Oxidative Coupling\nof Methane over MOF-Mediated La₂O₃

Abstract

Due to the recent increase in natural gas reservoir discoveries,\nwhere methane is the main constituent, research into the upgrading\nof methane is gaining more attention. Among the techniques being explored,\nOxidative Coupling of Methane (OCM) is one of the most promising routes\nfor on-purpose ethylene production. OCM requires an efficient catalyst\nto achieve high C₂+ selectivity, and lanthanum oxide has\nlong been known to be a promising catalyst for this reaction. However,\nit is well-known that the synthesis method for OCM catalysts plays\nan important role in the performance of materials like La₂O₃ for this reaction. Herein, we report the catalytic\nperformance of La₂O₃ prepared through the use\nof an inexpensive La-based-Metal Organic Framework (La-MOF) and compare\nits activity to a conventionally prepared La₂O₃ via sol–gel (La-SG) and an off-the-shelf commercial La₂O₃ (La-C). All three catalysts exhibit the hexagonal\ncrystal structure of La₂O₃. The catalytic tests\nwere carried out between 600 and 800 °C using different feed\nratios (methane to oxygen) ranging between 3.5 and 13. Among these\nthree catalysts, La-MOF exhibits the smallest particle size of 220\nnm versus 350 and 1140 nm for La-SG and La-C, respectively. XPS results\nsuggest the formation of different surface species on the catalyst’s\nsurface which can influence the selectivity and catalytic results\nat 800 °C for a methane to oxygen ratio of 3.5 showing that the\nC₂+ yield for La-MOF was approximately 15.8%–higher\nthan 11.75% and 9.5% for La-SG and La-C, respectively.