V. Palma, P. Russo, S. Vaccaro

The catalytic combustion of Diesel soot was studied performing reactivity tests of soot-catalyst mixtures in a tubular flow reactor. The dependence of the reaction rate on the temperature was found. With respect to the uncatalysed combustion the reactivity of the soot in the presence of catalyst increased of some orders of magnitude while the apparent activation energy was found to be less than half. 

Complementary tests were carried out for studying the regeneration process of ceramic sintered filter samples by uncatalysed and catalysed combustion of the accumulated carbon particles. With respect to the uncatalysed case, the presence of catalyst reduces the carbon ignition temperature so favouring spontaneous filter regeneration. However, the catalyst activity appears to be lower than that observed in the reactivity tests. 

The results of both series of tests were discussed and compared in order to assess the role of carbon-catalyst contact and of catalyst preparation on its performances. 

Soot emitted from Diesel engines is hazardous for human health since it is made of inhalable particles [1] and contains gases and liquids adsorbed on its smrface, some of which (Polycyclic Aromatic Hydrocarbons) are suspected to be cancerogenic [2]. Virtually, soot-free Diesel exhaust may be obtained combining reduction of soot formation in the combustion chamber with exhaust gas treatment [3]. This latter is generally performed by a ceramic wall-flow filter that collects the carbonaceous particles while the filter regeneration is achieved by post-combustion of collected soot [3, 4]. 

An important step of the above mentioned soot removal process is the filter regeneration that could lead to filter failvu e by melting or breaking when high temperature spots or large temperature gradients occur [5, 6]. These phenomena 

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P.Ciambelli, V.Palma, P.Russo, S.Vaccaro, Appl.Catal. B Environmental 22(1999)5. 

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