Publication

The work presented herein reports on the oxidative coupling of methane (OCM) performance of a series of Li-free and Li-doped CeO₂ and CeO₂ modified with Sm³⁺ and La³⁺ catalysts. The supporting materials (Ce, Sm-Ce and La-Sm-Ce metal oxides) were synthesized using the microwave assisted sol-gel method in order to achieve nanophase complex materials with increased particle surface energy and reactivity. Lithium ions were added, using the wet impregnation technique, in order to further improve the physicochemical characteristics and reinforce the activity and selectivity, in terms of C₂H₆ and C₂H₄ production. All materials were characterized using N₂ adsorption-desorption, XRD, Raman spectroscopy, CO₂-TPD, H₂-TPR, SEM and XPS. We showed that the addition of lithium species changed the reaction pathway and drastically enhanced the production of ethylene and ethane, mainly for the promoted catalysts (Li/Sm-Ce and Li/La-Sm-Ce). In particular, the presence and the synergy between the electrophilic oxygen species (peroxide and superoxide), population of oxygen vacancy sites and the surface moderate basic sites determined the reaction pathway and the desirable product distribution.