One-Step, Continuous-Flow, Highly Catalytic Hydrogenation–Isomerization of Dicyclopentadiene to exo-Tetrahydrodicyclopentadiene over Ni-Supported Catalysts for the Production of High-Energy-Density Fuel

A one-step, continuous flow-phase, highly catalytic hydrogenation–isomerization of dicyclopentadiene (DCPD) directly into exo-tetrahydrodicyclopentadiene (exo-THDCPD) has been successfully performed over a fixed-bed reactor. This method is a greener and more cost-effective single-step route than the use of AlCl3 and noble metals (Pd, Pt, and Au) and, instead, employs a combination of Ni/γ-Al2O3 for hydrogenation and Ni/Hβ for isomerization. The bifunctional catalysts provided 100% DCPD conversion and 70% selectivity for exo-THDCPD and displayed a high stability without obvious deactivation over 200 h of testing. The synergistic effect of Ni hydrogenation activity and the isomerization activity of the supports is a key factor for the catalytic hydrogenation–isomerization of DCPD. A series of supports (ReY, USY, USReY, HY, HReY, Hβ, MCM-41, γ-Al2O3, SiO2, and NaY) were initially investigated as the Ni-supported catalysts. Surprisingly, we found that Hβ had a high activity for the isomerization of endo-THDCPD into exo-THDCPD. The integration of reactors was proposed to obtain the optimal hydrogenation and isomerization activities in a one-step, continuous flow-phase process. The physicochemical properties of the Ni-supported catalysts were studied using X-ray diffraction (XRD), O2 titration, thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), and NH3 temperature-programmed desorption (NH3-TPD). The influence of the reaction conditions, including temperature, pressure, reaction time, reduction time, liquid hourly space velocity (LHSV), Ni loading, catalyst weight ratio, calcination temperature of the catalysts, and solvents, was studied in detail.