PNNL

Abstract

H2S reforming of methane (HRM) provides a potential strategy to directly utilize sour natural gas for the production of COx-free H2 and sulfur chemicals. Several carbon allotropes were found to be active and selective for HRM, while the additional presence of transition metals led to further rate enhancements and outstanding stability (e.g., Ru supported on carbon black). Most metals are transformed to sulfides, but the carbon supports prevent sintering under the harsh reaction conditions. Supported by theoretical calculations, kinetic and isotopic investigations with representative catalysts showed that H2S decomposition and the recombination of surface H atoms are quasi-equilibrated, while the first C–H bond scission is the kinetically relevant step. Theory and experiments jointly establish that dynamically formed surface sulfur dimers are responsible for methane activation and catalytic turnovers on sulfide and carbon surfaces that are otherwise inert without reaction-derived active sites. This work was financially supported by Evonik Industries. J.A.L. acknowledges support by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES), Division of Chemical Sciences, Geosciences and Biosciences (Impact of catalytically active centers and their environment on rates and thermodynamic states along reaction paths, FWP 47319). The authors would like to thank Dr. Christian Jandl (TUM, Germany) for XPS characterization and Ms. Wangwang Zhang (X