Effects of the Active Phase of CoMo/γ-Al2O3 Catalysts Modified Using Cerium and Phosphorus on the HDS Performance for FCC Gasoline

The modified CoMo/gamma-Al2O3 catalysts with different Ce and/or P loading were prepared by the incipient wetness impregnation method. The catalysts were characterized using X-ray fluorescence spectroscopy, N-2-adsorption-desorption, pyridine Fourier transform infrared, H-2 temperature-programmed reduction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The effect of Ce and/or P on the active phase, acidic properties, and catalytic activity of the CoMo/gamma-Al2O3 catalysts were investigated in detail. The results showed that the phosphorus additive can slightly increase the stacking number of MoS2 slabs by reducing the metal-support interaction. Also, the addition of a small amount of cerium (1.75 wt %) not only increased the average slab length and stacking layer number of MoS2 slabs, but also formed new Bronsted acid sites on the support, which efficiently enhance the thiophene hydrodesulfurization (HDS) and olefins isomerization activity of the catalyst. These favorable effects are more obvious in cases where cerium and phosphorus coexist. The CoMo/gamma-Al2O3P(2)Ce(1.75) catalyst exhibited the highest thiophene HDS and olefin isomerization conversion values of 98.58 and 19.51%, respectively. The high isomerization activity is able to inhibit the loss of gasoline octane number. Based on the above results, it can be concluded that the synergistic effect between Ce and P can achieve deep desulfurization and minimize the loss of octane number by modulating the acidity of the support and optimizing the active phase of the sulfided catalysts.