MULTICOMPONENT DIFFUSION OF METHYL ETHYL KETONE AND TOLUENE IN POLYISOBUTYLENE FROM VAPOR SORPTION FTIR-ATR SPECTROSCOPY

In this study, diffusion coefficients of toluene/methyl ethyl ketone ( MEK) mixtures in polyisobutylene were measured at 50 degrees C using v apor sorption FTIR-ATR (Fourier Transform Infrared Attenuated Total Re flectance) spectroscopy. For three mixture compositions, the diffusion coefficients were determined using a diffusion framework for ternary systems. The ''crossterm'' diffusion coefficient for MEK was found to be very small under the experimental conditions studied here, while th at for toluene was found to increase with increasing MEK concentration . On the basis of this finding, a binary diffusion model was used to d etermine diffusion coefficients for MEK over a wide range of mixture c ompositions and the results compared well with those determined from p ure MEK transport data. Relative transport rates during integral sorpt ion experiments with mixtures were used to explain the results. (C) 19 98 John Wiley & Sons, Inc.