N2 Adsorption in LiX Zeolite: Isotopic Transient Analysis

Steady-state isotopic transient kinetic analysis (SSITKA) is a very powerful technique used in heterogeneous catalysis to measure coverages and reactivities of surface intermediates. This paper reports the results of a study by SSITKA of N 2 adsorption behavior (physisorption) in a LiX zeolite around room temperature. By varying the partial pressure of N 2 in the feed stream, N 2 adsorption isotherms at temperatures between 303 and 338 K were able to be measured at equilibrium conditions with SSITKA using isotopic switches between 14 N 2 and 15 N 2 . The amount of N 2 adsorbed per total Li cation content varied between (1 and 6.0) × 10 - 2 molecules/cation. The isosteric heats of adsorption of N 2 as a function of coverage were calculated from the measured isotherms using the Clausius−Clapeyron equation. The obtained values (around 5.0 kcal/mol) are in good agreement with ones obtained from data collected using traditional techniques. On the basis of the results of this study, application of SSITKA to the investigation of adsorption from multicomponent sorbing mixtures offers exciting possibilities.