Activation of Clayzic and its effect on the relative rates of benzylation of aromatic substrates

Abstract

The effects of the activation of K10 montmorillonite supported zinc chloride (‘Clayzic’) by different methods on the reactivity of the catalyst in the Friedel–Crafts benzylation of benzene and halo-benzenes have been investigated. There is an optimum temperature for thermal activation in air at which point a rate enhancement, compared to unactivated Clayzic, in the benzylation of benzene of greater than 30 has been achieved. The rate limiting factor for these reactions is believed to be the ability of the aromatic substrate to enter the polar mesopores containing the active zinc ions in Clayzic, causing unexpected and activation-dependent rate trends to be observed. Activation of Clayzic is believed to reduce the polar nature of the pores, so aiding partitioning of the substrate into the catalyst.