JP6687637B2 - Method for producing titanium trichloride solution and apparatus for producing titanium trichloride solution - Google Patents

Description

The present invention relates to a method for producing a titanium trichloride solution and an apparatus for producing a titanium trichloride solution.
This application claims the priority right based on Japanese application No. 2015-200520 filed on October 8, 2015, and incorporates all the contents described in the above Japanese application.

  A titanium trichloride solution is used as a reducing agent in a liquid-phase reduction method in which metal ions in an aqueous solution are reduced by a reducing agent to produce metal powder. It is known that a titanium trichloride solution can be produced by electrolytically reducing a titanium tetrachloride solution (see, for example, JP 2012-255188 A).

  In the method for producing a titanium trichloride solution described in the above publication, titanium tetrachloride is used as an electrolyte solution on the cathode side, an aqueous solution containing hydrochloric acid and an oxidation inhibitor is used, and as an electrolyte solution on the anode side, for example, an ammonium chloride aqueous solution, a sodium chloride aqueous solution, An aqueous solution containing chlorine ions such as an aqueous titanium chloride solution is used.

JP 2012-255188 A

  A method for producing a titanium trichloride solution according to one aspect of the present invention is a method for producing a titanium trichloride solution for reducing titanium tetrachloride in an electrolytic solution by an ion exchange electrolytic reduction method, wherein the electrolytic solution on the anode side is An aqueous solution containing sulfate ions is used.

  Further, a titanium trichloride solution producing apparatus according to another aspect of the present invention is an apparatus for producing a titanium trichloride solution by electrolytic reduction of titanium tetrachloride in an aqueous solution, an anode chamber for storing an anode electrolyte, The anode chamber and the ion exchange membrane are partitioned, and the cathode chamber stores the titanium tetrachloride solution, the anode is immersed in the anode electrolyte of the anode chamber, and the cathode is immersed in the titanium tetrachloride solution of the cathode chamber, The anode electrolyte contains sulfate ions.

FIG. 1 is a schematic view showing an apparatus for producing a titanium trichloride solution according to an embodiment of the present invention.

[Problems to be solved by the present disclosure]
In the method for producing a titanium trichloride solution using an aqueous solution containing chlorine ions as the electrolytic solution on the anode side, chlorine ions generate chlorine gas by an anodic reaction, and react with other solute components in the electrolytic solution to form chloride. May generate gas. Therefore, in the above method for producing titanium trichloride, it is usually necessary to suck and exhaust the generated gas.

  In order to reduce the cost of such chlorine-based gas treatment, it is desired to suppress the amount of chlorine-based gas generated in the production of the titanium trichloride solution.

  The present invention has been made based on the above circumstances, and an object of the present invention is to provide a method for producing a titanium trichloride solution and an apparatus for producing a titanium trichloride solution capable of suppressing the amount of chlorine-based gas generated. .

[Effect of the present disclosure]
The method for producing a titanium trichloride solution according to one aspect of the present invention and the apparatus for producing a titanium trichloride solution according to another aspect of the present invention can suppress the generation amount of chlorine-based gas.

[Description of Embodiments of the Present Invention]
A method for producing a titanium trichloride solution according to one aspect of the present invention is a method for producing a titanium trichloride solution for reducing titanium tetrachloride in an electrolytic solution by an ion exchange electrolytic reduction method, wherein the electrolytic solution on the anode side is An aqueous solution containing sulfate ions is used. The “ion exchange electrolytic reduction method” means an electrolytic reduction method in which an electrolytic solution on the anode side and an electrolytic solution on the cathode side are separated by an ion exchange membrane to perform electrolysis.

  The method for producing the titanium trichloride solution is such that, as the electrolyte solution on the anode side, an aqueous solution containing sulfate ions is used to suppress the chloride ion concentration of the electrolyte solution on the anode side to a low level, and chloride ions in the electrolyte solution on the anode side are used. Can be prevented from reacting unnecessarily with the electrolytic solution and other substances in the air, and the amount of chlorine-based gas generated can be suppressed.

  The molar concentration of sulfate ions in the electrolyte solution on the anode side may be equal to or higher than the total molar concentration of other anions. Thus, when the molar concentration of sulfate ions in the electrolyte solution on the anode side is equal to or higher than the total molar concentration of other anions, generation of chlorine-based gas can be prevented more reliably.

  The ion exchange membrane is preferably a cation exchange membrane. As described above, since the ion exchange membrane is a cation exchange membrane, it is possible to prevent chlorine ions in the electrolyte solution on the cathode side from moving to the anode side, so that the generation of chlorine-based gas can be further suppressed. it can.

  The total molar concentration of metal ions in the electrolyte solution on the anode side is preferably 1/10 or less of the molar concentration of sulfate ions. Thus, the total molar concentration of metal ions in the electrolytic solution on the anode side is less than or equal to the upper limit, thereby reducing the amount of metal ions in the carrier moving from the anode side to the cathode side, and the reaction efficiency of the cathode. The decrease can be suppressed.

  The ion exchange membrane may be an anion exchange membrane. As described above, since the ion exchange membrane is an anion exchange membrane, the electrolytic cell used in the conventional method for producing a titanium trichloride solution can be used, so that the facility cost can be suppressed.

  It is preferable to have a step of adding an oxidation inhibitor to the electrolyte solution on the cathode side. Thus, by having a step of adding an oxidation inhibitor to the electrolyte solution on the cathode side, the oxidation of trivalent titanium ions generated by the cathode reaction is suppressed, and a titanium trichloride solution is produced relatively efficiently. can do.

  As the oxidation inhibitor, it is preferable to use a carboxylic acid having two or more carboxyl groups or a salt of this carboxylic acid. Thus, by using a carboxylic acid having two or more carboxyl groups or a salt of this carboxylic acid as the above-mentioned oxidation inhibitor, the oxidation of trivalent titanium ions can be more effectively suppressed and the storability can be relatively improved. An excellent titanium trichloride solution can be produced.

  An apparatus for producing a titanium trichloride solution according to another aspect of the present invention is an apparatus for producing a titanium trichloride solution by electrolytic reduction of titanium tetrachloride in an aqueous solution, and an anode chamber for storing an anode electrolyte, The chamber and the ion exchange membrane are partitioned, a cathode chamber for storing the titanium tetrachloride solution, an anode immersed in the anode electrolyte of the anode chamber, and a cathode immersed in the titanium tetrachloride solution of the cathode chamber, The anode electrolyte contains sulfate ions.

  The titanium trichloride solution manufacturing apparatus suppresses the chloride ion concentration of the electrolyte on the anode side to be low by preventing the generation of chlorine or chloride unnecessarily by containing the sulfate ion in the anode electrolyte. Thus, the amount of chlorine-based gas generated can be suppressed.

[Details of the embodiment of the present invention]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The apparatus for producing a titanium trichloride solution in FIG. 1 is used for producing a titanium trichloride solution (TiCl ₃ ) by electrolytic reduction of titanium tetrachloride (TiCl ₄ ) in an aqueous solution.

  It is preferable that the titanium trichloride solution manufacturing apparatus includes an electrolytic cell 1 and a power source 2 that applies a voltage to the electrolytic cell 1.

<Electrolysis tank>
The electrolytic cell 1 is defined by an anode chamber 11 that stores an electrolyte solution on the anode side (hereinafter, sometimes referred to as an anode electrolyte solution), the anode chamber 11 and an ion exchange membrane 12, and an electrolyte solution on the cathode side (hereinafter, referred to as a cathode). (Sometimes referred to as an electrolyte), a cathode chamber 13 that stores a titanium tetrachloride solution, an anode 14 that is immersed in the anode electrolyte of the anode chamber 11, and a cathode 15 that is immersed in the titanium tetrachloride solution of the cathode chamber 13. . A DC voltage is applied between the anode 14 and the cathode 15 by the power supply 2.

(Anode chamber)
The anode chamber 11 is a space on the side where the anode 14 is arranged, of the two spaces formed by partitioning the internal space of the electrolytic cell 1 with the ion exchange membrane 12. In other words, the anode chamber 11 is adjacent to the cathode chamber 13 via the ion exchange membrane 12. As will be described later in detail, an aqueous solution containing sulfate ions is stored in the anode chamber 11 as an anode electrolyte.

(Ion exchange membrane)
The ion exchange membrane 12 is a diaphragm that divides the internal space of the electrolytic cell 1 into an anode chamber 11 and a cathode chamber 13, and selectively allows cations or anions to pass therethrough. That is, the ions that can pass through the ion exchange membrane 12 can move back and forth between the anode chamber 11 and the cathode chamber 13. The ions passing through the ion exchange membrane 12 function as carriers for moving charges between the anode 14 and the cathode 15, and allow an electric current to flow between the anode 14 and the cathode 15.

  The ion exchange membrane 12 is not particularly limited, and a known cation exchange membrane or anion exchange membrane can be used. When a cation exchange membrane that selectively allows cations to pass therethrough is used as the ion exchange membrane 12, for example, a hydrocarbon-based ion exchange membrane, a polymer perfluorocarbon-based ion exchange membrane, or the like can be used. As the hydrocarbon-based ion exchange membrane, a styrene-divinylbenzene copolymer or other hydrocarbon-based polymer having a cation exchange group introduced therein can be used. The polymer perfluorocarbon-based ion exchange membrane has a perfluoroalkylene group as the main chain skeleton, has perfluorovinyl ether as a part of its side chain, and has a cation exchange group introduced at the end of this side chain. Can be used. Examples of the cation exchange group include a sulfonic acid group and a carboxylic acid group.

As described above, by using the cation exchange membrane as the ion exchange membrane 12, the titanium trichloride manufacturing apparatus uses hydrogen ions (H ⁺ ) generated by electrolysis of water in the anode electrolyte as a carrier. By passing a current between the anode 14 and the cathode 15, tetravalent titanium ions in the cathode electrolyte are reduced. Thereby, it is possible to prevent chlorine ions (Cl ⁻ ) in the cathode electrolyte solution from moving into the anode electrolyte solution, and to more effectively prevent chlorine ions from being supplied to the anode reaction to generate chlorine gas. it can.

  When an anion exchange membrane that selectively allows passage of anions is used as the ion exchange membrane 12, for example, a hydrocarbon-based ion exchange having a styrene-divinylbenzene copolymer as a main chain skeleton and having a quaternary ammonium group at the end. A film or the like can be used.

As described above, when the anion exchange membrane is used as the ion exchange membrane 12, the chlorine ions in the cathode electrolyte serve as carriers for transferring electric charges and move into the anode electrolyte to thereby form the anode 14 and the cathode 15. Allows current to flow in between. In this case, since the carrier transmittance can be increased, power consumption can be suppressed. Further, when an anion exchange membrane is used as the ion exchange membrane 12, the chlorine ions used as carriers generate chlorine gas by the anodic reaction, but the anodic electrolytic solution contains sulfate ions (SO ₄ ²⁻ ), which causes the anodic reaction. It is possible to suppress the reaction of chlorine ions more than necessary for the above. Specifically, it is possible to prevent chlorine ions in the anode electrolyte from reacting with nitrogen in the air to generate nitrogen trichloride or the like.

  Further, as an advantage of using the anion exchange membrane as the ion exchange membrane 12, it is possible to use the ion exchange electrolysis apparatus which is comparatively often used in the related art as it is, and thus it is possible to suppress the facility cost. .

  The lower limit of the average thickness of the ion exchange membrane 12 is preferably 0.02 mm, more preferably 0.05 mm. On the other hand, the upper limit of the average thickness of the ion exchange membrane 12 is preferably 2 mm, more preferably 0.5 mm. If the average thickness of the ion exchange membrane 12 is less than the above lower limit, the strength of the ion exchange membrane 12 cannot be sufficiently secured, and the ion selectivity (ion exchange capacity) may be reduced. On the contrary, when the average thickness of the ion exchange membrane 12 exceeds the above upper limit, the ion permeability is lowered, so that the current density is lowered and the reaction may be inefficient.

  The anode chamber 11 is divided from the cathode chamber 13 via the ion exchange membrane 12. That is, the ions that can pass through the ion exchange membrane 12 can move between the electrolyte solution on the anode side stored in the anode chamber 11 and the electrolyte solution on the cathode side stored in the cathode chamber 13.

(Cathode chamber)
The cathode chamber 13 has a supply port 16 and a discharge port 17. The supply port 16 is for supplying a titanium tetrachloride solution, and is provided below the cathode chamber 13. The discharge port 17 is for discharging the titanium trichloride solution, and is provided above the cathode chamber 13. That is, the electrolytic cell 1 can continuously produce the titanium trichloride solution by continuously supplying the titanium tetrachloride solution.

  Here, the “titanium tetrachloride solution” includes a titanium solution supplied to the cathode chamber 13 and a titanium solution existing in the cathode chamber 13 (a coexisting solution of titanium tetrachloride and titanium trichloride). The “titanium trichloride solution” refers to a solution containing trivalent titanium ions discharged from the discharge port 17 of the electrolytic cell 1 (cathode chamber 13).

<Anode>
The anode 14 takes out electrons (e ⁻ ) from the anode electrolyte. As a reaction for taking out an electron from the anode electrolyte, a reaction of taking an electron from an anion in the anode electrolyte to oxidize it, and electrolyzing water in the anode electrolyte to generate hydrogen ions and oxygen (O ₂ ). There is a reaction that causes it.

  The anode 14 is formed in a plate shape, for example. Further, the anode 14 is preferably formed as a porous body containing a conductive substance. As the conductive substance, those known as electrode materials can be used, and examples thereof include titanium, conductive carbon, nickel, iridium oxide, and the like, and among these, titanium is preferable. As the anode 14, a conductive material whose surface is coated with a metal having high corrosion resistance, such as platinum, gold or rhodium, may be used.

  By forming the anode 14 in a porous body, the anodic reaction can be promoted, and as a result, the cathodic reaction can be promoted to efficiently produce titanium trichloride.

  The porous body can be formed by a known method. For example, a method in which conductive urethane foam or the like is plated and then baked, a method in which metal powder is adhered to an adhesive-coated urethane foam or the like and then baked, and metal fibers are filled in a mold It can be formed by a method of sintering the molded body later.

  The porosity of the porous body is preferably 30% or more and 99% or less in order to increase the contact area with the anode electrolyte and promote the anodic reaction. Here, the porosity is a value measured according to JIS-Z2501 (2000) "Sintered metal material-Density, oil content and open porosity test method".

  The lower limit of the average thickness of the anode 14 is preferably 0.2 mm, more preferably 0.5 mm. On the other hand, the upper limit of the average thickness of the anode 14 is preferably 5 mm, more preferably 2 mm. If the average thickness of the anode 14 is less than the above lower limit, the electric resistance value of the anode 14 may increase and the number of electrons supplied to the cathode 15 may decrease. On the contrary, when the average thickness of the anode 14 exceeds the above upper limit, the migration distance of molecules in the anode 14 becomes large and the efficiency of the anodic reaction may decrease.

<Cathode>
The cathode 15 reduces tetravalent titanium ions (Ti ⁴⁺ ) to trivalent titanium ions (Ti ³⁺ ), that is, adds electrons to the tetravalent titanium ions. The cathode 15 is formed in a plate shape, for example. The cathode 15 is arranged such that the lower end portion thereof is located in front of the supply port 16 of the electrolytic cell 1. By disposing the cathode 15 in this manner, the titanium tetrachloride solution is supplied from the supply port 16 toward the lower end of the cathode 15. On the other hand, the discharge port 17 is arranged above the supply port 16. Therefore, in the cathode chamber 13, a flow from the lower end to the upper end of the cathode 15 is generated along the surface of the cathode 15, and titanium trichloride generated by the cathode reaction can be efficiently guided to the discharge port 17.

  The cathode 15 is not particularly limited as long as it has conductivity and corrosion resistance to hydrochloric acid, and a conductive metal such as iron, an alloy, graphite or the like is used. Further, as the cathode 15, a conductive metal whose surface is coated with a metal having high corrosion resistance, such as platinum, gold, or rhodium, may be used.

  When the ion exchange membrane 12 is a cation exchange membrane, the titanium trichloride solution manufacturing apparatus is arranged between the ion exchange membrane 12 and the anode 14 to increase the reaction rate of electrolysis of water. It may have a catalyst layer (not shown). This catalyst layer is preferably arranged so as to contact both the anode 14 and the ion exchange membrane 12.

  Thus, the catalyst layer is fixed between the anode 14 and the ion exchange membrane 12, so that water is efficiently supplied to the catalyst layer and hydrogen ions generated by the anodic reaction are efficiently ion-exchange membrane. Through twelve. Therefore, the anode 14 can efficiently receive electrons from water and supply them to the cathode 15, so that titanium tetrachloride can be efficiently reduced. On the other hand, in the cathode chamber 13, since chlorine ions and hydrogen ions produced by the cathode reaction coexist, oxidative deterioration of titanium trichloride produced by the cathode reaction can be effectively suppressed.

  The catalyst layer can be formed, for example, by impregnating the anode 14 or the ion exchange membrane 12 with a solution containing catalyst ions, then stacking the anode 14 and the ion exchange membrane 12 and reducing the catalyst ions. Examples of the material forming the catalyst layer include noble metals such as platinum, rhodium, and iridium oxide.

<Power supply>
The power supply 2 is for applying a DC voltage between the anode 14 and the cathode 15. The power supply 2 is not particularly limited as long as it can apply a predetermined voltage, and a known DC power supply device can be used.

<Anode electrolyte>
As described above, in the anode chamber 11, an aqueous solution containing sulfate ions is stored as the anode electrolyte. As the aqueous solution containing sulfate ions, in addition to sulfuric acid, an aqueous solution of sulfate such as sodium sulfate and calcium sulfate can be used. Further, the anode electrolyte may contain an additive such as an osmotic pressure adjusting agent for adjusting the osmotic pressure difference between the anode chamber 11 and the cathode chamber 13, for example.

  The lower limit of the molar concentration of sulfate ions in the anode electrolyte is preferably 0.05 mol / L, more preferably 0.1 mol / L, and even more preferably 0.2 mol / L. On the other hand, the upper limit of the molar concentration of sulfate ions in the anode electrolyte is preferably 2 mol / L, more preferably 1 mol / L, and even more preferably 0.7 mol / L. If the molar concentration of sulfate ions in the anode electrolyte is less than the above lower limit, the anode reaction may not be promoted sufficiently or the generation of chlorine gas may not be suppressed sufficiently. On the contrary, when the molar concentration of sulfate ion in the anode electrolyte exceeds the above upper limit, the osmotic pressure of the anode electrolyte becomes too high, which may suppress the movement of carriers and reduce the reaction efficiency.

  The anode electrolyte preferably has a low concentration of anions other than sulfate ions. As a lower limit of the ratio of the molar concentration of sulfate ion to the total molar concentration of other anions in the anode electrolyte, 1 is preferable, 10 is more preferable, 20 is further preferable, and 50 is even more preferable. On the other hand, the upper limit of the ratio of the molar concentration of sulfate ions to the total molar concentration of other anions in the anode electrolyte is not particularly limited. If the ratio of the molar concentration of sulfate ion to the total molar concentration of other anions in the anode electrolyte is less than the above lower limit, the generation of chlorine gas due to the anode reaction may not be sufficiently suppressed, or due to other anions. Unfavorable reaction may occur.

  When the ion exchange membrane 12 is a cation exchange membrane, metal ions in the anode electrolyte can move to the cathode electrolyte through the ion exchange membrane 12. Therefore, when the ion exchange membrane 12 is a cation exchange membrane, it is preferable that the total concentration of metal ions in the anode electrolyte is as low as possible. The upper limit of the total molar concentration of metal ions in the anode electrolyte is preferably 1/10 of the molar concentration of sulfate ions, more preferably 1/20, and even more preferably 1/50. When the total molar concentration of the metal ions in the anode electrolyte exceeds the above upper limit, the metal ions in the anode electrolyte move into the cathode electrolyte and titanium is reduced by consuming and reducing the electrons supplied from the cathode. There is a possibility that the reduction of ions may be hindered or that the quality may be deteriorated by being mixed as an impurity in the obtained titanium trichloride solution.

  Examples of the osmotic pressure adjusting agent that may be contained in the anode electrolyte include citric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, tartaric acid, malic acid, fumaric acid, maleic acid, itaconic acid, phthalic acid. , Isophthalic acid, terephthalic acid, salts thereof, and the like, and one kind or a combination of two or more kinds thereof can be used. The addition amount of the osmotic pressure adjusting agent is determined depending on, for example, the target osmotic pressure adjusting agent, the type of the osmotic pressure adjusting agent used, and the like, and is, for example, more than 0 mol / L and 2 mol / L or less. When the addition amount of the osmotic pressure adjusting agent exceeds the above upper limit, ions other than titanium ions may be increased in the cathode electrolytic solution and the reduction of titanium ions may be hindered.

<Cathode electrolyte>
As described above, the cathode chamber 13 is supplied with a titanium tetrachloride solution that produces a titanium trichloride solution by electrolytic reduction as the cathode electrolyte. The cathode electrolyte preferably contains hydrochloric acid. It is preferable that an oxidation inhibitor that suppresses the oxidation of trivalent titanium ions generated by electrolytic reduction to tetravalent titanium ions is added to the titanium tetrachloride solution before electrolysis that is supplied to the cathode chamber 13. . The supply flow rate of the titanium tetrachloride solution to the electrolytic cell 1 (cathode chamber 13) is, for example, the ratio of the concentration of trivalent titanium ions at the outlet 17 to the total amount of trivalent titanium ions and tetravalent titanium ions. Therefore, it is preferably set to 90 mol% or more, more preferably about 100 mol%.

  The lower limit of the titanium ion concentration (total concentration of trivalent titanium ions and tetravalent titanium ions) of the cathode electrolyte is preferably 0.05 mol / L, more preferably 0.1 mol / L, and 0.2 mol. / L is more preferable. On the other hand, the upper limit of the titanium ion concentration of the cathode electrolyte is preferably 2 mol / L, more preferably 1 mol / L, and even more preferably 0.7 mol / L. If the titanium ion concentration of the cathode electrolyte is less than the above lower limit, the cathode reaction may not be sufficiently promoted, or the concentration of the titanium trichloride solution obtained may be insufficient. On the contrary, when the concentration of titanium ions in the cathode electrolyte exceeds the above upper limit, the amount of unreacted titanium tetrachloride increases, and the quality of the titanium trichloride solution obtained may be insufficient.

  The upper limit of the concentration of hydrochloric acid is not particularly limited, but 2 mol / L is preferable. On the other hand, the lower limit of the concentration of hydrochloric acid is preferably 0.5 mol / L, more preferably 1.5 mol / L. By containing hydrochloric acid in the above concentration, the titanium trichloride solution can more effectively suppress the oxidative deterioration of trivalent titanium ions and has excellent storage stability.

  The oxidation inhibitor is preferably a carboxylic acid having two or more carboxyl groups or a salt of this carboxylic acid. These carboxylic acids or carboxylic acid salts coordinate with trivalent titanium ions to form a titanium complex. This reduces the frequency with which trivalent titanium ions and oxygen approach each other, and effectively suppresses the oxidation of trivalent titanium ions.

  Examples of the oxidation inhibitor include citric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, tartaric acid, malic acid, fumaric acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and the like. Salts and the like can be mentioned, and one kind or a combination of two or more kinds thereof can be used.

  The lower limit of the molar concentration of the oxidation inhibitor in the titanium tetrachloride solution (cathode electrolyte solution before electrolysis) supplied to the cathode chamber 13 is the total of trivalent titanium ions and tetravalent titanium ions in the cathode electrolyte solution. The molar concentration is preferably 0.1 times, more preferably 0.15 times. On the other hand, the upper limit of the molar concentration of the oxidation inhibitor in the titanium tetrachloride solution supplied to the cathode chamber 13 is preferably twice the total molar concentration of the titanium ions, more preferably 1.5 times. If the molar concentration of the oxidation inhibitor in the titanium tetrachloride solution supplied to the cathode chamber 13 is less than the above lower limit, the oxidation of trivalent titanium ions may not be sufficiently suppressed. On the contrary, when the molar concentration of the oxidation inhibitor in the titanium tetrachloride solution supplied to the cathode chamber 13 exceeds the above upper limit, reduction of tetravalent titanium ions and movement of carriers between the anode chamber 11 and the cathode chamber 13 are prevented. May interfere.

  Further, it is preferable to further add an oxidation inhibitor to the titanium trichloride solution (cathode electrolyte solution after electrolysis) generated in the cathode chamber 13. In particular, when an anion exchange membrane is used as the ion exchange membrane 12, chlorine ions in the cathode electrolyte move to the anode chamber 11, and trivalent titanium ions in the cathode electrolyte are oxidized to titanium oxide. Since the function of suppressing chloride by chloride ions is likely to decrease, it is more effective to add an oxidation inhibitor to the cathode electrolyte after the electrolytic reaction in order to maintain the concentration of trivalent titanium ions.

  The lower limit of the molar concentration of the oxidation inhibitor in the titanium trichloride solution to which the oxidation inhibitor has been added after electrolysis is 0. with respect to the total molar concentration of trivalent titanium ions and tetravalent titanium ions in the cathode electrolyte. 3 times is preferable and 0.4 times is more preferable. On the other hand, the upper limit of the molar concentration of the oxidation inhibitor in the titanium trichloride solution is preferably 5 times, more preferably 2 times, the total molar concentration of the titanium ions. If the molar concentration of the oxidation inhibitor in the titanium trichloride solution is less than the above lower limit, the oxidation of trivalent titanium ions may not be sufficiently suppressed. On the contrary, when the molar concentration of the oxidation inhibitor in the titanium trichloride solution exceeds the above upper limit, the cost may be unnecessarily increased or the use of the obtained titanium trichloride solution may be limited.

[Method for producing titanium trichloride]
Then, the manufacturing method of the titanium trichloride solution which concerns on another embodiment of this invention which can be performed using the said titanium trichloride solution manufacturing apparatus is demonstrated.

  The method for producing the titanium trichloride solution is a method for producing a titanium trichloride solution in which titanium tetrachloride in the electrolytic solution is reduced by an ion exchange electrolytic reduction method.

  In the method for producing the titanium trichloride solution, an aqueous solution containing sulfate ions is used as the electrolytic solution on the anode 14 side, as described above with respect to the titanium trichloride solution producing apparatus. That is, in the titanium trichloride manufacturing method, an aqueous solution containing sulfate ions is stored in the anode chamber 11, a titanium tetrachloride solution is stored in the cathode chamber 13, and a voltage is applied between the anode 14 and the cathode 15. Thus, titanium tetrachloride in the cathode chamber 13 is electrolytically reduced to produce a titanium trichloride solution.

<Application of voltage>
The voltage is applied by the power supply 2. The applied voltage is preferably 3 V or more and 10 V or less, and is typically 5 V. The current density is preferably from 20 mA / cm ² or more 40 mA / cm ² or less, and typically are 30 mA / cm ^2.

  The method for producing the titanium trichloride solution preferably has a step of adding an oxidation inhibitor to the cathode chamber 13. That is, in the method for producing the titanium trichloride solution, preferably the cathode electrolyte before electrolysis or the cathode electrolyte after electrolysis, more preferably the cathode electrolyte after electrolysis and after the electrolysis, so that the above-mentioned molar concentration is obtained. It is preferable to add an oxidation inhibitor. Thereby, the storage stability of the manufactured titanium trichloride solution can be improved.

<Advantages>
The apparatus for producing the titanium trichloride solution and the method for producing the titanium trichloride solution use an aqueous solution containing sulfate ions as the electrolyte solution on the anode 14 side, thereby suppressing the chloride ion concentration of the electrolyte solution on the anode 14 side to be low. It is possible to prevent chlorine and chloride from being unnecessarily generated and suppress the amount of chlorine-based gas generated.

[Other Embodiments]
The embodiments disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is not limited to the configurations of the above-described embodiments, but is defined by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

  In the titanium trichloride solution manufacturing apparatus, the anode or the cathode may have a gas passage that allows a gas generated in the electrolytic reduction reaction to pass therethrough.

  In addition, the titanium trichloride solution manufacturing apparatus may not be equipped with a power supply device, and a voltage may be applied from the outside.

  Further, in the above embodiment, the case where the titanium tetrachloride solution is continuously supplied to the electrolytic cell has been described. However, the titanium trichloride solution is produced from the titanium tetrachloride solution in a batch system (batch system). Good.

  Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limitedly interpreted based on the description of the examples.

  Using the manufacturing apparatus according to the manufacturing apparatus of the titanium trichloride solution of FIG. 1, the manufacturing conditions were changed and the trial manufacture examples 1-5 of the titanium trichloride solution were manufactured. The titanium trichloride solution manufacturing apparatus was placed in a closed space so that changes in the chlorine gas concentration in this space could be confirmed.

(Prototype example 1)
Anion exchange membrane is used as an ion exchange membrane, an aqueous solution containing 0.4 mol / L titanium tetrachloride as a cathode electrolyte, 1.0 mol / L hydrochloric acid and 0.08 mol / L trisodium citrate as an oxidation inhibitor. Was used and electrolytic reduction was performed using a 0.4 mol / L sodium sulfate aqueous solution as an anode electrolyte to produce a titanium trichloride solution. A trial production example 1 of titanium trichloride solution was obtained by adding 0.2 mol of trisodium citrate per 1 L of the cathode electrolyte as an oxidation inhibitor to the cathode electrolyte immediately after the electrolytic reduction.

(Prototype example 2)
Trial production of titanium trichloride solution under the same conditions as in Prototype Example 1 above, except that 0.4 mol / L sulfuric acid containing no metal ions was used as the anode electrolyte and a cation exchange membrane was used as the ion exchange membrane. Example 2 was obtained.

(Prototype example 3)
Prototype Example 3 of titanium trichloride solution was obtained under the same conditions as in Prototype Example 1 above, except that the amount of trisodium citrate added immediately after electrolytic reduction was 0.1 mol per 1 L of the cathode electrolyte.

(Prototype example 4)
A trial production example 4 of a titanium trichloride solution was obtained under the same conditions as the trial production example 1 except that trisodium citrate was not added after the electrolytic reduction.

(Prototype example 5)
Prototype Example 5 of titanium trichloride solution was obtained under the same conditions as in Prototype Example 1 above, except that 0.4 mol / L hydrochloric acid was used as the anode electrolyte.

(Chlorine gas concentration)
Immediately before the end of electrolytic reduction in the production of the above-mentioned titanium trichloride solution prototypes 1 to 5, the chlorine concentration in the closed space in which the titanium trichloride solution production apparatus was placed was measured by using a gas detector "Gas Alert Extreme" by Zicco. "GAXT-C-DL".

(Storage test)
Prototype Examples 1 to 5 of the titanium trichloride solution were stored for 3600 hours, and the trivalent titanium ion concentration before and after storage was based on JIS-K0050 (2011), and redox titration using a cerium sulfate solution (IV). The ratio of the trivalent titanium ion concentration after storage to the trivalent titanium ion concentration immediately after production (shown in Table 1 as the titanium ion concentration ratio after storage) was calculated. In addition, the state of the titanium trichloride solution after storage was visually confirmed to determine whether or not a titanium oxide (TiO ₂ ) precipitate was formed.

  Table 1 below collectively shows the production conditions of the above-mentioned trial production examples 1 to 5 of the titanium trichloride solution, the measurement result of the chlorine gas concentration and the result of the storage test. In the table, “> 500 ppm” in the chlorine gas concentration at the end of electrolysis means that the upper limit of the detection limit of the gas detector used was 500 ppm.

  As shown in Table 1, in Prototype Examples 1 to 4 using an aqueous solution containing sulfate as the anode electrolyte, the chlorine gas concentration at the end of electrolysis was 300 ppm or less, and it was confirmed that the generation of chlorine gas can be suppressed. . Particularly, in Prototype Example 2 in which a cation exchange membrane was used as the ion exchange membrane and sulfuric acid containing no metal ions was used as the anode electrolyte, the chlorine gas concentration at the end of electrolysis was 1 ppm or less, and the generation amount of chlorine gas was large. It was confirmed that it could be reduced. In addition, referring to Prototype Examples 1, 3, and 4, by adding an oxidation inhibitor immediately after electrolytic reduction, the generation of titanium oxide precipitates in the titanium trichloride solution after storage was prevented, and trivalent titanium was obtained. It was found that the ion concentration can be increased.

1 Electrolyzer 2 Power Supply 11 Anode Chamber 12 Ion Exchange Membrane 13 Cathode Chamber 14 Anode 15 Cathode 16 Supply Port 17 Discharge Port

Claims (8)

A method for producing a titanium trichloride solution in which titanium tetrachloride in an electrolytic solution is reduced by an ion exchange electrolytic reduction method using a production apparatus for a titanium trichloride solution,
The manufacturing apparatus is an anode chamber that stores an anode electrolyte, is partitioned by the ion exchange membrane with the anode chamber, a cathode chamber that stores a cathode electrolyte containing the titanium tetrachloride solution and titanium trichloride solution, and the anode chamber An anode immersed in an anode electrolyte, and a cathode immersed in the cathode electrolyte of the cathode chamber,
As the positive electrode electrolytic solution, an aqueous solution containing sulfate ions,
Having a step of adding an oxidation inhibitor to the titanium trichloride solution,
The sulfate ion has a molar concentration of 0.05 mol / L or more and 2 mol / L or less,
The concentration of titanium ions in the cathode electrolyte is 0.05 mol / L or more and 2 mol / L or less,
The molar concentration of the oxidation inhibitor in the titanium trichloride solution added with the oxidation inhibitor is 0.3 times or more the total molar concentration of trivalent titanium ions and tetravalent titanium ions in the cathode electrolyte. 5 times or less,
The average thickness of the anode is 0.2 mm or more and 5 mm or less,
Method for producing a titanium trichloride solution applied voltage is Ru der more than 10V 3V between the anode and cathode.
  The method for producing a titanium trichloride solution according to claim 1, wherein a molar concentration of the sulfate ion in the electrolyte solution on the anode side is equal to or higher than a total molar concentration of other anions.   The method for producing a titanium trichloride solution according to claim 1 or 2, wherein the ion exchange membrane is a cation exchange membrane.   The method for producing a titanium trichloride solution according to claim 3, wherein the total molar concentration of the metal ions in the electrolyte solution on the anode side is 1/10 or less of the molar concentration of the sulfate ions.   The method for producing a titanium trichloride solution according to claim 1 or 2, wherein the ion exchange membrane is an anion exchange membrane.   The method for producing a titanium trichloride solution according to any one of claims 1 to 5, further comprising a step of adding an oxidation inhibitor to the electrolyte solution on the cathode side.   The method for producing a titanium trichloride solution according to claim 6, wherein a carboxylic acid having two or more carboxyl groups or a salt of this carboxylic acid is used as the oxidation inhibitor. An apparatus for producing a titanium trichloride solution by electrolytic reduction of titanium tetrachloride in an aqueous solution,
Anode chamber for storing the anode electrolyte, the anode chamber is partitioned with the ion exchange membrane, the cathode chamber for storing the cathode electrolyte containing the titanium tetrachloride solution and titanium trichloride solution, immersed in the anode electrolyte of the anode chamber And an anode that is immersed in the cathode electrolyte of the cathode chamber,
The anode electrolyte is seen containing a sulfuric acid ion,
The sulfate ion has a molar concentration of 0.05 mol / L or more and 2 mol / L or less,
The concentration of titanium ions in the cathode electrolyte is 0.05 mol / L or more and 2 mol / L or less,
The molar concentration of the oxidation inhibitor added to the titanium trichloride solution is 0.3 times or more and 5 times or less with respect to the total molar concentration of trivalent titanium ions and tetravalent titanium ions in the cathode electrolyte. Yes,
The average thickness of the anode is 0.2 mm or more and 5 mm or less,
An apparatus for producing a titanium trichloride solution in which a voltage applied between the anode and the cathode is 3 V or more and 10 V or less .

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