Dry reforming of methane over a Ni/Al2O3 catalyst in a coaxial dielectric barrier discharge reactor. AbstractA coaxial double dielectric barrier discharge (DBD) reactor has been developed for plasmacatalytic conversion of CH 4 and CO 2 into syngas and other valuable products. A supported metal catalyst (Ni/Al 2 O 3 ) reduced in a methane discharge is fully packed into the discharge region. The influence of the Ni/Al 2 O 3 catalyst packed into the gas gap on the electrical characteristics of the discharge has been investigated. The introduction of the catalyst pellets leads to a transition in discharge behaviour from a typical filamentary microdischarge to a combination of spatially-limited microdischarges and a predominant surface discharge on the catalyst surface. It is also found that the breakdown voltage of the CH 4 /CO 2 discharge significantly decreases when the reduced catalyst is fully packed in the discharge area.Conductive Ni active sites dispersed on the catalyst surface contribute to the expansion of the discharge and enhancement of charge transfer. In addition, plasma-catalytic dry reforming of CH 4 has been carried out with the reduced Ni/Al 2 O 3 catalyst using a mixing ratio of CH 4 /CO 2 = 1 and a total flow rate of 50 ml min -1 . An increase in H 2 selectivity is observed compared to dry CH 4 reforming with no catalyst, while the H 2 /CO molar ratio greatly increases from 0.84 to 2.53 when the catalyst is present.

Non‐thermal plasma has been investigated for CO2 reforming of CH4 in a coaxial DBD reactor with different reactor packing materials placed into the discharge gap. Both the chemical and physical effects on reaction performance have been examined for the addition of quartz wool, γ‐Al2O3 and zeolite 3A, in order to gain a better understanding of plasma interactions with materials during CH4 reforming reactions. Quartz wool was found to enhance the conversion of CH4 and improve H2 yields as a result of changes in the physical properties of the discharge; electrical measurements showed an increase in the intensity of microdischarge filaments over quartz wool. In the presence of Al2O3 and zeolite 3A, the discharge intensity was reduced and consequently CH4 and CO2 conversions were lower for these materials. However, in the presence of zeolite 3A improved selectivities towards H2 and light hydrocarbons acetylene/ethylene were obtained and formation of liquid hydrocarbons was inhibited due to shape‐selectivity determined by the zeolite pore size.

The influence of adding TiO2 on the electrical and spectroscopic characteristics of a N2 dielectric barrier discharge (DBD) has been investigated in a single-stage plasma-catalysis system. The introduction of the catalyst into the electrode gap leads to a transition in the discharge behaviour. The presence of the TiO2 pellets in the discharge significantly increases the vibrational temperature of N2 in the DBD, which suggests that the interaction of plasma and catalyst has a strong effect on the electron energy distribution function in the discharge with an increase in electron density in the high-energy tail of the distribution function.

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