KR20020092583A - Preparation of TiO2 ultrafine powders from titanium tetrachloride with inorganic acid solution by the advanced washing method - Google Patents

Abstract

PURPOSE: A method for preparing TiO2 supermicro powder using titanium tetrachloride(TiCl4) and an inorganic acid aqueous solution is provided, to improve the washing method, thereby allowing the nano-sized crystalline TiO2 powder with a narrow distribution of size without the pulverization process. CONSTITUTION: The method comprises the steps of adding TiCl4 into a reactor charted with an inert gas at a room temperature, and adding 0.01-90% inorganic acid aqueous solution by the amount more than the stoichiometric amount to prepare a Ti4+ aqueous solution mixed with an inorganic acid; adding 0.01-90% inorganic acid aqueous solution to the obtained solution at a room temperature to prepare a 0.1-1.4 M Ti4+ aqueous solution; leaving the diluted solution at 15-200 deg.C to obtain a TiO2 particle-containing slurry; filtering the slurry, washing the filtered one with an alkali halide or acid solution and filtering the washed one; adding an alkali aqueous solution to the filtered slurry to adjust the pH to be 2-9; and washing the solution with distilled water and an alcohol, filtering the washed one and drying the filtered one. Preferably the inorganic acid is HCl or HNO3; and the alkali halide is NaCl, KCl or NH4Cl.

Description

Preparation of TiO₂ ultrafine powders from titanium tetrachloride with inorganic acid solution by the advanced washing method

The present invention relates to a method for preparing crystalline TiO ₂ powder having a nano-sized, narrow particle size distribution using titanium tetrachloride (TiCl ₄ ) as an initial starting material.

Generally, titanium dioxide (TiO ₂ ) has a purity of 98% or less and a particle size of 3 μm or more in high-tech industries such as paint, ink, paper, enamel and porcelain pigment, titanium oxide magnetic, glass, cement, welding rod, titanium lead, etc. Although it has been used, in recent years, in order to be used in MLCCs, capacitors, piezoelectrics, thermistors, sensors, and photocatalysts of high-performance electronic ceramics, an ultrafine powder having a purity of 99% or more and a particle size distribution of 0.1 to 1.0 µm is required. Particularly used for photo catalyst, photo-electrode, and semiconductor is classified as the optimum particle size for designing nano composite when 0.01 ~ 0.2 ㎛, and the particle size distribution range of powder should be narrow to improve semiconductor properties, scattering and refraction characteristics. It is known to be excellent.

The production method of titanium dioxide can be largely divided into sulfuric acid method and chlorine method.

The sulfuric acid method has a long history, and the manufacturing method is also in the stabilization stage, dissolving the dried and pulverized ilmenite with sulfuric acid, separating the insoluble residue and the titanyl sulfate solution during the dissolution process, and calcining process. In the hydrolysis process, the basic basic properties of TiO ₂ particles are determined. On the other hand, more than 50% of the TiO ₂ currently produced is manufactured by such a sulfuric acid method, the reaction formula for each unit is as follows.

① Dissolution process: FeOTiO ₂ + 2H ₂ SO ₄ = TiOSO ₄ + FeSO ₄ + 2H ₂ O (1)

② Hydrolysis Process: TiOSO ₄ + mH ₂ O = TiO ₂ ㆍ nH ₂ O + H ₂ SO ₄ (2)

③ Firing process: TiO ₂ ㆍ nH ₂ O = TiO ₂ + nH ₂ O (3)

The chlorine method can be easily purified by distillation because the starting point is TiCl _4, which has a relatively low boiling point. The chlorine method has the advantages of uniform particles and easy process continuity and automation. Due to the risk of the use of expensive equipment that maintains confidentiality is required and there is a disadvantage that is not rich in raw materials

In addition, the TiO ₂ ultra-fine particles are manufactured using the sol-gel method, the gas phase method, the wet method and the thermal hydrolysis method, and the development of an efficient and mass-produced manufacturing method is actively underway in Korea. In Japanese Patent Application Laid-Open No. 4-280816, a method of preparing TiO ₂ by a known liquid phase method, a reaction solution formed by adding a titanium tetrachloride solution to an aqueous alkali solution prepared by adding basic organic carboxylic acid or the like is filtered, washed with water and suspended in water. An alkali metal hydroxide is added to the aqueous solution and treated at a temperature of pH 8 or higher and 50 ° C. to form an alkaline titanate solution. The solution is filtered again, washed with water, and then, acid is added to the suspended aqueous solution and neutralized with alkali metal titanate at a pH of 3 or less and a temperature of 50 ° C or higher. Finally, a method of preparing titanium dioxide was proposed through a post-treatment process in which the solution was filtered, washed with water and dried. In addition, Korean Patent Publication No. 91-9589 proposes a method for producing anatase and nearly cubic titanium dioxide by hydrolyzing TiOCl ₂ by heating TiOCl ₂ -containing solution under pressurized conditions in which fluorine ions and nuclei exist. However, this method has a problem in that it is difficult to manage the process in manufacturing and requires a lot of equipment cost and operation cost because the reaction is performed at high temperature and high pressure.

In Korean patent (Registration No.:10-0285210, Application No.:10-1999-0013284), ice or ice water is added to titanium tetrachloride to form an unstable hydroxide first, and then water is added to dissolve the hydroxide to increase the Ti ⁴⁺ concentration. A titanyl chloride (TiOCl ₂ ) aqueous solution of 0.15 to 1.2 M was prepared, and TiO ₂ slurry was prepared at 65 ° C. or lower by adding ammonia water with ultrasonic stirring. The slurry thus prepared was washed with an aqueous alkali halide solution of 0.1 M or more and filtered to provide a method for preparing rutile TiO ₂ ultrafine powder. However, this method is complicated by the first step of adding titanium or tetrachloride to ice or ice water to form unstable hydroxide to make titanyl chloride (TiOCl ₂ ) and then reacting by adding a small amount of distilled water to the solution. It takes a long time to manufacture, and has a relatively large disadvantage of TiCl ₄ loss in the preparation of hydroxide. In addition, an aqueous alkali halide (NaCl, KCl) solution of 0.1 M or more was used to prevent peptizing of the precipitate in the washing process, but a large amount of aqueous alkali halide solution is necessary to make the slurry neutral without peptising of the precipitate. do.

Therefore, the inventors have developed an improved manufacturing process as a result of research to solve the problems of the ultra-fine rutile titanium dioxide powder manufacturing method described above in the Republic of Korea patent (Registration No.:10-0285210, Application No.:10-1999-0013284) (Patent Application 10-2001-0018426) was filed. However, this method has an advantage of easily preparing a Ti ⁴⁺ aqueous solution, but has a disadvantage of maintaining a low temperature. In addition, in order to make the process more efficient, the production rate of TiO ₂ slurry needs to be improved and the process of washing with water is improved. As well as possible, the present invention has been developed by developing a process in which the production rate of TiO ₂ slurry is increased and the washing process is significantly improved. This way, insert the titanium tetrachloride (TiCl ₄₎ in a reactor filled with an inert gas at room temperature, the inorganic acid of 0.01~90% (HCl, HNO _3, etc.) was added to a mixture of mineral acid is added to the stoichiometric ratio than Ti ^{4 +} Prepare an aqueous solution. A solution of inorganic acid (HCl, HNO _3, etc.) of 0.01-90% was added to the prepared solution to prepare a Ti ⁴⁺ aqueous solution in a concentration range of 0.1-1.4 M, and then left at 15 ° C. to 200 ° C. to obtain TiO ₂ particles. Obtain the resulting slurry. The slurry was filtered and washed with an alkali halide (NaCl, KCl, NH ₄ Cl, etc.) or an acidic solution, and an alkaline aqueous solution was added to prepare a slurry having a pH range of 2-9. The slurry filtrate thus prepared is washed with distilled water and alcohol again and then filtered and dried to produce crystalline TiO ₂ powder. This method is a solution of Ti ⁴⁺ aqueous solution due to the rapid reaction of inorganic acid and raw material at room temperature rather than low temperature in a reactor filled with an inert gas than the method proposed in the patent (patent application 10-2001-0018426) filed by the present inventors. Because of the production, the loss of titanium tetrachloride (TiCl ₄ ) is insignificant, and has many advantages in terms of manufacturing method and manufacturing time. In addition, since the inorganic acid aqueous solution is used in the dilution step of the Ti ⁴⁺ aqueous solution, the production rate is significantly increased in the TiO ₂ slurry production step compared to the process using the distilled water without the inorganic acid, and the washing process of the finally obtained powder is improved. It is an excellent manufacturing method with the advantage of producing crystalline TiO ₂ powder of nanometer size efficiently without grinding process.

The technical problem to be achieved by the present invention is to prepare crystalline titanium dioxide (TiO ₂ ), the reaction time of the production time by rapidly reacting the inorganic acid and titanium tetrachloride (TiCl ₄ ) at room temperature by filling the reactor with an inert gas during the initial reaction Minimization of shortening and loss of titanium tetrachloride (TiCl ₄ ), shortening the production time of TiO ₂ slurry to increase the efficiency of the manufacturing process, developing an effective washing process to apply to the process nanometer (nano) It is to provide an excellent manufacturing method to obtain crystalline TiO ₂ powder of meter) size.

FIG. 1 is an X-ray diffraction line of TiO ₂ powder prepared by adding 0.1M HCl to an aqueous Ti ⁴⁺ solution mixed with HCl at 60 ° C. FIG.

FIG. 2 is a TEM photograph of TiO ₂ powder prepared by adding 0.1M HCl to a Ti ⁴⁺ aqueous solution mixed with HCl at 60 ° C. FIG.

3 is an EDX analysis result of TiO ₂ powder prepared by adding 0.1M HCl to an aqueous Ti ⁴⁺ solution mixed with HCl at 60 ° C.

FIG. 4 is an X-ray diffraction line of TiO ₂ powder prepared by adding 0.5M HNO ₃ to a Ti ⁴⁺ aqueous solution mixed with HCl at 60 ° C. FIG.

The present invention for achieving the above object relates to a method for efficiently preparing the crystalline titanium dioxide in solution state using a titanium tetrachloride (TiCl ₄ ) as the initial starting material crystalline TiO of the nanometer (nano meter) size ₂ relates to an excellent method for producing a powder.

Specific manufacturing method of crystalline titanium dioxide (TiO ₂ ) according to the present invention,

(1) After adding titanium tetrachloride (TiCl ₄ ) to a reactor filled with an inert gas at room temperature, 0.01 to 90% of an inorganic acid (HCl, HNO _3, etc.) solution was added at a stoichiometric ratio or higher to mix Ti ⁴ with an inorganic acid. ⁺ Preparing an aqueous solution (first step)

(2) preparing a Ti ⁴⁺ aqueous solution having a concentration range of 0.1 to 1.4 M by adding 0.01 to 90% of an inorganic acid (HCl, HNO _3, etc.) solution to the first step solution at room temperature (second step)

(3) leaving the dilution solution of the second step at a temperature range of 15 ° C. to 200 ° C. to obtain a slurry in which TiO ₂ particles are produced (third step)

(4) filtering the slurry of the third step, followed by washing with an alkaline halide (NaCl, KCl, NH ₄ Cl, etc.) or an acidic solution and filtering (fourth step)

(5) adding alkaline aqueous solution to the slurry filtrate of the fourth step to adjust the pH to the range 2-9 (step 5)

(6) The fifth step is a method for producing crystalline TiO ₂ powder of nanometer size consisting of a step of washing with distilled water and alcohol, followed by filtration and drying (sixth step).

Here, the inorganic acid aqueous solution of the first and second steps is preferably composed of HCl, HNO ₃ and the like, the aqueous alkali solution of the fourth step is preferably added a non-metal hydroxide such as NaOH, KOH, NH ₄ OH, At this time, it is preferable to adjust the acid concentration to pH 2-9 range.

The following examples are intended to illustrate the invention and should not be understood as limiting the scope of the invention.

<Example 1> Preparation of ultrafine titanium dioxide powder using HCl solution

Titanium tetrachloride (TiCl ₄ ), which is a starting material at room temperature, was placed in a reactor filled with an inert gas, and then 5M HCl solution was added with stirring to prepare a 2M aqueous Ti ⁴⁺ solution containing HCl. By the addition of 0.1M HCl solution to the prepared solution at room temperature was diluted to be a 0.7M concentration of the Ti ⁴⁺ and the mixture was stirred for 30 minutes. The diluted solution was left at 60 ° C. for 4 hours to prepare a TiO ₂ slurry. The prepared slurry was filtered and then washed with 1M NaCl solution. 1M aqueous NaOH solution was added to the slurry filtrate and the mixture was washed with water, and pH was properly adjusted and then filtered. The slurry filtrate was washed with distilled water and alcohol solution, filtered and dried to obtain TiO ₂ powder. The X-ray diffraction line of the prepared titanium dioxide is shown in FIG. 1, wherein the powder was a powder having a nanometer size of rutile (Rutile). In addition, Figure 2 is a TEM image of the TiO ₂ powder, the average secondary particle size was 0.25 ㎛. 3 shows that Ti and O are present in a stoichiometric ratio as the EDX analysis data of the powder, and no impurities are present.

<Example 2> Preparation of Ultrafine Titanium Dioxide Powder Using HNO ₃ Solution

Titanium tetrachloride (TiCl ₄ ) as a starting material was added to a reactor filled with an inert gas at room temperature, and then 7M HNO ₃ solution was added while stirring to prepare a 2M Ti ⁴⁺ aqueous solution in which HCl and HNO ₃ solution were mixed. The prepared solution was diluted to a concentration of Ti ⁴⁺ to 1.0M by adding 0.5M HNO ₃ solution at room temperature and stirred for 25 minutes. The diluted solution was left at 60 ° C. for 2 hours to prepare a TiO ₂ slurry. The prepared slurry was filtered and washed with 1M of CH ₃ COOH solution and washed. 1M aqueous KOH solution was added to the slurry filtrate, and the mixture was washed with water, and pH was adjusted. The slurry filtrate was washed with distilled water and alcohol solution, filtered and dried to obtain TiO ₂ powder. The X-ray diffraction line of the ultrafine titanium dioxide prepared at this time is as shown in FIG. 4, and the powder was a powder having a nanometer size of rutile (Rutile).

As described above, in the preparation method of the present invention, since titanium tetrachloride (TiCl ₄ ) is reacted with an inorganic acid in an aqueous solution state while inert gas is injected into a reactor that can be stirred at room temperature, not only the amount of raw material loss is small but also TiO _2. By shortening the slurry production time and developing an effective washing process, it is possible to produce nanometer-sized crystalline TiO ₂ powder that does not require grinding process, and requires a device to be fired at a high temperature atmosphere. As it is possible to mass-produce and lower production costs, it will expand the marketability of TiO ₂ nano powders as a very practical manufacturing method.

Claims (7)

(1) After adding titanium tetrachloride (TiCl ₄ ) to a reactor filled with an inert gas at room temperature, 0.01 to 90% of an inorganic acid (HCl, HNO _3, etc.) solution was added at a stoichiometric ratio or higher to mix Ti ⁴ with an inorganic acid. ⁺ Preparing an aqueous solution (first step) (2) adding an aqueous solution of 0.01 to 90% inorganic acid (HCl, HNO _3, etc.) to the first step solution at room temperature to prepare a Ti ⁴⁺ aqueous solution in a concentration range of 0.1 to 1.4 M (second step) (3) leaving the dilution solution of the second step at a temperature range of 15 ° C. to 200 ° C. to obtain a slurry in which TiO ₂ particles are produced (third step) (4) filtering the slurry of the third step, followed by washing with an alkaline halide (NaCl, KCl, NH ₄ Cl, etc.) or an acidic solution and filtering (fourth step) (5) adding an aqueous alkali solution to the slurry filtrate of the fourth step to adjust the pH to the range of 2-9 (step 5) (6) Method of manufacturing ultra-fine crystalline TiO ₂ powder of nanometer size consisting of the step 5 washed with distilled water and alcohol and then filtered and dried (sixth step) The inert gas of claim 1, wherein a mixture of a mixture of nitrogen (N ₂ ), argon (Ar), nitrogen (N ₂ ), and argon (Ar) is preferably 99.9% or more. As a method for producing a nanometer sized crystalline TiO ₂ powder, characterized in that the use of a pure component gas and a mixed gas thereof do not chemically react with the reactants in the reactor The nanometer size according to claim 1, wherein when titanium tetrachloride (TiCl ₄ ) and an inorganic acid are added to prepare a Ti ⁴⁺ aqueous solution, a nanometer size is prepared using a batch or a continuous reactor. Of crystalline TiO ₂ powder (1) and (2), the concentration of the inorganic acid solution is preferably added in the range of 0.01 to 90%, it is preferable to use HCl, HNO ₃ and the like as the inorganic acid material, other inorganic acid material Method for producing a crystalline TiO ₂ powder of nanometer size characterized in that it comprises a The method of claim 1 (4), which is washed with an alkaline halide or an acidic solution and filtered. The aqueous halide solution is preferably an aqueous solution of 0.1 M or more composed of NaCl, KCl, NH ₄ Cl, or the like, and all substances composed of other alkali halides. Include. In addition, the acidic solution is preferably an aqueous solution of 0.1M or more consisting of HCl, HNO ₃ , CH ₃ COOH and the like, crystalline TiO of nanometer size (nano meter) characterized in that to use all materials consisting of other acidic solution ₂ Preparation of Powder The aqueous alkali solution according to claim 1 (5) is preferably an aqueous solution composed of KOH, NaOH, NH ₄ OH, LiOH, or the like, and includes all substances composed of other alkalis. In addition, the method of producing a crystalline TiO ₂ powder of the nanometer (nano meter) size, characterized in that adjusted to the pH range 2-9 when the aqueous alkali solution is added. The method for producing a crystalline TiO ₂ powder having a nanometer size according to claim 1, which is washed with distilled water and alcohol, followed by filtration and drying.