Well-defined lanthanum ethylenediaminetetraacetates as the precursors of catalysts for the oxidative coupling of methane

Water-soluble metal organic framework (MOF) complex [La5Cl2(edta)(3)(H2O)(18)](n)Cl-n.8nH(2)O (1) is converted to its nitrate or sulfate derivatives [La-2(NO3)(2)(edta)(H2O)(5)](n).3nH(2)O (2), [La-2(SO4)(edta)(H2O)(3)](n) (3) (H-4 edta = C10H16N2O8, ethylenediaminetetraacetic acid). The three well-defined complexes are further calcinated for the preparations of pure lanthanum oxides LaOCl, La2O2CO3 and La2O2SO4 or their mixtures respectively. The oxides from 1 to 2 show good catalytic performances for the oxidative coupling reaction of methane (OCM). Their conversions of methane and the selectivities to C-2 achieved 24.5%, 39.2% and 28.0%, 47.4% respectively at low temperature 550 degrees C, while the pure La2O2SO4 from 3 is not active at low temperature. The latter is contradict to the result by simple treatment of La-2(SO4)(3) reported previously. (C) 2015 Elsevier B.V. All rights reserved.