How molecular sieve works?
Synthetic zeolites are produces in the form of granular extrudates, which have different microcrystalline structures. The input window of the molecular lattice can vary in size from 2-15 angstroms depending on what chemical process the zeolites are intended for. But their main purpose is the dehydration, purification, and separation of gases and liquids.
Separating different molecules is achieved by altering the size of the input window-depending on the size of the window, only certain sized molecules are adsorbed onto the zeolite surface.
For example, water molecules are smaller than both carbon dioxide and oxygen molecules, and are thus easily “trapped” by a zeolite’s crystal lattice 3 angstroms wide whereas other molecules simply bounce off the surface. Synthetic zeolite granules have a system of secondary pores and channels through which gases can be percolated. Libra specialists measure these pores using special units. Surface analyzers are used to measure micropores and mesopores in the range of 0.8 to 100 nanometers. This method is based on zeolite adsorption of nitrogen at liquid nitrogen temperature. A mercury porosimeter is used for measuring pores from 5 to 10000 nanometers.
Distribution of the secondary pores according to their sizes is very important. A dominance of small pores can lead to a choking of the pores by coke and to diffusive restriction, shortening the zeolite’s lifespan.
A dominance of macropores reduces the strength of the granule. Libra specialists managed to find the ultimate solution to this problem, and a way to optimize the balance between different pore sizes.
