An experimental study on the conversion of NO in the NO/N2, NO/O2/N2, NO/C2H4/N2 and NO/C2H4/O2/N2 systems has been carried out using dielectric barrier discharge (DBD) plasmas at atmospheric pressure. In the NO/N2 system, NO decomposition to N2 and O2 is the dominating reaction; NO conversion to NO2 is less significant. O2 produced from NO decomposition was detected by an on-line mass spectrometer. With the increase of NO initial concentration, the concentration of O2 produced decreases at 298 K, but slightly increases at 523 K. In the NO/O2/N2 system, NO is mainly oxidized to NO2, but NO conversion becomes very low at 523K and over 1.6% of O2. In the NO/C2H4/N2 system, NO is reduced to N2 with about the same NO conversion as that in the NO/N2 system but without NO2 formation. In the NO/C2H4/O2/N2 system, the oxidation of NO to NO2 is dramatically promoted. At 523 K, with the increase of the energy density, NO conversion increases rapidly first, and then almost stabilizes at 93–91% of NO conversion with 61–55% of NO2 selectivity in the energy density range of 317–550 J L−1. It finally decreases gradually at high energy density. A negligible amount of N2O is formed in the above four systems. Of the four systems studied, NO conversion and NO2 selectivity of the NO/C2H4/O2/N2 system are the highest, and NO/O2/C2H4/N2 system has the lowest electrical energy consumption per NO molecule converted.

A new bimetallic catalyst (Ag–Co/CeO2) was studied for simultaneously catalytic removal of NO and CO in the absence or presence of O2. CeO2 prepared by homogeneous precipitation method was optimized as supports for the active components. The addition of Ag on CeO2 greatly improved the catalytic activities in the lower temperature regions (≤300ºC), and the introduction of Co on CeO2 increased the activities at higher temperatures (≥250ºC). The bimetallic Ag–Co/CeO2 catalyst combined the advantages of the corresponding individual metal supported catalysts and showed superior activity due to the synergetic effect. The effect of support, temperature, loading amount, GHSV and oxygen on catalysis was investigated. NO and CO could be completely removed in the temperature range of 200–600ºC at a very high space velocity of 120 000 h-1. No deactivation was observed over 4% Ag–0.4% Co/CeO2 catalyst even after 50 h test. © 2006 Elsevier B.V. All rights reserved.

Nanocrystalline anatase TiO2 has been successfully synthesized using TiCl4 and O2 as precursors by atmospheric cold plasmas generated by dielectric barrier discharges (DBD) without extra heating or thermal treatment. For the TiO2 powders synthesized by DBD plasma at an energy density of 5.9 k J۰ L-1, XRD and TEM analyses revealed that the nanocrystallite size is about 10–15 nm. Only a single crystalline structure of anatase was observed performing XRD, HRTEM and SAED measurements. It was found that the particle size decreased with increasing the discharge power, and that the chlorine contamination dramatically decreased when using high discharge power levels.

A process for a high yield of aromatics and co-produced hydrogen from the oxygen-free conversion of methane using a two-stage plasma-followed-by-catalyst (PFC) reactor at atmospheric pressure and low temperature is reported. Pure methane and a methane and hydrogen mixture as the feed gas for the two-stage PFC process were investigated, respectively. Using the methane and hydrogen mixture as the feed gas into the two-stage PFC reactor, Ni/HZSM-5 catalysts keep stable catalytic activity for a much longer on-stream time than that using pure methane as the feed gas. The maximum aromatic yield may be achieved using low Ni-loading Ni/HZSM-5 catalysts and at a suitable catalyst temperature.

A supported TiO2/γ-A12O3 photocatalyst has been prepared by γ-Al2O3 pellet-filled dielectric barrier discharges induced plasma CVD at atmospheric pressure and room temperature. The TiO2/γ-A12O3 photocatalyst exhibits higher photocatalytic activity than Degussa P25, and much higher photocatalytic activity than that prepared by thermal CVD.