Tortuosity of mesoporous alumina catalyst supports: Influence of the pore network organization

• Published in: Microporous and mesoporous materials Vol. 248; pp. 91 - 98
• Main Authors: Kolitcheff, Svetan, Jolimaitre, Elsa, Hugon, Antoine, Verstraete, Jan, Carrette, Pierre-Louis, Tayakout-Fayolle, Mélaz
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-08-2017; Elsevier
• Subjects: Alumina support; Catalysis; Chemical Sciences; Internal diffusional limitations; Inverse liquid chromatography; Material chemistry; Pore network; Pore size distribution; Tortuosity; Pore network; Internal diffusional limitations; Inverse liquid chromatography; Tortuosity; Pore size distribution; Alumina support
• DOI: 10.1016/j.micromeso.2017.04.010
• EISSN: 1873-3093
• ISSN: 1387-1811

Inverse liquid chromatography experiments were performed on five mesoporous alumina catalyst supports with similar porosity and different pore size distributions. By varying the size of the molecular tracer, it was shown that the diffusion regime in our conditions is molecular diffusion. Hindered diffusion was not observed even for squalane, a C30 molecule. Using the slope of the Van Deemter equation, the tortuosity of each alumina support was determined. The results are in disagreement with literature correlations: although all alumina supports had similar total porosities, the measured tortuosity values are really different and much higher than those predicted by these theoretical models. This discrepancy has been resolved by assuming a two–level pore network organization, whose characteristics can be entirely estimated from a classical nitrogen adsorption isotherm. This simple methodology allows to evaluate the mass transfer in mesoporous alumina supports knowing their textural properties, which is an important issue for the design and optimization of numerous catalytic processes.
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•Diffusion properties of several alumina catalyst supports having the same porosity but different textural properties.•Tortuosities of alumina catalyst supports estimated from Inverse Liquid Chromatography experiments differ.•Different levels of the porous organization in the alumina catalyst support.•Decomposition of BJH pore size distribution in order to obtain porous volumes of hierarchical levels.