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

Abstract

The promoting effect of sulfate species in propane dehydrogenation over Fe₂O₃/γ-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 °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 Fe_xC 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.