Monte Carlo Simulations of Adsorption of Non-polar and Polar Molecules in Zeolite X

Abstract

Grand canonical Monte Carlo simulations have been performed for single-gas adsorption of Lennard-Jones molecules with point multipole moments in zeolite cavities of type X. Fluid-solid electrostatic interactions are taken into account. Adsorption isotherms, isosteric heats and structural properties have been calculated for Xe, CH₄, CO₂, C₂H₄ and i-C₄H₁₀ and compared with experiment. The results reveal the importance of adsorbate-adsorbate interactions for sorption in faujasite. The interaction of the quadrupole moment of CO₂ with the electric field generated by the zeolite ions constitutes more than half of the total energy of adsorption. Density and energy distributions show that the cavity is either a relatively homogeneous surface or a highly heterogeneous one, depending on the molecular characteristics of the adsorbed gas and the type, position and charge of the zeolite cations.

Key Words:

• Zeolites
• adsorption
• Monte Carlo simulation