Oxidative Coupling of Methane over MOF-Mediated La₂O₃

Due to the recent increase in natural gas reservoir discoveries, where methane is the main constituent, research into the upgrading of methane is gaining more attention. Among the techniques being explored, Oxidative Coupling of Methane (OCM) is one of the most promising routes for on-purpose ethylene production. OCM requires an efficient catalyst to achieve high C2+ selectivity, and lanthanum oxide has long been known to be a promising catalyst for this reaction. However, it is well-known that the synthesis method for OCM catalysts plays an important role in the performance of materials like La2O3 for this reaction. Herein, we report the catalytic performance of La2O3 prepared through the use of an inexpensive La-based-Metal Organic Framework (LaMOF) and compare its 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 crystal structure of La2O3. The catalytic tests were carried out between 600 and 800 degrees C using different feed ratios (methane to oxygen) ranging between 3.5 and 13. Among these three catalysts, La-MOF exhibits the smallest particle size of 220 nm versus 350 and 1140 nm for La-SG and La-C, respectively. XPS results suggest the formation of different surface species on the catalyst's surface which can influence the selectivity and catalytic results at 800 degrees C for a methane to oxygen ratio of 3.5 showing that the C2+ yield for La-MOF was approximately 15.8%-higher than 11.75% and 9.5% for La-SG and La-C, respectively.