Alkali-metal enhanced LaMnO3 perovskite oxides for chemical looping oxidative dehydrogenation of ethane

Abstract

Chemical looping oxidative dehydrogenation (CL-ODH) of ethane provides a potential method to convert ethane into ethylene by using a circulative redox catalyst (also called oxygen carrier). In this work, perovskites type oxide LaMnO3 and three kinds of alkali-metal (Na, Na3PO4 and Na2WO4) promoted LaMnO3 redox catalysts were prepared and tested for CL-ODH of ethane. Results showed that the alkali promoters not only reduce the Mn oxidation state, but also decrease the surface manganese sites. The alkali-doping induces the formation of electron-rich intermediate oxygen species, which contributes to the higher ethylene selectivity of the alkali-modified LaMnO3. As the best candidate for CL-ODH of ethane among the four catalysts, NaW-LaMnO3 exhibited a stable activity during 25 redox cycles. 85 % of ethylene selectivity and 60 % of ethylene yield was obtained, which is significantly improved in comparison to 41.16 % ethylene yield of unpromoted LaMnO3, simultaneously exhibiting less than 1 % of coke formation.