The diesel oxidation catalyst (DOC) plays a key role in diesel exhaust treatment systems. Typical noble metals used as active components are platinum (Pt) and palladium (Pd). During lightoff/lightout experiments, the catalyst reactivity during heating is in some cases different from the reactivity during cooling in the same reaction mixture. These so called hysteresis phenomena have repeatedly been reported for CO, NO, and HC conversion and are mostly attributed to noble metal oxidation and/or surface coverage effects. Hauff et al. have developed a kinetic model that is able to account for the hysteresis effects observed in NO conversion on Pt-only catalysts due to noble metal oxidation. The model was only validated for a limited range of NO concentrations and temperatures. In this follow-up, further experiments on Pt-only as well as on Pd-only catalysts will be presented for additional feed compositions. General transferability of the Pt-only model to Pd-only catalysts for NO-only is demonstrated. By addition of CO and propene to the feed, additional hysteresis phenomena are observed and will be discussed. On Pd-only, results indicate that under lean exhaust conditions, the noble metal can only be slightly reduced by CO. Interestingly, with a mix of CO and NO no reactivation is observed whereas the combination of CO, NO, and propene again shows reducing tendency. Based on these informations, a possible modeling approach will be proposed.

This work shows that the powder aerosol deposition (PAD) method allows the formation of films in powder quantities of less than 60 mg, rather than the large amounts that are typically required for conventional powder aerosol deposition systems. This was achieved by changing the operation mode to a discontinuous one, resulting in operation times of several seconds. Semiconducting strontium titanate ferrate SrTi0.65Fe0.35O3−δ (STF35) was used as the powder to prove the equal behavior in terms of adhesion, film quality and electric conductivity compared to conventional powder-aerosol-deposited films.

Parameter estimation for Langmuir‐Hinshelwood/Hougen‐Watson type of kinetics in the field of automotive exhaust gas aftertreatment can be challenging as a great variety of parameter sets can result in a similar model quality as rate and inhibition parameters can interact during numerical optimization although they can be regarded independent from theory. This contribution introduces a method that enables the model‐based rapid estimation of NO oxidation kinetic information on a Pt‐only monolith catalyst from a straightforward set of synthesis gas test‐bench experiments.