Tungsten-doped high-silica CHA zeolite membranes with improved hydrophobicity for CO₂ separation

High-silica CHA (SSZ-13) zeolites membranes, with pore size between the molecular size of CO₂ and N₂ or CH₄, are promising for some industrial CO₂ separation process. Considering water is typically present in these industrial gas feed and the negative impact of moisture on the membranes’ gas permeation, it is highly desirable to increase the surface hydrophobicity of membranes to reduce the adsorption of water. In this paper, a W-doping strategy was proposed to increase the hydrophobicity of SSZ-13 membranes by eliminating the silanols on the surface, and the W-doped high-silica CHA (W-SSZ-13) zeolite membranes were prepared for the first time. Characterizations such as SEM, XRD, and XPS confirmed the successful incorporation of W into CHA membrane. The incorporation of W reduced the pore mouth size, and the W-SSZ-13 zeolite membranes showed improved CO₂/N₂ and CO₂/CH₄ separation performance. After W-doping, the maximum separation factors (α_max) for the CO₂/N₂ mixture with equimolar composition under dry conditions increased from 8.8 to 16.9, and for the equimolar CO₂/CH₄ mixture, the value increased from 105.9 to 176. The W-SSZ-13 membranes also showed better separation performance under wet conditions. For both systems, the W-SSZ-13 membrane showed higher α_max and less CO₂ permeance reductions, indicating a more resistance in wet conditions.