title: n- and isoalkane adsorption mechanisms on zeolite MCM-22.
abstract: Low-coverage adsorption properties (Henry constants, adsorption enthalpy, and entropy) of linear and branched alkanes (C3-C8) on zeolite MCM-22 were determined using the chromatographic technique at temperatures between 420 and 540 K. It was found that adsorption enthalpy and entropy of linear alkanes vary in a nonmonotonic way with carbon number. The adsorption behavior of alkanes was rationalized on the basis of the pore geometry. Short molecules prefer to reside in the pockets of the MCM-22 supercage, where they maximize energetic interaction with the zeolite. Longer molecules reside in the larger central part of the supercage. For carbon numbers up to six, singly branched alkanes are selectively adsorbed over their linear counterparts. This preference originates from the entropic advantage of singly branched molecules inside MCM-22 supercages, where these species have high rotational freedom because of their small length.
authors.affiliation: Dienst Chemische Ingenieurstechniek, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium. Joeri.Denayer@vub.ac.be
authors.forename: Joeri F M
authors.initials: JF
authors.lastname: Denayer
authors.forename: Refik A
authors.initials: RA
authors.lastname: Ocakoglu
authors.forename: Joris
authors.initials: J
authors.lastname: Thybaut
authors.forename: Guy
authors.initials: G
authors.lastname: Marin
authors.forename: Pierre
authors.initials: P
authors.lastname: Jacobs
authors.forename: Johan
authors.initials: J
authors.lastname: Martens
authors.forename: G V
authors.initials: GV
authors.lastname: Baron
mesh_terms: D000327:Adsorption; D000473:Alkanes / Q000737:chemistry*; D008956:Models, Chemical; D013499:Surface Properties; D013696:Temperature; D017641:Zeolites / Q000737:chemistry*
chemical_list: D000473:Alkanes; D017641:Zeolites