Configurational Entropy and Intersection Blocking Effects in Multi- component Systems in MFI-type Zeolites Studied by IR Microscopy

1. Introduction Diffusion is important in many technological processes, particularly those that utilize nanoporous materials like zeolites for adsorptive separations and catalysis, where mass transfer is often the rate-limiting step. For understanding and predicting such processes knowledge of the adsorption and diffusion behaviour of molecular mixtures is essential. It is known, that branched hydrocarbons like 2-methylpentane favor the intersections of the channels in MFI-type zeolites as adsorption sites and therefore may impede separation processes by " intersection blocking " [1-3]. On the other hand, in molecular simulations " configurational entropy effects " are found predicting that at higher loadings the sorption of linear alkanes is favored above branched alkanes, if molecules with the same C-number are compared. In this study we present a direct experimental evidence of the " configurational entropy effect " in MFI-type zeolites and cross-link the results with the occurrence of " intersection blocking " .