Studies of competing hydroprocessing reactions catalyzed by Ni-Mo/.gamma.-Al2O3 and involving quinoline, indole, dibenzothiophene, and naphthalene in n-hexadecane show that marked interactions exist. The naphthalene hydrogenation rate is markedly reduced by the presence of quinoline; whereas the reactivity of quinoline is virtually unchanged by the presence of naphthalene. Similarly the rate of hydrodenitrogenation of indole, a non-basic nitrogen-containing compounds is strongly reduced by the presence of quinoline, whereas the rate of hydro-denitrogenation of quinoline, a basic nitrogen-containing compound, is unaffected by the presence of indole. The hydrogenation reactions in the dibenzothiophene reaction network are inhibited severely as indicated by the reduction in their pseudo first-order-rate constants as are the hydrogenation reactions for naphthalene. Thus the hydrogenation rate is reduced 30-fold by increasing the initial quinoline concentration from 0.0 to 0.5 wt % in naphthalene hydrogenation and in dibenzothiophene hydrodesulfurzation. The rate of direct sulfur removal is reduced by only 3-fold by increasing the quinoline concentration from 0.0 to 0.5 wt %. These results clearly show that the rate expressions for the hydrotreating reactions are of the form given in the text.

Quantitative measurement of the reactivities of methyl-substituted dibenzothiophenes, under high pressure reaction conditions (102 atm, 300°C) representative of industrial practice, has been accomplished. The catalyst was sulfided commercial Co-Mo/.gamma.-Al2O3. Methyl groups in the 2 and 8 or 3 and 7 positions show little effect. Methyl groups in the 4 position, however, reduced the reactivity by an order of magnitude and methyl groups in the 4 and 6 positions reduced it somewhat more. Dibenzothiophene (DBT) was found to be self-inhibiting and results with the methyl-substituted compounds implies that there is competitive adsorption of DBT and the methyl-substituted DBT. The reaction network involving benzonaphthothiophene and hydrogen has been determined. As before, the catalyst was typical commercial cobalt molybdate (sulfided CoO-MoO3/.gamma.-Al2O3). The reaction conditions were 68 atm and 300°C. The important result was that in contrast to dibenzothiophene, benzonaphthothiophene experiences extensive hydrogenation accompanying hydrodesulfurization, even with Co-Mo/.gamma.-Al2O3, the most selective of the available hydrodesulfurization catalysts. The sulfur-containing compounds having 3 rings or fewer experience nearly stoichiometric hydrodesulfurization (hydrogenolysis without hydrogenation), whereas the sulfur-containing compounds having 4 rings or more experience hydrogenation and hydrodesulfurization at roughly equal rates, giving products which experience further hydrogenation (and/or hydrodesulfurization - as the compound allows), again at roughly the same rates.

The refining of coal-derived liquids and, especially, the removal of harmful sulfur and nitrogen is of great scientific and practical importance. The research planned under this contract has been completed: detailed results have been provided in the fourteen quarterly reports previously issued. Brief statements concerning the status of the following tasks are presented; microreactor development; catalytic hydrodesulfurization; hydrogenation, hydrodenitrogenation reactions; reaction engineering; and characterization of aged hydroprocessing catalysts.

Three high-pressure flow microreactors and two batch autoclave reactors have been used to study the reaction networks and kinetics of (1) catalytic hydrodesulfurization of dibenzothiophene and methyl-substituted dibenzothiophenes and (2) catalytic hydrodenitrogenation of quinoline, methyl-substituted quinolines, and carbazole. At the typical conditions of 300°C and 104 atm, dibenzothiophene reacts to give H2S and biphenyl in high yield, but there is some hydrogenation preceding desulfurization. Methyl-substituted dibenzothiophenes react similarly, and each reaction is first-order in the sulfur-containing compound. Two methyl groups near the sulfur atom (in the 4 and 6 positions) reduce the reactivity tenfold, whereas methyl groups in positions further removed from the sulfur atom increase reactivity about twofold. The results are consistent with steric and inductive effects influencing adsorption. The data indicate competitive adsorption among the sulfur-containing compounds. In quinoline hydrodenitrogenation, both rings are saturated before the C-N bond is broken. Similarly, in acridine conversion, a large amount of hydrogenation precedes nitrogen removal. Breaking of the carbon-nitrogen bond is evidently one of the slower reactions in the network. The Ni-Mo catalyst is about twice as active as the Co-Mo catalyst for ring hydrogenation, and the two catalysts are about equally active for breaking the carbon-nitrogen bond. Reactivity of carbazole is similar to that of quinoline and lower than that of acridine. Again, extensive hydrogenation precedes heteratom removal.

Three high-pressure flow microreactors and two batch autoclave reactors have been used to study the reaction networks and kinetics of: (1) catalytic hydrodesulfurization of dibenzothiophene and methyl-substituted dibenzothiophenes; and (2) catalytic hydrodenitrogenation of quinoline, methyl-substituted quinolines, acridine and carbazole. The catalysts were commercial, sulfided CoO-MoO3/.gamma.-Al2O3, NiO-MoO3/.gamma.-Al2O3, and NiO-WO3/.gamma.-Al2O3. At the typical conditions of 300°C and 104 atm, dibenzothiophene reacts to give H2S and biphenyl in high yield, but there is some hydrogenation preceding desulfurization. Methyl-substituted dibenzothiophenes react similarly, and each reaction is first-order in the sulfur-containing compound. Two methyl groups near the sulfur atom (in the 4 and 6 positions) reduce the reactivity tenfold, whereas methyl groups in positions further removed from the sulfur atom increase reactivity about twofold. The results are consistent with steric and inductive effects influencing adsorption. The data indicate competitive adsorption among the sulfur-containing compounds. In quinoline hydrodenitrogenation, both rings are saturated before the C-N bond is broken. Similarly, in acridine conversion a large amount of hydrogenation precedes nitrogen removal. Breaking of the carbon-nitrogen bond is evidently one of the slower reactions in the network. The Ni-Mo catalyst is about twice as active as the Co-Mo catalyst for ring hydrogenation, and the two catalysts are about equally active for breaking the carbon-nitrogen bond. Reactivity of carbazole is slightly lower than that of quinoline but higher than that of acridine.