| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 75246 | Microporous and Mesoporous Materials | 2008 | 5 Pages |
The formation conditions of nitrate–cancrinite and chlorosodalite-type zeolites were studied by investigating the influence of the pH and NO3-/Cl− ratios on the synthesis of these compounds. The pH was varied by using different NaOH concentrations i.e., 3, 8 and 16 mol/L (aqueous solution) and the ratio of NO3-/Cl− ions was defined by different weight fractions of NaNO3/(NaNO3 + NaCl) i.e., 0, 25, 50, 75 and 100%. In the case of 3 M NaOH one additional experiment with 2% NaNO3 was carried out in order to investigate that area of the phase system in more detail. All of the reactions were carried out at 80 °C and under autogenous pressure for 40 h. Zeolite X was used as silicon and aluminum source. The obtained solids were characterized by powder X-ray diffraction (XRD), FTIR-spectroscopy, scanning electron microscopy (SEM) including elemental analyses using the EDX method and BET surface area measurements. The study shows that pure nitrate–cancrinite was obtained with all NO3-/Cl− compositions with NO3- contents from 2% to 100% and independently of the NaOH concentration. With 3 M NaOH and 0% NO3- (=100% Cl−) the reaction lead to a mixture of chlorosodalite and the starting material zeolite X. Pure chlorosodalite could only be synthesized if the reaction gel was formulated with 0% NO3- and at higher NaOH concentrations (8 and 16 M). These results allowed to deduce a dependency of the formation of the different phases in the studied zeolite system of the NaOH and the NO3- concentration.
