Method of producing anhydrous aluminum chloride

Abstract

To provide a method of producing AlCl3 for distilling a molten salt of chlorides including AlCl3 under reduced pressure at a temperature far below the melting point of AlCl3 single salt to reduce the water content therein to 100 ppm or below.SOLUTION: The method of producing anhydrous AlCl3 comprises a step 1 of heating an evaporator storing room temperature molten salt consisting of 35 to 70 mol% of AlCl3 and 65 to 30 mol% of onium chloride, i. e., 1,3-dimethylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride (EMIC), 1-methyl-3-propylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-methyl-3-pentylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-heptyl-3-methylimidazolium chloride, or 1-methyl-3-octylimidazolium chloride (total 100 mol% of AlCl3 and onium chloride) at a temperature of 30 to 80°C and at a pressure of 0.01 to 8 Pa to vaporize AlCl3 from the room temperature molten salt, and a step 2 of cooling the vapor of AlCl3 in the gas phase to solidify the same to recover AlCl3 having a water content of 100 ppm or below.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing high purity anhydrous aluminum chloride. [Background technology]

[0002] Anhydrous aluminum chloride is widely used as a catalyst for the isomerization or dehydrogenation of hydrocarbons, the Friedel-Crafts reaction, or cracking. Anhydrous aluminum chloride is generally produced by blowing chlorine gas into molten aluminum and solidifying the sublimated aluminum chloride gas in a cooler. This method requires a high reaction temperature because aluminum and chlorine gas react directly. Therefore, the small amount of moisture, oxygen, or carbon dioxide contained in chlorine gas reacts with high-temperature aluminum to generate hydrogen gas, or generate aluminum oxide or carbon powder, which causes a decrease in purity and yield in the production of high-purity aluminum.

[0003] Pure anhydrous aluminum chloride is a white solid, but industrially produced anhydrous aluminum chloride is pale yellow to gray. When the hue is pale yellow, other metal chlorides are mainly mixed in, and when it is gray, raw aluminum and amorphous carbon are mixed in. As a method for removing such impurities, a method has been disclosed in which purified chlorine gas with a carbon dioxide content reduced to 20 ppm by volume or less is introduced into molten aluminum kept at 700 to 800°C in a reactor, and the generated aluminum chloride gas is solidified in a cooler to recover solid anhydrous aluminum chloride (Patent Document 1).

[0004] In addition, when producing high-purity anhydrous aluminum chloride that meets the requirements for a raw material for lithium batteries, the aluminum chloride that is produced and recovered is purified again by sublimation. However, since solid aluminum chloride is reheated, the thermal efficiency and productivity are low, which is a problem. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3528424 [Patent Document 2] Patent No. 6-263438 [Non-patent literature]

[0006] [Non-Patent Document 1] Mikito Ueda and Koichi Ui, "Surface Technology", Vol. 60, pp. 491-496, 2009 Summary of the Invention [Problem to be solved by the invention]

[0007] However, aluminum chloride is a sublimable substance, and a molten salt cannot be formed from aluminum chloride alone. Therefore, when forming a molten salt of aluminum chloride at room temperature, aluminum chloride, which is a Lewis acid, is mixed with an inorganic chloride or an organic chloride, which is a Lewis base. According to Non-Patent Document 1, the melting points of each material, aluminum chloride, 1-butylpyridinium chloride (BPC), and 1-ethyl-3-methylimidazolium chloride (EMIC), are much higher than room temperature, but the melting point of a mixed salt of aluminum chloride and BPC, or a mixed salt of aluminum chloride and EMIC, is lower than room temperature, and aluminum chloride can be distilled at a lower temperature by further adjusting the pressure conditions. Patent Document 2 reports a method in which a room temperature molten salt consisting of EMIC and crude aluminum chloride is charged into a flask equipped with a cooling tube, heated to 120°C under a nitrogen gas flow at normal pressure, aluminum chloride is distilled, and a white solid attached to the cooling tube is collected.

[0008] The present invention aims to provide a method for producing anhydrous aluminum chloride having a water content reduced to 100 ppm or less, which comprises distilling a chloride molten salt containing aluminum chloride under reduced pressure at a temperature much lower than the melting point of aluminum chloride simple salt. [Means for solving the problem]

[0009] The method for producing anhydrous aluminum chloride of the present invention comprises, in an evaporation apparatus having at least an evaporator and a vacuum pump, dissolving 35 to 70 mol % of aluminum chloride and an onium chloride selected from the group consisting of 1,3-dimethylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride (EMIC), 1-methyl-3-propylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-methyl-3-pentylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-heptyl-3-methylimidazolium chloride and 1-methyl-3-octylimidazolium chloride. The method comprises the steps of: step 1, heating an evaporator containing a room-temperature molten salt composed of 65 to 30 mol % of aluminum chloride and an onium chloride at a temperature of 30 to 80° C. and a reduced pressure of 0.01 to 8 Pa to vaporize aluminum chloride from the room-temperature molten salt; and step 2, cooling and solidifying the aluminum chloride vapor in the gas phase to recover aluminum chloride having a moisture content of 100 ppm or less.

[0010] It is preferable that the evaporation apparatus further includes a gas inlet pipe for supplying a carrier gas and a gas outlet pipe, and during steps 1 and 2, the carrier gas is introduced into the room-temperature molten salt through the gas inlet pipe, and gas-liquid contact between the carrier gas and the room-temperature molten salt is performed by bubbling.

[0011] The method for producing anhydrous aluminum chloride of the present invention comprises, in an evaporation apparatus comprising at least an evaporator, a gas inlet pipe for supplying a carrier gas, and a gas outlet pipe, step 1 of heating the evaporator containing the room-temperature molten salt at a temperature of 30 to 80°C to vaporize aluminum chloride from the room-temperature molten salt, and step 2 of cooling and solidifying the aluminum chloride vapor in the gas phase to recover aluminum chloride having a moisture content of 100 ppm or less, characterized in that during steps 1 and 2, a carrier gas is introduced into the room-temperature molten salt through the gas inlet pipe, and gas-liquid contact is performed between the carrier gas and the room-temperature molten salt by bubbling.

[0012] The method for producing anhydrous aluminum chloride of the present invention comprises, in an evaporator equipped with at least an evaporator, a bottom filter for gas injection for supplying a carrier gas, and a gas outlet pipe, step 1 of heating the evaporator containing the room-temperature molten salt at a temperature of 30 to 80°C to vaporize aluminum chloride from the room-temperature molten salt, and step 2 of cooling and solidifying the aluminum chloride vapor in the gas phase to recover aluminum chloride having a moisture content of 100 ppm or less, characterized in that during steps 1 and 2, a carrier gas is introduced into the room-temperature molten salt through the bottom filter for gas injection, and gas-liquid contact between the carrier gas and the room-temperature molten salt is performed by bubbling.

[0013] The method for producing anhydrous aluminum chloride of the present invention comprises, in an evaporator equipped with at least an evaporator, a vacuum pump, a gas-blowing bottom filter for supplying a carrier gas, and a gas outlet pipe, step 1 in which the evaporator containing the room-temperature molten salt is heated at a temperature of 30 to 80°C and under a reduced pressure of 0.01 to 8 Pa to vaporize aluminum chloride from the room-temperature molten salt, and step 2 in which the aluminum chloride vapor in the gas phase is cooled and solidified to recover aluminum chloride having a moisture content of 100 ppm or less, and is characterized in that during steps 1 and 2, a carrier gas is introduced into the room-temperature molten salt through the gas-blowing bottom filter, and gas-liquid contact between the carrier gas and the room-temperature molten salt is performed by bubbling.

[0014] The bottom filter for gas injection is preferably made of diffusion brick or glass fiber. Preferably, the onium chloride is 1-ethyl-3-methylimidazolium chloride (EMIC). Effect of the Invention

[0015] According to the present invention, when distilling anhydrous aluminum chloride, a room-temperature molten salt containing aluminum chloride and an onium chloride in a specific composition ratio is used, whereby aluminum chloride having a water content of 100 ppm can be efficiently produced under reduced pressure conditions of 0.01 to 8 Pa and low temperature conditions of 30 to 80°C. In addition, when distilling anhydrous aluminum chloride, a carrier gas is introduced and bubbled in the room temperature molten salt in an evaporator, so that aluminum chloride with a water content of 100 ppm can be produced at a low temperature of 30 to 80°C even under atmospheric pressure. The aluminum chloride obtained by the manufacturing method of the present invention has an extremely low water content, so it can be used as a highly reactive Lewis acid in the Friedel-Crafts reaction. In addition, since it has an extremely low amount of metal impurities, it is also useful as a precursor when forming an alumina film on a semiconductor substrate, and can improve the electrical properties of the resulting semiconductor multilayer film. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic cross-sectional view of an evaporation device 100 used in Example 1, Example 2, Comparative Example 3, and Comparative Example 4. [Diagram 2] FIG. 2 is a schematic cross-sectional view of an evaporation device 200 used in the third embodiment. [Diagram 3] FIG. 3 is a schematic cross-sectional view of an evaporation device 300 used in the fourth embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view of an evaporation device 400 used in the fifth embodiment. [Diagram 5] FIG. 5 is a schematic cross-sectional view of an evaporation device 500 used in Example 6. [Figure 6]FIG. 6 is a schematic cross-sectional view of an evaporation device 600 used in Comparative Examples 1 and 2. As shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The process for producing anhydrous aluminum chloride of the present invention will now be described in detail. The method for producing anhydrous aluminum chloride of the present invention is a method for reducing the water content of aluminum chloride to 100 ppm or less, and comprises dissolving 35 to 70 mol % of aluminum chloride and an onium chloride selected from the group consisting of 1,3-dimethylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride (EMIC), 1-methyl-3-propylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-methyl-3-pentylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-heptyl-3-methylimidazolium chloride and 1-methyl-3-octylimidazolium chloride in an evaporator. The method includes a step 1 of heating an evaporator containing a room-temperature molten salt composed of 65 to 30 mol % of aluminum chloride and an onium chloride at a temperature of 30 to 80°C under a reduced pressure of 0.01 to 8 Pa to vaporize aluminum chloride from the room-temperature molten salt, and a step 2 of cooling the aluminum chloride vapor in the gas phase and recovering the solidified aluminum chloride.

[0018] First, the room temperature molten salt, which is the evaporation material in the present invention, will be described. The room temperature molten salt is a mixture of aluminum chloride and the onium chloride. Here, the mixture of aluminum chloride and the onium chloride can be solid or liquid depending on the mixing ratio and temperature. According to the equilibrium phase diagram of aluminum chloride and EMIC in a mixing ratio of 7:3 (AlCl3:EMIC=70 mol %:30 mol %) described in J. Phys. Chem., 88, 2614 (1984), a mixture of aluminum chloride and 1-ethyl-3-methylimidazolium chloride (EMIC) is a solid mixture at room temperature, but becomes liquid when heated to 100°C. On the other hand, a mixture of aluminum chloride and EMIC in an equimolar ratio is liquid at room temperature. J. Phys. Chem., 88, 2614 (1984) shows that when a room-temperature molten salt containing aluminum chloride and EMIC in an equimolar ratio is distilled at a vacuum degree of 0.01 to 8 Pa and a distiller temperature of 30 to 80°C, the water content of the aluminum chloride captured in a cooler 3 is low. Therefore, in the present invention, an anhydrous aluminum chloride having an extremely low water content of 10 ppm is produced by using a room-temperature molten salt obtained by mixing aluminum chloride and the above-mentioned onium chloride in a specific ratio as an evaporation raw material and distilling aluminum chloride under specific conditions.

[0019] The aluminum chloride in the present invention refers to aluminum chloride before steps 1 and 2 are performed, i.e., commercially available aluminum chloride. In one commercially available aluminum chloride product, the water content determined by Karl Fischer titration is 654 ppm, and the metal impurities determined by high-frequency inductively coupled plasma (ICP) atomic emission spectrometry are 11 ppm iron, 5 ppm nickel, 2 ppm chromium, 3 ppm sodium, 6 ppm zinc, 2 ppm lead, 2 ppm potassium, and 3 ppm copper (Table 1). In the present invention, high-purity anhydrous aluminum chloride is produced from a chloride-based mixed molten salt containing commercially available aluminum chloride.

[0020] As the onium chloride, 1,3-dimethylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride (EMIC), 1-methyl-3-propylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-methyl-3-pentylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-heptyl-3-methylimidazolium chloride, or 1-methyl-3-octylimidazolium chloride is used. The onium chloride may be used alone or in combination of two or more kinds, but it is more preferable to use EMIC alone.

[0021] The composition of the evaporation raw material is 35-70 mol % of aluminum chloride and 65-30 mol % of onium chloride, with the total of aluminum chloride and onium chloride being 100 mol %. That is, as the evaporation raw material according to the present invention, a room-temperature molten salt with an aluminum chloride molar fraction of 0.35-0.7 is used. Preferably, the room-temperature molten salt according to the present invention contains 40 to 60 mol % aluminum chloride and 60 to 40 mol % onium chloride, based on a total of 100 mol % aluminum chloride and onium chloride. That is, a room-temperature molten salt having a molar fraction of aluminum chloride of 0.4 to 0.6 is preferred.

[0022] Next, an embodiment of anhydrous aluminum chloride of the present invention will be described with reference to Figures 1 to 5. Figures 1 to 5 are schematic cross-sectional views showing an embodiment of the present invention. Note that the present invention is not limited to these embodiments, and appropriate modifications and improvements based on the ordinary knowledge of a person skilled in the art are also included within the scope of the present invention, provided that they do not deviate from the gist of the present invention.

[0023] 1 is a schematic cross-sectional view of an evaporation apparatus 100 according to a first embodiment of the present invention. In the evaporation apparatus 100, an evaporator 1 is a container for evaporating aluminum chloride from the evaporation raw material by putting aluminum chloride and the onium chloride into the container. A heater 2 is provided so as to surround the side and bottom of the evaporator 1, and heats the evaporator 1 to vaporize aluminum chloride from the room-temperature molten salt.

[0024] The cooler 3 is used to heat the evaporator 1 with the heater 2, cool the aluminum chloride vapor vaporized from the evaporation material below the melting point, and solidify and adhere to the inner wall surface. The cooler 3 is usually cylindrical, but may be a triangular or square tube. Alternatively, in order to increase the contact area between the cooler 3 and the aluminum chloride vapor, the inside of the cylindrical cooler 3 may be shaped like a number of gourds connected together, or may be shaped with piping for flowing a refrigerant inside the cylindrical cooler 3. When contacting the aluminum chloride vapor, the temperature of the cooler 3 is preferably maintained between -70°C and room temperature, which can be adjusted using dry ice.

[0025] The heater 2 is used to heat the evaporator 1 and increase the evaporation rate of aluminum chloride. The heating temperature is set to 30 to 80° C., preferably 50 to 70° C. If the heating temperature exceeds 80° C., the evaporation rate of aluminum chloride increases, but at the same time, moisture contained in the evaporation raw material in small amounts also evaporates, and this moisture may be mixed into the aluminum chloride captured in the cooler 3.

[0026] The aluminum chloride vapor is cooled and solidified by contacting the inner wall of the cooler 3. The solidified matter adheres to and accumulates on the inner wall. As aluminum chloride accumulates inside the cooler 3, its inner diameter gradually narrows. When the cooler 3 becomes clogged with the deposits, the distillation of aluminum chloride stops.

[0027] The vacuum pump 4 creates a low vacuum (10 5 ~10 2 Pa) ~ High vacuum (10 -1 ~10 -5The pressure inside the evaporator 100 is reduced to a range of 0.01 to 8 Pa, preferably 0.5 to 5 Pa, since the vapor pressure of aluminum chloride at 50 to 70°C is 9.32 to 30.7 kPa. The pressure inside the evaporator 100 is adjusted by a pressure gauge 5 installed between the vacuum pump 4 and the evaporator 1. When the molar fraction of aluminum chloride is 0.35 to 0.7, a room-temperature molten salt is formed under atmospheric pressure at room temperature, and therefore aluminum chloride can be efficiently evaporated under the reduced pressure conditions described above.

[0028] 2 is a schematic cross-sectional view of an evaporation apparatus 200 according to a second embodiment of the present invention. In the evaporation apparatus 200, the distiller 1, the heater 2, and the cooler 3 are the same as those in the first embodiment. The evaporation apparatus 200 is provided with a gas inlet pipe 6 for supplying a carrier gas to the evaporation raw material, and a gas outlet pipe 7 for discharging the carrier gas and unsolidified aluminum chloride vapor. The second embodiment is carried out under atmospheric pressure, and therefore does not include a vacuum pump 4 and a pressure gauge 5, unlike the first embodiment.

[0029] The gas injection pipe 6 is provided from any position on the upper side or ceiling of the cooler 3 toward the surface of the evaporation raw material, and its tip is inserted into the evaporation raw material. When the inlet of the gas injection pipe 6 is located at any position on the upper side of the cooler 3, the gas injection pipe 6 is L-shaped or curved. The evaporation raw material is bubbled with the carrier gas supplied from the gas injection pipe 6. As the carrier gas, nitrogen gas or an inert gas (argon, helium, neon, krypton, xenon) is used, and nitrogen gas or argon gas is preferable. In the carrier gas bubbled into the evaporation raw material, aluminum chloride vapor vaporized from the evaporation raw material diffuses, and the aluminum chloride vapor and the carrier gas are mixed. This mixed gas scatters from the surface of the evaporation raw material and adheres to the wall surface of the cooler 3 and solidifies. A part of the aluminum chloride in the gas phase that has not solidified is discharged to the outside of the evaporation device 200 through the gas outlet pipe 7.

[0030] FIG. 3 is a cross-sectional schematic diagram of an evaporation apparatus 300 according to a third embodiment of the present invention. In the evaporation apparatus 300, the distiller 1, the heater 2, and the cooler 3 are the same as those in the first embodiment. In the evaporation apparatus 300, instead of the gas blowing pipe 6 in the second embodiment, a bottom filter 8 for blowing gas is provided at the bottom, and the evaporation raw material is bubbled with the carrier gas supplied through the bottom filter 8 for blowing gas. As in the second embodiment, the mixed gas of aluminum chloride vapor and carrier gas adheres to and solidifies on the wall surface of the cooler 3 to obtain the desired aluminum chloride. Note that the evaporation apparatus 300 also has a gas outlet pipe 7 for discharging the carrier gas and the unsolidified aluminum chloride vapor.

[0031] The material of the gas blowing bottom filter 8 is preferably a so-called sponge structure having pores connected in a three-dimensional network in terms of passing the carrier gas, but on the other hand, it is preferable that the pore density is small in terms of holding the evaporation raw material, which is in a liquid phase, on the gas blowing bottom filter 8 without seeping out. Suitable materials for the gas blowing bottom filter 8 that satisfy such requirements include glass fiber or glass powder compressed and molded, diffusion bricks, etc. Of these, diffusion bricks are advantageous in terms of their excellent heat resistance.

[0032] When the carrier gas passes through the gas blowing bottom filter 8, it is diffused into the evaporation raw material as fine bubbles. The mixed gas of the carrier gas and aluminum chloride vapor that has become fine bubbles adheres to the wall surface of the cooler 3 as cloudy vapor in which some of the aluminum chloride is condensed and solidifies. A portion of the aluminum chloride vapor that has not solidified is discharged to the outside of the evaporation device 300 from the gas outlet pipe 7.

[0033] 4 is a schematic cross-sectional view of an evaporation apparatus 400 according to a fourth embodiment of the present invention. In the evaporation apparatus 400, the distiller 1, the heater 2, the cooler 3, the gas inlet pipe 6, and the gas outlet pipe 7 are the same as those in the first and second embodiments. The fourth embodiment is a configuration in which a vacuum pump 4 and a pressure gauge 5 are provided between the vacuum pump 4 and the evaporator 1 in order to evaporate aluminum chloride from the room-temperature molten salt under reduced pressure in the third embodiment.

[0034] The inside of the evaporation device 100 is made into a low vacuum (10 5 ~10 2 Pa) ~ High vacuum (10 -1 ~10 -5 The pressure inside the evaporator 400 is adjusted to the required reduced pressure condition using a pressure gauge 5.

[0035] 5 is a schematic cross-sectional view of an evaporation device 500 according to a fifth embodiment of the present invention. The fifth embodiment is an embodiment in which a gas blowing bottom filter 8 is provided at the bottom of the evaporator 1 in the first embodiment.

[0036] In the fifth embodiment, the evaporation of aluminum chloride from the room temperature molten salt is performed under reduced pressure, so the inside of the evaporation device 100 is made into a low vacuum (10 5 ~10 2 Pa) ~ High vacuum (10 -1 ~10 -5 The pressure is reduced to a range of 0.01 to 8 Pa, specifically 0.01 to 8 Pa, and the inside of the evaporator 500 is adjusted to the required reduced pressure conditions using a pressure gauge 5. By supplying a carrier gas through a bottom filter 8 for gas blowing under reduced pressure, the carrier gas is diffused into the evaporation raw material as fine bubbles, and the mixed gas with the aluminum chloride vapor adheres to the wall surface of the cooler 3 as cloudy vapor and solidifies. A portion of the aluminum chloride vapor that has not solidified is discharged to the outside of the evaporator 300 from a gas outlet pipe 7.

[0037] 6 is a schematic cross-sectional view of an evaporation device 600 according to a conventional embodiment. In the conventional embodiment, unlike the first to fifth embodiments, aluminum chloride is evaporated from the evaporation raw material under atmospheric pressure rather than reduced pressure. Since the gas blowing pipe 6 is not inserted into the evaporation raw material, the evaporation raw material is not bubbled with the carrier gas supplied from the gas blowing pipe 6 during steps 1 and 2, and the aluminum chloride vapor adheres to and solidifies on the wall surface of the cooler 3 in an inefficient manner. EXAMPLES

[0038] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to the following examples. [Example 1] In the evaporator 100 shown in FIG. 1, 45 mol % (600 g) of aluminum chloride with a purity of 99 wt % and 55 mol % (806 g) of 1-ethyl-3-methylimidazolium chloride (EMIC) with a purity of 99 wt % were charged (total of 100 mol % of AlCl3 and EMIC), the heater 2 was turned on, the evaporator 1 was heated to 63°C, and after confirming that it had become liquid, it was held for 1 hour. Next, in this state, the vacuum pump 4 was operated, and after the degree of vacuum in the evaporator 100 was held at 3 Pa, aluminum chloride was evaporated at 11.9 g per minute. After aluminum chloride was attached to the inner wall of the cooler 2, the vacuum pump 4 was stopped. The amount of metal impurities in the aluminum chloride deposited inside the tube of the cooler 3 was analyzed using an inductively coupled plasma (ICP) optical emission spectrometer (ICP-OES) (Agilent Technologies; detection limit for each element is 0.01-0.1 ppb), and the contents of iron, nickel, chromium, sodium, zinc, lead, potassium, and copper were all less than 1 ppm. In addition, the amount was quantified using a Karl Fischer moisture meter (Nitto Seiko Analytech; detection limit is 3 ppm), and the amount was 42 ppm.

[0039] [Example 2] 55 mol % (800 g) of aluminum chloride with a purity of 99 wt % and 45 mol % (720 g) of 1-ethyl-3-methylimidazolium chloride (EMIC) with a purity of 99 wt % were charged into the evaporator 100 shown in Fig. 1 (total of 100 mol % of AlCl3 and EMIC), the heater 2 was turned on, and the evaporator 1 was maintained at 76°C. In this state, the vacuum pump 4 was operated to create a vacuum of 8 Pa in the evaporator 100 and maintain it for 2 hours, evaporating aluminum chloride at 13.2 g per minute, and the aluminum chloride was attached to the inner wall of the cooler 3, and then the vacuum pump 4 was stopped. When the aluminum chloride deposited inside the tube of the cooler 3 was analyzed in the same manner as in Example 1, the moisture content was 65 ppm, and the amounts of metal impurities were both less than 1 ppm.

[0040] [Example 3] 46 mol % (700 g) of aluminum chloride with a purity of 99 wt % and 54 mol % (904 g) of 1-ethyl-3-methylimidazolium chloride (EMIC) with a purity of 99 wt % (total of 100 mol % for AlCl3 and EMIC) were charged into the evaporator 200 shown in Fig. 2, and the heater 2 was turned on to maintain the evaporator 1 at 32°C. In this state, nitrogen gas under standard conditions was blown in at 300 cm3 per minute from the gas blowing pipe 6. 3 Aluminum chloride was evaporated at 11.3 g per minute for 5 hours to deposit aluminum chloride on the inner wall of the cooler 3, after which the supply of nitrogen gas was stopped. When the aluminum chloride deposited inside the tube of the cooler 3 was analyzed in the same manner as in Example 1, the moisture content was 65 ppm, and the amounts of metal impurities were both less than 1 ppm.

[0041] [Example 4] 58 mol % (800 g) of aluminum chloride with a purity of 99 wt % and 42 mol % (637 g) of 1-ethyl-3-methylimidazolium chloride (EMIC) with a purity of 99 wt % (total of 100 mol % for AlCl3 and EMIC) were charged into the evaporator 300 shown in Fig. 3, and the heater 2 was turned on to maintain the evaporator 1 at 66°C. In this state, nitrogen gas under standard conditions was blown in at 200 cm3 per minute through the ceramic bottom filter 8 for blowing gas.3 Aluminum chloride was evaporated at 13.3 g per minute for 4 hours to deposit aluminum chloride on the inner wall of the cooler 3, after which the supply of nitrogen gas was stopped. When the aluminum chloride deposited inside the tube of the cooler 3 was analyzed in the same manner as in Example 1, the moisture content was 77 ppm, and the amounts of metal impurities were both less than 1 ppm.

[0042] [Example 5] Into the evaporator 400 shown in Fig. 4, 47 mol % (700 g) of aluminum chloride with a purity of 99 wt % and 53 mol % (868 g) of 1-ethyl-3-methylimidazolium chloride (EMIC) with a purity of 99 wt % (total of 100 mol % for AlCl3 and EMIC) were charged, and the heater 2 was turned on to maintain the evaporator 1 at 42°C. In this state, the vacuum pump 4 was operated to maintain the degree of vacuum in the evaporator 400 at 3 Pa, and then the vacuum pump 4 was stopped. In this state, nitrogen gas under standard conditions was blown from the gas blowing pipe 6 at 300 cm per minute. 3 The aluminum chloride was evaporated at 18.1 g per minute for 5 hours, and after the aluminum chloride was deposited on the inner wall of the cooler 3, the supply of nitrogen gas was stopped. When the aluminum chloride deposited inside the tube of the cooler 3 was analyzed in the same manner as in Example 1, the moisture content was 55 ppm, and the amounts of metal impurities were both less than 1 ppm.

[0043] [Example 6] 5, 50 mol % (700 g) of aluminum chloride with a purity of 99 wt % and 50 mol % (770 g) of 1-ethyl-3-methylimidazolium chloride (EMIC) with a purity of 99 wt % were charged (total of 100 mol % for AlCl3 and EMIC), the heater 2 was turned on, and the evaporator 1 was maintained at 63° C. In this state, the vacuum pump 4 was operated to maintain the degree of vacuum in the evaporator 500 at 3 Pa, and then the vacuum pump 4 was stopped. In this state, nitrogen gas under standard conditions was blown in at 300 cm per minute through the ceramic bottom filter 8 for blowing gas. 3Aluminum chloride was evaporated at 15.7 g per minute for 5 hours to deposit aluminum chloride on the inner wall of the cooler 3, after which the supply of nitrogen gas was stopped. When the aluminum chloride deposited inside the tube of the cooler 3 was analyzed in the same manner as in Example 1, the moisture content was 29 ppm, and the amounts of metal impurities were both less than 1 ppm.

[0044] [Comparative Example 1] 6, 67 mol % (1000 g) of aluminum chloride with a purity of 99 wt % and 33 mol % (542 g) of 1-ethyl-3-methylimidazolium chloride (EMIC) with a purity of 99 wt % were charged into the evaporator 600 shown in Fig. 6 (total of AlCl3 and EMIC: 100 mol %), the heater 2 was turned on, and the evaporator 1 was maintained at 120°C. In this state, nitrogen gas was supplied at 200 cm3 per minute. 3 The gas was supplied from the gas inlet pipe 9 for 2 hours at 1000 rpm and discharged from the gas outlet pipe 7. In Comparative Example 1, the evaporation rate of aluminum chloride was less than 0.1 g per minute, and it was difficult to cause the aluminum chloride in the gas phase to adhere and deposit inside the tube of the cooler 3. The aluminum chloride that had deposited inside the tube of the cooler 3 was barely recovered and analyzed in the same manner as in Example 1. As shown in Table 1, the amount of metal impurities was less than 1 ppm, but the amount of moisture was as high as 567 ppm.

[0045] [Comparative Example 2] Aluminum chloride was evaporated in the same manner as in Comparative Example 1, except that the composition of the evaporation raw materials was changed to 50 mol % (700 g) of aluminum chloride having a purity of 99 wt % and 50 mol % (770 g) of 1-ethyl-3-methylimidazolium chloride (EMIC) having a purity of 99 wt %. In Comparative Example 2, the evaporation rate of aluminum chloride was also less than 0.1 g per minute, and it was difficult to cause the aluminum chloride in the gas phase to adhere and deposit inside the tube of the cooler 3. The aluminum chloride deposited inside the tube of the cooler 3 was recovered and analyzed in the same manner as in Example 1. The amount of metal impurities was reduced to less than 1 ppm, but the amount of moisture was high at 454 ppm.

[0046] [Comparative Example 3] 1, 50 mol % (700 g) of aluminum chloride with a purity of 99 wt % and 50 mol % (770 g) of 1-ethyl-3-methylimidazolium chloride (EMIC) with a purity of 99 wt % were charged (total of 100 mol % of AlCl3 and EMIC), the heater 2 was turned on, the evaporator 1 was heated to 120° C., and after confirming that the liquid phase had been reached, the mixture was maintained for one hour. In this state, the vacuum pump 4 was operated to maintain the degree of vacuum in the evaporator 100 at 3 Pa, and aluminum chloride was evaporated at 12.9 g per minute, and the aluminum chloride was attached to the inner wall of the cooler 3, after which the vacuum pump 4 was stopped. When the aluminum chloride deposited inside the tube of the cooler 3 was analyzed in the same manner as in Example 1, the amount of metal impurities was reduced to less than 1 ppm, but the amount of moisture was high at 277 ppm.

[0047] [Comparative Example 4] 1, 50 mol % (700 g) of aluminum chloride with a purity of 99 wt % and 50 mol % (770 g) of 1-ethyl-3-methylimidazolium chloride (EMIC) with a purity of 99 wt % were charged (total of 100 mol % of AlCl3 and EMIC), the heater 2 was turned on, the evaporator 1 was heated to 60° C., and after confirming that the liquid phase had been reached, the mixture was maintained for one hour. In this state, the vacuum pump 4 was operated to maintain the degree of vacuum in the evaporator 100 at 20 Pa, and the aluminum chloride was evaporated and adhered to the inner wall of the cooler 3, after which the vacuum pump 4 was stopped. When the aluminum chloride deposited inside the tube of the cooler 3 was analyzed in the same manner as in Example 1, the amount of metal impurities was reduced to less than 1 ppm as shown in Table 1, and the amount of moisture was also low at 86 ppm. However, the amount of AlCl3 evaporated was 4.8 g per minute, less than half that of Examples 1 to 6.

[0048] Table 1 shows the production conditions and the evaluation results of aluminum chloride for Examples 1 to 6 and Comparative Examples 1 to 4. [Table 1] [Industrial Applicability]

[0049] The anhydrous aluminum chloride according to the present invention has an extremely high purity and is therefore useful in many industrial applications requiring high purity, including applications such as Al2O3 insulating films formed by chemical vapor deposition (CVD) in the manufacture of fuel cells, semiconductors, and integrated circuits (ICs), and by atomic layer epitaxy (ALE) for EL elements. [Explanation of symbols]

[0050] 100,200,300,400,500,600 Evaporation device 1 Evaporator 2 Heater 3 Cooler 4. Vacuum pump 5. Pressure gauge 6 Gas inlet pipe 7 Gas outlet pipe 8. Bottom filter for gas blowing 9 Gas inlet pipe

Claims

1. An evaporation device including at least an evaporator and a vacuum pump, 35 to 70 mol % of aluminum chloride; a step 1 of heating an evaporator containing a room-temperature molten salt composed of 65 to 30 mol % of an onium chloride selected from 1,3-dimethylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride (EMIC), 1-methyl-3-propylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-methyl-3-pentylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-heptyl-3-methylimidazolium chloride, and 1-methyl-3-octylimidazolium chloride (wherein the total of aluminum chloride and the onium chloride is 100 mol %) at a temperature of 30 to 80° C. and under a reduced pressure of 0.01 to 8 Pa to vaporize aluminum chloride from the room-temperature molten salt; and step 2 of cooling and solidifying the aluminum chloride vapor in the gas phase to recover aluminum chloride having a water content of 100 ppm or less.

2. The evaporation device further includes a gas inlet pipe for supplying a carrier gas, and a gas outlet pipe; 2. The method for producing anhydrous aluminum chloride according to claim 1, wherein during steps 1 and 2, a carrier gas is introduced into the room-temperature molten salt through the gas-injection pipe, and gas-liquid contact between the carrier gas and the room-temperature molten salt is carried out by bubbling.

3. An evaporation apparatus including at least an evaporator, a gas inlet pipe for supplying a carrier gas, and a gas outlet pipe, 35 to 70 mol % of aluminum chloride; a step 1 of heating an evaporator containing a room-temperature molten salt composed of 65 to 30 mol % of an onium chloride selected from 1,3-dimethylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride (EMIC), 1-methyl-3-propylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-methyl-3-pentylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-heptyl-3-methylimidazolium chloride, and 1-methyl-3-octylimidazolium chloride (wherein the total of aluminum chloride and the onium chloride is 100 mol %) at a temperature of 30 to 80° C. to vaporize aluminum chloride from the room-temperature molten salt; and a step 2 of cooling and solidifying the aluminum chloride vapor in the gas phase to recover aluminum chloride having a moisture content of 100 ppm or less. A method for producing anhydrous aluminum chloride, characterized in that during steps 1 and 2, a carrier gas is introduced into the room-temperature molten salt through the gas-injection pipe, and gas-liquid contact between the carrier gas and the room-temperature molten salt is carried out by bubbling.

4. An evaporation apparatus comprising at least an evaporator, a gas blowing bottom filter for supplying a carrier gas, and a gas outlet pipe, 35 to 70 mol % of aluminum chloride; a step 1 of heating an evaporator containing a room-temperature molten salt composed of 65 to 30 mol % of an onium chloride selected from 1,3-dimethylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride (EMIC), 1-methyl-3-propylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-methyl-3-pentylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-heptyl-3-methylimidazolium chloride, and 1-methyl-3-octylimidazolium chloride (wherein the total of aluminum chloride and the onium chloride is 100 mol %) at a temperature of 30 to 80° C. to vaporize aluminum chloride from the room-temperature molten salt; and a step 2 of cooling and solidifying the aluminum chloride vapor in the gas phase to recover aluminum chloride having a moisture content of 100 ppm or less. A method for producing anhydrous aluminum chloride, characterized in that during steps 1 and 2, a carrier gas is introduced into the room-temperature molten salt through the gas-blowing bottom filter, and gas-liquid contact between the carrier gas and the room-temperature molten salt is carried out by bubbling.

5. An evaporation apparatus comprising at least an evaporator, a vacuum pump, a gas blowing bottom filter for supplying a carrier gas, and a gas outlet pipe, 35 to 70 mol % of aluminum chloride; a step 1 of heating an evaporator containing a room-temperature molten salt composed of 65 to 30 mol % of an onium chloride selected from 1,3-dimethylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride (EMIC), 1-methyl-3-propylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-methyl-3-pentylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-heptyl-3-methylimidazolium chloride, and 1-methyl-3-octylimidazolium chloride (wherein the total of aluminum chloride and the onium chloride is 100 mol %) at a temperature of 30 to 80° C. and under a reduced pressure of 0.01 to 8 Pa to vaporize aluminum chloride from the room-temperature molten salt; and a step 2 of cooling and solidifying the aluminum chloride vapor in the gas phase to recover aluminum chloride having a moisture content of 100 ppm or less. A method for producing anhydrous aluminum chloride, characterized in that during steps 1 and 2, a carrier gas is introduced into the room-temperature molten salt through the gas-blowing bottom filter, and gas-liquid contact between the carrier gas and the room-temperature molten salt is carried out by bubbling.

6. 6. The method for producing anhydrous aluminum chloride according to claim 4 or 5, wherein the bottom filter for blowing gas is made of diffusion bricks or glass fiber.

7. The method for producing anhydrous aluminum chloride according to any one of claims 1 to 5, characterized in that the onium chloride is 1-ethyl-3-methylimidazolium chloride (EMIC).

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