TPD and XRD studies of molybdenum nitride and its activity for hydrodenitrogenation of carbazole

The nitrided MoO3 catalysts formed using two kinds of treatment with either NH3 or He after nitriding were studied by temperature-programmed desorption and X-ray diffraction analyses. The catalysts were cooled to room temperature in either flowing NH3 or He (NH or HE catalyst) after nitriding at 773, 973 and 1173 K with NH3. The activities of the catalysts were determined during the hydrodenitrogenation of carbazole at 573 K and 10.1 MPa total pressure. MoO2, gamma-Mo2N, and Mo metal were mainly formed in the NH catalysts nitrided at 773, 973 and 1173 K, respectively. Mo oxides and metals in the NH catalysts were nitrided to gamma-Mo2N and beta-Mo2N0.78 With low crystallinity during TPD. The surface area of the NH and HE catalysts nitrided at 773 K increased to 66 and 59 m(2) g(-1) maximum from 1.1 m(2) g(-1) of fresh MoO3, respectively, but decreased as the nitriding temperature increased to 973 K and 1173 K. The HE catalysts per surface area were more active than the NH catalysts for both the overall HDN reaction and hydrogenation, and the 1173 K-nitrided catalysts were highest. On the other hand, the NH catalysts were more active than the HE catalysts for C-N hydrogenolysis and the 973 K-nitrided catalyst showed a maximum activity for C-N hydrogenolysis. (C) 1998 Elsevier Science B.V. All rights reserved.