Acetylation of 2-methoxynaphthalene with acetic anhydride over a series of dealuminated HBEA zeolites

Abstract

The liquid phase acylation of 2-methoxynaphthalene with acetic anhydride was carried out in a batch reactor at 120°C over a series of HBEA zeolites resulting from dealumination of a commercial sample by treatment with chlorhydric acid or with ammonium hexafluorosilicate. Lewis acid sites which correspond to extraframework aluminium species and to transient-state species (aluminium atoms which are leaving the framework) were preferentially removed. With all the HBEA samples, acetylation of 2-methoxynaphthalene leads preferentially to 1-acetyl-2-methoxynaphtalene, this compound undergoing isomerization into 2-acetyl-6-methoxynaphthalene and 1-acetyl-7-methoxynaphthalene as well as deacylation. A maximum in acetylation and isomerization activities is found for a Si/Al ratio between 20 and 35. The low activity of the commercial sample can be related to limitations in the desorption of acetylated products from the zeolite micropores caused by the large amount of extraframework aluminium species present on this sample. Lewis acid sites were shown to be completely inactive for acetylation and isomerization reactions.