Spacial constraint in ZSM-5 zeolite as studied by electron spin resonance

Abstract

Copper (II) ions in ZSM-5 zeolite outgassed at 673 K occupy three different sites. Adsorption of ammonia or pyridines led to the migration of Cu (II) ions to the position where adsorbate molecules can coordinate with Cu (II) ions. The number of adsorbate molecules coordinating with Cu (II) ions can be a measure of the size of the free space in the zeolite channels. Thus, four molecules of ammonia can coordinate to Cu (II) ions easily, but the fourth one only slowly. Only two molecules of pyridine or 2-methylpyridine can be complexed with Cu (II) ions in ZSM-5 in contrast to four in Y-type zeolites.