Direct conversion of methane into ethylene through the oxidative coupling of methane (OCM) is a technically important reaction. However, conventional co-fed fixed-bed OCM reactors still face serious challenges in conversion and selectivity. In this paper, we apply a finite element model to simulate OCM reaction in a plug-flow CO2/O2transport membrane (CTM) reactor with a directly captured CO2and O2mixture as a soft oxidizer. The CTM is made of three phases: molten carbonate, 20% Sm-doped CeO2, and LiNiO2. The membrane parameters are first validated by CO2/O2flux data obtained from CTM experiments. The OCM reaction is then simulated along the length of tubular plug-flow reactors filled with a La2O3-CaO-modified CeO2catalyst bed, while a mixture of CO2/O2is gradually added through the wall of the tubular membrane. A 12-step OCM kinetic mechanism is considered in the model for the catalyst bed and validated by data obtained from a co-fed fixed-bed reactor. The modeled results indicate a much-improved OCM performance by membrane reactor in terms of C2-yield and CH4conversion rate over the state-of-the-art, co-fed, fixed-bed reactor. The model further reveals that improved performance is fundamentally rooted in the gradual methane conversion with CO2/O2offered by the plug-flow membrane reactor.
To cut CO2emissions, we propose to directly convert shale gas into value-added products with a new H2/O2co-transport membrane (HOTM) reactor. A Multiphysics model has been built to simulate the membrane and the catalytic bed with parameters obtained from experimental validation. The model was used to compare C2 yield and CH4conversion rate between the membrane reactor and the state-of-the-art fixed-bed reactor with the same dimensions and operating conditions. The results indicate that (1) the membrane reactor is more efficient in consuming CH4for a given amount of fed O2. (2) The C2 selectivity of the membrane reactor is higher due to the gradual addition of O2into the reactor. (3) The current proposed membrane reactor can have a decent proton molar flux density but most of the proton molar flux will contribute to producing H2O on the feed side under the current operating conditions. The paper for the first-time projects the performance of the membrane reactor for combined H2O/H2removal and C2 production. It could be used as important guidance for experimentalists to design next generation natural gas conversion reactors.
more » « less- NSF-PAR ID:
- 10468386
- Publisher / Repository:
- The Electrochemical Society
- Date Published:
- Journal Name:
- Journal of The Electrochemical Society
- Volume:
- 170
- Issue:
- 10
- ISSN:
- 0013-4651
- Format(s):
- Medium: X Size: Article No. 103502
- Size(s):
- ["Article No. 103502"]
- Sponsoring Org:
- National Science Foundation
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