(570b) Low-Temperature Microwave Plasma Conversion of Methane to Higher Hydrocarbons
AIChE Annual Meeting
Wednesday, October 31, 2018 - 3:48pm to 4:06pm
H Quest has demonstrated feasibility of applying a microwave continuous flow reactor to high-rate conversion of methane to hydrogen, acetylene, and ethylene. In the experimental set-up, the process gas mixture passes through a resonant cavity reactor, where a microwave discharge is created through an energy input of up to 4kW. The discharge creates a plasma environment and ruptures the CâH bond in methane. Resulting methyl, hydrogen, and other radicals participate in the rapid self-catalytic reaction, promoting activation of other methane molecules, as well as serving as precursors to C2+ chemicals, solid carbons, and free hydrogen. A slipstream exhaust gas with a nitrogen trace was analyzed with a 2-channel Inficon MicroGC to determine product distributions and conversion rates.
The product distribution and conversion rates were shown to be highly dependent not only on the energy density and process gas composition, but also on specific reactor configuration and geometry, as well as the gas flow patterns. Results (input energy requirements, methane conversion rates, and product selectivity) from the experimental sweep through process conditions and reactor configurations with and without a downstream catalyst bed will be discussed. A downward trend in energy requirements as methane concentration increased in the process gas mixture indicates a direction for process optimization.
Unlike other thermal decomposition approaches, this process 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 reactorâs 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 â 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.
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 under award DE-SC0017227.