Detailed Reaction Mechanisms for the Oxidative Coupling of Methane over La₂O₃/CeO₂ Nanofiber Fabric Catalysts

Abstract

We develop and validate detailed reaction mechanisms to represent the oxidative coupling of methane (OCM) over a La2O3/CeO2 nanofabric catalyst. The reaction mechanism includes 39 reversible gas‐phase reactions and 52 irreversible surface reactions between 22 gas‐phase species and 11 surface species. We use a model‐based interpretation of spatially resolved concentration and temperature profiles measured by using a laboratory‐scale packed‐bed reactor. The reaction mechanisms are validated for inlet feed compositions in the range of 7≤CH4/O2≤11. The results are supported by a reaction pathway analysis that provides insight into the relative contributions of the gas‐phase and surface reactions to form the desired C2+ and the undesired COx products. The results provide new quantitative insights into the complex nature of the OCM chemistry, which can assist practical process and reactor development.

Model-Based Catalyst Selection for the Oxidative Coupling of Methane in an Adiabatic Fixed-Bed Reactor

“…The microkinetic model has proven to be successful in describing experimental data over 5 different catalysts in a broad range of operating conditions; with some modifications in the kinetic parameters, it has also been used by other research groups to reproduce experimental data obtained for nanofiber fabric catalysts 40 . In the present work, the following catalysts are considered: 10%wtLa-20%wtSr/CaO 37 -Heterogeneous: on the particle-scale two different phases are considered.…”

Optimizing the Reaction Performance of La2Ce2O7‐Based Catalysts for Oxidative Coupling of Methane (OCM) at Lower Temperature by Lattice Doping with Ca Cations

“…Additionally, on this catalyst, OCM reaction can only take place efficiently above 800 °C. On the basis of former studies, it is generally recognized that OCM reaction includes typically two steps, that is, the generation of CH 3 · radicals on active surface oxygen and alkaline sites, which is followed by the coupling of the CH 3 · radicals in gas phase to form C 2 H 4 . Therefore, both active surface electrophilic oxygen and alkaline sites are indispensable for the reaction , .…”

Analysis of volume‐to‐surface ratio effects on methane oxidative coupling using microkinetic modeling

“…A more elaborate description of the model has been reported elsewhere . The applicability of this model has been recently extended from spherical catalyst particles to nanofiber morphologies by Karakaya et al, after relevant adjustments in the reactor model equations …”