Experimental and kinetic modelling study of H2S oxidation

Oxidation of H2S in an atmospheric pressure flow reactor at temperatures from 950 to 1150 K has been studied under fuel-lean conditions (1.9 < [O-2](0)/[H2S](0) < 10). The reaction is strongly catalysed by silica surface but this effect is suppressed with application of a B2O3 coating to the silica. A feature of the reaction is the high selectivity (similar to 40%) to H-2 formation, even in the presence of a large excess of oxygen. A comprehensive chemical kinetic model for H2S oxidation has been developed. The model includes detailed chemistry for disulfur interactions based on recent experimental and theoretical work. The model shows extraordinary sensitivity to the rates of a significant number of reactions that determine the radical concentrations during the oxidation process. Minor variations (< factor 3) in the rate coefficients of two of the SH self-reaction channels allows accurate description of H2S consumption profiles: on the one hand, the reaction 2SH (sic) H2S + S (followed by S + O-2 (sic) SO + O and SO + O-2 (sic) SO2 + O) is strongly branching whereas on the other, 2SH (sic) HSSH (followed by HSSH + SH (sic) H2S + HSS and HSS + SH (sic) H2S + S-2) is a powerful chain termination sequence, especially when the oxygen excess is reduced. Disulfur interactions are extremely important in the ignition and propagation of H2S oxidation even under fuel lean conditions. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.