A study of the acidity of SAPO-34 by solid-state NMR spectroscopy

Using multinuclear solid-state NMR in combination with probe molecule techniques, we examined the acidic property of SAPO-34 with different Si content. The results show that there are two kinds of Bronsted acid sites in SAPO-34 with the acid strength of one kind higher than that of ZSM-5. The Si species and their distribution in the framework depend on the Si content. A large amount of Si islands are formed when Si content is high, at lower Si content, only isolated Si(OAl)(4) species exists. The Si content has little effects on the Bronsted acid strength of SAPO-34, but does affect the acid concentration. (C) 2012 Elsevier Inc. All rights reserved.