Oxidation of H2S on activated carbon KAU and influence of the surface state

Properties of the oxidized activated carbon KAU treated at different temperatures in inert atmosphere were studied by means of DTA, Boehm titration, XPS and AFM methods and their catalytic activity in H2S oxidation by air was determined. XPS analysis has shown the existence of three types of oxygen species on carbon catalysts surface. The content of oxygen containing groups determined by Boehm titration is correlated with their amount obtained by XPS. Catalytic activity of the KAU catalysts in selective oxidation of hydrogen sulfide is connected with chemisorbed charged oxygen species (O-3.1 oxygen type with BE 536.8-537.7 eV) present on the carbons surface. Formation of dense sulfur layer (islands of sulfur) on the carbons surface and removal of active oxygen species are the reason of the catalysts deactivation in H,S selective oxidation. The treatment of deactivated catalyst in inert atmosphere at 300 degrees C gives full regeneration of the catalyst activity at low temperature reaction but only its partial reducing at high reaction temperature. The last case is connected with transformation of chemisorbed charged oxygen species into C=O groups. The KAU samples treated in flow of inert gas at 900-1000 degrees C were very active in H2S oxidation to elemental sulfur transforming up to 5 157 mmol H2S/g catalyst at 180 degrees C with formation of 1.7-1.9 g S-x/g catalyst. (c) 2006 Elsevier B.V. All rights reserved.