Characterization of the diffusion path in micro- and meso-porous materials from ZLC analysis
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Characterization of the diffusion path in micro- and meso-porous materials from ZLC analysis Qinglin Huang · Mladen Ei´c · Huining Xiao · Serge Kaliaguine
Published online: 5 August 2010 © Springer Science+Business Media, LLC 2010
Abstract It has been demonstrated that the main diffusion paths of micro- and meso-porous UL-zeolites could be characterized from the Zero Length Column (ZLC) desorption curves with an appropriate theoretical analysis (Malekian et al., in Ind. Eng. Chem. Res. 46:5067, 2007). The present work extends this method to study the ZLC desorption data of n-heptane/cumene/mesitylene in three mesoporous SBA-15 samples, 1-methylnaphthalene in MCM-48, cumene in SBA-16 and toluene/cumene in a microporous one-dimensional boron SSZ-42. The investigation results revealed that the structure of SBA-15, MCM-48 and SBA-16 behaved approximately as three-dimensional (isotropic) diffusion system, while SSZ-42 behaved as one-dimensional (anisotropic) diffusion systems. The diffusion path did not change within the measured temperature range, and by using different sorbate molecules. This work confirmed that this effective and relatively inexpensive method can be used as an additional tool for the characterization of porous materials. Keywords Micro- and meso-porous material · Diffusion path, ZLC technique
1 Introduction Microporous materials of three-dimensional structure (e.g., zeolites A, X, Y and carbon molecular sieve) or oneQ. Huang · M. Ei´c () · H. Xiao Department of Chemical Engineering, University of New Brunswick, Fredericton, NB, E3B 5A3, Canada e-mail: [email protected] S. Kaliaguine Department of Chemical Engineering, Laval University, Québec, G1K 7P4, Canada
dimensional structure (e.g., AlPO4 -5, SAPO-5, silicalite, mordenite and ZSM-12) are widely used as adsorbents and catalysts in the petrochemical and hydrocarbon processing industry. Investigation of one-dimensional microporous materials as hydrocarbon trapping media for controlling vehicle cold start emission has also been reported (Iliyas et al. 2007; Sarshar et al. 2009). As molecules diffuse in microporous materials, they exhibit the corresponding one-/threedimensional diffusion patterns. Such diffusion patterns have to be properly taken into account in the diffusion model used, to avoid significant errors that can be made in the calculations of diffusion parameters. Since the discovery of ordered mesoporous silicas such as M41-S by Mobil Corporation scientists (Kresge et al. 1992) and SBA-n by Stucky and coworkers (Zhao et al. 1998), mesoporous materials have attracted great research interest in the field of catalysis (Trong-On et al. 2003), separation science (Vinh-Thang et al. 2005a) and drug delivery (Doadrio et al. 2006). Mesoporous materials have regular two-/three-dimensional distribution of mesopores with size ranging from 2 to 30 nm, allowing the penetration of large molecules. They were investigated for the use of light hydrocarbon adsorption separation and volatile organic component removal (Newalkar et al. 2002; Serrano et al. 2004)
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