Catalytic behavior of O2-pretreated Ni3(SbTe3)2 catalyst in oxidative coupling of methane Original Research Article

Amorphous Ni3(SbTe3)2 was prepared from a metathesis between K3SbTe3 and NiBr2 solution and was examined as a catalyst for the oxidative coupling of methane in a single-pass flow reactor system using on-line gas chromatography at atmospheric pressure. Catalytic reaction was performed by feeding the reaction mixture containing CH4/O2/He in the temperature range of 600–750 °C. Although amorphous Ni3(SbTe3)2 showed no catalytic activity for the oxidative coupling of methane, the O2-pretreated Ni3(SbTe3)2 was found to be active and selective for the reaction. Its C2 selectivities were in the range of 45–79% in the temperature range of 600–750 °C. The best C2-yield was 11% with a selectivity of 79% at 650 °C. X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses were performed for the O2-treated Ni3(SbTe3)2 catalyst before and after the catalytic reaction to characterize the catalyst. Thermogravimetry (TG) analysis was performed for amorphous Ni3(SbTe3)2 in a flow of O2/Ar mixture. Electrical conductivity of amorphous Ni3(SbTe3)2 was measured as a function of temperature in the range of 400–800 °C at both PO2’s of 0.01 and 0.20 atm. The results suggest that NiTeO3 formed on the surface by the O2-pretreatment of catalyst is active and is the selective phase for the oxidative coupling of methane.