Rutile-phase high-purity titanium dioxide as well as preparation method and application thereof

Abstract

The invention relates to the technical field of artificial lens synthesis, and particularly provides rutile-phase high-purity titanium dioxide and a preparation method and application thereof.The preparation method of the rutile-phase high-purity titanium dioxide comprises the steps that crude titanium tetrachloride and concentrated hydrochloric acid are mixed for co-distillation, and the crude titanium tetrachloride obtained after co-distillation is rectified to obtain titanium tetrachloride; hydrolyzing titanium tetrachloride in a protective atmosphere under an alkaline condition to generate titanium hydroxide; and cleaning and drying the titanium hydroxide, and calcining to obtain the rutile phase high-purity titanium dioxide. By adopting the preparation method provided by the invention, the rutile-phase titanium dioxide with the purity of 99.99% or above and the content of each impurity element of less than 1ppm is prepared.

Description

Technical Field

[0001] The invention relates to the technical field of artificial crystal synthesis, and in particular to rutile phase high-purity titanium dioxide and a preparation method and application thereof. Background Art

[0002] KTP (potassium titanate, chemical formula KTiOPO4) is an important optoelectronic functional crystal with excellent nonlinear optical and electro-optical properties, and is widely used in nonlinear optics and laser technology. KTP has good phase matching ability, high laser damage threshold, mechanical strength and thermal stability, good light transmittance between about 350nm and 4500nm, can be optically operated in multiple bands, has strong adaptability, has large nonlinear optical coefficient, excellent performance, wide acceptable angle, not easy to deliquesce, and light damage threshold can reach GW / cm 2 It has good thermal stability in terms of magnitude and phase matching and is currently one of the best materials for 1.06μm frequency doubling of small and medium power Nd:YAG lasers.

[0003] KTP crystals are widely used in medical, industrial processing, satellite ranging and laser indication, and are particularly important in the military field. Its key role in laser-guided weapon systems, lidar systems, and night vision and infrared imaging equipment fully demonstrates its value in modern military technology. As a frequency multiplication material for lasers, KTP crystals support guided weapons to achieve precision strikes in complex battlefield environments, while providing high-precision terrain detection and target identification, and enhancing detection capabilities. These characteristics make KTP crystals indispensable in military applications. The current mainstream preparation methods for KTP include hydrothermal method, solid phase synthesis method, Czochralski method (CZ method), etc. Hydrothermal growth is to dissolve the raw materials in a solution under high temperature and high pressure until KTP crystals are formed, and usually higher quality crystals can be obtained in a shorter time. At present, although my country has overcome the growth problem of large-size, high-ash-resistance, and high-resistivity KTP crystals using TiO2 and KH2PO4 as raw materials and the hydrothermal method, the purity of the raw material titanium dioxide has a great influence on the crystal performance. At present, there is no mature preparation method for rutile phase titanium dioxide with a purity of more than 99.99% and an impurity element content of less than 1ppm.

[0004] In view of the above shortcomings, the present invention is proposed. Summary of the invention

[0005] The main purpose of the present invention is to provide a rutile phase high-purity titanium dioxide and its preparation method and application. The preparation method provided by the present invention is used to prepare rutile phase titanium dioxide with a purity of more than 99.99% and a content of each impurity element less than 1ppm.

[0006] The first aspect of the present invention provides a method for preparing rutile phase high-purity titanium dioxide, the preparation method comprising: mixing crude titanium tetrachloride and concentrated hydrochloric acid for co-distillation to remove part of the metal ions in the crude titanium tetrachloride; rectifying the crude titanium tetrachloride obtained after the co-distillation to obtain titanium tetrachloride with a purity of more than 99.99%; hydrolyzing the titanium tetrachloride under a protective atmosphere and alkaline conditions to generate titanium hydroxide; and washing and drying the titanium hydroxide and then calcining to obtain the rutile phase high-purity titanium dioxide.

[0007] In some embodiments of the present invention, in the co-distillation, the molar ratio of the crude titanium tetrachloride to the hydrochloric acid is 1:(0.3-0.35).

[0008] In some embodiments of the present invention, in the co-distillation, the distillation pressure is 0.09 MPa to 0.1 MPa, the distillation temperature is 105° C. to 110° C., and the recovery rate of the crude titanium tetrachloride is ≥85%.

[0009] In some embodiments of the present invention, the metal ions include at least one of iron, chromium, vanadium, manganese, cobalt, and nickel.

[0010] In some embodiments of the present invention, during the distillation, the liquid level in the distillation tower bottom is 45% to 60%, the crude titanium tetrachloride flow rate is 2 L / min to 2.6 L / min, and the tower diameter ratio is 12 to 15.

[0011] In some embodiments of the present invention, the distillation temperature is 145° C. to 150° C., and the reflux ratio is 1.7 to 1.9.

[0012] In some embodiments of the present invention, the distillation time is 30 h to 40 h.

[0013] In some embodiments of the present invention, the hydrolysis of titanium tetrachloride comprises: slowly injecting the titanium tetrachloride into an alkaline aqueous solution, performing a hydrolysis reaction under stirring conditions, and then performing solid-liquid separation to obtain titanium hydroxide with a solid content of ≥85%.

[0014] In some embodiments of the present invention, the pH value of the alkaline aqueous solution is 10-14.

[0015] In some embodiments of the present invention, the stirring speed is 1000 rpm to 2000 rpm.

[0016] In some embodiments of the present invention, the volume ratio of the alkaline aqueous solution to the titanium tetrachloride is 2.2:1 to 2.5:1.

[0017] In some embodiments of the present invention, the injection flow rate of the titanium tetrachloride is 3 L / min to 5 L / min.

[0018] In some embodiments of the present invention, the temperature of the hydrolysis reaction is 40° C. to 60° C., and the time is 20 min to 30 min.

[0019] In some embodiments of the present invention, the drying adopts a high-efficiency boiling dryer, wherein the inlet air temperature is 155°C to 170°C, the tower temperature is 140°C to 145°C, the outlet air temperature is 120°C to 125°C, and the drying time is 1.5h to 3h.

[0020] In some embodiments of the present invention, the calcination temperature is 850°C to 950°C.

[0021] In some embodiments of the present invention, the calcination time is more than 3 hours based on per kilogram of titanium hydroxide.

[0022] In some embodiments of the present invention, clean anhydrous air is introduced during the calcination process to ensure sufficient calcination.

[0023] The second aspect of the present invention provides a rutile phase high-purity titanium dioxide, which is prepared by the preparation method described in the first aspect; wherein the purity of the rutile phase high-purity titanium dioxide is greater than 99.99%, and has a unique rutile crystal phase.

[0024] The third aspect of the present invention provides a use of the rutile phase high-purity titanium dioxide described in the second aspect or the rutile phase high-purity titanium dioxide prepared by the preparation method described in the first aspect in KTP crystal synthesis.

[0025] Beneficial effects of the present invention:

[0026] In the present invention, concentrated hydrochloric acid is used as a washing liquid for titanium tetrachloride, and a distillation device and a process are designed to meet the purity requirements by combining distillation and rectification, and the generation of impurities in the hydrolysis process is controlled, so that impurities in crude titanium tetrachloride are effectively removed, and the metal ion content is reduced to below 1ppm, thereby obtaining high-purity titanium dioxide, which is a key raw material for synthesizing KTP crystals with rutile as the only crystal phase.

[0027] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only used for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. In the accompanying drawings:

[0029] Figure 1 The XRD spectrum of the rutile phase high-purity titanium dioxide for KTP crystals prepared in Example 1 of the present invention;

[0030] Figure 2 The present invention is a flow chart for preparing high-purity titanium dioxide in rutile phase according to one embodiment or multiple embodiments. DETAILED DESCRIPTION

[0031] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concept of the present invention.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" in the specification and claims of the present invention and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0033] In the description of the embodiments of the present invention, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present invention, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0034] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0035] In the description of the embodiments of the present invention, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0036] In the description of the embodiments of the present invention, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0037] Rutile TiO2 is the main product of titanium series and one of the key raw materials for synthesizing high-performance KTP crystals. It plays a vital role in the synthesis and performance optimization of KTP. As a dopant, rutile TiO2 can significantly improve the nonlinear optical properties of KTP crystals and enhance their efficiency in the process of laser frequency multiplication. TiO2 has fine particles, large specific surface area, high purity and few impurities. It has a high refractive index for light, stable thermal effects on light, stable physical and chemical properties, and excellent optical and electrical properties such as high resistance to reduction, high dielectric constant and resistance. The introduction of rutile TiO2 improves the crystal structure stability of KTP and improves its thermal stability and damage resistance. This makes TiO2-doped KTP crystals perform well in high-power laser applications and can better meet the high requirements of modern optoelectronic devices for material performance.

[0038] The material purity and crystal phase of rutile TiO2 are key indicators that affect the performance of KTP crystals. The rutile TiO2 lattice is small and stable, and has the characteristics of high dielectric constant, high density, high refractive index, and excellent electrical properties. At present, rutile is the only crystal phase, and the purity of rutile high-purity titanium dioxide with a purity of at least 99.99% (iron, chromium, vanadium, manganese, cobalt, nickel, etc. are all less than 1ppm) is still not mature in the market. Therefore, it is of great significance to prepare the above-mentioned high-purity titanium dioxide and improve the performance of KTP crystals.

[0039] The invention provides a method for preparing rutile phase high-purity titanium dioxide, the key of which is to obtain high-purity rutile titanium dioxide through purification, hydrolysis and calcination of crude titanium tetrachloride (purity ≥ 95%).

[0040] See also Figure 2 As shown, the preparation method of rutile phase high-purity titanium dioxide in the present invention is specifically carried out according to the following steps.

[0041] Distillation

[0042] In an embodiment of the present invention, crude titanium tetrachloride is mixed with concentrated hydrochloric acid for co-distillation to remove part of metal ions in the crude titanium tetrachloride.

[0043] In some embodiments of the present invention, in the co-distillation, the molar ratio of crude titanium tetrachloride to hydrochloric acid is 1:(0.3-0.35). For example, the molar ratio of crude titanium tetrachloride to hydrochloric acid can be one of 1:0.3, 1:0.31, 1:0.32, 1:0.33, 1:0.34, 1:0.35 or any value satisfying the above range.

[0044] In some embodiments of the present invention, in the co-distillation, the distillation pressure is 0.09 MPa-0.1 MPa, the distillation temperature is 105° C.-110° C., and the recovery rate of crude titanium tetrachloride is ≥85%.

[0045] The distillation pressure of the crude titanium tetrachloride and hydrochloric acid mixture provided by the present invention can be one of 0.09MPa, 0.1MPa or any value satisfying the above range. The distillation temperature of the crude titanium tetrachloride and hydrochloric acid mixture provided by the present invention can be one of 105°C, 110°C or any value satisfying the above range.

[0046] In some embodiments of the present invention, the metal ions include at least one of iron, chromium, vanadium, manganese, cobalt, and nickel.

[0047] In some embodiments of the present invention, the purity of the crude titanium tetrachloride is above 95%.

[0048] In some embodiments of the present invention, a clean corrosion-resistant container is placed in an ice-water bath, concentrated hydrochloric acid is added, and crude titanium tetrachloride with a purity of about 95% or more is slowly injected into the concentrated hydrochloric acid for mixing, and the volume ratio of crude titanium tetrachloride to concentrated hydrochloric acid is 1:(0.3-0.35); the mixed solution is co-distilled to remove part of the metal ions in the crude titanium tetrachloride, wherein the metal ions include at least one of iron, chromium, vanadium, manganese, cobalt, and nickel; the distillation pressure of the crude titanium tetrachloride and hydrochloric acid mixture is 0.09MPa-0.1MPa, the distillation temperature is 105°C-110°C, the titanium tetrachloride recovery rate is ≥85%, and the distilled residual liquid is recovered and then distilled.

[0049] Distillation

[0050] In an embodiment of the present invention, the crude titanium tetrachloride obtained after co-distillation is rectified to obtain titanium tetrachloride with a purity of more than 99.99%.

[0051] In an embodiment of the present invention, the crude titanium tetrachloride obtained after co-distillation is added to the bottom of a distillation tower, and distillation is performed after adjusting the pressure and temperature to increase the purity to more than 99.99%.

[0052] In some embodiments of the present invention, the distillation is carried out under a protective atmosphere, such as introducing high-purity argon gas and ensuring a sealed operation to prevent the titanium tetrachloride from being hydrolyzed in contact with the outside air.

[0053] In some embodiments of the present invention, during distillation, the liquid level in the bottom of the distillation tower is 45% to 60%, the flow rate of crude titanium tetrachloride is 2 L / min to 2.6 L / min, and the tower diameter ratio is 12 to 15.

[0054] The liquid level of the distillation tower provided by the present invention can be one of 45%, 48%, 50%, 52%, 55%, 58%, 60% or any value that meets the above range. The crude titanium tetrachloride flow rate provided by the present invention can be one of 2L / min, 2.1L / min, 2.2L / min, 2.3L / min, 2.4L / min, 2.5L / min, 2.6L / min or any value that meets the above range. The tower diameter ratio of the distillation tower provided by the present invention can be one of 12, 13, 14, 15 or any value that meets the above range.

[0055] In some embodiments of the present invention, the distillation temperature is 145° C. to 150° C. For example, the distillation temperature can be 145° C., 150° C., or any value satisfying the above range.

[0056] In some embodiments of the present invention, the reflux ratio of the distillation is 1.7 to 1.9. For example, the reflux ratio can be one of 1.7, 1.8, 1.9 or any value satisfying the above range.

[0057] In some embodiments of the present invention, the distillation time is 30 hours to 40 hours. For example, the distillation time can be one of 30 hours, 31 hours, 32 hours, 33 hours, 34 hours, 35 hours, 36 hours, 37 hours, 38 hours, 39 hours, and 40 hours, or any value that satisfies the above range.

[0058] In some embodiments of the present invention, a plate distillation tower is used for distillation, the tower diameter ratio is 12-15, high-purity argon is introduced into the tower and the distillation tower is sealed to prevent titanium tetrachloride from being hydrolyzed by contact with external air.

[0059] In some embodiments of the present invention, the crude titanium tetrachloride obtained by distillation is added to the bottom of a plate distillation tower, and distillation is performed after adjusting the pressure and temperature. The tower diameter ratio is 12 to 15, the liquid level of the bottom of the distillation tower is controlled at 45% to 60%, the crude titanium tetrachloride flow rate is 2 L / min to 2.6 L / min, the distillation temperature is 145° C. to 150° C., the reflux ratio is 1.7 to 1.9, and the distillation time is 30 h to 40 h. Titanium tetrachloride with a purity of more than 99.99% is obtained in the reflux tank.

[0060] hydrolysis

[0061] In some embodiments of the present invention, the titanium tetrachloride obtained after distillation is hydrolyzed under a protective atmosphere and alkaline conditions to generate titanium hydroxide.

[0062] In some embodiments of the present invention, under a protective atmosphere, a titanium tetrachloride solution is slowly injected into an alkaline aqueous solution, and a hydrolysis reaction is carried out under stirring conditions, followed by solid-liquid separation to obtain titanium hydroxide with a solid content of ≥85%.

[0063] In some embodiments of the present invention, the entire hydrolysis process is protected by a high-purity inert clean gas, such as argon or nitrogen.

[0064] In some embodiments of the present invention, the pH value of the alkaline aqueous solution is 10-14.

[0065] In some embodiments of the present invention, a soluble alkaline substance, such as sodium carbonate, potassium hydroxide or sodium hydroxide, is added to pure water and stirred to obtain an alkaline aqueous solution with a pH value of 10 to 14.

[0066] In some embodiments of the present invention, stirring is continued throughout the hydrolysis process, and the stirring speed is 1000 rpm to 2000 rpm. For example, the stirring speed can be one of 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm, 2000 rpm, or any value satisfying the above range.

[0067] In some embodiments of the present invention, the volume ratio of the alkaline aqueous solution to titanium tetrachloride is 2.2: 1 to 2.5: 1. For example, the volume ratio of the alkaline aqueous solution to titanium tetrachloride can be one of 2.2: 1, 2.3: 1, 2.4: 1, 2.5: 1 or any value satisfying the above range.

[0068] In some embodiments of the present invention, the injection flow rate of titanium tetrachloride is 3L / min to 5L / min. For example, an automatic titration device can be used to ensure that the hydrolysis process is stable and balanced. Exemplarily, the injection flow rate of titanium tetrachloride can be one of 3L / min, 4L / min, 5L / min, or any value that satisfies the above range.

[0069] In some embodiments of the present invention, the temperature of the hydrolysis reaction is 40°C to 60°C, and the time is 20min to 30min. Exemplarily, after the titanium tetrachloride is injected, stirring is continued for 20 to 30 minutes and then allowed to stand until all the precipitated solids are precipitated to the bottom of the container. The temperature of the hydrolysis reaction provided by the present invention may be one of 40°C, 45°C, 50°C, 55°C, 60°C or any value satisfying the above range value. The time of the hydrolysis reaction provided by the present invention may be one of 20min, 21min, 22min, 23min, 24min, 25min, 26min, 27min, 28min, 29min, 30min or any value satisfying the above range value.

[0070] In an embodiment of the present invention, the hydrolysis reaction is carried out under stirring conditions, and the target crystalline titanium hydroxide and titanium dioxide are obtained by controlling the hydrolysis temperature and the pH value of the alkaline aqueous solution.

[0071] In some embodiments of the present invention, the hydrolysis reaction of titanium tetrachloride comprises the following steps: adding pure water to a corrosion-resistant container, and then adding an alkaline solution and slowly stirring to obtain an alkaline aqueous solution, and stirring continues throughout the hydrolysis process at a speed of 1000 rpm to 2000 rpm; slowly injecting the titanium tetrachloride solution into the alkaline aqueous solution for hydrolysis, and after the injection is completed, continuing to stir for 20 to 30 minutes and then standing until all the precipitated solids are precipitated to the bottom of the container.

[0072] Cleaning

[0073] In an embodiment of the present invention, the titanium hydroxide generated by hydrolysis is washed with pure water for multiple times, and then solid-liquid separation is performed using a centrifuge to obtain titanium hydroxide with a solid content of ≥85%.

[0074] dry

[0075] In the embodiment of the present invention, a high-efficiency fluidized bed dryer is used for drying, wherein the inlet air temperature is 155°C to 170°C, the tower body (working room) temperature is 140°C to 145°C, the outlet air temperature is 120°C to 125°C, and the drying time is 1.5h to 3h.

[0076] The air inlet temperature provided by the present invention can be one of 155°C, 160°C, 165°C, 170°C or any value satisfying the above range. The air outlet temperature provided by the present invention can be one of 120°C, 125°C or any value satisfying the above range. The tower body temperature provided by the present invention can be one of 140°C, 145°C or any value satisfying the above range. The drying time provided by the present invention can be one of 1.5h, 1.8h, 2h, 2.2h, 2.5h, 2.8h, 3h or any value satisfying the above range.

[0077] Calcination

[0078] In the embodiment of the present invention, the titanium hydroxide filter cake is dried and then calcined to obtain rutile phase high-purity titanium dioxide.

[0079] In an embodiment of the present invention, the calcination temperature is 850° C. to 950° C. For example, the calcination temperature may be one of 850° C., 900° C., 950° C., or any value satisfying the above range.

[0080] In the embodiment of the present invention, the calcination time is more than 3 hours based on one kilogram of titanium hydroxide.

[0081] In the embodiment of the present invention, clean anhydrous air is introduced during the calcination process to ensure sufficient calcination.

[0082] In an embodiment of the present invention, clean air without metal impurities is introduced during the calcination process to ensure sufficient calcination without introducing new impurities. The calcination temperature needs to reach 850°C to 950°C, and the calcination time of 1 kg of titanium hydroxide is at least 3 hours. After cooling, the titanium dioxide with rutile as the only crystal phase and purity >99.99% (the contents of iron, chromium, vanadium, manganese, cobalt, nickel, etc. are all less than 1 ppm) is obtained by testing.

[0083] The present invention also provides a rutile phase high-purity titanium dioxide, which is prepared by the above-mentioned preparation method; wherein the purity of the rutile phase high-purity titanium dioxide is greater than 99.99%, and has a unique rutile crystal phase.

[0084] The rutile phase high-purity titanium dioxide provided by the invention is applied in KTP crystal synthesis.

[0085] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The experimental reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the raw materials, instruments and equipment used in the following examples, etc., can all be purchased on the market or can be obtained by existing methods; the amounts of the experimental reagents, unless otherwise specified, are the amounts of reagents used in conventional experimental operations; the experimental methods, unless otherwise specified, are all conventional methods.

[0086] Example 1

[0087] A method for preparing rutile high-purity titanium dioxide for KTP crystals is as follows:

[0088] Place a clean corrosion-resistant container in an ice water bath, add concentrated hydrochloric acid, slowly inject crude titanium tetrachloride with a purity of about 98% or more into the concentrated hydrochloric acid for mixing, and the volume ratio of crude titanium tetrachloride to concentrated hydrochloric acid is 1:0.35; remove part of the metal ions in the crude titanium tetrachloride by co-distillation of the mixed solution; the distillation pressure of the crude titanium tetrachloride and hydrochloric acid mixed solution is 0.1MPa, the distillation temperature is 110°C, the titanium tetrachloride recovery rate is ≥85%, and the distillation residue is collected and returned to the initial step for further distillation.

[0089] A plate distillation tower is used for distillation, with a tower diameter ratio of 15. High-purity argon is introduced into the tower and the distillation tower is sealed to prevent titanium tetrachloride from being hydrolyzed by contact with the outside air. The crude titanium tetrachloride obtained after distillation is added to the bottom of the plate distillation tower, and distillation is carried out after adjusting the pressure and temperature. The liquid level of the bottom of the distillation tower is controlled at 60%, the flow rate is 2.6L / min, the distillation temperature is 150°C, the reflux ratio is 1.9, the distillation time is 40h, and titanium tetrachloride with a purity of more than 99.99% is obtained in the reflux tank.

[0090] The titanium tetrachloride after distillation is hydrolyzed to generate titanium hydroxide. A high-purity inert clean gas argon or nitrogen is introduced into a corrosion-resistant container to prevent titanium tetrachloride from reacting with moisture in the air. Then pure water is added to the container, and then sodium hydroxide, a soluble alkaline substance, is slowly stirred to obtain an alkaline aqueous solution with a pH value of 10. The stirring continues throughout the hydrolysis process at a speed of 2000rpm; the titanium tetrachloride solution is slowly injected into the alkaline aqueous solution for hydrolysis at a flow rate of 3L / min. An automatic titration device is used to ensure that the hydrolysis process is stable and balanced, and the generation of impurities is controlled. An online pH meter is used to monitor the alkalinity. The volume ratio of pure water to titanium tetrachloride is controlled at 2.3:1. After the injection is completed, continue to stir for 30 minutes and then stand until all the precipitated solids are precipitated to the bottom of the container. Since this process is an exothermic reaction, cooling water needs to be introduced into the container to keep the hydrolysis temperature at 60°C.

[0091] The solid precipitate is sieved and washed with pure water for multiple times, and then the solid-liquid separation is performed using a centrifuge to obtain a titanium hydroxide filter cake with a solid content ≥ 80%; the filter cake is dried in a high-efficiency boiling dryer, wherein the inlet air temperature is 170°C, the tower temperature is 145°C, the outlet air temperature is 125°C, and the drying time is 1.5h.

[0092] After the titanium hydroxide filter cake is dried, it is calcined. During the process, clean air without metal impurities needs to be introduced to ensure sufficient calcination and no new impurities are introduced. The calcination temperature reaches 900°C, and the calcination time of 1 kg of titanium hydroxide is at least 3 hours. After cooling, the titanium dioxide with rutile as the only crystal phase and purity > 99.99% (the content of iron, chromium, vanadium, manganese, cobalt, nickel, etc. is less than 1ppm) is obtained by testing. Figure 1 The impurity content of the sample in Example 1 is shown in Table 1.

[0093] Table 1. Impurity content of titanium dioxide obtained in Example 1

[0094] element Actual content ppm element Actual content ppm Ca / Fe 0.46 Sc / Co 0.097 Ti Matrix Ni 0.034 V 0.9 Cu / Cr 0.88 Zn / Mn 0.027

[0095] Note: 1ppm means the content is one part per million.

[0096] In the present invention, a distillation device and process that meet the purity requirements are designed by combining distillation and rectification, and the generation of impurities in the hydrolysis process is controlled, so that impurities in crude titanium tetrachloride are effectively removed, the metal ion content is reduced to below 1 ppm, and high-purity titanium dioxide, a key raw material for the synthesis of KTP crystals with rutile as the only crystal phase, is obtained.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in each embodiment can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for preparing rutile phase high-purity titanium dioxide, characterized in that: The preparation method comprises: Mixing crude titanium tetrachloride with concentrated hydrochloric acid for co-distillation to remove some metal ions in the crude titanium tetrachloride; The crude titanium tetrachloride obtained after the co-distillation is distilled to obtain titanium tetrachloride with a purity of more than 99.99%; The titanium tetrachloride is hydrolyzed under a protective atmosphere and alkaline conditions to generate titanium hydroxide; The titanium hydroxide is washed, dried, and then calcined to obtain the rutile phase high-purity titanium dioxide.

2. The method for preparing rutile phase high-purity titanium dioxide according to claim 1, characterized in that: In the co-distillation, the molar ratio of the crude titanium tetrachloride to the hydrochloric acid is 1:(0.3-0.35).

3. The method for preparing rutile phase high-purity titanium dioxide according to claim 1, characterized in that: In the co-distillation, the distillation pressure is 0.09MPa-0.1MPa, the distillation temperature is 105°C-110°C, and the recovery rate of the crude titanium tetrachloride is ≥85%; Preferably, the metal ions include at least one of iron, chromium, vanadium, manganese, cobalt and nickel.

4. The method for preparing rutile phase high-purity titanium dioxide according to claim 1, characterized in that: During the distillation, the liquid level of the distillation tower bottom is 45% to 60%, the crude titanium tetrachloride flow rate is 2L / min to 2.6L / min, and the tower diameter ratio is 12 to 15; Preferably, the distillation temperature is 145°C to 150°C, and the reflux ratio is 1.7 to 1.9; Preferably, the distillation time is 30 h to 40 h.

5. The method for preparing rutile phase high-purity titanium dioxide according to claim 1, characterized in that: The hydrolysis of titanium tetrachloride comprises: Slowly injecting the titanium tetrachloride into an alkaline aqueous solution, performing a hydrolysis reaction under stirring conditions, and then performing solid-liquid separation to obtain titanium hydroxide with a solid content of ≥85%; Preferably, the pH value of the alkaline aqueous solution is 10 to 14; Preferably, the stirring speed is 1000 rpm to 2000 rpm.

6. The method for preparing rutile phase high-purity titanium dioxide according to claim 5, characterized in that: The volume ratio of the alkaline aqueous solution to the titanium tetrachloride is 2.2:1 to 2.5:1; Preferably, the injection flow rate of titanium tetrachloride is 3L / min to 5L / min; Preferably, the hydrolysis reaction is carried out at a temperature of 40°C to 60°C and for a time of 20 min to 30 min.

7. The method for preparing rutile phase high-purity titanium dioxide according to claim 1, characterized in that: The drying adopts a high-efficiency boiling dryer, wherein the inlet air temperature is 155°C to 170°C, the tower body temperature is 140°C to 145°C, the outlet air temperature is 120°C to 125°C, and the drying time is 1.5h to 3h.

8. The method for preparing rutile phase high-purity titanium dioxide according to claim 1, characterized in that: The calcination temperature is 850°C to 950°C; Preferably, based on each kilogram of titanium hydroxide, the calcination time is more than 3 hours; Preferably, during the calcination process, clean anhydrous air is introduced to ensure sufficient calcination.

9. A rutile phase high-purity titanium dioxide, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8; wherein, The purity of the rutile phase high-purity titanium dioxide is greater than 99.99%, and it has a unique rutile crystal phase.

10. Use of the rutile phase high-purity titanium dioxide according to claim 9 or the rutile phase high-purity titanium dioxide prepared by the preparation method according to any one of claims 1 to 8 in KTP crystal synthesis.

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