Hydrodenitrogenation of Heavy Oil (Part 1)

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Hydrodenitrogenation catalysts were prepared by impregnating nickel and molybdenum onto 10 kinds of solid acid carriers, mainly Al2O3 or SiO2. The activity test of catalysts was performed with the apparatus shown in Fig. 1. Typical reaction conditions were: temperature 380°C; pressure 140kg/cm2G; liquid hourly space velocity 2.0hr-1; and hydrogen flow rate 1, 000Nl/l. The catalyst properties and reaction results are shown in Table 2. Strengths and amounts of acid of some of the catalysts were determined by ammonia desorption curves at temperatures ranging from 200 to 600°C. Ammonia desorption was measured using the apparatus shown in Fig. 3. Illustrated in Fig. 4 is an example of the NH3 desorption curve and tabulated in Table 3 are the results.Fig. 5 shows the intrinsic activity of HDN (kn) and that of HDS(ks). These catalysts can be classified into three groups depending on the extent of kn and ks; i.e., an Al2O3-MOx group having high kn and high ks, a SiO2-MOx group having low kn and low ks, and an Al2O3 group having low kn and high ks. The reason as to why HDN activity of SiO2 MOx catalysts is smaller than that of Al2O3-MOx catalysts, is probably due to the difference in the hydrogenation activities of both groups. The effect of acidity on kn is shown in Fig. 6 in which a correlation proportional to acidity and kn appears to exist for SiO2-MOx catalysts, but such a correlation is not obvious for Al2O3-MOx and for Al2O3 catalysts.Illustrated in Fig. 7 is a correlation between HDN activity per acid amount and acid strength. It reveals that, in general, the catalysts having high acid strength (notably Al2O3 catalysts) possess low HDN activities. It is supposed that the high HDN activities of Al2O3-MOx catalysts depend on their suitable acid strength. It is remarkable that AB-06 catalyst which was prepared by merely impregnating AB-01 catalyst with B2O3 and whose acidity is equal to that of AB-01 showed higher HDN activity and lower acid strength than that of AB-01 catalyst.