Acidic properties of porous Ga/Cr mixed oxides intercalated in α zirconium phosphate

Porous Ga/Cr mixed oxides were intercalated within the layers of a-zirconium phosphate using a colloidal suspension of phosphate previously swelled with vapours of n-propylamine. The materials were characterised by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and N-2 adsorption-desorption. The surface acidity, both before and after poisoning with K, was evaluated by the following techniques: temperature programmed desorption of ammonia (NH3-TPD), IR spectroscopy measurements of adsorbed pyridine (Py-IR), isopropyl alcohol conversion tests and but-l-ene isomerisation tests. The catalytic activity in the vapour phase deep oxidation of methylene chloride was also tested. All samples were found to be moderately active as acid catalysts. The Bronsted type sites appeared to be located mainly on the phosphate layers and their concentration was found to be independent from the Ga/Cr ratio. Lewis acid sites appeared to be located on the surface of the intercalated oxides and their concentration reaches a maximum for a Ga/Cr ratio of 40/60. This sample also shows the highest activity for the deep oxidation of methylene chloride.