U.S. patent application number 10/539718 was filed with the patent office on 2006-03-09 for purification of titanium tetrachloride.
Invention is credited to James Timothy Cronin, Thomas Shields Elkins, Lisa Edith Helberg, James Elliott Merkle, Steve Edward Mirabella.
Application Number | 20060051267 10/539718 |
Document ID | / |
Family ID | 32713449 |
Filed Date | 2006-03-09 |
United States Patent
Application |
20060051267 |
Kind Code |
A1 |
Cronin; James Timothy ; et
al. |
March 9, 2006 |
Purification of titanium tetrachloride
Abstract
The present invention is a process for reducing raw material
yield losses resulting from the passivation aluminum chloride and
vanadium chlorides in the chlorinator discharge in a
carbochlorination process for making titanium tetrachloride.
Inventors: |
Cronin; James Timothy;
(Townsend, DE) ; Elkins; Thomas Shields; (Waverly,
TN) ; Helberg; Lisa Edith; (Middletown, DE) ;
Mirabella; Steve Edward; (New Johnsonville, TN) ;
Merkle; James Elliott; (Long Beach, TN) |
Correspondence
Address: |
Jessica M Sinnott;E I du Pont de Nemours and Company
Legal Patent
4417 Lancaster Pike
Wilmington
DE
19805
US
|
Family ID: |
32713449 |
Appl. No.: |
10/539718 |
Filed: |
January 9, 2004 |
PCT Filed: |
January 9, 2004 |
PCT NO: |
PCT/US04/00765 |
371 Date: |
July 20, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60439190 |
Jan 9, 2003 |
|
|
|
Current U.S.
Class: |
423/69 |
Current CPC
Class: |
C22B 34/1295 20130101;
C01G 23/024 20130101; C22B 34/1272 20130101; C22B 34/1222 20130101;
Y02P 10/20 20151101 |
Class at
Publication: |
423/069 |
International
Class: |
C22B 34/10 20060101
C22B034/10 |
Claims
1. A method in the purification of a crude titanium tetrachloride
chlorinator discharge from the carbochlorination of titanium
containing materials to minimize the loss of raw materials
resulting from passivation of aluminum chloride and vanadium
oxychloride, comprising: (a) mixing into the crude titanium
tetrachloride chlorinator discharge comprising vanadium chlorides
and aluminum chloride: (1) a vanadium passivating agent to
passivate the vanadium chlorides present and form in the discharge
one or more easy-to-separate vanadium-containing compounds, and (2)
an aluminum passivating agent to passivate the aluminum chloride
present and form one or more easy-to-separate aluminum-containing
compounds wherein the aluminum passivating agent is selected from
the group consisting of water, water containing solutions, water
containing mixtures, and carboxylic acids, with the proviso that:
(i) when, after mixing the vanadium passivating agent into the
chlorinator discharge, titanium oxychloride is formed in the
discharge, no aluminum passivating agent is mixed into the
discharge; and (ii) when after mixing the vanadium passivating
agent into the chlorinator discharge, no titanium oxychloride is
formed in the discharge, mixing into the discharge an amount of
aluminum passivating agent to passivate the aluminum chlorides and
react with the titanium tetrachloride to form titanium oxychloride;
and (b) separating from titanium tetrachloride chlorinator
discharge the easy-to-separate vanadium- and aluminum-containing
compounds to form a purified titanium tetrachloride.
2. The process of claim 1 wherein the separation process is
selected from the group consisting of flashing distillation,
multi-stage distillation, a solid-liquid separation process,
filtration, and centrifugation.
3. The process of claim 1 wherein the vanadium passivating agent
and the aluminum passivating agent are mixed into the discharge
essentially simultaneously.
4. The process of claim 1 wherein the vanadium passivating agent is
mixed into the discharge before the aluminum passivating agent is
mixed into the discharge stream.
5. The process of claim 1 wherein the vanadium passivating agent is
mixed into the discharge after the aluminum passivating agent is
mixed into the discharge stream.
6. The process of claim 1 wherein the vanadium passivating agent is
mixed into the discharge in an amount sufficient to reduce the
concentration of, but not eliminate the vanadium chlorides
present.
7. The process of claim 1 wherein the aluminum passivating agent is
comprised of a purge containing products from the passivation of
vanadium chlorides taken from a process step following the
separation step.
8. The process of claim 1 wherein the addition of the vanadium
passivating agent and the aluminum passivating agent are controlled
by a process control method.
9. The process of claim 1 wherein the vanadium passivating agent is
an organic oil.
10. The process of claim 1 wherein the vanadium passivating agent
is a petroleum oil, an animal fat, a vegetable oil or a combination
thereof
11. The process of claim 1 wherein the vanadium passivating agent
is a hydrogenated naphthenic oil.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Cross-reference is made to U.S. Provisional Application No.
60/439190 filed on Jan. 9, 2003, which is incorporated herein by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a process for the removal of
multiple metal chlorides from a crude titanium tetrachloride stream
produced by chlorination of titanium-bearing compounds, and more
particularly to a process wherein the removal of multiple metal
chlorides occurs in a single reaction vessel.
[0003] In the production of titanium tetrachloride, raw materials,
including ilmenite or rutile ores or other titanium-containing
materials such as those obtained from beneficiating these ores, are
reacted with chlorine and carbon (carbochlorination) to yield a
mixture of metal chlorides in a crude titanium tetrachloride
stream, from which titanium tetrachloride of sufficient purity may
be recovered that may be used as a starting material to make
titanium metal or titanium dioxide pigment.
[0004] Common metal chloride impurities present in the crude
titanium tetrachloride include chlorides and complex chlorides of
aluminum, niobium, tantalum, and vanadium. These metal chloride
impurities are not susceptible to removal by distillation because
of the proximity of their boiling points to that of titanium
tetrachloride or their solubility in the titanium tetrachloride.
They can have a detrimental impact on downstream processes. Thus,
it is important to remove them or treat them to inhibit their
detrimental properties.
[0005] Aluminum chloride, for example, is highly corrosive and
attacks the metal materials of construction in the equipment
downstream of its formation; thus, aluminum chloride must be
rendered non-corrosive via treatment with a passivating agent early
in the processing of making crude titanium tetrachloride.
[0006] Niobium and tantalum chlorides may condense downstream and
cause fouling problems. Conveniently these two metal chlorides may
be removed in the passivation of the aluminum chloride through
their preferential reaction with certain aluminum passivating
agents.
[0007] Water, sodium chloride, sodium hydroxide or a mixture of
these are the most common agents added to passivate aluminum
chloride. The passivated aluminum compounds are more
easy-to-separate from the crude titanium tetrachloride stream than
aluminum chloride. Aluminum passivating agents are selected to form
aluminum compounds that are not corrosive to the equipment. See,
for example, U.S. Pat. Nos. 2,600,881; 4,125,586; and U.S. Pat. No.
4,521,384. Furthermore, as taught by Bonsack in U.S. Pat. No.
4,070,252, use of water to treat crude titanium chloride streams
also converts niobium and tantalum chlorides to species insoluble
in liquid titanium tetrachloride, which can be readily removed by
filtration or other simple separation techniques.
[0008] Vanadium chlorides form colored species that must be removed
if the titanium tetrachloride is to be used for production of
titanium dioxide pigment. Typically, treatment agents are added to
the crude titanium tetrachloride to chemically modify these
vanadium compounds so that they may be removed. Therefore, there is
a body of art that teaches treatment for removing vanadium
chlorides from titanium tetrachloride, but this body of art is
essentially separate from that of the passivation of aluminum
chloride in titanium tetrachloride.
[0009] The prior art in the passivation of vanadium chlorides
discloses the use of catalytic metals, such as iron and copper or
other agents such as activated carbons, hydrogen, hydrogen sulfide
and a number of organic compounds, such as oils, esters, and
amines. Examples of prior art teachings for removal of vanadium
compounds from crude titanium tetrachloride include the following.
Swiss Patent No. 262267, published in 1949, discloses removing
colored metal chlorides (Cr, and V) by treating the crude titanium
tetrachloride, at an elevated temperature, with a metal-free
organic compound which is carbonized by the chlorides. U.S. Pat.
No. 2,560,424 discloses a method to remove the colored impurities
from titanium tetrachloride by simultaneously adding to the crude
titanium tetrachloride small amounts of aluminum metal and
anhydrous aluminum chloride. Australian Patent No. 219,385 teaches
the use of metallic sodium to remove vanadium impurities from
titanium tetrachloride.
[0010] While methods have long been available for treatment of
crude titanium tetrachloride, treatments to remove the metal
chlorides of aluminum, niobium and tantalum have been practiced
separately from treatments to remove vanadium chlorides from crude
titanium tetrachloride. The present invention is a method to remove
metal chloride impurities including the chlorides of aluminum and
vanadium in a way that minimizes the loss of process raw materials
such as titanium containing materials, coke, chlorine, and vanadium
and aluminum passivating agents. The present process is more cost
effective, produces less waste and more product and is the result
of a simple change in the sequence of and locations for the
additions of the aluminum and vanadium passivating agents.
SUMMARY OF THE INVENTION
[0011] The present invention provides a method in the purification
of a crude titanium tetrachloride chlorinator discharge from the
carbochlorination of titanium containing materials to minimize the
loss of raw materials resulting from passivation of aluminum
chloride and vanadium oxychloride, comprising: [0012] (a) mixing
into a crude titanium tetrachloride chlorinator discharge
comprising vanadium chlorides and aluminum chloride: [0013] (1) a
vanadium passivating agent to passivate the vanadium chlorides
present and form in the discharge one or more easy-to-separate
vanadium-containing compounds, and [0014] (2) an aluminum
passivating agent to passivate the aluminum chloride present and
form in the discharge one or more easy-to-separate
aluminum-containing compounds wherein the aluminum passivating
agent is selected from the group consisting of water, water
containing solutions, water containing mixtures, and carboxylic
acids, with the proviso that: [0015] (i) when, after mixing the
vanadium passivating agent into the chlorinator discharge, titanium
oxychloride is formed in the discharge, no aluminum passivating
agent is mixed into the discharge; and [0016] (ii) when, after
mixing the vanadium passivating agent into the chlorinator
discharge, no titanium oxychloride is formed, mixing into the
discharge an amount of aluminum passivating agent to passivate the
aluminum chloride and react with the titanium tetrachloride to form
titanium oxychloride; and [0017] (b) separating from the titanium
tetrachloride chlorinator discharge the easy-to-separate vanadium-
and aluminum-containing compounds to form a purified titanium
tetrachloride. In the present process the separation typically
depends upon the phases present in the discharge and suitable
separation techniques are well known in the art. Typically a
distillation process is employed for vapor-liquid-solid separation,
preferably selected from the group consisting of flash distillation
and multi-stage distillation. The solid-liquid separation process
can be a filtration or centrifugation.
[0018] The addition of the vanadium and aluminum passivating agents
may be made such that the vanadium passivating agent and the
aluminum passivating agent are mixed into the discharge essentially
simultaneously or the vanadium passivating agent may be mixed into
the discharge before the aluminum passivating agent is mixed into
the discharge, or the vanadium passivating agent may be mixed into
the discharge after the aluminum passivating agent is mixed into
the discharge or the vanadium passivating agent may be mixed into
the discharge both before and after the aluminum passivating agent
is mixed into the discharge.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The present invention is a method in the purification of a
crude titanium tetrachloride chlorinator discharge from the
carbochlorination of titanium containing materials to minimize the
loss of raw materials resulting from passivation of aluminum
chloride and vanadium chlorides.
[0020] The term vanadium chlorides as used herein includes vanadium
oxychloride compounds and other vanadium chloride compounds that
are not susceptible to removal from crude titanium tetrachloride by
distillation.
[0021] In the present invention, the passivation of vanadium
chlorides may be accomplished in a two step addition of the
vanadium passivating agent or in a single step addition. In the two
step addition, a vanadium passivating agent is mixed into the
discharge in an amount sufficient to reduce, but not eliminate the
vanadium chlorides present and form one or more easy-to-separate
vanadium-containing compounds. When titanium oxychloride is present
in the discharge treated with the vanadium passivating agent, no
aluminum passivating agent is added. When titanium oxychloride is
not present, an amount of aluminum passivating agent sufficient to
form titanium oxychloride is added to form easy-to-separate
aluminum-containing compounds. The easy-to-separate vanadium- and
aluminum-containing compounds may be separated from the discharge.
Then, a second addition step of a vanadium passivating agent in an
amount sufficient to passivate the remaining vanadium chlorides is
made to form easy-to-separate vanadium-containing compounds,
followed by a separation step to form a purified titanium
tetrachloride.
[0022] In the single step addition of the vanadium passivating
agent, sufficient vanadium passivating agent is mixed into the
discharge to passivate all of the vanadium chlorides in a single
step, and, if necessary, addition of aluminum passivating agent is
made if there remains active aluminum chloride in the discharge as
determined by the absence of titanium oxychloride in the discharge.
In any event, all of the aluminum chloride present in the discharge
must be passivated, no matter which method (two step or single
step) is used to passivate the vanadium chlorides, since the
presence of active aluminum chloride after this point in the
overall purification process will result in corrosion of downstream
equipment.
[0023] The terms passivating and passivation as used herein mean
converting the vanadium- and aluminum-containing compounds present
in the crude titanium tetrachloride discharge to compounds that are
easy-to-separate from the titanium tetrachloride and neutralizing
the compounds' adverse effects. "Easy-to-separate" typically means
a solid, but it also includes compounds that may be separated from
the titanium tetrachloride by distillation or removal as an
adsorbed species, and the like. Surprisingly, it has been found
that the product of the passivation of vanadium oxychloride in
crude titanium tetrachloride discharge with an organic oil is a
passivating agent for aluminum chloride. The result of this
discovery according to the present invention is an improved
chlorination process wherein there is the potential to save
production costs by reducing the titanium yield loss while at the
same time improving raw material utilization to reduce process cost
and the amount waste--solid, liquid, and vapor.
[0024] In the present invention, the point of addition of the
passivating agents into the flow of the chlorinator product stream,
that is, crude titanium tetrachloride discharge, may be optimized
for (1) the reduction and elimination of corrosion from active
aluminum chloride, (2) minimal yield losses of raw materials, and
(3) to take advantage of the ability of passivated vanadium
compounds to provide at least part of the total amount of
passivating agent needed to control passivation of aluminum
chloride, as measured by titanium oxychloride concentration.
[0025] Addition of the aluminum passivating agent is dependent on
whether there is titanium oxychloride in the crude titanium
tetrachloride chlorinator discharge stream. Aluminum chloride is
completely passivated once titanium oxychloride is formed in the
discharge. Aluminum passivating agent may be mixed into the
chlorinator discharge simultaneously with the vanadium passivating
agent or before addition of the vanadium passivating agent or after
addition of the vanadium passivating agent. After mixing the
vanadium or aluminum passivating agent into the chlorinator
discharge, the discharge is analyzed for titanium oxychloride. If
titanium oxychloride is formed, addition of aluminum passivating
agent is not required. If no titanium oxychloride is formed, then
an amount of aluminum passivating agent sufficient to passivate the
aluminum chloride and react with the titanium tetrachloride to form
titanium oxychloride is mixed into the chlorinator discharge.
[0026] Water is most preferred as the aluminum passivating agent in
the present process. Water solutions or mixtures may be used as
passivating agents even if the materials other than the water show
no reactivity towards aluminum chloride.
[0027] Since some fraction of the aluminum chloride is passivated
by the reaction product of vanadium oxychloride with the vanadium
passivating agent, it is preferable to add only 1 to 1.5 times the
amount of passivating agent to stoichiometrically react with the
remaining aluminum in the discharge. More preferably the amount of
aluminum passivating agent added is 1.1 to 1.3 times the
stoichiometric requirement.
[0028] Organic oils have been found to be useful as vanadium
passivating agents including petroleum oils, such as mineral oils
and waxes, animal fat, and vegetable oils and combinations thereof.
The organic oil may be hydrogenated. A specific example of a useful
organic oil is hydrogenated naphthenic oil. The essential element
in selecting a substance as a vanadium passivating agent is the
ability of the reaction product of the passivating agent with
vanadium oxychloride to function as an aluminum passivating agent.
Those skilled in the art may find other organic compounds that are
functionally equivalent to an organic oil that are also useful as
the vanadium passivating agent. Similarly, some inorganic vanadium
passivating agents may also be useful as functional equivalents to
the organic oil, so long as there are no detrimental effects, such
as color formation in the titanium tetrachloride, or where the
passivated compounds may become re-chlorinated. Especially
preferred as the organic oil vanadium passivating agent is a
hydrogenated naphthenic oil.
[0029] The amount of vanadium passivating agent is based on the
agent's stoichiometric reaction ratio with the vanadium chlorides.
Ideally, this ratio should be determined experimentally, rather
than theoretically. Preferably the amount of vanadium passivating
agent added is 0.8 to 1.2 times the stoichiometric quantity
required to react with the vanadium chlorides to be removed from
the stream being treated, which may be all or any fraction of the
vanadium present in that stream. More preferably the amount of
vanadium passivating agent is from 0.95 to 1.1 times the
stoichiometric requirement.
[0030] Regardless of the amount of vanadium passivating agent
added, it is possible to calculate the amount of vanadium removal
reaction products capable of passivating aluminum chloride and then
reduce the amount of aluminum passivating agent or reduce the
addition rate by an equivalent amount which can substantially
reduce titanium losses due to excess addition of aluminum
passivating agents which react with titanium tetrachloride. For
example, one method to calculate the amount of vanadium removal
reaction products capable of passivating aluminum chloride is by
infrared spectroscopy, based on concentration of vanadium
oxychloride in the chlorinator discharge.
[0031] Following addition of the passivating agents, there is
provided a separation step wherein the easy-to-separate vanadium-
and aluminum-containing compounds are separated from the titanium
tetrachloride chlorinator discharge to form a purified titanium
tetrachloride using a vapor-liquid-solid separation process or a
solid-liquid separation process. A vapor-liquid-solid separation
process is typically a distillation process, preferably selected
from the group consisting of flashing distillation and multi-stage
distillation. A solid-liquid separation process is typically
filtration or centrifugation.
[0032] The separation process may occur in one or more steps. For
example, depending on the order of addition of the vanadium and
aluminum passivating agents, intermediate separation steps may be
performed. Particularly, in a two step addition of the vanadium
passivating agent, a separation step may be performed after all of
the aluminum chloride has been converted to easy-to-separate
aluminum-containing compounds. A separation step is performed after
the second addition of the vanadium passivating agent.
[0033] Alternatively, following a separation step after addition of
vanadium passivating agent, a purge containing products from the
passivation of vanadium chlorides may be used as the aluminum
passivating agent.
[0034] Process control methods for the addition of the aluminum
passivating agent, the vanadium passivating agent, or both can be
applied to the present invention. For example, the control methods
disclosed in U.S. Pat. No. 6,562,312 are particularly useful for
controlling addition of aluminum passivating agent. Therein is
provided, an in-process, real time control loop capable of
controlling the passivation of aluminum chloride in crude titanium
tetrachloride chlorinator discharge wherein an aluminum passivating
agent is mixed into the discharge in an amount sufficient to form
titanium oxychloride. The amount of aluminum passivating agent
added is controlled based on comparison of the titanium oxychloride
concentration measured in-process with an aim point. Preferably,
the concentration of titanium oxychloride is measured by an optical
method selected from the group consisting of transmission filter
Infrared spectroscopy, transmission Fourier Transform Infrared
spectroscopy, Raman spectroscopy, Attenuated Total Reflectance
Infrared spectroscopy, and Attenuated Total Reflectance Fourier
Transform Infrared spectroscopy.
[0035] The presence and concentration of titanium oxychloride may
be measured by use of transmission filter Infrared spectroscopy,
transmission Fourier Transform Infrared spectroscopy, Raman
spectroscopy, and Attenuated Total Reflectance Infrared
spectroscopy, and Attenuated Total Reflectance Fourier Transform
Infrared spectroscopy in a frequency range of from 800 to 2000
cm-1.
[0036] For accuracy and precision, it is most preferred to measure
the presence and the concentration of titanium oxychloride by
diamond based Attenuated Total Reflectance Fourier Transform
Infrared at a frequency of about 820 cm-1. Diamond based attenuated
reflectance means that the infrared probe or detector placed in the
process stream has a diamond element. Suitable probe units include
those manufactured by ASI Applied Systems of Millersville, Md.,
Axiom Analytic, Inc. of Irvine, Calif. and others.
[0037] In the following examples VOCl.sub.3 passivation is measured
by Fourier Transform Infrared Spectroscopy (FTIR).
EXAMPLE 1
[0038] A round bottomed flask was filled with 100 mL TiCl.sub.4,
0.92 g VOCl.sub.3 (5.31 mmol), and 0.174 g AlCl.sub.3 (1.30 mmol).
The AlCl.sub.3 was handled air-free to avoid moisture
contamination. The reaction mixture was heated to 100.degree. C.
Hydrogenated naphthenic oil (ERGON Incorporated's product brand
Ergon H-750) was added (1.0333 g). The reaction mixture was held at
temperature for 30 minutes. At this point, all of the VOCl.sub.3
was passivated, as measured by FTIR. To determine how much
unreacted AlCl.sub.3 remained, 30 microliter (1.61 mmol) of water
were added by syringe. Any AlCl.sub.3 in solution would react with
the water before TiOCl.sub.2 was formed. A total of 1531 ppm
TiOCl.sub.2 was generated from the water addition, as observed by
FTIR. If all of the AlCl.sub.3 was present, only 280 ppm should
have been observed. Since an extra 1301 ppm TiOCl.sub.2 (1.67 mmol)
formed, all of the AlCl.sub.3 had already been passivated in the
solution.
EXAMPLE 2
[0039] A round bottomed flask was filled with 100 mL TiCl.sub.4,
0.92 g VOCl.sub.3 (5.31 mmol), and 1.74 g AlCl.sub.3 (13.0 mmol).
The AlCl.sub.3 was handled air-free to avoid moisture
contamination. The reaction mixture was heated to 100.degree. C.
The oil from Example 1 was added (1.0401 g). The reaction mixture
was held at temperature for 30 minutes. At this point, all of the
VOCl.sub.3 was passivated, as measured by FTIR. To determine how
much unreacted AlCl.sub.3 remained, 290 microliter (16.1 mmol) of
water were added by syringe. A total of 6808 ppm TiOCl.sub.2 was
generated from the water addition. If all of the AlCl.sub.3 was
still present, only 2371 ppm TiOCl.sub.2 should have been observed.
Since an extra 4437 ppm TiOCl.sub.2 (5.70 mmol) formed, part of the
AlCl.sub.3 was passivated in the solution. The amount of AlCl.sub.3
reacted was stoichiometrically equivalent to the amount of oxygen
initially present in solution as part of the VOCl.sub.3, within
experimental error.
EXAMPLE 3
[0040] Water was added as an aluminum passivating agent to a crude
TiCl.sub.4 stream containing metal chloride contaminants AlCl.sub.3
and VOCl.sub.3 produced by the chlorination of titanium-bearing
ore, following discharge from the chlorinator and separation of
condensable solids. Water addition was in control by the control
method described in U.S. Pat. No. 6,562,312. The hydrogenated,
naphthenic oil, from Example 1 (vanadium passivating agent) was
added to the TiCl.sub.4 stream at the same location as the water
addition. In contrast to operating the process in the absence of
the vanadium passivating agent, the demand for aluminum passivating
agent was reduced by 50% while reducing VOCl.sub.3 by 20% of its
original concentration.
* * * * *