Hydroprocessing of a Maya residue.: Intrinsic kinetics of sulfur-, nitrogen-, nickel-, and vanadium-removal reactions

A residue from a Maya crude was processed in a hydrotreating unit with a continuous stirred tank reactor at high temperatures (375-415 degrees C) and hydrogen pressures (10-15 MPa). A commercial guard-bed demetalation catalyst Ni-Mo supported on gamma-Al2O3 was used. In this paper, the intrinsic kinetics of the sulfur-, nitrogen-, nickel-, and vanadium-removal reactions are reported. The sulfur-removal reactions fit second-order kinetics, the nitrogen-removal reactions half-order kinetics, the nickel-removal reactions first-order kinetics, and the vanadium-removal reactions half-order kinetics. The nickel-removal reactions showed the highest value for the activation energy. The sulfur-removal reactions were the only ones that had a dependence on the hydrogen pressure in every range of hydrogen pressures studied, 10-15 MPa, and a kinetic order of 0.4 has been observed. For nitrogen-, nickel-, and vanadium-removal reactions, an increase of the pseudokinetic constants was only observed between 10 and 12.5 MPa. The percentages of sulfur-removal range from 22% to 79.3%, nitrogen conversion from 3.7% to 50.9%, nickel conversion from 32.1% to 98.8%, and vanadium conversion from 40.1% to 99.7% at 375 degrees C, 10 MPa, and 7.1 Uh g(cat) and 415 degrees C, 12.5 MPa, and 3.3 L/h g(cat). The relationships between the percentages of sulfur-removal and metal-removal were studied.