Pulsed dry methane reforming in plasma-enhanced catalytic reaction

• Non-thermal plasma and catalyst hybrid reaction enhances CH4 and CO2 conversion with reduced coke deposition.
• Pulsed reforming enables continuous operation without serious coking problem.
• Pulsed CH4 injection produces H2 (higher H2/CO ratio) selectivity.
• Carbon removal reaction (Boudouard reaction) is promoted by non-thermal plasma.
• Optical emission of C2 high pressure Swan system is associated with the solid carbon removal via Boudouard reaction.

Pulsed dry methane reforming (DMR) in dielectric barrier discharge (DBD) and 12 wt.% Ni/Al2O3 catalyst hybrid reaction was investigated, aiming for efficient conversion of greenhouse gas (CH4, CO2) into syngas (H2, CO) at low temperature. CO2 was continuously supplied, while CH4 was introduced intermittently for 1 min at constant interval of 3 min. Although solid carbon was deposited during the reforming reaction, carbon was almost fully removed by turning off CH4 flow and applying CO2-fed DBD. Pulsed transient analysis revealed that CH4 dehydrogenation and subsequent reverse water–gas-shift reaction is sufficiently fast with and without DBD, producing syngas with the H2/CO ratio of 0.8–0.9. In contrast, carbon removal reaction, i.e. Boudouard reaction, is promoted clearly by DBD hybridization. Radical injection is primarily important step. Besides, selective surface heating by DBD such as charge recombination on the catalysts is anticipated to promote carbon diffusion through Ni catalyst particles and subsequent oxidation by adsorbed CO2. DBD and catalyst hybrid reaction enabled higher CH4 and CO2 conversion without having serious coking problem.

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