Preparation and NOx-assisted soot oxidation activity of a CuO–CeO2 mixed oxide catalyst

• A urea-nitrates combustion method is adopted to prepare CuO–CeO2 catalyst.
• The Cu:Ce molar ratio has a great influence to soot oxidation activity.
• NO2 promote the soot oxidation reaction over CuCe catalyst.
• The nitrate species may be one of the intermediates of soot oxidation.
• Kinetic parameters are determined with a differential TG method.

A CuO–CeO2 mixed oxide catalyst is synthesized via the urea-nitrate combustion method. The catalytic activity in the reaction of NOx-assisted soot oxidation is evaluated with a TG/DTG technique. The sample Cu1Ce9 possesses the lowest temperature (Tm=383 °C) of the maximum soot oxidation rate and the largest specific surface area (65.1 m2/g) among the samples examined. The XRD results show that the fluorite-type CeO2 exists in all the samples forming a solid solution with CuO. Crystalline copper oxide phases are not detectable if the Cu/(Cu+Ce) atomic ratio is lower than 0.25. The activity and NOx-TPD results prove that NO2 formed from NO and the nitrate species play crucial roles for soot oxidation in NOx atmosphere. Kinetic parameters, such as the activation energy and reaction order, corresponding to the oxidation of soot are calculated with a differential method.

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