ADSORPTION PROPERTIES OF MICROPOROUS SILICA PREPARED FROM METAKAOLINITE BY SELECTIVE LEACHING METHOD

概要

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Gas adsorption properties of microporous silica prcpared by selective leaching of metakaolinite were investigated at 25℃ using various adsorbates of different molecular size, shape and polarity, i.e. water, methanol, butan-1-o1, cyclohexane and 2,2,4-trimethylpentane. The microporous silica was obtained by chemical treatment of metakaolinite, (derived from the 1:1 layered clay mineral kaolinite (Al_2(OH)_4Si_2O_5) by firing at 600℃ for 24 h) with a 20 mass% H_2SO_4 solution at 90℃ for 2 h with stirring. The pore size of 0.6 nm previously obtained from the t-plot and Horvath-Kawazoe (HK) methods was examined by comparison of the results obtained from the adsorption isotherms of 2,2,4-trimethylpentane on zeolite 4A (pore size 0.42 nm), zeolite ZSM-5 (0.54 nm) and mordenite (0.67 nm). The pore size of the microporous silica was found to be between those of ZSM-5 and mordenite, in good agreement with the value derived from the t-plot and HK methods. The adsorption isotherms of all adsorbates showed a convex curve in the low partial pressure (P/P_0) range irrespective of the polarity of adsorbates, indicating micropore filling due to strong interaction between adsorbate and adsorbent in micropores. The increase of adsorption in the low P/P_0 range (P/P_0 < 0.05) changed with the shape, size and polarity of the adsorbates due to the steric hindrance and chemical affinity of the adsorbtites.
日本粘土学会の論文
1999-11-01