Note: Descriptions are shown in the official language in which they were submitted.
- l- 1109-7249D
This application is a divisional application from
Application 445,116 filed January 11th, 1984.
Application 445,116 relates to the selective extrac-tion
of rhenium metal from aqueous sulfuric acid solutlons. More par-
ticularly, it relates to -the selective extraction of rhenium metal
from sulfuric acid leach solutions, resulting from the leaching
of spent petroleum reforming catalysts, by the use of tertiary
phosphine oxide extraction compounds.
This Application relates to methods to recover -the rhen-
ium from the thus obtained leach solutions.
Rhenium is an essential element, along with platinum, inthe production of petroleum reforming catalysts. Recovery of
these valuable metals from spent catalysts is obviously desirable.
One method for recovering the metals is to leach them from the
spent catalyst with sulfuric acid. The resulting leach solution
contains, ordinarily, less than 100 ppm of rhenium metal, along
with various other metals in appreciable amounts, including
aluminum, which is generally present at a level of more than 3%.
A satisfactory method is available for the recovery of platinum
metal from the catalysts, but rhenium recovery is at present a
time consuming operation. A reduction in the time required to
recover rhenium metal, particularly in a selective manner, would
represent an economically significant improvement.
f
~2~983!L
Application 445,116 provides an ef~iclent and
economical process for the extraction ox rhenium metal
from aqueous sulfuric acid solutions and, more particularly,
for the selective recovery of rhenium metal from sulEuric
acid solutions containing other metals, which process
comprises contacting the aqueous rhenium-containing sul-
furic acid solution with a tertiary phosphine oxide com-
pound, separating the resulting rhenium phosphine oxide
complex therefrom, and recovering the rhenium metal from
the complex by contacting the complex with a suitable
stripping agent.
In accordance with Application 445,116, a rhenium
containing sulfuric acid solution is contacted with a
tertiary phosphine oxide extractant compound. Tertiary
15 phosphine oxides which are suitable for use in the present
invention as rhenium metal extractants are those which are
represented by the formula:
Rl
20 R2-P=o
l3
wherein Rl, R2 and R3 are each, independently, selected
from alkyl containing from 6 to 20 carbon atoms, cycloalkyl,
aryl, alkyl-substituted aryl, aralkyl and alkyl-substitued
aralkyl. Illustrative examples of suitable tertiary
phosphine oxides include, but are not limited to, tri-n-
hexylphosphine oxide (TIIPO), tri-n-octylphosphine oxide
(TOPO), tris~2,4,4-trimethylpentyl)phosphine oxide (TMPPO),
tricyclohexyl phosphine oxide (TCHPO), tri-n dodecyl phos-
phine oxide, tri-n-octadecyl phosphine oxide, tris(2-ethyl-
hexyl) phosphine oxide, di-n-octylethyl phosphine oxide,
di-n-hexylisobutyl phosphine oxide, octyldiisobutyl phos-
phine oxide, triphenylphosphine oxide 9 tribenzylphosphine
oxide, di-n-hexylbenzylphosphine oxide, di-n-octylbenzyl-
phosphine oxide, di-n-octylphenylphosphine oxide, and the
like. The preferred tertiary phosphine oxide co~npounds
~36~381
are tri-n-octyl phosphine oxide (TOPO), tri-n-hexyl phos-
phine oxide (THPO), and tris(2,4,4-trimethylpentyl)phos-
phine oxide (TMPPO).
The extraction of rhenium from aqueous sulfuric
acid solutions in accordance with Application 445,116 may be
accomplished by (a) solvent extraction, wherein the aqueous
rhenium-containing sulfuric acid solution is contacted with
a water-immiscible organic solvent solution of the tertiary
phosphine oxide compound, whereby the rhenium reports to
10 the organic solution as a rhenium-phosphine oxide complex,
or (b) by a supported extraction, whereby the aqueous
rhenium-containing sulfuric acid solution is passed over
or through an inert support material having absorbed
thereon or encapsulated therein the tertiary phosphine
15 oxide compound, whereby the rhenium metal is retained on
the support material.
The solvent extraction process is generally
preferred for relatively high concentrations ox rhenium
metal and the supported extraction for relatively low
20 concentrations.
In the solvent extraction process the tertiary
phosphine oxide compound is generally, and preferably,
dissolved in a suitable water-immiscible organic hydro-
carbon solvent. However, if the tertiary phosphine oxide,
25 or mixture of phosphine oxides, is a liquid at the temp-
erature of the extractin, it may be used neat. Suitable
water-immiscible organic hydrocarbon solvents include, but
are not limited to, aromatic hydrocarbons, such as toluene
and xylene; cyclohexane, naphtha, kerosine compositions,
30 and the like. A preferred solvent is an aliphatic or aro-
matic petroleum distillate composition of the kind available
commercially as, for example, Kermac*470B (Kerr-~lcCee, Inc.~),
VarsoL*Dx-364l (Exxon Co.), Ashland*360 (Ashland Oil Co.),
or Solvesso*150 (Exxon Co.);
* Trade Mark
~L~3~
In general, the tertiary phosphine oxide compound,
or mixture thereof, is used in the solution in an amount
ranging from about 20 to about 500 grams per liter of solu-
tion, and preferably from about 200 to 350 grams per liter.
Usually, it is desirable to contact the aqueous solution
with as concentrated a solution of extractant as practicable.
The aqueous sulfuric acid solutions which are
extracted in accordance with the invention usually will
contain from about 0.1 to about 5000 micrograms of rhenium
10 per milliliter of solution and, more commonly, from about
80 to about 250 micrograms of rhenium per milliliter.
The pH of the aqueous sulfuric acid solution is
important, since efficient extraction of rhenium with good
phase disengagement is achieved when the pH is in the range
15 of from about -0.5 to about 3.0 and, preferably, from about
0.1 to 0.7.
The ratio oE the aqueous phase (A) to the organic
extractant phase (O), i.e., the A/0 ratio, may be in the
range of from about 0.1 to 1000, but it is preferably in
20 the range of about 3 to 100.
The solvent extraction process may be conducted
at a temperature in the range oE from about 20C to about
85C and contact time between the two phases may vary
between about 1 and 60 minutes. In carrying out the process
25 of the invention solvent extraction techniques compatible
with an extraction solution include, but are not limited to,
liquid-liquid extraction using either mixer-settlers or
columns, such as the reciprocating plate extraction column,
pulse columns or columns employing rotating impellers.
When the extraction is conducted using a sup
ported phosphine oxide extractant, the support material
will ordinarily contain from about lQ to 60 weight percent
of the phosphine oxide compound encapsulated therein or
absorbed thereon. Preferably, the phosphine oxide is
35 encapsulated in a macroporous styrene-divinylbenzene
copolymer to the extent oE about 40% by weight. The rat;o
--5--
of phosphine oxide extractant on the support to the rhenium
in solution should range from about 0.5 to about 1000 moles
per gram-atom of rhenium and, preferably, 10 to 400 moles
per gram-atom of rhenium.
The supported extractant may either be slurried
with the aqueous rhenium-containing solution or the solu-
tion may be passed over or through the supported phosphin2
oxide in a `column. Contact time between the aqueous solu-
tion and the supported extractant may vary widely from
10 about 1 minute to many hours, but in general, the contact
time will be in the range of about 15 minutes to 20 hours
and will also depend on the temperature of the extraction,
which is normally in the range of about 20C to 50C.
Usually the rhenium metal to be extracted from
15 the aqueous solution will be accompanied by other dissolved
metals, including aluminum, calcium, iron and magnesium.
Aluminum may be present in high concentration, i.e., greater
than 3%. When the extraction process of the invention is
used, rhenium is selectively separated from these metals.
20 rhus, when rhenium extraction is high, little to none of
the aluminum, calcium or magnesium are co-extracted and
only 2-4% of the iron present is co-extracted.
Following extraction of the rhenium metal from
solution, either by solvent extraction, wherein the phos-
25 phine oxide-rhenium complex is in solution in the organic
extractant phase, or by supported extraction, wherein the
phosphine oxide-rhenium complex is retained on the support,
the rhenium metal must be recovered from the complex by a
suitable stripping procedure.
In accordance with the present invention, there
is provided a method for stripping the rhenium metal
from its phosphine oxide complex, said methocl comprising
contacting the organic solvent solution containing the
complex, as the inert support containing the complex "with
35 an aqueous solution of an ammonium salt, preferably ammonium
sulfate, whereby the rhenium metal is stripped from the
complex and reports to the aqueous phase.
--6--
The stripping solution generally will contain the
ammonium salt in an amount oE Erom about 1 to 80% by weight,
preferably 5 to 20% by weight. The ratio of stripping solu-
tion to organic extractant solution may vary widely from l to 100
volumes of stripping solution per volume extractant solution.
However, 1 - 2 volumes per volume of organic extractant sol-
ution is preferred. When the rhenium-phosphine oxide com-
plex is retained on a support material, the stripping
solution is passed through or over the support material
to recover the rhenium from the complex.
The rhenium metal may be recovered from the strip-
ping solution by conventional electrowinning or concentra-
tion methods.
The following non-limiting examples further
illustrate the invention.
Example 1
Aqueous solutions of perrhenate were prepared
from potassium perrhenate (KReO4) and SN sulfuric acid,
providing a solution containing 232 micrograms (~g) of
rhenium per milliliter at pH 1.8 and a solution containing
223 ~g/ml at pH 0.7.
These solutions were contacted with tri-n-octyl-
phosphine oxide (TOPO) dissolved in Kermac 470B (Kerr-McGee);
The extractions were conducted at 50C using an A/O ratio
Of 3.3 and a contact time of 30 minutes. Data are given
in Table I.
U CO
f
Ux
f
Us
,o Jo
.u EON I;
o Us U Us
U) a ta
.,,
a
Pi
U Jo o o
o O `--
C -
Q u I,
~,~ X I:
u l Q
pa
u
X
I}
O
i~4
,~ O
C
Cal
Eli Ei
O
I-' e,.
C '
_C
O
Example 2
The aqueous perrhenate solutions Erom Example 1
(33 ml. each) were slurried with 5.75 grams of macroreticular
polystyrene beads containing encapsulated therein 40% by
weight oE TOPO. Contact was achieved by mechanical stirring
at 25C for 19 hours. Data are given in Table II.
10
~3~
G
O
V Ox
a) o . ,!~
Ox
Ox O Q.
O JJ
Us X O
C`J
cn
o
a
O
4 O
. Lf~
V
m o ,o
X
o
o
3:: 1 001
o
o
G
O
G :1 a Cal
I;
~3~
-10-
Example 3
A leach liquor obtained by leaching a spent petro-
leum reEorming catalyst with sulfuric acid contained the
following elements:
Element Concentration, ~g/ml
Rhenium 86.1
5 Aluminum 35,700
Calcium 128
Iron . 405
Magnesium 43
Titanium
10 Nickel I .
Chromium each C10 ppm
manganese ¦
zinc J
The solutions had a pH of 1.6 and a sp. gr. of
1.23 g/l.
The procedure of Example 1 was followed to extract
rhenium from the solution directly (at pH 1.6) and following
pH adjustment to 0.4 with sulfuric acid. Data are given in
Table III.
9~
a
.,.
I,
a) a r--
cr
x
c
a) I::
on I
o
o
C I,
Us
o 'I'
G
_l
_C
Us
< .
X
o
~4
~0
O
I CO CO
C
Example 4
The procedure of Example 2 was followed to extract
rhenium from the leach liquor described in Example 3. Data
are given in Table IV.
-13-
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a)
~J
o V ox
.~ ox
_,
o
_,~ .
o
a
o
o
o
3 6
Example 5
The aqueous leach liquor described in Example 3
was contacted with solutions of TOPO in Kermac 470B at
various A/O ratios. The pH was adjusted with H2SO4. Data
are given in Table V.
~0
-15-
6~
¦ I Do
l 1 1 1 1 C I o
V
Lo I I I I C I C
X
~0 - I I I I I C I C
C
E v v
V V I: C U
-I QJ U a f
us Do
c, ,c C u, U a 3 o v
o C) O X X X
O . ,., Us
C
row o
C
¢ o
pa . ,~
U) i.
X O -- J to) ,_ 00 0--~'I
l .,1 l I h _ I _ O O O O
pa x
:~
a
_
Cal O U) O .
O OJ O 11
O O O Us O l l
o ;:r _ ox
_~ ~0
tJ _C . O
MU U O Us o o
E ¢
tn C
O :~ o c E
Pi o o .,~ o o o o o o o
En u J
.,1
¢ o o o o o l O
C yin us
X o o
o u l o o o o o o o
o --' -- --
_, _ o o o o
. _
C C Jo _ ~$
o Jo C~o~ oo CO CO Of
r O
.
O
X O ¢ I
Z
3 6
-16-
- Example 6
The organic extractant solutions containing the
phosphine oxide-rhenium complexes from Table V were then
stripped with several stripping solutions. 'rhe organic
solutions (18 ml) were contacted with 36 ml of the stripping
solutions in a stirred flask. The aqueous stripping sol-
tions were then analyzed for rhenium recovered. Data are
given in Table VI.
.
-17-
l 1 1 1 . .
O O
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I:: E
o l 1 1 1 o o
C:
ui r1
C Lo ,~ 1 1 1 1 o o
u ¢
O
O
o
Us
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o l u I ox
. I, C pa I It f
X Do O
JJ
U Pi X
O :~:
E C C
, a .,~
C Us
C UU U U
. ,~ E xX X X
o ^~
W Jo
_l o
I: E
Q~ O O
I l lw U ~Co o
O ::~ )~ o
. .u
O o or: X
Y a
us
o
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oo Y v~v~
I: a
a) , ,~
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æ
Lo Z
Y v~Q~E--l I! a JO a
ox 3333 3:
0~ OOOO O
,~
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Y :~ _ x -- _
us o us
X O
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