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/g Al2O3-Cl

L.S. CARVALHO; C.L. PIECK; M.C. RANGEL; N.S. FÍGOLI; J.M. GRAU; P. REYES; J.M. PARERA

APPLIED CATALYSIS A-GENERAL

Elsevier Sci. B.V.

Lugar: Amsterdam; Año: 2004 vol. 269 p. 91 - 103

0926-860X

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 sulfur. 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 S-tolerance 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 characterized by means of TPR, H2 chemisorption, TEM and CO-FTIR spectroscopy. The results suggest an electronic transfer from Sn and Re to Pt, greatly influencing its catalytic properties. Keywords: trimetallic catalysts; metal function; successive impregnation; electronic-geometric effects