New catalysts for hydroprocessing: Transition metal carbides and nitrides

A series of moderate surface area transition metal carbides and nitrides of titanium, vanadium, niobium, molybdenum and tungsten were prepared by a temperature programmed method involving the reaction of oxide precursors with a reactant gas (20% CH{dollar}sb4{dollar}/H{dollar}sb2{dollar} for the carbides and 100% NH{dollar}sb3{dollar} 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 the surface properties were determined by N{dollar}sb2{dollar} 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 model liquid feed mixture containing 3000 ppm sulfUr (dibenzothiophene), 2000 ppm nitrogen (quinoline), 500 ppm oxygen (benzofuran), 20 wt% aromatics (5 wt% amylbenzene and 15 wt% 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 {dollar}>{dollar} Group 5 {dollar}>{dollar} Group 4. In particular, Mo{dollar}sb2{dollar}C showed higher HDN activity than a commercial sulfided Ni-Mo/Al{dollar}sb2{dollar}O{dollar}sb3{dollar} (Shell 324) catalyst. The XRD patterns of the catalysts after reaction indicated no change in the bulk structure, while XPS results showed little sulfur incorporation in the surface region of the catalysts suggesting that these materials were tolerant of sulfur.; In addition to the single metal compounds, bimetallic oxynitrides of the form M{dollar}sb{lcub}rm I{rcub}{dollar}M{dollar}sb{lcub}rm II{rcub}{dollar}O{dollar}sb{lcub}rm x{rcub}{dollar}N{dollar}sb{lcub}rm y{rcub}{dollar} (M{dollar}sb{lcub}rm I{rcub}{dollar} = Mo or W and M{dollar}sb{lcub}rm II{rcub}{dollar} = V, Nb, Mo, W, Mn, Co) were also found to be active for HDN of quinoline with V-Mo-O-N showing higher activity than a commercial sulfided Ni-Mo/Al{dollar}sb2{dollar}O{dollar}sb3{dollar} catalyst. In fact, the activity of V-Mo-O-N was found to be higher than the corresponding monometallic compounds, VN and Mo{dollar}sb2{dollar}N. X-ray diffraction patterns of the catalysts after reaction indicated that the oxynitrides consisting of early transition metals (Groups 4-6) were tolerant of sulfur, while catalysts involving metals of Group 7 and Group 8 showed bulk sulfide phases.