| 摘要 |
<p>There are produced crystalline zeolite powders of Type A with the composition 1.0+/-0.2 M2/nO:Al2O3:1.85+/-0.5 SiO2xy H2O where M is a metal cation, n is its valence and y has a value up to 6 with 50 weight % of the particles not over 5.9 mu and with a particle spectrum -Fraction ( mu ) Portion (weight %) -<3 15 to 25 -<5 35 to 55 -<10 80 to 94 -<15 96 to 100 - by hydrothermally crystallizing a SiO2, Al2O3, Na2O and water containing alkali aluminate, water, silicate synthesis mixture with an optional tempering step wherein in a given case during the crystallization or tempering step instead of stirring shearing forces are employed. The process comprises providing water in a container, simultaneously feeding into the water at a temperature of 30 DEG to 100 DEG C. an aqueous sodium aluminate liquor containing 100 to 200 grams/l of Na2O and 50 to 150 grams/l of Al2O3 and alkali silicate solution, diluting with water to obtain a gel containing synthesis premixture having the composition SiO2/Al2O3=2 to 50:1, Na2O/SiO2=0.2 to 20:1 and H2O/Na2O=4 to 300:1 adding further sodium aluminate liquor of the same composition and water having a temperature of 10 DEG to 100 DEG C. with stirring and allowing the thus obtained synthesis mixture to crystallize at a temperature within between 20 DEG and 175 DEG C. in at least 15 minutes.</p> |
