Insight into the H 2 S selective catalytic oxidation performance on well-mixed Ce-containing rare earth catalysts derived from MgAlCe layered double hydroxides.

A series of well-mixed Ce-containing MgAlCe rare earth catalysts derived from layered double hydroxides were synthesized and tested for H2 S 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 H2 S. 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.