Quasi-elastic neutron scattering was used to study the diffusion of n-pentane and 2-methylbutane in MCM-22 zeolite. Differences in rotational diffusion, between the linear and branched chains, in the super-cages of the zeolite were measured. The smaller radius of gyration of the branched chain, compared to its linear isomer, resulted in a less restricted rotation in the zeolite cages, as shown by molecular dynamics simulations.

A Quasi Elastic Neutron Scattering and Molecular Dynamics Study of the Rotational Diffusion of n- and Iso-Alkanes in the Cages of Zeolite MCM-22. S.Huang, V.Finsy, M.T.F.Telling, G.V.Baron, J.F.M.Denayer: Studies in Surface Science and Catalysis, 2007, 170[A], 882-92