Diesel Oxidation Catalyst Combined to Non-Thermal Plasma: Effect on Activation Catalyst Temperature and by-products formation

The aim of this work is to study the pollutants removal efficiency together with the catalyst activation temperature when a Diesel Oxidation Catalyst (DOC) is placed downstream to a multi-plans Dielectric Barrier Discharge (DBD) reactor. In order to simulate Diesel engine exhaust, synthetic gas mixtures containing N2, O2, H2O, CO2, CO, NO, and hydrocarbons (HCs) at controlled concentrations could be heated at temperature up to 300°C. Catalytic material based on Pd and Pt supported on Al2O3 was used at a gas hourly space velocities (GHSV) of about 55 000 h -1 . The major gaseous components as NOx, CO, CO2, and HCs were systematically investigated online and quantified using an electrochemical analyzer and a Fourier Transform Infrared Absorption Spectroscopy (FTIR). Results show the advantageous plasma catalyst coupling effect on the lowering of the catalyst activation temperature. Improvement of about 20°C was obtained. As it is well known, the gas-phase chemistry in the plasma includes NO to NO2 conversion as well as HCs partial oxidation to CxHyOz. These species play an important role in the catalytic mechanisms. Byproducts such as aldehydes (CH2O) and alcohols (CH3OH) compounds were also detected together with a small amount of nitrous acid (HONO) when water was added into the gas mixture.