Insight into the H2S selective catalytic oxidation performance on well-mixed Ce-containing rare earth catalysts derived from MgAlCe layered double hydroxides

摘要

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 O-2 as compared to the reduction rate of Ce4+ to Ce3+ by H2S. Particularly, the added water, a Lewis base, can compete with inefficient S-8 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 S-8 catalyst to inactive S3. Thus, lead to a decrease of deposited inefficient S-8 catalyst content. Consequently, decrease the catalytic activity. (C) 2017 Elsevier B.V. All rights reserved.