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Research has focused on dry reforming because it offers a sink for CO2 and relative to steam methane reforming produces a more desirable ratio of H2 to CO for feed to a Fischer−Tropsch synthesis process. To form synthesis gas by dry reforming in a rapid, environmentally benign manner, a fluid-wall aerosol flow reactor powered by concentrated sunlight has been designed. Operating with residence times on the order of 10 ms and temperatures of approximately 2000 K, CH4 and CO2 conversions of 70% and 65%, respectively, have been achieved in the absence of any added catalysts. Methane to carbon dioxide feed ratios greater than unity were fed in order to prevent reaction of CO2 with the graphite tube. The carbon black particles formed by reaction were amorphous carbon black with a primary particle size of approximately 20−40 nm.

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A graphite fluid-wall aerosol flow reactor heated with concentrated sunlight has been developed over the past five years for the solar-thermal decarbonization of methane. The fluid-wall is provided by an inert or compatible gas that prevents contact of reactants and products of reaction with a graphite reaction tube. The reactor provides for a low thermal mass that is compatible with intermittent sunlight and the graphite construction allows rapid heating/cooling rates and ultrahigh temperatures. The decarbonization of methane has been demonstrated at over 90% for residence times on the order of 10 milliseconds at a reactor wall temperature near 2000 K. The carbon black resulting from the dissociation of methane is nanosized, amorphous, and ash-free and can be used for industrial rubber production. The hydrogen can be supplied to a pipeline and used for chemical processing or to supply fuel cell vehicles.

A solar-thermal aerosol flow reactor has been constructed, installed, and tested with the High-Flux Solar Furnace (HFSF) at the National Renewable Energy Laboratory (NREL). Experiments were successfully carried out for the dissociation of methane to produce hydrogen and carbon black and for the dry reforming of methane with carbon dioxide to form syngas (hydrogen and carbon monoxide). Approximately 90% dissociation of methane was achieved in a 25-mm diameter quartz reaction tube illuminated with a solar flux of 2400 kW/m2 (or suns). The carbon black produced was amorphous and had a particle size of 20 to 40 nm. Approximately 70% conversion was achieved for dry reforming using a solar flux of 2000 kW/m2. The experimental results for both processes are very encouraging and support further work to address the technical issues and to develop the processes.