Prominent catalytic activity of Ga-containing MCM-41 in the Friedel-Crafts alkylation

Ga-containing MCM-41 were prepared by addition of Ga to the synthesis gel (Ga-MCM-41) or by impregnation of Ga onto MCM-41 (Ga/MCM-41), and their structure, acid properties and catalytic properties were studied. In the as-synthesized form of Ga-MCM-41, the introduced Ga was incorporated in the MCM-41 network structure, which was confirmed from the EXAFS and the Ga-71 NMR. The transformation to the H-form caused the partial elimination of Ga from the MCM-41 network. The nature of acid sites generated on Ga was studied by IR and NH3 temperature programmed desorption methods. Lewis acid sites were dominant independent of the preparation methods as evidenced by the IR of adsorbed pyridine. Ga-containing MCM-41 exhibited prominent activity in the liquid phase reaction between benzyl chloride and benzene (Friedel-Crafts alkylation) under such a low temperature as 313 K. The highest yield of diphenylmethane was obtained on the Ga impregnated MCM-41. Ga2O3 located outside the MCM-41 network was considered to bear active species for the reaction. (C) 2001 Eisevier Science B.V. All rights reserved.