| Summary: | Ammonia (NH<sub>3</sub>) and hydrogen sulfide (H<sub>2</sub>S) are hazardous and odorous gases. A special device that is not affected by other gases is necessary so that it can detect such gases. Zeolite membranes can separate the desired component selectively by molecular sieving and selective adsorption. LTA-, MFI-, and FAU-type zeolite membranes were prepared in this study, and the permeation and separation performances were determined for the ternary mixture of NH<sub>3</sub>, H<sub>2</sub>S, and N<sub>2</sub> to develop an NH<sub>3</sub> selectively permeable membrane. Although the separation factors of NH<sub>3</sub> were high enough for the LTA-type zeolite membrane, the NH<sub>3</sub> permeance was the lowest among the three membranes. In contrast, the FAU-type zeolite membrane with Si/Al = 1.35 showed a high enough NH<sub>3</sub> permeance and a NH<sub>3</sub>/N<sub>2</sub> separation factor. The membrane modification and varying the membrane composition were carried out to reduce the H<sub>2</sub>S permeance. As a result, the H<sub>2</sub>S permeance could be decreased by modification with silane coupling agents, and a separation factor of NH<sub>3</sub> toward H<sub>2</sub>S of over 3000 was achieved.
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