Montedison S.p.a.

Fabio Pastorello

Claudio Troglia

The synthesis of zeolites 4A having a high crystallinity and a fine granulometry is disclosed, by the addition in a first stage of a sodium silicate solution to a sodium aluminate solution (containing an excess of NaOH and heated to a temperature of from 50.degree. to 100.degree. C.), and by the crystallization in a second stage at a temperature of from 70.degree. to 105.degree. C., characterized in that the temperature of the sodium silicate solution is lower by at least twenty Centigrade degrees than that of the sodium aluminate solution, the molar ratios SiO.sub.2 :H.sub.2 O and SiO.sub.2 :Na.sub.2 O in the sodium silicate solution being respectively from 0.030 to 0.150 and from 1.95 to 2.30, and the weight ratio between the reaction mother liquor and the zeolite thus formed being from 6.5 to 20.

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Milan, Italy

Fabio Pastorello