Acidity and catalytic activity of the mesoporous aluminosilicate molecular sieve MCM-41

The acidity and catalytic properties of aluminosilicate mesoporous molecular sieves with the MCM-41 structure and bulk Si/Al ratios in the 10-60 range have been investigated. The incorporation of 4-coordinate aluminium into the structure of MCM-41 generates both Bronsted and Lewis acid sites in amounts increasing with the degree of incorporation. However, the Bronsted/Lewis acid population ratio is independent of the content of aluminium. The number and strength of acid sites generated are comparable to those of a pillared acid-activated clay and lower than in zeolite H-Y with Si/Al = 3.65. Aluminosilicate MCM-41 is a moderate catalyst for the conversion of cumene which proceeds predominantly via catalytic cracking to propene and benzene. The sample of MCM-41 with the highest content of framework aluminium (Si/Al = 10) has the largest number of Bronsted acid sites and exhibits highest catalytic activity.