New Catalysts for Hydroprocessing: Transition Metal Carbides and Nitrides

Article abstract of DOI:10.1021/j100044a025

A series of moderate surface area transition metal carbides and nitrides of molybdenum, tunsten, vanadium, niobium, and titanium were prepared by temperature-programmed reaction of the oxide precursor with a reactant gas (20percent CH4/H2 for the carbides and 100percent NH3 for the nitrides).The phase purity and composition of the samples were established by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), while surface properties were determined by N2 BET and CO chemisorption measurements.The catalysts were tested in a three-phase trickle-bed reactor for their activity in hydrodenitrogenation (HDN), hydrodesulfurization, and hydrodeoxygenation, with particular emphasis on HDN.The catalytic tests were carried out using a model liquid feed mixture containing 3000 ppm sulfur (dibenzothiophene), 2000 ppm nitrogen (quinoline), 500 ppm oxygen (benzofuran), 20 wt percent aromatics (tetralin), and balance aliphatics (tetradecane).The carbides and nitrides were found to be active for HDN of quinoline with activity following the order group 6 > group 5 > group 4.Notably, Mo2C showed superior areal HDN activity than a commercial sulfided Ni-Mo/Al2O3 catalyst (Shell 324).The XRD analysis of the spent catalysts indicated no change in the bulk structure, while XPS results showed little incorporation of sulfur in the surface region of the catalysts, suggesting that these materials are tolerant of sulfur.