Comparison of micro- and nanoscale support for friedel-crafts benzylation of anisole

Abstract

Friedel-Crafts benzylation of anisole can be efficiently catalyzed by supported dodeca-tungstophosphorioc acid (DTP) catalysts. The use of such catalysts can eliminate or minimize the serious pollution problems associated with the conventional catalytic materials for the liquid phase benzylation of anisole with benzyl alcohol. The immense potential of these catalysts is studied and the focus of the current work is on the comparison of micro and nano scale supports based on silicalite-1 and silica impregnated with dodeca-tungstophosphorioc acid (DTP) catalysts for FC benzylation of anisole with benzyl alcohol. A 20 w% DTP impregnated on micro and nano scale supports of silicalite-1 and silica was prepared and characterized by XRD, SEM, BET and TEM technique. The liquid-phase benzylation of anisole with benzyl alcohol reaction was carried out using micro and nano scale supported DTP catalysts and the parameters such as, time-on-stream, catalyst loading, mole ratio and reaction temperature were optimized. It was observed that the support with nanocrystalline silicalite-1 impregnated with DTP showed superior activity. The activites for the benzylation were found to be in the following order. DTP/silicalite-1 (nano) > DTP/silica (nano) > DTP/silicalite > DTP/silica (commercial). The catalysts can be reused after a simple workup. The result shows that the decrease in particle size of the support enhances the surface area of the support where the active dodecaungstophosphoric acid is dispersed which is a essential factor to increase the benzylation activity and selectivity.