Catalytic hydroprocessing of aromatic compounds: Effects of nickel and vanadium sulfide deposits on reactivities and reaction networks

Ni-Mo/gamma-Al2O3 hydroprocessing catalysts enriched in nickel and vanadium by contacting with solutions of the respective metal naphthenates were sulfided and tested for hydroprocessing of naphthalene, dibenzothiophene, and quinoline in a batch reactor at 350 degrees C and 165 atm. Approximate reaction networks were determined for each reactant, and the data showed the dependence of the pseudo-first-order rate constants on the catalyst nickel and vanadium contents. The nickel sulfide deposits only slightly affected the rate constants for hydrogenation, but the vanadium sulfide deposits led to decreases in the rate constants for hydrogenation reactions in the naphthalene network and to increases in those for hydrogenation reactions in the dibenzothiophene network. Nickel sulfide deposits led to almost no change in the rate constants for hydrogenolysis of dibenzothiophene, but vanadium sulfide deposits led to decreased rate constant for this reaction. The nickel sulfide deposits have little activity for reactions giving lower-molecular-weight (''cracking'') products, but the vanadium sulfide deposits have a relatively high activity for cracking, which suggests that they are acidic; the effects are reversed by the presence of the basic quinoline in the reactants. The results indicate a need for representing the nickel and vanadium sulfide deposits separately in process models for heavy oil hydroprocessing.