Ethane is selectively adsorbed over ethylene in their mixtures on the zeolite imidazolate framework ZIF-7. In packed columns, this results in the direct production of pure ethylene. This gas-phase separation is attributed to a gate-opening effect in which specific threshold pressures control the uptake and release of individual molecules. These threshold pressures differ for the different molecules, leaving a window of selective uptake operation. This phenomenon makes ZIF-7 a perfect candidate for the separation of olefins from paraffins, since in contrast to most microporous materials, the paraffin is selectively adsorbed. Mixture adsorption, as studied by breakthrough experiments, demonstrates that gate-opening effects can be effectively used to separate molecules of very similar size.

C2 and C3 alkanes are selectively adsorbed from mixtures over the corresponding alkenes on the zeolite imidazolate framework ZIF-7 through a gate-opening mechanism. As a result, the direct production of the pure alkene upon adsorption and the pure alkane upon desorption in packed columns is possible. Herein, a detailed investigation of the step-wise adsorption and separation of alkanes and alkenes is presented, together with a rigorous performance assessment. A molecular picture of the gate-opening mechanism underlying the unprecedented selectivity towards alkane adsorption is proposed based on DFT calculations and a thermodynamic analysis of the adsorption-desorption isotherms.

High-silica (gel Si/Al ¼ 100) SSZ-13 membranes were prepared by hydrothermal secondary growth on the surface of a-alumina hollow fiber supports. The membranes were evaluated for their performance in the separation of CO 2 from equimolar mixtures with CH 4 or N 2 . The maximum CO 2 -CH 4 and CO 2 -N 2 separation selectivities were found to be 42 and 12 respectively, with a high CO 2 permeance of 3.0 Â 10 À7 mol m 2 s À1 Pa À1 at 293 K and total feed pressure of 0.6 MPa. At the low aluminum content, the prepared membranes contain a very low number of defects, as follows from their H 2 /SF 6 ideal selectivity of over 500 in the 293-473 K temperature range. Due to their hydrophobicity, water in the feed mixture has only a small influence on the permeance at temperatures above 353 K. Water improves the CO 2 -N 2 and CO 2 -CH 4 selectivity, which is attributed to preferential blocking of the hydrophilic, non-zeolitic defect pores. The hydrothermal stability of the high-silica SSZ-13 membrane was evaluated by a long (220 h) CO 2 -N 2 separation test with a humidified (9.5 kPa H 2 O) feed mixture at 393 K and 0.6 MPa feed pressure. The permeance and selectivity were stable during this endurance test, underpinning the promise of high-silica SSZ-13 membranes for application in the separation of hot and humid gas mixtures. † Electronic supplementary information (ESI) available: Including schemes of experimental setup and membrane module, SEM images of support surface and seed layer, details of adsorption simulations, TGA analysis of detemplation process, mixture separation in pressure gradient mode, water and gas adsorption isotherms, analysis of defect inuence. See

The effect of physicochemical properties on catalyst deactivation, overall olefin selectivity and ethylene/propylene ratio during the methanol-to-olefins (MTO) reaction is presented for two zeolites with the DDR topology, Sigma-1 and ZSM-58.