Simultaneous oxidative coupling of methane and oxidative dehydrogenation of ethane on the Na +/CaO catalyst

Abstract

The co-feeding of ethane during oxidative methane coupling (OCM) decreases methane conversion, the more so, the higher the concentration of added ethane. At about 20% ethane content, methane reaction almost ceases. The amount of ethane remaining in post-reaction gases begins to be smaller than that supplied to the reaction only at its concentrations in the methane+ethane+oxygen mixture exceeding 2 mol%. At higher concentrations of ethane fed into the reaction, the magnitude of its conversion becomes stabilized at a constant level of 20–60%, depending on the conditions of the reaction. Along with the rising concentration of added ethane, the carbon contained in methane and ethane undergoing reaction towards the formation of ethylene and hydrocarbons C 3+ rises, mainly in consequence of the transformations of more highly reactive ethane. Although the presence of ethane among reagents increases ethylene content in post-reaction gases, still the ethylene/ethane ratio in these gases rises only slightly, regardless of the amount of ethane in the initial mixture of methane+ethane+oxygen. A significant finding is the lack of dependence of the value of the conversion of carbon introduced into the reaction in the form of methane and ethane to carbon dioxide on the amount of added ethane, so that the overall selectivity of hydrocarbons C 2+ formation does not deteriorate, either.