日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

The ZSM-5 powder (zeolite reference material: JRC-Z5-25H, NH₄-type) was degassed at ca. 25°C to obtain Sample I, whereas Samples II, III, IV were prepared by heating the ZSM-5 powder at 535°C under different atmospheric conditions. The SEM photographs show that the ZSM-5 powder consists of an aggregate of fine particles of ca. 200 nm and the crevices between primary particles are slit-shaped pores. The adsorption-desorption isotherms of nitrogen at 77 K were measured for Samples I～IV. The isotherms were analyzed using the t method in order to evaluate the mesoporous and microporous texture of the zeolite powder. The t plot of Sample I indicates that the slit-shaped mesopore of 3.3 nm was formed by degassing the ZSM-5 powder at ca. 25°C for 10 min. The t plots of Samples II～IV indicate that the closed micropores, which are filled mainly with water, are changed into the open micropores under the treatment of 535°C. Micropore volume depends on the atmospheric conditions; Sample III. which was heated under exposure of water vapor, has the micropore volume of 148 mm³/g, while Sample II,IV, which was heated without exposure of water vapor, has the micropore volume of 167 mm³/g. It was found that mesopore volume of Sample III is larger than that of Sample II, IV. There results lead to conclusion that the water vapor plays an important role for degradation of micropore. The degradation of micropore was influenced on acidity of ZSM-5; it was found from the NH₃-TPD curves that the acidity of Sample III is only 20% of Sample II, IV.