New Catalysts from Spent Catalysts - Spent Hydroprocessing Catalysts - page 238

Figure 9.4: Effect of the amount of spent catalyst (catalyst A) added to boehmite on
hydrodesulfurization (HDS) and hydrodevanadization (HDV) activities [From ref. 522 .
Reprinted with permission].
effect on HDM, although it positively influenced HDS and HDN activities. This confirms that
the activity of catalysts prepared by reprocessing spent hydroprocessing catalysts exhibit the
same general trends, which are observed for the fresh commercial HDM catalysts.
Asaoka et al. [257] showed that V sulfides are active for HDM and hydrodeasphalting (HDAs).
For example, HDM was positively influenced by metal deposits until maximum of about
15 wt.% of deposits was formed [160,161] . Even unsupported V 2 S 3 exhibited some activity
during hydroprocessing reactions [163,164] . It was demonstrated that HDAs is essential for
HDM to occur [27] . Thus, in order for porphyrins to undergo HDM, they have to be liberated
from large asphaltenic entities to become available for HDM reactions. Because of the high
V/Mo ratio of catalyst C, its activity may be governed by V sulfides rather than the Ni-Mo-S