Sites exhibiting acidic properties (Broensted and Lewis sites), if present, yield significant amount of C4 hydrocarbons and aromates, and are responsible for the catalysts deactivation by coke. Steam-activated Fe-zeolites exhibited much higher activity than calcined zeolites and a lower rate of deactivation caused by lower concentration of Broensted acid sites. The propene yields range from 10 to 20 % depending on the population of the individual Fe species. We suggest that a part of well-isolated Fe species is extremely active in the propane conversion to propene, whereas there is no evidence for the activity of the oxide-like species.
