Faujasite - A.K.A. Zeolite Y
Structure and Characterization
Zeolite Y exhibits the FAU (faujasite) structure. It has a 3-dimensional
pore structure with pores running perpendicular to each other in the x,
y, and z planes similar to LTA, and is made of secondary building units
4, 6, and 6-6. The pore diameter is large at 7.4Å since the aperture
is defined by a 12 member oxygen ring, and leads into a larger cavity of
diameter 12Å. The cavity is surrounded by ten sodalite cages (truncated
octahedra) connected on their hexagonal faces. The unit cell is cubic (a
= 24.7Å) with Fd-3m symmetry. Zeolite Y has a void volume fraction
of 0.48, with a Si/Al ratio of 2.43. It thermally decomposes at 793ºC.
Zeolite Y, like zeolite A, is synthesized in a gelling process. Sources
of alumina (sodium aluminate) and silica (sodium silicate) are mixed in
alkaline (NaOH) aqueous solution to give a gel. The gel is then usually
heated to 70-300ºC to crystallize the zeolite. The zeolite is present
in Na+ form and must be converted to acid form. To prevent disintegration
of the structure from acid attack, it is first converted to the NH4+ form
before being converted to acidic form. If a hydrogenation metal such as
platinum is needed, it is deposited via impregnation or ion exchange. 
The most important use of zeolite Y is as a cracking catalyst. It is used
in acidic form in petroleum refinery catalytic cracking units to increase
the yield of gasoline and diesel fuel from crude oil feedstock by cracking
heavy paraffins into gasoline grade napthas. Zeolite Y has superseded zeolite
X in this use because it is both more active and more stable at high temperatures
due to the higher Si/Al ratio. It is also used in the hydrocracking units
as a platinum/palladium support to increase aromatic content of reformulated
refinery products. [3,4]
1. Herreros, B., The X-Ray
Diffraction Zeolite Database on the web.
2. Meier, W. M., et. al., The
Atlas of Zeolite Structure Types on the web.
3. Subhash Bhatia, Zeolite Catalysis: Principles and Applications, CRC Press,
Inc., Boca Raton, Florida, 1990.
4. Ribeiro, F. R., et. al., ed., Zeolites: Science and Technology, Martinus
Nijhoff Publishers, The Hague, 1984.
Return to the Zeolite Page