Manipulating pore structures of SSZ-13 zeolite membranes via hydrocracking activation for superior H2/CO2 separation

Abstract

Manipulating pore structures with precisely controlled pore sizes and surface chemistry is essential for fabricating high-quality zeolite membranes. This study aims to improve the performance of SSZ-13 membranes by tuning their pore structures using an occluded organic structure-directing agent (OSDA) through low-temperature hydrocracking. The resulting membranes demonstrated notable improvements in H₂/CO₂ separation. Permeation tests indicated that the SSZ-13 zeolite membrane achieved a moderate H₂ permeance of 1.04 × 10⁻⁷ mol Pa⁻¹ m⁻² s⁻¹, along with a markedly improved H₂/CO₂ ideal selectivity of 225 at 150 °C. Both H₂ and CO₂ permeances increased significantly through the membrane with increasing temperatures, suggesting an activated diffusion mechanism for their permeation. The activation energy for H₂ permeation was calculated to be as high as 8.98 kJ mol⁻¹, suggesting that the membrane has a relatively small mean pore size and minimal defects. CO₂ adsorption and temperature-programmed desorption (TPD) analysis showed a pronounced interaction between CO₂ molecules and the SSZ-13 membrane, likely accounting for the exceptionally low CO₂ permeance observed. These SSZ-13 zeolite membranes demonstrate considerable potential for efficient H₂/CO₂ separation in practical applications.