Two-step activation of SSZ-13 zeolite membranes for mild template removal and enhanced CO2/C2H6 separation

Abstract

Activation plays a crucial role in determining the final performance of zeolite membranes, and therefore, developing an effective activation technique to achieve both high permeance and high selectivity is highly desirable. In the present study, a promising two-step activation strategy, consisting of a hydrocracking step followed by an oxidation step, has been proposed to fabricate high-performance SSZ-13 zeolite membranes for CO₂/C₂H₆ separation. Compared to the single-step hydrocracking or oxidation activation, the two-step activation strategy enabled much more effective removal of the organic template from the SSZ-13 zeolite channels at a significantly lower temperature, despite identical activation conditions, except for the atmosphere. This led to improved CO₂ permeance and CO₂/C₂H₆ selectivity, owing to the more efficient removal of the template. It was confirmed that C₂H₆ preferentially adsorbs in the SSZ-13 zeolite pores, resulting in reduced CO₂ permeance and CO₂/C₂H₆ selectivity during CO₂/C₂H₆ mixed-gas separation compared to single-gas permeation. Furthermore, the CO₂ permeation mechanism shifted from surface diffusion to activated diffusion due to the narrowing of the zeolite pores after C₂H₆ adsorption. These findings highlight the potential of the proposed two-step activation strategy for developing high-quality zeolite membranes and provide a promising solution for enhancing CO₂/C₂H₆ separation in mixed-gas separations by modifying C₂H₆ adsorption in the zeolite pores.