Journal
CHEMICAL ENGINEERING SCIENCE
Volume 87, Issue -, Pages 224-233Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ces.2012.10.010
Keywords
Catalysis; Diffusion; Transient response; Catalyst support; Flux response; Monolith
Categories
Funding
- EPSRC, under the CARMAC project
- EPSRC, under CASTech project
- EPSRC, under FRT project
- DEL NI
- EPSRC [EP/G012156/1] Funding Source: UKRI
- Engineering and Physical Sciences Research Council [EP/G012156/1] Funding Source: researchfish
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The importance of accurately measuring gas diffusivity in porous materials has led to a number of methods being developed. In this study the Temporal Analysis of Products (TAP) reactor and Flux Response Technology (FRT) have been used to examine the diffusivity in the washcoat supported on cordierite monoliths. Herein, the molecular diffusion of propane within four monoliths with differently prepared alumina/CeZrOx washcoats was investigated as a function of temperature. Moment-based analysis of the observed TAP responses led to the calculation of the apparent intermediate gas constant, K-p, that characterises adsorption into the mesoporous network and apparent time delay, tau(app), that characterises residence time in the mesoporous network. Additionally, FRT has been successfully adapted as an extensive in situ perturbation technique in measuring intraphase diffusion coefficients in the washcoats of the same four monolith samples. The diffusion coefficients obtained by moment-based analysis of TAP responses are larger than the coefficients determined by zero length column (ZLC) analysis of flux response profiles with measured values of the same monolith samples between 20 and 100 degrees C ranging from 2-5 x 10(-9) m(2) s(-1) to 4-8 x 10(-10) m(2) s(-1), respectively. The TAP and FRT data, therefore, provide a range of the lower and upper limits of diffusivity, respectively. The reported activation energies and diffusivities clearly correlate with the difference in the washcoat structure of different monolith samples. (C) 2012 Elsevier Ltd. All rights reserved.
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