Methane is a potent greenhouse gas and the chief component of natural gas. Presently, most natural gas is combusted resulting in emissions of carbon dioxide (CO2) – also a greenhouse gas. The project investigates an alternative approach to methane utilization employing a reaction known as non-oxidative coupling of methane (NOCM). NOCM avoids the formation of CO2 by converting the methane primarily to ethylene and aromatic compounds – important precursors to a wide range of chemical products. While the reaction is not new, its potential application has been limited by incomplete understanding of the complex reaction chemistry which, in turn, complicates the design effective NOCM catalysts. To overcome those limitations, this EArly-concept Grant for Exploratory Research (EAGER) project examines the elementary reactions that occur during NOCM over a novel class of catalysts known as single-atom catalysts (SACs) using alkyl halide methane surrogate molecules. The potential of NOCM to produce alkenes and aromatics from fossil-derived and biological methane resources represents a stop-gap solution to fully carbon-neutral approaches to the manufacture of chemicals and fuels. NOCM is a highly endothermic reaction, necessitating the use of high temperatures, which leads to a significant impact of gas-phase chemistry on the observed product distribution of the surface-catalyzed reaction. The project will investigate reactions of alkyl halide molecular surrogates of methane. The surrogates allow for low temperature reactivity, thus eliminating complications associated with gas-phase chemistry contributions. The project examines the impact of SAC structure and composition on the ability to form carbon-carbon bonds to produce alkenes of varying size and aromatics. Specifically, three aspects of C-C bond formation chemistry on SACs will be investigated at moderate temperatures (200 to 400 degrees Celsius) where surface reactions prevail: (i) coupling between -CH3(ads) and =CH2(ads) surface fragments; (ii) coupling between -CH3(ads) surface fragments and C2 species (either -C2H5(ads) or C2H4(g), a product of NOCM) and (iii) surface-catalyzed aromatic formation through cyclotrimerization chemistry. The three experimental tasks will focus on quantifying reaction rates, selectivity, and mechanistic details of C-C coupling using isotopically labeled substrates. A fourth aim will focus on density functional theory-based discovery of SACs for C-C bond formation, and the development of microkinetic models for promising SAC candidates. The catalysts will be characterized before and after reaction by complementary techniques to assess the single atom nature of the catalysts and the impact of NOCM chemistry on the catalyst structure.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
|Effective start/end date||8/1/23 → 7/31/25|
- National Science Foundation: $300,000.00
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