Generation of Bronsted acidity in AlMCM-41 by sulphation for enhanced liquid phase tent-butylation of phenol

AIMCM-41 mesoporous molecular sieve modified by impregnation with sulphuric acid in toluene possesses only Bronsted 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. Al-27 MAS NMR study indicates that the modification of AIMCM-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 AIMCM-41 is retained after modification, but pore size decreases by ca. 3 A by the modification. The active sites are postulated on the basis of XRD, FTIR, Al-27 MAS NMR, TGA, BET analysis and FTIR-pyridine adsorption studies that -OSO3H bonded to octahedrally coordinated Al species. (C) 2007 Elsevier B.V. All rights reserved.