Abstract

There are produced crystalline zeolite powders of Type A with the composition 1.0&#b1;0.2 M2/n O:Al2 O3 :1.85&#b1;0.5 SiO2 ⋅y H2 O 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 4.0μ and with a particle spectrumby hydrothermally crystallizing a SiO2, Al2 O3, Na2 O and water containing alkali aluminate, water, silicate synthesis mixture with optionally a 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 silicate soluton, heating it to a temperature between 30° and 80° C., adding to the alkali silicate solution with stirring aqueous sodium aluminate having a content of 0.1 to 100 grams Al2 O3 /l and 1 to 200 grams Na2 O/l and which had been pre-warmed to from 30° to 100° C. until the turbidity point of the reaction mixture within 10 to 60 minutes, adding with stirring to the turbid reaction mixture which had the composition SiO2 /Al2 O3 =2 to 50:1, Na2 O/SiO2 =0.2 to 20:1 and H2 O/Na2 O=4 to 300:1 an aqueous sodium aluminate which contains 10 to 200 grams/l of Al2 O3 and 10 to 250 grams/l of Na2 O having a temperature of 10° to 100° C. and allowing the thus obtained synthesis mixture to crystallize at a temperature within between 20° and 175° C. in at least 15 minutes.