Analysis of hydrogen purification process by adsorption in the dehydrated Na-LSX zeolite is described. New measurements of hydrogen and nitrogen adsorption selectivity of this zeolite have been performed up to a pressure of 20 MPa and at temperatures of 273, 293 and 313 K, by using a gravimetric-volumetric method. Structural characterizations were realized by helium density displacement, nuclear magnetic resonance, X-ray diffraction and scanning electronic microscopy. Furthermore, Monte Carlo simulations of gas adsorption were performed in a zeolite model of Na-LSX, using pair potentials to represent the interaction between gas molecules and zeolite atoms. Comparison of simulation results and experimental data enabled testing of the validity of such a modeling of the gas-zeolite interaction. (C) 2004 American Institute of Chemical Engineers.