Environmental Engineering Reference
In-Depth Information
Figure 11.18: General scheme for recovery of Al, Ni (or Co) and Mo after catalyst fusion with
KHSO
4
and dissolution of the fused mass in water [From ref.
662
. Reprinted with permission].
11.1.3 Chlorination
Recovery of metals from waste catalyst materials by chlorination has been studied extensively
and reported in many patents and scientific papers. A patented process developed by Gravey
et al.
[663]
comprises transforming the metals into volatile and non-volatile chlorides by
carbochlorination and then separating the chlorides in a selective manner. The residual oil
present in the spent catalyst was first removed by extraction with a solvent. After the
hydrocarbon extraction, the waste catalyst containing metal sulfides, Al
2
O
3
and coke was
treated with gaseous chlorine at a temperature between 500 and 600
◦
C. V, Mo, and Al were
converted to volatile chlorides under these conditions. Separation of AlCl
3
from other
chlorides was accomplished by passage through granules of anhydrous NaCl. MoCl
5
was
