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

TLDR

The study develops a coaxial DBD reactor for plasma‑catalytic conversion of CH₄ and CO₂ into syngas and investigates how packing Ni/Al₂O₃ catalyst in the gas gap affects the discharge’s electrical characteristics. The reactor contains a fully packed, methane‑reduced Ni/Al₂O₃ catalyst in the discharge region, and plasma‑catalytic dry reforming of CH₄/CO₂ (1:1 ratio, 50 mL min⁻¹) is performed. Introducing the catalyst pellets transforms the discharge from filamentary microdischarges to a mix of spatially limited microdischarges and a dominant surface discharge, lowers the breakdown voltage, expands the discharge via conductive Ni sites, and boosts H₂ selectivity and the H₂/CO ratio from 0.84 to 2.53.

Abstract

A coaxial double dielectric barrier discharge (DBD) reactor is developed for plasma-catalytic 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 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 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 is 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 with dry CH 4 reforming with no catalyst, while the H 2 /CO molar ratio significantly increases from 0.84 to 2.53 when the catalyst is present.