| 摘要 |
<p>Zeolitic molecular sieves of type A are prepared on the basis of a hydrate water-containing, crystalline aluminosilicate having a content of at least 99.5% by weight of particles of an average particle size of less than 45 mu m by hydrothermal crystallisation of an aluminate/water glass synthesis mixture. The components of the synthesis mixture, which has a molar ratio of SiO2 to Al2O3 of less than 1.9:1 and a molar ratio of water to alkali metal oxide of at least 30:1, are intimately mixed prior to precipitation of the amorphous preproduct. After crystallisation, the aluminium sulphate suspension is tempered and during crystallisation and/or tempering is subjected to shearing. The process makes it possible to prepare pulverulent, grit-free molecular sieves having defined particle sizes which are suitable for use as ion exchangers, especially as a phosphate substitute in detergents and cleaning agents.</p> |
