Trimetallic naphtha reforming catalysts. I. Properties of the metal function and influence of the order of addition of the metal precursors on Pt–Re–Sn/ -Al2O3–Cl

Abstract

Trimetallic Pt–Re–Sn catalysts supported on chlorided alumina were prepared by successive impregnation, following different orders, of the metal precursors. The content of each metal was 0.3% (w/w). The catalysts were tested in the reaction of cyclohexane dehydrogenation which was also poisoned by sulphur. The results of bimetallic Pt–Sn and Pt–Re catalysts indicate that the influence of Sn in decreasing Pt activity is greater than that of Re. Trimetallic catalysts present smaller catalytic activity and thiotolerance than Pt and the bimetallics indicating an additive action of Re and Sn on Pt. The rate of deactivation during S addition is intermediate between the ones of Pt–Re and Pt–Sn, suggesting a simultaneous poisoning of Pt–Re and Pt–Sn sites. The metallic function was further characterised by means of TPR, H2 chemisorption, TEM and CO-FT-IR spectroscopy. The results suggest an electronic transfer from Sn and Re to Pt, greatly influencing its catalytic properties.