Method for producing refined titanium tetrachloride and method for producing titanium-based materials

Abstract

To provide a method for producing purified titanium tetrachloride and a method for producing a titanium-based material by which the appropriateness of using a vanadium separating agent can be determined.SOLUTION: A method for producing purified titanium tetrachloride of the present invention is for producing purified titanium tetrachloride with higher purity from crude titanium tetrachloride containing vanadium than the crude titanium tetrachloride. The method comprises a separation agent addition step in which a vanadium separating agent containing an organic compound is added to a liquid crude titanium tetrachloride, a distillation step in which the crude titanium tetrachloride is distilled after the separating agent addition step to obtain purified titanium tetrachloride, and a color inspection step in which the color of the liquid purified titanium tetrachloride is inspected after the distillation step.SELECTED DRAWING: None

Description

Technical Field

[0001] This invention relates to a method for producing purified titanium tetrachloride from crude titanium tetrachloride and a method for producing titanium-based materials using the same.

Background Art

[0002] Generally, the crude titanium tetrachloride obtained by reducing titanium oxide in titanium ore using coke in a chlorination furnace contains a number of impurities derived from titanium ore, coke, etc. In order to separate and remove such impurities, distillation or rectification is performed on the crude titanium tetrachloride to separate and concentrate it by utilizing the difference in boiling points of titanium tetrachloride and each impurity. By undergoing distillation or rectification, purified titanium tetrachloride is produced.

[0003] Here, among the impurities contained in the crude titanium tetrachloride, vanadium is difficult to separate from the crude titanium tetrachloride by distillation or rectification due to, for example, having a boiling point close to that of titanium tetrachloride depending on the form of chlorides and other compounds in the crude titanium tetrachloride. For this reason, as described in, for example, Patent Documents 1 to 4, vanadium is removed from the crude titanium tetrachloride by bringing the crude titanium tetrachloride into contact with a vanadium separation agent.

[0004] Patent Document 1 discloses "a method of recovering pure titanium tetrachloride by contacting titanium tetrachloride in vapor state with a solution or well-dispersed suspension of an organic reagent under heating, and then condensing it." Patent Document 1 states that "until now, the removal of vanadium impurities has been carried out by converting the impurities into a form that does not easily volatilize at the boiling point of titanium tetrachloride or into a non-volatile form, or by using organic treatment agents that react with VOCl3 or VCl4 to form non-volatile vanadium derivatives. Organic substances used for this purpose include animal oils, vegetable oils, waxes, their hydrolysis i.e., saponification derivatives such as fatty acids, fatty alcohols and soaps, petroleum fractions such as lubricating oils, mineral oils, heavy residue oil fractions (such as bunker C oil), hydrocarbon-rich substances such as tall oil, and hydrocarbon-rich polymers such as polyethylene and polypropylene."

[0005] Patent Document 2 states that "organic oils are known to be useful as vanadium passivating agents, and such oils include, for example, petroleum-based oils such as mineral oil and wax, animal fats and oils, and vegetable oils, as well as combinations thereof."

[0006] Patent Document 3 states that, "as a blending oil for refining titanium tetrachloride used when distilling and refining crude titanium tetrachloride, it uses mineral oil with a low content of polycyclic aromatic compounds (PCA) that have little impact on human health, and provides excellent removal of impurities such as vanadium," and proposes "a blending oil for refining titanium tetrachloride containing a mineral oil-based base oil with a DMSO extract content of less than 3% by mass, a %CA of 10 to 25, and an aromatic content of 50% by mass or more by chromatography, and a sulfur-based additive consisting of at least one of sulfurized oils and fats, sulfurized olefins, sulfurized esters, and polysulfides, as the sulfur content, in an amount of 2 to 8% by mass."

[0007] Patent Document 4 describes a method for producing TiCl4, comprising: a crude TiCl4 gas generation step of generating crude TiCl4 gas in a chloride reaction furnace; a liquefaction step of liquefying the generated crude TiCl4 gas to obtain a first crude TiCl4 liquid; an oil mixing step of mixing organic oil with the first crude TiCl4 liquid to obtain a second crude TiCl4 liquid; a preheating step of preheating the second crude TiCl4 liquid; a degassing step of degassing the preheated second crude TiCl4 liquid; and a rectification step of rectifying the second crude TiCl4 liquid in a rectification column. Patent Document 4 also states that "when reacted with the components of the organic oil, the V-containing substance precipitates as a non-volatile substance and can be easily separated from the second crude TiCl4 liquid." [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Special Publication No. 46-7363 [Patent Document 2] Special Publication No. 2006-515264 [Patent Document 3] Japanese Patent Publication No. 2010-254486 [Patent Document 4] Japanese Patent Publication No. 2019-172543 [Overview of the project] [Problems that the invention aims to solve]

[0009] The vanadium content in crude titanium tetrachloride can vary depending on the quality of the raw materials, such as titanium ore and coke. Accordingly, it is necessary to adjust the amount of vanadium separating agent added and other usage methods to suppress the residue of vanadium separating agent and vanadium in the refined titanium tetrachloride due to excessive or insufficient addition.

[0010] However, there was room for further consideration regarding whether the use of the vanadium separating agent was appropriate.

[0011] The object of this invention is to provide a method for producing purified titanium tetrachloride that allows for the determination of the suitability of using a vanadium separating agent, and a method for producing titanium-based materials. [Means for solving the problem]

[0012] After diligent research, the inventors noticed that while high-purity liquid titanium tetrachloride is almost colorless and transparent, it exhibits a yellowish hue when vanadium or a vanadium separating agent is present. However, in the case of crude titanium tetrachloride, which contains many other impurities, its color is also affected by these impurities, making it impossible to accurately estimate the presence or absence of vanadium or vanadium separating agent by examining its color. Therefore, the inventors decided to examine the color of the purified liquid titanium tetrachloride obtained after distillation of crude titanium tetrachloride. Since most impurities are removed from the purified titanium tetrachloride by distillation, it is possible to determine the presence or absence of discoloration due to vanadium or a vanadium separating agent, and consequently, the appropriateness of using a vanadium separating agent.

[0013] The present invention provides a method for producing purified titanium tetrachloride of higher purity than that of crude titanium tetrachloride containing vanadium, comprising: a separation agent addition step of adding a vanadium separation agent containing an organic compound to liquid crude titanium tetrachloride; a distillation step of performing distillation on the crude titanium tetrachloride after the separation agent addition step to obtain purified titanium tetrachloride; and a color inspection step of inspecting the color of the liquid purified titanium tetrachloride after the distillation step.

[0014] In the above-described method for producing purified titanium tetrachloride, it is preferable to continuously carry out the production of purified titanium tetrachloride, including the separation agent addition step, the distillation step, and the color inspection step.

[0015] The vanadium separating agent preferably contains mineral oil containing aromatic hydrocarbons.

[0016] It is preferable to use an apparatus for the color inspection of purified titanium tetrachloride in the color inspection step.

[0017] In this case, in the color inspection step, based on the determination value Vd obtained from the formula: Vd = [(R + G) / 2] - B from the respective values of R, G, and B in the RGB color model representing the color of the purified titanium tetrachloride, it is preferable to perform the color inspection of the purified titanium tetrachloride.

[0018] The above method for producing purified titanium tetrachloride includes a component analysis step of analyzing components derived from the vanadium separating agent in the purified titanium tetrachloride after the distillation step, and it is preferable to adjust the vanadium separating agent in the separating agent addition step according to the inspection result of the color inspection step and the analysis result in the component analysis step.

[0019] In the component analysis step, infrared spectroscopy can be used.

[0020] The method for producing a titanium-based material of this invention is to produce at least one titanium-based material selected from the group consisting of sponge titanium, titanium oxide, titanium tetrachloride aqueous solution, catalyst for polyolefin polymerization, and titanate using the purified titanium tetrachloride produced by the method for producing purified titanium tetrachloride according to any of the above.

Advantages of the Invention

[0021] According to this invention, it is possible to determine the suitability of using a vanadium separating agent.

Brief Description of the Drawings

[0022] [Figure 1] It is a schematic diagram showing an example of equipment capable of implementing the method for producing purified titanium tetrachloride according to an embodiment of this invention. [Figure 2] It is a graph showing the relationship between the Hazen color number of a Hazen color number standard solution and the determination value Vd obtained from the values of R, B, and G representing the color of the Hazen color number standard solution. [Modes for carrying out the invention]

[0023] Embodiments of this invention will be described in detail below. A method for producing refined titanium tetrachloride according to one embodiment of this invention is a method for producing refined titanium tetrachloride of higher purity than crude titanium tetrachloride from crude titanium tetrachloride containing vanadium. This production method includes a separation agent addition step of adding a vanadium separation agent containing an organic compound to liquid crude titanium tetrachloride, a distillation step of performing distillation on the crude titanium tetrachloride after the separation agent addition step to obtain refined titanium tetrachloride, and a color inspection step of inspecting the color of the liquid refined titanium tetrachloride after the distillation step.

[0024] The purified titanium tetrachloride obtained after the distillation process has had most impurities sufficiently removed. Therefore, if the purified titanium tetrachloride exhibits a yellow or other color during the color inspection process, this color indicates that it contains a certain amount of vanadium or vanadium separating agent. Thus, the results of the color inspection process can be used to confirm whether the vanadium and vanadium separating agent content in the purified titanium tetrachloride is low enough to meet the required quality standards.

[0025] Preferably, the process includes a component analysis step after the color inspection step, in which components derived from the vanadium separating agent in the purified titanium tetrachloride are analyzed. This allows the component analysis step to determine whether the color of the purified titanium tetrachloride exhibits a color in the color inspection step, whether that color is due to vanadium or the vanadium separating agent, and furthermore, whether the amount of vanadium separating agent added in the separating agent addition step is insufficient or excessive. Based on the results of the color inspection step and the analysis in the component analysis step, the amount of vanadium separating agent added in the separating agent addition step and other usage methods can be adjusted. This manufacturing method can be carried out using equipment such as that shown in Figure 1.

[0026] (Crude titanium tetrachloride)

[0027] Crude titanium tetrachloride is generally produced by the chlorination reaction of titanium ore in a chlorination furnace 1. More specifically, for example, the chlorination furnace 1 is maintained at a high temperature of about 1000°C, and chlorine gas is supplied from below the raw materials, including titanium ore and coke, towards the top, forming a fluidized bed. In the fluidized bed, gaseous crude titanium tetrachloride is produced by the reaction equation: TiO2 + C + 2Cl2 → TiCl4 + CO2 / CO. At this time, by-products such as carbon dioxide and sulfur-containing compounds may also be produced. The gaseous crude titanium tetrachloride produced in the chlorination furnace 1 is sent to a condenser 2 connected to the chlorination furnace 1, where it is cooled and turned into a liquid. The liquid crude titanium tetrachloride may be stored in a storage tank 3.

[0028] The crude titanium tetrachloride obtained in this way contains many impurities derived from titanium ore, coke, etc. Specifically, crude titanium tetrachloride contains vanadium, and may also contain carbon, oxygen, sulfur, phosphorus, chlorine, iron, aluminum, etc. For example, the vanadium content of crude titanium tetrachloride may be 0.02% to 0.2% by mass, and the carbon content may be 0.001% to 0.005% by mass. Such impurities may be present in liquid crude titanium tetrachloride in the form of CO, O2, CO2, COS, SO2, COCl2, CCl4, POCl3, VCl4, VOCl3, etc.

[0029] In order to separate and remove most of the impurities mentioned above from crude titanium tetrachloride, the separation agent addition process and distillation process described later are carried out.

[0030] Here, "crude titanium tetrachloride" refers to a material containing at least vanadium in addition to titanium tetrachloride (TiCl4), and which is used in the separation agent addition process described below. "Purified titanium tetrachloride" refers to a material that has undergone the distillation process described later and has a higher purity of titanium tetrachloride (TiCl4) than the crude titanium tetrachloride described above. When simply referred to as "titanium tetrachloride," it refers to a compound in which the crude titanium tetrachloride and purified titanium tetrachloride are not distinguished.

[0031] (Separation agent addition process) In the separation agent addition step, a vanadium separation agent containing an organic compound is added to the liquid crude titanium tetrachloride.

[0032] In the example of the equipment shown in Figure 1, the separation agent addition process is carried out in the evaporator 4, where liquid crude titanium tetrachloride is heated and evaporated for distillation in the distillation process described below. Here, a separation agent tank 10 is connected to the piping that carries crude titanium tetrachloride from the storage tank 3 to the evaporator 4, and vanadium separation agent is supplied from there to the evaporator 4 along with the crude titanium tetrachloride. The crude titanium tetrachloride with the added vanadium separation agent is then heated and vaporized in the evaporator 4 and introduced into the rectification column 5. The timing of contacting the crude titanium tetrachloride with the vanadium separation agent is not particularly limited to any time after the crude titanium tetrachloride is generated but before distillation is performed on the crude titanium tetrachloride, and can be determined as appropriate.

[0033] The vanadium separating agent contains an organic compound and is typically an oil (organic oil), preferably a mineral oil containing aromatic hydrocarbons, but may also contain animal oil or vegetable oil containing fatty acids, or wax. Known vanadium separating agents can be used. The mineral oil may contain 10% or more by mass, 30% or more by mass, 50% or more by mass, or 75% or more by mass of aromatic hydrocarbons.

[0034] When a vanadium separating agent as described above is added to liquid crude titanium tetrachloride, for example, the vanadium separating agent reacts with VOCl3 and VCl4 in the crude titanium tetrachloride to form a non-volatile vanadium derivative, and this vanadium is separated and removed from the titanium tetrachloride after the addition of the vanadium separating agent and / or during distillation.

[0035] If too much vanadium separating agent is added, even if the vanadium in the crude titanium tetrachloride is sufficiently removed, the remaining vanadium separating agent that was not used in the reaction will remain and become an impurity. On the other hand, if too little vanadium separating agent is added, there will be insufficient separating agent, resulting in inadequate removal of vanadium from the crude titanium tetrachloride, which will also be present in the refined titanium tetrachloride. Therefore, it is necessary to add the vanadium separating agent in an appropriate amount. On the other hand, depending on the grade of the titanium ore and other conditions, the vanadium content of the crude titanium tetrachloride may fluctuate, making it difficult to uniformly determine the appropriate amount of vanadium separating agent to add.

[0036] The color of titanium tetrachloride is an indicator used to determine the amount of vanadium separating agent to add. High-purity liquid titanium tetrachloride, which contains almost no impurities, is practically colorless and transparent, but liquid titanium tetrachloride containing vanadium exhibits a yellowish color. Furthermore, liquid titanium tetrachloride containing the aforementioned vanadium separating agent often has a similar yellow color. However, since crude titanium tetrachloride has a color due to other impurities, it is difficult to determine the presence or absence of vanadium or vanadium separating agent by examining the color of crude titanium tetrachloride after contact with the vanadium separating agent. Therefore, in this embodiment, after removing most of the impurities by performing the distillation process described below, a color inspection process is performed to examine the color of the purified titanium tetrachloride obtained therefrom.

[0037] (Distillation process) In the distillation process, the crude titanium tetrachloride after the separation agent addition process is distilled using known methods to reduce impurities and obtain purified titanium tetrachloride. Here, "distillation" is used as a term that includes not only distillation that separates and concentrates titanium tetrachloride and each impurity by utilizing the difference in boiling points, but also rectification, which involves repeating the distillation process.

[0038] As an example, as shown in Figure 1, liquid crude titanium tetrachloride is heated in an evaporator 4 to evaporate into a gas, which is then sent to a rectification column 5. The rectification column 5 is divided into multiple shelves arranged at different heights in the vertical direction, and at each stage, the high-boiling-point and low-boiling-point components of the crude titanium tetrachloride are separated based on the difference in boiling points through gas-liquid contact. As a result, the purified titanium tetrachloride obtained by passing through the rectification column 5 has had most of the impurities contained in the crude titanium tetrachloride sufficiently removed.

[0039] (Color inspection process) In the color inspection process, the color of the purified titanium tetrachloride liquid after passing through the rectification column 5 in the distillation process is inspected.

[0040] As mentioned earlier, purified titanium tetrachloride tends to have a yellowish tint whether it contains vanadium or a vanadium separating agent. Here, since the purified titanium tetrachloride that has already undergone distillation is the subject of the test, it is virtually free from discoloration caused by other impurities. Therefore, it is possible to determine with high accuracy whether or not the purified titanium tetrachloride contains vanadium or a vanadium separating agent.

[0041] The color of purified titanium tetrachloride can also be inspected visually. In this case, for example, purified titanium tetrachloride can be visually compared with a platinum-cobalt color standard solution (Hazen color number standard solution) prepared in accordance with JIS K0071 (2017).

[0042] On the other hand, it is preferable to inspect the color of purified titanium tetrachloride using a colorimeter, colorimeter, or spectrophotometer, or an imaging or photographic device such as a camera, and an image processing device including a computer for processing the images obtained thereby. Using such a device can improve productivity, reduce labor costs, and prevent variations in inspection results that depend on the individual inspection ability of the person performing the inspection visually, thereby improving inspection accuracy.

[0043] When using a colorimeter or similar device, it is preferable to represent the color of purified titanium tetrachloride using the R, G, and B values ​​in the RGB color model, and then calculate the judgment value Vd using the formula Vd = [(R+G) / 2]-B from these R, G, and B values. In other words, here, the judgment value Vd is obtained by subtracting B from the average value of R and G. As explained in the Examples section below, it has been found that there is a high correlation between the Hazen color number (Hazen number) of the aforementioned Hazen color number standard solution and the judgment value Vd obtained from the R, G, and B values ​​representing the color of that Hazen color number standard solution. Therefore, by determining the judgment value Vd for the color of purified titanium tetrachloride, it is possible to estimate which Hazen color number of the Hazen color number standard solution the purified titanium tetrachloride is closest to using the above correlation from the judgment value Vd.

[0044] The inspection results obtained during the color inspection process allow for the estimation of vanadium and vanadium separating agent content in refined titanium tetrachloride. This makes it possible to determine whether the refined titanium tetrachloride meets the required quality standards. For example, if the inspection results indicate that the refined titanium tetrachloride has a strong yellowish tint, it may indicate a relatively high amount of vanadium or vanadium separating agent. Measures such as suspending shipment of refined titanium tetrachloride with a strong yellowish tint may be taken.

[0045] The color inspection process may be carried out, for example, by passing liquid purified titanium tetrachloride through or storing it in a color inspection area 6 connected to the discharge port of purified titanium tetrachloride from the rectification column 5, using a color difference meter or similar device. For example, the color inspection area 6 may be constructed with a light-transmitting material such as glass surrounding the interior through which the purified titanium tetrachloride passes, ensuring that the area where the color is measured is appropriately shielded from light. As an example of a color inspection area 6, if a measurement area with a glass window is provided in the piping, the purified titanium tetrachloride may be flowed through the piping in a liquid state.

[0046] If the color inspection process indicates that the color of the purified titanium tetrachloride is unacceptable, it is preferable to return the purified titanium tetrachloride to the storage tank 3 or evaporator 4 and subject it again to the separation agent addition process or distillation process.

[0047] (component analysis process) If, for example, the yellow tint of refined titanium tetrachloride is found to be stronger than the prescribed standard during the color inspection process, it may be desirable to confirm whether that color of the refined titanium tetrachloride is due to vanadium or the vanadium separating agent. This is because confirming this can allow for appropriate adjustment of the vanadium separating agent in the separating agent addition process.

[0048] In such cases, it is preferable to perform a component analysis step after the distillation process to analyze the components derived from the vanadium separating agent in the purified titanium tetrachloride.

[0049] The specific analytical method for the component analysis step is not particularly limited as long as it can analyze the components derived from the vanadium separation agent in the purified titanium tetrachloride, but infrared spectroscopy is preferred. Infrared spectroscopy can confirm the presence or absence of organic compounds in the vanadium separation agent and can be performed relatively easily using an infrared spectrophotometer (IR).

[0050] If a component analysis step is performed, the amount and method of adding the vanadium separating agent in the separating agent addition step, as well as the type of vanadium separating agent, can be adjusted according to the results of the color inspection step and the analysis step described above. Specifically, the amount of vanadium separating agent added in the separating agent addition step can be increased or decreased.

[0051] For example, if the color inspection process yields an unacceptable result for the color of the purified titanium tetrachloride, and the component analysis process yields an analysis result indicating that the purified titanium tetrachloride contains a certain amount of vanadium separating agent, then it is likely that an excessive amount of vanadium separating agent was added in the separating agent addition process. In this case, adjustments such as reducing the amount of vanadium separating agent added can be made. Alternatively, if the analysis results indicate that the purified titanium tetrachloride contains almost no vanadium separating agent, then the yellowish tint of the purified titanium tetrachloride in the color inspection process is presumed to be due to vanadium, not the vanadium separating agent. In this case, it is likely that the amount of vanadium separating agent added in the separating agent addition process was insufficient, and adjustments such as increasing the amount of vanadium separating agent added can be made.

[0052] As shown in Figure 1, the component analysis process may be performed after the color inspection process at component analysis location 7, which is connected in series with color inspection location 6. Alternatively, although not shown in the figure, the component analysis location may be set up in parallel with the color inspection location (i.e., the component analysis location may be connected to the rectification column), and the component analysis process may be performed before or simultaneously with the color inspection process.

[0053] If the component analysis process reveals that the purified titanium tetrachloride contains a certain amount of components derived from the vanadium separating agent, it is preferable to return the purified titanium tetrachloride to the storage tank 3 or evaporator 4 and subject it again to the separating agent addition process or distillation process.

[0054] The production of purified titanium tetrachloride, which includes the separation agent addition process, distillation process, color inspection process, and possibly a component analysis process as described above, may be carried out continuously using the equipment illustrated in Figure 1. In this case, labor costs can be reduced and human error can be prevented. During the separation agent addition process in this continuous production, for example, a vanadium separation agent may be added to crude titanium tetrachloride in the evaporator 4.

[0055] (Manufacturing method for titanium-based materials) The refined titanium tetrachloride produced in the manner described above has a relatively low vanadium content and contains almost no vanadium separating agent used to remove vanadium. Furthermore, most of the other impurities present in the crude titanium tetrachloride are effectively removed during the distillation process. Therefore, this refined titanium tetrachloride has a relatively high degree of purity.

[0056] By using the purified titanium tetrachloride described above, at least one titanium-based material selected from the group consisting of sponge titanium, titanium oxide, aqueous titanium tetrachloride solution, polyolefin polymerization catalyst, and titanate salts such as barium titanate can be produced by known methods. Such titanium-based materials also have sufficiently reduced impurities and are suitable for their respective applications. High-purity purified titanium tetrachloride is particularly suitable for use in the production of titanium-based materials used in semiconductors. [Examples]

[0057] Next, the method for producing purified titanium tetrachloride according to this invention was experimentally carried out, and its effects were confirmed, which are described below. However, this description is for illustrative purposes only and is not intended to be limiting.

[0058] (Comparative Example 1) Using the equipment shown in Figure 1, a chlorination reaction was carried out in a chloride furnace using raw materials containing titanium ore and coke. The crude titanium tetrachloride obtained therefrom was cooled in a condenser to obtain liquid crude titanium tetrachloride in an evaporator.

[0059] In the evaporation vessel described above, 1.0 to 2.0 g / L of mineral oil containing 83% by mass of aromatic hydrocarbons (DEVAL-TT, manufactured by ENEOS Corporation) was continuously supplied along with liquid crude titanium tetrachloride as a vanadium separating agent, and vanadium was precipitated from the crude titanium tetrachloride in the evaporation vessel. Subsequently, when the color of the liquid crude titanium tetrachloride was visually inspected, it was found that the coloration was due to components other than vanadium and the vanadium separating agent, making it impossible to determine whether the amount of vanadium separating agent added was appropriate.

[0060] ( reference Example 1) In the same manner as in Comparative Example 1, the same amount of vanadium separating agent was added to liquid crude titanium tetrachloride, and then distillation was performed in a rectification column to obtain purified titanium tetrachloride.

[0061] Visually comparing the purified titanium tetrachloride described above with platinum-cobalt color standard solutions (Hazen color number standard solutions, No. 10-80) based on JIS K0071 (2017), it was determined that the color of the purified titanium tetrachloride was 40 or less on the Hazen color number scale.

[0062] As a result, it was found that the purified titanium tetrachloride contained vanadium and vanadium separating agent in amounts below the permissible limits for this application, and that the amount of vanadium separating agent added was appropriate.

[0063] ( reference Example 2) reference Refined titanium tetrachloride was obtained in the same manner as in Example 1. When the color of this refined titanium tetrachloride was examined with a colorimeter (CV-X400 manufactured by Keyence Corporation), the color was (R, G, B) = (170, 169, 162) in the RGB color model. From the R, G, and B values, the judgment value Vd was calculated as Vd = [(R+G) / 2]-B, and the judgment value Vd was 7.5.

[0064] Separately, we investigated the relationship between platinum-cobalt color standard solutions (Hazen color number standard solutions, No. 10-80) based on JIS K0071 (2017) and the judgment value Vd obtained from the R, G, and B values ​​of the RGB color model of the color of the Hazen color number standard solutions, and obtained the graph shown in Figure 2. From this graph, R 2 The result was 0.9658 (≈1), confirming a high correlation between them.

[0065] The color determination value Vd for the purified titanium tetrachloride described above corresponds to a Hazen color number of 40 or less in the Hazen color number standard solution, as shown in the graph in Figure 2. Therefore, it was found that the color of the purified titanium tetrachloride is similar to that of a Hazen color number of 40 or less. Thus, reference It can be seen that the same results were obtained as in the visual inspection in Example 1.

[0066] In addition, reference When the components of the purified titanium tetrachloride obtained in Example 2 were analyzed using an FT / IR-4100 (manufactured by JASCO Corporation), the hydrocarbon content was found to be 0.8 ppm by mass.

[0067] ( reference Example 3) reference Perform distillation in the same manner as in Example 1. reference Unlike Example 1, the sample was taken from a different position in the rectification column. reference A purified titanium tetrachloride with a different purity than that obtained in Example 1 was obtained.

[0068] When the purified titanium tetrachloride described above was visually compared with platinum-cobalt color standard solutions (Hazen color number standard solutions, No. 10-80) based on JIS K0071 (2017), the purified titanium tetrachloride had a color similar to that of solutions with a Hazen color number of 80 or less.

[0069] As a result, it was found that the purified titanium tetrachloride contained vanadium and vanadium separating agent in amounts below the permissible limits for this application, and that the amount of vanadium separating agent added was appropriate.

[0070] ( reference Example 4) reference Refined titanium tetrachloride was obtained in the same manner as in Example 3. When the color of this refined titanium tetrachloride was examined with a colorimeter (CV-X400 manufactured by Keyence Corporation), the color was (R, G, B) = (176, 171, 155) in the RGB color model. From the R, G, and B values, the judgment value Vd was calculated as Vd = [(R+G) / 2]-B, and the judgment value Vd was 18.5.

[0071] The color determination value Vd for the purified titanium tetrachloride described above corresponds to a Hazen color number of 80 or less in the Hazen color number standard solution, as shown in the graph in Figure 2. Therefore, it was found that the color of the purified titanium tetrachloride is similar to that of a Hazen color number of 80 or less. Thus, reference It can be seen that the same results were obtained as in the visual inspection in Example 3.

[0072] (Examples) 1 ) When the color of purified titanium tetrachloride obtained separately was examined, the Hazen color number was 100. Analysis of the components of this purified titanium tetrachloride using an FT / IR-4100 (manufactured by JASCO Corporation) revealed that the hydrocarbon content was: reference The hydrocarbon content was 14.0 ppm by mass, which was considerably higher than that of the purified titanium tetrachloride in Example 2.

[0073] Based on these results, it could be determined that the amount of vanadium separating agent used in the manufacturing process of the refined titanium tetrachloride in question was excessive.

[0074] From the above, it has been found that, according to this invention, vanadium can be successfully separated from crude titanium tetrachloride by appropriately using a vanadium separating agent. [Explanation of Symbols]

[0075] 1. Chloride furnace 2 Capacitors 3 Storage tank 4. Evaporator 5 Rectification tower 6 Color testing locations 7. Component analysis locations 10 Separating agent tank

Claims

1. A method for producing refined titanium tetrachloride of higher purity than said crude titanium tetrachloride from crude titanium tetrachloride containing vanadium, The process includes a separation agent addition step of adding a vanadium separation agent containing an organic compound to liquid crude titanium tetrachloride, a distillation step of distilling the crude titanium tetrachloride after the separation agent addition step to obtain purified titanium tetrachloride, and a color inspection step of inspecting the color of the liquid purified titanium tetrachloride after the distillation step. Following the distillation step, the process includes a component analysis step in which the components derived from the vanadium separating agent in the purified titanium tetrachloride are analyzed. A method for producing purified titanium tetrachloride, comprising adjusting the vanadium separating agent in the separating agent addition step according to the inspection results of the color inspection step and the analysis results of the component analysis step.

2. A method for producing purified titanium tetrachloride according to claim 1, comprising continuously performing the production of purified titanium tetrachloride including the separation agent addition step, the distillation step, and the color inspection step.

3. The method for producing purified titanium tetrachloride according to claim 1, wherein the vanadium separating agent contains mineral oil containing aromatic hydrocarbons.

4. A method for producing purified titanium tetrachloride according to claim 1, wherein an apparatus is used to inspect the color of the purified titanium tetrachloride in the aforementioned color inspection step.

5. A method for producing purified titanium tetrachloride according to claim 4, wherein in the color inspection step, the color of the purified titanium tetrachloride is inspected based on a determination value Vd obtained from the formula: Vd = [(R + G) / 2] - B, using the R, G, and B values ​​in the RGB color model representing the color of the purified titanium tetrachloride.

6. A method for producing purified titanium tetrachloride according to claim 1, wherein infrared spectroscopy is used in the component analysis step.

7. A method for producing a titanium-based material, comprising using purified titanium tetrachloride produced by the method for producing purified titanium tetrachloride according to any one of claims 1 to 6, to produce at least one titanium-based material selected from the group consisting of sponge titanium, titanium oxide, aqueous titanium tetrachloride solution, polyolefin polymerization catalyst, and titanate salt.

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