Friedel–Crafts acylation of anisole over hybrid zeolitic-mesostructured materials

Abstract

The application of hybrid zeolitic-mesostructured materials (HZM) as catalysts in Friedel–Crafts acylation has been investigated and compared with the behaviour of standard ordered mesoporous Al-MCM-41 and nanocrystalline ZSM-5 samples. Hybrid zeolitic-mesoporous samples were prepared from zeolite seeds obtained in different stages of ZSM-5 crystallization by assembling around cetyltrimethyl ammonium bromide (CTAB) micelles to obtain materials having a combination of both zeolitic and mesostructured properties. Acylation of anisole with acetyl chloride and acetic anhydride has been investigated over this type of catalysts, the highest conversions being obtained in all cases with the former acylating agent. The activity of the hybrid materials (HZM) was found to be remarkably higher than those exhibited by Al-MCM-41 and ZSM-5 materials, which has been interpreted as a convenient combination of accessibility and zeolitic features in the former. Deactivation, re-use and regenerability of the HZM material were also investigated. With all catalysts, a decline of activity was observed along the reaction time denoted by the fact that the conversion reaches a plateau. This deactivation is caused mainly by product inhibition associated to the strong adsorption of p-MAP on the acid sites. Nevertheless, the hybrid catalysts could be regenerated by calcination and further re-used efficiently for the anisole acylation.