The aim of this study was to develop a method to prepare the Pd/Al2O3 catalyst with an egg-shell-like structure which was used for hydrogenation of dicyclo-pentadiene (DCPD) to endo-tetrahydrodicyclo-pentadiene (THDCPD). Endo-THDCPD is isomerized to exo-THCPD, which is used as the JP-10 fuel. Catalysts with a core-shell structure usually have high product selectivity and long life time. If the reaction is fast and pore-diffusion is limited, the metal inside the particles becomes of no use. Only the metals in the shell can be used in the reaction. Pd/Al2O3 with a core-shell structure was prepared using the impregnation technique. 0.1068 g Pd(CH3COO)2 was dissolved in 150 ml toluene. γ-Al2O3 obtained from Osaka Yogyo was calcined at 1000 °C for 6 h. The particle size of the spherical-shaped alumina bead was in the range 2-4 mm. The alumina support was then dipped into the toluene solution for 3 h. The catalyst was then dried at 100 °C for 1 h, and then calcined at 350 °C for 6 h. The sample was analyzed by inductively coupled plasma-optical emission spectrometer (ICP-OES) to measure the Pd metal loading. It showed that the Pd metal loading was 0.3 wt.%. The bulk density of this catalyst was 0.68 g/cm3, and the Brunauer-Emmett-Teller (BET) surface area was 60 m2/g. Selective hydrogenation of DCPD to endo-THDCPD was carried out in a batch reactor. In this study, 30 g DCPD dissolved in 70 g n-hexane was loaded into a high pressure slurry reactor, and the catalyst was then loaded into the reactor. Hydrogen pressure was varied between 5 and 10 atm, temperature was varied between 50 and 70 °C, and catalyst loading was varied between 1.7 mg and 3.7 mg. Al2O3 was converted to δ-Al2O3 upon calcination. Pd/δ-Al2O3 showed high activity and 100% selectivity to endo-THDCPD. The kinetics study showed the rate equation was –rDCPD = 2.525 X 102 X exp (-4380/T) PH2 (mol/s. g). The activation energy was 36.42 kJ/mol and the reaction rate is first order with respect to the partial pressure of hydrogen.
Buy this Article