Plasma-assisted removal of methanol in N2, dry and humidified air using a dielectric barrier discharge (DBD) reactor

Abstract

In this work, a non-thermal plasma dielectric barrier discharge (DBD) was used to remove methanol from ambient air. The effects of carrier gases (N₂, dry and humidified air), power (2–10 W), inlet concentration (260–350 ppm), and residence time (1.2–3.3 s) were investigated to evaluate the performance of the plasma DBD reactor in terms of removal efficiency, product selectivity and reduction of unwanted by-products at ambient temperature and atmospheric pressure. It was found that the conversion of methanol increased with power and residence time regardless of the carrier gas used. However, the removal efficiency decreased with the increasing concentration of CH₃OH. Almost complete removal of methanol (96.7%) was achieved at 10 W and a residence time of 3.3 s in dry air. The removal efficiency of methanol followed a sequence of dry air > humidified air > N₂ carrier gas. This was due to the action of the O radical in dry air, which dominates the decomposition process of the plasma system. The introduction of water vapour into the DBD system decreased the removal efficiency but had a number of significant advantages: increased CO₂ selectivity and yield of H_2, it significantly reduced the formation of O₃, CO and higher hydrocarbons. These influences are probably due to the presence of potent OH radicals, and the conversion pathways for the various effects are proposed. It is important to note that no solid residue was formed in the DBD reactor in any carrier gas. Overall, this research indicates that methanol can be almost completely removed with the correct operating parameters (96.7% removal; 10 W; 3.3 s) and shows that humidification of the gas stream is beneficial.