Surface Species Silica and Zeolites

Surface Species Silica and Zeolites. Whereas MAS Si n.m.r. allows one to study all Si sites in a sample, the application of CP effectively filters out Si species which are not within a few bond distances of a 1H species (see Section 6). In other words, Si n.m.r. with CP is a means to study surface phenomena provided that hydrogen-bearing species, such as OH groups, are present. 

The surface species and counterions of zeolites play an important role in their chemical and catalytic behaviour. It is one of the important and valuable aspects of CP that it allows one to study surfaces almost exclusively and monitor chemical and structural changes accordingly. The presence of surface 

SiOH groups, has been detected48,76,88 for various zeolites and their role in ring closure together with the beneficial effect of NH4+ counterions has been reported for ZSM-5.48 

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