Search

[Display omitted] • Stable plasma generation in reactor configuration comprising multiple honeycomb monoliths. • Linear relationship between discharge power and increased number of monoliths. • High ethylene adsorption capacity in an open channeled monolith catalyst at humid conditions. • Higher ethylene removal efficiency with high energy yield at low energy requirement. • Simplified overall system and operation at atmospheric conditions. Dilute ethylene (C 2 H 4) was removed in a novel plasma reactor comprising multiple honeycomb monoliths consisting of up to four PdO/ZSM-5/monolith catalysts. These monoliths were packed in a tubular reactor separated by mesh electrodes alternatively grounded or connected to a high voltage (HV) power source. The effect of the number of monoliths on the discharge power, adsorption, and removal of C 2 H 4 was investigated. Additionally, the influence of the energy input, C 2 H 4 inlet concentration, and gas flow rate on the C 2 H 4 abatement was examined. The adsorption capacity, C 2 H 4 conversion, and energy efficiency were observed to increase as the number of monoliths increased. The effect of the palladium (Pd) loading technique, namely ion exchange (IE), incipient wetness impregnation (IM), and combined IE-IM, IE followed by IM, on the C 2 H 4 adsorption was also studied. The combined IE-IM method presented an exceptional adsorption capacity of ∼136 µmol/g catalyst under humid conditions despite nonpolar nature of C 2 H 4. C 2 H 4 removal was performed via both continuous and cycled storage-discharge (CSD) plasma-catalytic oxidation processes. The CSD process was conducted in two ways: with intermittent C 2 H 4 feed (CSD-IEF) and with maintained C 2 H 4 feed (CSD-MEF), both comprising intermittent plasma discharge. Intriguingly, the performance of the CSD-MEF process was superior (56 J/L, 1.61 g/kWh) to that of the CSD-IEF (119 J/L, 0.98 g/kWh), and continuous process (∼228 J/L, 0.53 g/kWh) in terms of energy efficiency as well as the overall simplicity of the system. [ABSTRACT FROM AUTHOR]

The effect of the reactor configuration and several key parameters such as the gas temperature, humidity, and flow rate on the corona discharge plasma in honeycomb monoliths was investigated. The AC corona discharge-based plasma reactor consisted of two parallel electrodes (perforated disk/wire-mesh) placed at both ends of the honeycomb monolith. Although the wire-mesh electrode offers increased sharpness, the perforated disk electrode, where the corona discharge started at the sharp edges of the holes, produced more discharge power because of the larger effective electrode area. Loading a small amount of metal onto the monolith was found to increase the discharge power significantly. Coating the monolith with a zeolite such as ZSM-5 (Si/Al: 23.9) led to a decrease in the discharge power because of its hydrophobic nature and large surface area. The result also revealed that the operating temperature, the humidity of the feed gas, and the gas velocity were key factors affecting the discharge performance. The discharge power was inversely proportional to the temperature. On the other hand, the use of a high-velocity feed gas with high water vapor content was found to be particularly advantageous for obtaining high discharge power. ga1 • A honeycomb plasma reactor for practical-environmental applications. • Successful generation of large-volume air plasma in commercial monoliths. • Enhancing discharge power by metal-coating over commercial monolith. • Increase in discharge power with increasing either air flow rate or humidity. [ABSTRACT FROM AUTHOR]

[Display omitted] • In-plasma is superior to injected-plasma catalysis for NO x removal at low temperatures. • Significant synergy between plasma and catalyst for NO x removal at low temperatures. • NO x removal efficiency up to 70% by assisting plasma at [200–250 °C] temperature. • Energy delivery through plasma is better than a thermal process for NO x removal. • Injected-plasma catalysis has potential applications in circumstantial high-throughput gas. Plasma-assisted hydrocarbon selective catalytic reduction (HC-SCR) of NO x was investigated by a packed Ag/γ-Al 2 O 3 catalyst in a dielectric barrier discharge reactor at low temperatures. The effect of plasma discharge on NO x removal was investigated with two methods for comparison, in- and injected-plasma catalysis systems. In-plasma catalysis comprised a plasma-catalytic discharge with the entire feed gas, and injected-plasma catalysis incorporated a part of feed gas consisting of dodecane pretreated with the plasma-catalytic discharge and mixed with the remaining gas before passing through the catalyst-alone stage. Here, using the surface response method with temperature and specific energy input (SEI) as independent variables, the results revealed that energy delivery through plasma gained more NO x removal efficiency than that by thermal catalyst process; a set of SEI and temperature is needed to obtain a similar level of NO x removal. There is a significant synergy between plasma and catalyst in in-plasma catalysis at low temperatures (≤250 °C) that increased NO x removal efficiency up to Δη = 50% (SEI = 137 J/L; T = 200 °C). In-plasma catalysis is superior to injected-plasma catalysis for enhancing the NO x removal and widening the temperature window of effective NO x removal owing to the plasma-catalytic interface in-plasma catalysis supplies. Interestingly, the results also revealed that the plasma in the catalyst for both methods did not always improve the NO x removal efficiency. The plasma had a negative effect on NO x removal at sufficient temperature and SEI. As a result, the in-plasma catalysis presented a high NO x removal efficiency; it can be higher than 70% at temperatures of 200–250 °C. However, injected-plasma catalysis has potential applications in circumstantial high-throughput gas due to low plasma energy consumption by adjusting the entire feed to plasma-treated gas ratio. [ABSTRACT FROM AUTHOR]