Shape-selective n-alkane hydroconversion at exterior zeolite surfaces

Maesen, Theo L. M. ; Krishna, Rajamani ; Vanbaten, Jasper M. ; Smit, Berend ; Calero, Sofia ; Sanchez, Juan Manuel Castillo (2008) Shape-selective n-alkane hydroconversion at exterior zeolite surfaces Journal of Catalysis, 256 (1). pp. 95-107. ISSN 0021-9517

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Official URL: http://www.sciencedirect.com/science/article/pii/S...

Related URL: http://dx.doi.org/10.1016/j.jcat.2008.03.004

Abstract

A critical review of the adsorption and catalysis of n- and methylalkanes demonstrates that the interior surface of TON- and MTT-type zeolites dominates both adsorption and catalysis, and that the contribution from the exteriorsurface is negligible. For both n- and methylalkane isomers, the experimental Henry constants at the interior TON-type zeolitesurface are more than an order of magnitude greater than those at the exteriorsurface. Molecular simulations on exclusively interior TON-type silica surface reproduce the adsorption isotherms of n- and methylalkane isomers remarkably well and suggest that even an isomer as bulky as 2,3-dimethylpentane could have access to the interior TON-type zeolitesurface. Only the reference state used in solution thermodynamics affords an equitable comparison between internal and external surface thermodynamics. It indicates that methylalkanes adsorb in a structured fashion at the exterior TON-type zeolitesurface when the interior surface is inaccessible. But the entropic penalty for this organized exteriorsurface “pore mouth” or “key-lock” adsorption is high, so that methylalkanes prefer adsorption at the interior surface when it is accessible. We speculate that CHA- and ERI-type sieves exhibit exteriorsurface catalysis in long n-alkane conversion, but the database remains too small to allow investigation of the full potential of shape selectivity in exteriorzeolitesurface catalysis.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Ostwald Coefficient; Adsorption Thermodynamics; Solution Thermodynamics; TON-, MTT-, CHA-, ERI-Type Zeolites; Alkane Hydroconversion; Shape Selectivity; Exterior Zeolite Surface Catalysis
ID Code:94033
Deposited On:25 Jul 2012 07:27
Last Modified:25 Jul 2012 07:27

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