Dry reforming of methane over a Ni/Al2O3 catalyst in a coaxial dielectric barrier discharge reactor

Abstract

A coaxial double dielectric barrier discharge (DBD) reactor is developed for plasma-catalytic conversion of CH₄ and CO₂ into syngas and other valuable products. A supported metal catalyst (Ni/Al₂O₃) reduced in a methane discharge is fully packed into the discharge region. The influence of the Ni/Al₂O₃ catalyst packed into the gas gap on the electrical characteristics of the discharge is 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 CH₄/CO₂ 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 CH₄ is carried out with the reduced Ni/Al₂O₃ catalyst using a mixing ratio of CH₄/CO₂ = 1 and a total flow rate of 50 ml min⁻¹. An increase in H₂ selectivity is observed compared with dry CH₄ reforming with no catalyst, while the H₂/CO molar ratio significantly increases from 0.84 to 2.53 when the catalyst is present.