Temperature and Pressure Effects on the Catalytic Performance of Metalloporphyrins during Hydrogenation of Naphthalene

Temperature and pressure effects on the catalytic performance of metalloporphyrins (MPs) for naphthalene hydrogenation were studied. Naphthalene hydrogenation over MPs and sulfur (S), or S alone was examined at varying temperatures and pressures. MPs showed catalytic activity for naphthalene hydrogenation by aid of S. The catalytic activity was promoted by increasing pressure and temperature. The promotion for nickel porphyrinseemed stronger than that for vanadyl porphyrin. Excessive temperature hindered catalytic performance due to coke formation. To reveal role of temperature and pressure in catalytic performance of MPs, the demetalation was traced by ultraviolet-visible(UV/Vis) spectroscopy, and catalytic species were characterized by Raman and high-resolution transmission electron microscopy (HRTEM). High catalytic activity was correlated with high conversion of MPs. The catalytic species were mixtures of different nickel sulfide phases. High pressure and temperature facilitatedformation of crystalline metal sulfides. This work can provide guidance for activating inherent MPs in heavy oil more effectively during hydroconversion.