Naphthalene hydrogenation over Mg-doped Pt/Al₂O₃

Mg-doped alumina carriers at various alkaline earth contents (0.5–8 wt%) were prepared by incipient wetness impregnation of corresponding nitrate on sol-gel Al₂O₃ support. Pt (1 wt%) supported catalysts were obtained by pore-filling deposition from H₂PtCl₆·6H₂O on magnesium-modified carriers. Prepared materials were characterized by N₂ physisorption, infrared (IR) and UV–vis spectroscopies and temperature-programmed reduction. Textural properties of alumina substrate were not significantly affected by MgO deposition at any content suggesting well-dispersed magnesia patches. According to CO₂ adsorption analyzed by IR, surface basic properties of mixed supports were clearly enhanced with alkaline earth concentration. Reduction temperature of Pt⁴⁺ species slightly shifted to lower values by augmenting Mg content in binary supports pointing out to weakening of noble metal-mixed carriers interaction. Reduced (at 623 K, under hydrogen flow) noble metal catalysts were tested in liquid-phase naphthalene hydrogenation in tri-phasic slurry batch reactor (T = 523 K, P = 3.92 MPa). The reduced Pt catalysts supported over the binary carrier at 2 wt% Mg content had the best properties in both naphthalene conversion and consecutive tetralin hydrogenation. Nevertheless, addition of the basic additive at higher loading in the support resulted detrimental on saturating properties of corresponding noble metal-based catalyst. Selectivity to preferred cis-decalin isomer decreased over Pt materials by increasing alkaline-earth concentration in the carrier.