Class: Zeolite, tectosilicate
Related Materials: Zeolites, Linde Type A, Sodalite, Lazurite
Notable Properties: Gas Separation, Hydrocarbon Cracking, Catalysis, Drying Agent, Ion Exchange, Gas Sorption
Description:
Faujasite, (Na2,Ca,Mg)3.5[Al7Si17O48]·32(H2O), can be considered one of the quintessential zeolites given its simplicity in structure, natural occurrence, and the industrial importance of synthetic variants. Faujasite is a colorless rare mineral discovered in 1842 but not used industrially until the mid-20th century. As is evident in the t-site schematic, the faujasite structure can be described as a tiling of sodalite cages connected by double six-ring (d6r) units. This is very similar to the Linde Type A structure where sodalite cages are connected at the square faces by double four-ring (d4r) units.
Industrially, faujasite is sold as either type X or type Y. Zeolite Y is classified as having a silicon to aluminum ratio of 1:3 or higher and as such are typically less stable. The more anionic the lattice, however, the more strongly guest molecules will interact since there is a higher concentration of charge balancing cations (aluminate is anionic). As such, although the basic structure type is the same the application of Zeolites X and Y are quite different. Type X is a benchmark material for CO2 absorption and separation processes.
In the lab, 13X is a common drying agent used in columns upstream of a Schlenck line or in the catalyst bed of Argon and Nitrogen-filled gloveboxes. It is not in common use for drying solvents were 4A and 3A are preferred.
Topology:
FAU
Formula:
(Na2,Ca,Mg)3.5[Al7Si17O48]·32(H2O)
Space Group:
Fd-3m
Unit Cell Parameters:
a = 24.345 Å
Pore Structure:
Small cages (sodalite) with six silicon ring openings with a three-dimensional network of larger one-dimensional channels. Largest included sphere is 11.2 Å and the largest sphere that can diffuse is 7.4 Å.
Occurrence:
Natural and Synthetic (used industrially)
Links:
Database of Zeolite Structures
