NEW CATALYSTS FOR HYDROPROCESSING - TRANSITION-METAL CARBIDES AND NITRIDES

A series of moderate surface area transition metal carbides and nitrid es of molybdenum, tungsten, vanadium, niobium, and titanium were prepa red by temperature-programmed reaction of the oxide precursor with a r eactant gas (20% CH4/H-2 for the carbides and 100% NH3 for the nitride s). The phase purity and composition of the samples were established b y X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), while surface properties were determined by N-2 BET and CO chemisorpti on measurements. The catalysts were tested in a three-phase trickle-be d reactor for their activity in hydrodenitrogenation (HDN), hydrodesul furization, and hydrodeoxygenation, with particular emphasis on HDN. T he catalytic tests were carried out using a model liquid feed mixture containing 3000 ppm sulfur (dibenzothiophene), 2000 ppm nitrogen (quin oline), 500 ppm oxygen (benzofuran), 20 wt % aromatics (tetralin), and balance aliphatics (tetradecane). The carbides and nitrides were foun d to be active for HDN of quinoline with activity following the order group 6 > group 5 > group 4. Notably, Mo2C showed superior areal HDN a ctivity than a commercial sulfided Ni-Mo/Al2O3 catalyst (Shell 324). T he 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.