Rapid preparation of high-silica CHA-type zeolite membranes and their separation properties

High-silica CHA-type zeolite membranes (HS-CHA membranes) have attracted considerable attention as zeolite membranes with high permeability, separation performance, and stability. However, long hydrothermal reaction times are required to form HS-CHA membranes. Therefore, in this study we investigated more rapid preparation methods to produce high performance HS-CHA membranes for practical applications. In our preparation process, FAU-type zeolite and N,N,N-trimethtyl-1-adamantammonium hydroxide were used as a raw material and structure-directing agent, respectively, through the secondary growth of seed crystals. As a result, the HS-CHA membranes could be prepared in a 5-h hydrothermal reaction. The permeation properties of the membranes were determined for pervaporation for either ethanol (EtOH), 2-propanol (IPA), or acetic acid (AcOH) solution containing water at 348 K. The permeation flux and separation factor of 80 wt% IPA solution with the use of the HS-CHA zeolite membrane with a Si/Al ratio of 11 were 20 kg m−2 h−1 and 1128, respectively. Furthermore, the gas separation performances of the HS-CHA membranes for binary mixtures of CO2 and CH4 were evaluated. For an equimolar mixture of the gases at 313 K, the CO2 permeance and the selectivity were 1.5 × 10−6 mol m−2 s−1 Pa−1 and 115, respectively.