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Zeolite MFI crystal layers were grown on different α-alumina supports. Permeation and separation characteristics of selected zeolite MFI composite membranes were measured for the system of butane isomers. Flux, permeation and separation factors were measured as a function of feed pressure, temperature and feeding amount of butane isomers. The experiments, based on Wicke–Kallenbach method, were carried out using steady-state membrane apparatus MEMFIS. The observed fluxes and permeances of n-butane were higher in comparison with isobutane for all membranes. The separation factors exhibited the maxima in the dependence on temperature and decreased with increasing feed pressure. It follows from the comparison of single component and binary mixture experimental data that n-butane permeance was strongly reduced by the presence of isobutane as a co-permeating component in the binary mixture. However, isobutane was practically not influenced by the presence of n-butane. Long-term continuous membrane separation resulted in gradual decrease of butane isomers flux and corresponding separation factor. The flux decrease was more pronounced for isobutane. Reactivation of the membranes showed a slight increase of butane isomers flux but continuous decrease of separation factor.

The good quality zeolite MFI membranes were synthesised and studied for the separation of butane isomers. The membranes were effective to separate butane isomers at low feed pressure and in the temperature range between 60°C and 90°C. The longterm permeation experiments showed continuous decrease of flux and separation factor showing the necessity of periodical membrane reactivation. Acknowledgments The financial support by the Czech Science Foundation via grant no. 203/07/1443, the Grant Agency of ASCR via grant KAN 400720701 and ASCR via grant 1QS401250509 is gratefully acknowledged.