U.S. patent number 3,801,307 [Application Number 05/275,257] was granted by the patent office on 1974-04-02 for metal reduction process.
Invention is credited to Frank W. Hurd.
United States Patent |
3,801,307 |
Hurd |
April 2, 1974 |
METAL REDUCTION PROCESS
Abstract
An improved metal reduction process permits the efficient
production of metals from reducible metal compounds by means of a
reducing metal. The reducible metal compound and a stoichiometric
amount of a reducing metal are introduced into a sealed reaction
zone and heated to a temperature which is above the melting point
of the reducing metal but below the temperature at which a
reduction reaction between the reducible metal compound and the
molten reducing metal will proceed spontaneously. In this
temperature range, a reduction reaction is initiated between the
reducible metal compound and the molten reducing metal by suddenly
disrupting the surface of the molten reducing metal and allowing
the reduction reaction to continue to completion.
Inventors: |
Hurd; Frank W. (Le Sueur,
MN) |
Family
ID: |
23051505 |
Appl.
No.: |
05/275,257 |
Filed: |
July 26, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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833378 |
Jun 16, 1969 |
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Current U.S.
Class: |
75/395; 75/593;
75/617; 75/623; 75/399; 75/616; 75/622 |
Current CPC
Class: |
C22B
5/04 (20130101); C22B 34/1272 (20130101); C22B
5/06 (20130101) |
Current International
Class: |
C22B
34/00 (20060101); C22B 5/00 (20060101); C22B
34/12 (20060101); C22B 5/04 (20060101); C22B
5/06 (20060101); G22b 005/00 (); C22b 053/00 () |
Field of
Search: |
;75/84.5,62,84.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Epstein; Reuben
Attorney, Agent or Firm: Jones and Lockwood
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of Ser. No. 833,378,
filed June 16, 1969, now abandoned.
Claims
What is claimed is:
1. A reduction process for the production of metal, which process
includes the steps of
a. introducing into a reaction zone without premixing a halide
selected from the group consisting of halides of titanium,
zirconium, hafnium, uranium, vanadium, niobium, thorium, beryllium,
molybdenum and mixtures thereof and a reducing metal selected from
the group consisting of sodium, potassium, calcium, barium,
magnesium, lithium and mixtures thereof, said reducible metal
compound and said reducing metal being introduced in amounts
providing not more than 10 percent excess of either reactant over
stoichimetric requirements for complete reduction of the reducible
metal halide to reduced metal,
b. sealing the reaction zone,
c. heating the reactants without substantial agitation from a
temperature below the melting point of the reducing metal to a
temperature which is both above the melting point of the reducing
metal and below the temperature at which a reduction reaction
between the metal halide and the molten reducing metal will proceed
spontaneously,
d. initiating a reduction reaction between the metal halide and the
molten reducing metal by suddenly disrupting the surface of the
molten reducing metal by means of a mechanical force sufficient to
provide a dispersion of the reducing metal in intimate contact with
the reducible metal compound,
e. permitting the reduction reaction to continue to thereby produce
a reduced metal in a zero-valence state; and
f. thereafter removing said reduced metal from the reaction
zone.
2. The process of claim 1 wherein the reducing metal is an alkali
metal selected from the group consisting of sodium, potassium and
lithium.
3. The process of claim 1 wherein the reducing metal is selected
from the group consisting of sodium, potassium, sodium mixed with
barium, and sodium mixed with calcium.
4. The process of claim 1 wherein the reducible metal halide is
selected from the group consisting of halide of titanium and
zirconium.
5. The process of claim 4 wherein the reducing metal is an alkali
metal selected from the group consisting of sodium, potassium and
lithium.
6. The process of claim 4 wherein the reducing metal is selected
from the group consisting of sodium, potassium, sodium mixed with
barium, and sodium mixed with calcium.
7. The process of claim 6 wherein the reducible metal halide is
selected from the group consisting of titanium tetrachloride and
zirconium tetrachloride.
8. A reduction process for the production of metal, which process
includes the steps of
a. introducing into a reaction zone without premixing molybdenum
sulfide and a reducing metal selected from the group consisting of
sodium, potassium and lithium and mixtures thereof, said molybdenum
sulfide and said reducing metal being introduced in amounts
providing not more than 10 percent excess of either reactant over
stoichiometric requirements for complete reduction of the
molybdenum sulfide to molybdenum metal,
b. sealing the reaction zone,
c. heating the reactants without substantial agitation from a
temperature below the melting point of the reducing metal to a
temperature which is both above the melting point of the reducing
metal and below the temperature at which a reduction reaction
between the molybdenum sulfide and the molten reducing metal will
proceed spontaneously,
d. initiating a reducing reaction between the molybdenum sulfide
and the molten reducing metal by suddenly disrupting the surface of
the molten reducing metal by means of a mechanical force sufficient
to provide a dispersion of the reducing metal in initmate contact
with the molybdenum sulfide,
e. permitting the reduction reaction to continue to thereby produce
molybdenum metal,
f. thereafter removing said molybdenum metal from the reduction
zone.
9. The process of producing titanium metal which comprises:
a. introducing titanium halide and sodium into a reaction zone
without pre-mixing and in amounts providing not more than 10
percent excess of either reactant over stoichiometric requirements
for complete reduction of the titanium halide to titanium
metal;
b. sealing the reaction zone;
c. heating the reactants without substantial agitation from a
temperature below the melting point of sodium to a temperature
which is both above the melting point of sodium and below the
temperature at which a reduction reaction between the titanium
halide and molten sodium will proceed spontaneously;
d. initiating a reduction reaction between the titanium halide and
molten sodium by suddenly disrupting the surface of the molten
sodium;
e. permitting the reduction reaction to continue to thereby produce
titanium metal; and
f. thereafter removing consolidated titanium metal from the
reaction zone.
10. The process of claim 9 wherein the titanium halide comprises
titanium tetrachloride and wherein the titanium halide and sodium
are present in amounts providing not more than 5 percent excess of
either reactant.
11. The process of claim 9 wherein the titanium halide comprises
titanium tetrachloride and wherein the titanium halide and sodium
are present in substantially stoichiometric proportions.
12. The process of claim 11 wherein the maximum temperature of step
(c) is between 120.degree. and 400.degree. C.
13. The process of claim 11 wherein the disruption of step (d) is
caused by sudden vertical shaking of the molten sodium.
14. The process of producing zirconium metal which comprises:
a. introducing zirconium halide and sodium or mixtures of sodium
and calcium into a reaction zone without pre-mixing and in amounts
providing not more than 10 percent excess of either reactnat over
stoichiometric requirements for compelte reduction of the zirconium
halide to zirconium metal;
b. sealing the reaction zone;
c. heating the reactants without substantial agitation from a
temperature below the melting point of sodium or the mixture of
sodium and calcium to a temperature which is both above the melting
point of sodium or the mixture of sodium and calcium and below the
temperature at which a reduction reaction between the zirconium
halide and molten sodium or mixture of sodium and calcium will
proceed spontaneously;
d. initiating a reduction reaction between the zirconium halide and
molten sodium or the mixture of sodium and calcium by suddenly
disrupting the surface of the molten sodium or the mixture of
sodium and calcium;
e. permitting the reduction reaction to continue to thereby produce
zirconium metal; and
f. thereafter removing consolidated zirconium metal from the
reaction zone.
15. The process of claim 9 wherein the zirconium halide comprises
zirconium tetrachloride and wherein the zirconium halide and sodium
or mixtures of sodium and calcium are present in amounts providing
not more than 5 percent excess of either reactant.
Description
BACKGROUND OF THE INVENTION
Numerous processes exist for the production of metals and their
alloys from reducible compounds of such metals. For example,
titanium and other metals have been produced by processes which
involve reacting the corresponding metal halide, such as titanium
tetrachloride, with a reducing metal, such as magnesium, under
reducing conditions. One existing procedure involves the trickling
or other slow addition of titanium tetrachlorideonto or across the
top of a large mass of tetrachloride onto magnesium in an effort to
reduce the titanium from its polyvalent form to its zero valence
state, while producing magnesium chloride as a by-product.
Further, experiments have been conducted by others in which a
reducible metal compound and a reducing metal have been placed in a
small closed reaction vessel and heated therein, without agitation,
to a thermal initiation temperature at which a reduction reaction
between the reducible metal compound and the molten reducing metal
will proceed spontaneously. However, when such a spontaneous
reaction is initiated, the reaction proceeds so rapidly that
enormous internal pressures are developed within the closed
reaction vessels. Accordingly, it is uncommon for large bulk
reactions to be performed by the foregoing procedure on a
commercial scale. Instead, industry has relied on procedural
modifications involving the slow and incremental addition of one or
both of the reactants to a closed reaction zone which is maintained
at or near atmospheric pressure. However, this modified procedure
also has its disadvantages since the modification involves the
time-consuming steps of selecting, monitoring, and changing the
rates of addition of the reactants to the closed reaction zone in
order to control the temperature of the reaction zone. As an
example of the time-consuming nature of the modified procedure,
according to one reported procedure used by the U.S. Bureau of
Mines, titanium tetrachloride was slowly fed into a reaction vessel
above the surface of a large bath of molten magnesium which was
enclosed within the reaction vessel. 2 hours after the titanium
tetrachloride addition was begun, only 40 percent of the total
amount of the reactant had been introduced into the reaction
vessel.
SUMMARY OF THE INVENTION
The present invention relates to an improved metal reduction
process which permits the efficient production of a metal from its
reducible metal compound by reacting substantially all of the
reducible metal compound simultaneously with substantially all of a
reducing metal in a closed reaction zone without encountering the
extremely high pressure conditions or time-consuming steps common
to the existing procedures discussed above.
Briefly described, the process of this invention includes the
following steps. A reducible metal compound and a reducing metal
are introduced into a reaction zone, without any pre-mixing of
these reactants, in amounts usually not more than 10 percent excess
of either reactant over the stoichiometric requirements for the
complete reduction of the metal compound to the zero valence state
of the metal. After the reaction zone is sealed, the reactants are
heated therein, without any significant agitation of the reactants,
from a temperature below the melting point of the reducing metal to
a temperature which is above the melting point of the reducing
metal but below the thermal initiation temperature at which the
reduction reaction will proceed spontaneously. After the reactants
are brought to within the foregoing temperature range, a reduction
reaction is initiated between reducible metal compound and the
reducing metal by suddenly disrupting the surface of the molten
reducing metal and allowing this reaction to continue spontaneously
and exothermically to thereby produce the zero valence state of the
reduced metal. Subsequently, the reduced metal is withdrawn from
the reaction zone.
An important feature of the present invention is that the reactants
are maintained at a temperature significantly below the thermal
initiation temperature before the reduction reaction is initiated
by the sudden disruption of the surface of the molten reducing
metal. The thermal initiation temperature in this case is defined
as the temperature to which the reactants must be heated at rest in
a sealed reaction vessel to cause the reaction to proceed
spontaneously without disrupting the surface of the molten reducing
metal and then to continue to react to completion without the
benefit of externally supplied heat or agitation.
Another important feature of the present invention, is that after
the reduction reaction is completed, the product, the zero valence
state of the reduced metal, is substantially separated from the
by-product salt and can be easily recovered from the reaction
vessel.
THE DRAWINGS
FIG. 1 is a side elevation of an apparatus, including a reaction
vessel, which can be used in the practice of this invention on a
laboratory scale.
FIG. 2 is a cross-sectional view of the reaction vessel shown in
FIG. 1. This view is taken along the lines 2--2 in the direction of
the arrows in FIG. 1.
DETAILED DESCRIPTION
THE REDUCIBLE METAL COMPOUND
The process of the present invention is applicable to any metal
compound which can be reduced with a molten reducing metal. Such
reducible compounds include the halides, oxides and sulfides of
titanium, zirconium, hafnium, vanadium, niobiom, tantalum, silicon,
germanium, tin, lead, thorium, uranium, boron, beryllium, and the
like. Among the various compounds of these metals, the metal salts
of the common inorganic acids are preferred. The metal halides are
particularly preferred, especially the halides of the metals found
in groups IVA, IVB, VA, VB, VIA, and VIB of the Periodic Chart. To
a somewhat lesser extent, the halides of metals of groups IIIA,
IIIB and the actinoid Series can be used to advantage in the
present process.
Illustrative reducible metal compounds are TiCl.sub.4, TiBr.sub.4,
TiF.sub.4, ZrCl.sub.4, BeCl.sub.2, SnCl.sub.4, NbCl.sub.5,
VCl.sub.4, TaCl.sub.5, UCl.sub.4, UF.sub.6, ThCl.sub.4 Fe.sub.2
O.sub.3, Nb.sub.2 O.sub.5, CoO and MoS.sub.2.
Reducible metal compounds of the transition metals are very useful
in this invention. Of the transition metals, titanium and zirconium
are preferred. The present invention is usually well suited for the
production of titanium from titanium tetrachloride and zirconium
from zirconium tetrachloride.
Further, alloys of the various metals discussed above can be
produced by the process of the present invention. For example, a
titanium-tin alloy can be formed by reacting a reducible metal
compound of titanium, such as TiCl.sub.4, and a reducible metal
compound of tin, such as SnCl.sub.4, in the presence of a suitable
reducing metal, such as sodium, within the conditions of the
present method.
The metals which can be used as reducing agents in the present
invention include any metal which is capable of reducing the
selected reducible metal compound. As is known in the art, metals
which will reduce certain compounds will not reduce all compounds.
However, the selection of a suitable reducing metal is within the
skill of the art once the reducible metal compound is identified or
selected.
The reducing metals used in the practice of this invention can be
selected from the group consisting of alkali metals, such as
lithium, sodium, and potassium; the alkaline earth metals, such as
magnesium, barium, and calcium; aluminum; and the rare earth misch
metals.
Preferred reducing metals include sodium, magnesium, potassium,
lithium, barium, calcium and mixtures thereof. Sodium, mixtures of
sodium with barium, sodium with calcium and sodium with potassium
are particularly useful as reducing metals for reducible metal
halide compounds, such as TiCl.sub.4, BeCl.sub.2, ZrCl.sub.4,
VCl.sub.4, NbCl.sub.5, TiB.sub.4, TiF.sub.4, and UF.sub.6.
Although aluminum is not a good reducing metal for producing metals
from reducible metal halide compounds, it does function
satisfactorily as a reducing metal for other reducible metal
compounds, such as Fe.sub.2 O.sub.3, Cr.sub.2 O.sub.3, TiO.sub.2,
ZnO.sub.2, and mixtures of FeO and TiO.sub.2.
Selection of Suitable Reactants
In many instances, the selection of the reducible metal compound is
limited by the availability in commercial quantities of reducible
compounds of the selected metal. For example, titanium
tetrachloride is commercially available or can be prepared from
commercially available raw materials. Accordingly, titanium
tetrachloride is one primary source of titanium metal.
The selection of a suitable reducing metal is within the skill of
the art when aided by this disclosure. Factors to be considered in
selecting a reducing metal for use in the process of this invention
include the following:
1. The ability of the reducing metal to react with the reducible
metal compound under the anticipated conditions of use.
2. The melting point and boiling point of the reducing metal
compared to those of the reducible metal compound.
3. The cost and commercial availability of the reducing metal.
4. The relationship between the melting point of the reducing metal
and the thermal initiation temperature for the reduction reaction
for the selected combination of reducible metal compound and
reducing metal.
5. The type of by-products produced during the reduction
process.
As previously indicated, particularly effective combinations of
reducible metal compound and reducing metal are the combination of
titanium tetrachloride and sodium metal, and the combination of
zirconium tetrachloride and sodium metal.
Relative Amounts of the Reactants
When possible, the relative amounts of reducing metal and reducible
metal compound which are used in the practice of this invention
should be substantially stoichiometric. Ordinarily it is not
necessary to use any significant excess of either of the reactants,
and the use of substantial excesses, for example, over 25 percent
excess of either reactant, should be avoided. Ordinarily, the
process of this invention requires less than 10 percent excess of
either reactant, and desirably less than 5 percent excess of either
reactant. Preferably, less than 1 percent excess of either reactant
is most desirable.
The Temperature
The temperature at which the reaction of the present invention is
initiated, by the sudden disruption of the surface of the molten
reducing metal, is below the boiling point of the reducing metal
and can range from the melting point of the reducing metal up to
within about 50.degree. C. of the "thermal initiation temperature"
for the reduction reaction.
By "thermal initiation temperature," I mean the temperature to
which the reactants must be heated at rest in a sealed reaction
vessel to cause the reactants to react spontaneously without
disrupting the surface of the molten reducing metal and then to
continue to react to completion without the benefit of externally
supplied heat or agitation.
By contrast, initiation of the process of the present invention is
characteristically induced at temperatures significantly below the
thermal initiation temperature. Thus, if one heats the reactants to
an initiation temperature as taught herein (i.e., significantly
below the thermal initiation temperature), and either does not
mechanically initiate the reduction reaction by intentionally
disrupting or proliferating the surface and body of the molten
metal, or inadequately manipulates the reactants in mechanically
initiating the reduction reaction, little or no reaction will occur
and the reaction will not proceed to completion.
Desirably, the temperature at which the process of the present
invention is initiated will be the minimum required to achieve an
acceptable rate of reaction when the surface of the molten reducing
metal is sharply disrupted in the presence of the reducible metal
compound. In the present invention the preferred temperature of
initiation is more than 100.degree. C. and usually more than
200.degree. C. below the thermal initiation temperature.
Frequently, a combination of reducible metal compound and reducing
metal can be selected so that there is a broad temperature range,
for example, several hundred centigrade degrees, over which the
reaction could be induced or mechanically initiated. However, once
initiated, the reducing reaction is exothermic and the temperature
will rise above the calculated thermal initiation temperature. With
this in mind, it is advantageous in the present invention to select
the lowest initiation temperature that meets many or all of the
following objectives:
a. The temperature should provide an acceptable rate of reaction
when the reaction is initiated;
b. The temperature should be at or above the boiling point of the
reducible metal compound; and
c. The temperature should be high enough to cause the exothermic
temperature reached during the reaction to be sufficient enough to
maintain the reduced metal and the by-product salt above their
melting points.
When using magnesium or sodium as the reducing metal, and using
titanium tetrachloride as the reducible metal compound, the thermal
initiation temperature for the reduction reaction is ordinarily in
excess of 600.degree. C. and thermally initiated reduction
processes, such as the Kroll process, are typically carried out
within the temperature range of from 700.degree.-850.degree. C. By
contrast, the present process can be carried out at temperatures as
low as the melting point of sodium (about 98.degree. C.). A very
useful initiation temperature for the present process, using sodium
metal as the reducing metal and titanium tetrachloride as the
reducible metal compound, is from 120.degree.-400.degree. C.
Initiating the Reaction
The reduction process of the present invention is initiated by
disrupting the surface of the molten reducing metal after it has
been heated to the temperature previously indicated. This can be
accomplished by abruptly shaking or jarring the reaction vessel or
zone, by rapid agitation of the reactants, or by any other means
which produces a sudden material change in the shape or area of the
surface of the molten metal which is exposed to or in contact with
the titanium tetrachloride.
Disrupting the surface of the molten metal results in a
proliferation or dispersion of freshly exposed reducing metal into
initmate contact with the reducible metal compound. this disruption
or proliferation of the molten metal serves to initiate the
reduction reaction in the present invention. Another way of viewing
this phenomenon is to consider that the thermal initiation
temperature under quiescent conditions, that is the "thermal
initiation temperature" of the prior art, is higher than the
initiation temperature under conditions wherein molten reducing
metal is being dispersed or proliferated as in the present
invention.
Although a variety of means can be used to disrupt or proliferate
the molten reducing metal, vertical agitation, that is agitation in
a direction perpendicular to the surface of the molten metal, is
much more effective than, for example, side to side shaking or
rotary mixing in vertically oriented cylindrical reaction vessels.
Thus, the direction of agitation can be important and should
ordinarily be performed in the direction or manner which results in
the best or most efficient proliferation of the molten reducing
metal. With cylindrical reaction vessels, agitation in the
direction of the axis is preferred. For example, end-on-end mixing
against the flattened ends of the reaction vessel is particularly
beneficial.
Once initiated, heat is produced by the reduction process and
desirably the external heat should be removed from the reactor and,
if necessary, cooling means should be provided for controlling the
temperature within the reaction zone.
Reaction Vessel and Related Equipment
The reaction vessel can take any of a variety of shapes. Apparatus
suitable for practicing this invention on a laboratory scale is
shown in the drawings.
In FIG. 1, a reaction pot or vessel, generally designated by the
numeral 1, is attached to a supporting arm 2 which is bolted to an
extension arm 3. Extension arm 3 extends over a block 4 which
serves as fulcrum. Block 4 rests on floor 5.
Reaction vessel 1 comprises a cylindrical body 6, the upper end of
which is closed. The open end of cylindrical body 6 is provided
with an outwardly extending annular flange 7 which is provided with
means, such as bolts, for fastening gasket 8 and cover 9 to
cylindrical body 6. Reaction vessel 1 is further adapted for
attachment to supporting arm 2.
The details of construction of reaction vessel 1 are shown more
clearly in FIG. 2.
In operation, the reaction vessel which in FIG. 1 is disassembled
and evacuated and/or purged with an inert gas, such as argon, as is
known in the art. Then, while operating within an inert atmosphere,
the reducing metal and the reducible metal compound, in
stoichiometric proportions, are placed in cylindrical shell 6 in
quantities sufficient to, for example, fill approximately 40-80
percent of the volume of reaction vessel 1. The reaction vessel is
then sealed by attaching the cover 9 to the cylindrical body 6 with
suitable bolts and a copper gasket 8. Reaction vessel 1 is then
attached to supporting arm 2. The contents of the reaction vessel 1
are then heated to the desired temperature. This heating can be
accomplished by various means including the use of a heating mantle
encircling the body of reaction vessel 1 and/or by means of a
heater placed between floor 5 and supporting arm 2 immediately
below reaction vessel 1. After the desired temperature has been
obtained, heating is discontinued.
Next, the reduction reaction is initiated by quickly or sharply
disrupting the surface of the molten metal within reaction vessel
1. Although various means can be used to accomplish this purpose, a
convenient laboratory method is to suddenly depress or rotate
extension arm 3 about fulcrum 4 one or more times in rapid
succession to provide sharp vertical agitation.
While not wishing to be bound by any theory, it has been observed
that a coating forms on the surface of the molten metal which is in
contact with the reducible metal compound and it is believed that
this coating or surface layer inhibits the reduction reaction until
either the temperature is raised high enough to thermally initiate
the reaction, for example, by causing the molten metal to boil, or
until the surface of the molten metal is sharply disrupted to
thereby expose fresh molten metal. By initiating the reaction in
the latter manner, such as by mechanically disrupting the surface
of the molten metal, the reaction can be started at a lower
temperature and the enormous pressures associated with the prior
art processes can be avoided. In the case of reducible compounds of
polyvalent metals, this may be the result of a shift in the
reaction mechanism and/or the reaction kinetics.
For example, once the reaction between titanium tetrachloride and
sodium is initiated by disrputing or proliferating the surface of
the molten sodium, the reaction proceeds spontaneously. The
reaction is exothermic and it has been observed that some or all of
the reaction vessel 1 will take on a red glow as the reaction
proceeds. With small reaction vessels up to 10 liter capacity, the
reduction reaction can be allowed to proceed without external heat
and without external cooling means. After the reaction has
completed, the reaction vessel and its contents can then be
permitted to cool to room temperature. The reaction vessel is then
detached from supporting arm 2 and cover 9 is removed. The interior
of the reaction vessel 1 will typically appear as shown in FIG. 2.
At the bottom of reaction vessel 1 will be a disc or plaque 10 of
titanium metal. Above this will be a salt deposit 11 of sodium
chloride. The top and side walls of cylindrical body 6 will be
covered with a thin layer of material 12 which may be salt, excess
sodium metal, and small particles or nodules of titanium which
adhere to the reactor walls.
It has been found that although small particles of titanium have
been found along the upper side walls and top of reaction vessel 1,
there are very few readily identifiable titanium particles within
salt block 11. Excess sodium, when present, tends to deposit along
the top wall or upper end of reaction vessel 1. For some reason,
the titanium nodules or particles which are sometimes found along
the upper walls of reaction vessel 1, within deposit layer 12 are
more ductile or softer than the titanium disc or plug 10.
The present invention is further illustrated by the following
specific examples which evidence the applicability of the present
invention to reducible metal compounds of titanium, zirconium,
hafnium uranium, vanadium, niobium, thorium, beryllium, and
molybdenum. As can be seen from the following examples, the process
of the present invention is particularly useful in the production
of titanium, zirconium, hafnium, uranium, vanadium, niobium and
thorium from reducible halide compounds of these metals.
Unless otherwise indicated in the following examples, all parts and
percentages are by weight.
EXAMPLE 1
This example illustrates the improved reduction process of this
invention using titanium tetrachloride as the reducible metal
compound and sodium as the reducing metal. It further illustrates
how other metals (such as copper) can be placed in the reaction
zone to be melted and combined with or alloyed with the metal being
produced by the reduction process.
The apparatus used in this example was of the type shown in FIG. 1.
The reaction vessel was constructed from a section of a mild steel
casing approximately 3/8 inch thick. A 3/8 inch steel plate was
welded across one end of the casing and an annular 3/4 inch steel
flange was welded to the opposite end of the casing to provide a
reaction vessel of the configuration shown in FIGS. 1 and 2. The
interior dimensions of this reaction vessel were 6 inches in
diameter and 8 inches high. A steel cover was made from 3/4 inch
steel. 510 grams of sodium metal from a sodium brick and 615 ml. of
titanium tetrachloride were placed in the reaction vessel after
first inverting it. A solid copper gasket (0.05 inches thick) was
placed over the flange and the cover plate was then bolted to the
flange using eight equally spaced 5/8 inch bolts. The gasket was
disc-shaped and was within the inside bolt circle. Consequently,
much of the gasket was exposed to the contents of the reaction
vessel.
Next, the sealed reaction vessel was heated in an oven for
approximately 2-3 hours until the temperature of the reaction
vessel reached approximately 175.degree. C.
The reaction vessel was then removed from the oven and immediately
attached to a steel supporting arm. A wooden plank approximately 10
feet long was used as the extension arm. A block of wood nominally
4 inches by 6 inches in cross sections was used as the fulcrum. The
surface of the molten sodium was sharply disrupted by rapidly
depressing the left end of extension arm 3 as shown in FIG. 1
several times in rapid succession. The movement of the extension
arm about the fulcrum was sufficient to cause the reaction vessel
to rise approximately 6-8 inches from the floor before falling back
to the floor. This sharp agitation was sufficient to initiate the
reduction process.
Shortly after the reaction was initiated, the lower one-third of
the reaction vessel became red. The vessel was set level and the
reaction was immediate and complete. After completion of the
reaction, the reaction vessel was permitted to cool to room
temperature. The reaction vessel was then removed from its
supporting arm, inverted and opened. The contents of the reaction
vessel were substantially identical to that shown in FIG. 2.
A well consolidated lump of titanium metal and copper, as
hereinafter explained, weighing approximately 128 grams was
obtained from the bottom of the reaction vessel. See FIG. 2,
element 10. 791 grams of sodium chloride crystals, containing no
discernible particulate metal were removed from the reactor. See
element 11 of FIG. 2. The outside of the reactor was pounded with a
mallet to loosen material which had adhered to the inner walls of
the reaction vessel. In this manner, 526 grams of a mixture of
small nodules and particles of ductile metal admixed with sodium
chloride particles, were recovered. Of this amount, 197 grams were
titanium. Very little material remained within the reaction
vessel.
Essentially no un-reacted sodium or titanium tetrachloride was
found in the reaction vessel.
Total metal recovery (as the lump and as small nodules) was in
excess of the theoretical yield of titanium metal. Subsequent
examination of the reaction vessel and of the titanium plaque
revealed that a portion of the copper gasket which was exposed to
the interior of the reaction vessel had melted during the reaction
and was co-mingled or alloyed with the titanium metal that was
recovered from the cover of the reaction vessel.
The estimated temperature range at which the reaction would be
initiated by only heating, the thermal initiation temperature, is
from 500.degree. to 600.degree. C. The reaction is this Example was
initiated at about 175.degree. C.
EXAMPLE 2
In this example, titanium metal was again produced from titanium
tetrachloride using sodium as the reducing metal.
The experimental apparatus of Example 1 was modified to the extent
that the cover 9 was welded to the body of the reaction vessel
after it was loaded with the reactants.
In Example 2, the reaction vessel was loaded with 1.8 Kg. of sodium
in the form of two commercial two pound sodium bricks each
measuring approximately 8 inches by 2 1/2 inches by 2 1/2 inches. A
stoichiometric amount (2,190 ml.) of titanium tetrachloride was
then added and the reaction vessel was sealed. It was then attached
to the supporting arm. The contents of the reaction vessel were
heated over a period of several hours until the temperature as
measured externally along the top of the reaction vessel had
reached approximately 180.degree. C. Heating was accomplished by
lifting the reaction vessel from the floor sufficiently high to
permit an electric heating element to be placed on the floor
underneath the reaction vessel. An electric heating element or
mantle was also placed around the reaction vessel. A cover of
insulating board was then placed over the reaction vessel to
prevent massive heat losses. When the temperature reached
approximately 180.degree. C., the heating elements and insulated
cover were removed. The contents of the reaction vessel were then
agitated by rapidly raising the reaction vessel about 8 inches from
the floor (using the extension arm for this purpose) and allowing
it to drop under its own weight. This procedure was repeated three
times in rapid succession, that is, in less than 5 seconds. The
reaction between the molten sodium and the titanium tetrachloride
was thereby initiated and immediately the lower one-half of the
reaction vessel turned red. The reaction was immediate and
complete. After the completion of the reaction, the reaction vessel
was allowed to cool to room temperature as the reaction subsided.
After the reaction vessel had cooled to substantially room
temperature, the reaction vessel was opened and the contents
appeared substantially as shown in FIG. 2.
425 grams of titanium metal was recovered in a consolidated mass or
lump. See element 10 of FIG. 2. This represents approximately 44
percent of the theoretical yield of titanium metal. In addition to
this consolidated mass of titanium metal, nodules of titanium metal
were found along the upper side walls of the reaction vessel and
along the top of the reaction vessel. The combined weight of these
nodules and the lump was in excess of 95 percent of the theoretical
yield of titanium.
The nodules of titanium metal attached loosely to the wall were
substantially softer than the consolidated mass of titanium found
in the bottom of the reaction vessel. No discernible particles of
titanium metal were found in the crystalline mass of sodium
chloride which was located immediately above the lump of titanium.
See element 11 of FIG. 2.
The estimated temperature range at which this reaction would be
initiated by only heating, the thermal initiation temperature, is
from 500.degree. to 600.degree. C. The reaction in this Example was
initiated at about 180.degree. C.
EXAMPLE 3
In this Example, titanium metal was produced from titanium
tetrachloride using a mixture of sodium and calcium as the reducing
metal.
In this embodiment 100 ml. of titanium tetrachloride, 61 grams of
sodium and 21.5 grams of calcium were placed in the 300 ml.
reactor. The reactor was sealed and heated in an oil bath to an oil
bath temperature of 230.degree. C. Upon shaking of the reactor at
this temperature, a very vigorous reaction occurred. After the
completion of the reaction 41.56 grams of titanium were recovered
for a yield of 95.4 percent. The reduction reaction of this Example
was initiated at 230.degree. C., whereas the thermal initiation
temperature for this reaction lies in the range from 500.degree. to
600.degree. C.
EXAMPLE 4
In this Example, titanium metal was produced from titanium
tetrachloride using a mixture of sodium and barium as the reducing
metal.
In this embodiment of the present invention, 100 ml. of titanium
tetrachloride, 45 grams of sodium, and 125 grams of barium were
placed in the 300 ml. reactor. The reactor was then shaken for
about 60 seconds, which shaking produced a very vigorous reaction.
After the completion of the reaction, 43.08 grams of titanium were
recovered for a yield of 98.8 percent.
The reduction reaction of this Example was initiated at 230.degree.
C., whereas the thermal initiation temperature for this reaction
lies in the range of from 500.degree. to 600.degree. C.
EXAMPLE 5
In this Example, an alloy of titanium and tin is produced from a
mixture of SnCl.sub.4 and TiCl.sub.4 using sodium as the reducing
metal.
In this embodiment, 5 ml. of SnCl.sub.4 and 95 ml. of TiCl.sub.4
were placed in the 500 ml. reactor with 85 grams sodium. The
reactor was put in an oil bath which was heated to 160.degree. C.
and held at from 140.degree. to 160.degree. C. for 40 minutes. The
reactor was then shaken end to end in a laboratory hydrogenation
shaker for 20 seconds. It was noticed that immediately after the
start of the shaking the residual oil smoked and the bottom of the
reactor became red hot. After completion of the reaction, 45 grams
of powder and nodules were recovered for a yield of 97 percent. In
a subsequent laboratory investigation, the recovered material was
found to be an alloy of 90 percent titanium and 10 percent tin.
The reduction reaction of this Example was initiated at from
140.degree. to 160.degree. C., whereas the thermal initiation
temperature for this reaction lies in the range of from 500.degree.
to 600.degree. C.
EXAMPLE 6
In this Example, titanium was produced from titanium tetrabromide
using sodium as the reducing metal.
In this embodiment, 105.4 grams of TiBr.sub.4 and 28 grams of
sodium were placed in the 300 ml. reactor and sealed with a copper
gasket as well as an eight bolt flange. The sealed reactor was
heated in an oil bath at a bath temperature in the range of from
208.degree. to 230.degree. C. for a period of 25 minutes. The
disruption of the reducing metal surface was accomplished by
shaking the reactor in a laboratory shaker for 20 seconds. Upon
completion of the reaction, 14.0 grams of powder, lumps, and
spherules were recovered. Since all the sodium was reacted, this
was used as a basis for a 100 percent theoretical yield of 14.58
grams of titanium metal. Accordingly, the actual yield was 96
percent of the theoretical yield.
The reduction reaction of this Example was initiated at a
temperature in the range of from 208.degree. to 320.degree. C.,
whereas the thermal initiation temperature for the reaction lies in
the range of from 500.degree. to 600.degree. C.
EXAMPLE 7
In this Example, titanium metal was produced from titanium
tetrafluoride using sodium as the reducing metal.
In this embodiment, 108.6 grams of TiF.sub.4 and 81.6 grams sodium
were placed in a 300 ml. cylindrical reactor which was sealed with
a solid copper gasket which was, in turn, secured by a bolted blank
flange. The reactor was then placed in an oil bath which was heated
in the range of from 225.degree. to 240.degree. 25 C. for
251minutes after which the reactor was shaken for 60 seconds. 18
seconds after the start of the shaking, the residual oil left on
the outside of the reactor began smoking, thereby indicating that
the reaction had been initiated. Upon the realization that only a
partial reaction had taken place, the reactor was again heated in
asalt bath at a final temperature of 385.degree. C. No indication
of a further reaction was noted, nor did additional shaking give
any evidence of a further reaction.
After the reactor was opened, the reactor was heat-soaked for 4 1/2
hours at from 760.degree.-790.degree. C. in a crucible furnace.
After extensive leaching of the end-product in isopropyl alcohol to
kill the residual sodium, followed by a water and a concentrated
nitric acid treatment to remove the residual fluoride, 17.8 grams
of powdered and granular titanium were recovered for a recovery of
42.5 percent of the theoretical amount.
The relatively low recovery is believed to be caused by the lumpy
and powdered nature of the TiF.sub.4 starting material which was
hydroscopic and which possessed an inherently low heat of reaction,
certainly lower than that for the reduction of the bromide or
chloride of titanium.
Nonetheless, titanium was recovered in appreciable amounts from the
TiF.sub.4 starting material in accordance with the procedure of
this invention. The reduction reaction of this Example was
initiated at from 225.degree. to 240.degree. C., whereas the
thermal initiation temperature is from 500.degree. to 700.degree.
C.
EXAMPLE 8
In this Example, zirconium metal was produced from zirconium
tetrachloride using sodium as the reducing metal.
A large reactor was charged with about 9 kilograms of zirconium
tetrachloride powder before the contents of the reactor were
evacuated through an opening therein; such as, for example, a 3/8
inch nipple welded into the middle of one side of the reactor. A
vacuum of 682 mm. (Hg) was maintained over a period of 5 hours
during which time argon was admitted twice to encourage the removal
of HCl and other gases. After a final addition of argon, the nipple
was sealed off and the reactor was heated over a gas flame to a
temperature on the top of the reactor of about 450.degree. to
470.degree. F. then the reactor was shaken end on end for a period
of 70 seconds. After 40 seconds, the reactor was red over most of
its area indicating that the reduction reaction was taking
place.
After the completion of the reduction reaction, the reactor was
opened and the contents thereof examined. The contents consisted of
a large amount of salt (NaCl) substantially free of zirconium
metal, and porous fused zirconium metal lying along the side of the
reactor. Almost 70 kilograms of salt were segregated. The metal and
the remaining salts were leached with isopropyl alcohol to remove
traces of sodium, then sequentially with 0.1N HCl, 1N H.sub.2
SO.sub.4, water and finally methyl alcohol. The yield of coarse
zirconium metal was 7,569 grams for a recovery of 85 percent while
the yield of fine zirconium metal amounted to 1,240 grams or 14
percent, for a total yield of 99 percent of the theoretical
yield.
The reduction reaction of this Example was initiated at about
470.degree. F., whereas the thermal initiation temperature for this
reduction reaction is in the range of from 500.degree. to
600.degree. C.
EXAMPLE 9
In this Example, zirconium metal was produced from zirconium
tetrachloride using a mixture of sodium and calcium as the reducing
metal.
In this embodiment, 55.5 grams (0.238 moles) of zirconium
tetrachloride powder, 12 grams (0.522 moles) of clean sodium and 10
grams (0.250 moles) of calcium were placed in a 300 ml. reactor.
The reactor was closed with a solid copper gasket and an eight bolt
blank flange as in Example 1 before the reactor was immersed in a
mineral oil bath where the oil was held for 25 minutes at from
230.degree. to 235.degree. C. Immediately thereafter, the reactor
was shaken vigorously for 20 seconds resulting in a pronounced
smoking of the residual oil on the reactor surface after about 6
seconds. This smoking was considered as an indication that an
exothermic reaction had been initiated shortly after the start of
the agitation.
The resulting reaction mixture was treated with excess isopropyl
alcohol to destroy the unreacted sodium and calcium. The alcohol
was increasingly diluted with water as the hydrogen evolution
subsided. After heating the residue on the steam bath for 4 hours
with concentrated HNO.sub.3, the yield was 20.7 grams (95.4 percent
recovery) of a black powder and sponge mixture of zirconium.
The reduction reaction of this Example was initiated in the
temperature range of from 230.degree. to 235.degree. C., whereas
the thermal initiation temperature is from 500.degree. to
600.degree. C.
EXAMPLE 10
In this Example, vanadium was produced from vanadium tetrachloride
using sodium as the reducing metal.
In this embodiment, 77 ml. of VCl.sub.4 (containing some VCl.sub.3
contaminant) was placed in a 300 ml. reactor with 70 grams of
sodium. The reactor was immersed in an oil bath which was heated to
145.degree. C. and held in a temperature range of from 140.degree.
to 163.degree. C. for 27 minutes. The reactor was then shaken for
about 23 seconds, during which shaking, smoke became evident and
the bottom of the reactor became red hot. After leaching in 1/8N
HCl overnight, 32.7 grams of vanadium powder and vanadium nodules
were recovered for a yield of 86.7 percent.
The reduction reaction in this Example was initiated in the
temperature range of from 140.degree. to 163.degree. C., whereas
the thermal initiation temperature for this reaction is from
500.degree. to 600.degree. C.
EXAMPLE 11
In this Example, niobium was produced from niobium pentachloride
using sodium as the reducing metal.
In this embodiment, 100 grams of NbCl.sub.5 and 41.7 grams of
sodium were placed in the 300 ml. reactor and sealed with a solid
copper gasket and a bolted flange. The reactor was then placed in
an oil bath heated in the temperature range of from 225.degree. to
230.degree. C. for 22 minutes after which the reactor was removed
from the bath and shaken for 60 seconds with no evidence of heat
development. The reactor was then placed in a salt bath and
reheated with the bath temperature rising continuously over a
period of 39 minutes from 229.degree. to 366.degree. C. After the
heat treatment in the salt bath, the reactor was shaken in the
laboratory shaker for 60 seconds during which time smoke appeared
(at 40 seconds) and the residual oil on the shaking sleeve caught
fire (at 60 seconds). After the completion of the reduction
reaction, 31.3 grams of fine black niobium powder and small niobium
metal particles were recovered. The recovery was 91 percent of the
theoretical value.
In this Example, the reduction reaction was initiated at under
366.degree. C., whereas the thermal initiation temperature is in
the range of from 500.degree. to 700.degree. C.
EXAMPLE 12
In this Example, beryllium is produced from BeCl.sub.2 using sodium
as the reducing metal.
In this Example, 50 grams of powdered, anhydrous beryllium chloride
and 30 grams of sodium were charged to the 300 ml. reactor and the
reactor was heated in an oil bath to a temperature of 230.degree.
C. Thereafter, the reactor was shaken for 30 seconds and vigorous
reaction resulted. Upon the completion of the reaction 2.9 grams of
beryllium were recovered for a yield of 52 percent.
This reduction reaction was initiated at 230.degree. C., whereas
the estimated thermal initiation temperature is from 500.degree. to
600.degree. C.
EXAMPLE 13
In this Example, molybdenum was produced from molybdenum sulphide
using lithium as the reducing metal.
In this embodiment, a quantity of MoS.sub.2 (natural molybdenite)
was ground to -150 mesh and heated under vacuum for several hours.
30.8 grams of this treated molybdenite and 8.6 grams of lithium
were placed in the 300 ml. reactor and heated to an oil bath
temperature slightly in excess of 230.degree. C. Upon end to end
agitation in a laboratory shaker, a moderate reaction occurred.
After cooling, 15.6 grams of molybdenum were recovered for a yield
of 85 percent.
This reduction reaction was initiated at about 230.degree. C,
whereas the thermal initiation temperature for this reaction is in
the range of from 500.degree. to 700.degree. C.
The following is a brief discussion of some other exemplary metals
which may be produced by the procedure of the present
invention.
Hafnium can be produced in the same manner as zirconium, see
Examples 8 and 9 above, by treating hafnium tetrachloride with
sodium or a sodium mixture as the reducing metal. The following
data taken from Metallurgical Thermochemistry; Kubaschewski, Evans,
and Alcock; Pergamon Press; Third Edition (1967), shows the
similarities between the important properties of zirconium
tetrachloride and hafnium tetrachloride essential to the
performance of this invention:
HfCl.sub.4 ZrCl.sub.4 Boiling Point 316.degree.C. (sublimes)
331.degree.C. (sublimes) Melting Point 437.degree.C. 432.degree.C.
Heat of Formation -236.7 Kcal. -234.7 Kcal.
Uranium can be produced by the reduction of UF.sub.6 with a sodium
reducing metal according to the procedure of this invention, since
the heat of reaction for UF.sub.6 + 6Na = U + 6NaF is -175.8 Kcal.
Further, UF.sub.6 melts at 64.degree. C. with a vapor pressure of
about 1.5 atmospheres and mixes quickly and completely with the
reducing metal at low temperatures of about 140.degree. to
240.degree. C. Further still, an USAEC Document (ORNL-3012, C. D.
Scott, May 24, 1961) clearly shows that UF.sub.6 and sodium react
when they are heated together.
Thorium has been produced by the thermally initiated reduction of
ThCl.sub.4 with sodium metal at a temperature of about 500.degree.
C. according to Z. anorg. allgem. Chem., C. Lely and L. Hamburger
at 87,209 (1914). Accordingly, it is evident from the preceding
Examples that the procedure of the present invention can produce
thorium at temperatures significantly below 500.degree. C.
Reducible metal compounds, other than the reducible metal halides,
may be used as a source of the metal to be recovered. See, for
instance, Example 13 above in which MoS.sub.2 is reduced by lithium
metal according to the procedure of the present invention. Further,
British Pat. Nos. 729,503 and 729,504 indicate that TiO.sub.2,
Li.sub.2 TiO.sub.3, V.sub.2 O.sub.5, Cb.sub.2 O.sub.5, Ta.sub.2
O.sub.5, Cr.sub.2 O.sub.3, MoO.sub.3, WO.sub.3, MnTe, FeS, and
U.sub.3 O.sub.8 may be reduced to form their respective metals.
Though the present invention has been illustrated above in a number
of specific examples, the procedure of this invention may obviously
be applied to reducible metal compounds not specifically mentioned
above in view of the broader aspects of this procedure.
* * * * *