New Catalysts from Spent Catalysts - Spent Hydroprocessing Catalysts - page 237

Table 9.4: Properties of feedstock [From ref. 524 . Reprinted with permission].

Density (kg/L) 0 . 977

Sulfur (wt.%) 4 . 30

Nitrogen (ppm) 2740

H/C 1 . 58

CCR (wt.%) 12 . 20

Asphaltenes (wt.%) 3 . 78

Metals (ppm)
Vanadium

69

Nickel 21

Distillation, ( ◦ C)
IBP

391

40% 560

Recovery volume (%) 57 . 1

The effect of V on HDS activity is rather different than that of Mo, as it is shown in Fig. 9.7
[522] . It is essential that the results in Fig. 9.6 are considered in the context of results in
Fig. 9.4 . Thus, the change in HDS conversion shown in Fig. 9.7 can be attributed to the
combined effects of all metals, i.e., V, Ni, and Mo. Of course, it is not easy to decouple these
effects. However, the Ni/Mo and V/Mo ratios in Table 9.2 [522] indicate that for catalyst A,
the interference of contaminant metals with active Ni-Mo-S phase should be least evident
compared with the other two catalysts. Then, a significant decline in HDS activity from
catalyst A to catalyst C suggests that during sulfiding, particularly that of the catalyst C, the
active Ni-Mo-S phase was only partially developed. It is believed that for this catalyst, the
HDS activity was dominated by V sulfides with a little contribution from the Ni-Mo-S phase.
This is in accordance with the high V/Mo ratio ( Table 9.2 ) for catalyst C. This is consistent
with the catalytic activity of V sulfides (e.g., V 2 S 3 ,V 3 S 4 ,VS 2 ) for HDS, although much lower
than that of Mo sulfide, observed by Loos et al. [255] . It may be therefore concluded that there
is an upper concentration of V (e.g., 5 wt.%) in spent catalyst above which the HDS activity

of the reprocessed catalysts may be only partially recovered.

∼

The effects of Mo content on HDV and hydrodenickelization (HDNi) at 370 and 390 ◦ C are
compared in Fig. 9.6 [522] . It is believed that at both temperatures, the activities were similar
when accumulated errors are taken into consideration, although at low Mo contents, a scatter
of the results was observed. These results also show that the Mo content is determining factor
for HDM activity in agreement with the other studies [27] . Thus, the HDM activity tends to
level off above 3 wt.% Mo. At Mo content greater than 3 wt.%, the addition of Ni had little