The oxidative coupling of methane (OCM) is a potential option for conversion of excess natural gas to higher value products or useful feedstocks. The preferred or ideal OCM stoichiometry is: 2CH4 + O2 → C2H4 + 2H2O, but real OCM produces a variety of species. Using a detailed mechanism from the literature for OCM over a La2O3/CeO2 catalyst that combines coupled elementary gas phase and surface reactions, a reactor engineering study has been done. Adiabatic packed bed reactor (PBR, modeled as plug flow) and continuous stirred tank reactor (CSTR, perfect mixing) simulations using this mechanism are presented. Each reactor simulation used the same total number of catalyst sites. Process variables included CH4/O2 feed ratio (7, 11), feed temperature (843–1243 K), and feed rate. All runs were conducted at 1.01E5 Pa pressure. The results show the CSTR produces high conversions at much lower feed temperatures than those required by the PBR. Once full PBR “light off” occurs, however, its CH4 conversions exceed CSTR. The simulations reveal OCM over this catalyst at these conditions gives a mixture of synthesis gas (CO, H2) and C2Hx (primarily C2H4 plus small quantities of C2H6 and C2H2). The CSTR favors the production of synthesis gas, while the PBR favors C2Hx. Within the suite of CSTR cases, C2Hx is favored at the lowest feed temperature and highest CH4/O2 feed ratio.

The catalytic activation of CH4 by limited amounts of O2 produces a mixture of synthesis gas (CO, H2) and light hydrocarbons (C2Hx), the relative amounts of each depending on catalyst type and process conditions. Using an elementary reaction mechanism for the oxidative coupling of methane (OCM) on a La2O3/CeO2 catalyst derived from the literature, this study replaces the activating O2 with moist H2O2 vapor to reduce synthesis gas production while improving C2Hx yields and selectivities. As the H2O2 content of the activating oxidant rises, more of the CH4 conversion occurs in the gas phase instead of with the catalytic surface. In a packed bed reactor (PBR), the use of H2O2 allows the PBR “light-off” to occur using a lower feed temperature. In exchange for a small decline in CH4 conversion, C2Hx selectivity increases while synthesis gas production drops. In a continuous stirred tank reactor (CSTR), H2O2 improves C2Hx over synthesis gas across a wider range of feed temperatures than is possible with the PBR. This suggests the CSTR will likely reduce OCM preheating requirements.