Characterization of Nanographene Product by Microwave-Assisted Plasma-Mediated Methane Pyrolysis

R.L. Vander Wal, M. Singh, K. Zeller, G. Skoptsov
Penn State University,
United States

Keywords: microwave, hydrogen, premium carbons, graphene, natural gas, GTL


Hydrogen is recognized as the most promising and environmentally benign energy carrier. In particular, it may be used as a transportation fuel with no pollution and with higher efficiency than the present fossil-based solutions. The current methods of producing hydrogen include steam methane reforming (SMR), coal gasification, water electrolysis, biomass gasification and thermochemical processes. Presently, 95% of industrial hydrogen is produced via steam-reforming of natural gas [1]. This process is burdened with high CO2 emissions and water consumption [2], and does not scale down to enable low-cost, distributed hydrogen production necessary for the hydrogen economy. The heavy environmental burden of this dominant process puts the two objectives of reducing carbon emissions and increasing the use of hydrogen for fuel in direct conflict. H Quest’s microwave plasma pyrolysis process presents a transformational solution to the challenge of efficient, clean, and cost-effective methane decomposition. Unlike other approaches, it does not rely on conventional (contact, convective, or dielectric) heating or use of thermal plasmas. Rather, it employs a microwave resonant cavity to create localized and high-energy reaction zones in the gas as it passes through the reactor’s active zone. Microwaves enable volumetric, non-contact energy transfer to the reactant flow, which is not achievable with radiative or conductive heating in furnaces, by accelerating free electrons in the partially ionized low-temperature plasma. Through electron-molecule collisions, these electrons both transfer the microwave energy to methane molecules and help overcome the high activation energy required by the rate limiting step of hydrocarbon (methane) pyrolysis – the endothermic cleavage of C-C and/or C-H bonds. This results in rapid, direct conversion of methane to chemically active species under atmospheric pressure and mild bulk temperatures: at least 500 ℃ lower than conventional decomposition methods. Additional microwave plasma process advantages include: rapid startup and shutdown, enabling use of intermittent renewable power sources; inherent modularity, scalability, and reduction of costs and risks through replication of a single high-throughput low-cost modular unit reactor; a higher level of safety thanks to lower temperatures and ambient pressures; and simplicity of power delivery [3]. With its prototype microwave plasma reactor, H Quest has demonstrated direct conversion of methane to hydrogen, higher-value chemicals (including acetylene and ethylene), and carbon products: conductive carbon black and a wide range of carbon/graphitic morphologies and nanostructures, including graphene. Presently natural gas can be used in single-stage reactor as a hydrogen source, eliminating external hydrogen production units and the associated CO2 production, water consumption, and capital costs, and providing excess hydrogen sufficient for downstream hydro-treating. Acknowledgements H Quest Vanguard, Inc. is a privately held technology company, based in Pittsburgh, Pennsylvania, focused on the development and commercialization of novel hydrocarbon conversion technologies. This material is based on work supported by the Department of Energy, Office of Science through sub-award agreement no. 212392 with H Quest Vanguard, Inc. under the Prime Award DE-SC0018703 Phase I SBIR.