Controlling Al-distribution in small-pore zeolites: Impact on adsorption and cyclic separation

The chemical composition of zeolites, widely used in chemical industry, is known to strongly affect their adsorptive and catalytic properties. Small pore cage-like zeolites have similar dimensions as their guest molecules (< 1 nm). This high degree of confinement leads to remarkable, highly selective molecular separations and unusual adsorption effects ('cage' and 'window' effects, molecular gating). Subtle changes in chemistry, such as Al-distribution, should have a strong impact on the adsorption phenomena for these materials. Recently, some control over the position of the Al within the zeolite structure (Al-distribution such as pairing) has been demonstrated via hydrothermal synthesis. This project will, for the first time, explore the effects of different Al-distributions on unusual adsorption phenomena in small pore zeolites. This study therefore focuses on establishing a wider synthetic control of the Al-distribution (WP I) in confinement-relevant small pore frameworks. The synthesized zeolites will be studied for their adsorption behavior (WP II) and separation behavior (WP III). To study the latter, WP III includes a new cyclic study technique. Here, molecular mixtures are separated in a thermal adsorption-desorption cycle. By systematically adapting the cycle frequency, the goal is to map the separative behavior and effectively search for unusual phenomena over a broad range of conditions.