Metal Reclamation from Spent Hydroprocessing Catalysts - Spent Hydroprocessing Catalysts - page 304

Figure 11.21: Extraction of metals (A) with 20 vol.% LIX 63 in EXXSOL D80 and (B) with 20
vol.% Cyanex 272 in EXXSOL D80 [From ref. 622 . Reprinted with permission].
Some typical examples involving spent hydroprocessing catalysts were selected to describe
these events in more details.
An important contribution to the development and testing of the organic agents used for the
extraction of metal compounds from various solutions obtained by dissolution of spent
catalysts was made by Inoue et al. [622,623] . Before the extraction method could be applied,
the spent CoMo/Al 2 O 3 catalyst deposited with V and Ni was roasted at 700 ◦ C, then roast was
suspended in 63% H 2 SO 4 and evaporated to dryness. After dissolving in water and filtered, the
filtrate was diluted to attain pH of 1.2 and extracted. With respect to the purity of isolated
metals, pH of the solution may be the most critical parameter. This was demonstrated by the
results shown in Fig. 11.21 [622] . In this case, before the extraction, the solution contained
2.7, 0.75, 0.03, 13.5, 1.0, and 0.17 g/L of Mo, V, Fe, Al, Co, and Ni, respectively. An excellent
separation of the Mo from the other metals in the scrub solution could be achieved at pH
approaching zero when 20 vol.% Cyanex 272 in EXXSOL D 80 as diluent was used as
extracting agent ( Fig. 11.21b ). Subsequently, the aqueous solution of ammonia could be used
to strip Mo from the extract. In this case, a good separation was achieved when pH of the
extract was maintained between 8.0 and 8.4. After the Mo separation, pH of the scrub solution
was increased to 1.5 by the addition of Ca(OH) 2 powder. At this pH, V was separated with