Synthesis and thermal stability of beta zeolite using ammonium fluoride

Hydrothermal synthesis of beta (BEA) zeolite with NH4F as a fluoride source was investigated in detail. The highly crystalline BEA zeolites with a wide range of Si/Al ratios from 10 to infinity could be easily obtained. From an evaluation of the thermal stability of BEA zeolites synthesized with and without NH4F, it was found that the thermal stability of BEA zeolite synthesized with NH4F is relatively higher than that of BEA zeolite synthesized without NH4F, although the thermal stability decreases with an increase in the Al content. The addition of NaOH hardly affected the thermal stability of BEA zeolite synthesized with NH4F. The enhanced thermal stability was attributed to much less framework defects.