INVESTIGATIONS ON HYDROTHERMAL SYNTHESIS PARAMETERS IN PREPARATION OF ZEOLITE W

Abstract

Zeolite W crystals were synthesized via hydrothermal process, the influence of crystallization time, aging time and temperature, the molar ratios Al2O3/SiO2 and K2O/SiO2 on the crystalline final products were studied. The results revealed that well-developed twin-ball shaped morphology zeolite W crystals were obtained after 6 h of crystallization, the longer crystallization time would not result in substantial changes in crystal morphology and size of end products. However, the crystals transferred from twin-ball to bouquet-like in shape with increasing aging time, while the high aging temperature resulted in zeolite F developed. Also, the Al2O3/SiO2 and K2O/SiO2 molar ratios of the hydrogel had major influences on synthesis of pure form zeolite W. Well-crystallized pure phase zeolite W products were obtained with Al2O3/SiO2=0.20, which were composed of many square pillars crystals, with average width in the range of 0.2–0.5 μm and length approximately 10 μm. Mild alkalinity circumstance was in favor of zeolite W crystallization, when the K2O/SiO2 molar ratio was increased to 9.42, the product obtained was pure phase of zeolite LTJ.