Influence of Crystallization Temperature on Crystal Size and Morphology in the Synthesis of Zeolite NaX

Zeolites NaX were prepared by a hydrothermal method and the influences of crystallization temperature on the end products were investigated. The samples synthesized were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and particle size analysis. The results indicated that the products synthesized 25 and 40 degrees C were composed of many closely packed nanocrystals with the average size of around 30 nm, while the products obtained at 60 degrees C exhibited slightly larger nanocrystal sizes. The average crystal particle sizes prepared at 25, 40 and 60 degrees C were measured to be 265, 298 and 602 nm, with their distributions in the ranges of 150-360, 178-420 and 352-794 nm, respectively. Higher crystallization temperature favoured the aggregation of individual nanocrystals, which resulted in the formation of larger steady congregated agglomerates. However, the products synthesized at high temperature (95 degrees C) were big single crystals. The reasons may be attributed to the dominant nucleation due to much slower diffusion rates and crystal growth kinetics at low temperatures.