Nucleation and growth of zeolite A under reagent controlled conditions. Part II

Broad differences in the synthesis kinetics and the morphology of zeolite A from two silicate sources (soluble silicate and Ludox colloidal silica) and two different aluminium sources (aluminium isopropoxide and freshly prepared aluminium hydroxide) are reported. The differences are attributed to different rate limiting steps in the syntheses. The reactions have been followed by small angle X-ray scattering from the time of first mixing of the constituents until the final separation of zeolite A crystals. The soluble silicate and Ludox/aluminium hydroxide syntheses produce excellent cubic crystals in the 300 nm-1 μm size range. The products of the first synthesis have an interesting texture on the scale of nanometres but with aluminium isopropoxide as the aluminium source, the resulting zeolite A has a spherical morphology of size ca. 100 nm. Possible reasons for the development of these morphologies are discussed.