Gel shrinkage and nutrient addition in unstirred batch zeolite A reaction systems

Abstract

The shrinkage of the opaque portion of zeolite reaction mixtures during hydrothermal treatment was studied. Experimental results for unstirred, batch zeolite A reaction systems showed that the non-(solid gel) fraction changed during the course of the reaction. The results also showed that the sudden shrinkage of the opaque portion during the reaction did not correlate with the sudden appearance of crystals in the mixture, but was due to crystal growth. Experiments also were performed in which nutrient materials, both with and without a nucleation control agent (triethanolamine), were added to reacting mixtures at various times during reaction. Nutrient additions without nucleation control resulted in only a small increase in size of the zeolite A product. The largest crystal sizes were obtained, however, when the nucleation control agent was present in the original mixture from the beginning of the reaction.