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Shape Selectivity in Adsorption of n ‐ and Iso‐alkanes on a Zeotile‐2 Microporous/Mesoporous Hybrid and Mesoporous MCM‐48
Author(s) -
Devriese L. I.,
Cools L.,
Aerts A.,
Martens J. A.,
Baron G. V.,
Denayer J. F. M.
Publication year - 2007
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200700008
Subject(s) - microporous material , mesoporous material , adsorption , materials science , selectivity , enthalpy , chemical engineering , steric effects , mesoporous organosilica , organic chemistry , mesoporous silica , thermodynamics , chemistry , catalysis , composite material , physics , engineering
The adsorption of linear and branched C5–C9 alkanes in the temperature range 50–250 °C on mesoporous MCM‐48 material and its microporous/mesoporous variant Zeotile‐2 at low surface coverage is investigated using the pulse chromatographic technique. On MCM‐48, the differences in adsorption between linear and branched alkanes are merely a result of differences in volatility, indicating that the MCM‐48 material does not present shape‐selective adsorption sites. On Zeotile‐2, there is a preferential adsorption of linear over branched alkanes. The difference arises from a difference in adsorption entropy rather than enthalpy. Upon their adsorption on Zeotile‐2 branched alkanes lose relatively more entropy than their linear isomers do. Zeolitic molecular pockets embedded in the walls of the mesoporous Zeotile‐2 impose steric constraints on the bulky isoalkanes. Zeotile‐2 combines adsorption properties from microporous and mesoporous materials. Compared to the nitrogen molecule, linear and branched C5–C9 alkanes are superior probes for investigating micropores and micropockets in hierarchical materials.