Organic template residues confined in silicalite-1 zeolite membranes for tuning pore structures and boosting H2/CO2 separation

Silicalite-1 zeolite membranes were successfully activated at 300–350 °C in a hydrogen atmosphere. FTIR, TGA, and N 2 adsorption-desorption characterizations confirmed that the amount of the organic structure directing agent (OSDA) residue in silicalite-1 zeolite channels was tunable. The H 2 -calcined membrane showed a lower gas permeance than that of the air-calcined membrane due to the partial pore blockage by the OSDA residue. The permeance of H 2 and CO 2 increased with increasing temperature, showing an activated diffusion-like mechanism. The activation energies for the permeation of H 2 and CO 2 were in the range of 1.63–4.15 and 0.76–5.90 kJ mol −1 , respectively, which confirmed the reduced average membrane pore size and different pore surface chemistry due to the presence of the OSDA residue in the membrane. Significant interactions between CO 2 molecules and OSDA residues confined in the membrane resulted in a notably lower CO 2 permeance compared to N 2 and CH 4 , despite CO 2 having a smaller kinetic diameter. Enhanced H 2 /CO 2 selectivity in the silicalite-1 zeolite membrane, featuring confined OSDA residue, was attributed to the reduction in membrane pore size and the fine-tuning of pore surface chemistry.