Title: Evidences for pore mouth and key-lock catalysis in hydroisomerization of long n-alkanes over 10-ring tubular pore bifunctional zeolites
Authors: Martens, Johan ×
Vanbutsele, Gina
Jacobs, Pierre
Denayer, J
Ocakoglu, R
Baron, G
Arroyo, JAM
Thybaut, J
Marin, GB #
Issue Date: 2001
Series Title: Catalysis today vol:65 issue:2-4 pages:111-116
Conference: date:Katholieke Univ Leuven, Ctr Oppervlaktechem Katalyse, B-3001 Heverlee, Belgium; Free Univ Brussels, Brussels, Belgium; State Univ Ghent, Petrochem Tech Lab, B-9000 Ghent, Belgium
Abstract: The evidence for the pore mouth catalysis model for n-alkane methylbranching on Pt/H-ZSM-22 hydroisomerization catalyst is reviewed. It is based on adsorption equilibria at catalytic temperatures determined using tracer and perturbation chromatography, reaction product distributions obtained with nC(8)-nC(24) n-alkanes and rival model screening for catalytic conversions. In the Henry regime, methylbranched isomers have lower adsorption entropy and enthalpy compared to n-alkanes explained by the enhanced rotational and translational freedom of methyl and methylene groups positioned outside the pore interacting with the external surface. Adsorption isotherms for isoalkanes are in agreement with dual site adsorption in pore mouths and on external surfaces, respectively. The hydroisomerization can be modeled with a bifunctional reaction scheme and adsorption on the external crystal surfaces and pore mouths. The selectivity for 2-methylbranching reflects the optimum van der Waals interaction of the n-alkane with the zeolite pore and methylbranching in that part of the chain that is located outside the first 10-ring of the zeolite pore to facilitate desorption. Very long n-alkanes (C-12(+)) exhibit key-lock adsorptions and penetrate simultaneously with their two ends into two different pores. Key-lock physisorption leads to branching at more central C atom positions. (C) 2001 Elsevier Science B.V. All rights reserved.
ISSN: 0920-5861
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Centre for Surface Chemistry and Catalysis
× corresponding author
# (joint) last author

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