Strong mass signals of H2− and D2− ions have been observed from low-pressure dielectric barrier discharge hydrogen and deuterium plasmas via molecular beam mass spectrometry. The observed H2−/H− and D2−/D− ratios (～0.35–0.4) are over five orders of magnitude higher than those observed by other techniques. The kinetic energy of H2− and D2− ions sampled from the plasmas was determined to be widely distributed, from a few eV to >100 eV, giving lifetimes greater than ∼40 μs for H2− and ∼55 μs for D2− . The highest vibrotational excitation of neutral H2 species in the plasma was determined to be about J = 0, v = 5 or J = 19, v = 0 via threshold ionization mass spectrometry. The possible pumping mechanisms for generating H2− with further high J, required by the current high-rotation model, have been proposed. Similar to the lifetime of D2− determined recently by another group, the H2− lifetime observed in this work is about two orders of magnitude longer than that predicted by the current theoretical model. To explain these experimental observations regarding the meta-stability of long-livedH2− andD2− ions, the improved current high-rotation model or other new models, including the possible existence of some long-lived electronically excited states of H2−/D2−, need to be developed.

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.

Investigations on the combination of the dielectric barrier discharge plasma with Co-HZSM-5 catalyst for the selective catalytic reduction (SCR) of NOx by lower hydrocarbons were presented. Compared with the reductant of CH4 and C2H4, C2H2 showed a broader low temperature activity in the SCR of NOx with significant O2 tolerance, as well as enhanced CO2 selectivity under the combination of plasma with the catalyst. With a reactant gas mixture of 500 ppm NOx, 500 ppm C2H2, 15% oxygen in N2 and space velocity of 12000 h-1. The NOx conversion is higher than 50% in the temperature range of 150–450ºC in this plasma-assisted process. Larger than 90% of NOx conversion was obtained at 300ºC and Ein = 138 J l-1. © 2005 Elsevier B. V. All rights reserved.

The oxidative dehydrogenation of ethane to ethylene and acetylene with carbon dioxide at ambient temperature and atmospheric pressure by pulse corona plasma over various catalysts has been investigated. The products included C2H4, C2H2 and syngas (H2 and CO). The conversion of ethane and distribution of products depend on the catalyst used, the C2H6/CO2 feed ratio, the energy density of plasma, etc. The rare earth metal oxides catalyst such as La2O3/γ-Al2O3 and CeO2/γ-Al2O3 enhance the conversion of ethane and the yield of ethylene and acetylene. The sequence of ethane conversion and yield of ethylene and acetylene is from CeO2/γ-Al2O3 to La2O3/γ-Al2O3. The metal catalyst Pd/γ-Al2O3 exhibits high ethylene selectivity. The optimum C2H6/CO2 ratio in the feed for oxidative dehydrogenation of ethane under plasma catalytic conditions is 1/1. The conversion of ethane and the yield of ethylene and acetylene increase with increasing of the energy density of plasma. © 2003 Elsevier B.V. All rights reserved.