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KMID : 1059519960400030202
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Journal of the Korean Chemical Society
1996 Volume.40 No. 3 p.202 ~ p.208
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The Effect of Dealumination on the Structure and Acidity of SAPO-11 Molecular Sieve
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Park Jong-Yul
Lee Chi-Hun
Kim Soo-Kyung
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Abstract
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SAPO-11 was synthesized hydrothermally and dealuminated with H4EDTA. The framework structure of SAPO-11 was maintained safely by 24 hours' dealumination, but further dealumination for 48 hours caused SAPO-11 collapsed and to be changed to variscite(AlPO4·2H2O) and tridymite(SiO2). Dealuminated SAPO-11 showed two structural hydroxyl bands at 3607 cm-1 and 3453 cm-1 respectively. The intensities of these two bands increased according to the extent of dealumination, and disappeared by the adsorption of methylamine. Dealuminated SAPO-11 showed higher desorption temperatures and greater activation energies in desorption of water and methylamine compared to non-dealuminated SAPO-11. All the phenomena may be due to the stronger interactions of Brψnsted acid sites of structural hydroxyl groups generated by dealumination with adsorbed water and methylamine molecules respectively.
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