Comparison between tungsten carbide and molybdenum carbide for the hydrodenitrogenation of carbazole

The activity of molybdenum and tungsten carbides in hydrodenitrogenation (HDN) of carbazole was studied. Transition metal carbides (Mo₂C and W₂C) were synthesized using the temperature-programmed reaction of the appropriate oxide precursor (MoO₃ and WO₃) with the following gas mixture: 10 vol.% CH₄/H₂. The structure of the catalysts was characterized using X-ray diffraction, CO chemisorption, high resolution transmission electron microscopy (HRTEM) and BET surface area measurements. From the HRTEM analysis, it could be concluded that the tungsten carbide was thioresistant in our operating conditions (50 ppm of S, pressure = 6 MPa, 553 < T < 653 K, H₂/feed volumic ratio = 600). In the case of Mo₂C, molybdenum sulphide was observed as single slabs. The activity of catalysts was determined during the hydrodenitrogenation of carbazole at the wide range of temperature (553–653 K) and under a 6 MPa total pressure of H₂. The comparison of tungsten carbide and molybdenum carbide has shown higher activity of Mo₂C than W₂C at the same condition. However, W₂C leads to higher amount of isomers of main products, and have higher hydrogenation activity.