Kinetic modelling of Pt and Pt:Pd diesel oxidation catalysts

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.

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“…10, right). This behavior has also been reported by Khosravi [11]. Interestingly, if only C 3 H 6 and CO are present in the feed (Fig.…”

Section: Palladium Catalystsupporting

confidence: 56%

Hysteresis Phenomena on Platinum and Palladium-based Diesel Oxidation Catalysts (DOCs)

Dubbe

Bühner

Eigenberger

et al. 2016

Emiss. Control Sci. Technol.

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“…Morlang et al [15] and Persson et al [25] have found that a Pt:Pd alloy increases the hydrocarbon oxidation rate [14]. Khosravi et al [26] determined global kinetic models for Pt and Pt:Pd diesel oxidation catalysts. Han et al [18] reported that among the three DOCs evaluated, the one with (Pt/Pd) had the best light-off efficiency, followed by (Pt-Pd+ CeO 2 ), and Pt-only, regardless of exhaust mixture.…”

Section: Introductionmentioning

confidence: 99%

Experimental and modeling study of CO and hydrocarbons light-off on various Pt-Pd/γ-Al 2 O 3 diesel oxidation catalysts

Daneshvar

Dadi

Luss

et al. 2017

Chemical Engineering Journal

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“…Abedi et al [4] investigated CO hysteresis behavior in a mixture with C 3 H 6 . Khosravi et al [5] investigated the oxidation of carbon monoxide, nitrogen monoxide and propene and the reduction of nitrogen monoxide by propene over two diesel oxidation catalysts. A more recent study by Raj et al [6] examined steady-state and dynamic hysteresis effects during co-oxidation of CO and C 3 H 6 on Pt/Al 2 O 3 .…”

Section: Introduction and Literature Reviewmentioning

confidence: 99%

Bifurcation features of mixtures containing CO and hydrocarbons in diesel oxidation catalyst

Dadi

Luss

Balakotaiah

2016

Chemical Engineering Journal

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A model of a monolith reactor with radial gradients in the washcoat is used to study the ignition-extinction of pure CO, C 2 H 6 and C 3 H 6 and of their mixtures on a Pt/Al 2 O 3 diesel oxidation catalyst. The ignition temperature of the individual species oxidation increases upon an increase in feed concentration of either CO or C 3 H 6 and decreases upon an increase in feed concentration of C 2 H 6 . This is because CO, C 3 H 6 have negative order kinetics and C 2 H 6 has positive order kinetics. We determine the steady-state hysteresis behavior of conversion versus feed temperature during co-oxidation of CO and hydrocarbons (C 3 H 6 , C 2 H 6 ). A single S-shaped bifurcation diagram of conversion versus inlet temperature is obtained during the co-oxidation of all feed mixtures of CO and C 3 H 6 because the activation energies of CO and C 3 H 6 are close to each other. The presence of CO in the feed inhibits the oxidation of propylene during the cooxidation of CO and C 3 H 6 . In contrast, the ignition temperatures of pure CO and pure C 2 H 6 are much different and CO ignites at a much lower temperature than C 2 H 6 A double-S shaped 2 bifurcation diagram is obtained when hysteresis exists for both CO and C 2 H 6 during the cooxidation. The oxidation of CO present in the feed increases the catalyst temperature and this reduces the C 2 H 6 ignition temperature. The separated ignition is transformed to a simultaneous ignition when the CO concentration in the feed is sufficiently high. We determine the boundary in the parameter space of feed compositions and other operating conditions that separate the simultaneous and separate ignition. The application of this result for the design of DOCs for treating exhaust gases at lower inlet temperatures is discussed.

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Kinetic modelling of Pt and Pt:Pd diesel oxidation catalysts

Cited by 39 publications

References 10 publications

Hysteresis Phenomena on Platinum and Palladium-based Diesel Oxidation Catalysts (DOCs)

Hysteresis Phenomena on Platinum and Palladium-based Diesel Oxidation Catalysts (DOCs)

Experimental and modeling study of CO and hydrocarbons light-off on various Pt-Pd/γ-Al 2 O 3 diesel oxidation catalysts

Bifurcation features of mixtures containing CO and hydrocarbons in diesel oxidation catalyst

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