Structure and physisorption energy of alkanes in ZSM-22 are investigated using periodic density functional theory employing the new BEEF-vdW functional. Good agreement with experimental data is obtained, illustrating successful modeling of the van der Waals forces responsible for the adsorption. All calculations were performed on a single level of theory, and the method therefore provides an attractive possibility for an accurate theoretical description of the confinement effects observed in zeolite catalysis.