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Highlights: [•] The steric hindrance mainly suppressed the reactivities of S-compounds and olefins. [•] H2S inhibition effect was severe on HDS reactivity, thus decreasing the selectivity. [•] The interconversion of Lewis and Brønsted acid sites explained the H2S inhibition. [•] The HYD pathway of the HDS reaction was principally affected. [•] Catalysts with appropriate acidic sites proportion was effective in selective HDS. [ABSTRACT FROM AUTHOR]

Abstract: Presulfided CoMoS/γ-Al2O3 catalysts with sharp and deep eggshell concentration profiles of Co and Mo were prepared by a simple method and their properties were characterized by EDS, HRTEM, and FT-IR techniques. It was found that the Co eggshell thickness of the as-prepared catalysts could be conveniently regulated by controlled evaporation depth of the pre-soaked n-decane in the outer layer of the catalyst extrudates prior to the impregnation process, and the remaining n-decane in the core of the extrudates could prevent the diffusion of the acetone impregnation solution of Co(NO3)2 into that zone of extrudates. The evaluation results of the catalytic performance in hydrodesulfurization (HDS) of dibenzothiophene (DBT) indicated that the eggshell catalysts showed higher HDS activity than that of the uniform catalyst. That was because the eggshell catalysts could remarkably decrease the internal diffusion limitation effect due to a short diffusion path of the reactant. In addition, the eggshell catalysts could greatly improve the utilization efficiency of the active components. [Copyright &y& Elsevier]

• Detrimental effect of sulfation on CO 2 -capturing capacity in presence of steam. • Understanding of the competitive adsorption mechanism between CO 2 and SO 2. • Detailed reaction paths of carbonation and sulfation when H 2 O molecules exist. • Comparison of CO 2 and SO 2 adsorption energies on various sites of CaO (1 0 0) surface. Calcium looping is a fast-developing second generation CO 2 capture technology. In practical looping of Ca-based sorbents, steam and SO 2 are naturally present in the flue gas subjected to CO 2 capture, due to the combustion of fossil fuels. Until now, the single effect of steam or SO 2 has been reported to have a significant impact on the CO 2 capture of sorbents. However, there are few studies on the synergistic effect of steam and SO 2 on the CO 2 sorption characteristics of sorbents, and it is poorly understood. In this study, experiments and DFT calculation are employed to clearly understand the synergistic effect of steam and SO 2 on the carbonation behaviors of sorbents. Tests were first performed under typical calcium looping (CaL) conditions with and without the presence of steam and SO 2 during the carbonation process. Results indicated that the enhancement of steam on the sulfation is obviously stronger than that on the carbonation as the CaL cycles increased, which is then verified by a series of characterization methods. According to quantitative analysis through DFT calculation, the adsorption energy of SO 2 on CaO (1 0 0) surface was found to be more than that of CO 2 in the presence of steam, indicating the preferential adsorption of SO 2 in the presence of H 2 O molecules on the CaO (1 0 0) surface. Therefore, the experimental results were verified and the competitive adsorption mechanism of SO 2 and CO 2 in the presence of steam during the carbonation process was further understood from microscopic aspect. [ABSTRACT FROM AUTHOR]