Micro-kinetics of NO storage and reduction with H2/CO/C3H6 on Pt/BaO/Al2O3 monolith catalysts

Abstract

h i g h l i g h t sMicro-kinetic model for NO x reduction with H 2 , CO, C 3 H 6 is developed. Model includes key intermediates determined in the experiments. Model predicts the steady state conversions for NO, H 2 , CO, C 3 H 6 against temperature. Impact of washcoat diffusion and its effect on kinetic parameters is discussed. g r a p h i c a l a b s t r a c t NO and CO conversion vs inlet CO concentration at 270°C on Pt/Ba/Al 2 O 3 catalyst. a b s t r a c tIsothermal steady state NO x storage and reduction on Pt/BaO/Al 2 O 3 by H 2 /CO/C 3 H 6 reactant mixtures is studied using, 1 + 1 dimensional two-phase model that accounts for washcoat diffusional limitations. It predicts the storage and reduction performance over a wide range of inlet feed concentrations and temperatures. A major limitation of global kinetic models is not being able to predict accurately the performance of the catalyst with changing feed composition. Micro-kinetic models elucidating the role of individual reductants can account for such variations. The temperature dependence of the rate constants has been quantified so that the surface chemistry is consistent with experimental observations. Inclusion of washcoat diffusion enables the model to accurately predict the NO x conversion and zscale-up performance of the catalyst over a wide temperature range. The sensitivity of the estimated kinetic parameters to the effective diffusivities in the washcoat is analyzed. Results indicate that the estimated micro-kinetic parameters are influenced by the washcoat pore structure as well as the properties of the catalytic and storage components.

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

“…Therefore, an obvious extension of the work presented here is to include the species NO and water along with other global reactions among the species. An alternative approach is to replace global kinetic models with micro-kinetic models that include all the species of interest as was done by Kota et al [23] for an analogous problem of the LNT. This extension for DOC will be considered in a future publication.…”

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

“…The kinetic parameters for these late igniting species are sensitive to the values of tortuosity and pore radius. We refer to the work of Kota et al [33] for an investigation of the sensitivity of the kinetic parameters with the effective diffusivity in the washcoat.…”

Investigation of the impact of the configuration of exhaust after-treatment system for diesel engines

“…Simple "global kinetic" mechanisms with semi-empirical reaction rate expressions (based on work of Voltz et al [38] for example) are often used. However they are rarely able to describe the change in catalyst behaviour under different operating conditions where the inlet composition changes significantly [39]. The global kinetic approach is also unable to describe the composition profile of species adsorbed on the catalyst which can have significant impact [40].…”