Silica sol gel assisted defect patching of SSZ-13 zeolite membranes for CO2/CH4 separation

Intercrystalline defects are commonly present in zeolite membranes formed during membrane synthesis and calcination process. Therefore, the selection of a suitable post-treatment method is of particular importance. In this work, SSZ-13 membrane defects were significantly reduced by dipping in the different ethanol/TEOS molar ratios of the silica sol solutions. Characterizations including FTIR, FESEM, EDX, BET, and gas adsorption isotherms of CO2 and CH4 revealed that silanes groups were properly placed on the surface of the zeolite while the crystal structure and zeolitic pores remained intact. Permporometry analysis was also carried out to find the effectiveness of the applied patching method. Permeation of CO2 and CH4 and CO2/CH4 ideal and mixture selectivity through the fresh and improved membranes was investigated. The results showed that ethanol/TEOS molar ratio of 95.5 increased the single gas selectivity from 33 to 176 at 30 degrees C and the pressure difference of 100 kPa, while the permeation of CO2 declined by 15%. In the mixed gas conditions, the selectivity of CO2/CH4 reached a really high value of 660, proving that this post-treatment modification is very effective in SSZ-13 zeolite membrane.

Automated summary

Intercrystalline defects in zeolite membranes can be significantly reduced by dipping in silica sol solutions with different ethanol/TEOS molar ratios, leading to improved gas selectivity and permeation properties. The post-treatment modification with a specific ethanol/TEOS molar ratio effectively enhances the CO2/CH4 selectivity in SSZ-13 zeolite membranes under mixed gas conditions.