Experimental study and numerical simulation of hydrogen/isobutane permeation and separation using MFI-zeolite membrane reactor

A composite alumina–MFI-zeolite membrane has been prepared by a pore-plugging method. Transport through this mem-brane is controlled by molecular size and adsorption properties, as expected for a defect-free zeolite composite layer. Single gas transport was studied for hydrogen and isobutane. In the studied temperature range, (323–723 K) for isobutane and (277–723 K) for hydrogen, transports were activated. Isobutane exhibited a flux maximum at 450 K, whereas hydrogen flux declined with temperature. These different permeation behaviors were modeled using Maxwell–Stefan equations taking into account only surface diffusion. Activation energies were obtained from the model by fitting the experimental data. They were calculated to be 31 kJ mol−1 for isobutane and 1.9 kJ mol−1 for hydrogen. The diffusion coefficients calculated at 323 K differed by four orders of magnitude. Separation experiments with a mixture of hydrogen and isobutane in a 293–723 K temperature range were performed. Typical permeation behavior was observed for a mixture of weakly and strongly adsorbed molecules. At room temperature, hydrogen permeation was hindered by stronger adsorbed isobutane molecules in the micropores. H2/i-C4H10 separation experiments showed a separation factor of 25 at 723 K, a typical temperature of the isobutane dehydrogenation in membrane reactors. Résum