Electron microdiffraction study of PtSnalumina reforming catalysts

Abstract An electron microdiffraction technique was employed to identify crystal structures developed in two PtSnalumina catalysts. One catalyst was prepared by coprecipitating Sn and Al and then impregnating the calcined material with hexachloroplatinic acid to give a Pt: Sn = 1 : 3 atomic ratio. The second catalyst was prepared by coimpregnating Degussa Al 2 O 3 with an acetone solution of H 2 PtCl 6 and SnCl 4 to provide a Pt: Sn ratio of 1 :3. Pt-Sn alloy was not detected by X-ray diffraction for coprecipitated catalyst although evidence for Pt-Sn alloy was found for the coimpregnated catalyst. However, electron microdiffraction studies clearly showed evidence for Pt: Sn = 1 : 1 (hcp) alloy phase in both the catalysts. Evidence for the presence of minor amounts of Pt: Sn = 1 : 2 (fee) phase was also found for the coprecipitated catalyst. EDX analysis of selected particles show that the dominant alloy is Pt: Sn = 1 : 1 for the coimpregnated catalyst. However, for the coprecipitated catalyst, most of the Pt appear as the metal, and not an alloy. Much of the tin is not detected by EDX for the coprecipitated catalyst.