Air pollution from mobile sources is an increasingly serious problem throughout most of the industrialized would. Diesel powered vehicles, because of their higher thermal efficiency, tend to emit less carbon monoxide and unburned hydrocarbons than gasoline vehicles, but emit significant quantities of NOx. Therefore, it is essential to develop improved emission control equipment in diesel engines. A fixed bed catalytic reactor was used to study the decomposition of NO and the reduction of NO to N2 by different reductants that can be found in diesel exhaust, such as hydrocarbons, CO and elemental carbon over different catalysts. The effect of space velocity, feed concentrations, reaction temperature and catalyst deactivation were also investigated. A dual detector gas chromatograph equipped with a thermal conductivity and a flame ionization detection, a gas chromatograph with thermal conductivity detector and a chemiluminescent NO/NOx analyzer were used for quantitative analysis of feed and product streams.
The results show that both Cu-ZSM-5 and high surface area alumina are effective in promoting the desired NO reduction reaction, especially the reduction of NO by hydrocarbon. It was also determined that copper loaded carbon and alumina containing copper reduce NOx at lower temperature than these substrates do without copper. The results can be explained qualitatively using the hypothesis that the catalyst promotes the soot-NOx reaction by requiring an intermediate, possibly CO, produced from the soot to react with NO on the catalyst. This hypothesis helps explain how the catalyst improves soot oxidation without invoking the requirement that soot adsorb on catalytic active centers or diffuse into catalyst pores. The CO will rapidly reduce the NO to N2 while being oxidized to CO2. This research is part of an overall project directed at the development of a rotating fluidized bed reactor (RFBR) to catalytically promote the oxidation of diesel soot while reducing NOx to nitrogen gas
