U.S. patent application number 11/465180 was filed with the patent office on 2008-12-04 for cavitation process for products from precursor halides.
This patent application is currently assigned to GM Global Technology Operations, Inc.. Invention is credited to Michael P. Balogh, Michael K. Carpenter, Ion C. Halalay.
Application Number | 20080295645 11/465180 |
Document ID | / |
Family ID | 39082858 |
Filed Date | 2008-12-04 |
United States Patent
Application |
20080295645 |
Kind Code |
A1 |
Halalay; Ion C. ; et
al. |
December 4, 2008 |
CAVITATION PROCESS FOR PRODUCTS FROM PRECURSOR HALIDES
Abstract
A precursor halide compound is reduced to a predetermined
product at substantially ambient conditions. The halide is added to
an anhydrous liquid reaction medium containing one or more alkali
metals or alkaline earth metals as reductants. The metal reductants
are dispersed as very small globules in the liquid by cavitation of
the liquid, such as by application of high intensity ultrasonic
vibrations or high-shear mixing to the reaction vessel. Continued
cavitation of the liquid medium affects low temperature reduction
of the precursor halide(s) to produce a metal, metal alloy, metal
compound, ceramic material, metal matrix-ceramic composite
material, or the like. The practice may be applied, for example, to
titanium tetrachloride, alone or with other chlorides, to produce
titanium metal, titanium alloys (for example Ti-6Al-4V), and
titanium compounds (TiSi.sub.2).
Inventors: |
Halalay; Ion C.; (Grosse
Pointe, MI) ; Balogh; Michael P.; (Novi, MI) ;
Carpenter; Michael K.; (Troy, MI) |
Correspondence
Address: |
GENERAL MOTORS CORPORATION;LEGAL STAFF
MAIL CODE 482-C23-B21, P O BOX 300
DETROIT
MI
48265-3000
US
|
Assignee: |
GM Global Technology Operations,
Inc.
Detroit
MI
|
Family ID: |
39082858 |
Appl. No.: |
11/465180 |
Filed: |
August 17, 2006 |
Current U.S.
Class: |
75/345 ; 423/492;
423/71; 75/351 |
Current CPC
Class: |
B22F 9/24 20130101; Y10S
423/12 20130101 |
Class at
Publication: |
75/345 ; 75/351;
423/71; 423/492 |
International
Class: |
C22B 34/10 20060101
C22B034/10; B22F 9/24 20060101 B22F009/24 |
Claims
1. A method of reducing a least one precursor halide compound to
yield a predetermined product, the method comprising: circulating a
dry inert gas through an anhydrous liquid reaction medium and
inducing cavitation in the liquid reduction medium; and mixing at
least one precursor halide compound with a reductant composition in
the liquid reaction medium during the cavitation to reduce the
precursor halide compound(s) to the predetermined product, the
reductant composition consisting essentially of at least one of an
alkali metal and/or an alkaline earth metal(s), the reductant
composition being converted to the halide salt of the alkali metal
and/or alkaline earth metal upon reaction with the precursor halide
compound.
2. A method of reducing at least one precursor halide compound as
recited in claim 1 in which the liquid reaction medium is
maintained at a temperature in the range of about -80.degree. C. to
about 300.degree. C. during the cavitation and reduction of the
precursor halide(s) to the predetermined product.
3. A method of reducing at least one precursor halide compound as
recited in claim 1 in which the liquid reaction medium is initially
at ambient temperature.
4. A method of reducing at least one precursor halide compound as
recited in claim 1 in which the anhydrous liquid is a hydrocarbon
liquid, a liquid comprising a silicon-containing compound, or an
ionic liquid.
5. A method of reducing at least one precursor halide compound as
recited in claim 1 in which the anhydrous liquid is a hydrocarbon
liquid selected from the group consisting of decalin, tetralin,
decane, dodecane, and hexadecane.
6. A method of reducing at least one precursor halide compound as
recited in claim 1 in which the reductant composition consists
essentially of a mixture of sodium and potassium.
7. A method of reducing at least one precursor halide compound as
recited in claim 1 in which the reductant composition consists
essentially of a mixture of sodium and potassium that is liquid at
temperatures below about 30.degree. C.
8. A method of reducing at least one precursor halide compound as
recited in claim 1 in which the reductant compound is initially
dispersed in the liquid reaction medium and the precursor halide
compound is thereafter added to the liquid reaction medium.
9. A method of reducing at least one precursor halide compound as
recited in claim 1 in which the amount of liquid reaction medium is
predetermined based in the heat of reaction of the precursor halide
and the reductant material.
10. A method of reducing at least one precursor halide compound as
recited in claim 1 in which substantially stoichiometric
proportions of precursor halide(s) and reductant composition are
reacted.
11. A method of reducing at least one precursor halide compound as
recited in claim 1 in which inert gas is pumped through the liquid
reaction medium in a closed circuit path.
12. A method of reducing at least one precursor halide compound to
yield a predetermined product, the method comprising: forming a
reduction reaction medium for the precursor halide by dispersing a
reductant composition for the precursor halide in an anhydrous
liquid that is non-reactive with the reductant composition using
vibrations to affect cavitation in the liquid, the reductant
composition consisting essentially of at least one of an alkali
metal and/or alkaline earth metal; circulating a dry inert gas
through the reduction reaction medium to assist cavitation in the
medium and to return volatile material to the reduction reaction
medium; and, while continuing the vibrations, adding the at least
one precursor halide to the reaction medium to reduce the precursor
halide to the predetermined product and to concurrently form a
corresponding halide salt of the alkali metal and/or alkaline earth
metal(s).
13. A method of reducing at least one precursor halide compound as
recited in claim 12 in which the precursor halide compound(s) are
chloride(s).
14. A method of reducing at least one precursor halide compound as
recited in claim 12 in which the anhydrous liquid is a hydrocarbon
liquid, a liquid comprising a silicon-containing compound, or an
ionic liquid.
15. A method of reducing at least one precursor halide compound as
recited in claim 12 in which the anhydrous liquid is a hydrocarbon
liquid selected from the group consisting of decalin, tetralin,
decane, dodecane, and hexadecane.
16. A method of reducing at least one precursor halide compound as
recited in claim 12 in which the reductant composition consists
essentially of a mixture of sodium and potassium.
17. A method of reducing at least one precursor halide compound as
recited in claim 12 in which the reductant composition consists
essentially of a mixture of sodium and potassium that is liquid at
temperatures below about 30.degree. C.
18. A method of reducing at least one precursor halide compound as
recited in claim 12 in which the liquid reaction medium is
maintained at a temperature in the range of about -80.degree. C. to
about 300.degree. C. during the cavitation and reduction of the
precursor halide(s) to the predetermined product.
19. A method of reducing at least one precursor halide compound as
recited in claim 12 in which substantially stoichiometric
proportions of precursor halide(s) and reductant composition are
reacted.
20. A method of reducing at least one precursor halide compound as
recited in claim 12 in which the precursor halide(s) is a chloride
compound(s) and the predetermined product is one of titanium
powder, titanium disilicide powder, platinum zirconium powder, or
zirconium powder.
Description
TECHNICAL FIELD
[0001] This invention pertains to substantially ambient temperature
preparation of metals, metal alloys and compounds, ceramic
materials, and metal matrix-ceramic composite materials from
hydride precursors in an anhydrous liquid medium using cavitation
processing. Suitable alkali or alkaline earth metals may be
dispersed by cavitation in the liquid medium for reduction of
precursor halides. For example, titanium and titanium alloys and
compounds, platinum alloys and transition metal silicides may be
prepared. In an illustrative example, the practice pertains to the
addition of titanium chloride or mixtures of titanium chloride with
other precursor halides to a cavitated liquid containing the
reductant material to produce titanium metal or titanium alloys or
compounds.
BACKGROUND OF THE INVENTION
[0002] Titanium and its metal alloys are examples of materials that
currently are relatively expensive to produce. Titanium alloys can
be used in forms such as castings, forgings, and sheets for
preparing articles of manufacture. Titanium based materials can be
formulated to provide a combination of good strength properties
with relatively low weight. For example, titanium alloys are used
in the manufacture of airplanes. But the usage of titanium alloys
in automotive vehicles has been limited because of the cost of
titanium compared to ferrous alloys and aluminum alloys with
competitive properties.
[0003] Titanium-containing ores are beneficiated to obtain a
suitable concentration of TiO.sub.2. In a Chloride Process the
titanium dioxide (often the rutile crystal form) is chlorinated in
a fluidized-bed reactor in the presence of coke (carbon) to produce
titanium tetrachloride (TiCl.sub.4), a volatile liquid at room
temperature. Traditionally, metallic titanium was produced in batch
processes from the high temperature reduction of titanium
tetrachloride (TiCl.sub.4) with sodium or magnesium metal. Pure
metallic titanium (99.9%) was first prepared in 1910 by Matthew A.
Hunter by heating TiCl.sub.4 with sodium in a steel bomb at
700-800.degree. C. The first, and still the most widely used,
process for producing titanium metal on an industrial scale is the
Kroll Process. In the Kroll Process, magnesium at 800.degree. C. to
900.degree. C. is used as the reductant for TiCl.sub.4 vapor and
magnesium chloride is produced as the byproduct. Both of these
processes produce titanium sponge and necessitate repetitive energy
intensive vacuum arc remelting steps for purification of the
titanium. These processes can be used for the co-production of
titanium and one or more another metals (an alloy) when the
alloying constituent can be introduced in the form of a suitable
chloride salt (or other suitable halide salt) that undergoes the
sodium or magnesium reduction reaction with the titanium
tetrachloride vapor. These high temperature and energy-consuming
processes yield good quality titanium metal and metal alloys but,
as stated, these titanium materials are too expensive for many
applications such as in components for automotive vehicles.
[0004] The Armstrong/ITP process also uses alkali metals or
alkaline earth metals to reduce metal halides in the production of
metals. The Armstrong process can run at lower temperatures and can
operate as a continuous process for producing a metal or metal
alloy (such as titanium or titanium alloy) powder. However, the
projected cost of the metal is still high, too high for many
automotive applications.
[0005] A lower cost process is needed for the production of
titanium and titanium alloys and compounds. It would be
particularly beneficial if a lower cost process could be provided
that had applicability to other metals and their alloys and
compounds.
SUMMARY OF THE INVENTION
[0006] Titanium metal (as an example) may be produced by reduction
of a titanium halide (for example, titanium tetrachloride) with a
reductant metal in a liquid reaction medium at close-to-ambient
temperatures and at close-to-atmospheric pressure. The reduction of
the precursor halide in the reaction medium is assisted using
suitable cavitation practices, for example a sonochemical process
or high-shear mixing. The process may also be used to
simultaneously reduce other precursor halides with a titanium
halide to produce alloys or compounds of titanium or titanium metal
matrix composite materials. Further, the process may be used to
produce many other materials in many forms depending on the
selection of the precursor halide or combinations of precursor
halides.
[0007] The reaction medium is an anhydrous, suitably low vapor
pressure liquid that is not reactive with the precursor halide(s)
or the reductant metal(s). Anhydrous liquid hydrocarbons such as
decalin, tetralin, decane, dodecane, and hexadecane are examples of
suitable reaction medium materials. Liquid silicon-containing oils,
such as polydimethylsilanes, and room temperature ionic liquids are
also examples of suitable reaction medium materials. The liquid
medium may be infused or covered with dry and substantially
oxygen-free and water-free inert gas such as helium or argon to
provide an inert atmosphere during processing.
[0008] The reductant for the precursor halide(s) is suitably one or
more of the alkali or alkaline earth metals such as lithium,
sodium, potassium, rubidium, cesium, magnesium, calcium, and
barium. A preferred reductant is a low-melting point mixture of the
reactants that can be dispersed, by application of ultrasonic
vibrations to the liquid, as colloidal bodies in the liquid medium
at a near-to-ambient temperature. For example, eutectic mixtures of
sodium and potassium, such as Na.sub.0.22K.sub.0.78 and
Na.sub.0.44K.sub.0.56 are liquid at about room temperature and are
effective reductants for precursor halides. One or more precursor
halides, such as titanium tetrachloride, are then added to the
reaction medium, with its dispersed reductants, and reduced to a
predetermined product. When the precursor halide(s) includes a
titanium halide the product may, for example, may be titanium metal
or a mixture of titanium and other metals, or titanium containing
alloy or a titanium compound.
[0009] The process uses cavitation processes (preferably
sonochemical practices) to disperse the reductant material in the
liquid medium and to promote the reduction of the precursor
halides. A suitable vessel containing the liquid medium is
subjected to ultrasonic vibrations, using a transducer that
generates sound waves in the liquid at a frequency usually greater
than about 20 kilohertz. The sonic energy causes the repeated
formation, growth, and collapse of tiny bubbles within the liquid,
generating localized centers of very high temperature and pressure,
with extremely rapid cooling rates to the bulk liquid. It is
preferred that the liquid medium have a relatively low vapor
pressure at processing temperatures so that the medium contributes
little vapor to the high temperature regions in the cavitation
bubbles. Meanwhile, the introduction of the inert gas into the
liquid facilitates the formation of the cavitation bubbles with
small atoms that will not be reactive at the high temperature in
the bubbles.
[0010] This cavitation processing first disperses the reductant
metal in the hydrocarbon liquid and then promotes the reaction of
the reducing metal with the precursor halide(s) when they are
brought into contact with the liquid. The reduced halide yields
particles of metal, metal alloy, metal compound, metal matrix
ceramic composite, or the like, depending on the composition of the
halide starting materials (of course, when the precursor halide is,
or contains, a non-metal such as carbon tetrachloride or silicon
tetrachloride, the product then may be a non-metal). The metal
content of the reducing medium is oxidized to a corresponding
alkali metal or alkaline earth metal halide salt(s). The reaction
usually proceeds over a period of minutes to several hours and
usually provides an essentially quantitative yield of the metal
constituents of the halide(s) being treated.
[0011] Thus, as an example, titanium tetrachloride liquid is passed
into hexadecane containing finely dispersed Na.sub.0.22K.sub.0.78
and the products are titanium metal, sodium chloride, and potassium
chloride.
[0012] The solids are separated from the reaction medium and the
salt is separated from the metal product (or other predetermined
product). The temperature of the liquid medium increases somewhat
from an ambient starting temperature, but typically only to a
temperature of the order of 60.degree. C. to about 100.degree. C.
The reaction may be conducted as a batch process or on a continuous
basis.
[0013] Examples of products of this process using, for example,
titanium-containing halide vapor include titanium metal, mixtures
of titanium with other metals for alloy formation such as aluminum
and/or vanadium, and titanium compounds such as titanium silicide
(TiSi.sub.2). Other metals such as platinum and zirconium may be
produced along with their alloys and compounds. Non-metal halide
precursors such as carbon tetrachloride or silicon tetrachloride
may be used in the process. The products are often produced
initially as very small particles. Often the product is amorphous
or of very small crystal size.
[0014] An obvious advantage of this practice for producing, for
example, metals, metal alloys and metallic compounds,
inter-metallic compounds metal matrix ceramic composites, and the
like is that the process may be conducted at temperatures that are
close to ambient temperatures and with relatively low consumption
of energy.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a flow diagram illustrating an embodiment of the
invention as it is applied to the production of titanium metal
starting with titanium tetrachloride as the halide precursor.
[0016] FIG. 2 is a schematic illustration of apparatus for the
sonochemical reduction of titanium chloride using a mixture of
sodium and potassium dispersed in a hydrocarbon liquid.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0017] This invention utilizes sonochemistry to promote the
reduction of precursor halides to useful products such as metals,
metal alloys, compounds, ceramics, mixtures, and metal matrix
ceramics composites. In the practice of sonochemistry, liquids are
subjected to high intensity sound or ultrasound (sonic frequencies
above twenty kilohertz, above the range of human hearing). The
liquid is contained in a suitable vessel that is actuated by one or
more ultrasonic transducers or the like. Each transducer converts
alternating current energy above twenty kilohertz to mechanical
vibrations of about the same frequency. The transducer usually
utilizes a magnetostrictive or piezoelectric material to convert
alternating current to mechanical vibrations.
[0018] When ultrasonic vibrations of suitable intensity are
applied, the energy is transmitted through the walls of the vessel
to the liquid. The ultrasonic energy causes the repeated formation,
growth, and collapse of tiny cavitation bubbles within the liquid,
generating localized centers of very high temperature and pressure,
with extremely high cooling rates to the bulk liquid. It is
estimated that the local temperature and pressure within the
bubbles can reach 5000K and two kilobars, respectively. Ultrasound
propagates by a series of compressions and rarefactions induced in
the liquid medium through which it passes. At sufficiently high
power, the forces generated during the rarefaction cycles exceed
the attractive forces between the molecules of the liquid and
cavitation bubbles will form. The bubbles will then grow during
subsequent acoustic cycles by a process known as rectified
diffusion, i.e. small amounts of vapor and gas from the medium
enter the bubble during its expansion phase and are not fully
expelled during compression. The bubbles grow until they reach an
unstable size, then collapse during a succeeding compression (i.e.
acoustic half-cycle), with the release of energy for chemical and
mechanical effects. The spherical bubble or vapor cavity may have a
diameter of about 0.2 to about 200 micrometers and experience a
momentary temperature of about 5000K. The vapor cavity is enclosed
by a liquid shell which, in turn, is immersed in the bulk liquid.
The liquid shell may have a thickness of about 0.02 to about 2
micrometers and a momentary temperature of about 2,000K. The bulk
liquid may be gradually heated by the sonochemical activity.
Assuming that the bulk liquid is initially at a low temperature of,
e.g., 298K, it may reach a temperature of up to 670K during
prolonged sonochemical processing.
[0019] Chemical reactions can occur in two distinct regions of the
medium: (1) inside the vapor cavity, i.e. the bubble proper, and
(2) inside the hot liquid shell surrounding which surrounds the
bubble. The narrow width of the hot liquid shell and the large
temperature difference between the vapor cavity and surrounding
liquid (order of 5,000 K) lead to extremely steep temperature
gradients, which in turn translate into cooling rates of the order
of 10.sup.9 K/s. Such conditions will lead to the formation of
metastable--sometimes amorphous--metals, alloys and compounds.
[0020] The chemical reduction of metal chlorides with alkali metals
and magnesium has been practiced at very high temperatures, for
example in the commercial production of titanium metal. But this
invention permits the reduction of suitable precursor halides at
lower temperatures than traditionally used for the synthesis of a
particular product. In the practice of this invention sonochemistry
is used to promote the reduction of precursor halides in an inert,
anhydrous liquid reaction medium. Preferably, the reaction medium
is a low vapor pressure anhydrous hydrocarbon, such as decalin,
tetralin, decane, dodecane, and hexadecane. Some of these liquids
have a melting point well below 0.degree. C. and a boiling point
well above 100.degree. C. Thus they provide a broad temperature
range as a reaction medium below and above typical ambient
temperatures. Low vapor pressure is preferred so as to minimize the
presence of vapor from the liquid reaction medium in the cavitation
bubbles. For some embodiments hydrocarbons such as xylene and
toluene with moderate vapor pressure may also be suitable. The
water content of the anhydrous liquid reaction medium is suitably
less than 100 ppm, preferably below 10 ppm.
[0021] The reduction of a precursor chloride by an alkali or
alkali-earth metal to form a desired element (or combination of
elements) and alkali metal or alkali-earth metal chlorides proceeds
exothermically. The heat released in a given reaction for a given
amount of precursors can be determined through thermochemical
calculations. In the case of batch processing, the amount of liquid
reaction medium (sometimes a solvent) needed for the reaction is
determined from the heat released in the reaction and from the
specific heat of the liquid used as reaction medium. Typically, one
chooses an amount of liquid so that the temperature increase at the
end of the reaction does not exceed a predetermined temperature
limit deemed to be safe or desirable. This procedure can be adapted
for continuous processing, provided that the reaction apparatus is
equipped with a heat exchanger. In this case one must choose a
precursor addition rate such that the heat release rate during the
reduction reaction(s) is balanced by the heat removal rate of the
heat exchanger.
[0022] In general, it may be preferred to start a practice of the
process with the reaction medium at ambient temperature or near to
ambient temperature. It is found that dispersion of the alkali or
alkali-earth metal reductants in the reaction medium, with the aid
of ultrasound (or other cavitation method) causes the temperature
of the medium to rise, typically by 10.degree. C. to 30.degree. C.,
above its initial temperature. Addition of the precursor halides,
under cavitating conditions, causes the temperature in the reaction
vessel to increase steadily, so that the temperature of the
reaction medium at the end of the reaction reaches typically to a
temperature between 70.degree. C. to 100.degree. C. Several
specific examples of the practice of the invention are described
below. In these examples of relatively small reaction volumes, no
attempt was made to control the temperature of the reaction medium
as it increased from room temperature. However, controlling the
average temperature of the reaction medium may be desirable or
necessary when the goal is to achieve a predetermined particle size
and/or morphology for the product. Typically, low average reaction
medium temperatures will yield smaller product particles which are
generally characterized by a relatively high specific surface area
and relatively high chemical reactivity. When formed in a
relatively low temperature reaction medium the particles may be
amorphous or have a very fine crystal structure. On the other hand
relatively high average reaction medium temperatures favor the
formation of larger particles with a lower specific surface area
and lower chemical reactivity. These higher temperature reaction
conditions sometimes produce crystalline products and in the form
of aggregated particles. A suitable temperature may be chosen, for
example from about -80.degree. C. to about 300.degree. C.
[0023] Besides the temperature of the reaction medium, the power
input per unit area is another factor that determines product
particle size and morphology. Input power per unit area is also a
cost determining parameter. Should a given particle size and
morphology be the desired outcome of the reaction, then both the
reaction temperature and input power must be adjusted to achieve
this goal (after choosing a suitable solvent or reaction medium).
However, if a low cost is desired, then one would like to operate
close to the threshold power for the reaction(s). This threshold
power may be determined experimentally, by running successive
reactions at decreasing power levels, until the reaction stops or
the overall processing time is unacceptably long. The ultrasonic
energy input is of low or moderate level.
[0024] In the example of the reduction of titanium tetrachloride at
laboratory scale as described below in this specification, the
energy level of the transducer was 0.25 W/cm.sup.2 of
transducer-engaged surface of the reaction flask or vessel.
[0025] The sonochemical reaction is practiced using continuous
infusion or sparging of the reaction medium with an inert gas,
suitably helium or argon. The inert gas promotes cavitation and
provides a protective blanket for the liquid reaction medium. To
the extent that atoms or molecules of the inert gas enter the high
temperature regime of the cavitation bubbles these chemical species
are more likely to remain unaltered and not contaminate desired
reaction products. The pore diameter of the sparging elements is
typically in the range of about 0.5 .mu.m to 200 .mu.m.
[0026] Alkali metals and alkaline earth metals (especially
magnesium) are available as reduction agents. However, either of
the two eutectic alloys of sodium and potassium,
Na.sub.0.22K.sub.0.78 and Na.sub.0.44K.sub.0.56, is preferred
because each is liquid at typical ambient conditions and easily
dispersed as colloids (or finer) with ultrasonic energy in
anhydrous liquid hydrocarbon media. It is preferred to use reducing
metals in a form that is readily dispersed in the liquid reaction
medium. Further, it is generally preferred to disperse the
reductant metal(s) in the reaction medium before adding the halide
precursor.
[0027] Precursor halides that are gases, or volatile and reactive
liquids, or solids are reduced sonochemically. An example of a
precursor gas is boron trichloride (BCl.sub.3). Examples of liquid
precursor halides are titanium tetrachloride (TiCl.sub.4), vanadium
tetrachloride (VCl.sub.4), carbon tetrachloride, and silicon
chlorides (SiCl.sub.4 and Si.sub.2Cl.sub.6). Solid precursor
halides that are not completely insoluble in the liquid
sonochemical reaction medium are also suitable. Examples include
platinum dichloride (PtCl.sub.2), platinum dibromide (PtBr.sub.2),
Platinum diiodide (PtI.sub.2), aluminum trichloride (AlCl.sub.3),
titanium trichloride (TiCl.sub.3), platinum tetrachloride
(PtCl.sub.4) and zirconium tetrachloride, (ZrCl.sub.4).
[0028] Amorphous or nanocrystalline products have been produced
that include, as examples, Ti, TiSi.sub.2, Zr, PtZr, and PtTi.
[0029] An embodiment of the invention will be illustrated using
volatile liquid titanium tetrachloride as a representative
precursor halide, hexadecane as a representative inert, low vapor
pressure, hydrocarbon liquid, and a low melting point mixture (a
eutectic mixture, Na.sub.0.22K.sub.0.78) of sodium and potassium as
the reductant. The process will be illustrated with reference to
the drawing figures. FIG. 1 is a flow diagram for the formation and
separation of titanium metal product and FIG. 2 is a schematic
illustration of reactor apparatus for the process.
[0030] The flow diagram of FIG. 1 generally illustrates processing
steps for the production of a predetermined product by reduction of
a precursor halide. In this example the precursor halide is
titanium tetrachloride for the production of titanium metal. The
process may be practiced as a batch process or a continuous
process.
[0031] Referring to FIG. 1, a Cavitation Reactor is filled with a
suitable quantity of a liquid reaction medium from a Solvent
Reservoir. Cavitation conditions are created in the liquid medium
of the Cavitation Reservoir using Power from a suitable ultrasonic
transducer or the like. An inert gas, such as argon or helium, is
sparged through the liquid reaction medium in the Cavitation
Reactor using a Pump and Flow Control for the inert gas flow. As
illustrated it is preferred that the inert gas be circulated to and
from the Cavitation reactor in a closed loop to retain volatile
constituents in the reactor.
[0032] A suitable amount of a reductant, here a liquid mixture of
sodium and potassium metals (NaK), is added to the liquid reaction
medium in the Cavitation Reactor from NaK Input source. The
contents of the Cavitation Reactor may be subjected to a Heat
Exchanger for the removal of energy (labeled Power in FIG. 1) and
temperature control.
[0033] The product stream is subjected to a separation process in
Separator. In the separation step, the solids containing titanium,
sodium chloride, and potassium chloride are removed from the
reaction medium which is recycled as Solvent to the Solvent
Reservoir. The solids (Ti, NaCl, and KCl) are washed (Wash) to
remove the halide salts (as Solution of NaCl+KCl). Titanium metal
is recovered from the Wash step and sent to a Power consuming dryer
for obtaining pure dry titanium metal (Ti Output). The solution or
suspension of sodium chloride and potassium chloride are processed
in a power-consuming Evaporator for recovery and possible recycling
of these salts (NaCl+KCl Output).
[0034] The above illustrated process is applicable with minor
suitable modifications to many products that can be obtained by
many individual precursor halide compounds or combinations of
precursor halide compounds.
[0035] The above process was conducted in laboratory-scale
apparatus as illustrated in FIG. 2.
[0036] A reaction vessel 12 was partially immersed in the vibration
bath 34 of an ultrasonic generator 10. Ultrasonic generator
vibration bath 34 contained an anhydrous mixture of decalin and
hexadecane.
[0037] The reaction vessel 12 contained a liquid reaction medium 32
which in this example was hexadecane. A quantity of liquid
Na.sub.0.22K.sub.0.78 eutectic alloy was dispersed as colloidal
droplets in the hexadecane reaction medium 32. Reaction vessel 12
(a transparent glass vessel) was closed with a hermetic
feed-through cover 14. The vessel contained a thermometer 16. The
hexadecane reaction medium 32 was infused with very dry and
oxygen-free argon through feed-through closure cover 14 using gas
feed line 22B, sparger nozzle 24, gas return line 22A, needle valve
26, and diaphragm gas pump 26. The pressure of the argon atmosphere
was controlled using needle valve 28 and pressure gauge 30.
[0038] Activation of the ultrasonic generator 10 for about twenty
minutes dispersed the sodium-potassium mixture as colloidal
droplets in the initially clear hexadecane reaction medium 32. The
droplets of reductant metal, the cavitation bubbles, and the argon
gas bubbles were all very small and are not illustrated in FIG. 2.
The colloidal suspension became opaque blue-gray. The action of the
ultrasonic generator 10 was continued and liquid titanium
tetrachloride 36 was slowly added to the reaction medium 32 from
syringe 20 through addition tube 18 inserted through hermetic
feed-through cover 14. The amount of titanium tetrachloride added
was determined so as to be chemically equivalent to the amount of
sodium/potassium reductant in accordance with the following
equation, TiCl.sub.4+4 Na.sub.0.22K.sub.0.78.fwdarw.Ti+0.88
NaCl+3.12 KCl.
[0039] In this example 1.252 grams (35.20 mmol) of
Na.sub.0.22K.sub.0.78 was dispersed in 125 ml of hexadecane. Then
0.566 g (8.80 mmol) of TiCl.sub.4 was added to the dispersed
reductant metal.
[0040] As the reaction proceeded, the contents of the reaction
vessel turned black. Titanium chloride was added over a period of
about thirty minutes. The temperature of the materials in the
un-cooled vessel (except by heat loss to ambient air) increased
from about 25.degree. C. to about 80.degree. C. due to the input of
sonic energy and the exothermic reaction. The total insonation time
was sixty minutes. The ultrasonic generator 10 was turned off and
contents of the reaction vessel 12 were allowed to settle.
[0041] After about an hour of product particle sedimentation the
clear solvent above the black powder was removed by decantation.
The solids were washed with toluene to remove residual hexadecane,
and the mixture was centrifuged. The wash liquid was removed by
decanting and a second wash and separation procedure with pentane
was performed followed by drying in a vacuum oven. The salts were
identified as sodium chloride and potassium chloride by x-ray
diffraction and it was determined that they had been formed in
quantitative amounts in the reduction reaction. The other product
of the reduction of titanium tetrachloride was substantially
amorphous titanium metal.
[0042] The reaction medium-free solids were then washed with
formamide to separate sodium chloride and potassium chloride from
the titanium product. An anhydrous solvent for the metal chlorides
was used to prevent reaction with any unconsumed titanium chloride.
Water may be used to remove alkali metal halide salts or alkaline
earth metal salts in other embodiments of the invention.
[0043] The product powder was separated from the formamide solution
of the sodium and potassium salts by centrifuging. The amorphous
titanium metal was heated in a vacuum oven to remove residual
solvents and wash fluids. The metal can then be further heated in a
vacuum oven or other suitable heating apparatus for heat treatment
of the metal product. For example, the metal product may be
annealed, crystallized, melted and cast, or the like.
[0044] The above described reaction apparatus may be modified for
temperature control of the reaction vessel and/or of the circulated
argon or other inert gas atmosphere. Further, the circulated inert
gas may be scrubbed as it is recirculated to and from the reaction
vessel to remove oxygen and liquid hydrocarbon reaction medium
material. An oxygen scrubber could be inserted in gas return line
22A, between sparger nozzle 24 and the diaphragm gas pump 28.
[0045] The illustrated embodiment produced titanium metal from a
precursor halide charge material which contained only titanium
tetrachloride. Of course, titanium has many useful applications in
many industries. The titanium product could have been formed
stating with other titanium halides. And the product of the
titanium halide reduction can be annealed, treated by powder
metallurgy methods, hot or cold working, or other processing to
convert it to a metallurgical form required for an intended
application.
[0046] The described process may also be practiced by using a
precursor halide mixture comprising titanium halide and one or more
other precursor halides in smaller portion to form a reduction
product that is a mixture of titanium and, for example, aluminum
and vanadium preparatory to forming an titanium-aluminum-vanadium
alloy of titanium. Also titanium compounds, such as titanium
silicide (TiSi.sub.2), may be formed by using a mixture of halides
such as titanium tetrachloride and silicon tetrachloride.
[0047] Other metal products may be formed by this cavitation
process using precursor halides and alkali metal and/or alkaline
earth metal reductants in an inert, anhydrous reaction liquid
medium. For example, the following materials have been produced by
the laboratory-scale process described above.
[0048] Zirconium powder has been produced in accordance with the
reaction, ZrCl.sub.4+4 Na.sub.0.22K.sub.0.78.fwdarw.Zr+0.88
NaCl+3.12 KCl. The liquid reaction medium was 150 mL hexadecane at
ambient temperature. The sodium/potassium mixture was dispersed in
the amount of 0.057 g (29.72 mmol). Zirconium tetrachloride was
added to the dispersed reductant metal in the amount of 1.735 g
(7.43 mmol). Insonation time (after NaK dispersion) was 20 hrs. A
substantially quantitative yield of zirconium metal powder was
obtained from zirconium tetrachloride in the process.
[0049] Titanium disilicide powder has been produced in accordance
with the reaction, TiCl.sub.4+2 SiCl.sub.4+12
Na.sub.0.22K.sub.0.78.fwdarw.TiSi.sub.2+2.64 NaCl+9.36 KCl. The
liquid reaction medium was 150 mL hexadecane at ambient
temperature. The sodium/potassium mixture was dispersed in the
amount of 1.274 g (35.81 mmol). TiCl.sub.4 was added in the amount
of 0.566 g (0.325 mL, 2.98 mmol) together with SiCl.sub.4 in the
amount of 1.014 g (0.660 mL, 5.97 mmol). The total mass of
precursors was 2.85 g and the total mass of products was 2.81 g.
The insonation time (after NaK dispersion) was 60 minutes.
[0050] Platinum zirconium powder has been produced in accordance
with the equation, PtCl.sub.4+ZrCl.sub.4+8
Na.sub.0.22K.sub.0.78.fwdarw.PtZr+1.76 NaCl+6.24 KCl. The liquid
reaction medium was 125 mL hexadecane at ambient temperature. The
sodium potassium mixture was dispersed in the amount of 1.21 g
(34.00 mmol). Platinum tetrachloride was added in the amount of
1.43 g (4.25 mmol) with zirconium tetrachloride in the amount of
0.99 g (4.25 mmol). The total insonation time (after NaK
dispersion) was 16 hrs. A substantially quantitative yield of the
mixed platinum-zirconium powder was obtained form their halide
precursors.
[0051] Thus, while a few specific embodiments have been described
it is apparent the disclosed sonochemical practices for the
reduction of metal halides are of broad application.
* * * * *