Systems based on Ce-Zr are used in catalytic converters for their oxygen storage ability. Recently, their application for soot abatement is under investigation. In this paper, preliminary results of the performance of Ce-Zr systems with the addition of K are reported by varying potassium content and calcination temperature. The powder catalysts were prepared by a variant of the citrates route developed at University of L'Aquila. Characterization of the catalysts after calcination was performed by different techniques: profile fitting of the XRD data, estimation of surface composition by XPS, evaluation of catalytic performance by temperature programmed oxidation tests of the soot-catalyst mixture and of redox properties by carbothermic reduction and subsequent oxidation in a high resolution thermobalance. The characterization by XRD showed that the system maintains the crystallographic structure Fm-3m and that the potassium is segregated on the grain boundaries. The catalytic activity results showed that the systems are particularly active even after 10 hours of calcination at 900 degrees C in fluidized bed. This temperature is high enough to get reasonably stable systems for practical applications. Moreover, the soot oxidation rate has a maximum at 368 degrees C in the sample with the best performance, therefore in the range of temperatures of diesel engine exhaust gases. The XPS data showed the presence of Ce, Zr, K and also of significant amount of Cl. Other formulations were prepared by adding small amounts of the different potassium halides.

The application of microwaves allows to overcome technical hitches related to the regeneration of soot-filters allowing to perform it independently on the engine operating conditions. The performance of a SiC foam filter during microwave regeneration was investigated with and without a catalyst coating. The regeneration efficiency and the energy required for regeneration were evaluated for catalytic and uncatalytic SiC foams by varying the operating conditions of soot trapping.Results showed that for both catalytic foams, Fe/V/K and Cu/V/K, the capability to be heated independently of the amount of soot allows to maintain temperature sufficiently high to perform a complete foam filter regeneration. Moreover, the microwave absorbing properties of the catalytic phases allow to perform regeneration with a lower energy consumption with respect to the uncatalytic case. The presence of a catalyst also allows to overcome the dependence of microwave-assisted regeneration process on the operating conditions of soot loading. (c) 2006 Elsevier B.V. All rights reserved.

Recent progress in diesel technology demonstrates the possibility of reducing the particulate matter (PM) emissions level combining the high efficiency of common rail engine with exhaust gas after-treatment devices, such as diesel PM filter. Ceramic foam catalytic filter (CFCF), prepared by coating of ceramic foam (CFUF), results in lower temperature and shorter regeneration time due to the higher specific surface, lower pressure drop and good filtration efficiency with respect to CFUF.

Microwaves heating and catalysis have been proposed as an integrated process to get fast diesel particulate filter regeneration without occurring in filter failure. The choice of the filter composition, catalytic active species and support material is a key parameter for optimal energy handling. In this work the effect of the catalyst support on the activity of Cu/V/K catalyst towards soot oxidation in the presence of microwaves was investigated. Results shown that in the presence of an active catalyst supported on a very good microwave absorbing oxide, the overall soot conversion is achieved in a very short time and with lower energy supply with respect to the uncatalytic case.

Microwave assisted regeneration of catalytic a nd uncatalytic foam used as s oot filter was studied. Results showed that a catalytic foam with microwave absorbing properties allows an energy saving with respect to the uncatalytic one.