tamis moléculaire
- Domaine
-
- chimie
- Date
Définition :
Composé piège (aluminosificate naturel ou synthétique) dont la structure est constituée par les enchaînements tridimensionnels de molécules tétraédriques d'oxyde de silicium et d'aluminium liées par leurs sommets.
Terme :
- tamis moléculaire n. m.
Traductions
-
anglais
Date :Définition
A term used to describe the function of zeolite materials, which are clay-like in chemical nature (aluminosilicate compounds), and from which all water can be removed without alteration of their molecular structure.
Note :
As a result of this, the material becomes microporous to such an extent that about half its volume is occupied by very small holes or channels (cages). The material thus readily absorbs molecules of other substances in much the same manner as activated carbon; however, such molecules must be small enough to enter the pore vacated by the water molecules. Because of the limitation placed by the pores on the size of absorbed molecules, zeolites act as selective devices which absorb smaller molecules readily by reject larger ones. For this reason, they are called molecular sieves. They tend to accept polar molecules as well as unsaturated types. Their more important uses are in water purification by ion exchange and in the cracking of petroleum; they are also active in soil chemistry because of their ion-exchange capability.
Terme :
- molecular sieve