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A molecular sieve is a material with pores (voids or holes), having uniform size comparable to that of individual molecules, linking the interior of the solid to its exterior. These materials embody the molecular sieve effect, the preferential sieving of molecules larger than the pores.
Clinoptilolite has many applications due to its effect as a molecular sieve, among others as an additive for building materials, as aggregate in horticulture, as an additive to cattle feed, as an additive in household products, as a desiccant, and in environmental technology.
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]
DS-PSA can also be applied to increase the oxygen concentration. In this case, an aluminum silica based zeolite adsorbs nitrogen in the first stage reaching 95% oxygen in the outlet, and in the second stage a carbon-based molecular sieve adsorbs the residual nitrogen in a reverse cycle, concentrating oxygen up to 99%.
The typical molecular sieve used is a synthetic zeolite with a pore diameter around 0.4 nanometer ( Type 4A ) and a surface area of about 500 m 2 /g. The sorption pump contains between 300 g and 1.2 kg of molecular sieve. A 15-liter system will be pumped down to about 10 −2 mbar by 300 g molecular sieve. [1]
As a result, the pore entrance of LTA is an 8-ring (0.41 nm [3]) and belongs to the small pore zeolite, while the pore entrance of FAU is a 12-ring (0.74 nm [3]) and belongs to the large pore zeolite, respectively. Materials with a 10-ring are called medium pore zeolites, a typical example being ZSM-5 (MFI).
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]
The presence of defects can make these membranes far less effective, and it is difficult to produce defect free zeolite membranes. [4] There are several mechanisms of transport that govern the separation of molecules by zeolite membranes. The main mechanisms for separation by zeolite membranes are molecular sieving, diffusion, and adsorption.