(322d) Combined Experimental and Density Functional Theory Studies on the Modified SrTiO3 Catalysts for Oxidative Coupling of Methane

The main component of natural and shale gas, methane, attracted global attention because of the richness of deposits and significant potential for direct or indirect conversion into value added chemicals and fuels. Oxidative Coupling of Methane (OCM) is one of promising methods of adding value to methane via directly producing ethane and ethylene, vital building blocks in chemical industry. We studied modified SrTiO₃ based perovskites with metal dopants which were prepared by polymeric precursor method. A_xSr_1-xTiO₃ (A = Ba, Ca, La, Y, Li, Na, K, Rb, Cs, Al, Mg, Tl, and Pb, x = 0.2) and SrB_xTi_1-x O₃ (B = Sn, Al, Mg, Ce, Pr, Nd, Sm, and In, x = 0.2) were investigated. Also, we use density functional theory (DFT) calculations to remove ambiguity on the identification of the catalytically active site and devise descriptors for high-performance catalyst. The volcano curve was observed for C₂₊ selectivity with methyl radical adsorption energy from experimental and DFT results. The correlation indicated that the appropriate strength of methyl radical adsorption is required for improving C₂₊ compounds formation. Based on catalyst characterization using X-ray diffraction (XRD), O₂-pulse injection and temperature programmed desorption (O₂-TPD), and X-ray photoelectron spectroscopy (XPS), the influences on catalytic activity by partial replacement of cations with A- and B-site dopants were investigated.