Nanosized Pd/Pt and Pd/Rh catalysts for naphthalene hydrogenation and hydrogenolysis/ring-opening

• Published in: Catalysis letters 2006-05, Vol.108 (3-4), p.197-207
• Main Authors: ALBONETTI, Stefania, BALDI, Giovanni, BARZANTI, Andrea, RODRIGUEZ CASTELLON, Enrique, JIMENZ LOPEZ, Antonio, QUESADA, Dolores Eliche, VACCARI, Angelo
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Catalysis; Catalysts; Catalytic activity; Chemical synthesis; Chemistry; Colloidal state and disperse state; Decalin; Dibenzothiophene; Exact sciences and technology; General and physical chemistry; Hydrogenation; Hydrogenolysis; Metal oxides; Metal particles; Metal surfaces; Moisture content; Naphthalene; Noble metals; Palladium; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Platinum; Porous materials; Rhodium; Ring opening; Silicon dioxide; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Zirconium
• ISSN: 1011-372X; 1572-879X
• DOI: 10.1007/s10562-006-0042-x

Pd/Rh and Pd/Pt catalysts supported on two different mesoporous materials – a Zr-doped MCM-41-type silica [Si/Zr = 5 w/w (SiZr)] and a commercial silica-alumina [Si/Al = 40:60 w/w (SiAl)] – were prepared by incipient wetness impregnation using nanosized suspensions of alloy particles prepared by polyol-mediated synthesis in diethylene glycol (DEG). The catalytic behaviour of these catalysts was investigated in the hydrogenation and hydrogenolysis/ring-opening of naphthalene at 6.0 MPa, by checking the role of both the main reaction conditions (temperature, contact time and H2/naphthalene molar ratio) and increasing amounts of dibenzothiophene (DBT). The catalysts supported on SiAl showed higher activity than catalysts supported on SiZr, thus suggesting that activity is favoured by higher acidity of the support and/or higher interaction of the nanosized metal particles with the support. While using the SiZr support, weaker metal-support interactions took place by forming catalysts with bigger metal and/or metal oxide particles. Besides, the catalyst with lowest noble-metal content (0.3 wt.%) (SiAl-0.3Pd/Pt-5) had the greatest acidity and metal surface and, consequently, the highest activity. Furthermore, it exhibited a good thiotolerance in presence of increasing amounts of DBT in the feed, thus maintaining a high catalytic activity in the hydrogenation of naphthalene, although with decreased yield in trans- and cis-decalin (decahydronaphthalene or DeHN) and high-molecular-weight compounds (H.M.W.), with a corresponding increased yield in the partially hydrogenated tetralin (tetrahydronaphthalene or TeHN).