Molecular simulation of adsorption of alkanes in sodium MOR-type zeolites using a new force field

Abstract

The applicability of a recently proposed force field of Calero et al. (J. Am. Chem. Soc., 2004, 126, 11377) to Na–MOR zeolites is evaluated. The Henry law coefficients of ethane and C₅–C₉ as well as the adsorption isotherms of ethane, propane, butane, and hexane in various Na–MOR zeolites are computed and compared with experimental values. These comparisons show that the new force field is suitable for Na–MOR zeolites. Furthermore, this force field is used to study the effects of sodium cations on the adsorption behavior of larger alkanes, such as C₄–C₇, in MOR-type zeolites. These simulations give a better understanding of the underlying mechanisms of the cations’ position and density influence on adsorption. In addition, a characteristic pressure named “reversal pressure” is introduced which characterizes the efficiency of the presence of cations in zeolites.