Studies on the promoting effect of sulfate species in catalytic dehydrogenation of propane over Fe2O3/Al2O3 catalysts

The promoting effect of sulfate species in propane dehydrogenation over Fe2O3/gamma-Al2O3 catalysts is systematically elucidated by using iron(III) or iron(II) sulfate as the precursor, pre-treating with SO2 or introducing SO2 with propane as the reactant. At 560 degrees C, up to 23 wt% propylene yield with 80% selectivity is obtained. It is demonstrated that the introduced sulfate species exist in the form of SO42- and strongly interact with the support and Fe via the Al-O-S bond and the Fe-O-S bond. On one hand, it suppresses the formation of FexC species and thus the cracking reaction. On the other hand, it leads to an enhanced adsorption capacity of propane. Meanwhile, the initial C-H bond activation and subsequent rupture with the formation of Fe-C3H7 and OH are facilitated, resulting in excellent dehydrogenation performance. Online MS, XPS, XRD and reaction-regeneration-sulfuration results show that the loss of sulfate species by the reduction to S2- and release in the form of SO2 is the main reason for the deactivation of the sulfated catalysts.