Infrared study of the effects of oxychlorination on Pt dispersion in Pt/Al2O3 catalysts

Abstract

Chlorided Pt/Al₂O₃ has been subjected to series of consecutive oxychlorination/reduction cycles in which oxychlorination stages in each series involved heat treatment of Pt/Al₂O₃ at 723, 893 or 993 K in oxygen containing 400 ppm carbon tetrachloride. The quality of resulting Pt dispersion was monitored by infrared and volumetric study of CO adsorption. Optimum conditions for good dispersion were achieved with oxychlorination at 893 K and involved mobile oxychloroplatinum complexes in the dispersion process. The best dispersion occurred with reduced platinum atoms strongly interacting with the alumina support.