n-octane reforming over alumina-supported Pt, Pt-Sn and Pt-W catalysts

Pt, Pt-Sn and Pt-W supported on gamma-Al(2)O(3) were prepared and characterized by H(2) chemisorption, TEM, TPR, test reactions of n-C(8) reforming (500 (degrees)C), cyclohexane dehydrogenation (315 (degrees)C) and n-C(5) isomerization (500 degrees C), and TPO of the used catalysts. Pt is completely reduced to Pt(0), but only a small fraction of Sn and of W oxides are reduced to metal. The second element decreases the metallic properties of Pt (H(2) chemisorption and dehydrogenation activity) but increases dehydrocyclization and stability. In spite of the large decrease in dehydrogenation activity of Pt in the bimetallics, the metallic function is not the controlling function of the bifunctional mechanisms of dehydrocyclization. Pt-Sn/Al(2)O(3) is the best catalyst with the highest acid to metallic functions ratio (due to its lower metallic activity) presenting a xylenes distribution different from the other catalysts. The acid function of Pt-Sn/Al(2)O(3) is tuned in order to increase isomerization and cyclization and to decrease cracking, as compared to Pt and Pt-W.