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The Si/Al ratio is variable, which provides a means to tune the properties. Zeolites with a Si/Al ratios higher than about 3 are classified as high-silica zeolites, which tend to be more hydrophobic. The H + and Na + can be replaced by diverse cations, because zeolites have ion exchange properties. The nature of the cations influences the ...
Faujasite (FAU-type zeolite) is a mineral group in the zeolite family of silicate minerals.The group consists of faujasite-Na, faujasite-Mg and faujasite-Ca. They all share the same basic formula (Na 2,Ca,Mg) 3.5 [Al 7 Si 17 O 48]·32(H 2 O) by varying the amounts of sodium, magnesium and calcium. [1]
Since the metal-imidazole-metal angle is similar to the 145° Si-O-Si angle in zeolites, ZIFs have zeolite-like topologies. [2] As of 2010, 105 ZIF topologies have been reported in the literature. [ 3 ] [ 4 ] Due to their robust porosity, resistance to thermal changes, and chemical stability, ZIFs are being investigated for applications such as ...
Pentasil-zeolites are defined by their structure type, and more specifically by their X-ray diffraction patterns. ZSM -5 is the trade name of a pentasil-zeolite. As early as 1967, Argauer and Landolt worked out parameters for the synthesis of pentasilzeolites, particularly those relating to the following molar ratios: OH − /SiO 2 = 0.07–10, SiO 2 /Al 2 O 3 = 5–100, H 2 O/SiO 2 = 1–240. [1]
Most of molecular sieves are aluminosilicates with Si/Al molar ratio less than 2, but there are also examples of activated charcoal and silica gel. [2] [3] [4] The pore diameter of a molecular sieve is measured in ångströms (Å) or nanometres (nm).
The framework topology is the same as that of chabazite but SSZ-13 has a high silica composition with Si/Al > 5, which leads to low cation exchange capacity. The typical chemical formula of the unit cell can be described as Q x Na y Al 2.4 Si 33.6 O 72 • z H 2 O (1.4 < x <27)(0.7 < y < 4.3)(1 < z <7), where Q is N , N , N -1 ...
Chabazite (UK: / ˈ k æ b ə z aɪ t /) [3] is a tectosilicate mineral of the zeolite group, [4] closely related to gmelinite, with the chemical formula (Ca,K 2,Na 2,Mg)Al 2 Si 4 O 12 •6H 2 O. Recognized varieties include Chabazite-Ca, Chabazite-K, Chabazite-Na, and Chabazite-Sr, depending on the prominence of the indicated cation.
The aluminosilicate framework of LTA-type zeolite (left) and FAU-type zeolite (right). Vertices = Al or Si, oxygen atoms are not shown. Feldspar is a common tectosilicate aluminosilicate mineral made of potassium, sodium, and calcium cations surrounded by a negatively charged network of silicon, aluminium and oxygen atoms.