Catalytic behavior of O 2-pretreated Ni 3(SbTe 3) 2 catalyst in oxidative coupling of methane

Abstract

Amorphous Ni 3(SbTe 3) 2 was prepared from a metathesis between K 3SbTe 3 and NiBr 2 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 CH 4/O 2/He in the temperature range of 600–750 °C. Although amorphous Ni 3(SbTe 3) 2 showed no catalytic activity for the oxidative coupling of methane, the O 2-pretreated Ni 3(SbTe 3) 2 was found to be active and selective for the reaction. Its C 2 selectivities were in the range of 45–79% in the temperature range of 600–750 °C. The best C 2-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 O 2-treated Ni 3(SbTe 3) 2 catalyst before and after the catalytic reaction to characterize the catalyst. Thermogravimetry (TG) analysis was performed for amorphous Ni 3(SbTe 3) 2 in a flow of O 2/Ar mixture. Electrical conductivity of amorphous Ni 3(SbTe 3) 2 was measured as a function of temperature in the range of 400–800 °C at both P O 2 ’s of 0.01 and 0.20 atm. The results suggest that NiTeO 3 formed on the surface by the O 2-pretreatment of catalyst is active and is the selective phase for the oxidative coupling of methane.