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

摘要

A series of Mg2AlxFe1-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, alpha-Fe2O3, alpha-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 Fe-2(SO4)(3) species also led to catalyst deactivation.