ADSORPTION AND TRANSPORT OF ETHANE AND ETHENE IN ZEOLITE NAA : 2H NMR AND MONTE CARLO LATTICE DYNAMICS STUDIES

The temperature dependence of deuterium NMR spin−lattice and spin−spin relaxation time data for ethane and ethene adsorbed in zeolite NaA is presented for sorbate loadings in the range 1−4 molecules/cavity. Analytical expressions relating these data to the dynamics of the sorbate molecules are derived. Simultaneous fitting of the temperature dependence of both T1 and T2 data for each sorbate loading provides estimates of the correlation time characterizing translational, rotational, and librational motions of the sorbate within the zeolite. The NMR data presented are consistent with ethane having a higher mobility than ethene within the zeolite. Data derived from the NMR study are then used as input to a Monte Carlo lattice dynamics (MCLD) model, which predicts adsorption and transport characteristics of the sorbate−zeolite system. Desorption events from adsorption sites are characterized by a correlation time of the form τ = τo exp[E/(RT)], and the probability of the sorbate attempting an intercage jump ...