K2SO4-promoted TiO2 for the efficient oxidative coupling of methane

Abstract

The oxidative coupling of methane (OCM) into C2−3 hydrocarbons is still limited to a few types of catalysts with low product yield. Herein, we reported our discovery that a K2SO4-promoted TiO2 catalyst can effectively catalyze the OCM reactions with a C2−3 yield of up to 26 %, which is comparable to the classical Mn-NaWOx/SiO2 catalyst. Besides, this catalyst not only exhibits promising stability for at least 200 h without signs of deactivation under typical OCM conditions but also demonstrates high sulfur-resistance performance, outperforming most reported catalysts. We have evidenced that K+ ions are responsible for increasing the surface basicity of rutile TiO2, thus benefiting C2−3 selectivity. The presence of SO42− can prevent the formation of potassium titanates, which catalyze the over-oxidation of CH4. The surface lattice oxygen species are confirmed to be the active sites for selective CH4 activation, while the chemisorbed oxygen species catalyze the combustion of CH4 to CO2.