Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the process for
purification of crude metal chlorides, particularly
S aluminum chloride. More particularly, the subject of
the present invention provides for a process for improv-
ing rates and yield in the purification of aluminum
chloride through the additional elemental sulfur or
equivalent sulfur containing compounds and powdered
aluminum or equivalent aluminum containing compounds
during the purification of the aluminum chloride under
agitation and the subsequent removal of trace sulfur
through granular aluminum reaction prior to the collec-
tion of the pure solid aluminum chloride.
2. General Background
The aluminum industry is illustrative of a situation
wherein high grade bauxite or other aluminum containing
ores represent limited reserves. However, kaolinitic
clay provides a virtually inexhaustible reserve for the
aluminum industry. Ore chlorination processes offer
what is the most promising economic means for removal
and recovery of the valuable aluminum chlorides; how-
ever, for example, major obstacles have been the low
rates of chlorination, the low yield of aluminum chlo-
ride, and the difficulty of obtaining aluminum chloride
in sufficient purity for use in various applications.
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The overall process of the present invention relates
to the purification of aluminum chloride which result
primarily from the carbo-chlorination of aluminum con-
taining ores to make the crude aluminum chloride itself.
The chlorination of metallic ores in the presence of the
sulfur and/or one or more functionally equivalent sulfur
containing compounds is known in the art, however, the
purification o~ the resulting crude aluminum chloride
through the addition of sulfur and/or equivalent sulfur
containing compounds for high yield of pure aluminum
chloride and aluminum powder and/or aluminum containing
compounds for high quality pure aluminum chloride and
the subsequent sublimation of the pure aluminum chlo-
ride, lends itself to an entire novel process not found
in the art.
Processes for the conversion of the various ores
into metallic halides and the subsequent purification of
the resulting metallic halide (particularly aluminum
chloride) are fairly well known in the art. Also, the
utilization of sulfur and/or sulfur containing compounds
as reducing agents during the carbo chlorination phase
of the production of aluminum cloride has been document-
ed in the literature. For example, U. S. Patent Nos.
1,858,272; 1,~22,568; and 1,405,115 all disclose proces-
ses for chlorinating clay and alumina utilizing mixtures
of chlorine and sulfur or sulfur chlorides. Also, U. S.
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Patent Nos. 1 ,581,272 and 1,325,203 describe the chlori-
nation of aluminum metals using chlorine and other
compounds. U. S. Patent No. 4,082,83~ also teaches the
process of clay chlorination, yet stopping far short of
the subsequent process for purification of the aluminum
chloride resulting therefrom.
In that regard, U. S. Patent Nos~ 3,938,969 and
U. S. Patent No. 4,035,169 both assigned to Toth Alumi-
num Corporation teach a method for the recovery of
aluminum chloride and the subsequent purification there-
of.
U. S. Patent No. 1,645,143 and Russian Patent No.
684,000 employ the use of aluminum metal being injected
into an aluminum chloride melt, the '143 patent in par-
ticular illustrating the resulting displacement of the
iron from the metal chloride and the subsequent sublima
tion of the pure aluminum chloride therefrom. However,
particularly in the 1,645,143 patent, the aluminum chlo-
ride which will result from the sublimation, which is a
very slow process, is indeed not as pure as the patent
would indicate, and thus still resulting in substantial
impure and low yield aluminum chloride. Therefore,
there is a significant need in the art for a process
which would both yield a high grade aluminum chloride
with less than 0.05% iron chloride and a high yield
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aluminum chloride from the crude aluminum chloride being
processed. Such is the case of the present invention.
GENERAL DISCUSSION OF THE PRESENT INVENTION
1. Experimental Data
Although laboratory rectification of crude AlC13
has demonstrated that product purity can be obtained,
unfortunately the high costs of materials of construc-
tion for a commercial scale AlC13 rectification pro-
cess dictated that alternative methods for purification
be investigated.
A proposed alternate process whereby pure AlC13
can be recovered from crude AlC13 is selective subli-
mation at ambient pressure. A series of laboratory
tests carried out by Toth Aluminum Corporation have
shown that effective separation can be achieved in a
three-stage sublimation system. Unfortunately a 3-stage
system would result in higher capital costs than for
rectification; therefore, it is necessary to demonstrate
that product purity can be obtained in a less expensive
operation.
Theoretical vapor pressure calculations show that at
170C a crude AlC13 solid containing 5~ FeC13 should
sublime to a vapor containing less than 0.05~FeC13.
According to the literature, however, many investigators
have demonstrated that an FeC13(AlC13)n complex
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having the same vapor pressure as AlC13 exists in the
vapor state which complicates FeC13 equilibrium
calculations. ~ifficulties in subliming the AlC13
were also encountered. However the literature is full
of work whereby pure AlC13 was obtained by subliming
AlC13 from the FeC13 in the presence of aluminum
metal.
The results o~ the experiments show that a pure
AlC13 product can be obtained by a single-stage
sublimation process using Al powder in the presence of
sulfur, and that this method is a feasible alternative
to the present rectification process.
Star'cing with a high FeC13 content in the lab,
product excellent purity (99.9% +) for the final con-
densed AlC13 product is obtained with the use of
aluminum metal powder. Although at this point the
amount of Al metal required is higher than stoichiome-
tric, further optimization tests may indicate lower Al
requirements.
To improve diffusion rate all indications are that
the AlC13 bed will have to be agitated for any commer-
cial operation.
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Addressing now the yield rates in the laboratory
experiments, it was found that although the purity
factor of the aluminum chloride obtained through subli-
mation was very high, tleSS 0.05% impure), there was
serious problems with the overall yield of the pure
aluminum chloride. Theoretically, for every mole per
unit time of crude aluminum chloride that was undergoing
sublimation, we should have obtained a mole per that
same unit time of a pure aluminum chloride. However,
such was not the case. In fact, the results were a wide
range of very low yield which had no correlation to what
theoretically should have been occurring. As an exam-
ple, under the laboratory conditions, pure aluminum
chlorlde was mixed with pure iron chloride, and through
sublimation at approximately 180 C and at one atmosphere
of pressure, the yield, although theoretically being
equal to the amount that would be starting in the
experiment, did not produce the expected yield, yet the
product was pure.
That being the case, it was decided that there was
an unknown factor which did not allow us to obtain full
yield of pure aluminum chloride during the sublimation.
At one point in the experiments, upon the sublimation of
crude aluminum chloride, which had been obtained through
carbo-chlorination, and had traces of sulfur or sulfur
compound, not only pure product was obtained, but the
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expected or calculated yield was achieved also. There-
fore, through these experi~ents, it was determined that
the elemental sulfur or an equivalent sulfur compound
was serving not as a reactant involved in the formation
S of sulfur aluminum compounds, but as a catalyst in
obtaining our yield. Therefore, the process of the
present invention was undertaken, and the purity and
high yield were achieved which will be the subject of
the claimed invention process.
2. Summary of the Invention
The overall process of the preferred embodiment of
the present invention would solve the problems being
confronted in the present state of the art in a
straightforward manner. The present invention relates
to the purification of aluminum chloride, with the crude
aluminum chloride normally being obtained through a pro-
cess of carbo-chlorination of metallic ores, in particu-
larly aluminum bearing ores, to make the metallic chlo-
rides, in particular aluminum chloride. In the present
invention, if the crude aluminum chloride does not con-
tain traces of sulfur, the crude aluminum chloride is
blended with elemental sulfur or an equivalent sulfur
containing compound and simultaneously elemental alumi-
num powder or an equivalent aluminum containing compound
in the solid state is added to the crude aluminum chlo-
ride. This blend is kept at 180 C at one atmosphere of
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pressure and is fed into a screw-type sublimer wherein
the substantially pure aluminum chloride undergoes sub-
limation in the presence of elemental nitrogen as a
purging agent and under constant agitation. The sub-
limed aluminum chloride is streamed into a reaction
ground bed containing aluminum granules at approximately
250C for removal of the traces of elemental sulfur
therefrom. The then pure aluminum chloride, in the
vapor state, is condensed for subsequent collection. If
necessary, the aluminum chloride may be further purified
through a rectification column and subsequent collection
thereafter.
Therefore, it is one of the primary ob]ects of the
present lnvention to provide a process for the purifica-
tion of metallic chlorides, particularly aluminum chlo-
ride, utilizing sulfur and/or functionally equivalent
sulfur containing compounds as a reaction promoter.
It is another principal object of the present inven-
tion to provide a process for the purification of metal
chlorides, particularly aluminum chloride, at a greater
purity utilizing the addition of powdered aluminum metal
and/or functionally equivalent aluminum containing com-
pounds.
It is yet another principal object of the present
invention to produce pure aluminum chloride through the
process of agitated sublimation at approximately 180C.
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It is yet another principal object of the present
invention to provide granular aluminum reaction to
react with the sulfur containing aluminum chloride
following the sublimation to remove the elemental sulfur
impuri t ies.
' It is yet a further object of the present invention
to provide a further step of condensation of the pure
aluminum chloride following the reaction and prior to
collection.
Among the many advantages and features of the
present invention, it is a provision for the first time
in the purification of crude aluminum chloride through
the A) injection of powdered aluminum coupled with the
B) injection of sulfur and/or functionally equivalent
sulfur compounds and C) the subsequent sublimation of
the pure aluminum chloride which is under agitation for
the yielding of commercially pure aluminum chloride.
The above objects, together with other distinguish-
ing features and advantages of the present invention
will be apparent to one skilled in the art in light of
the insuing detailed disclosure of its preferred embodi-
ment which are also distinctively claimed hereinafter.
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BRIEF DESCRIPTION OF THE DRAWINGS
For a further understanding of the nature and
objects of the present invention, reference should be
taken to the following detailed description, in
conjunction with the accompanying drawings, in which
like parts are given like reference numerals and,
wherein:
FIGU~E 1 illustrates a schematic flow diagram of the
aluminum chloride purification process in the preferred
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMEN~
In FIG~RE 1, there is illustrated in the preferred
embodiment the process of the present invention, a
blending tank 12 which is a tank relatively well known
in the art for blending various materials that are
injected thereinto. In the particular process there is
injected a principal stream 14 of aluminum chloride
which is in the crude state, i.e., 95~ aluminum chloride
with approximately 5% of other metallic chloride impuri-
ties. Also injected into the blender 12 is a stream of
preferably elemental sulfur and/or functionally equiva-
lent sulfur containing compounds. It should be noted
that if the crude aluminum chloride being injected
contains a sufficient quantity of sulfur to effect the
yield, then sulfur need not be added.
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As further seen in FIGURE 1, there is also injected
simultaneously toyether with the sulfur stream and the
crude aluminum chloride stream, a stream of preferably
powdered aluminum metal and/or functionally equivalent
aluminum containing compound, via stream 18. As seen in
the FIGURE, the injection of streams 14, 16 and 18 into
blender t2 enables the yield of aluminum ch~oride to be
significantly higher, for further steps of the process.
The mechanism by which sulfur acts as a reaction pro-
moter and to increase the rate of yield of pure chloride
as not yet been fully established. However, while not
wishing to be bound by theory, it is believed that the
active reaction promotor or catalyst is elemental
sulfur. The term "reaction promoter" comprises one of
the apparent functions of the sulfur and/or functionally
equivalent sulfur compounds as a catalytic agent rela-
tive to improvement in reaction rates achieved in the
present invention and also commonly results in a higher
yield values. However, the use of sulfur as a reaction
promoter in the purification step of purification of
aluminum chloride is a novel use of sulfur, and is thus
one of the prime basis of this particular inventive
process.
Following the blending of aluminum chloride sulfur
and aluminum powder in blender 12, the stream is then
moved via line 20 into preferably a laterally disposed
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screw-type sublimer 22. This type of screw-type subli-
mer 22 is relatively well known in the art, and there-
fore, its functioning components shall not be detailed
It is necessar~ in the particular process, that the
S container portion of sublimer 22 maintained at a temper-
ature of not less than 180 C and at an atmospheric pres-
sure not under 1 atmosphere and the blend be under
constant aqitation. ~nder these conditions, aluminum
chloride, which has been acted upon by the sulfur and
aluminum powder, sublimes in a substantially pure form
in sublimer 22 and is in the state for collection.
However, as seen in the figure, sublimer 22 has injected
into it a stream of nitrogen gas 24 which serves to
purge the contents of the sublimer and provides further
1~ for a purer stream of aluminum chloride in the sublimed
state moving out line 26, as seen in the figure, and the
byproducts collected at point 27. Following the move-
ment of the sublimed aluminum chloride, now in the vapor
state, out of sublimer 22 into line 26, it is known that
the pure aluminum chloride shall have traces of elemen-
tal sulfur contained therein, which must be removed
prior to the condensation of the aluminum chloride
product. That being the case, the stream of aluminum
chloride in line 26 is fed into a granular reactor 28
which comprises solid aluminum granules or activated
granular aluminum metal which is sufficient to remove
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the sulfur impurities and other metal chloride traces
contained in the pure alu~inum chloride. The aluminum
chloride stream moves up through granular reactor 28
into line 29, wherei~ it is then collected in a "cold
zone" at approximately 25C wherein the stream of alumi-
num chloride is then condensed in c,ondensor 31 and col-
lected as substantially pure, i.e., less than 0.05%
metal chloride or pure aluminum chloride at point 34,
with the nitrogen gas being collected from point 40.
In order to inhance the movement of the sublimed
aluminum chloride out of sublimer 22 through granulated
filter 28, the stream would tend to move from the hot
zones of the sublimer and reactor 28 into the cold zone
of condensor 31 at 25C, therefore assuring the constant
swift movement of the sublimed stream of pure aluminum
chloride through the system.
In an alternate embodiment, as 5een by phantom lines
33, should following the reacting of a stream through
reactor 28, a stream of aluminum chloride not be
sufficiently pure, the stream could then be routed
through a rectification column 35 and condense into the
condensor 31 for condensation thereinto.
As is stated earlier, the significant aspects of the
present process is the fact that elemental sulfur and/or
functionally equivalent sulfur containing compounds, are
being added to a stream of crude aluminum chloride for a
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process enhancer or yield enhancer in the purification
of crude aluminum chloride, i.e., other than as a major
reducing agent or reactant. It is well recognized in
the art, that it is very desirable in certain instances
to add sulfur and/or functionally equivalent sulfur
containing compounds to the carbo chlorination phase in
the production of crude aluminum chloride in order to
achieve considerably higher rates and yields, in fact,
the best results are achieved under certain conditions
by adding the sulfur to both pre-chlorination and carbo
chlorination steps.
However, upon the addition of one or more sulfur
compounds selected from the chemical classes defined
herein, the rate of reaction increases significantly and
much improved yields are observed. However, the carbo
chlorination reaction phase of the carbo chlorination
process is conducted within a temperature range of from
about 400-C to about l,000 C with the low temperature
range from about 600C to about 800 C, for best results.
However, although this particular use of sulfur in this
process is known in the art, the fact that the increased
temperatures in order to get an effective yield, would
not defective in the purification of aluminum chloride,
and is therefore, as taught in the present state of the
art, non applicable. It is novel to maintain the
purification temperature on or about 180C, i.e., the
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subliming temperature of aluminum chloride, and together
with the injection of elemental sulfur thereinto, the
reaction rate and yield of pure aluminum chloride is
increased dramatically. This use of elemental sulfur in
this particular stage in the purification of aluminum
chloride is a significant breakthrough in the overall
process, and will be of significant value in providing the
aluminum industry with pure aluminum chloride at a
relatively low cost in the process.
Because many varying and different embodiments may be
made within the scope of the inventive concept herein
taught, and because many modifications may be made in the
embodiments herein detailed in accordance with the
descriptive requirements of the law, it is to be under-
stood that the details herein are to be interpreted as
illustrative and not limiting in any sense.
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