From fundamentals to chemical engineering on oxidative coupling of methane for ethylene production: A review

• Published in: Carbon resources conversion 2022-03, Vol.5 (1), p.1-14
• Main Authors: Liu, Jiao, Yue, Junrong, Lv, Mei, Wang, Fang, Cui, Yanbin, Zhang, Zhanguo, Xu, Guangwen
• Format: Article
• Language: English
• Subjects: C2; Ethylene; Methane; OCM; Oxidative coupling of methane; Reactor
• ISSN: 2588-9133; 2588-9133
• DOI: 10.1016/j.crcon.2021.11.001

A potential application of a transport bed type of circulating reactor system in the catalytic OCM reaction is proposed. This system consists mainly of a transport bed reactor, a disengager, a cyclone and a fluidized bed vessel. Since the reactant-catalyst contact time in the transport bed reactor can be easily reduced to be extremely short by increasing the CH4/O2 feeding rate, and simultaneously the temperature of catalyst particles circulated into the bottom of the reactor be managed, the secondary oxidation of C2+ products and catalyst deactivation originated from formation of hot spots in the catalyst bed both are expected to be significantly suppressed. Schematic diagram of a transport bed type of circulating reactor system for processing of the catalytic OCM reaction. [Display omitted] •Comprehensive overview of oxidative coupling of methane for ethylene production.•Up-to-date overview of research on oxidative coupling of methane (OCM).•Survey of OCM thermodynamics, catalysts, mechanisms and reaction engineering.•Proposing a circulating reactor system for OCM reaction.•Active sites dispersed on the exterior surface to eliminate the internal diffusion. A comprehensive overview is presented to summarize the research works since 1982 on oxidative coupling of methane (OCM), a complex reaction network combining heterogeneous and homogeneous reaction steps. Fundamentals on reaction mechanisms and thermodynamics have revealed that the OCM process is highly exothermic and its C2+ selectivity and yield is critical in evaluating its commercial viability. Catalytic strategies have been put to enhance C2+ selectivity, improve C2+ yield and lower reaction temperature. The catalyst Mn-Na2WO4/SiO2 enables methane activation at a temperature of 800 °C and simultaneously a high C2+ selectivity of 70–80%, while the nanowire and La2O3-based catalysts enable to lower the reaction temperature to 200–300 °C and 500 °C, respectively. Reaction engineering aspects have also been dealt in many investigations in order to make the process technically feasible. Particularly, research works on reaction kinetics, reactor selection and reactor operating mode choice have been addressed. Intermediate cooling and distributed oxygen feed have been integrated into a multi-stage adiabatic fixed-bed reactor system to suppress the side oxidation reactions and improve the performance of the catalysts towards CH4 conversion and C2+ yield. This review paper proposes employing a circulating r