Production method of aluminum using hydrate

Abstract

A production method of aluminum including: a step of synthesizing an aluminum compound from a mixture including a halogenated aluminum hydrate and a perfluoroalkylsulfonimide-type or perfluoroalkylsulfonamide-type ionic liquid represented by general formula (1); a step of dissolving the aluminum compound in a nitrile-based organic solvent to prepare an aluminum electrolyte; a step of adding at least one ligand selected from a phosphorus compound and an organic compound having an amide group to the aluminum electrolyte and dehydrating water molecules from a hydrate included in the aluminum electrolyte; and a step of electrodepositing aluminum on a cathode by allowing electricity to pass between an anode and the cathode in the aluminum electrolyte after the dehydrating step.

Claims

1. A production method of aluminum comprising: a step of synthesizing an aluminum compound derived from an aluminum perfluoroalkyl sulfonyl imide or an aluminum perfluoroalkyl sulfonyl amide from a mixture including a halogenated aluminum hydrate and a perfluoroalkylsulfonimide-type or perfluoroalkylsulfonamide-type ionic liquid represented by following general formula (1): wherein Rf.sup.1 and Rf.sup.2 are each independently CF.sub.3 or C.sub.4F.sub.9, and ##STR00004## M is H, alkali metal, quaternary ammonium or imidazolium; a step of dissolving the aluminum compound in a nitrile-based organic solvent to prepare an aluminum electrolyte; a step of adding at least one ligand selected from either a phosphorus compound or an organic compound having an amide group to the aluminum electrolyte wherein the at least one ligand dehydrates water molecules from a hydrate included in the aluminum electrolyte; and a step of electrodepositing aluminum on a cathode by allowing electricity to pass between an anode and the cathode in the aluminum electrolyte after the adding step.

2. The production method of aluminum according to claim 1, wherein the aluminum electrolyte with the at least one ligand added is stirred at 0 C. or higher and 100 C. or lower in the adding step.

3. The production method of aluminum according to claim 1, wherein constant potential electrolysis with an electrode potential with respect to aluminum used as a reference electrode of 6.0 V or more and less than 0 V or constant current electrolysis with a current density of 1 Acm.sup.2 or more and 10000 Acm.sup.2 or less is carried out in the electrodepositing step.

4. The production method of aluminum according to claim 1, wherein a temperature of an electrolytic bath is 20 C. or higher and 100 C. or lower in the electrodepositing step.

5. The production method of aluminum according to claim 1, wherein Rf.sup.1 and Rf.sup.2 in the general formula (1) are CF.sub.3.

6. The production method of aluminum according to claim 1, wherein the halogenated aluminum hydrate is aluminum (III) chloride hexahydrate.

7. The production method of aluminum according to claim 1, wherein the phosphorus compound is selected from the group consisting of phosphinic acid, a phosphine oxide, and tributyl phosphate.

8. The production method of aluminum according to claim 1, wherein the organic compound having an amide group is selected from the group consisting of N-phenylacetamide, dimethylformamide, and dimethylacetamide.

Description

DETAILED DESCRIPTION

(1) Hereinafter, embodiments of the present disclosure will be described. The present disclosure is not limited to the following embodiments and can be carried out in various aspects within a range not departing from the scope of the present disclosure.

(2) A production method of aluminum according to the present disclosure includes

(3) a step of synthesizing an aluminum compound of an aluminum perfluoroalkyl sulfonyl imide or an aluminum perfluoroalkyl sulfonyl amide from a mixture including a halogenated aluminum hydrate and a perfluoroalkylsulfonimide-type or perfluoroalkylsulfonamide-type ionic liquid represented by the following general formula (1):

(4) ##STR00002##

(5) wherein

(6) Rf.sup.1 and R.sup.2 are each independently CF.sub.3 or C.sub.4F.sub.9, and

(7) M is H, alkali metal, quaternary ammonium or imidazolium;

(8) a step of dissolving the aluminum compound in a nitrile-based organic solvent to prepare an aluminum electrolyte;

(9) a step of adding at least one ligand selected from a phosphorus compound and an organic compound having an amide group to the aluminum electrolyte and dehydrating water molecules from a hydrate included in the aluminum electrolyte; and

(10) a step of electrodepositing aluminum on a cathode by allowing electricity to pass between an anode and the cathode in the aluminum electrolyte after the dehydrating step.

(11) That is, in the production method of aluminum according to the present disclosure, a halogenated aluminum hydrate is used instead of anhydrous halogenated aluminum, the anhydrous halogenated aluminum being an undesirable raw material from a point of view of production costs, energy consumption, etc. Then, a certain aluminum compound is synthesized from the halogenated aluminum hydrate and a predetermined ionic liquid, and the aluminum electrolyte is prepared using an organic solvent capable of dissolving the aluminum compound. Consequently, aluminum is allowed to be electrodeposited at around room temperature by electrolytic reaction with an electrolyte prepared by using the halogenated aluminum hydrate, that is, an ionic liquid method, and therefore aluminum (hereinafter, also simply referred to as Al) can be produced with lower energy consumption and at a lower cost than before. In addition, water molecules (H.sub.2O ligand) of a hydrate included in the aluminum electrolyte such as a hydrate of the synthesized aluminum compound, an unreacted halogenated aluminum hydrate remaining in the aluminum electrolyte, etc. are replaced by a predetermined ligand by adding the predetermined ligand to the aluminum electrolyte. Consequently, water molecules which may hinder electrodeposition are removed from the hydrate included in the aluminum electrolyte, and therefore aluminum is allowed to be efficiently electrodeposited.

(12) <Synthesis of Aluminum Compound>

(13) First, synthesis of the aluminum compound carried out in the production method of aluminum according to the present disclosure is described. The aluminum compound (hereinafter, also simply referred to as the Al compound) derived from an aluminum perfluoroalkyl sulfonyl imide or an aluminum perfluoroalkyl sulfonyl amide is synthesized through mixing the predetermined ionic liquid represented by formula (1) and the halogenated aluminum hydrate, and heating the resulting mixture to vaporize moisture and hydrogen chloride, which are byproducts originated from the halogenated aluminum. A mixing ratio of the ionic liquid and the halogenated aluminum hydrate is not particularly limited, and a molar ratio of ionic liquid:halogenated aluminum hydrate is preferably 0.1:1 to 10:1 and more preferably 0.5:1 to 5:1. In addition, a heating temperature of the mixture is also not particularly limited, and the heating temperature is preferably 80 C. or higher and 200 C. or lower and more preferably 100 C. or higher and 150 C. or lower. In addition, distillation may be carried out as necessary to further remove impurities from the heated mixture. A desired Al compound is synthesized through these steps. Such Al compounds are aluminum perfluoroalkyl sulfonyl imides (amides) such as aluminum bis(trifluoromethanesulfonyl)imide and their hydrates, for example.

(14) (Ionic Liquid)

(15) In the present disclosure, an ionic liquid is a general term for liquid ionic compounds (salts) composed of a combination of a cationic species and an anionic species and intends to represent a compound forming a liquid phase at a relatively low temperature not more than 100 C. Such an ionic liquid has quite a low vapor pressure and can be used also in a vacuum like in a SEM in some cases. It is also possible to allow the ionic liquid to exhibit hydrophobicity by appropriately selecting the anionic species.

(16) As the ionic liquid, a compound capable of dissolving in a nitrile-based organic solvent described later and capable of being used as the aluminum electrolyte is selected. Specifically, a perfluoroalkylsulfonimide-type or perfluoroalkylsulfonamide-type ionic liquid represented by the following general formula (1):

(17) ##STR00003##

(18) wherein

(19) Rf.sup.1 and Rf.sup.2 are each independently CF.sub.3 or C.sub.4F.sub.9,

(20) M is H, alkali metal, quaternary ammonium or imidazolium is used. Examples of such an ionic liquid include an ionic liquid based on bis(trifluoromethanesulfonyl)imide in which Rf.sup.1 and Rf.sup.2 are each CF.sub.3 in general formula (1), an ionic liquid based on bis(nonafluorobutanesulfonyl)imide in which Rf.sup.1 and Rf.sup.2 are each C.sub.4F.sub.9, and an ionic liquid based on nonafluoro-N-[(trifluoromethane)sulfonyl]butanesulfonyl amide in which Rf.sup.1 is CF.sub.3 and Rf.sup.2 is C.sub.4F.sub.9. Among these ionic liquids, an ionic liquid in which Rf.sup.1 and Rf.sup.2 are each CF.sub.3 in general formula (1), that is, an ionic liquid including an anion of bis(trifluoromethanesulfonyl)imide (hereinafter, also referred to as TFSI) is preferable, and an ionic liquid in which M as a cation is H, K (potassium), Li (lithium) or Na (sodium), that is, an ionic liquid of HTFSI, KTFSI, LiTFSI or NaTFSI is particularly preferable. For the ionic liquid used in the present disclosure, imide means a case where Rf.sup.1 and Rf.sup.2 have the same structure, and amide means a case where Rf.sup.1 and Rf.sup.2 have different structures with each other.

(21) (Halogenated Aluminum Hydrate)

(22) As a halogenated aluminum hydrate, for example, aluminum (III) fluoride hexahydrate (AlF.sub.3.6H.sub.2O), aluminum (III) chloride hexahydrate (AlCl.sub.3.6H.sub.2O), aluminum (III) bromide hexahydrate (AlBr.sub.3.6H.sub.2O), aluminum (III) iodide hexahydrate (All.sub.3.6H.sub.2O), etc. can be used. An Al compound synthesized from a mixture of such a halogenated aluminum hydrate and the perfluoroalkyl sulfon imide(amide)-type ionic liquid as described above may be an Al source in an aluminum electrolyte described later. Aluminum (III) chloride hexahydrate is preferable among the halogenated aluminum hydrates from a point of being easily available at a low cost.

(23) <Preparation of Aluminum Electrolyte>

(24) After synthesizing the Al compound, the obtained Al compound is dissolved in a nitrile-based organic solvent to prepare an aluminum electrolyte (hereinafter, simply referred as the electrolyte). An amount of the Al compound included in the electrolyte is not particularly limited as long as the Al compound can be sufficiently dissolved in the nitrile-based organic solvent and a sufficient amount of Al can be deposited by electrodeposition described later, and the amount of the Al compound is preferably 0.1 g or more and 100 g or less and more preferably 0.5 g or more and 50 g or less with respect to 100 ml of the electrolyte. In addition, while the Al compound can be dissolved by stirring at ordinary temperature, heating treatment at 40 C. to 80 C., for example, may be carried out to rapidly and surely dissolve the Al compound.

(25) (Organic Solvent)

(26) A nitrile-based compound is used as the organic solvent from points that the Al compound synthesized from the halogenated aluminum hydrate and the above certain perfluoroalkyl sulfon imide(amide)-type ionic liquid can be dissolved in a nitrile-based compound and that a nitrile-based compound is available as a solution of the electrolyte. As such a nitrile-based compound, for example, acetonitrile, acrylonitrile, and benzonitrile are preferable, and acetonitrile is particularly preferable.

(27) <Dehydration of Water Molecules>

(28) After preparing the electrolyte, at least one ligand selected from a phosphorus compound and an organic compound having an amide group is added to the obtained electrolyte to dehydrate water molecules from the hydrate included in the electrolyte. An amount of the ligand added is not particularly limited as long as the ligand is allowed to replace water molecules of the hydrate included in the electrolyte and the ligand do not affect electrodeposition described later in the amount added, and the amount added is preferably 0.01 mol/L or more and 10 mol/L or less and more preferably 0.05 mol/L or more and 5 mol/L or less with respect to 100 ml of the electrolyte. In addition, the ligand to be added may be of one ligand or of two or more ligands.

(29) When water molecules are dehydrated from the hydrate included in the electrolyte, it is preferable that the aluminum electrolyte with at least one ligand added be stirred at 0 C. or higher and 100 C. or lower. In addition, in order to more efficiently conduct subsequent electrodeposition by conducting this dehydration step under a more appropriate condition, a temperature of the aluminum electrolyte including the ligands is more preferably 20 C. or higher and 90 C. or lower and still more preferably 30 C. or higher and 70 C. or lower.

(30) (Ligands)

(31) Ligands are selected from a phosphorus compound and an organic compound having an amide group as a compound capable of replacing water molecules originated from the hydrate included in the electrolyte and dissolving in the nitrile-based organic solvent. Since bonding strength to Al of these compounds is stronger than that of water molecules, these compounds are capable of substituting water molecules existing around Al to form coordinate bonds so as to surround Al. Water molecules of the hydrate included in the electrolyte such as the hydrate of the synthesized Al compound and the unreacted halogenated aluminum hydrate remaining in the electrolyte, for example, are substituted. That is, ligands serve as a dehydrating agent to remove water molecules (H.sub.2O ligands) surrounding Al.

(32) Phosphorus compound is a general term for compounds including a phosphorus atom (P), and examples of the phosphorus compound include a phosphoric acid ester, phosphonic acid, phosphinic acid, a phosphinic acid ester, and a phosphine oxide. The phosphoric acid ester may be any of a monoester, a diester, and a triester, and a phosphoric acid triester is preferable. Examples of the phosphoric acid ester include alkyl phosphates such as trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, trioctyl phosphate, (alkyl)aryl phosphates such as triphenyl phosphate, tricresyl phosphate, and trixylenyl phosphate, tributoxyethyl phosphate, and tributyl phosphate is particularly preferable. The phosphonic acid, phosphinic acid, phosphinic acid ester, and a phosphine oxide may be a derivative with at least one H atom bonding to a phosphorus atom having been substituted with an organic group such as an alkyl group, an aryl group, an alkylaryl group or an alkoxy group, for example. Among them, it is preferable that the phosphorus compound be selected from the group consisting of phosphonic acid, phosphinic acid, a phosphine oxide, and tributyl phosphate, and it is particularly preferable that the phosphorus compound be selected from the group consisting of phosphinic acid, a phosphine oxide, and tributyl phosphate.

(33) Examples of the organic compound having an amide group include an aliphatic amide and an aromatic amide. These amides may be any of a primary amide, a secondary amide, and a tertiary amide, and a secondary amide or a tertiary amide is preferable. As the primary amide, formamide, acetamide, propionamide, butyramide, benzamide, etc. are exemplified, for example. As the secondary amide, N-methylformamide, N-ethylformamide, N-methylacetamide, N-ethylacetamide, N-phenylformamide, N-phenylacetamide, etc. are exemplified, for example. As the tertiary amide, dimethylformamide, diethylformamide, dimethylacetamide, diethylacetamide, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, etc. are exemplified, for example. Among them, it is preferable that the organic compound having an amide group be selected from the group consisting of N-phenylacetamide, dimethylformamide, and dimethylacetamide, and it is particularly preferable that the organic compound having an amide group be selected from dimethylformamide and dimethylacetamide.

(34) <Electrodeposition of Aluminum>

(35) After preparing the electrolyte, electricity is allowed to pass between an anode and a cathode in the electrolyte, that is, aluminum is electrodeposited on a cathode by electrolysis. This electrolysis allows Al to be electrodeposited on a surface of the cathode by preparing an electrolytic tank containing an electrolyte, arranging a cathode and an anode to face to each other in the electrolyte, applying a voltage or a current or both of a voltage and a current between both electrodes to allow electricity to pass. On electrodeposition, moisture originated from the halogenated aluminum hydrate may react with electrodeposit to cause electrodeposition of aluminum oxide or hydroxide simultaneously with electrodeposition of Al. However, an amount of these byproducts to be electrodeposited is quite small, and Al is mainly electrodeposited.

(36) (Electrodeposition Conditions)

(37) An electrodeposition temperature, that is, a temperature of the electrolytic bath during electrodeposition is preferably 20 C. or higher and 100 C. or lower, more preferably 20 C. or higher and 80 C. or lower, and still more preferably 30 C. or higher and 70 C. or lower. The lower limit of 20 C. is set as a temperature around room temperature. On the other hand, when the electrodeposition temperature exceeds 100 C., volatilization of the nitrile-based organic solvent in the electrolyte easily occurs and composition of the electrolyte is prone to become unstable. As a result, if electrodeposition failure occurs, Al becomes difficult to be electrodeposited.

(38) Electrodeposition is preferably carried out by constant potential electrolysis with an electrode potential with respect to aluminum used as a reference electrode of 6.0 V or more and less than 0 V or by constant current electrolysis with a current density of 1 Acm.sup.2 or more and 10000 Acm.sup.2 or less. Constant potential electrolysis is a method for carrying out electrolysis while keeping an electrode potential of one of the anode and the cathode immersed in the electrolyte constant with respect to a reference electrode. In constant potential electrolysis, the electrode potential is preferably set at an electrode potential of 4.0 V or more and less than 0 V and more preferably 2.0 V or more and 0.7 V or less as a potential range lower than 0 V vs. Al/Al(III) where a reduction current is observed with respect to an Al line serving as the reference electrode. An electrode potential of less than 6.0 V results in reduced electrodeposition efficiency because an electrodeposition speed at the electrode potential of less than 6.0 V is too slow, and consequently Al becomes difficult to be electrodeposited. In addition, constant current electrolysis is a method for carrying out electrolysis while keeping a value of current constant. A current density in the constant current electrolysis is preferably 10 Acm.sup.2 or more and 10000 Acm.sup.2 or less, more preferably 20 Acm.sup.2 or more and 1000 Acm.sup.2 or less, still more preferably 30 Acm.sup.2 or more and 500 Acm.sup.2 or less, and particularly preferably 50 Acm.sup.2 or more and 300 Acm.sup.2 or less. A current density of less than 1 Acm.sup.2 results in reduced electrodeposition efficiency because an electrodeposition speed at the current density of less than 1 Acm.sup.2 is too slow, and consequently Al becomes difficult to be electrodeposited. On the other hand, when the current density exceeds 10000 Acm.sup.2, decomposition in electrolytic bath easily occurs, and consequently Al becomes difficult to be electrodeposited.

(39) (Cathode)

(40) In the production method of aluminum according to the present disclosure, the cathode is not particularly limited. For example, a cathode composed of a metal material such as platinum, gold, and copper may be used to deposit Al on the metal material and the deposited Al may be collected. Alternatively, a cathode composed of a metal material having a passive coating (oxide coating) such as titanium, nickel, and a stainless steel may be used to deposit Al on the passive coating, and the deposited Al may be successively peeled off and collected by utilizing low adhesiveness between the passive coating and Al. In addition, material of the cathode is not limited to metal materials, and a cathode composed of carbon, a plastic material given electrical conductivity, etc. may be used.

(41) (Anode)

(42) In addition, the anode is also not particularly limited, and an aluminum source to be consumed in the electrolyte during electrodeposition can be replenished from the anode with use of soluble aluminum. As an insoluble anode, an electrode of a pure metal such as platinum and titanium, or a titanium electrode coated with an insoluble metal such as platinum, iridium oxide, ruthenium oxide, lead dioxide, etc. can be used.

EXAMPLES

(43) Next, the present disclosure will be described in more detail based on Examples, but the present disclosure is not limited to the Examples.

Examples 1 to 40, Comparative Examples 1 to 8

(44) Aluminum was produced according to the following procedures.

(45) <Synthesis of Al Compound>

(46) Ionic liquids and halogenated aluminum compounds shown in Table 1 were used to be mixed so as to achieve a molar ratio of ionic liquid:halogenated aluminum compound=3:1. Then, the obtained mixtures were heated at 120 C. to prepare aluminum compounds to be desired Al sources. Synthesis reaction formulae of Example 1 are shown as formulae (2) and (3) as an example.
AlCl.sub.3.6H.sub.2O+3HTFSI.fwdarw.Al(TFSI).sub.3+3HCl+6H.sub.2O(2)
AlCl.sub.3.6H.sub.2O+3HTFSI.fwdarw.Al(TFSI).sub.3.6(H.sub.2O)+3HCl(3)

(47) As to ionic liquids used in Comparative Examples 2 to 4 in Table 1, EMIC, EMIFSI, and LiBETI mean 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, and lithium bis(pentafluoroethanesulfonyl)imide, respectively.

(48) <Preparation of Electrolyte>

(49) An electrolyte was prepared by dissolving 2 g of each of the synthesized Al compounds in 20 ml of a corresponding nitrile-based organic solvent shown in Table 1.

(50) <Dehydration of Water Molecules>

(51) A predetermined amount of each ligand shown in Table 1 was added dropwise to the electrolyte and the electrolyte was kept for two days or longer while being heated and stirred at a temperature (dehydration temperature) shown in Table 1 using a hot stirrer to dehydrate water molecules.

(52) <Electrodeposition of Al>

(53) Constant potential electrolysis and constant current electrolysis were conducted under electrodeposition conditions shown in Table 1 using a Cu plate as the cathode and glassy carbon as the anode. The cathode was washed with water and dried after the electrolysis, and Al was allowed to be electrodeposited on the cathode.

(54) The following evaluations were conducted on the electrodeposit obtained on the cathode in each of the Examples and Comparative Examples. Electrodeposition conditions and evaluation results are shown in Table 1.

(55) TABLE-US-00001 TABLE 1 Halogenated Electrode Current tonic Aluminum Organic Dehydration Potential Density Electrodeposition Electrodeposition Total Liquid Compound Solvent Ligand Temperature V vs. Al/Al(III) mA/cm.sup.2 Temperature C. Appearance SEM-EDS XRD Efficiency Evaluation Examples 1 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.7 50 Excellent Excellent Excellent Good Excellent 2 KTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.7 50 Excellent Excellent Excellent Good Excellent 3 LiTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.7 50 Excellent Excellent Excellent Good Excellent 4 NaTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.7 50 Excellent Excellent Excellent Good Excellent 5 HTFSl AlF.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.7 50 Good Good Good Good Good 6 HTFSl AlBr.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.7 50 Good Good Good Good Good 7 HTFSl All.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.7 50 Fair Good Good Good Good 8 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.7 50 Good Good Good Good Good 9 HTFSl AlCl.sub.36H.sub.2O Benzonitrile Tributyl Phosphate 50 0.7 50 Good Good Good Good Good 10 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 6 50 Fair Good Fair Good Fair 11 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 4 50 Fair Good Good Good Good 12 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 2 50 Good Good Excellent Good Very Good 13 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.4 50 Fair Good Good Good Good 14 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 1 50 Fair Good Fair Good Fair 15 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 10 50 Fair Good Good Good Good 16 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 30 50 Good Good Good Good Good 17 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 50 50 Excellent Good Excellent Good Very Good 18 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 100 50 Excellent Good Excellent Good Very Good 19 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 300 50 Excellent Good Excellent Good Very Good 20 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 500 50 Good Good Good Good Good 21 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 1000 50 Fair Good Good Good Good 22 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 10000 50 Fair Fair Fair Good Fair 23 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.7 20 Good Good Good Good Good 24 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.7 30 Excellent Good Good Good Very Good 25 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.7 70 Excellent Good Good Good Very Good 26 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.7 80 Good Good Good Good Good 27 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.7 100 Fair Fair Fair Good Fair 28 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Phosphonic Acid 50 0.7 50 Excellent Good Excellent Good Very Good 29 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Phosphonic Acid 50 0.7 50 Excellent Excellent Excellent Good Excellent 30 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Phosphonic Oxide 50 0.7 50 Excellent Excellent Excellent Good Excellent 31 HTFSl AlCl.sub.36H.sub.2O Acetonitrile N-phenyl Acetamide 50 0.7 50 Excellent Good Excellent Good Very Good 32 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Dimethylformamide 50 0.7 50 Excellent Excellent Excellent Good Excellent 33 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Dimethylacetamide 50 0.7 50 Excellent Excellent Excellent Good Excellent 34 HTFSl AlCl.sub.36H.sub.3O Acetonitrile Tributyl Phosphate 0 0.7 50 Fair Excellent Excellent Good Good 35 HTFSl AlCl.sub.36H.sub.3O Acetonitrile Tributyl Phosphate 20 0.7 50 Good Excellent Excellent Good Very Good 36 HTFSl AlCl.sub.36H.sub.4O Acetonitrile Tributyl Phosphate 30 0.7 50 Excellent Excellent Excellent Good Excellent 37 HTFSl AlCl.sub.36H.sub.5O Acetonitrile Tributyl Phosphate 70 0.7 50 Excellent Excellent Excellent Good Excellent 38 HTFSl AlCl.sub.36H.sub.6O Acetonitrile Tributyl Phosphate 80 0.7 50 Good Excellent Excellent Good Very Good 39 HTFSl AlCl.sub.36H.sub.7O Acetonitrile Tributyl Phosphate 90 0.7 50 Good Excellent Excellent Good Very Good 40 HTFSl AlCl.sub.36H.sub.3O Acetonitrile Tributyl Phosphate 100 0.7 50 Fair Excellent Excellent Good Good Comparative 1 HTFSl AlCl.sub.36H.sub.2O Acetonitrile 50 0.7 50 Good Good Good Poor Poor Examples 2 EMlC AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.7 50 Poor Poor Poor Poor Poor 3 EMlFSl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.7 50 Poor Poor Poor Poor Poor 4 LiBETl AlCl.sub.36H.sub.2O Acetonitrile Tributyl Phosphate 50 0.7 50 Poor Poor Poor Poor Poor 5 HTFSl Al.sub.2O.sub.3 Acetonitrile Tributyl Phosphate 50 0.7 50 Poor Poor Poor Poor Poor 6 HTFSl AlCl.sub.36H.sub.2O Ethanol Tributyl Phosphate 50 0.7 50 Poor Poor Poor Poor Poor 7 HTFSl AlCl.sub.36H.sub.2O Acetone Tributyl Phosphate 50 0.7 50 Poor Poor Poor Poor Poor 8 HTFSl AlCl.sub.36H.sub.2O Acetonitrile Pyridine 50 0.7 50 Poor Poor Poor Poor Poor

(56) <Appearance Observation>

(57) Electrodeposit on the cathode was visually confirmed, and a case where Al was uniformly electrodeposited without electrodeposition unevenness was rated excellent, a case where electrodeposit could be visually confirmed while electrodeposition unevenness was observed was rated good, a case where current or voltage could be confirmed at the time of electrolysis while electrodeposit could not visually observed was rated fair, and a case where neither current nor voltage was confirmed at the time of electrolysis and electrodeposition of Al could not be carried out was rated poor. That is, when the evaluation results were fair or better, electrodeposition of Al was evaluated as being enabled.

(58) <SEM-EDS>

(59) In order to analyze the obtained electrodeposit in more detail, by using a scanning electron microscope (SEM) (manufactured by JEOL Ltd., trade name: JSM-6010PLUS) and an energy dispersive X-ray spectrometer (EDS) built in the SEM, SEM-EDS analyses were conducted. A case where Al was remarkably detected was rated excellent, a case where Al was detected was rated good, a case where Al was slightly detected was rated fair, and a case where Al was not detected was rated poor.

(60) <XRD>

(61) In order to analyze the obtained electrodeposit in more detail, by using an X-ray diffractometer (manufactured by BRUKER, trade name: D2 PHASER), X-ray diffraction (XRD) was conducted. A case where strong peaks of Al were confirmed was rated excellent, a case where peaks of Al were confirmed was rated good, a case where weak peaks of Al were confirmed was rated fair, and a case where peaks of Al were not confirmed was rated poor.

(62) <Electrodeposition Efficiency>

(63) A weight (an amount collected) of the obtained electrodeposit was measured, and electrodeposition efficiency (collection rate) was calculated from the percentage of the amount collected with respect to a theoretical yield. The theoretical yield was calculated by the following equation (4) on the basis of Faraday's law. A case where the collection rate was 50% or more was rated good as having high electrodeposition efficiency, and a case where the collection rate was less than 50% was rated poor as having low electrodeposition efficiency.
Theoretical yield=(current densityfilm forming areafilm forming periodatomic weight of Al)/(valence of Al ionFaraday constant)(4) Atomic weight of Al=26.98, Valence of ion=3, Faraday constant=96500 [C.Math.mol.sup.1]

(64) <Total Evaluation>

(65) A case where electrodeposition efficiency was good, and all items among of the other three items of appearance observation, SEM-EDS, and XRD were excellent was rated excellent, a case where one or two evaluation items were excellent and the rest of the items were good was rated very good, a case where one evaluation item was fair and the rest of the items were good or excellent, or a case where all items were good was rated good, a case where two or more evaluation item were fair and the rest of the items were good or fair was rated fair, and a case where one or more evaluation items were poor was rated poor.

(66) In Examples 1 to 40, since the ionic liquids, halogenated aluminum compounds, and organic solvents were within the range defined in the present disclosure, Al could be produced through electrodeposition. That is, in Examples 1 to 40, aluminum could be electrodeposited from the halogenated aluminum hydrate instead of anhydrous halogenated aluminum, which is an undesirable raw material from a point of view of production costs, energy consumption, etc., by the ionic liquid method respectively. As a result, aluminum could be produced with lower energy consumption and at a lower cost than before. In addition, in any of Examples 1 to 40, the collection rate of aluminum as electrodeposit was high, and aluminum could be efficiently electrodeposited. Further, in Examples 1 to 4, 12, 17 to 19, 24, 25, 28 to 33, and 35 to 39, as the total evaluations were very good or higher, aluminum could be electrodeposited more efficiently as a whole, and especially in Examples 1 to 4, 29, 30, 32, 33, 36, and 37 with the total evaluations being excellent, aluminum could be electrodeposited still more efficiently.

(67) On the other hand, since ligands were not used in Comparative Example 1, while electrodeposition of Al could be confirmed, electrodeposition efficiency was inferior to those in Examples. Since the ionic liquids were not appropriate in Comparative Examples 2 to 4, no halogenated aluminum hydrate was used in Comparative Example 5, the organic solvents were not appropriate in Comparative Examples 6 and 7, and the ligands were not appropriate in Comparative Example 8, desired electrolytes could not be prepared. As a result, electrodeposition of Al could not be carried out and Al was not produced.