Effect of χ-alumina addition on H2S oxidation properties of pure and modified γ-alumina

The influence of the textural and acidic properties of gamma-Al2O3, (gamma+chi)-Al2O3, and alpha-Al2O3 on the catalytic activity, selectivity, and stability of direct H2S oxidation has been studied. A comparison of the H2S-to-S conversion effectiveness of aluminas with their acidic properties (identified by Fourier transform infrared spectroscopy and temperature programmed desorption of NH3) shows that H2S adsorption occurs predominantly on weak Lewis acid sites (LAS). gamma-Alumina samples containing a chi-phase and/or modified Mg2+ ions have a greater concentration of weak LAS and exhibit greater catalytic activity. When alumina is treated with a sulfuric acid solution, strong LAS appear and the number of LAS decreases significantly. Modification of alumina with hydrochloric acid has a limited effect on LAS strength. Weak LAS are retained and double in number compared to that present in the unmodified alumina, but the treated sample has Al-Cl bonds. Alumina samples modified by sulfate and chloride anions exhibit poor catalytic activity in H2S oxidation. (C) 2018, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.