FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
1. Title of the invention
"A METHOD FOR THE MANUFACTURE OF TITANIUM DIOXIDE NANO PARTICLES"
2. Applicant(s)
Name Nationality Address
TATA CHEMICALS LIMITED INDIA BOMBAY HOUSE, 24 HOMI MODI STREET, MUMBAI-400001,


3. Preamble to the description
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it is
to be performed.

The following disclosure generally relates to a process for the production of titanium dioxide nano particles. More particularly the disclosure relates to a process for the production of titanium dioxide nano particles at room or low temperature.
BACKGROUND
Titanium dioxide nano particles have a wide application in paints, plastics, cosmetics, inks, paper, chemical fibers and as a photo catalysis. The semiconducting and photocatalytic properties of titanium dioxide have been extensively studied for air and water purification and for solar cells. Properties influencing the photocatalytic activity of titanium, dioxide nano particles include surface area, crystal linity, crystallite size and crystal structure. The three polymorphs of titanium dioxide are anatase, rutile and brookite. It is known that anatase is the most active photocatalyst and a combination of high crystallinity and large specific area improves photocatalytic performance. These physical properties are controlled by the synthesis method adopted.
Tianium dioxide nano particles are currently being produced all over the world using a sulfate and chloride process. In the sulphate process, ilmenite dissolved in sulphuric acid is conventionally hydrolyzed at a temperature greater than 95°C, calcined at 800-1000°C, and then pulverized to produce titanium dioxide powders. However, during calcination and pulverization impurities are introduced, thereby reducing the quality of the sample. In the chloride process, TiCl4 reacts with oxygen at a temperature of about 1500°C, there by producing titanium dioxide nano particles. Relative to the sulphate process, the chloride process has the advantage in that the amount of waste is reduced, and continuous processing is possible with high quality rutile titanium dioxide production. Chloride process accounts for approximately 60 percent of the world wide titanium dioxide production. The inherent disadvantage of the process is the use of high temperature and less control over the particle shape and size.

Another method for the production of titanium dioxide nano particles is the sol-gel method. This method which involves the hydrolysis and condensation of alkoxide precursor, is a reliable method to synthesize ultrafine metallic oxides. This method has been widely employed for the preparation of titanium dioxide nano particles due to the inexpensive equipment required, low temperatures, easy doping and the homogeneous and highly pure product produced. Usually the particles obtained by this method are amorphous in nature and heat treatment at temperatures higher than 400°C is required to realize the transition of the titanium dioxide particles from amorphous to crystalline antase phase. However, such high heat treatment temperatures results in increased size of the titanium dioxide nano particles and decreases the specific surface area. Moreover, the titanium dioxide nano particles obtained by this process cannot be used on some common or potential substrates such as polymers and metals with low melting points. Therefore, the development of low temperature synthesis of crystalline titanium dioxide nano particles is essential for its implementation across a wider range of applications.
Some of limitations of the above process are the low molar concentrations of the solutions, elevated temperature during the synthesis and employing chemicals that are not eco-friendly. There is therefore a need for a process that would allow for the production of ■ crystalline titanium dioxide nano particles in a simple and efficient manner. Moreover, the process should be such that it allows for the production of titanium dioxide nano particles at room temperature without requiring any sintering process.
SUMMARY OF THE INVENTION
A method for the manufacture of titanium dioxide nano particles is disclosed. The method comprises preparing a solvent solution by mixing water, acetone and an electrolyte, preparing a titanium dioxide precursor solution by adding a titanium dioxide precursor to

ethanol, and hydrolyzing the titanium dioxide precursor by adding to the solvent solution the titanium dioxide precursor solution to precipitate titanium dioxide nano particles.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The accompanying drawing illustrates the preferred embodiments of the invention and together with the following detailed description serves to explain the principles of the invention.
Figure 1 is a X-ray diffraction pattern of a sample of titanium dioxide nano particles prepared in accordance with an aspect of the process.
Figure 2: is a UV absorption spectra of a sample of titanium dioxide nano particles as synthesized in accordance with an embodiment of the process and a sample of commercially available P-25 Degussa.
Figure 3 is a X-ray diffraction pattern of a sample of titanium dioxide prepared in accordance with an aspect of the process.
Figure 4 is a X-ray diffraction pattern of a sample of titanium dioxide prepared in accordance with an aspect of the process.
DETAILED DISCRIPTION
To promote the understanding of the principles of the invention, reference will be made to the embodiment and specific language will be used to describe the same. It will nevertheless be understood that no limitation to the scope the invention is thereby intended, such alterations and further modifications in the described process and such further applications of the principles of the invention as described therein being contemplated as would normally occur to one skilled in art to which the invention relates.

A process for the production of titanium dioxide nano particles is disclosed. More particularly a process for the production of titanium dioxide nano particles at room or low temperature is disclosed.
The process comprises of preparing a solvent solution by mixing together water, acetone and an electrolyte. A titanium dioxide precursor solution is prepared by adding a titanium dioxide precursor to ethanol. The titanium dioxide precursor solution so obtained is added to the solvent solution to precipitate titanium dioxide nano particles.
In accordance with an aspect, the process further comprises of separating the titanium dioxide nano particles from the solvent solution and drying them at room temperature.
The formation of titanium dioxide nano particles occurs in two stages. In the first stage titanium dioxide precursor is hydrolysed to from Ti - OH bonds in the following reaction: Ti(OR)4 + 4H20 -» 2Ti(OH)4 + 4ROH (hydrolysis)
In the second stage, the condensation polymerization stage, Ti-O-Ti bonds form resulting in the formation of a three dimensional structure, which precipitates out of the solution. This stage can be represented by the following reaction:
Ti(OH)4 - TiO2.XH2O + (2-X)H2O (condensation)
The solvent solution is prepared by adding to water the electrolyte to obtain a water electrolyte solution. To the water electrolyte solution acetone is added to obtain a solvent solution.
The titanium dioxide precursor solution is prepared by adding to ethanol a titanium dioxide precursor.
In accordance with an aspect, the titanium dioxide precursor solution is not added to the solvent solution as a dumping action but added to the solvent solution in a drop wise manner. In

accordance with an aspect, the solvent solution is stirred during the addition of the titanium dioxide precursor solution.
The titanium dioxide nano particles formed in the solvent solution may be separated from the solvent solution by any known method including but not limited to decanting, filtration, centrifugation alone or in combination with each other.
In accordance with an aspect, the separated titanium dioxide nano particles are washed. The separated titanium dioxide nano particles may be washed with a mixture of water and ethanol. In accordance with an aspect, the final washing of the separated titanium dioxide may be done with acetone.
The separated titanium dioxide nano particles are dried at room temperature. Any known method of drying including but not limited to air drying or vacuum drying may be used for drying the titanium dioxide nano particles. In accordance with an embodiment the separated titanium dioxide nano particles are dried at temperature in the range of 40°C to 55°C under vacuum.
In accordance with an aspect, the process further comprises of adding water to the mixture of titanium dioxide precursor solution and solvent solution having the precipitated titanium dioxide nano particles to dissolve precipitated electrolyte prior to separating and drying the precipitated titanium dioxide nano particles.
In accordance with an aspect, the titanium dioxide precursor solution is added to the solvent solution such that the final concentration of the titanium dioxide precursor in the solvent solution is in the range of 0.5 molar to 2.5 molar. Preferably the titanium dioxide precursor solution is added to the solvent solution such that the final concentration of the titanium dioxide precursor in the solvent solution is 2 molar.

The ratio of acetone to water in the solvent solution is in the range of 7:1 to 4: \ and the preferable ratio of acetone to water is 5:1.
In accordance with an aspect, titanium alkoxide is used as the titanium precursor. The titanium dioxide precursor may include but is not limited to titanium methoxide, titanium ethoxide, titanium propoxide, titanium isoproxide, titanium butoxide, titanium isobutoxide or their mixture. In accordance with a preferred embodiment titanium isoproxide is used as the titanium precursor.
In accordance with an aspect, the amount of titanium dioxide precursor in the titanium dioxide precursor solution is in the range of 95% to 98%.
The electrolyte that is added to solvent solution may be any salt including but not limited to sodium chloride, potassium chloride, calcium chloride, magnesium chloride, barium chloride and related salts. The amount of electrolyte that may be added to the solvent solution is in the range of 0.05 molar to 1 molar.
Specific embodiments are described below:
A method for the manufacture of titanium dioxide nano particles comprising preparing a solvent solution by mixing water, acetone and an electrolyte; preparing a titanium dioxide precursor solution by adding a titanium dioxide precursor to ethanol; and hydrolyzing the titanium dioxide precursor by adding to the solvent solution the titanium dioxide precursor solution to precipitate titanium dioxide nano particles.
Such method(s) further comprising separating the precipitated titanium dioxide nano particles and drying them at a temperature in the range of 40°C to 55°C under vacuum.
Such method(s) further comprising adding water to the mixture of titanium dioxide precursor solution and solvent solution having the precipitated titanium dioxide nano particles to dissolve precipitated electrolyte.

Such method(s) wherein the titanium dioxide precursor solution is added to the solvent solution in a drop wise manner under constant stirring.
Such method(s) wherein the ratio of acetone to water is in the range of 7:1 to 4:1.
Such method(s) wherein the titanium precursor is any of titanium methoxide, titanium ethoxide, titanium propoxide, titanium isoproxide, titanium butoxide, titanium isobutoxide or their mixture.
Such method(s) wherein the titanium dioxide precursor solution is added to the solvent solution in an amount such that the final concentration of the titanium dioxide precursor in the solvent solution is in the range of 0.5 molar to 2.5 molar.
Such method(s) wherein the electrolyte is any of sodium chloride, potassium chloride, calcium chloride, magnesium chloride, barium chloride or their mixture.
Such method(s) wherein the amount of electrolyte in the solvent solution is in the range of 0.05 molar to 1 molar.
Titanium dioxide nano particles obtained by such process(s).
Such titanium dioxide nano particle(s) wherein the titanium dioxide nano particles have an anatase structure.
The following example is provided to explain and illustrate certain preferred embodiments of the process of the invention.
Example 1: In a 5 litre conical flask 41 gm of sodium chloride was dissolved in 458 ml
of double distilled water. To this 2286 ml of acetone was added to form uniform solvent
solution. Hydrolysis of titanium isopropoxide (98%) was done by adding 1600 ml of the
titanium dioxide precursor solution at the rate of 10ml/min under continuous stirring. At the end
of the hydrolysis, 500 ml of distilled water was added to dissolve the salt that would have
precipitated along with the end product. The solution was then centrifuged to separate the
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precipitate and the precipitate was washed with distilled water and acetone. The washed precipitate was dried at 55°C under vacuum for 24 hr. The formation of anatase titanium dioxide nano particles was confirmed from X-ray diffraction pattern. Figure 1 illustrates the x-ray diffraction pattern for a sample of titanium dioxide nano particles formed. Figure 2 illustrates the UV absorption spectra of a sample of synthesized anatase titanium dioxide powder as against P-25 Degussa. The size of the particles was measured to be 7nm from X-ray diffraction using Debey-Scherrer equation. The BET (Brunauer, Emmett and Teller) surface area of the prepared anatase titanium dioxide nano particles was measured to be 236m /g. The yield of the product is 100%.
Example 2: In a 3 litre conical flask 10.5 gm of sodium chloride was dissolved in 115 ml of double distilled water. To this 572 ml of acetone was added to form uniform mixed solvent solution. Hydrolysis of titanium isopropoxide was done by adding 400 ml of the titanium dioxide precursor solution at the rate of 10ml/min under continuous stirring. At the end of the hydrolysis, 200 ml of distilled water was added to dissolve the salt that would have precipitated along with the end product. The solution was then centrifuged to separate the precipitate and the precipitate was washed with distilled water and acetone. The washed precipitate was dried at 50°C under vacuum for 24 hr. The formation of anatase titanium dioxide nano particles was confirmed from X-ray diffraction analysis. Figure 3 illustrates the X-ray diffraction pattern of a sample of the titanium dioxide nano particles. The size of the particles was measured to be 7iim from X-ray diffraction using Debey-Scherrer equation. The BET (Brunauer, Emmett and Teller) surface area of the prepared anatase titanium dioxide nano particles was measured to be 239m /g. The yield of the product is 100%.
Example 3: In a 3 litre conical flask 5.2 gm of sodium chloride was dissolved in 115ml
of double distilled water. To this 572 ml of acetone was added to form uniform mixed solvent
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solution. Hydrolysis of titanium isopropoxide was done by adding 400 ml of the titanium dioxide precursor solution at the rate of 10ml/min under continuous stirring. At the end of the hydrolysis, 200 ml of distilled water was added to dissolve the salt that would have precipitated along with the end product. The solution was then centrifuged to separate the precipitate and the precipitate was washed with distilled water and acetone. The washed precipitate was dried at 45°C under vacuum for 24 hr. The formation of anatase titanium dioxide nano particles was confirmed from X-ray diffraction analysis. Figure 4, illustrates the X-ray diffraction pattern of a sample of the titanium dioxide nano particles obtained. The size of the particles was measured to be 7nm from X-ray diffraction using Debey-Scherrer equation. The BET (Brunauer, Emmett and Teller) surface of the prepared anatase titanium dioxide nano particles was measured to be 232m2/g. The yield of the product is 100%.
Example 4: In a 1 litre conical flask 10 gm of calcium chloride was dissolved in 40 ml of double distilled water. To this 200 ml of acetone was added to form uniform mixed solvent solution. Hydrolysis of titanium isopropoxide was done by adding 80 ml of the titanium dioxide precursor solution at the rate of 5ml/min under continuous stirring. At the end of the hydrolysis, 200 ml of distilled water was added to dissolve the salt that would have precipitated along with the end product. The solution was then centrifuged to separate the precipitate and the precipitate was washed with distilled water and acetone. The washed precipitate was dried at 45°C under vacuum for 24 hr. The formation of anatase titanium dioxide nano particles was confirmed from X-ray diffraction. The size of the particles was measured to be 7 nm from X-ray diffraction using Debey-Scherrer equation. The BET (Brunauer, Emmett and Teller) surface of the prepared anatase titanium dioxide nano particles was measured to be 235m /g.
Example 5: In a 1 litre conical flask 6 gm of barium chloride was dissolved in 40 ml of
double distilled water. To this 200 ml of acetone was added to form uniform mixed solvent
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solution. Hydrolysis of titanium isopropoxide was done by adding 80 ml of the titanium dioxide precursor solution at the rate of 5ml/min under continuous stirring. At the end of the hydrolysis, 200 ml of distilled water was added to dissolve the salt that would have precipitated along with the end product. The solution was then centrifuged to separate the precipitate and the precipitate was washed with distilled water and acetone. The washed precipitate was dried at 45° C under vacuum for 24 hr. The formation of anatase titanium dioxide nano particles was confirmed from X-ray diffraction. The size of the particles was measured to be 6nm from X-ray diffraction using Debey-Scherrer equation. The BET (Brunauer, Emmett and Teller) surface of the prepared anatase titanium dioxide nano particles was measured to be 232m /g. INDUSTRIAL APPLICABILITY
The process as disclosed allows for the production of titanium dioxide nano particles in a simple and efficient manner. The process as disclosed allows for the production of titanium dioxide nano particles at room temperature without the need of a sintering process. Moreover, the synthesis is carried out at high molar concentrations (2M) there by increasing the yield, making the process viable for large scale synthesis.
The titanium dioxide nano particles produced by the disclosed process have a size in the range of 5 to 200 nm with a predominant amount of titanium dioxide nano particles having an anatase structure. These titanium dioxide nano particles exhibit excellent transmission properties.
It is believed that the formation of titanium dioxide nano particles during the transition
from titanium alkoxide precursor to the oxide depends on several factors including the
dielectric constant of the solvent, surface charge potential and ratio of water and other
organic solvents and the electrolytes. In the process as disclosed, the acetone water system
essentially acts as a dielectric constant tuning system. The dielectric constant tuning helps in
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the stability of the nano particles against aggregation by adjusting the surface potential of the particles. The ratio of water and acetone along with effect of electrolyte, by altering the surface potential of the particles, balance the van der Waals attractions and electrostatic repulsive forces. This allows the formation of titanium dioxide nano particles at room temperature, at high molar concentration. Moreover, the addition of electrolytes alters the surface potential of the particles to greater than 12mV necessary for the stability of the nano particles.
The titanium dioxide nano particles synthesized by the disclosed process, find use in diverse applications. By way of example the titanium dioxide nano particles may be used in paint and fabric industry as both antibacterial agent and as a pigment having superior pigment properties. The titanium dioxide nano particles produced by this process have high transparency, and therefore find use in cosmetics as UV absorption agent. Moreover, due to their small size and high surface area these titanium dioxide nano particles are very good photocatalyst and hence find application in self cleaning windows.

We claim:
1. A method for the manufacture of titanium dioxide nano particles comprising:
preparing a solvent solution by mixing water, acetone and an electrolyte ;
preparing a titanium dioxide precursor solution by adding a titanium dioxide precursor to ethanol; and
hydrolyzing the titanium dioxide precursor by adding to the solvent solution the titanium dioxide precursor solution to precipitate titanium dioxide nano particles.
2. A method as claimed in claim 1, further comprising separating the precipitated titanium dioxide nano particles and drying them at a temperature in the range of 40°C to 55°C under vacuum.
3. A method as claimed in any preceding claim, further comprising adding water to the mixture of titanium dioxide precursor solution and solvent solution having the precipitated titanium dioxide nano particles to dissolve precipitated electrolyte.
4. A method as claimed in any preceding claim, wherein the titanium dioxide precursor solution is added to the solvent solution in a drop wise manner under constant stirring.
5. A method as claimed in any preceding claim, wherein the ratio of acetone to water is in the range of 7:1 to 4:1.

6. A method as claimed in any preceding claim, wherein the titanium precursor is any of titanium methoxide, titanium ethoxide, titanium propoxide, titanium isoproxide, titanium butoxide, titanium isobutoxide or their mixture.
7. A method as claimed in any preceding claim, wherein the titanium dioxide precursor solution is added to the solvent solution in an amount such that the final concentration of the titanium dioxide precursor in the solvent solution is in the range of 0.5 molar to 2.5 molar.
8. A method as claimed in any preceding claim, wherein the electrolyte is any of sodium chloride, potassium chloride, calcium chloride, magnesium chloride, barium chloride or their mixture.
9. A method as claimed in any preceding claim, wherein the amount of electrolyte in the solvent solution is in the range of 0.05 molar to 1 molar.
10. Titanium dioxide nano particles obtained by a process as claimed in any preceding claim.
11. Titanium dioxide nano particles as claimed in claim 10, wherein the titanium dioxide nano particles have an anatase structure.
12. A process substantially as herein described with reference to and as illustrated with
the accompanying figures.
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13. Titanium dioxide nano particles substantially as herein described with reference to and as illustrated in the accompanying figures.