Infrared study on the acid sites of nitrided molybdena-alumina catalysts

The acid sites of the nitrided 12.5% Mo/Al2O3 catalysts have been studied using a diffuse reflectance FTIR spectroscopy. The activities of the nitrided catalysts for the hydrodesulfurization (HDS) of dibenzothiophene at 573 K and at 10.1 MPa were also determined. The nitride catalysts were prepared by the temperature-programmed reaction of 12.5% MoO3/Al2O3 with NH3 from 573 K to 773 K, 973 K, and 1173 K at 1 K/min and then kept at each temperature for 3 h. On the basis of the FTIR spectroscopy, it was found that Lewis acidity was predominant on the surface of the nitrided catalysts. The Lewis and Bronsted acidities were correlated with the HDS activity of the catalysts for the HDS of dibenzothiophene.