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

• We studied the acylation of anisole with acetic anhydride over Beta zeolite.
• The Brönsted/Lewis acid concentration of poisoned Beta samples was determined.
• Strong acid sites played the predominant role in the anisole acylation.
• The contribution of external surface acid sites to the reaction can be ignored.
• The relation between Brönsted acid sites and anisole conversion was calculated.

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 ⩽ 0.0167 mmol/g) and XAN = 2.68CB + 0.38 (when 0.0167 < CB ⩽ 0.0857 mmol/g).

Over Beta-N samples with similar concentrations of Lewis acid sites, the relationship between anisole conversion (XAN) and the concentration of Brönsted acid sites (CB) could be represented by two linear expressions: XAN = 37.53CB − 0.20 (when 0.0053 ⩽ CB ⩽ 0.0167 mmol/g); XAN = 2.68CB + 0.38 (when 0.0167 < CB ⩽ 0.0857 mmol/g).Figure optionsDownload high-quality image (38 K)Download as PowerPoint slide