Determination of different acid sites in Beta zeolite for anisole acylation with acetic anhydride

Abstract

Catalytic roles of the acid sites in Beta zeolite for the acylation of anisole (AN) with acetic anhydride were investigated. There existed obvious difference between the Beta zeolite acidity modified with inorganic alkali cation (K+) and that modified with organic base (2,4-dimethylquinoline, 2,4-DMQ). With the increase in K+ loadings, the Beta zeolite showed decreases in both total acid strength and acylation performance. Strong acid sites played the predominant role in the AN acylation. Whereas the modifier of 2,4-DMQ mainly poisoned the Brönsted acid sites and kept the Lewis acid sites almost intact. Over the Beta zeolite poisoned by 2,4-DMQ, the AN conversion (XAN) versus the concentration of Brönsted acid sites (CB) could be represented by two linear expressions, namely XAN=37.53CB−0.20 (when 0.0053⩽CB⩽0.0167mmol/g) and XAN=2.68CB+0.38 (when 0.0167<CB⩽0.0857mmol/g).