Thermal stability of [B]ZSM-5 molecular sieve

Abstract

The thermal stability of [BJZSM-5 (boronsilicalite) has been examined by IR, XRD,11B MAS NMR and XPS techniques. [B]ZSM-5 and amorphous borosilicate were converted to α-cristobalite at high temperatures (=750C). However, Na-free amorphous borosilicate was not converted to a-cristobalite at 750C. Therefore, the presence of Na ions in [BJZSM-5 would determine whether this transition occurred or not. When the phase transition to α-cristobalite occurred, most of B atoms tetrahedrally coordinated were released from the ZSM-5 structure and migrated to the exterior surface as a boron compound having trigonal BO3 units and oxidation states of 3. ？ 1991 Korean Institute of Chemical Engineering.