Colloidal zeolite suspensions

• A method is presented whereby it is possible to synthesize colloidal zeolite sols containing discrete zeolite particles with an average particle size of less than 150 nm and with a narrow particle-size distribution. The zeolite sols exhibit typical colloidal characteristics such as Tyndall light scattering and a low rate of sedimentation and coagulation due to electrolyte concentrations in excess of the critical coagulation concentration. The effect of sodium on the crystallization kinetics, product distribution, and particle size has been investigated. Relatively high Na2O AL2O3 ratios favor the formation of large crystals of zeolite A. Low Na2O AI2O3 ratios result in colloidal crystals of zeolite Y, whereas intermediate ratios yield zeolite Y and/or zeolite A with particle sizes of ca. 100 nm. Midsynthesis addition of sodium allows for a fivefold increase in zeolite yield.

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