ZIF-derived Co/NCNTs as a superior catalyst for aromatic hydrocarbon resin hydrogenation: Scalable green synthesis and insight into reaction mechanism

The large-scale synthesis of transition metal catalysts with high performance and their catalytic mechanism for hydrogenation is of great importance for the development of a cost-effective alternative to noble metal catalysts. Herein, we report a facile and high-yield approach for the large-scale production of highly active Co/NCNTs catalyst transformed from zeolitic imidazolate frameworks (ZIFs). The precursor ZIF-67 could be easily prepared in an aqueous solution at room temperature in a short time (∼30 min) with a high space–time-yield. Followed by low-temperature (450 °C) pyrolysis, the Co/NCNTs catalyst was obtained in high yield. Benefiting from the high density and accessible active sites, Co/NCNTs-450 exhibits high activity in hydrogenation of aromatic hydrocarbon resin (AHCR) at 160 °C and 3 MPa (for the first time below 5 MPa), which was superior to the 5 wt% Pd/C. Furthermore, a combination of kinetic experiments and density functional theory (DFT) calculations were conducted to provide insight into the mechanism of AHCR hydrogenation. The 21 kinetic models based on the Eley-Rideal (ER) and Langmuir-Hinshelwood-Haugen-Watson (LHHW) formalism were proposed to describe the kinetic data obtained via elimination of the mass transfer limitations. On the basis of the model discrimination and regression results, the LHHW mechanism presented the best fit. And all the estimated kinetic parameters, including rate constants and activation energy, could be used in a reactor design for process scale-up. The DFT calculations further corroborated the kinetic modeling results that the surface reaction of chemisorbed AHCR and the dissociatively adsorbed hydrogen was the rate-determining step.