Synthesis of molecular sieves from Chilean kaolinites: 1. Synthesis of NaA type zeolites

The synthesis of NaA type zeolites has been studied at autogenous pressure using Chilean kaolins as starting materials. The ratios of SiO2/Al2O3, Na2O/SiO2, H2O/Na2O have been set at 1.9 or 2.5, 0.6 or 1.0 and 50 or 90, respectively. Reaction times have been 5 or 15 h and reaction temperature 80 or 100°C. The influence of these parameters on the textural and structural properties of the zeolite has been studied. All samples have been characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, differential thermal analysis and cation exchange capacity. The best conditions for synthesis are: SiO2/Al2O3=2.5, Na2O/SiO2=1.0, H2O/Na2O=50 and 15 h reaction time at 100°C.