Hybrid plasma-catalytic systems for converting substances of high stability, greenhouse gases and VOC

Abstract

Three kinds of plasma-catalytic hybrid systems were examined with purpose of improving the techniques for the reduction of greenhouse gases and volatile organic compound (VOC) emissions: (1) A new reactor was developed and used for combining the reagent activation in gliding discharges (GD) with the catalytic action of particles moving in the discharge zone. Non-oxidative methane coupling by plasma action in the presence of a moving bed of Pt and Pd catalysts was examined. Acetylene and soot were the main products formed in the homogeneous plasma system (without a catalyst) and with alumina-ceramic particles. In the presence of Pt and Pd supported on alumina ceramic particles, two effects were noticed: ethylene and ethane became the main products instead of acetylene, and the soot formation was strongly reduced. (2) Plasma-catalytic methane conversion with CO 2 was studied in a dielectric-barrier discharge (DBD) reactor which was packed with selected materials: alumina ceramic carrier, Ag, Fe, and Pd catalysts, and Na-ZSM-5 zeolite. It was found that the tested catalysts were active under the process conditions. The catalytic action of palladium was the most pronounced. (3) The conversion of trichloromethane in mixtures with air was investigated with the use of a hybrid system composed of GD and a stable bed of catalysts containing Cr 2O 3, MnO 2 and platinum. Chlorine was the main reaction product with a minor share of hydrogen chloride and tetrachloromethane. Due to the catalysts used in this experiment, the overall CHCl 3 conversion was increased, whereas the unwanted CCl 4 formation was nearly constant. On the basis of these experiments, one can conclude that hybrid systems which combine plasma activation of reagents with the action of solid catalysts may be useful for processing gaseous substances, including those of high stability. It was confirmed that the catalyst localization inside or near the plasma zone is the indispensable condition for high efficiency of the hybrid systems.