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.

At atmospheric pressure and room temperature, dielectric barrier discharge induced plasma oxidation for achieving supported TiO2 photocatalysts derived from TiCl4 adsorbed onto γ-Al2O3 pellets was studied. The supported TiO2/γ-Al2O3 photocatalysts prepared by a cyclic ‘adsorption–discharge’ approach, without requirement of heat treatment, exhibit high activity in the photocatalytic degradation reaction of formaldehyde. The mass spectra and optical emission spectra during O2/Ar discharge for oxidizing the adsorbed-state TiCl4 were measured. The mechanism for the TiO2 formation from adsorbed-state TiCl4 by plasma oxidation was discussed.

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.

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.

Methane conversion to C2 hydrocarbons and hydrogen has been investigated in a needle-to-plate reactor by pulsed streamer and pulsed spark discharges and in a wire-to-cylinder dielectric barrier discharge (DBD) reactor by pulsed DC DBD and AC DBD at atmospheric pressure and ambient temperature. In the former two electric discharge processes, acetylene is the dominating C2 products. Pulsed spark discharges gives the highest acetylene yield (54%) and H2 yield (51%) with 69% of methane conversion in a pure methane system and at 10 SCCM of flow rate and 12 Wof discharge power. In the two DBD processes, ethane is the major C2 products and pulsed DC DBD provides the highest ethane yield. Of the four electric discharge techniques, ethylene yield is less than 2%. Energy costs for methane conversion, acetylene or ethane (for DBD processes) formation, and H2 formation increase with methane conversion percentage, and were found to be: in pulsed spark discharges (methane conversion 18–69%), 14–25, 35–65 and 10–17 eV/molecule; in pulsed streamer discharges (methane conversion 19–41%), 17–21, 38–59, and 12–19 eV/molecule; in pulsed DBD (methane conversion 6–13%), 38–57, 137–227 and 47–75 eV/molecule; in AC DBD (methane conversion 5–8%), 116–175, 446–637, and 151–205 eV/molecule, respectively. The immersion of the γ-Al2O3 pellets in the pulsed streamer discharges, or in the pulsed DC DBD, or in the AC DBD has a positive effect on increasing methane conversion and C2 yield. © 2004 Elsevier B.V. All rights reserved.