A physico-chemical study of Ga-ZSM-5 zeolite

Abstract

X-Ray powder diffraction, scanning electron microscopy, ion-exchange capacity, methylene blue adsorption measurements and i.r. spectral data of absorbed nitrogen dioxide, pyridine and acetylacetone have been used to characterize the Ga-ZSM-5 zeolite. Ion-exchange capacity studies have shown that the Ga³⁺ is incorporated into the zeolitic framwork over a wide range of Ga³⁺ contents. Staining of the zeolitic crystals by methylene blue has been used to assess the simultaneous formation of silicalite and Ga-ZSM-5 zeolite and compare with that found in the formation of the Fe³⁺ and Al³⁺ forms of the zeolite. The order of tenacious metal isomorphous substitution into the framework is Fe³⁺ > Ga³⁺ > Al³⁺. Methylene blue adsorption studies show the order of greatest Brønsted acidity is Al-ZSM-5 > Ga-ZSM-5 > Fe-ZSM-5.