Regioselective hydrogenation of 1-naphthol over supported Pt and Pd catalysts for producing high-temperature jet fuel stabilizer

Supported Pt and Pd catalysts were examined for selective hydrogenation of 1-naphthol to form tetrahydronaphthol (THNol). Five kinds of supports were used: HY zeolite with SiO₂/Al₂O₃ of 40, HM zeolite with SiO₂/Al₂O₃ of 38, γ-Al₂O₃, SiO₂ and TiO₂. Among these five supports, only TiO₂-supported catalysts displayed selectivity for 1-naphthol hydrogenation towards 1,2,3,4-THNol. Under the same reaction conditions, Pd/TiO₂ catalysts show much higher catalytic activity and higher selectivity to 1,2,3,4-THNol than Pt/TiO₂ catalysts, and more tetralin was observed in product distribution for Pd catalysts. On the other hand, Pt/TiO₂ showed higher selectivity for 5,6,7,8-THNol. By using Pt and Pd bimetallic catalysts, much higher selectivity to 1,2,3,4-THNol has been achieved. Product distribution depends strongly on Pt/Pd ratio. The selectivity of 1,2,3,4-THNol decreases with the increase in Pt/Pd weight ratio. The bimetallic catalyst with Pt/Pd weight ratio of 0.3 shows the highest 1,2,3,4-THNol selectivity up to 22.6 mol% at 150 °C, 500 psi and 60 min. Tetralone has been found to be an intermediate for hydrogenation of 1-naphthol to 1,2,3,4-THNol. Further hydrogenation of 1,2,3,4-THNol towards tetralin is much faster than that of 5,6,7,8-THNol.