Synergetic effects of plasma and metal oxide catalysts on diesel soot oxidation

The synergetic effects of a pin-to-plate corona plasma and Mn, Co and Fe oxide catalysts on soot oxidation were investigated under diesel exhaust gas conditions of 10% oxygen and 180-350 degrees C. The catalysts were synthesized by a precipitation method and characterized by XRD, BET surface area, SEM, EDX mapping, and temperature programmed methods of H-2-reduction, O-2-desorption and oxidation. The effects of energy injection, gas temperature, NOx, and water vapor were investigated on the soot removal efficiency in the absence and presence of catalysts. Both tight and in-situ catalyst-soot contacts were examined. NOx as the most hazardous pollutant in the diesel exhaust gas is completely removed in plasma. In the presence of the catalyst, the soot removal efficiency and selectivity to CO2 enhance by up to 77 and 29%, respectively, as compared to those in the plasma alone. The highest removal efficiency and CO2 selectivity are obtained on manganese and iron oxides at high and low temperatures, respectively. 49.3 and 17.4% enhancements of energy efficiency are observed, when 3.5% H2O vapor or 450 ppm NOx is added to the plasma-MnOx catalysis system at 5.7 W and 300 degrees C, respectively. High energy efficiencies at very low energy injections are the advantages of this study. (C) 2015 Elsevier B.V. All rights reserved.