Study of catalytic filters for soot particulate removal from exhaust gases

The catalytic combustion of Diesel soot was studied by performing reactivity tests of soot-catalyst mixtures in a tubular flow reactor. Relevant kinetic parameters were derived. With respect to the uncatalysed combustion the reactivity of the soot in the presence of catalyst increased by some orders of magnitude while the apparent activation energy was found to be less than half. Four reactivity tests were also carried out directly at the exhaust of a Diesel engine for studying the capability of regeneration of a ceramic foam filter by catalytic combustion of the accumulated soot. With respect to the uncatalytic case, the presence of the catalyst reduces the carbon ignition temperature so allowing spontaneous regeneration of the filter at operating conditions typical of a Diesel exhaust. A simple descriptive model of filter operation is presented and comparisons between model features and experimental findings are performed.