GEL SHRINKAGE AND NUTRIENT ADDITION IN UNSTIRRED BATCH ZEOLITE-A REACTION SYSTEMS

The shrinkage of the opaque portion of zeolite reaction mixtures durin g hydrothermal treatment was studied. Experimental results for unstirr ed, batch zeolite A reaction systems showed that the non-(solid gel) f raction changed during the course of the reaction. The results also sh owed that the sudden shrinkage of the opaque portion during the reacti on did not correlate with the sudden appearance of crystals in the mix ture, but was due to crystal growth. Experiments also were performed i n which nutrient materials, both with and without a nucleation control agent (triethanolamine), were added to reacting mixtures at various t imes during reaction. Nutrient additions without nucleation control re sulted in only a small increase in size of the zeolite A product. The largest crystal sizes were obtained, however, when the nucleation cont rol agent was present in the original mixture from the beginning of th e reaction. (C) 1997 Elsevier Science B.V.