Framework Types and Compositions

As mentioned above, the main types of zeoHtes in industrial catalytic application today are Zeolite Y (FAU) and its variants, ZSM-5 and SUicahte (MFI), Mordenite (MOR) and Beta (BEA). After the first commercial synthesis of X and Y zeolites in the mid- to late 1940s by workers at the Union Carbide Corporation [21, 22], 

Zeolite Beta with its three-dimensional channel system appears more suitable for conversion of gas oil feeds containing large molecules in FCC and hydrocracking processes and has indeed received much attention in the scientific and technical literature [38-40]. It exhibits very strong acidity which exceeds that of stabihzed Y zeolites. While the three dimensional pore system of this zeoHte with its 12-member pore mouth makes it suitable for use in processing heavier feedstocks, its more tortuous chaimel system appears to impart a tendency to selectively crack normal paraffins as compared to Y-zeolite. A close look as the channel geometry 

Silicoaluminophosphates (SAPOs), along with their crystalline aluminum phosphate counterparts (ALPOs), first discovered by Union Carbide workers in the early 1970s [41, 42], derive their acidity through the substitution of framework phosphorous by silicon thereby creating the charge imbalance which, when compensated for by protons, creates acidic centers. SAPOs in general have seen limited use in bond-breaking applications primarily due to weaker acidity, framework stability, or technoeconomic reasons. Of the rich variety of structures available, 

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