Oxidative Coupling of Methane to Ethylene Over La2O3-CaO Catalyst: Kinetics and Selectivity Analysis

Abstract

The oxidative coupling of methane (OCM) offers a promising route for the direct conversion of natural gas into higher-value hydrocarbons such as ethylene and ethane. This study investigates the performance of a La₂O₃–CaO catalyst for the oxidative coupling of methane with emphasis on reaction kinetics, product selectivity, and catalyst efficiency under varying operating conditions. Experimental analyses were conducted in a fixed-bed reactor to evaluate the influence of reaction temperature, methane-to-oxygen ratio, catalyst composition, gas hourly space velocity, and residence time on methane conversion and hydrocarbon yield. Results demonstrated that the La₂O₃–CaO catalyst exhibited strong catalytic activity and enhanced selectivity toward C₂ hydrocarbons due to the synergistic interaction between lanthanum oxide and calcium oxide active sites. Optimized operating conditions significantly improved ethylene formation while minimizing complete oxidation reactions leading to carbon monoxide and carbon dioxide production. Kinetic evaluation revealed that methane activation and surface oxygen species play critical roles in determining reaction pathways and hydrocarbon selectivity. The catalyst promoted effective radical-mediated coupling reactions that enhanced C₂ product generation under controlled oxygen availability. Catalyst characterization studies confirmed good thermal stability and sustained catalytic performance during prolonged reaction operation. Comparative analysis indicated that the La₂O₃–CaO catalytic system provides improved selectivity and conversion efficiency compared with conventional oxide catalysts used in oxidative methane conversion processes. Furthermore, the study highlights the importance of catalyst design and process optimization in achieving efficient utilization of methane resources for petrochemical production. The findings demonstrate the potential of La₂O₃–CaO catalysts as effective materials for selective methane valorization and sustainable ethylene production in industrial catalytic processing applications.