Lithium Chemistry of Lithium Doped Magnesium Oxide Catalysts Used in the Oxidative Coupling of Methane a

Active sites are created on the surface of a Li/MgO catalyst used for the selective oxidation of methane by the gradual loss of carbondioxide from surface carbonate species in the presence of oxygen. Decomposition of the carbonat~ species in the absence of oxygen is detrimental to the activity of the cataIy~t. The active sites'created are not stable but disappear either as a result of reaction with S iO2~ fort 0 Li2SiQ Dr by the formation and subsequent loss of the volatile compound LiOH. hug~neral th~adAti~on of water to the gas feed is detrimental to the stability of the catalyst. In the case of Li2CO3 strongly bonded on the surface of Li/MgO catalyst, the decomposition of the carbo~te and thus the initial activity, can be enhanced by the addition of water to the gas feed. The addi~bn-of carbon dioxide to the gas feed results in a poisoning of the catalyst, the degree of this poisoning depending on the activity of the catalyst. The deactivation of the catalyst can be retarded if low concentration of carbon dioxide are added to the reaction mixture. It is possible to improve the stability of the catalyst by periodic reversal of the direction of flow of the gas steam.