Preparation and characterization of thermostable silver on α-alumina catalysts

Abstract

A new preparative method is described for the production of thermostable, supported silver catalysts. The enhanced thermostability is brought about by “anchoring” the silver particles with tin oxide previously applied to the support. A preshaped α-alumina support was employed. Sintering of the silver particles after calcination in air at various temperatures was studied extensively by scanning electron microscopy. To obtain an highly thermostable silver catalyst, the SnO 2 must be applied as discrete particles to the surface of the support prior to the deposition of the silver. If the SnO 2 is applied as a continuous thin film, the silver particles are not thermally stabilized. Additional characterization of one of the prepared thermostable catalysts was performed by oxygen and hydrogen chemisorption measurements at 443 K. Oxidation of carbon monoxide by molecular oxygen was used both to characterize the catalyst and to test its catalytic activity. The results point unequivocally to the underlying SnO 2 being reduced at elevated temperatures (673 K), most presumably resulting in Ag Sn alloy formation.