Heteroatom-doping regulated Mg6MnO8 for improving C2+ hydrocarbons during chemical looping oxidative coupling of methane

Chemical looping oxidative coupling of methane (CLOCM) is a novel process for the selective oxidization of methane to produce C-2(+) hydrocarbons. However, the high activity of oxygen carriers usually promotes the undesired complete or partial oxidation of methane to form large amounts of COx. Herein, a series of novel composite oxide carriers of Mg 6 MnO 8 doped by hetematoms (Na, W, and P) are developed to achieve selective and stable production of C-2(+) hydrocarbons from CLOCM of methane. The redox performance of hetematom-doped Mg6MnO8 was evaluated in a U-tube reactor coupling with various analytical methods. It is found that Na doping can improve the content of surface O- and Mn2+/Mn3+ species of Mg6MnO8, thus improving the C-2(+) selectivity and yield. The highest C-2(+) selectivity of 82.9% and the highest C-2(+) yield of 23.2% are obtained on 4Na-Mg6MnO8 and 10Na-Mg6MnO8, respectively. The co-doping of W can stabilize the surface Na species via the formation of Na-O-W and Na-O-Mn bonds, thus resulting in the stable performance of NaW-Mg(6)MnO(8 )in 20 redox cycles. It is thus concluded that the key to achieving CLOCM with high C-2(+) selectivity and yield is the stable formation of surface O- and Mn2+/Mn3+ species of oxygen carriers regulated by doping of hetematoms.

Automated summary

A novel composite oxide carrier doped by hetematoms was developed for the selective and stable production of C-2(+) hydrocarbons from methane in chemical looping oxidative coupling. Doping with Na improved the surface O- and Mn2+/Mn3+ species content, leading to higher C-2(+) selectivity and yield. Co-doping with W stabilized surface Na species, resulting in stable performance.