| AVS 65th International Symposium & Exhibition | |
| Fundamental Discoveries in Heterogeneous Catalysis Focus Topic | Wednesday Sessions |
| Session HC+SS-WeA |
| Session: | Theory and Dynamics of Heterogeneously Catalyzed Reactions |
| Presenter: | Yong Yang, ShanghaiTech University, China |
| Authors: | Y. Yang, ShanghaiTech University, China Z. Liu, ShanghaiTech University, China E.I. Vovk, ShanghaiTech University, China X. Zhou, ShanghaiTech University, China C. Guan, ShanghaiTech University, China |
| Correspondent: | Click to Email |
Oxidative coupling of methane (OCM) is a catalytic partial oxidation process that converts methane directly to valuable C2 products (ethane and ethylene). The main difficulties from further investigation of this reaction are due to the nature of its high temperature and reaction exothermicity. In this work, a specially designed online characterization setup is applied for this reaction, which achieved both precise bed temperature control and real time product measurement. The setup combines a micro reactor and realtime mass spectroscopy. The reaction was performed under simulated industrial condition. For the first time, the Arrhenius plots of the major OCM products (CO2, ethane and ethylene) were obtained, and their temperature dependence as well as the respective activation energy barriers were clearly differentiated, over a recently reported high performance nanorod La2O3 catalyst. Different from general expectation, CO2, the fully oxidized carbon species, dominates all the products in the lower temperature region, and less oxidized C2 species are only formed at much higher temperatures. Further analysis of the Arrhenius plots indicates that selectivity and apparent activation energy for both COx and C2 products are strongly influenced by the oxygen concentration and temperature. Combined with density functional theory calculations and additional experimental measurements, significant insights are brought to this high temperature reaction of wide interest. Furtheranalysis specially focusing on this temperature region, applying XPS surface studies with in-situ high pressure cell and XRD bulk structure with operando reactor, revealed that there are both intermediates and poisoning species formation. With these new experiment results with distinguished lights-off products temperature provide new insights for understanding OCM reaction.