The medium of small pore zeolites exhibits shape - selectivity, which has been exploited commercially in processes such as the catalytic production of p-xylene, the dewaxing of fuel and lube oils, and the absorptive separation of linear paraffins. When the guest molecules are comparable in diameters to the channels, diffusion takes place by configurational diffusion, which is poorly understood. The diffusion of n-paraffins with carbon numbers in the range of 30-100 is important in the lube and fuel oil dewaxing process to lower pour point for cold weather uses. This project proposes an associated theoretical and experimental program to study the conformation of n-paraffin chains and their creeping diffusion in zeolite channels. The experiment concerns the diffusivity and cracking rates of n-5. The experiments will be compared with a new theoretical approach, "reptation theory" recommended by de Genne for diffusion in polymer melts. The theoretical program (supported elsewhere) studies the conformation of paraffin chains by Monte Carlo methods, the energy changes associated with the creeping motion of chains and the temperature effects, and to proposes diffusion models that may be termed the "Snake-in-Maze" model.
