Cyclic Process for Propylene Production via Oxidative Dehydrogenation of Propane with N2O over FeZSM-5

Steam-activated FeZSM-5 (Si/Al = 31.3 and 0.67 wt % Fe) is a highly efficient catalyst for the N2O-mediated oxidative dehydrogenation of propane (ODHP), with propene yields up to 25% at 723 K, but strongly deactivates due to coke formation. Because the initial ODHP performance was recovered upon air-regeneration of the spent catalyst, a process for continuous propylene production via alternation of reaction and regeneration cycles has been evaluated. A tapered element oscillating microbalance (TEOM) coupled to on-line analysis of products has been applied to correlate activity, deactivation, and regeneration of FeZSM-5 by simultaneous measurement of reaction and mass changes. This information was used to optimally design the cyclic process. In a system with five fixed-bed reactors in parallel, stable propene yields >20% were demonstrated during continuous operation for 1500 min (12 cycles), using reaction and regeneration periods of 25 and 90 min, respectively, at the same temperature (723 K). This novel process is attractive for on-site C3H6 production using a lowcost source of N2O.