凝胶制备对气相合成MCM-22沸石的影响

Zeolite MCM-22 was synthesized by vaporphase transport method (VPT) with sodium silicate as silicon source, aluminium sulfate as aluminum source and HMI as the template. The characterization of xerogels was carried out using29Si MAS NMR,27 Al MAS NMR, FTIR and TEM. The effect of pH value on the structure of xerogels and synthesis of MCM-22 was investigated. It was indicated that the structure and the proportion of different composing aluminium silicates of xerogels were changed with pH value. The periods for the hydrosol turning into hydrogel increased with the increase of the pH. The xerogels had different particle sizes and properties in the different pH conditions. The alkalinity of the xerogel had very important impact on the crystallization of MCM-22. The pure MCM-22 was obtained when the pH of preparation hydrogels was between 8.7 and 10.7. MOR appeared partially when the pH value reached 11.1 and pure MOR was obtained when the pH was 11.6.