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.

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.

A novel process consisting of a pulsed streamer discharge over Ni/HZSM-5 catalysts for an oxygen-free conversion of methane to aromatics is reported here. This plasma-over-catalyst process shows a significant synergetic effect on promoting methane conversion to aromatic products and high stability. Using this process at atmospheric pressure and a temperature of 573 K, significant amounts of aromatics have been obtained.

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.