Catalytic behaviors of combined oxides derived from Mg/AlxFe1−x–Cl layered double hydroxides for H2S selective oxidation

Abstract

A series of Mg₂Al_xFe_1−x LDH compounds was synthesized by a one-step method. The structural and chemical properties were studied by various methods and the derived oxides were tested for H₂S selective oxidation. It was observed that the iron species existed mainly in the form of isolated Fe³⁺ species, α-Fe₂O₃, γ-Fe₂O₃ and Fe₃O₄. Moreover, the nature of the iron oxides was varied with the rise in the iron content. Significantly, the catalysts exhibited high catalytic activity and reasonable durability at a relatively lower temperature and higher GHSV. The catalysts obeyed the step-wise mechanism for H₂S selective catalytic oxidation. And the chemically adsorbed oxygen on the oxygen vacancies participated in the H₂S selective oxidation reaction and played a key role in the H₂S selective oxidation into elemental sulfur. The catalyst deactivation was due mainly to the deposit of elemental sulfur. Additionally, the small amount of the formed less active Fe₂(SO₄)₃ species also led to catalyst deactivation.