Tungsten-doped high-silica CHA zeolite membranes with improved hydrophobicity for CO 2 separation

High-silica CHA (SSZ-13) zeolites membranes, with pore size between the molecular size of CO 2 and N 2 or CH 4 , are promising for some industrial CO 2 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 & Oslash;S 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 CO 2 /N 2 and CO 2 /CH 4 separation performance. After W -doping, the maximum separation factors ( alpha max ) for the CO 2 /N 2 mixture with equimolar composition under dry conditions increased from 8.8 to 16.9, and for the equimolar CO 2 /CH 4 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 alpha max and less CO 2 permeance reductions, indicating a more resistance in wet conditions.