Hydrotreating of heavy vacuum gas oil (HVGO) on molybdenum and tungsten nitrides catalytic phases

A series of supported and unsupported Mo2N and W2N phases were synthesized by means of the treatment under ammonia atmosphere at 700 degreesC of Mo and W oxides. The X-ray diffraction and electron microscopy techniques verified the formation of the Mo2N and W2N ceramic phases, while the N-2 adsorption (BET) was used to determine the surface areas, between 46-133 m(2)/g for Mo2N (unsupported) and 81-101 m(2)/g for W2N (unsupported). The supported phases had surface areas between 109-113 and 109-122 m(2)/g, for Mo2N/Al2O3 and W2N/Al2O3, respectively. The catalytic hydrotreating of a heavy vacuum gas oil (HVGO) derived from Maya crude (i.e. 2.21 wt.% S, 0.184 wt.% N2) was performed on both, supported and unsupported Mo nitrides and W nitrides, which promoted the HDN reaction preferentially, up to 26.6% on Mo2N/Al2O3 and up to 22.3% on W2N/Al2O3,against 3.26% on the reference catalyst, i.e. CoMo/Al2O3 at 350 degreesC and 80 kg/cm(2). Also; the rates for HDN increased with the crystallite size in the unsupported W2N series. Also, the pore volume and mean pore diameters of the Mo2N/Al2O3 and W2N/Al2O3 series improve substantially with respect to the pure ceramic phases. (C) 2001 Elsevier Science B.V. All rights reserved.