Effects of particle size on CO2 reduction and discharge characteristics in a packed bed plasma reactor

Current understanding of the behaviour of plasma discharges within packed bed reactors (PBRs) is very poor, and the effects of many of the parameters that can be varied are still unknown. This article investigates the effects of particle size (180 μm to 2000 μm) of two different commonly used packing materials (Al2O3 and BaTiO3) on the conversion of CO2 in PBRs. The reactor behaviour is observed through determination of product gas composition and plasma power consumption in order to determine CO2 conversion and reactor efficiency. Electrical characterisation techniques are used to determine reactor burning voltage, and capacitances. These capacitances are subsequently used to quantify the occurrence of reactor partial discharging over a range of different operating conditions. The results indicate that smaller particles (down to 180 μm) can significantly increase CO2 conversion by up to 70%, provided that the voltage applied is sufficiently high to generate a discharge in the void spaces of the packing material. However, with decreasing particle size, the reactor burning voltage is found to increase rapidly, as well as the tendency of the reactor towards partial discharging

Role of surface discharges in catalytic ozone synthesis

New data are reported on the catalytic activity of silica in the ozone formation under silent discharge conditions. For the first time, the stable catalytic effect was observed not only during the ozone production from oxygen but also-from air. A hypothetical scheme of the catalytic ozone synthesis in the presence of granular dielectrics is discussed. Using a simplified model of the discharge gap, a hypothesis has been proposed on the essential role of surface discharges (on the dielectric grains) in the catalytic process

Deposition of thin SiO_x films by direct precursor in atmospheric pressure microwave torch (TIA)

International audienceAn axial injection torch (TIA, Torche a` Injection Axiale) contained in an open air deposition chamber has been exploited to deposit thin silicon oxide films. The organosilicon precursor, tetramethylsilane (TMS), was injected directly in the plasma gas. A parametric study was carried out to study the effects of microwave power, precursor quantity and torch to substrate distance on the film deposition process. Inorganic films were obtained without the addition of oxygen in the system as the oxygen got incorporated in the plasma from the open air, as shown by optical spectroscopic studies on the plasma. The deposited films were characterised using different techniques like Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), elastic recoil detection analysis (ERDA), Rutherford backscattering spectroscopy (RBS) and nuclear resonance analysis (NRA). These analyses helped understanding the factors affecting the film deposition process. Results show that at short processing time, low microwave plasma power and precursor quantity at an optimised torch to substrate distance, thin non-porous hydrogenated silicon oxide-like films can be deposited at low substrate temperatures of around 370 K using this technique