Humidity Effect on Toluene Decomposition in a Wire-plate Dielectric Barrier Discharge Reactor

Abstract

Laboratory-scale experiments were performed to evaluate the humidity effect on toluene decomposition by using a wire-plate dielectric barrier discharge (DBD) reactor at room temperature and atmospheric pressure. The toluene decomposition efficiency as well as the carbon dioxide selectivity with/without water in a gas stream of N 2 with 5% O 2 was investigated. Under the optimal humidity of 0.2% the characteristics of toluene decomposition in various background gas, including air, N 2 with 500 ppm O 2 , and N 2 with 5% O 2 were observed. In addition, the influence of a catalyst on the decomposition was studied at selected humidities. It was found that the optimum toluene removal efficiency was achieved by the gas stream containing 0.2% H 2 O, since the presence of water enhanced the CO 2 selectivity. In addition, the toluene removal efficiency increased significantly in a dry gas stream but decreased with an increase in the humidity when the Co 3 O 4 /Al 2 O 3 /nickel foam catalyst was introduced into the discharge area.

Plasma‐Based Indoor Air Cleaning Technologies: The State of the Art‐Review

“…According to the reaction constanants, OH radicals play an important role in the destruction of HCHO as compared to ozone. The same study for removal of 50 ppm toluene in a DBD reactor showed that despite the positive role of presence of water molecules in the formation of OH radicals, increasing the relative humidity level (up to 80%) has negative effect on the removal efficiency due to decreasing electron density and quenching the reactive species in the reactor . Therefore, humidity level plays a crucial role on the removal performance of the NTP reactors.…”

“…Relative humidity has an important role in plasma catalyst performance . Yu‐fang et al studied the effect of humidity on toluene decomposition efficiency in a PPC reactor at the ambient temperature. The result of carrying their experiments in the presence of Co 3 O 4 /Al 2 O 3 /nickel foam as catalyst showed the importance role of water molecules in completing the oxidation reactions.…”

“…However, the negative effect of high humidity level is that the catalyst surface is covered with water molecules, which leads to a decrease in the removal efficiency . This negative impact should be taken into account more seriously in the case of indoor environment application in which the concentration of pollutants are in the order of ppb.…”

Methanol oxidation in dry and humid air by dielectric barrier discharge plasma combined with MnO2–CuO based catalysts

“…One way, which has been developed extensively, to overcome these disadvantages is by placing a catalyst inside or post discharge. Depending on the VOC chemical structure, nonthermal plasma reactor layout and catalyst chemical nature, several conclusions were drawn in respect of VOC removal efficiency (RE), ozone concentration, carbon mass balance (CMB), by-products selectivites, specific energy or discharge behavior [4][5][6][7][8][9][10][11][12][13][14]. Treatment by non thermal plasma alone succeeds in removing low concentration pollutants at low energy consumption compared to conventional catalytic processes.…”

“…In a plasma alone configuration, when no catalyst was present in the discharge or post discharge, opposite effects were observed depending on the relative humidity (RH) percentages present in the gas stream [4,7,12,13]. In a low humid environment, the formation of highly oxidative hydroxyl radicals ( • OH) increases due to the dissociation of water molecules by impact with electrons or oxygen radicals, O(1D).…”