Total metallic dispersion of sulfided Pt-Re/Al2O3 naphtha reforming catalysts

Abstract

Catalysts with Pt, Re and Pt-Re supported on γ alumina were prepared by impregnation or catalytic reduction methods. The activation was performed by calcination–reduction or only direct reduction treatment. These catalysts and a commercial one were sulfided with H2S at 500°C and characterized by chemical analysis, TPR, test reactions (cyclohexane dehydrogenation and cyclopentane hydrogenolysis), chemisorption of H2 and O2 and TEM. The test reactions were affected by S according to the interaction Pt-Re and metallic dispersion of the catalysts, which are functions of the preparation technique. The presence of S inhibits H2 chemisorption, which cannot be used as a measure of the metallic dispersion. Nevertheless, sulfidation or Pt-Re alloying does not affect the O2 chemisorption and this chemisorption can be used to calculate the total (Pt+Re) metallic dispersion with a stoichiometry ratio Pt or Re/O equal to 1.