Deposition of Catalysts onto Vehicle Heat Exchangers via Thermal and Kinetic Spray Processes for Direct Ozone Reduction 2003-01-3079

The California Air Resources Board (CARB) has recently adopted direct ozone reduction (DOR) technologies as an emission control alternative. The application of DOR technologies on motor vehicles allows an automaker to receive non-methane organic gas (NMOG) emission credits, which may be applied to offset vehicle tailpipe emissions or evaporative emissions from fuel tanks. Additionally, DOR technologies can enhance the “green image” of an automaker. DOR devices involve catalyst coatings on radiators or other surfaces in such a way that the amount of ozone in the ambient air passing through such surfaces is reduced. The deposition of catalysts onto substrates (e.g. radiator surfaces) is traditionally accomplished using a slurry process, which often involves multiple steps in coating formation. In this work, deposition of catalytic coatings onto radiator surfaces via kinetic and thermal spray processes is explored. We demonstrate that catalytic materials could be successfully deposited directly onto radiator surfaces using a thermal spray process. Coating characterization studies show that the composition of catalytically active coating surfaces is MnO_x (x between 1.5 to 2) when metal Mn powders are used as a feedstock. Our results show that ozone removal by the thermally sprayed Mn-based catalysts on radiators is efficient (about 70-80% at the radiator's fully warmed-up temperature of about 82 °C) and is comparable to or better than commercially available sample catalysts prepared using slurry-based deposition techniques. The thermal spray process is relatively rapid, involves only a single step in coating formation, and potentially is a low cost alternative to the current slurry technology.