Mesoporous molecular sieve MCM-41 with a %/A1 ratio of 39 was obtained by hydrothermal synthesis with a gel composition of 6 SiO2:O. 1 A1203: 1 hexadecyltrimethylammonium chloride:0.25 dodecyltrimethylammonium bromide:0.25 tetrapropylammonium bromide:O. 15 (NH4)20: 1.5 Na20:300 H20. The MCM-41 sample incorporating aluminum (AlMCM-41) was calcined in 0 2 flow at 813 K and subsequently ion exchanged with Na+, K+, Ca2+, and Y3+. The ion exchange levels have been increased as high as 0.41 NdA1,

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... WAl, 0.37 CdAl and 0.39 Y/Al, respectively. Hydrothermal stability of the ion exchanged AlMCM-41 materials has been investigated with X-ray powder diffraction pattern, BET specific surface area, and magicangle spinning 27Al NMR spectroscopy, after the samples were heated for 2 h at various temperatures in 0 2 flow saturated with water vapor at room temperature. The hydrothermal stability of the AlMCM-41 has been found to extend to the following temperatures depending on ion exchange: Y3+ (1170 K) x Ca2+ > Na+ (1070 K) x as calcined AlMCM-41 > pure-silica MCM-41 (980 K).