Abstract: The mixed lithium-lanthnum-titanium oxide catalysts have been prepared from different Li-containing compounds(LiNO₃, Li₂SO₄)for oxidative coupling of methane, The XRD, IR, XPS, and BET resuIts showed that LiLa_0.5Ti_0.5O_2+λ catalysts prepared from LiNO₃ possessed a higher activity and space velocity, while those from Li₂SO₄ possessed a much higher C₂ selectivity, but lower activity and space velocity. The deactivation of LiLa_0.5Ti_0.5O_2+λ catalysts prepared from LiNO₃ is mainly caused by the loss of surface lithium. In the course of the coupling reaction the bulk lithium diffuses to the surface, leading to the decomposition of active phase containing lithium and lowering the amount of oxygen vacancies. In order to combine the advantages of both catalysts prepared from LiNO₃ and Li₂SO₄ and to fix the surface lithium a novel preparation method with impregnation in (NH₄)₂SO₄ is proposed.

Key words: methane, oxidative coupling, lithium-lanthanum-titanium mixed oxide, deactivation