| 摘要 |
There are produced crystalline zeolite powders of Type A with the composition 1.0+/-0.2M2/nO:Al2O3:1.85+/-0.5SiO2.yH2O where M is a metal cation, n is it valence and y has a value up to 6 with 50 weight % of the particles not over 4.3 mu and with a particle spectrum: -Fraction ( mu ) Portion (weight %) -<3 18 to 38 -<5 70 to 82 -<10 93 to 99 -<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 an aqueous alkali aluminate liquor having a temperature of 30 DEG to 100 DEG C. and containing 0.1 to 100 grams of Al2O3/l and 1 to 200 grams of Na2O/l, feeding in an alkali silicate solution within 10 to 200 minutes to obtain a clear reaction solution having the composition SiO2/Al2O3=50 to 1000:1, Na2O/SiO2=0.2 to 20:1 and H2O/Na2O=4 to 300:1, adding with stirring to the synthesis mixture an aqueous sodium aluminate which contains 10 to 200 grams/l of Al2O3 and 10 to 250 grams/l of Na2O having a temperature of 30 DEG to 100 DEG C. 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.
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