On the incorporation of gallium ions into a cationic sites of pentasil ring zeolites and their acid-base, redox and catalytic properties

Abstract

Ga-zeolites of MFI and BEA topology were prepared by three different methods: conventional ion exchange of gallium ions from solution of gallium salt, reductive solid state reaction of gallium oxide with H-form of zeolite, and interaction of GaCl3 with H-form of zeolite. They were characterized by XRD, XRF, H2-TPR, FTIR, the adsorption of pyridine and d3-acetonitrile. The catalytic activity of Gazeolites was studied in plug-flow reactor in a steady state at atmospheric pressure. XRD and TPR evidence shows the presence of at leats three kinds of species: a) (GaO)+ in the cationic sites; b) gallium is in the form of bulk oxide; c) Ga3+ ions. The number of Lewis sites increases as the Broensted sites decrease upon introduction of Ga ion. (GaO)+ ions are the easiest reducible and exhibit the highest catalytic activity in ammoxidation of propane to acrylonitrile.