Hydrogenation of benzothiophene- free naphthalene was examined over various transition metal (rhodium, ruthenium, palladium, and platinum) catalysts supported on charcoal in supercritical carbon dioxide (ScCO2) solvent at low temperature (313 K). Among these, a charcoal -supported rhodium catalyst was found to be the most active, while a charcoal -supported ruthenium catalyst was found to give the highest cis-decahydronaphthalene (cis-decalin) selectivity. A systematic investigation of hydrogenations of naphthalene and tetrahydronaphthanele (tetralin) in ScCO2 revealed that naphthalene hydrogenation is a consecutive and cis- and trans-decalin were formed via tetralin. (C) 2007 Elsevier B.V. All rights reserved.