Dealuminated Cs-ZK-5 zeolite for propylene/propane separation

Abstract

Developing new, more efficient adsorbents for propylene/propane separation is of urgent need, as the current energy-intensive cryogenic distillation method has to be replaced to achieve green chemistry goals. Here, we report that 973 K-steamed cesium ZK-5 zeolite with a framework Si/Al ratio of 16 (Cs-ZK-5-16-973) shows high propylene uptake and propylene/propane selectivity (1.9 mmol g(-1) and 2.4, respectively) at 298 K and atmospheric pressure, together with fast adsorption kinetics, mainly due to its modified 8-ring window dimensions. More interestingly, no significant loss in uptake or selectivity was observed even after repeated adsorption?desorption cycling under vacuum-swing adsorption mode and dynamic breakthrough experiments, which may be a result of the lack of strong acid sites to induce propylene oligomerization at room temperature. This impressive regeneration is comparable with the behavior of the pure-silica small-pore zeolite ITQ-12, but much better than that of Na-A and Ca-A, rendering Cs-ZK-5-16-973 potentially useful for selective propylene/propane separation.