TRANSPORT OF N-PARAFFINS IN ZEOLITE-T

Mass transport of n-heptane, n-nonane, and n-dodecane in zeolite T was studied using a gravimetric uptake technique. The sigmoidal shape of the uptake curves indicated the existence of a nondiffusional resistan ce in the transport process. To compute the transport parameters, an a pproach based on the temporal moments of the uptake curves was develop ed. A model involving an external resistance dependent on the local sl ope of the sorption isotherm best represented the data. No evidence of the ''window effect'' reported by Gorring was found. The measured dif fusivities decrease with chain length, while the activation energies r emain essentially constant. Both resistances (diffusional and nondiffu sional) depend strongly on lattice loading, and their relative contrib utions for the transport time change as saturation is approached.