Site Isolation or the Role of Zeolites as Solid Solvents

Site Isolation or the Role of Zeolites as Solid Solvents 

Catalytic centers can be easily isolated in the intracrystalline space of zeolites. As discussed above, the Br0nsted acid sites are isolated from a certain concentration, viz. critical Si/Al ratio, onwards. As a result it is possible to promote/suppress intramolecular versus intermolecular reactions depending on the overall chemical composition of the intracrystalline zeolite space [90]. Also, occluded metal complexes can be isolated and give rise to new catalytic chemistry [91, 92]. 

Whereas formation of natural zeolites required geological timescales, the schools around Barrer and Milton, Breck, Flanigen, and Wilson have been able to reduce this to days/hours, using more severe conditions with respect to alkalinity and synthesis temperature [24a, 93]. Numerous studies [94] allowed the scientific basis of a number of phenomena related to zeolite synthesis to be established. As a result, zeolite synthesis is now backed up by many scientific concepts, allowing occasionally tailor-made synthesis [95]. In the present section zeolitization concepts will be discussed to facilitate the catalyst manufacturer s task. 

---