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Prediction of diffusivity and conversion of n-decane and CO in coated Pt/γ-Al2O3 catalyst depending on porous layer morphology

Paper ID Volume ID Publish Year Pages File Format Full-Text
45951 46427 2014 13 PDF Available
Title
Prediction of diffusivity and conversion of n-decane and CO in coated Pt/γ-Al2O3 catalyst depending on porous layer morphology
Abstract

•Diffusion and reaction simulated in 3D reconstructed porous catalyst.•Effective diffusivity predicted for coated layers with various morphology.•Standard, compact and pore-templated Pt/γ-Al2O3 layers tested.•Model validated by decane and CO oxidation experiments.•Contributions of volume and Knudsen diffusion quantified.

The conversion in monolith reactors for automotive exhaust gas aftertreatment can be limited by diffusion in the catalytic layer. This is particularly important for monolith reactors with multiple coated layers. In this paper, we present detailed modeling methodology for prediction of effective diffusivity based on the actual structure of a porous coating (particle and pore size distributions). We demonstrate the approach on diffusion and oxidation of n-decane and CO in Pt/γ-Al2O3 layers typically used in diesel oxidation catalysts. To validate the model predictions experimentally, several layers were coated with uniform thickness on flat metal foils, and their macroporous structure was controlled by alumina particle size distribution, pore templates and compaction techniques. A multi-scale modelling approach was then applied to predict effective diffusivity and impact of the internal diffusion limitations on the achieved conversions. Diffusion of CO and n-decane was simulated on a micro-scale together with oxidation reactions in a 3D digitally reconstructed porous layer structure. The results were combined with a macroscopic 1D plug-flow model to calculate the reactor outlet conversions. Good agreement was achieved between the predicted and the measured conversions both for n-decane and CO oxidation. The predicted effective diffusion coefficients Deff through the tested Pt/γ-Al2O3 layers were 1.4, 3.6 and 6.4 × 10−6 m2 s−1 for CO at T = 298 K in compact, standard and macropore-templated sample, respectively. The corresponding diffusivities for n-decane were 0.53, 1.2 and 2.0 × 10−6 m2 s−1, respectively. The model quantified relative contributions of volume and Knudsen diffusion regimes to overall transport as well as temperature dependence of Deff.

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Keywords
Diffusion; Exhaust gas aftertreatment; Diesel oxidation catalyst; CO and n-decane oxidation; Multi-scale modeling
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Prediction of diffusivity and conversion of n-decane and CO in coated Pt/γ-Al2O3 catalyst depending on porous layer morphology
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volumes 150–151, 5 May 2014, Pages 446–458
Authors
, , , , , ,
Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us