Synthesis of PdO/CeO2 mixed oxides catalyst for automotive exhaust emissions control

PdO/CeO2 mixed oxide catalysts were synthesized using a modified deposition-precipitation technique. The catalyst was quite effective in oxidizing hydrocarbons (HC) and carbon monoxide (CO), but was not efficient in reducing nitrogen oxides (NOx). The light-off temperature for CO and HC under stoichiometric conditions was about 130 degreesC. The presence of CeO2 enhanced the low temperature activity of the catalyst. About 100% CO conversion was achieved at 235 degreesC, whereas the conversion for HC reached 77.8% at 245 degreesC. The promoting effect of CeO2 also improved the catalyst's ability to operate under lean conditions. The catalyst was able to reduce up to 80% of CO at 250 degreesC and 66% of HC at 315 degreesC. The efficiency of the catalyst in reducing NOx was low and the light-off temperature was not reached over the duration of the experiment. The catalyst started to reduce NOx only above 240 degreesC. The highest efficiency of about 27% was achieved at 275 degreesC. (C) 2004 Elsevier B.V. All rights reserved.