Abstract
Generation of Brönsted acidity in AlMCM-41 has been demonstrated by sulphation method. It was demonstrated that the sulphated AlMCM-41 was catalytically active towards liquid phase tert -butylation of phenol. AlMCM-41 mesoporous molecular sieve modified by impregnation with sulphuric acid in toluene possesses only Brönsted acid sites. The catalyst exhibits a high catalytic activity for tert -butylation of phenol with high selectivity to 2,4-di- tert -butylphenol in liquid phase. 27 Al MAS NMR study indicates that the modification of AlMCM-41 with sulphuric acid in toluene leaves only octahedrally coordinated Al species. The tetrahedrally coordinated Al species which exist before modification with sulphuric acid in toluene being dealuminated to form extraframework octahedrally coordinated Al species. The mesoporous structure of AlMCM-41 is retained after modification, but pore size decreases by ca. 3 Å by the modification. The active sites are postulated on the basis of XRD, FTIR, 27 Al MAS NMR, TGA, BET analysis and FTIR-pyridine adsorption studies that –OSO 3 H bonded to octahedrally coordinated Al species.
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