Abstract
In our previous paper1), we reported that hydrocracking of Taching crude on Mo- and W-catalysts was accelerated in the presence of a hydrogen-transferable solvent such as tetralin or toluene. Therefore, a tritium tracer method was used to study the mechanism of hydrogen transfer from a tritium labeled tetralin solvent in the hydrocracking of Taching Crude on Ni-W-Al2O3 at 350 and 400°C and on Ni-Mo-Al2O3 at 400°C. Such components as solvent, gas, naphtha, middle distillate, and residue in the reaction product were separated; then the tritium content in each component was determined using a liquid scintillation counter.
The ratio of tritium transferred from the solvent to each component and the ratio of the rate of hydrocracking to that of the exchange reaction of the solvent hydrogen was estimated.
Fig. 2 shows that the amount of tritium transferred from the solvent to the gas phase and product oil was small for the Ni-W catalyst at 350°C, whereas it attained to 40% for the Ni-W and Ni-Mo catalysts at 400°C.
Fig. 3 shows that the ratio of hydrogen transferred from the solvent to each component after reaction on Ni-W at 350°C was much lower than the equilibrium value, whereas the transfer reaction on Ni-W and Ni-Mo progressed appreciably at 400°C, and under all conditions of the reactions, the ratio increased in the following order; residue< middle distillate <naphtha.
Fig. 3 also shows that the ratio of exchanged gaseous hydrogen in the reactions on Ni-W at 350°C and 400°C was higher than in the reaction on Ni-Mo at 400°C.
As shown in Tables 5 and 6, under all cases, the rate of hydrogen exchange reaction was greater than the rate of hydrogen addition reaction.
From the above results, it was suggested that the solvent had a large effect on hydrocracking due to high concentrations of hydrogen atoms that were produced by the dissociation of the adsorbed solvent on the catalyst.
