Thermogravimetric analysis of soot emitted by a modern diesel engine run on catalyst-doped fuel

Understanding the mechanisms that affect catalytic activity in porous ceramic diesel particulate filters (DPF) at the temperature range 200 to 400°C is important for the successful modeling of the initiation and evolution of catalytic regeneration by use of fuel additives. This refers not only to the dry carbon particulate, but also to the volatile hydrocarbons adsorbed on it. In this paper, a detailed analysis of the hydrocarbon adsorption-desorption and oxidation behavior of diesel particulate emitted by a modern diesel engine and collected on a SiC diesel filter is performed by use of thermogravimetric and differential scanning calorimetry analysis (TGA-DSC). Non-isothermal tests were performed with samples collected directly from a ceramic filter connected to the exhaust system of the diesel engine running under low and medium speed and load operating conditions with and without fuel additive. Fuel additive concentration was varied to investigate its effect on the soot oxidation behavior. Based on the TGA data, the kinetic parameters of the soot oxidation reaction were calculated. The effect of volatile adsorbed hydrocarbons on the soot oxidation reaction was evaluated by comparing the calculated activation energies for samples collected from the center and the periphery of the filter at various exhaust temperatures prevailing at filter loading phase. In particular it was seen that the catalytic activity of the fuel additive is enhanced by the presence of the volatile organic components.

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