Micro- and macroscopic observations of the nucleation process and crystal growth of nanosized Cs-pollucite in an organotemplate-free hydrosol
Résumé
The nucleation and crystal growth of nanoscale cesium pollucite aluminosilicate zeolite (ANA topology) from an organotemplate-free precursor suspension are reported. By using a new and reactive synthesis recipe (5.5SiO2:1Al2O3:6Cs2O:140H2O), zeolite nanocrystals with higher Al content (Si/Al ratio = 2.12) are obtained within 120 min under mild condition (180 °C) which is much faster and safer as compared to those previously reported. The solid initially experiences amorphous phase reorganization before nucleation, crystallization and crystal growth take place. The resulting Cs-pollucite nanocrystals (average size 55 nm) display trapezohedron morphology. The nanocrystals are colloidally stabilized in water and they are very active in base-catalyzed cyanoethylation of dipropylamine reaction, giving 89.6% conversion at 180 °C within 50 min. In addition, high solid yield of nanocrystals (ca. 70%) is also achieved, thus offering a green pathway for synthesizing zeolite nanocrystals with high basicity in large scale.
Domaines
Chimie
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251. Micro- and Macroscopic Observations of the Nucleation and Crystal Growth of Nanosized Cs-Pollucite in Organotemplate-free Hydrosol.pdf (1.03 Mo)
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