Environmental Engineering Reference
In-Depth Information
CHAPTER 9
New Catalysts from Spent Catalysts
It has been shown in the preceding chapters that spent catalysts in their operating form can be
either regenerated or rejuvenated for the next utilization cycle. However, there are numerous
options for catalyst preparation when the operating size and form of spent catalysts are altered.
Metals which can be isolated from spent catalysts may be returned to the catalyst
manufacturing companies and used for catalyst preparation. In this regard, other than
hydroprocessing catalysts can also be prepared. Of course, after isolation, there are numerous
applications for the pure compounds containing metals such as Mo, W, Ni, Co, and V. For
example, the extracts containing Mo, V, and Ni obtained by leaching spent catalysts may be
used directly for catalyst preparation by impregnating conventional supports. The same extract
can be introduced to heavy feeds and as such act as catalyst during slurry bed hydroprocessing.
The processes, which can carry metal reclamation to the “extinction”, produce pure Al
2
O
3
which can be reused as the support for catalyst preparation. The production of refractories is
another potential application for the reclaimed Al
2
O
3
. There is a potential for the use of the
crushed spent hydrodesulfurization (HDS) catalyst for the hydrocracking (HCR) of vacuum
residue in a slurry bed reactor. However, its commercial application may not possible because
of the limited availability. Nevertheless, either reprocessing spent hydroprocessing catalysts
to obtain the desirable particle size and shape or crushing for use in the slurry bed
hydrocracking appear to be the most attractive options. Non-petroleum applications have been
receiving attention, although it is believed that this opportunity has not yet been
fully explored.
9.1 Petroleum Applications
Regeneration and rejuvenation of spent hydroprocessing catalysts have been conducted to
recover as much as possible of the original activity with the aim to reuse the catalyst in the
original operation. If this cannot be achieved, the regenerated and/or rejuvenated catalysts can
be cascaded to the less demanding operation. Otherwise, the spent catalysts may still be
subjected to non-conventional treatments, before they can be returned to the operation. In this
regard, significant advances have been made in reprocessing spent hydroprocessing catalysts,
in addition to several other non-conventional methods.
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