Preparation method of rutile type titanium dioxide

Abstract

The invention relates to the technical field of chemical metallurgy, in particular to a preparation method of rutile type titanium dioxide. According to the method, Fe < 2 + > and Ti < 4 + > are released in the acidolysis process of the ilmenite, the Ti < 4 + > is hydrolyzed under the hydrochloric acid hydrothermal condition to generate TiO2.xH2O, and then the TiO2.xH2O is subjected to dehydration condensation to gradually form a TiO2 crystal nucleus. In a high-temperature and high-pressure hydrothermal environment, a rutile type crystal nucleus with thermodynamic stability is easier to form through induction. The coordination capability of Cl <-> in hydrochloric acid and Ti < 4 + > in ilmenite is relatively weak, and an acidic environment promotes a Ti < 4 + > hydrolysis product to tend to protonation condensation, so that generation of a rutile type precursor structure is facilitated, and then pure rutile type titanium dioxide is prepared. The preparation method has the advantages of simple steps, easily available raw materials and low cost, and is suitable for industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical metallurgy. More specifically, it relates to a method for preparing rutile titanium dioxide. Background Art

[0002] Titanium dioxide (TiO2), commonly known as titanium white powder, as a key inorganic chemical product, plays a crucial role in multiple industrial fields. It mainly exists in two crystal forms, anatase and rutile. In addition, there is also brookite, but brookite has poor stability and lacks practical value in industrial applications. Rutile titanium dioxide, with its dense crystal structure, excellent stability, and excellent properties such as high temperature resistance, low temperature resistance, corrosion resistance, high strength, and low specific gravity, exhibits extremely high application value and is widely used in many fields such as coatings, plastics, inks, papermaking, chemical fibers, ceramics, daily chemicals, medicine, and food.

[0003] Currently, the main methods for commercial production of TiO2 include the sulfuric acid method and the chloride method. The sulfuric acid method uses ilmenite as the raw material and obtains the product through multiple steps such as sulfuric acid acidolysis, leaching, reduction, crystallization, hydrolysis, washing, and calcination. This method has mature technology and relatively low requirements for raw materials, so it has become the mainstream preparation process. However, the sulfuric acid method has exposed many drawbacks in practical applications. Its primary product is mainly anatase type. If a rutile type product is required, it must undergo a high-temperature calcination process at 800 - 1000 °C. In addition, this method also has problems such as a large amount of three-waste emissions, low resource recycling rate, and a cumbersome reaction process, which severely restricts the further development of this technology.

[0004] To solve the above problems of the sulfuric acid method, the chloride method came into being. The chloride method realizes partial recycling of chlorine gas and significantly reduces the emissions of three wastes. It is regarded as a new technology and new process encouraged currently. Its chemical reaction is mainly a gas-phase reaction between ferric chloride slag and chlorine gas under high temperature and high pressure to generate a gas-phase substance containing chlorine gas. Subsequently, impurity separation is carried out. Pure titanium tetrachloride is oxidized to form a TiO2 solid-phase material, and finally, after treatment, a rutile-type titanium dioxide powder with nearly 100% is obtained. However, the chloride method also has obvious limitations. It has extremely high requirements for the quality of raw materials. Most production must use high-grade titanium raw materials such as titanium chloride slag (calculated as TiO2, greater than 92%), artificial rutile, and natural rutile. Otherwise, the entire process cannot operate normally, which results in the production cost of the chloride method being much higher than that of the sulfuric acid method process. Moreover, since chlorine gas is used to decompose the raw materials under high pressure, the solid waste and liquid waste generated both contain chloride ions, causing greater impact on the environment.

[0005] To overcome the deficiencies of the chlorination process, some new processes between the sulfuric acid process and the chlorination process have gradually emerged. For example, a new technology for preparing TiO2 by the hydrochloric acid method. The prior art uses hydrochloric acid and titanium alkoxide to prepare rutile-type titanium dioxide nanometer micro-baseballs. The products prepared by this method have significant advantages such as good dispersibility, high crystallinity, and large specific surface area. However, in the actual preparation process, in addition to adding hydrochloric acid, a non-polar solvent needs to be introduced, and it is required to dropwise add hydrochloric acid and the non-polar solvent into the titanium alkoxide. The entire dropping process takes as long as 30 - 60 minutes. In an industrial production scenario, this inefficient and cumbersome operation process is difficult to meet the production requirements for rapidly and massively producing rutile-type titanium dioxide. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defects and deficiencies of the existing hydrochloric acid method that it is difficult to meet the requirements for rapidly and massively producing rutile-type titanium dioxide in industrial production, and to provide a method for preparing rutile-type titanium dioxide.

[0007] The above object of the present invention is achieved by the following technical solutions:

[0008] The present invention protects a method for preparing rutile-type titanium dioxide, comprising the following steps:

[0009] Mix ilmenite with a hydrochloric acid solution, and then carry out a solvothermal reaction under the condition that the temperature ≥ 140 °C. After the reaction is complete, cool, wash, and centrifuge, and take the precipitate and dry it to obtain rutile-type titanium dioxide;

[0010] Wherein, the concentration of the hydrochloric acid solution is 11.6 - 12 mol / L.

[0011] The present invention uses ilmenite as a raw material for acidolysis treatment. During the acidolysis process, the components in the ilmenite react to release Fe 2+ and Ti 4+ . The released Ti 4+ will undergo a hydrolysis reaction under acidic hydrothermal conditions to form TiO2·xH2O. Subsequently, this substance undergoes a dehydration condensation process and gradually forms TiO2 crystal nuclei. Since the high-temperature and high-pressure hydrothermal environment can significantly accelerate the reaction kinetics rate and provide more favorable conditions for the formation and growth of crystal nuclei, it is more likely to induce the formation of thermodynamically stable rutile-type crystal nuclei. At the same time, the acidic environment of hydrochloric acid also plays a key role in the formation process of TiO2 crystal nuclei. The coordination ability of Cl - in hydrochloric acid with Ti 4+ in ilmenite is relatively weak, which is beneficial to the formation of pure rutile-type titanium dioxide; and under acidic conditions, Ti 4+The hydrolysis product is more inclined to generate a rutile-type precursor structure through protonation condensation. Finally, through the above series of reactions and changes, rutile-type titanium dioxide is prepared. The preparation method of the present invention has simple steps, cheap and easily available raw materials, low production cost, and is suitable for industrial production.

[0012] In this application, ilmenite is selected as the raw material, mainly due to its low mining difficulty and economy. Ilmenite is widely distributed in basic rocks and acidic rocks, often existing as accessory minerals in igneous rocks and metamorphic rocks, and in some cases, it will form placer deposits. This extensive distribution characteristic makes the mining of ilmenite relatively convenient and the mining cost relatively low. Ilmenite from different origins usually contains a small amount of various metal impurities. Since most metal oxides can dissolve in concentrated hydrochloric acid and these impurities can be effectively removed through subsequent water washing processes, the preparation method provided in this application shows good applicability to ilmenite from different geographical sources. This characteristic ensures that the method can achieve stable and efficient preparation effects when dealing with ilmenite of different qualities.

[0013] Preferably, the content of TiO2 in the ilmenite is 45% - 50%.

[0014] Preferably, the mass-volume ratio of the ilmenite to the hydrochloric acid solution is 1:(2.5 - 10) g / mL.

[0015] Preferably, the mixing is stirring and mixing.

[0016] Preferably, the mixing time is 1 - 2 min.

[0017] Preferably, the temperature is 140 - 160 °C.

[0018] Furthermore, the chemical equation of the reaction is FeTiO3 + 2HCl → TiO2↓ + FeCl2 + H2O.

[0019] Preferably, the reaction time is 8 - 10 h.

[0020] Preferably, the reaction container is a reaction kettle.

[0021] Furthermore, the cooling is to cool the reaction solution after the reaction is complete to room temperature.

[0022] Preferably, the washing solvent is water.

[0023] Even further, the washing is to wash the cooled reaction solution with water 2 - 3 times.

[0024] Furthermore, the centrifugation is to centrifuge the washed mixture to collect the solid crude product.

[0025] Preferably, the rotation speed of the centrifugation is 8000 - 10000 rpm.

[0026] Preferably, the time of the centrifugation is 5 - 10 min.

[0027] Preferably, the temperature of the drying is 60 - 70 °C.

[0028] Preferably, the time of the drying is 30 - 60 min.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] During the acid digestion of ilmenite in the present invention, Fe 2+ and Ti 4+ are released, among which Ti 4+ hydrolyzes to form TiO2·xH2O under the hydrothermal conditions of hydrochloric acid, and then gradually forms TiO2 crystal nuclei through dehydration and condensation. In the hydrothermal environment of high temperature and high pressure, it is easier to induce the formation of thermodynamically stable rutile-type crystal nuclei. Since the coordination ability of Cl - in hydrochloric acid with Ti 4+ in ilmenite is weak, and the acidic environment promotes the protonation condensation of the hydrolysis products of Ti 4+ , which is beneficial to the formation of the rutile-type precursor structure, and then pure rutile-type titanium dioxide can be prepared. The preparation method of the present invention has simple steps, easily available raw materials and low cost, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 X-ray powder diffraction patterns of the rutile-type titanium dioxide prepared in Examples 1 - 6.

[0032] Figure 2 X-ray powder diffraction patterns of the titanium dioxide prepared in Comparative Examples 1 - 2.

[0033] Figure 3 Scanning electron microscope images of the rutile-type titanium dioxide prepared in Example 4.

[0034] Figure 4 Transmission electron microscope images of the rutile-type titanium dioxide prepared in Example 4.

[0035] Figure 5 High-resolution transmission electron microscope images of the rutile-type titanium dioxide prepared in Example 4.

[0036] Figure 6 Selected area electron diffraction patterns of the rutile-type titanium dioxide prepared in Example 4.

[0037] Figure 7EDS energy spectrum diagram of the rutile titanium dioxide prepared in Example 4. Detailed implementation manners

[0038] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific embodiments, but the embodiments do not impose any form of limitation on the present invention. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field.

[0039] Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0040] Ilmenite (TiO2 content is 47%) was purchased from Guangdong Huiyun Titanium Industry Co., Ltd.

[0041] Example 1 Preparation of a rutile titanium dioxide

[0042] Weigh 2 g of ilmenite and place it in a 25 mL polytetrafluoroethylene inner liner. Add 10 mL of 11.8 mol / L hydrochloric acid solution, stir for 1 min, then put it into the reaction kettle shell and tighten it. Then place the reaction kettle in an oven and react at 140 °C for 8 h. After the reaction is completed, let it cool naturally to room temperature. After obtaining the crude product, wash it three times with water. Then place the product in a centrifuge and centrifuge at a speed of 8000 rpm for 8 min. After centrifugation, pour out the liquid, and place the remaining solid in an oven to dry at 60 °C for 60 min to obtain rutile titanium dioxide.

[0043] Example 2 Preparation of a rutile titanium dioxide

[0044] The difference from Example 1 is that the reaction time is changed from 8 h to 10 h.

[0045] Other conditions and steps are the same as those in Example 1.

[0046] Example 3 Preparation of a rutile titanium dioxide

[0047] The difference from Example 1 is that the reaction temperature is changed from 140 °C to 150 °C.

[0048] Other conditions and steps are the same as those in Example 1.

[0049] Example 4 Preparation of a rutile titanium dioxide

[0050] The difference from Example 1 is that the reaction temperature is changed from 140 °C to 150 °C, and the reaction time is changed from 8 h to 10 h.

[0051] Other conditions and steps are the same as those in Example 1.

[0052] Example 5 Preparation of a rutile titanium dioxide

[0053] The difference from Example 1 is that the temperature of the reaction is changed from 140 °C to 160 °C.

[0054] Other conditions and steps are the same as those in Example 1.

[0055] Example 6 Preparation of rutile titanium dioxide

[0056] The difference from Example 1 is that the temperature of the reaction is changed from 140 °C to 160 °C, and the reaction time is changed from 8 h to 10 h.

[0057] Other conditions and steps are the same as those in Example 1.

[0058] Comparative Example 1 Preparation of titanium dioxide

[0059] The difference from Example 1 is that the solvent is changed from 10 mL of 11.8 mol / L hydrochloric acid solution to 3 mL of 11.8 mol / L hydrochloric acid solution and 7 mL of deionized water.

[0060] Other conditions and steps are the same as those in Example 1.

[0061] Comparative Example 2 Preparation of titanium dioxide

[0062] The difference from Example 1 is that the temperature of the reaction is changed from 140 °C to 100 °C.

[0063] Other conditions and steps are the same as those in Example 1.

[0064] Experimental Example Crystal form characterization of titanium dioxide

[0065] 1. X-ray powder diffraction (XRD) characterization

[0066] (1) Experimental method

[0067] The rutile titanium dioxide (2 mg) in Examples 1 to 6 and the titanium dioxide (2 mg) in Comparative Examples 1 to 2 were respectively loaded on a quartz wafer to make it flat without concavity or convexity, and then subjected to XRD testing on the machine.

[0068] (2) Experimental results

[0069] As Figure 1 shown, all the diffraction peak positions and intensities of the titanium dioxide samples prepared in Examples 1 to 6 accurately correspond to the characteristic peaks in the TiO2 (rutile type) standard card (PDF#77-0440), and no additional diffraction peaks attributable to impurity phases were observed. This result strongly indicates that rutile titanium dioxide with pure phase characteristics has been successfully prepared; from Figure 2It can be seen that in Comparative Example 1 and Comparative Example 2, since the concentration of the hydrochloric acid solution and the reaction temperature were respectively decreased, the reaction system failed to reach the conditions for sufficient reaction, resulting in the detection of the diffraction peak of the raw material FeTiO3 in the XRD pattern, indicating incomplete reaction.

[0070] 2. Characterization by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM)

[0071] In this experiment, the rutile-type titanium dioxide prepared in Example 4 was selected as the representative sample for SEM, TEM and HRTEM tests. The previous XRD characterization results showed that the rutile-type titanium dioxide prepared in other examples was highly consistent with Example 4.

[0072] (1) Experimental method

[0073] SEM: The rutile-type titanium dioxide (2 mg) in Example 4 was loaded on the conductive adhesive to make it flat without unevenness, and then subjected to SEM characterization on the machine.

[0074] TEM: The rutile-type titanium dioxide in Example 4 was dispersed in ethanol, then dropped on the copper grid and dried with a low-temperature infrared lamp, and then subjected to TEM characterization on the machine.

[0075] HRTEM: The rutile-type titanium dioxide in Example 4 was dispersed in ethanol, then dropped on the copper grid and dried with a low-temperature infrared lamp, and then subjected to HRTEM characterization on the machine.

[0076] (2) Experimental results

[0077] From Figure 3 the SEM image and Figure 4 the TEM image of Figure 5 it can be seen that the titanium dioxide prepared in Example 4 presents a regular needle-like structure, and this structural feature is highly consistent with the typical structural characteristics of rutile-type titanium dioxide. The nano-needle-like structure endows titanium dioxide with a large specific surface area, thus providing more surface active sites, which has a positive promoting effect on catalytic reactions, adsorption processes and interactions with the surrounding environment. In addition, the long strip needle-like structure is not easy to penetrate through the filter pores, and this characteristic has significant advantages in the filtration process of industrial production, which is beneficial to realizing solid-liquid separation and thus improving the efficiency of industrial production. Further, from

[0078] the HRTEM image of

[0079] In this experiment, the rutile titanium dioxide prepared in Example 4 was selected as the representative sample for SAED testing. The previous XRD characterization results showed that the rutile titanium dioxide prepared in other examples was highly consistent with that in Example 4.

[0080] (1) Experimental method

[0081] The rutile titanium dioxide in Example 4 was dispersed in ethanol, then dropped on a copper grid, dried with a low-temperature infrared lamp, and then subjected to SAED testing on the machine.

[0082] (2) Experimental results

[0083] From Figure 6 it can be observed that the crystal planes 101, 111, and 200 exhibit the typical crystal plane structure characteristics of rutile titanium dioxide. This result also strongly confirms that the titanium dioxide prepared in this application is rutile titanium dioxide.

[0084] 4. EDS energy spectrum characterization

[0085] In this experiment, the rutile titanium dioxide prepared in Example 4 was selected as the representative sample for EDS energy spectrum testing. The previous XRD characterization results showed that the rutile titanium dioxide prepared in other examples was highly consistent with that in Example 4.

[0086] (1) Experimental method

[0087] The rutile titanium dioxide in Example 4 was dispersed in ethanol, then dropped on a copper grid, dried with a low-temperature infrared lamp, and then subjected to EDS energy spectrum analysis on the machine.

[0088] (2) Experimental results

[0089] From Figure 7 it can be seen that Ti and O elements are evenly distributed in the needle-like titanium dioxide sample. This distribution characteristic not only verifies the presence of Ti and O elements in the sample and their ratio meeting the expectations from the chemical composition level, thereby confirming the chemical composition and purity of the sample; at the same time, it also reflects from the microscopic structure perspective that the preparation process has a high degree of stability, which can ensure the uniform incorporation of elements during crystal growth and the uniformity of the crystal structure at the macroscopic scale.

[0090] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing rutile titanium dioxide, characterized in that: The following steps are involved: After the ilmenite and the hydrochloric acid solution are mixed, a solvent thermal reaction is carried out at a temperature of ≥140°C. After the reaction is complete, the mixture is cooled, washed, centrifuged, and the precipitate is dried to obtain rutile titanium dioxide; Wherein, the concentration of the hydrochloric acid solution is 11.6-12 mol / L.

2. The preparation method according to claim 1, characterized in that: The TiO2 content in the ilmenite is 45% to 50%.

3. The preparation method according to claim 1, characterized in that: The temperature is 140-160°C.

4. The preparation method according to claim 1, characterized in that: The mass volume ratio of the ilmenite and the hydrochloric acid solution is 1: (2.5-10) g / mL.

5. The preparation method according to claim 1, characterized in that: The reaction time is 8 to 10 hours.

6. The preparation method according to claim 1, characterized in that: The washing solvent is water.

7. The preparation method according to claim 1, characterized in that: The centrifugal rotation speed is 8000-10000 rpm.

8. The preparation method according to claim 1, characterized in that: The centrifugation time is 5 to 10 minutes.

9. The preparation method according to claim 1, characterized in that: The drying temperature is 60-70°C.

10. The preparation method according to claim 1, characterized in that: The drying time is 30 to 60 minutes.

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