Metal Reclamation from Spent Hydroprocessing Catalysts - Spent Hydroprocessing Catalysts - page 306

SYNEX DN-052 in the EXXSOL D80 [678] . In this case, Ni and Co can be readily separated
from Al after separation of Mo by a slight adjustment of pH. The separation of Ni from Co can
then be easily achieved using conventional methods described by Ritcey [679] . In this regard,
long chains alkyl amines exhibited a good performance. The Al, as the last metal left in the
original solution, can be isolated by precipitation as pure Al(OH) 3 .
The METREX process can be used as another example illustrating the use of organic agents
for the extraction of metals from leachates. The order of metals separation was identical as
those observed by Inoue et al. [622,623] and Zhang et al. [677] . The optimization of
conditions (e.g., type of agents, pH of extraction, ratio of agent/diluent, etc.) for separation of
metals from solutions using organic agents was carried out by Olazabal et al. [502,503] .
Another study involving numerous extractants is that of Sato et al. [680] .
Phosphoric acid derivatives have received the attention as potential agents for separation of
Mo from V in aqueous solutions. For example, Hirai et al. [681,682] used
bis(2-ethylhexyl)monothiophosphoric acid and bis(2-ethylhexyl)phosphoric acid. The latter
agent was efficient for the metal separation from the sulfuric acid solutions [683] , whereas
tri-n-butyl phosphate was suitable for that from the hydrochloric acid solutions [684,685] .
In the leachates containing Mo and V, the latter could be isolated by the precipitation with
(NH 4 ) 2 SO 4 at pH of 8.6 [683] . The Mo was separated from the remaining V in 0.05M sulfite
ion medium by extracting with tri-n-octylamine, stripping with aqueous ammonia and
precipitating by acidification of the stripped solution. The method based on the use of
ion-exchange resins was also suitable for the separation of Mo from V in the same solution
[660] . Among several resins, the polystyrene resin cross-linked with bis-(22-hydroxyethyl)
amino group was the most efficient for the separation of Mo from V [686] . In this case, the
solution containing Mo and V was passed through the column of the water swollen resin and
the effluent analysed.
Membrane separation is another potential method which may be applied to metal recovery
from spent hydroprocessing catalysts. The separation of active metals could be enhanced by
introducing an iminodiacetate group on the membrane [687] . The metal adsorbed from the
solution by the agent could be eluted by permeation of an HCl solution. So far, this method
was only tested for recovery of noble metals from spent catalysts. It is believed that the
membrane separation deserves attention as potential method for metal recovery from spent
hydroprocessing catalysts.
11.3 Commercial Processes
There are several companies in the world which specialize in the recovery and reprocessing of
spent catalysts. Following are the main companies involved: Gulf Chemical & Metallurgical
Corporation (GCMC) (USA), CRI-MET (USA), Taiyo Koko Co. (Japan), EURECAT