Insight into the H₂S selective catalytic oxidation performance on well-mixed Ce-containing rare earth catalysts...

A series of well-mixed Ce-containing MgAlCe rare earth catalysts derived from layered double hydroxides were synthesized and tested for H₂S selective catalytic oxidation. Particularly, no chemisorption O-vacancies but intrinsic defect sites were present on catalyst surface. Significantly, the catalysts exhibited excellent catalytic activity, reasonable durability, and outstanding sulfur selectivity (100%) at relatively low temperatures. Furthermore, the catalyst followed a step-wise mechanism, and the catalyst deactivation was due mainly to the slower oxidation rate of Ce³⁺ to Ce⁴⁺ by O₂ as compared to the reduction rate of Ce⁴⁺ to Ce³⁺ by H₂S. Particularly, the added water, a Lewis base, can compete with inefficient S₈ catalyst for the occupation of Lewis acid sites and active sites. Meanwhile, it can change the characteristics of catalyst surface, resulting in sulfur existing form transforming from inefficient S₈ catalyst to inactive S₃. Thus, lead to a decrease of deposited inefficient S₈ catalyst content. Consequently, decrease the catalytic activity.