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This paper will discuss a number of different matters relating to the regeneration of catalyst coated diesel particulate filters such as: impact of the catalyst on the soot ignition temperature, soot combustion rate and NO2 generation. If catalytic coatings prove to be sufficient compared to certain fuel additives they could be used in second generation diesel particulate aftertreatment systems. Examples will be shown on how catalytic diesel particulate filters (“DPF”) can operate on a common rail passenger car diesel engine. Furthermore, an outlook is given on the future combination of particulate - and NOx - emission control for diesel passenger cars.

Since May 2000, PSA Peugeot Citroën has commercialized a wide range of diesel vehicles of different sizes (Peugeot 807, 607, 406 and 307; Citroën C8 and C5) equipped with a Diesel Particulate Filter (DPF) system using a Ceria-based Fuel-Borne Catalyst (FBC). More than 250000 vehicles have been sold in Europe. Based on extensive in-service feedback, an opportunity to further improve and optimize the technology was identified which will facilitate its extension to smaller passenger vehicles. The use of a more active FBC was identified as one of the key areas for improvement: with increased catalytic activity the FBC dosing rate is reduced and thus the rate of ash-build up in the DPF is limited. This could significantly extend the DPF interval maintenance. A new Ceria-based FBC (Ce-FBC) has been developed which demonstrates enhanced catalytic activity with limited exothermal peaks during DPF regeneration. This property is essential in preventing mechanical failure of the DPF.

A commercial NOx-storage catalyst for gasoline applications containing Ba/CeO2/Al2O3, platinum, palladium and rhodium has been sulfated on the engine bench at 390 and 510°C with a nominal exposure of 1.3 g sulfur/liter catalyst. Lower exposures proved too low to have a notable impact on the catalytic performance. At 390°C the sulfur is completely adsorbed while at 510°C only partial adsorption is being observed. Sulfur is mainly deposited at the catalyst inlet thereby shielding the downstream region. Desulfation on synthetic gas bench at 700°C leads to a partial removal of the sulfur. The residual sulfur is more evenly distributed along the length of the catalyst compared to the sulfur profile in the sulfated catalyst. This causes an improvement of the NOx-activity at the inlet side while the NOx-performance at the outlet side decreases after desulfation.

Comparisons between 1D simulations and experiments on a mini scale SiC filter are presented. First of all, experiments with regeneration for different loading mass and soot composition enabled us to derive an improved pressure drop correlation. The assumption of constant particulate layer permeability proves unable to predict the influence of the gas temperature on the pressure drop. This discrepancy seems to be linked to the high Knudsen number of the flow in the particulate layer. A new correlation is proposed. This correlation contains four adjustable constants which have been determined on a single experimental run. Without modifying these constants, other cases have been correctly simulated. Obviously, more work is needed to substantiate this approach. In a second step, regenerations with and without additive (Cerium) for two different soot compositions have been simulated and compared with experimental results.