Method and apparatus for producing base oil

Abstract

Provided is a method for producing a base oil, the method comprising a step for regenerating a waste oil in a simple manner.　Specifically, this method for producing a base oil comprises: an extraction step in which an extractant containing an oil-insoluble deep eutectic solvent is mixed with a waste oil to extract at least one substance selected from among a dissolved substance and a dispersed substance; and a waste oil-treated oil addition step in which the waste oil-treated oil from the extraction step is added to a base oil production step.

Description

Method for producing base oil and apparatus for producing base oil

[0001] This invention relates to a method for producing base oil and an apparatus for producing base oil.

[0002] Generally, waste oil contains various substances in addition to the base oil. For example, after long-term use, it may contain degradation products or additives to improve various performance aspects, but these substances need to be extracted when recycling waste oil. In particular, in recent years, efforts to recycle waste oil have been promoted from the perspective of effective resource utilization and reduction of environmental burden, and research is progressing on technologies to regenerate and effectively utilize waste oil by extracting substances such as degradation products and additives from it. For example, as a method for recycling waste oil, Patent Document 1 discloses a waste oil recycling treatment method that includes a first step of adding an unsaturated aqueous solution of an ammonium sulfate compound and acids to waste oil and mixing them, and a second step of separating and recovering the oil from the resulting mixture.

[0003] Japanese Patent Publication No. 2016-53125

[0004] However, when treating with an aluminum sulfate aqueous solution, as described in Patent Document 1, further processing steps are required to remove residual aluminum from the oil, and measures are needed to prevent corrosion of manufacturing equipment by aluminum sulfate, resulting in considerable effort and cost. Thus, there is still room for improvement in waste oil recycling methods, and in order to promote waste oil recycling, where waste oil is recycled and reused as a raw material for base oil, there is a need for a simpler method to recycle waste oil and use it in base oil production.

[0005] Therefore, the object of the present invention is to provide a method for producing a base oil that includes a step of recycling waste oil in a simple manner.

[0006] The present invention provides the following [1] to [2]: [1] A method for producing a base oil, comprising: an extraction step of mixing waste oil with an extractant containing a non-oil-soluble deep eutectic solvent to extract one or more substances selected from the dissolved matter and dispersion; and a waste oil treatment step of adding the waste oil treated after the extraction step to a base oil production step. [2] A base oil production apparatus comprising: an extraction facility for mixing waste oil with an extractant containing a non-oil-soluble deep eutectic solvent to extract one or more substances selected from the dissolved matter and dispersion; a base oil production facility; and an additive facility for adding the waste oil treated after the extraction operation by the extraction facility to the base oil production facility.

[0007] According to the present invention, it is possible to provide a method for producing a base oil that includes a step of recycling waste oil in a simple manner.

[0008] This is the infrared absorption (IR) spectrum of sample oil 1 before the extraction test. This is the infrared absorption (IR) spectrum of sample oil after the extraction test of Comparative Example 1. This is the infrared absorption (IR) spectrum of sample oil after the extraction test of Example 9. This is the infrared absorption (IR) spectrum of sample oil 2 before the extraction test. This is the infrared absorption (IR) spectrum of sample oil after the extraction test of Comparative Example 4. This is the infrared absorption (IR) spectrum of sample oil after the extraction test of Example 14. This is the infrared absorption (IR) spectrum of sample oil 3 before the extraction test. This is the infrared absorption (IR) spectrum of sample oil after the extraction test of Comparative Example 5. This is the infrared absorption (IR) spectrum of sample oil after the extraction test of Example 20. This is the infrared absorption (IR) spectrum of sample oil 7 before the extraction test. This is the infrared absorption (IR) spectrum of sample oil after the extraction test of Comparative Example 13. This is the infrared absorption (IR) spectrum of sample oil after the extraction test of Example 37. This is the infrared absorption (IR) spectrum of sample oil 8 before the extraction test. This is the infrared absorption (IR) spectrum of the sample oil after the extraction test of Comparative Example 15. This is the infrared absorption (IR) spectrum of the sample oil after the extraction test of Example 42. This is a flow chart showing a preferred embodiment of the method for producing the base oil of this embodiment. This is a flow chart showing a preferred embodiment of the apparatus for producing the base oil of this embodiment.

[0009] The upper and lower limits of the numerical ranges described herein can be combined in any way. For example, if the numerical ranges "A to B" and "C to D" are described, the numerical ranges "A to D" and "C to B" are also included within the scope of the present invention. Furthermore, unless otherwise specified, the numerical ranges "lower limit to upper limit" described herein mean greater than or equal to the lower limit and less than or equal to the upper limit. In addition, in this specification, the numerical values ​​in the examples are numerical values ​​that can be used as upper or lower limits.

[0010] In this embodiment, "new oil" refers to a lubricating oil composition that has not deteriorated before use, while "waste oil" refers to a lubricating oil composition that has deteriorated due to long-term storage or other reasons, even if it has not yet been used, or a used lubricating oil composition.

[0011] The inventors diligently studied to solve the above problems. As a result, they conceived the idea of ​​using a deep eutectic solvent as an extractant. However, in the course of various studies based on this idea, the inventors discovered that there are deep eutectic solvents that are not suitable as extractants. Therefore, the inventors further diligently studied and found that if the deep eutectic solvent is a mixed product of one or more nonionic hydrogen bond donors and one or more nonionic hydrogen bond acceptors, then one or more substances selected from dissolved and dispersed substances in waste oil can be extracted by a simple method of mixing and stirring at relatively low temperature and atmospheric pressure. After further studies, the inventors completed the present invention. The components contained in the extractant used in the base oil production method of this embodiment will be described in detail below.

[0012] [Description of the Extractant] In the method for producing the base oil of this embodiment, the extractant contains a deep eutectic solvent which is a mixed product of one or more nonionic hydrogen bond donors selected from nonionic hydrogen bond acceptors.

[0013] <Deep Eutectic Solvent> A deep eutectic solvent is a mixed product obtained by mixing a hydrogen bond donor and a hydrogen bond acceptor. The melting point of the deep eutectic solvent is lower than the melting points of the hydrogen bond donor and hydrogen bond acceptor that constitute the deep eutectic solvent due to eutectic melting point depression. The melting point of the deep eutectic solvent only needs to be lower than the melting points of the hydrogen bond donor and hydrogen bond acceptor that constitute the deep eutectic solvent. From the viewpoint of handling as an extractant, it is preferably liquid at 100°C, more preferably liquid at 60°C, and even more preferably liquid at or near room temperature. In this specification, room temperature means 25°C, and near room temperature means 25±5°C. In this embodiment, at least one (preferably both) of the melting point of the nonionic hydrogen bond donor and the nonionic hydrogen bond acceptor that constitute the deep eutectic solvent is preferably above 40°C, more preferably above 50°C, even more preferably above 80°C, and even more preferably above 100°C, from the viewpoint of improving the evaporation characteristics of the deep eutectic solvent. While there are no particular upper limits to these melting points, from the viewpoint of ease of forming the deep eutectic solvent, they are preferably 350°C or lower, more preferably 300°C or lower, even more preferably 250°C or lower, and even more preferably 200°C or lower. The deep eutectic solvent may be used alone or in combination of two or more types.

[0014] Here, the deep eutectic solvent contained in the extractant of this embodiment is characterized in that it is a mixed product of one or more nonionic hydrogen bond donors and one or more nonionic hydrogen bond acceptors. That is, both the hydrogen bond donors and hydrogen bond acceptors are nonionic substances. Because the deep eutectic solvent is a mixed product of one or more nonionic hydrogen bond donors and one or more nonionic hydrogen bond acceptors, it can be easily separated from oil, and thus dissolved substances and dispersions in waste oil can be extracted by a simple method. Furthermore, from the viewpoint of improving the separation of the deep eutectic solvent from oil, it is preferable that the deep eutectic solvent contained in the extractant of this embodiment is non-oil soluble. In this embodiment, the deep eutectic solvent is "non-oil soluble" if the HSP value D of the deep eutectic solvent, as described later, is, for example, 17 MPa０．５ This means that the HSP value D is 18 MPa. ０．５ It may be greater than or equal to 19 MPa ０．５ It may be greater than or equal to 20 MPa ０．５ That's fine too.

[0015] In this embodiment, the nonionic hydrogen bond donor has a proton dissociation energy of preferably -400 kcal / mol or higher, more preferably -390 kcal / mol or higher, and even more preferably -385 kcal / mol or higher, from the viewpoint of facilitating the donation of hydrogen for the formation of a deep eutectic solvent and thus facilitating the generation of a deep eutectic solvent. The proton dissociation energy is typically -320 kcal / mol or lower. Furthermore, in this embodiment, the nonionic hydrogen bond acceptor has a proton affinity energy of preferably -180 kcal / mol or lower, more preferably -190 kcal / mol or lower, and even more preferably -195 kcal / mol or lower, from the viewpoint of facilitating the acceptance of hydrogen for the formation of a deep eutectic solvent and thus facilitating the generation of a deep eutectic solvent. The proton affinity energy is typically -280 kcal / mol or higher.

[0016] In this specification, "proton dissociation energy" means the energy required for a proton to dissociate from a hydrogen bond donor, and is the value calculated by the following equation (1): (Proton dissociation energy) = E(D - H ＋ )-{E(D-)+E(H ＋ )}...(1) The meaning of the symbols in the above formula (1) is as follows: ・E(D-H ＋ ): Total energy value after structural optimization of hydrogen bond donor: E(D-) + E(H ＋ ): The sum of the total energies of the proton and the other parts when the hydrogen bond donor is divided into these two parts. Note that D represents the hydrogen bond donor with the proton removed, and H represents the hydrogen atom.

[0017] Also, in this specification, the "proton affinity energy" means the energy required for a proton to bind to a hydrogen bond acceptor, and is a value calculated by the following formula (2). (Proton affinity energy) = E(A-H ＋ ) - {E(A) + E(H ＋ )}... (2) The meanings of the symbols in the above formula (2) are as follows. ・E(A-H ＋ ): The total energy value when a proton is added to a hydrogen bond acceptor and structural optimization is performed. ・E(A) + E(H ＋ ): The sum of the total energies of each part when a proton is added to a hydrogen bond acceptor and the optimized structure is divided into a proton and other parts. Here, A means a hydrogen bond acceptor, and H means a hydrogen atom.

[0018] The proton dissociation energy and the proton affinity energy can be calculated using general-purpose quantum chemical calculation software (for example, Gaussian 16 manufactured by Gaussian). Specifically, first, the total energy is minimized with respect to all bond lengths, angles, and dihedral angles of the compound (molecule, specifically, an isolated molecule in a vacuum state) to be calculated to obtain a stable structure. Then, by using the Counterpoise method to calculate the binding energy of the compound (molecule) to be calculated with a proton, it can be calculated.

[0019] As combinations of nonionic hydrogen bond donors and nonionic hydrogen bond acceptors, preferably, combinations of two selected from the group consisting of amines, amides, ureas, azoles, organic acids, ketones, phosphine oxides, sulfoxides, sulfones, alcohols, sugars, and amino acids, and derivatives thereof can be mentioned. Among these, combinations of two selected from the group consisting of amines, amides, organic acids, ketones, phosphine oxides, sulfoxides, and alcohols, and derivatives thereof are preferable. Hereinafter, the compounds that can be used as nonionic hydrogen bond donors or nonionic hydrogen bond acceptors will be described in detail.

[0020] (Definition) In the following explanation, "hydrocarbon group" means a group consisting of carbon and hydrogen. A hydrocarbon group may have a chain structure, a cyclic structure, or a structure that includes both a chain structure and a cyclic structure. Typical examples of hydrocarbon groups include aliphatic hydrocarbon groups such as alkyl groups having 1 to 30 carbon atoms and alkenyl groups having 1 to 30 carbon atoms; alicyclic hydrocarbon groups such as cycloalkyl groups having 5 to 30 carbon atoms, alkylcycloalkyl groups having 6 to 30 carbon atoms, cycloalkylalkyl groups having 6 to 30 carbon atoms, cycloalkenyl groups having 5 to 30 carbon atoms, alkylcycloalkenyl groups having 6 to 30 carbon atoms and cycloalkenylalkyl groups having 6 to 30 carbon atoms; and aromatic hydrocarbon groups such as aryl groups having 6 to 30 carbon atoms, arylalkyl groups having 7 to 30 carbon atoms and alkylaryl groups having 7 to 30 carbon atoms. Furthermore, in the following explanation, compounds with the prefixes "aliphatic," "alicyclic," and "aromatic" refer to compounds having the above-mentioned aliphatic hydrocarbon group, alicyclic hydrocarbon group, and aromatic hydrocarbon group, respectively.

[0021] Furthermore, in the following explanation, the number of carbon atoms in the compounds exemplified as nonionic hydrogen bond donors and nonionic hydrogen bond acceptors includes the number of carbon atoms in the substituents.

[0022] (Amine) The amine used in this embodiment is not particularly limited as long as it is an amine capable of forming a deep eutectic solvent with the other component. Examples include aliphatic amines, alicyclic amines, aromatic amines, heterocyclic amines, etc. Heterocyclic amines may be heterocyclic alicyclic amines or heterocyclic aromatic amines. The amine may also be a derivative to which one or more substituents have been added. Examples of substituents include hydrocarbon groups, alkoxy groups (preferably having 1 to 10 carbon atoms), polyether groups, carboxyl groups, carbonyl groups, halogen groups, nitro groups, nitroso groups, thioether groups, thiocarbonyl groups, hydroxyl groups, etc. If the amine derivative has a hydroxyl group, it may also be classified as an alcohol, but in this specification it will be classified as an amine. If the amine derivative has a carboxyl group, it may also be classified as an organic acid, but in this specification it will be classified as an amine. If the amine derivative has a carbonyl group, it may also be classified as a ketone, but in this specification it will be classified as an amine.

[0023] In this embodiment, from the viewpoint of ease of generating a deep eutectic solvent, heterocyclic aromatic amines and aromatic amines are preferred. Examples of heterocyclic aromatic amines include heterocyclic aromatic amines having 4 to 30 carbon atoms. The number of carbon atoms in the heterocyclic aromatic amine is preferably 6 to 25, more preferably 7 to 20, and even more preferably 8 to 15. Examples of heterocyclic aromatic amines having 4 to 30 carbon atoms include compounds having a pyrrole skeleton, compounds having a pyridine skeleton, compounds having an indole skeleton, compounds having a quinoline skeleton, compounds having an isoquinoline skeleton, and compounds having a carbazole skeleton. Among these, compounds having an indole skeleton (preferably 8 to 15 carbon atoms) are preferred, and indole is more preferred.

[0024] Examples of aromatic amines include aromatic amines having 6 to 30 carbon atoms. The number of carbon atoms in the aromatic amine is preferably 10 to 30, more preferably 16 to 30, and even more preferably 16 to 25. Examples of aromatic amines having 6 to 30 carbon atoms include compounds having a phenylamine skeleton, compounds having a naphthylamine skeleton, compounds having a phenylnaphthylamine skeleton, and compounds having an anthraceneamine skeleton. Among these, compounds having a phenylnaphthylamine skeleton (preferably with 16 to 25 carbon atoms) are preferred, and N-phenyl-1-naphthylamine is more preferred.

[0025] Amines may be used individually or in combination of two or more types.

[0026] (Amide) The amide used in this embodiment is not particularly limited as long as it is an amide that can form a deep eutectic solvent with the other component. Examples include aliphatic amides, alicyclic amides, and aromatic amides, which are amides having a hydrocarbon group. Here, the amide may be a derivative to which one or more substituents have been added. Examples of substituents include hydrocarbon groups, alkoxy groups (preferably having 1 to 10 carbon atoms), polyether groups, carboxyl groups, carbonyl groups, halogen groups, amino groups, nitro groups, nitroso groups, thioether groups, thiocarbonyl groups, hydroxyl groups, etc. When an amide derivative has a hydroxyl group, the derivative may also be classified as an alcohol, but in this specification it will be classified as an amide. When an amide derivative has a carboxyl group, the derivative may also be classified as an organic acid, but in this specification it will be classified as an amide. When an amide derivative has a carbonyl group, the derivative may also be classified as a ketone, but in this specification it will be classified as an amide. Furthermore, if an amide derivative has an amino group, it may also be classified as an amine; however, in this specification, it will be classified as an amide.

[0027] In this embodiment, from the viewpoint of ease of generating a deep eutectic solvent, aromatic amides are preferred. Examples of aromatic amides include aromatic amides having 7 to 30 carbon atoms. The number of carbon atoms in the aromatic amide is preferably 7 to 25, more preferably 7 to 20, and even more preferably 7 to 15. Examples of aromatic amides having 7 to 30 carbon atoms include compounds having a benzamide skeleton and compounds having an acetanilide skeleton. Among these, compounds having an acetanilide skeleton (preferably 8 to 15 carbon atoms) are preferred, compounds having an acetanilide skeleton and a hydroxyl group (preferably 8 to 15 carbon atoms) are more preferred, and 4'-hydroxyacetanilide is even more preferred.

[0028] Amides may be used individually or in combination of two or more types.

[0029] (Organic Acids) The organic acid used in this embodiment is not particularly limited as long as it is an organic acid that can form a deep eutectic solvent with the other component. Examples include organic acids having hydrocarbon groups such as fatty acids, alicyclic acids, and aromatic acids. Here, the organic acid may be a derivative to which one or more substituents have been added. Examples of substituents include hydrocarbon groups, alkoxy groups (preferably having 1 to 10 carbon atoms), polyether groups, carbonyl groups, halogen groups, nitro groups, nitroso groups, thioether groups, thiocarbonyl groups, and hydroxyl groups. Note that if the derivative of an organic acid has a hydroxyl group, the derivative may also be classified as an alcohol, but in this specification it will be classified as an organic acid. Also, if the derivative of an organic acid has a carbonyl group, the derivative may also be classified as a ketone, but in this specification it will be classified as an organic acid. Here, in this embodiment, from the viewpoint of ease of forming a deep eutectic solvent, fatty acids and aromatic acids are preferred as organic acids.

[0030] Fatty acids are preferably those having 2 to 30 carbon atoms. The number of carbon atoms in the fatty acid is preferably 2 to 20, more preferably 6 to 18, and even more preferably 8 to 16. Examples of fatty acids include octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, and hexadecanoic acid. Among these, dodecanoic acid is preferred.

[0031] Aromatic acids are preferably those having 7 to 30 carbon atoms. The number of carbon atoms in the aromatic acid is preferably 7 to 20, more preferably 7 to 16, and even more preferably 7 to 12. Examples of aromatic acids include benzoic acid and phenylpropionic acid. Among these, benzoic acid is preferred.

[0032] Organic acids may be used individually or in combination of two or more types.

[0033] (Ketone) The ketone used in this embodiment is not particularly limited as long as it is a ketone capable of forming a deep eutectic solvent with the other component. Examples include aliphatic ketones, alicyclic ketones, and ketones having hydrocarbon groups such as aromatic ketones. Lactones such as aromatic lactones and aromatic lactones having hydrocarbon groups can also be used as ketones. Here, the ketone may be a derivative to which one or more substituents have been added. Examples of substituents include hydrocarbon groups, alkoxy groups (preferably having 1 to 10 carbon atoms), polyether groups, carboxyl groups, halogen groups, nitro groups, nitroso groups, thioether groups, thiocarbonyl groups, and hydroxyl groups. Note that if a derivative of a ketone has a hydroxyl group, the derivative may also be classified as an alcohol, but in this specification, it will be classified as a ketone. Here, in this embodiment, from the viewpoint of ease of forming a deep eutectic solvent, alicyclic ketones and aromatic lactones are preferred as ketones.

[0034] Examples of alicyclic ketones include alicyclic ketones having 5 to 30 carbon atoms. The number of carbon atoms in the alicyclic ketone is preferably 8 to 20, more preferably 8 to 16, and even more preferably 8 to 12. Furthermore, it is preferable that the alicyclic ketone has a bicyclic structure (preferably with 8 to 12 carbon atoms). Camphor is a preferred example of such an alicyclic ketone.

[0035] Examples of aromatic lactones include aromatic lactones having 5 to 30 carbon atoms. The number of carbon atoms in the aromatic lactone is preferably 9 to 20, more preferably 9 to 16, and even more preferably 9 to 12. Furthermore, it is preferable that the aromatic lactone is a compound having a coumarin skeleton (preferably with 9 to 12 carbon atoms). For example, coumarin is a preferred example of such an aromatic lactone.

[0036] Ketones may be used individually or in combination of two or more types.

[0037] (Phosphine Oxide) The phosphine oxide used in this embodiment is not particularly limited as long as it is a phosphine oxide that can form a deep eutectic solvent with the other component. An example is trihydrocarbylphosphine oxide. The three hydrocarbon groups of trihydrocarbylphosphine oxide are preferably, independently, the aliphatic hydrocarbon group, alicyclic hydrocarbon group, or aromatic hydrocarbon group. Here, the phosphine oxide may be a derivative to which one or more substituents have been added. Examples of substituents include hydrocarbon groups, alkoxy groups (preferably having 1 to 10 carbon atoms), polyether groups, etc. Here, in this embodiment, from the viewpoint of ease of forming a deep eutectic solvent, trialkylphosphine oxide is preferred as the phosphine oxide.

[0038] The number of carbon atoms in the three alkyl groups of the trialkylphosphine oxide is preferably 1 to 30, more preferably 2 to 20, even more preferably 3 to 18, and even more preferably 4 to 16, independently of each other. A preferred example of such a trialkylphosphine oxide is trioctylphosphine oxide.

[0039] Phosphine oxides may be used individually or in combination of two or more types.

[0040] (Sulfoxide) The sulfoxide used in this embodiment is not particularly limited as long as it is a sulfoxide that can form a deep eutectic solvent with the other component. For example, dihydrocarbyl sulfoxide can be used. The two hydrocarbon groups of dihydrocarbyl sulfoxide are each independently an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group. Here, the sulfoxide may be a derivative to which one or more substituents have been added. Examples of substituents include hydrocarbon groups, alkoxy groups (preferably having 1 to 10 carbon atoms), and polyether groups. Here, in this embodiment, from the viewpoint of ease of forming a deep eutectic solvent, dialkyl sulfoxides and diaryl sulfoxides are preferred. The number of carbon atoms of the two alkyl groups of dialkyl sulfoxide are each independently preferably 1 to 30, more preferably 2 to 20, even more preferably 3 to 18, and even more preferably 4 to 16. As such a dialkyl sulfoxide, didodecyl sulfoxide is a preferred example. The number of carbon atoms in the two aryl groups of the diaryl sulfoxide is preferably 6 to 30, more preferably 6 to 20, and even more preferably 6 to 10, independently of each other. Diphenyl sulfoxide is a preferred example of such a diaryl sulfoxide.

[0041] Sulfoxides may be used individually or in combination of two or more types.

[0042] (Sulfone) The sulfone used in this embodiment is not particularly limited as long as it is a sulfone that can form a deep eutectic solvent with the other component. An example is dihydrocarbyl sulfone. The two hydrocarbon groups of dihydrocarbyl sulfone are, independently, the aliphatic hydrocarbon group, alicyclic hydrocarbon group, or aromatic hydrocarbon group. Here, the sulfone may be a derivative to which one or more substituents have been added. Examples of substituents include hydrocarbon groups, alkoxy groups (preferably having 1 to 10 carbon atoms), polyether groups, etc. If the derivative of the sulfone has a hydroxyl group, the derivative may also be classified as an alcohol, but in this specification it will be classified as a sulfone. Here, in this embodiment, from the viewpoint of ease of forming a deep eutectic solvent, dialkyl sulfone or diaryl sulfone is preferred as the sulfone. The number of carbon atoms of the two alkyl groups of dialkyl sulfone is, independently, preferably 1 to 30, more preferably 2 to 20, even more preferably 3 to 18, and even more preferably 4 to 16. A preferred example of such a dialkyl sulfoxide is dioctyl sulfone. The number of carbon atoms in the two aryl groups of the diaryl sulfone is preferably 6 to 30, more preferably 6 to 20, and even more preferably 6 to 10, independently of each other. A preferred example of such a diaryl sulfone is diphenyl sulfone.

[0043] Sulfones may be used individually or in combination of two or more types.

[0044] (Alcohol) The alcohol used in this embodiment is not particularly limited as long as it is an alcohol that can form a deep eutectic solvent with the other component. Examples include aliphatic alcohols, alicyclic alcohols, aromatic alcohols, etc. The alcohol may be a monoalcohol, a diol, or a polyol such as a triol. Here, the alcohol may be a derivative to which one or more substituents have been added. Examples of substituents include hydrocarbon groups, alkoxy groups, polyether groups, halogen groups, nitroso groups, thioether groups, thiocarbonyl groups, etc. Among these, from the viewpoint of ease of forming a deep eutectic solvent, alicyclic alcohols, aromatic alcohols, aromatic alcohols having a nitro group (hereinafter also referred to as "nitro aromatic alcohols"), and aromatic alcohols having a halogen group (hereinafter referred to as "halogen aromatic alcohols") are preferred.

[0045] Preferred alicyclic alcohols include those having 5 to 30 carbon atoms. The number of carbon atoms in the alicyclic alcohol is preferably 6 to 20, more preferably 6 to 16, and even more preferably 8 to 12. Here, the alicyclic alcohol is preferably a compound having a cyclohexanol skeleton (preferably with 8 to 12 carbon atoms). A preferred alicyclic alcohol is L-menthol.

[0046] Preferred aromatic alcohols include aromatic alcohols having 6 to 30 carbon atoms. The number of carbon atoms in the aromatic alcohol is preferably 6 to 20, more preferably 6 to 18. Here, the aromatic alcohol is preferably a compound having a phenol skeleton (preferably 6 to 18 carbon atoms) or a compound having a benzenediol skeleton (preferably 6 to 18 carbon atoms). Preferred aromatic monoalcohols include thymol and tert-dibutylhydroxytoluene, an aromatic monoalcohol having a hindered structure. A preferred aromatic diol is tert-butylhydroquinone, an aromatic diol having a hindered structure.

[0047] Preferably, nitroaromatic alcohols have 6 to 30 carbon atoms. The number of carbon atoms in the nitroaromatic alcohol is preferably 6 to 20, more preferably 6 to 18. Here, the nitroaromatic alcohol is preferably a compound having a nitrophenol skeleton (i.e., a nitroaromatic alcohol having 6 to 30 carbon atoms and a nitrophenol skeleton). A preferred nitroaromatic alcohol is 4-nitrophenol.

[0048] Preferably, halogenated aromatic alcohols have 6 to 30 carbon atoms. The number of carbon atoms in the halogenated aromatic alcohol is preferably 6 to 20, more preferably 6 to 18. Here, the halogenated aromatic alcohol is preferably a compound having a halogenated phenol skeleton (i.e., a halogenated aromatic alcohol having 6 to 30 carbon atoms and a halogenated phenol skeleton). The halogen is preferably chlorine. A preferred halogenated aromatic alcohol is 4-chlorocresol.

[0049] Alcohol may be used alone or in combination of two or more types.

[0050] (Carbamide) The carbamide used in this embodiment is not particularly limited as long as it is a carbamide that can form a deep eutectic solvent with the other component. Examples include urea. Here, the carbamide may be a derivative to which one or more substituents have been added. The carbamide may be used alone or in combination of two or more types.

[0051] (Azole) The azole used in this embodiment is not particularly limited as long as it is an azole capable of forming a deep eutectic solvent with the other component. Examples include pyrazole, imidazole, thiazole, oxazole, and isoxazole. Here, the azole may be a derivative to which one or more substituents have been added. The azole may be used alone or in combination of two or more types.

[0052] (Sugar) The sugar used in this embodiment is not particularly limited as long as it can form a deep eutectic solvent with the other component. Examples include monosaccharides, disaccharides, and oligosaccharides. Specific examples of sugars include sucrose, glucose, fructose, lactose, maltose, cellobiose, arabinose, ribose, ribulose, galactose, rhamnose, raffinose, xylose, mannose, and trehalose. One type of sugar may be used alone, or two or more types may be used in combination.

[0053] (Amino Acids) The amino acids used in this embodiment are not particularly limited as long as they are amino acids that can form a deep eutectic solvent with the other component. The amino acids may be amino acids that do not exist in nature or amino acids that do exist in nature. For example, the amino acids may be α-amino acids, β-amino acids, γ-amino acids, or δ-amino acids. Specific examples of amino acids include γ-aminobutyric acid, alanine, β-alanine, glutamic acid, aspartic acid, asparagine, lysine, arginine, proline, and threonine. One type of amino acid may be used alone, or two or more types may be used in combination.

[0054] <Combinations of Hydrogen Bond Donors and Hydrogen Bond Acceptors> Examples of combinations of hydrogen bond donors and hydrogen bond acceptors include the following: Hydrogen bond donors: Includes one or more selected from the group consisting of amines, amides, organic acids, and alcohols, and derivatives thereof. In this embodiment, it is preferable to use compounds among these compounds that have a proton dissociation energy of -400 kcal / mol or higher. Specifically, it is preferable to use one or more selected from the group consisting of heterocyclic aromatic amines, aromatic amines, aromatic amides, fatty acids, aromatic acids, alicyclic alcohols, and aromatic alcohols. Preferred embodiments of heterocyclic aromatic amines, aromatic amines, aromatic amides, fatty acids, aromatic acids, alicyclic alcohols, and aromatic alcohols are as previously described. Hydrogen bond acceptors: Includes one or more selected from the group consisting of ketones, phosphine oxides, alcohols, and sulfoxides, and derivatives thereof. In this embodiment, it is preferable to use compounds among these compounds that have a proton affinity energy of -180 kcal / mol or lower. Specifically, one or more selected from the group consisting of alicyclic ketones, aromatic lactones, trialkylphosphine oxides, alicyclic alcohols, aromatic alcohols, and diaryl sulfoxides are preferred. Preferred embodiments of alicyclic ketones, aromatic lactones, trialkylphosphine oxides, alicyclic alcohols, aromatic alcohols, and diaryl sulfoxides are as previously described.

[0055] Here, the hydrogen bond donor and the hydrogen bond acceptor are different compounds. "Different compounds" means that even if they are classified as alcohols, their structures are different. For example, L-menthol and thymol are both alcohols, but thymol has a higher proton dissociation energy and lower stability than L-menthol. Therefore, when L-menthol and thymol are mixed, thymol acts as a hydrogen bond donor and L-menthol acts as a hydrogen bond acceptor. As a result, even when alcohols are mixed, a deep eutectic solvent can be formed.

[0056] <Preferred Combinations of Hydrogen Bond Donors and Hydrogen Bond Acceptors> More preferred combinations of hydrogen bond donors and hydrogen bond acceptors are listed below (1) to (22). In (1) to (22) below, the compounds listed first are hydrogen bond donors, and the compounds listed second are hydrogen bond acceptors. (1) Heterocyclic aromatic amines and alicyclic ketones (2) Heterocyclic aromatic amines and aromatic lactones (3) Heterocyclic aromatic amines and trialkylphosphine oxides (4) Heterocyclic aromatic amines and alicyclic alcohols (5) Heterocyclic aromatic amines and aromatic alcohols (6) Aromatic amines and alicyclic ketones (7) Aromatic amines and aromatic lactones (8) Aromatic amines and trialkylphosphine oxides (9) Aromatic amides and trialkylphosphine oxides (10) Fatty acids and trialkylphosphine oxides (11) Fatty acids and alicyclic alcohols (12) Aromatic acids and trialkylphosphine oxides (13) Aromatic alcohols and alicyclic ketones (14) Aromatic alcohols and trialkylphosphine oxides (15) Alicyclic alcohols and alicyclic ketones (16) Alicyclic alcohols and trialkylphosphine oxides (17) Aromatic alcohols and alicyclic alcohols (18) Aromatic alcohols and alicyclic ketones (19) Aromatic alcohols and aromatic lactones (20) Aromatic alcohols and trialkylphosphine oxides (21) Aromatic alcohols and diaryl sulfoxides (22) Heterocyclic aromatic amines and diaryl sulfoxides

[0057] More preferred combinations of hydrogen bond donors and hydrogen bond acceptors are listed below (1A) to (27A). In (1A) to (27A) below, the compounds listed first are hydrogen bond donors, and the compounds listed second are hydrogen bond acceptors. (1A) Heterocyclic aromatic amines with 4 to 30 carbon atoms and alicyclic ketones with 5 to 30 carbon atoms (2A) Heterocyclic aromatic amines with 4 to 30 carbon atoms and aromatic lactones with 5 to 30 carbon atoms (3A) Heterocyclic aromatic amines with 4 to 30 carbon atoms and trialkylphosphine oxides (alkyl group has 1 to 30 carbon atoms) (4A) Heterocyclic aromatic amines with 4 to 30 carbon atoms and alicyclic alcohols with 5 to 30 carbon atoms (5A) Heterocyclic aromatic amines with 4 to 30 carbon atoms and aromatic alcohols with 6 to 30 carbon atoms (6A) Aromatic amines with 6 to 30 carbon atoms and alicyclic ketones with 5 to 30 carbon atoms (7A) Aromatic amines with 6 to 30 carbon atoms and aromatic lactones with 5 to 30 carbon atoms (8A) Aromatic amines with 6 to 30 carbon atoms and trialkylphosphine oxides (alkyl group with 1 to 30 carbon atoms) (9A) Aromatic amides with 7 to 30 carbon atoms and trialkylphosphine oxides (alkyl group with 1 to 30 carbon atoms) (10A) Fatty acids with 2 to 30 carbon atoms and trialkylphosphine oxides (alkyl group with 1 to 30 carbon atoms) (11A) Fatty acids with 2 to 30 carbon atoms and alicyclic alcohols with 5 to 30 carbon atoms (12A) Aromatic acids with 7 to 30 carbon atoms and trialkylphosphine oxides (alkyl group with 1 to 30 carbon atoms) (13A) Nitroaromatic alcohols with 6 to 30 carbon atoms and alicyclic ketones with 5 to 30 carbon atoms (14A) Nitroaromatic alcohols with 6 to 30 carbon atoms and trialkylphosphine oxides (alkyl group with 1 to 30 carbon atoms) (15A) "Aromatic diols with 6 to 30 carbon atoms" and "Trialkylphosphine oxides (alkyl group with 1 to 30 carbon atoms)" (16A) "Alicyclic alcohols with 5 to 30 carbon atoms" and "Alicyclic ketones with 5 to 30 carbon atoms" (17A) "Alicyclic alcohols with 5 to 30 carbon atoms" and "Trialkylphosphine oxides (alkyl group with 1 to 30 carbon atoms)" (18A) "Aromatic alcohols with 6 to 30 carbon atoms" and "Alicyclic alcohols with 5 to 30 carbon atoms"(19A) Aromatic alcohols with 6 to 30 carbon atoms and alicyclic ketones with 5 to 30 carbon atoms (20A) Aromatic alcohols with 6 to 30 carbon atoms and aromatic lactones with 5 to 30 carbon atoms (21A) Aromatic alcohols with 6 to 30 carbon atoms and trialkylphosphine oxides (alkyl group has 1 to 30 carbon atoms) (22A) Aromatic alcohols with 6 to 30 carbon atoms and trialkylphosphine oxides (alkyl group has 1 to 30 carbon atoms) (23A) Halogenated aromatic alcohols with 6 to 30 carbon atoms and alicyclic alcohols with 5 to 30 carbon atoms (24A) Halogenated aromatic alcohols with 6 to 30 carbon atoms and alicyclic ketones with 5 to 30 carbon atoms (25A) Halogenated aromatic alcohols with 6 to 30 carbon atoms and trialkylphosphine oxides (alkyl group has 1 to 30 carbon atoms) (26A) "Heterocyclic aromatic amines with 4 to 30 carbon atoms" and "diaryl sulfoxides (aryl group with 6 to 30 carbon atoms)" (27A) "Aromatic alcohols with 6 to 30 carbon atoms" and "diaryl sulfoxides (aryl group with 6 to 30 carbon atoms)"

[0058] Further preferred combinations of hydrogen bond donors and hydrogen bond acceptors include (1B) to (27B) listed below. In (1B) to (27B) below, the compounds listed first are hydrogen bond donors, and the compounds listed second are hydrogen bond acceptors. (1B) Compounds with 8-15 carbon atoms and an indole skeleton, and alicyclic ketones with 8-12 carbon atoms and a bicyclic structure. (2B) Compounds with 8-15 carbon atoms and an indole skeleton, and compounds with 9-12 carbon atoms and a coumarin skeleton. (3B) Compounds with 8-15 carbon atoms and an indole skeleton, and trialkylphosphine oxides (alkyl group with 4-16 carbon atoms). (4B) Compounds with 8-15 carbon atoms and an indole skeleton, and compounds with 8-12 carbon atoms and a cyclohexanol skeleton. (5B) Compounds with 8-15 carbon atoms and an indole skeleton, and aromatic alcohols with 6-30 carbon atoms. (6B) Compounds with 16-25 carbon atoms and a phenylnaphthylamine skeleton, and alicyclic ketones with 8-12 carbon atoms and a bicyclic structure. (7B) Compounds with 16-25 carbon atoms having a phenylnaphthylamine skeleton and compounds with 9-12 carbon atoms having a coumarin skeleton (8B) Compounds with 16-25 carbon atoms having a phenylnaphthylamine skeleton and trialkylphosphine oxides (alkyl group has 4-16 carbon atoms) (9B) Compounds with 8-15 carbon atoms having an acetanilide skeleton and trialkylphosphine oxides (alkyl group has 4-16 carbon atoms) (10B) Fatty acids with 8-16 carbon atoms and trialkylphosphine oxides (alkyl group has 4-16 carbon atoms) (11B) Fatty acids with 8-16 carbon atoms and compounds with 8-12 carbon atoms having a cyclohexanol skeleton (12B) Aromatic acids with 7-12 carbon atoms and trialkylphosphine oxides (alkyl group has 4-16 carbon atoms) (13B) "Nitroaromatic alcohols with a phenol skeleton and 6 to 30 carbon atoms" and "Alicyclic ketones with a bicyclic structure and 8 to 12 carbon atoms" (14B) "Nitroaromatic alcohols with a phenol skeleton and 6 to 30 carbon atoms" and "Trialkylphosphine oxides (alkyl group has 4 to 16 carbon atoms)"(15B) Compounds with 6 to 18 carbon atoms having a benzenediol skeleton and trialkylphosphine oxides (alkyl group has 4 to 16 carbon atoms) (16B) Compounds with 8 to 12 carbon atoms having a cyclohexanol skeleton and alicyclic ketones with 8 to 12 carbon atoms having a bicyclic structure (17B) Compounds with 8 to 12 carbon atoms having a cyclohexanol skeleton and trialkylphosphine oxides (alkyl group has 4 to 16 carbon atoms) (18B) Compounds with 6 to 18 carbon atoms having a phenol skeleton and compounds with 8 to 12 carbon atoms having a cyclohexanol skeleton (19B) Compounds with 6 to 18 carbon atoms having a phenol skeleton and alicyclic ketones with 8 to 12 carbon atoms having a bicyclic structure (20B) Compounds with 6 to 18 carbon atoms having a phenol skeleton and compounds with 9 to 12 carbon atoms having a coumarin skeleton (21B) "Compounds with a phenol skeleton and 6 to 18 carbon atoms" and "Trialkylphosphine oxides (alkyl group has 4 to 16 carbon atoms)" (22B) "Compounds with a phenol skeleton and 6 to 18 carbon atoms" and "Trialkylphosphine oxides (alkyl group has 4 to 16 carbon atoms)" (23B) "Halogenated aromatic alcohols with a halogenated phenol skeleton and 6 to 30 carbon atoms" and "Compounds with a cyclohexanol skeleton and 8 to 12 carbon atoms" (24B) "Halogenated aromatic alcohols with 6 to 30 carbon atoms" and "Alicyclic ketones with a bicyclic structure and 8 to 12 carbon atoms" (25B) "Halogenated aromatic alcohols with 6 to 30 carbon atoms" and "Trialkylphosphine oxides (alkyl group has 4 to 16 carbon atoms)" (26B) "Compounds with an indole skeleton and 8 to 15 carbon atoms" and "Diaryl sulfoxides (aryl group has 6 to 10 carbon atoms)" (27B) "Compounds with 6 to 18 carbon atoms having a phenol skeleton" and "Diaryl sulfoxides (aryl group has 6 to 10 carbon atoms)"

[0059] More preferred combinations of hydrogen bond donors and hydrogen bond acceptors are listed below (1C) to (27C). In (1C) to (27C) below, the compounds listed first are hydrogen bond donors, and the compounds listed second are hydrogen bond acceptors. (1C) Indole and camphor (2C) Indole and coumarin (3C) Indole and trioctylphosphine oxide (4C) Indole and L-menthol (5C) Indole and thymol (6C) N-phenyl-1-naphthylamine and camphor (7C) N-phenyl-1-naphthylamine and coumarin (8C) N-phenyl-1-naphthylamine and trioctylphosphine oxide (9C) 4'-hydroxyacetanilide and trioctylphosphine oxide (10C) Dodecanoic acid and trioctylphosphine oxide (11C) Dodecanoic acid and L-menthol (12C) Benzoic acid and trioctylphosphine oxide (13C) "4-nitrophenol" and "camphor" (14C) "4-nitrophenol" and "trioctylphosphine oxide" (15C) "tert-butylhydroquinone" and "trioctylphosphine oxide" (16C) "L-menthol" and "camphor" (17C) "L-menthol" and "trioctylphosphine oxide" (18C) "thymol" and "L-menthol" (19C) "thymol" and "camphor" (20C) "thymol" and "coumarin" (21C) "thymol" and "trioctylphosphine oxide" (22C) "tert-dibutylhydroxytoluene" and "trioctylphosphine oxide" (23C) "4-chlorocresol" and "L-menthol" (24C) "4-chlorocresol" and "camphor" (25C) "4-chlorocresol" and "trioctylphosphine oxide" (26C) "Indole" and "diphenyl sulfoxide" (27C) "Thymol" and "diphenyl sulfoxide"

[0060] <Ratio of hydrogen bond donors to hydrogen bond acceptors> The deep eutectic solvent contained in the extractant of this embodiment has a content ratio of hydrogen bond donors to hydrogen bond acceptors [hydrogen bond donors:hydrogen bond acceptors] in molar ratio, preferably 1:0.2 to 1:2.5, more preferably 1:0.3 to 1:2.0, and even more preferably 1:0.4 to 1:1.6, from the viewpoint of ease of preparation of the deep eutectic solvent.

[0061] <HSP value of deep eutectic solvent> The deep eutectic solvent contained in the extractant of this embodiment has an HSP value of D from the viewpoint of extraction efficiency. ｄ , the HSP value of hydrogen bond receptors D ａ When the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor in the extractant is x:y, the HSP value D of the deep eutectic solvent, represented by the following formula (1), is 17 MPa. ０．５ The above is preferable. D = D ｄ x + D ａ ・y...(1) However, in equation (1) above, x + y = 1. Furthermore, if at least one of the hydrogen bond donors and hydrogen bond acceptors contains two or more substances, the HSP value D of the deep eutectic solvent is calculated based on the sum of the values ​​obtained by multiplying the HSP value of each substance by the molar ratio of each substance in the extractant when the total amount of extractant is set to 1. Note that the HSP value (Hansen solubility parameter) is a physical property value defined as the square root of the cohesive energy density, and is a numerical value that indicates the dissolution behavior of the solvent. The SP value (solubility parameter) is divided into dispersion force term (δ Ｄ ), polar term (δ Ｐ ), hydrogen bond term (δ Ｈ The HSP value is a parameter that takes into account the polarity of a substance by dividing it into three components, and the relationship between the two is "δ ２ = δ Ｄ ２ +δ Ｐ ２ +δ Ｈ ２ It is expressed as ". HSP value (δ Ｄ , δ Ｐ , δ ＨWhen the HSP value of one solvent is considered as a coordinate in three-dimensional space, if the HSP value of one solvent is close to that of the other solvent, they tend to mix easily. The HSP value D of the deep eutectic solvent is 17 MPa. ０．５ The reason why the extraction efficiency is improved by the above is not entirely clear, but it is thought that, for example, highly polar substances dissolve easily while the separation from oil is high, making it easier to separate the oil from the deep eutectic solvent after processing. In the extractant of this embodiment, the HSP value D of the deep eutectic solvent is preferably 17 MPa from the viewpoint of extraction efficiency. ０．５ The above is more preferable: 18 MPa ０．５ The above is true, and more preferably 19 MPa. ０．５ The above, and more preferably 20 MPa ０．５ That concludes the explanation. Furthermore, from the viewpoint of maintaining affinity with low-polarity substances such as base oils, the HSP value D of the deep eutectic solvent is preferably 35 MPa. ０．５ The following is more preferably 30 MPa ０．５ The following, and more preferably 28 MPa ０．５ The following, and more preferably 25 MPa ０．５ The following applies. In this embodiment, the HSP value of the deep eutectic solvent can be measured specifically by the method described in the examples below.

[0062] Furthermore, from the perspective of facilitating the separation of oil and deep eutectic solvent, the HSP value D of the base oil contained in the waste oil to be extracted is important. Ｂ The difference between the HSP value D of the deep eutectic solvent contained in the extractant and (D - D) Ｂ Preferably 1 MPa ０．５ The above is more preferable to 2 MPa. ０．５ The above is true, and more preferably 3 MPa ０．５ The above, and more preferably 4 MPa ０．５ That's all. Also, (D-D Ｂ ) preferably 19 MPa ０．５ The following is more preferably 14 MPa ０．５ The following, and more preferably 12 MPa ０．５ The following, and more preferably 9 MPa ０．５The following applies. Specifically, the HSP value of the base oil can be measured by the method described in the examples below or by the Hansen molten ball method.

[0063] [Method for Producing the Extractant] In the method for producing the base oil of this embodiment, the extractant can be produced by mixing one or more nonionic hydrogen bond donors and one or more nonionic hydrogen bond acceptors to generate a deep eutectic solvent. Preferred embodiments of the nonionic hydrogen bond donors and nonionic hydrogen bond acceptors are as described above. The mixing ratio [hydrogen bond donor:hydrogen bond acceptor] of one or more nonionic hydrogen bond donors and one or more nonionic hydrogen bond acceptors is preferably 1:0.2 to 1:2.5, more preferably 1:0.3 to 1:2.0, and even more preferably 1:0.4 to 1:1.6 in molar ratio. Also preferably 1:0.4 to 1:2.5.

[0064] [Physical properties of the extractant] In the method for producing the base oil of this embodiment, the extractant preferably satisfies the following physical properties.

[0065] <Kinematic viscosity at 40°C> In the base oil production method of this embodiment, the extractant preferably has a kinematic viscosity at 40°C of 1 mm. ２ / s ~ 600mm ２ / s, comfortably 2mm ２ / s ~ 300mm ２ / s, more preferably 3 mm ２ / s ~ 100mm ２ The value is / s. In this specification, the kinematic viscosity of the extractant at 40°C means the value measured in accordance with the "Test Method for Kinematic Viscosity of Petroleum Products" specified in JIS K2283:2000.

[0066] <HSP Value> In the method for producing the base oil of this embodiment, the preferred correspondence of the HSP value D of the deep eutectic solvent contained in the extractant is as described above.

[0067] [Waste Oil] In the method for producing the base oil of this embodiment, the extractant can safely, easily, and with high yield extract one or more substances selected from the dissolved and dispersed substances in the waste oil. Therefore, the extractant of this embodiment can be used to extract one or more substances selected from the dissolved and dispersed substances in various waste oils. The one or more substances selected from the dissolved and dispersed substances in the waste oil mentioned above are not particularly limited, but examples include additives for various lubricating oil compositions such as antioxidants, anti-wear agents, metal deactivators, friction modifiers, zinc dialkyldithiophosphate, detergent dispersants, molybdenum dithiocarbamate, and ashless dispersants, as well as decomposition products, oxides, by-reaction products, sludge, and unreacted substances and catalysts remaining in the waste oil that originate from the deterioration of the lubricating oil composition. Among these substances, it is preferable that they are polar, and it is more preferable that they contain one or more substances selected from nitrogen atoms, oxygen atoms, phosphorus atoms, halogen atoms, and metal atoms.

[0068] In the base oil manufacturing method of this embodiment, there are no particular limitations on the waste oil to be processed. For example, it can be applied to lubricating oil compositions that have deteriorated due to long-term storage even before use, or to used lubricating oil compositions. Specifically, it is suitable for waste oils such as used engine oil, gear oil or hydraulic fluid, rolling oil, turbine oil, and other used industrial lubricants. It is also suitable for waste oils such as oil recovered from gas stations and automobile repair shops, used and flushing oils from various manufacturing plants, and lubricating oils that have fallen below specifications due to long-term storage.

[0069] The aforementioned additives for the lubricating oil composition are not particularly limited, but for example, the following can be used.

[0070] <Antioxidant> The antioxidant is not particularly limited, but for example, one or more selected from amine-based antioxidants and phenol-based antioxidants can be used. These antioxidants may be used individually or in combination of two or more. In this embodiment, when the waste oil contains an antioxidant as an additive, the antioxidant content is preferably 0.01 to 2% by mass based on the total amount of waste oil.

[0071] (Amine-based antioxidants) As amine-based antioxidants, diphenylamine-based antioxidants represented by general formula (a1) or naphthylamine-based antioxidants represented by (a2) are preferred.

[0072] (In general formulas (a1) and (a2), R ａ１１ ~R ａ２２ Each of these independently represents an alkyl group having 1 to 24 carbon atoms, and each of na11 to na22 independently represents an integer from 0 to 5, but within the same molecule, R ａ１１ ~R ａ２２ If multiple are present, they may be the same or different.) Examples of amine-based antioxidants include dioctyldiphenylamine, phenyl-α-naphthylamine, diphenylamine, dinonyldiphenylamine, butylphenyloctylphenylamine, octylphenyl-1-naphthylamine, p-t-octylphenyl-1-naphthylamine, and 4,4'-bis(α,α-dimethylbenzyl)diphenylamine.

[0073] (Phenol-based antioxidants) Examples of phenol-based antioxidants include monophenol-based antioxidants such as 2,6-di-t-butylphenol, 2,6-di-tert-butyl-p-cresol, 2,6-di-t-butyl-4-ethylphenol, octyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate; diphenol-based antioxidants such as 4,4'-methylenebis(2,6-di-t-butylphenol) and 2,2'-methylenebis(4-ethyl-6-t-butylphenol); hindered phenol-based antioxidants; and the like. In addition, phosphorus-containing phenol-based antioxidants represented by the following general formula (b1) can also be used as phenol-based antioxidants.

[0074] In the above general formula (b1), R ｂ１ , R ｂ２ , R ｂ３, and R ｂ４ Each of these is independently a hydrogen atom or an alkyl group having 1 to 30 carbon atoms. However, R ｂ１ , R ｂ２ , R ｂ３ , and R ｂ４ The number of carbon atoms in the alkyl group that can be selected is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 6, independently of each other. Here, the phosphorus-containing phenolic antioxidant preferably has a hindered phenol skeleton. Therefore, R ｂ１ and R ｂ２ The alkyl group that can be selected is preferably a branched alkyl group, more preferably a branched alkyl group having 1 to 6 carbon atoms, and even more preferably a tert-butyl group.

[0075] In the above general formula (b1), R ｂ５ R is an alkylene group having 1 to 5 carbon atoms. ｂ５ The number of carbon atoms in the alkylene group that can be selected is preferably 1 to 4, more preferably 1 to 3, even more preferably 1 to 2, and even more preferably 1. ｂ５ Specific examples of alkylene groups that can be selected include linear alkylene groups such as methylene, ethylene, n-propylene, n-butylene, and n-pentylene; and branched alkylene groups such as isopropylene, isobutylene, sec-butylene, tert-butylene, isopentylene, and neopentylene. Among these, the methylene group is preferred.

[0076] In this embodiment, the antioxidant contained in the waste oil is preferably one or more selected from amine-based antioxidants and phenol-based antioxidants, more preferably one or more selected from diphenylamine-based antioxidants, naphthylamine-based antioxidants and phosphorus-containing phenol-based antioxidants, and even more preferably one or more selected from dioctyldiphenylamine, octylphenyl-1-naphthylamine, butylphenyloctylphenylamine, 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid ester, 2,6-di-tert-butyl-p-cresol and octyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate.

[0077] <Anti-wear agents> Examples of anti-wear agents include sulfur-containing compounds such as zinc dialkyldithiophosphate, zinc phosphate, disulfides, sulfurized olefins, sulfurized oils and fats, sulfurized esters, thiocarbonates, thiocarbamates, and polysulfides; phosphorus-containing compounds such as phosphite esters, phosphate esters, phosphonic acid esters, and their amine salts or metal salts; and sulfur and phosphorus-containing anti-wear agents such as thiophosphite esters, thiophosphate esters, thiophosphonic acid esters, and their amine salts or metal salts. In this embodiment, when the waste oil contains an anti-wear agent as an additive, the content of the anti-wear agent is preferably 0.01% to 3% by mass based on the total amount (100% by mass) of the waste oil. Note that one type of anti-wear agent may be used alone, or two or more types may be used in combination.

[0078] (Phosphate Esters) Examples of phosphate esters include neutral phosphate esters such as aryl phosphates, alkyl phosphates, alkenyl phosphates, and alkylaryl phosphates; acidic phosphate esters such as monoaryl acid phosphates, diaryl acid phosphates, monoalkyl acid phosphates, dialkyl acid phosphates, monoalkenyl acid phosphates, and diaryl acid phosphates; phosphate esters such as aryl hydrogen phosphates, alkyl hydrogen phosphates, aryl phosphates, alkyl phosphates, alkenyl phosphates, and arylalkyl phosphates; and acidic phosphate esters such as monoalkyl acid phosphates, dialkyl acid phosphates, monoalkenyl acid phosphates, and diaryl acid phosphates. These phosphate esters may be used individually or in combination of two or more types.

[0079] Furthermore, the amine constituting the amine salt of the phosphate ester is preferably a compound represented by the following general formula (c). This amine may be used alone or in combination of two or more types.

[0080] In the general formula (c) above, q represents an integer from 1 to 3, and is preferably 1. ｃ Each of these is independently a C6-C18 alkyl group, a C6-C18 alkenyl group, a ring-forming C6-C18 aryl group, a C7-C18 arylalkyl group, or a C6-C18 hydroxyalkyl group, with a C6-C18 alkyl group being preferred. ｃ If multiple R ｃ They may be identical to each other, or they may be different to each other.

[0081] Furthermore, it is preferable that the phosphate esters include one or more selected from neutral phosphate esters, acidic phosphate esters, and amine salts of acidic phosphate esters.

[0082] As the acidic phosphate ester, compounds represented by the following general formula (d1) or compounds represented by the following general formula (d2) are preferred.

[0083] In the above general formulas (d1) and (d2), R ｄ１ and R ｄ２ Each of these is independently an alkyl group or alkenyl group having 1 to 30 carbon atoms (preferably 1 to 27, more preferably 1 to 24). ｄ１ and R ｄ２ These may be the same, or they may be different from one another.

[0084] Furthermore, as the amine salt of the acidic phosphate ester, an amine salt of the compound represented by the general formula (d1) or an amine salt of the compound represented by the general formula (d2) is preferred. In addition, as the amine constituting the amine salt of the acidic phosphate ester, a compound represented by the general formula (c) is preferred.

[0085] As neutral phosphate esters, compounds represented by the following general formula (e1) are preferred, and compounds represented by the following general formula (e2) are more preferred.

[0086] In the above general formula (e1), R ｅ１１ ~R ｅ１３ Each of these is independently an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 18 carbon atoms that is substituted with an alkyl group having 1 to 12 carbon atoms.

[0087] Furthermore, in the general formula (e2), R ｅ２１ ~R ｅ２３ Each of these is independently an alkyl group having 1 to 12 carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably an alkyl group having 1 carbon atom. Each of p1 to p3 is independently an integer from 1 to 5, preferably an integer from 1 to 2, and more preferably 1.

[0088] (Zinc dialkyldithiophosphate) Examples of zinc dialkyldithiophosphate include compounds represented by the following general formula (f).

[0089] (In the formula, R ｆ１ ~R ｆ４ Each of these independently represents a hydrocarbon group having 1 to 24 carbon atoms.

[0090] R ｆ１ ~R ｆ４ Examples of hydrocarbon groups represented include linear or branched alkyl groups having 1 to 24 carbon atoms, linear or branched alkenyl groups having 3 to 24 carbon atoms, cycloalkyl groups or linear or branched alkylcycloalkyl groups having 5 to 13 carbon atoms, aryl groups or linear or branched alkylaryl groups having 6 to 18 carbon atoms, and arylalkyl groups having 7 to 19 carbon atoms. Among these, linear or branched alkyl groups having 1 to 24 carbon atoms are preferred, and branched alkyl groups having 1 to 24 carbon atoms are more preferred. The number of carbon atoms in the branched alkyl group is preferably 2 to 12, more preferably 3 to 11, and even more preferably 4 to 10. Examples of branched alkyl groups having 1 to 24 carbon atoms include iso-propyl group, iso-butyl group, sec-butyl group, tert-butyl group, iso-pentyl group, tert-pentyl group, iso-hexyl group, 2-ethylhexyl group, iso-nonyl group, iso-decyl group, iso-tridecyl group, iso-stearyl group, and iso-icosyl group, among which the 2-ethylhexyl group is preferred.

[0091] As for zinc dialkyldithiophosphate, a selection from primary zinc dialkyldithiophosphate and secondary zinc dialkyldithiophosphate is preferred, and the inclusion of secondary zinc dialkyldithiophosphate is more preferred.

[0092] In this embodiment, as the anti-wear agent contained in waste oil, one or more selected from phosphorus-containing compounds and zinc dialkyldithiophosphate are preferable, one or more selected from phosphate esters, amine salts of phosphate esters, and zinc dialkyldithiophosphate are more preferable, one or more selected from neutral phosphate esters, acidic phosphate esters, amine salts of acidic phosphate esters, and zinc dialkyldithiophosphate are still more preferable, and one or more selected from tricresyl phosphate, oleyl acid phosphate, methyl acid phosphate-dodecylamine salt, and secondary zinc dialkyldithiophosphate are even more preferable.

[0093] <Extreme pressure agent> As the extreme pressure agent, for example, sulfur-based extreme pressure agents such as sulfides, sulfoxides, sulfones, thiophosphinates, halogen-based extreme pressure agents such as chlorinated hydrocarbons, organometallic extreme pressure agents, phosphorus-based extreme pressure agents, etc. can be mentioned. Further, among the above-mentioned anti-wear agents, a compound having a function as an extreme pressure agent can also be used. In this embodiment, when the waste oil contains an extreme pressure agent as an additive, the content of the extreme pressure agent is preferably 0.1% by mass to 5% by mass based on the total amount (100% by mass) of the waste oil. Note that the extreme pressure agent may be used alone or in combination of two or more.

[0094] (Sulfides) As sulfides, any compound having a plurality of sulfur atoms in the molecule can be used without particular limitation, but it is preferably at least one selected from the compounds represented by the following general formula (g).

[0095]

[0096] In the general formula (g), R ｇ１ and R ｇ２ are each independently a hydrocarbon group having 1 to 24 carbon atoms, and m ｇ is an integer of 2 or more and 10 or less.

[0097] R ｇ１ and R ｇ２The hydrocarbon group having 1 to 24 carbon atoms represented by includes an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an arylalkyl group, etc., and an alkyl group and an alkenyl group are more preferable, and an alkyl group is still more preferable. Further, R ｇ１ and R ｇ２ The hydrocarbon group represented by preferably has 2 to 20 carbon atoms, more preferably 4 to 17 carbon atoms, and still more preferably 8 to 15 carbon atoms.

[0098] m ｇ is an integer of 2 or more and 10 or less, preferably 3 to 9, more preferably 3 to 7, still more preferably 4 to 6, and even more preferably 5.

[0099] In the present embodiment, as the extreme pressure agent contained in the waste oil, sulfides are preferable, sulfides represented by the above general formula (g) are more preferable, and di-tert-dodecyl pentasulfide is still more preferable.

[0100] <Metal deactivator> Examples of the metal deactivator include succinic esters, benzotriazole-based compounds, tolyltriazole-based compounds, thiadiazole-based compounds, imidazole-based compounds, pyrimidine-based compounds, etc. In the present embodiment, when the waste oil contains a metal deactivator as an additive, the content of the metal deactivator is preferably 0.01% by mass to 3% by mass based on the total amount (100% by mass) of the waste oil. Note that the metal deactivator may be used alone or in combination of two or more.

[0101] (Benzotriazole-based compound) As the benzotriazole-based compound, one or more selected from the benzotriazole-based compounds conventionally used as metal deactivators can be used without particular limitation, but preferably includes a compound represented by the following general formula (h).

[0102] In the general formula (h), R ｈ１This is an alkyl group having 1 to 4 carbon atoms. This alkyl group may be linear or branched. The number of carbon atoms in this alkyl group is preferably 1 to 3, more preferably 1 to 2, and even more preferably 1.

[0103] In the above general formula (h), ph is an integer from 0 to 4. ｈ１ If there are multiple instances (i.e., if ph is an integer between 2 and 4), then multiple R ｈ１ These may be the same or different from each other. Here, from the viewpoint of making it easier to exhibit the effects of the present invention, pH is preferably 0 to 3, more preferably 0 to 1, and even more preferably 1.

[0104] In the general formula (h), R ｈ２ R is a methylene group or an ethylene group. Here, from the viewpoint of making it easier to exhibit the effects of the present invention, ｈ２ The group is preferably a methylene group.

[0105] In the general formula (h), R ｈ３ and R ｈ４ Each of these is independently a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. The alkyl group may be linear or branched, but it is preferable that it be branched to better exhibit the effects of the present invention. Furthermore, from the viewpoint of better exhibiting the effects of the present invention, the number of carbon atoms in the alkyl group is preferably 2 to 14, more preferably 4 to 12, and even more preferably 6 to 10.

[0106] (Succinate Esters) As succinate esters, esters of alkenyl succinic acid and polyhydric alcohols (alkenyl succinic acid polyhydric alcohol esters) are preferred. Furthermore, it is preferable that the ester is a half-ester. As alkenyl succinic acid constituting the alkenyl succinic acid polyhydric alcohol ester, preferably alkenyl succinic acid having alkenyl groups with 8 to 28 carbon atoms, more preferably 10 to 24 carbon atoms, and even more preferably 12 to 20 carbon atoms. As polyhydric alcohols constituting the alkenyl succinic acid polyhydric alcohol ester, diols or polyols having about 3 to 20 hydroxyl groups are preferred. Examples of diols include ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol, and dodecanediol. The aliphatic hydrocarbon groups constituting the diol may be linear or branched. Examples of polyols having approximately 3 to 20 hydroxyl groups include trimethylolethane, trimethylolpropane, trimethylolbutane, trimethylolpentane, trimethylolhexane, trimethylolheptane, di(trimethylolpropane), tri(trimethylolpropane), pentaerythritol, di(pentaerythritol), tri(pentaerythritol), glycerin, polyglycerin (2 to 20-mers of glycerin), 1,3,5-pentanetriol, and sol. Examples include polyhydric alcohols such as bitol, sorbitan, sorbitol glycerol condensate, adonitol, arabitol, xylitol, and mannitol; sugars such as xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbose, cellobiose, maltose, isomaltose, trehalose, sucrose, raffinose, gentianose, and melenitose; and their partial ethers, as well as methyl glucosides (glycosides).

[0107] In this embodiment, the metal deactivator contained in the waste oil is preferably one or more selected from succinic acid esters and benzotriazole compounds, more preferably one or more selected from alkenyl succinic acid polyhydric alcohol esters and compounds represented by the following general formula (h), and even more preferably one or more selected from dodecenyl succinic acid polyhydric alcohol esters and 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole.

[0108] <Friction Modifiers> Examples of friction modifiers include molybdenum-based friction modifiers such as molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and amine salts of molybdenum acid; ashless friction modifiers such as aliphatic amines, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, and aliphatic ethers having at least one alkyl group or alkenyl group with 6 to 30 carbon atoms in the molecule; and oils and fats, amines, amides, sulfur esters, phosphate esters, phosphite esters, and phosphate ester amine salts. In this embodiment, when a friction modifier is included as an additive to waste oil, the content of the friction modifier is preferably 0.01% to 3% by mass based on the total amount (100% by mass) of the waste oil. Note that one type of friction modifier may be used alone, or two or more types may be used in combination.

[0109] (Fatty Acid Amides) The fatty acids that make up the fatty acid amides can be either saturated or unsaturated fatty acids. The number of carbon atoms in the fatty acids is preferably 8 to 28, more preferably 12 to 24, and even more preferably 16 to 20. Examples of saturated fatty acids include caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, palmitoleic acid, margaric acid, stearic acid, isostearic acid, nonadecylic acid, arachidic acid, henicosyl acid, and behenic acid. Furthermore, examples of such unsaturated fatty acids include monounsaturated fatty acids such as myristoleic acid, palmitoleic acid, oleic acid, eicosenoic acid, and erucic acid; and polyunsaturated fatty acids such as linoleic acid, linolenic acid, stearidonic acid, eicosadienoic acid, meadic acid, arachidonic acid, eicosapentaenoic acid, docosadienoic acid, docosapentaenoic acid, and docosahexaenoic acid. Furthermore, examples of amides that constitute fatty acid amides include polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and polyethyleneimine with a number average molecular weight of 300 to 200,000; alkanolamines such as monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, tri-n-propanolamine, tri-n-butanolamine, triisobutanolamine, tri-tert-butanolamine, N-methylethanolamine, N-ethylethanolamine, N-butylethanolamine, N-cyclohexylethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N-cyclohexyldiethanolamine, N,N-dimethylethanolamine, and N,N-diethylethanolamine; and alkylamines such as methylamine, dimethylamine, ethylamine, diethylamine, propylamine, and dipropylamine.

[0110] (Molybdenum dithiocarbamate) Examples of molybdenum dithiocarbamate include dinuclear molybdenum dithiocarbamate containing two molybdenum atoms in one molecule, and trinuclear molybdenum dithiocarbamate containing three molybdenum atoms in one molecule, but dinuclear molybdenum dithiocarbamate is preferred.

[0111] Examples of dinuclear molybdenum dithiocarbamates include compounds represented by the following general formula (i1) or compounds represented by the following general formula (i2).

[0112]

[0113] In the above general formulas (i1) and (i2), R ｉ１ ~R ｉ４ Each of these independently represents a hydrocarbon group, which may be identical or different from one another. ｉ１ ~X ｉ８ Each of these independently represents either an oxygen atom or a sulfur atom, and they may be the same or different from each other. However, X in formula (i1) ｉ１ ~X ｉ８ At least two of them are sulfur atoms. ｉ１ ~R ｉ４ The number of carbon atoms in the hydrocarbon group that can be selected is preferably 6 to 22, and more preferably 6 to 16.

[0114] In the above general formulas (i1) and (i2), R ｉ１ ~R ｉ４Examples of hydrocarbon groups that can be selected include alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups, alkylaryl groups, and arylalkyl groups. These may be linear or branched. Examples of alkyl groups include hexyl groups, heptyl groups, octyl groups, nonyl groups, decyl groups, undecyl groups, dodecyl groups, tridecyl groups, tetradecyl groups, pentadecyl groups, hexadecyl groups, heptadecyl groups, and octadecyl groups. Examples of alkenyl groups include hexenyl groups, heptenyl groups, octenyl groups, nonenyl groups, decenyl groups, undecenyl groups, dodecenyl groups, tridecenyl groups, tetradecenyl groups, and pentadecenyl groups. Examples of the cycloalkyl group include cyclohexyl group, dimethylcyclohexyl group, ethylcyclohexyl group, methylcyclohexylmethyl group, cyclohexylethyl group, propylcyclohexyl group, butylcyclohexyl group, and heptylcyclohexyl group. Examples of the aryl group include phenyl group, naphthyl group, anthracenyl group, biphenyl group, and terphenyl group. Examples of the alkylaryl group include tolyl group, dimethylphenyl group, butylphenyl group, nonylphenyl group, and dimethylnaphthyl group. Examples of the arylalkyl group include methylbenzyl group, phenylmethyl group, phenylethyl group, and diphenylmethyl group.

[0115] In this embodiment, the friction modifier contained in the waste oil is preferably one or more selected from molybdenum-based friction modifiers and ashless friction modifiers, more preferably one or more selected from molybdenum dithiocarbamate and fatty acid amides, even more preferably one or more selected from fatty acid amides consisting of unsaturated fatty acids and polyamines, fatty acid amides consisting of saturated fatty acids and alkanolamines, and dinuclear molybdenum dithiocarbamate, and even more preferably one or more selected from isostearate tetraethylenepentamine condensate amide, oleic acid diethanolamide, and the compound represented by the above general formula (i2).

[0116] <Metal-based detergents> Examples of metal-based detergents include organic acid metal salt compounds containing metal atoms selected from alkali metals and alkaline earth metals. Specifically, examples include metal salicylates, metal phenates, and metal sulfonates containing metal atoms selected from alkali metals and alkaline earth metals. In this specification, "alkali metals" refer to lithium, sodium, potassium, rubidium, cesium, and francium, and "alkaline earth metals" refer to beryllium, magnesium, calcium, strontium, and barium. From the viewpoint of improving cleaning performance at high temperatures, sodium, calcium, magnesium, or barium are preferred as metal atoms to be contained in the metal-based detergent, and calcium is more preferred. In this embodiment, when the waste oil contains a metal-based detergent as an additive, the content of the metal-based detergent is preferably 0.01% to 10% by mass based on the total amount (100% by mass) of the waste oil. One type of metal-based detergent may be used alone, or two or more types may be used in combination.

[0117] Furthermore, among metal-based detergents, it is preferable that one or more are selected from calcium salicylate, calcium phenate, and calcium sulfonate, from the viewpoint of improving cleaning performance at high temperatures and solubility in the base oil, and calcium salicylate is more preferable.

[0118] The metal-based detergent may be a neutral salt, a basic salt, an overbasic salt, or a mixture thereof, but an overbasic salt is preferred. The total base number of the metal-based detergent is preferably 0 to 600 mg KOH / g. If the metal-based detergent is a basic salt or an overbasic salt, the total base number of the metal-based detergent is preferably 10 to 600 mg KOH / g, more preferably 20 to 500 mg KOH / g. In this specification, the "base number" of the metal-based detergent refers to the base number measured by the perchloric acid method in accordance with JIS K2501:2003 "Petroleum products and lubricating oils - Neutralization number test method" 7.

[0119] In this embodiment, perbasic calcium salicylate is preferred as the metal-based detergent contained in the waste oil.

[0120] <Ashless Dispersants> Examples of ashless dispersants include succinimide, benzylamine, succinic acid esters, or boron-modified products thereof. In this embodiment, when the waste oil contains an ashless dispersant as an additive, the content of the ashless dispersant is preferably 0.1% to 20% by mass, based on the total amount (100% by mass) of the waste oil. The ashless dispersant may be used alone or in combination of two or more types.

[0121] Examples of alkenyl succinimides include alkenyl succinate monoimides represented by the following general formula (j1), or alkenyl succinate bisimides represented by the following general formula (j2). The alkenyl succinimide may also be a modified alkenyl succinimide obtained by reacting a compound represented by the following general formula (j1) or (j2) with one or more selected from alcohols, aldehydes, ketones, alkylphenols, cyclic carbonates, epoxy compounds, and organic acids. Furthermore, examples of boron-modified alkenyl succinimides include boron-modified compounds of the compounds represented by the following general formula (j1) or (j2).

[0122]

[0123] In the above general formulas (j1) and (j2), R ｊＡ , R ｊＡ１ and R ｊＡ２ Each of these is an alkenyl group having a mass-average molecular weight (Mw) of 500 to 3,000 (preferably 1,000 to 3,000), and is preferably a polybutenyl group or a polyisobutenyl group, with polybutenyl group being more preferred. ｊＢ , R ｊＢ１ and R ｊＢ２ These are, independently, alkylene groups having 2 to 5 carbon atoms. ｊＣ is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or -(AO) ｎｊ - A group represented by H (where A is an alkylene group having 2 to 4 carbon atoms, n ｊx1 is an integer from 1 to 10, preferably from 2 to 5, more preferably from 3 or 4. x2 is an integer from 0 to 10, preferably from 1 to 4, more preferably from 2 or 3. In this specification, the mass-average molecular weight (Mw) is a value on a standard polystyrene basis measured by gel permeation chromatography (GPC).

[0124] From the viewpoint of improving cleanliness, the ratio of boron atoms to nitrogen atoms [B / N] constituting the boron-modified alkenyl succinimide is preferably 0.5 or higher, more preferably 0.6 or higher, even more preferably 0.8 or higher, and even more preferably 0.9 or higher.

[0125] In this embodiment, the ashless dispersant contained in the waste oil is preferably one or more selected from alkenyl succinimide and boron-modified alkenyl succinimide, and preferably one or more selected from polybutenyl succinimide and boronated polybutenyl succinimide.

[0126] [Extractant Composition] The extractant composition of this embodiment contains the extractant. The extractant composition of this embodiment may consist only of the extractant, but may also contain other components besides the extractant. Examples of other components include additives for extractants.

[0127] <Extractant Additives> The extractant composition of this embodiment may further contain extractant additives, to the extent that they do not impair the effects of this embodiment. As the extractant additive, extractant additives commonly used in extractant compositions can be appropriately selected. Examples include surfactants, reducing agents, oxidizing agents, etc.

[0128] If the extractant composition contains an extractant additive, the total content of the extractant additive is preferably 0.01% to 40% by mass, more preferably 0.1% to 20% by mass, even more preferably 0.1% to 10% by mass, and even more preferably 0.1% to 5% by mass, based on the total amount of the extractant composition.

[0129] [Properties of the Extractant Composition] The extractant composition of this embodiment preferably satisfies the above requirements described as properties of the extractant. The preferred range is also as described above.

[0130] [Extraction Set] The extractant of this embodiment may be in the form of a deep eutectic solvent, which is a mixed product obtained by mixing a hydrogen bond donor and a hydrogen bond acceptor, or it may be in the form of an extraction set containing the hydrogen bond donor and hydrogen bond acceptor, which are included in the extractant of this embodiment, in an unmixed state. The extraction set of this embodiment is configured such that, for example, a first composition containing a hydrogen bond donor and a second composition containing a hydrogen bond acceptor are mixed and used for extraction. In this case, the first composition and the second composition, before mixing, are stored and distributed separately as components of the extraction set containing them, and are mixed at the time of use. The storage and distribution form of the first composition and the second composition is not particularly limited as long as it is such that they are not unintentionally mixed, but for example, a form in which the first composition and the second composition are each contained in glass bottles is envisioned. Furthermore, if components other than the extractant of this embodiment, such as extractant additives, are used, they may be added to the first and second compositions beforehand, or they may be included as a third composition, stored and distributed separately from the first and second compositions.

[0131] [Method for Manufacturing Base Oil] The method for manufacturing base oil according to this embodiment includes an extraction step of mixing waste oil with an extractant containing a non-oil-soluble deep eutectic solvent to extract one or more substances selected from the dissolved and dispersed substances, and a waste oil treatment oil addition step of adding the waste oil treated oil that has undergone the extraction step to the base oil manufacturing step. The extractant according to this embodiment can easily extract one or more substances selected from the dissolved and dispersed substances in the waste oil, and by using this extractant, it is possible to provide a method for manufacturing base oil that includes an extraction step that can efficiently remove one or more substances selected from the dissolved and dispersed substances in the waste oil in a simple manner. Furthermore, the extractant according to this embodiment can efficiently extract a wide range of substances in waste oil, such as additives for various lubricating oil compositions, decomposition products, oxides, by-reaction products, sludge, and unreacted substances and catalysts remaining in the waste oil, and is therefore applicable to a wide range of waste oils. Furthermore, the extractant of this embodiment can be used not only for extracting lubricating oil compositions that have deteriorated due to long-term storage, etc., even before use, or used lubricating oil compositions, but also for extracting one or more substances selected from dissolved and dispersed substances contained in one or more substances selected from the group consisting of low-polarity hydrocarbons and organic substances, even before use, or after use, which have deteriorated due to long-term storage, etc. For example, in the base oil production method of this embodiment, one or more substances selected from the group consisting of low-polarity hydrocarbon oils and organic substances, even before use, or after use, which have deteriorated due to long-term storage, etc., may be used as the processing target to produce one or more substances selected from the group consisting of low-polarity hydrocarbon oils and organic substances. Specific examples of low-polarity hydrocarbons include crude oil and heavy oils such as C heavy oil, and specific examples of organic substances include oils and fats. Furthermore, in the base oil production method of this embodiment, the extractant may be used in the form of an extractant composition.

[0132] Figures 16 and 17 are flow charts showing a preferred embodiment of the method for producing the base oil according to this embodiment. The method for producing the base oil according to this embodiment will be described below with reference to Figures 16 and 17.

[0133] [Extraction Step (S2)] As shown in Figure 16, the method for producing the base oil of this embodiment includes an extraction step (S2) in which an extractant containing a non-oil-soluble deep eutectic solvent is mixed with waste oil to extract one or more substances selected from the dissolved and dispersed substances. The extraction method is not particularly limited, but a specific extraction method is, for example, a method in which the waste oil and the extractant are mixed and then stirred so that the waste oil and the extractant are thoroughly mixed. There are batch methods and flow methods for mixing and stirring, and either is acceptable. Furthermore, from the viewpoint of promoting the extraction of one or more substances selected from the dissolved and dispersed substances in the waste oil, it is preferable to perform operations such as heating. In addition, the details of the nonionic hydrogen bond donor and nonionic hydrogen bond acceptor contained in the extractant in the method for producing the base oil of this embodiment are as described above. In the method for producing the base oil of this embodiment, the content of the non-oil-soluble deep eutectic solvent in the extractant is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 100% by mass, based on the total amount of the extractant. Furthermore, in the method for producing the base oil of this embodiment, the extractant is preferably a deep eutectic solvent.Furthermore, there are no particular restrictions on the order in which the waste oil and the extractant containing the non-oil-soluble deep eutectic solvent are mixed. For example, the waste oil may be brought into contact with one or more nonionic hydrogen bond donors first, and then into contact with one or more nonionic hydrogen bond acceptors, thereby mixing the waste oil with the extractant containing the non-oil-soluble deep eutectic solvent; or the waste oil may be brought into contact with one or more nonionic hydrogen bond acceptors first, and then into contact with one or more nonionic hydrogen bond donors, The waste oil may be mixed with an extractant containing a non-oil-soluble deep eutectic solvent; or, an extractant containing a non-oil-soluble deep eutectic solvent may be prepared by first contacting one or more selected nonionic hydrogen bond donors with one or more selected nonionic hydrogen bond acceptors, and then mixing the extractant with the waste oil; or, the waste oil may be mixed with an extractant containing a non-oil-soluble deep eutectic solvent by simultaneously contacting the waste oil with one or more selected nonionic hydrogen bond donors and one or more selected nonionic hydrogen bond acceptors. From the viewpoint of extraction efficiency, it is preferable to prepare an extractant containing a non-oil-soluble deep eutectic solvent in the extractant preparation step (S1) described later, and then mix the extractant with the waste oil.

[0134] <Mixing ratio of extractant and waste oil> In the method for producing base oil of this embodiment, the mixing ratio of the extractant and waste oil is not particularly limited as long as it does not affect extraction. However, a higher mixing ratio of (extractant) / (waste oil) improves the extraction rate, while a lower mixing ratio reduces the amount of recycled oil recovered per extraction treatment. Therefore, the mixing ratio of the extractant and waste oil is preferably 5.0 or less by volume, more preferably 3.0 or less, and even more preferably 2.0 or less. Furthermore, the aforementioned ratio of (extractant) / (waste oil) is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 1 / 3 or more, and even more preferably 0.5 or more. Based on the above, the aforementioned ratio of (extractant) / (waste oil) is preferably 0.1 to 5.0, more preferably 0.2 to 3.0, even more preferably 1 / 3 to 2.0, and even more preferably 0.5 to 2.0. Furthermore, even if the amount of extractant is small relative to the waste oil, repeated extraction can sufficiently extract one or more substances that can be selected from the dissolved and dispersed materials in the waste oil. Also, when using an extractant composition containing other components besides the extractant, the amount of extractant contained in the extractant composition should be mixed so that it falls within the above-mentioned range.

[0135] [Waste Oil Treatment Addition Step (S100)] The base oil manufacturing method of this embodiment includes a waste oil treatment addition step in which waste oil treatment, which has gone through the extraction step (S2), is added to the base oil manufacturing step. The waste oil treatment addition step is a step in which waste oil treatment (referring to at least the oil that has gone through the extraction step (S2), and may be the oil separated from the mixture obtained in the separation and recovery step (S3) described later, or the oil washed in the refining step (S5) described later, or the oil that has undergone further refining or other operations after the refining step (S5)) is added to the base oil manufacturing step (T) described later. The method of adding waste oil treatment to the base oil manufacturing step is not particularly limited, and for example, the waste oil treatment may be directly put into the apparatus that carries out the base oil manufacturing step to which it is to be added, or the waste oil treatment may be mixed with the base oil raw materials in advance, and the mixture may be put into the apparatus that carries out the base oil manufacturing step to which it is to be added. Here, there are no particular restrictions on the base oil to which the waste oil treatment oil is added, and any of the mineral oils and synthetic oils conventionally used as base oils for lubricating oils can be appropriately selected and used. Furthermore, when the base oil to which the waste oil treatment oil is added is mineral oil, there are no particular restrictions on the manufacturing process to which the waste oil treatment oil is added, but examples include solvent dewaxing processes; solvent extraction processes; dewaxing processes such as solvent dewaxing and catalytic dewaxing; and hydrorefining processes such as hydrocracking processes, advanced hydrocracking processes, and hydrofinishing processes (processes for refining mineral oil base oil by catalytic hydroreaction). Among these, it is preferable to include at least one of the hydrorefining process and the dewaxing process. The manufacturing process to which the waste oil treatment oil is added can be appropriately selected based on the physical properties of the waste oil treatment oil, such as sulfur content and saturation content, and the physical properties of the base oil to be manufactured, such as sulfur content and saturation content. For example, as shown in Figure 17, when the base oil manufacturing process (T) includes a vacuum distillation process T1, a hydrocracking process T2, a dewaxing process T3, and a finishing hydroprocessing process T4, the waste oil treatment may be added to process T2 (addition route A), to process T3 (addition route B), or to both processes T2 and T3. Furthermore, the amount of waste oil treatment added is not particularly limited. In addition, if there are preferred physical properties required in the manufacturing process of the base oil to which the treatment is added, the treatment may be adjusted to satisfy those requirements.

[0136] [Waste Oil Recovery Process (S0)] The method for producing base oil in this embodiment preferably includes a waste oil recovery process (S0) for recovering waste oil that is the subject of recycling treatment, as shown in Figure 16. The method for recovering waste oil is not particularly limited, but typically waste oil generated at gas stations, automobile repair shops, and various manufacturing plants is stored in waste oil tanks and recovered by waste oil recovery companies.

[0137] [Extractant Manufacturing Process (S1)] The method for producing the base oil of this embodiment, as shown in Figure 16, includes an extractant manufacturing process (S1) before the extraction process (S2) in which an extractant containing a non-oil-soluble deep eutectic solvent, which is a mixed product of one or more nonionic hydrogen bond donors and one or more nonionic hydrogen bond acceptors, is produced, and it is preferable to use the obtained extractant in the extraction process (S2). In the method for producing the base oil of this embodiment, the extractant can be produced by mixing one or more nonionic hydrogen bond donors and one or more nonionic hydrogen bond acceptors to produce a deep eutectic solvent, and the details thereof are as described above.

[0138] [Separation and Recovery Process (S3)] The method for producing the base oil in this embodiment preferably further includes a separation and recovery process (S3), as shown in Figure 16, in which the extractant and oil are separated and recovered from the mixture obtained in the extraction process (S1) after one or more substances selected from the dissolved matter and dispersion have been extracted and removed. The separation and recovery process is a process in which the extractant and oil are separated and recovered from the mixture in which the extractant and waste oil have been brought into contact in the aforementioned extraction process and the extraction of one or more substances selected from the dissolved matter and dispersion has progressed. In other words, the extractant from which one or more substances selected from the dissolved matter and dispersion have been extracted and the oil from which one or more substances selected from the dissolved matter and dispersion have been removed are separated and recovered. As for specific separation and recovery methods, for example, the deep eutectic solvent, which is the extractant, and the oil can be recovered by static separation, in which the mixture of the extractant and oil is left to stand for about a day and phase separation occurs. Furthermore, from the viewpoint of promoting the separation of the extractant and oil, it is preferable to combine operations such as centrifugation and heating with the mixture. As described above, static separation is a method of separating the extractant (deep eutectic solvent) and the oil by allowing the mixture of the extractant and the oil to stand. The standing time is preferably 1 hour or more, more preferably 6 hours or more, even more preferably 12 hours or more, and most preferably 24 hours or more. There is no particular upper limit; any time that allows sufficient separation of the extractant (deep eutectic solvent) and the oil is acceptable. There is no particular limit to the standing temperature, but it is usually 10 to 80°C, preferably 20 to 60°C, and more preferably 20 to 50°C. Furthermore, it is preferable to perform separation using a centrifuge to promote separation. By centrifugation, the mixture can be separated into an extractant phase (deep eutectic solvent phase), a small amount of suspension phase, and an oil phase due to the difference in specific gravity. There are no particular limitations to the centrifugation conditions, but the temperature of the mixture (regenerated liquid) during centrifugation is usually 10 to 80°C, preferably 20 to 60°C, and more preferably 20 to 50°C. Furthermore, the centrifugal force during centrifugation is typically 160 to 16,000 G, preferably 600 to 10,000 G, and more preferably 1,500 to 4,000 G. The centrifugation time is typically 1 to 20 minutes, preferably 1 to 15 minutes, and more preferably 1 to 10 minutes.

[0139] [Extractant Regeneration Process (S4)] The method for producing the base oil in this embodiment preferably further includes an extractant regeneration process (S4) for the extractant obtained in the separation and recovery process (S3), as shown in Figure 16. Generally, waste oil contains elements such as nitrogen, phosphorus, sulfur, calcium, zinc, molybdenum, and boron, which are derived from one or more substances selected from dissolved and dispersed materials such as degraded products and residual additives of the lubricating oil composition. Most of these elements in the waste oil are removed in the extraction process (S2), and these are contained in the deep eutectic solvent, which is the extractant. Therefore, by separating and regenerating the deep eutectic solvent, which is the extractant, from one or more substances selected from the dissolved and dispersed materials, the amount of waste can be minimized by extracting waste containing one or more substances selected from the dissolved and dispersed materials. The extractant containing one or more substances selected from the dissolved and dispersed materials separated in the above-mentioned separation and recovery process can be reused by regeneration. Specifically, for example, one method involves distilling the deep eutectic solvent, which is the extractant, under reduced pressure to purify the nonionic hydrogen bond donors and nonionic hydrogen bond acceptors that constitute the deep eutectic solvent. Depending on their boiling points, the hydrogen bond donors and acceptors can be recovered separately or in a mixed state without issue. The recovered hydrogen bond donors and acceptors can be mixed again to form a deep eutectic solvent, which can then be regenerated as an extractant. If, after distillation recovery, the amount of either the hydrogen bond donors or hydrogen bond acceptors falls short of the optimal composition range for the deep eutectic solvent, the deficiency can be compensated for by adding the missing amount, thereby regenerating the extractant to have performance equivalent to the original extractant. Therefore, in the method for producing base oil according to this embodiment, it is preferable that the extractant or the extractant composition includes a regenerated extractant obtained by an extractant regeneration step that regenerates the extractant or extractant composition obtained by the separation and recovery step. Reusing used extractants in this way is preferable from the viewpoint of reducing raw material costs and waste volume, and can provide an inexpensive processing method.Furthermore, if the waste oil contains degraded products or impurities with lighter components than the boiling points of the hydrogen bond donors and hydrogen bond acceptors of the deep eutectic solvent, it is desirable to distill them off before the waste oil extraction process or before the extractant regeneration process. If lighter components are mixed into the hydrogen bond donors or hydrogen bond acceptors to be regenerated, it may become impossible to regenerate a high-purity extractant. In addition to vacuum distillation, another method is to add a large amount of either the nonionic hydrogen bond donors or nonionic hydrogen bond acceptors that constitute the deep eutectic solvent to the deep eutectic solvent after extraction, thereby disrupting the balance of the eutectic melting point depression and returning the deep eutectic solvent to a solid state, and then washing it with lubricating oil or the like to recover the nonionic hydrogen bond donors and nonionic hydrogen bond acceptors. However, to regenerate a high-purity extractant, distillation purification is preferable. That is, one aspect of this embodiment provides a method for regenerating a used extractant, in which the used extractant after the separation and recovery process in the base oil production method of this embodiment is regenerated by vacuum distillation. The conditions for vacuum distillation can be appropriately set according to the composition of the used extractant, but for example, 80 to 200°C and 0.13 to 6.65 kPa are preferred. Furthermore, even if the extractant composition containing components other than the extractant is regenerated in the separation and recovery process, the extractant contained in the extractant composition can be recovered by methods such as vacuum distillation to obtain a regenerated extractant.

[0140] [Refining Process (S5)] The method for producing the base oil in this embodiment preferably further includes a refining process (S5) in which the oil obtained in the separation and recovery process is washed with a non-oil-soluble light solvent, as shown in Figure 16. By including this refining process, even if a small amount of extractant is mixed in the recovered oil, it can be washed away. Specifically, the refining process is a process of washing the recovered oil with a non-oil-soluble light solvent such as methanol or acetonitrile to remove the extractant remaining in the oil. The oil washed in the refining process can be used as recycled oil as is after the light washing solvent is distilled off, or it can be used as new oil by putting it through a refining apparatus again. Furthermore, the washing solvent containing the extractant used for washing can be mixed with the extractant regeneration process described above, making it possible to regenerate the extractant and washing solvent remaining in the oil. Reusing used extractants and washing solvents from this system leads to further cost reduction and a reduction in the amount of waste to be processed. In this specification, a non-oil-soluble light solvent means a light solvent whose HSP value is, for example, 17 MPa. ０．５ This means that the HSP value is 18 MPa. ０．５ It may be greater than or equal to 19 MPa ０．５ It may be greater than or equal to 20 MPa ０．５ The above is also acceptable. As for the non-oil-soluble light solvent, there are no particular restrictions as long as it satisfies the above-mentioned HSP value conditions, but for example, methanol, acetonitrile, diethyl ether, ethylene glycol, etc. can be used.

[0141] [Pretreatment step (S10)] The method for producing base oil in this embodiment preferably includes, in addition to S0 to S5 above, a pretreatment step (S10) in which the waste oil to be treated is pretreated before the extraction step, as shown in Figure 17. In the method for producing base oil in this embodiment, recycled oil is produced by extracting one or more substances selected from dissolved and dispersed substances from the waste oil using an extractant. Here, the fewer impurities in the waste oil, the higher the purity of the extracted oil, the higher the extraction efficiency, and the easier the handling. Therefore, pretreatment of the recovered waste oil by filtration and / or distillation and / or adsorption is an effective method for producing recycled oil. There are no particular limitations on the specific pretreatment method, but examples include filtration, distillation, and adsorption as described above, and among these, it is preferable to perform at least distillation, and more preferably at least vacuum distillation. The conditions for vacuum distillation can be appropriately set according to the composition of the waste oil, etc., but for example, 200 to 350°C and 0.13 to 6.65 kPa are preferred.

[0142] [Base Oil Manufacturing Apparatus] The base oil manufacturing apparatus of this embodiment comprises an extraction facility for mixing waste oil with an extractant containing a non-oil-soluble deep eutectic solvent to extract one or more substances selected from the dissolved and dispersed products, a base oil manufacturing facility, and an additive facility for adding the waste oil treated by the extraction facility to the base oil manufacturing facility.

[0143] Figure 18 is a flow chart showing a preferred embodiment of the base oil manufacturing apparatus of this embodiment. The base oil manufacturing apparatus of this embodiment will be described below with reference to Figure 18.

[0144] The base oil production apparatus of this embodiment, as shown in Figure 18, includes an extraction unit (E2), a base oil production unit (ET), and an additive unit (E6). The extraction unit (E2) is not particularly limited as long as it can carry out the extraction process described above, and for example, a mixing tank equipped with a stirring blade as shown in Figure 18 can be used. Furthermore, if heating is performed in the extraction process, it is preferable to further provide heating equipment such as a heater. The base oil production unit (ET) is not particularly limited as long as it can carry out the base oil production process described above, and for example, examples include solvent dewaxing equipment; solvent extraction equipment; dewaxing equipment such as solvent dewaxing equipment and catalytic dewaxing equipment; and hydrocracking equipment such as hydrocracking equipment, advanced hydrocracking equipment, and hydrofinishing equipment. It may also include vacuum distillation equipment and the like necessary for the production of other base oils. The additive unit (E6) is not particularly limited as long as it can carry out the waste oil treatment oil addition process described above, and for example, equipment equipped with oil supply piping, oil supply pump, flow meter and control valve for adjusting the flow rate, and various sensors can be used. In the base oil manufacturing apparatus of this embodiment, the details of the waste oil, extractant, extraction process, base oil manufacturing process, and waste oil treatment oil addition process are as described above.

[0145] Furthermore, as shown in Figure 18, the base oil production apparatus of this embodiment preferably further comprises one or more pieces of equipment selected from waste oil storage equipment (E0), extractant production equipment (E1), separation and recovery equipment (E3), extractant regeneration equipment (E4), refining equipment (E5), and pretreatment equipment (E10). The waste oil storage equipment (E0) is equipment for temporarily storing the waste oil to be treated, and is usually a storage tank. The extractant production equipment (E1) is not particularly limited as long as it can mix one or more selected from nonionic hydrogen bond donors and one or more selected from nonionic hydrogen bond acceptors, for example, as shown in Figure 18, a mixing tank equipped with a stirring blade can be used. The separation and recovery equipment (E3) is not particularly limited as long as it can separate and recover the extractant and the oil. For example, when separating and recovering the extractant and the oil by static separation, equipment can be used that includes a storage tank for allowing the mixture obtained from the extraction operation by the aforementioned extraction equipment to stand, and piping that allows the extractant and the oil to be recovered separately. It may also have a liquid level gauge, a density meter, etc. as needed, and may further include a centrifugal separator or heating equipment such as a heater as needed. In addition, the separation and recovery process may be carried out by performing the extraction operation by the aforementioned extraction equipment, then allowing the mixture to stand and separate within the extraction equipment. In this case, the extraction equipment and the separation and recovery equipment are the same. Also, in Figure 18, the extractant 12 is in the lower layer and the oil 13 is in the upper layer in the separation and recovery equipment, but the manner of layer separation is determined by the specific gravity of the extractant and the oil, and this embodiment is not limited to this. The extractant regeneration equipment (E4) is, for example, a distillation equipment when the extractant is regenerated by distillation. The purification equipment (E5) can, for example, use a mixing tank equipped with a stirring blade as shown in Figure 18, and preferably also has equipment for distilling off the non-oil-soluble light solvent used in purification. The pretreatment equipment (E10) can be determined according to the type of pretreatment process to be carried out, and examples include filtration equipment equipped with a filter, distillation equipment, adsorption equipment equipped with an adsorbent such as zeolite, and it is preferable to include at least distillation equipment.In the base oil production apparatus of this embodiment, the details of the waste oil recovery process, extractant production process, separation and recovery process, extractant regeneration process, refining process, and pretreatment process corresponding to the waste oil storage facility (E0), extractant production facility (E1), separation and recovery facility (E3), extractant regeneration facility (E4), refining facility (E5), and pretreatment facility (E10) are as described above.

[0146] [An Embodiment of the Invention Provided] According to one embodiment of the present invention, the following [1] to

[12] are provided. [1] A method for producing a base oil, comprising: an extraction step of mixing an extractant containing a non-oil-soluble deep eutectic solvent with waste oil to extract one or more substances selected from the dissolved and dispersed products; and a waste oil treatment step of adding the waste oil treated through the extraction step to a base oil production step. [2] The method for producing a base oil according to [1], wherein in the extraction step, the extractant is mixed with the waste oil so that, on a volume basis, (extractant) / (waste oil) is 0.1 to 5.0. [3] The method for producing a base oil according to [1] or [2], comprising an extractant production step of producing an extractant containing a non-oil-soluble deep eutectic solvent which is a mixed product of one or more nonionic hydrogen bond donors and one or more nonionic hydrogen bond acceptors, before the extraction step, wherein the obtained extractant is used in the extraction step. [4] The method for producing a base oil according to [3], wherein the hydrogen bond donor has a proton dissociation energy of -400 kcal / mol or more, and the hydrogen bond acceptor has a proton affinity energy of -180 kcal / mol or less. [5] The HSP value of the hydrogen bond donor is D ｄ , the HSP value of the hydrogen bond receptor is D ａ When the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor in the extractant is x:y, the HSP value D of the deep eutectic solvent, represented by the following formula (1), is 17 MPa. ０．５ The method for producing the base oil described in [3] or [4] above. D = D ｄ x + D ａ- y...(1) However, in formula (1) above, x + y = 1. [6] A method for producing a base oil according to any one of [1] to [5], wherein the base oil production step for adding the waste oil treatment oil comprises at least one of a hydrogenation refining step and a dewaxing step. [7] A method for producing a base oil according to any one of [1] to [6], further comprising a separation and recovery step for separating and recovering the extractant and oil after extracting and removing one or more substances selected from the dissolved and dispersed substances from the mixture obtained in the extraction step. [8] A method for producing a base oil according to [7], further comprising a refining step for washing the oil obtained in the separation and recovery step with a non-oil soluble light solvent. [9] A method for producing a base oil according to [7] or [8], further comprising an extractant regeneration step for regenerating the extractant obtained in the separation and recovery step.

[10] A method for producing a base oil according to [9], wherein the extractant comprises a regenerated extractant obtained in the extractant regeneration step.

[11] A base oil production apparatus comprising: an extraction apparatus for mixing waste oil and an extractant containing a non-oil-soluble deep eutectic solvent to extract one or more substances selected from the dissolved and dispersed products; a base oil production apparatus; and an additive apparatus for adding the waste oil treated by the extraction apparatus to the base oil production apparatus.

[12] A method for regenerating a used extractant, wherein the used extractant after the separation and recovery step in the base oil production method according to any one of [7] to

[10] is regenerated by vacuum distillation.

[0147] The present invention will be specifically described by the following examples, but the present invention is not limited to the following examples.

[0148] [Measurement Methods for Various Physical Properties] The measurement methods for various physical properties in this embodiment are as follows: (1) Kinematic viscosity: Measured in accordance with the "Test Method for Kinematic Viscosity of Petroleum Products" specified in JIS K2283:2000.

[0149] [Production Examples 1-54] The first and second components were placed in a beaker in the molar ratio shown in Table 3 and stirred with a stirring rod at room temperature (25°C). After liquefaction, the mixture was continued to stir with a stirrer at room temperature for 1 hour to produce a deep eutectic solvent. However, for mixtures that took time to become completely liquid, the mixture was heated to 40°C-50°C to accelerate liquefaction, and after the mixture became completely liquid, it was returned to room temperature and stirred at room temperature for 1 hour to produce a deep eutectic solvent.

[0150] Table 1 shows the three states (visually confirmed) and melting points (literature values) of the raw materials (first and second components) used in Production Examples 1 to 54 at room temperature. Table 2 shows the proton dissociation energy and proton affinity energy of the raw materials (first and second components) used in Production Examples 1 to 54. Note that all raw materials shown in Table 1 are nonionic substances.

[0151] [Calculation Method for Proton Dissociation Energy and Proton Affinity Energy of Starting Materials] Using Gaussian 16, a general-purpose quantum chemistry calculation program from Gaussian, Inc., structural optimization calculations were performed for hydrogen bond donors and hydrogen bond acceptors under the following conditions. Subsequently, the bond energy between the parent compound and protons (proton dissociation energy of the hydrogen bond donor and proton affinity energy of the hydrogen bond acceptor) was calculated. <Structural Optimization Calculation of Hydrogen Bond Donors and Hydrogen Bond Acceptors> All calculations were performed using DFT (Density Functional Theory). In this process, the basis functions used were 6-31+G** and the B3LYP functional, and Grimme's D3 dispersion force correction was used to optimize the structural parameters such as bonds, angles, and dihedral angles of each isolated molecule, assuming a vacuum state, so as to minimize the total energy of the molecule. <Bond Energy Calculation> Using Boys' Counterpoise method, the proton dissociation energy was calculated by dividing the parent compound into proton and non-proton parts, setting the proton to a charge of +1 and multiplicity of 1, and the non-proton parts to a charge of -1 and multiplicity of 1, so that the whole is electrically neutral. The proton affinity energy was calculated by adding a proton to the parent compound, optimizing the structure to have a total charge of +1 and multiplicity of 1, then dividing it into proton and non-proton parts, setting the proton to a charge of +1 and multiplicity of 1, and the non-proton parts to a charge of 0 and multiplicity of 1.

[0152]

[0153]

[0154] Table 3 shows the first and second components used in manufacturing examples 1 to 54, and their ratios (first component:second component (molar ratio)). Table 3 also shows the three states (visually confirmed) and kinematic viscosity of the manufactured deep eutectic solvent at room temperature. In Table 3, "first component" refers to the "hydrogen bond donor," and "second component" refers to the "hydrogen bond acceptor."

[0155] [Method for Calculating HSP Values] For each raw material, the HSP value was calculated using the "Hansen SP & QSPR Model," an add-on for the calculation software "Winmostar 9.4.11" (manufactured by Cross Ability Co., Ltd.). In production examples 1 to 54, the HSP value of the "first component" (hydrogen bond donor) was D ｄ The HSP value of the "second component" (hydrogen bond receptor) is D ａ Table 3 shows the HSP value D of the deep eutectic solvent represented by the following formula (1), where x:y is the molar ratio of the "first component" (hydrogen bond donor) to the "second component" (hydrogen bond acceptor). D = D ｄ x + D ａ ・y ... (1) However, in equation (1) above, x + y = 1.

[0156]

[0157] [Preparation of Sample Oils 1-4] Sample oils 1-4, to be used in the extraction experiment described later, were prepared as shown in Table 4. The numerical units of the composition in Table 4 are "mass%". The total amount of each sample oil composition is 100 mass%. Details of each component used in the preparation of the sample oil compositions shown in Table 4 are described below.

[0158]

[0159] <Mineral Oil> ・"Mineral Oil A": Kinematic viscosity at 40°C is 31 mm ２ The viscosity index is 105. • "Mineral oil B": kinematic viscosity at 40°C is 21 mm². ２ The viscosity index is 127, and the viscosity is s.

[0160] <Amine-based antioxidants> • "Amine-based antioxidant A": Dioctyldiphenylamine • "Amine-based antioxidant B": Octylphenyl-1-naphthylamine • "Amine-based antioxidant C": Butylphenyloctylphenylamine

[0161] <Phenol-based antioxidants> • "Phenol-based antioxidant A": 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid ester • "Phenol-based antioxidant B": 2,6-di-tert-butyl-p-cresol • "Phenol-based antioxidant C": Octyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate

[0162] <Phosphorus-based wear-resistant agents> • "Phosphorus-based wear-resistant agent A": Tricresyl phosphate • "Phosphorus-based wear-resistant agent B": Oleyl acid phosphate • "Phosphorus-based wear-resistant agent C": Methyl acid phosphate-dodecylamine salt

[0163] <Sulfur-based extreme pressure additives> ・"Sulfur-based extreme pressure additive A": di-tert-dodecylpentasulfide

[0164] <Metal deactivators> • "Metal deactivator": Polyhydric alcohol ester dodecenyl succinate • "Nitrogen-based metal deactivator": 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole

[0165] <Amid-based friction modifiers> • "Amid-based friction modifier A": Tetraethylenepentamine condensed isostearate • "Amid-based friction modifier B": Diethanol oleate

[0166] <Zinc Dialkyldithiophosphate> • "ZnDTP": Secondary dialkyldithiophosphate zinc (Zn content: 10.5% by mass, P content: 9.9% by mass)

[0167] <Calcium-based cleaning agent> • "Calcium-based cleaning agent": Overbasic calcium salicylate (base number: 224 mg KOH / g, calcium atom content: 7.6% by mass)

[0168] <Molybdenum dithiocarbamate> • "MoDTC": A dinuclear molybdenum dithiocarbamate represented by the following general formula (i2) (molybdenum atom content: 10.0 mass%, sulfur atom content: 11.5 mass%) In the above general formula (i2), R ｉ１ , R ｉ２ , R ｉ３ , and R ｉ４Each of these groups is independently selected from the isooctyl group (8 carbon atoms: short-chain substituent group) and the isotridecyl group (13 carbon atoms: long-chain substituent group), and the molar ratio of isooctyl groups to isotridecyl groups in the entire molecule of molybdenum dialkyldithiocarbamate is 50:50. ｉ１ and X ｉ２ X is a sulfur atom, ｉ３ and X ｉ４ It is an oxygen atom.

[0169] <Ashless Dispersants> • "Ashless Dispersant A": Polybutenyl succinimide • "Ashless Dispersant B": Boronated polybutenyl succinimide

[0170] [Preparation of Sample Oil 5] Copper and iron pieces were added to Sample Oil 1 as catalysts, and a dryTOST test was performed in accordance with JIS K 2514-2 (Test Method for Oxidation Stability of Turbine Oil) to forcibly degrade the test oil and obtain Sample Oil 5. The oxygen injection flow rate was 3.0 L / hr, the test temperature (oil temperature) was 120°C, and the test time was 1000 hours.

[0171] [Preparation of Sample Oil 6] Copper and iron pieces were added to Sample Oil 3 as catalysts, and an ISOT test was conducted in accordance with JIS K 2514-1:2013 (Internal Combustion Engine Lubrication Oxidation Stability Test) to forcibly degrade the test oil and obtain Sample Oil 6. The test temperature (oil temperature) was 150°C and the test time was 48 hours.

[0172] [Examples 1-10] Using the deep eutectic solvents produced from nonionic substances obtained in Production Examples 5, 6, 13, 15, 16, 25, 28, 29, 30, and 44 as extractants, the following extraction experiments were performed using sample oil 1, and the evaluations described below were carried out. The evaluation results are shown in Table 5.

[0173] <Extraction Experiment> The experiment was carried out in the following procedure: (1) 40 ml of sample oil 1 and 40 ml of the extraction solvent (deep eutectic solvent) for each production example were taken into a reaction vessel (200 ml flask). (2) The above mixture was stirred at 300 rpm for 30 minutes at room temperature. (3) After stirring was completed, it was left to stand overnight and sample oil 1 was separated. In Example 1, the separated extractant (deep eutectic solvent) was used in the extractant recovery and regeneration test described later. (4) The separated sample oil 1 was washed three times with 40 ml of methanol. (5) The remaining methanol was removed from the sample oil after methanol washing using an evaporator. (6) The properties of the obtained processed oil were evaluated by the method described later.

[0174] [Examples 11-15] Extraction experiments were conducted in the same manner as in Examples 1-10, except that sample oil 2 was used, with the deep eutectic solvent produced from the nonionic substance obtained in Production Examples 5, 6, 13, 30, and 44 as the extractant, and the evaluation described below was carried out. The evaluation results are shown in Table 6.

[0175] [Examples 16-20] Using the deep eutectic solvent produced from the nonionic substance obtained in Production Examples 5, 6, 13, 30, and 44 as the extractant, the following extraction experiments were performed using sample oil 3, and the evaluation described below was carried out. The evaluation results are shown in Table 7. <Extraction Experiment> The experiment was carried out in the following procedure. (1) 40 ml of sample oil 3 and 40 ml of the extraction solvent (deep eutectic solvent) from the above production example were taken into a reaction vessel (200 ml flask). (2) The above mixture was stirred at 300 rpm at 50°C for 30 minutes. (3) After stirring was completed, it was left to stand at 50°C for 1 hour, then left to stand at room temperature overnight, and the sample oil 3 was separated. (4) The separated sample oil 3 was washed three times with 30 ml of methanol. (5) The remaining methanol was removed from the sample oil 3 after methanol washing using an evaporator. (6) The properties of the obtained processed oil were evaluated by the following method.

[0176] [Examples 21-25] Using the deep eutectic solvent produced from the nonionic substance obtained in Production Examples 5, 6, 13, 30, and 44 as the extractant, the following extraction experiments were performed using sample oil 4, and the evaluation described below was carried out. The evaluation results are shown in Table 8. <Extraction Experiment> The experiment was carried out in the following procedure. (1) 40 ml of sample oil 4 and 40 ml of the extraction solvent (deep eutectic solvent) from the above production example were taken into a reaction vessel (200 ml flask). (2) The above mixture was stirred at 300 rpm at 50°C for 30 minutes. (3) After stirring was completed, it was allowed to stand until it returned to room temperature, and then the sample oil 4 was separated by centrifugation at a centrifugal force of 2600 G for 5 minutes using a centrifuge. (4) The separated sample oil 4 was washed three times with 30 ml of methanol. (5) The remaining methanol was removed from the sample oil 4 after methanol washing using an evaporator. (6) The properties of the obtained processed oil were evaluated by the following method.

[0177] [Examples 26-27] Extraction experiments were conducted in the same manner as in Examples 1-10, except that sample oil 5 was used as the extractant, with the deep eutectic solvent produced from the nonionic substance obtained in Production Examples 5 and 44 being used. The evaluation described below was then carried out. The evaluation results are shown in Table 9.

[0178] [Examples 28-30] Extraction experiments were conducted in the same manner as in Examples 1-10, except that sample oil 6 was used as the extractant, with the deep eutectic solvent produced from the nonionic substance obtained in Production Examples 5, 6, and 44 being used. The evaluation described below was then carried out. The evaluation results are shown in Table 10.

[0179] [Example 31] The following extraction experiment was performed using sample oil 1, and the evaluation described below was carried out. The evaluation results are shown in Table 11.

[0180] <Extraction Experiment> The experiment was carried out in the following procedure: (1) 40 ml of sample oil 1 was taken into a reaction vessel (200 ml flask). (2) Indole (18.5 g) was added to sample oil 1 as the first agent, and the mixture was stirred at 300 rpm for 15 minutes at room temperature to obtain a suspension. (3) Camphor (10.3 g) was added to the above suspension as the second agent, and the mixture was stirred at 300 rpm for 1 hour at room temperature. The suspension became a two-liquid phase. (4) After stirring, the mixture was left to stand overnight at room temperature, and sample oil 1 was separated. (5) The separated sample oil 1 was washed three times with 40 ml of methanol. (6) After methanol washing, the remaining methanol was removed from sample oil 1 using an evaporator. (7) The properties of the obtained processed oil were evaluated by the following method.

[0181] [Example 32] An extraction experiment was conducted in the same manner as in Example 31, except that thymol (18.0 g) was used instead of indole and coumarin (11.7 g) was used instead of camphor, and the evaluation described below was carried out. The evaluation results are shown in Table 11.

[0182] [Example 33] Using the deep eutectic solvent produced from the nonionic substance obtained in Production Example 5 as the extractant, the following extraction experiment was performed using sample oil 3, and the evaluation described below was carried out. The evaluation results are shown in Table 12.

[0183] <Extraction Experiment> The experiment was carried out in the following procedure: (1) 50 ml of sample oil 3 and 30 ml of the extraction solvent (deep eutectic solvent) from the above production example were placed in a reaction vessel (200 ml flask). (2) The above mixture was stirred at 300 rpm at 50°C for 30 minutes. (3) After stirring was completed, it was left to stand at 50°C for 1 hour, then left to stand overnight at room temperature to separate the sample oil 3. (4) The separated sample oil 3 was repeated using steps (1) to (3). (5) The separated sample oil 3 was washed three times with 30 ml of methanol. (6) The remaining methanol was removed from the sample oil 3 after methanol washing using an evaporator. (7) The properties of the obtained processed oil were evaluated by the following method.

[0184] [Example 34] An extraction experiment was conducted in the same manner as in Example 33, except that 50 ml of sample oil 6 was used instead of sample oil 3, and the evaluation described below was carried out. The evaluation results are shown in Table 13.

[0185] [Comparative Examples 1, 4, 5, 8, 10, 12] The following extraction experiments were conducted using sample oils 1 to 6 with methanol as the extractant, and the evaluations described below were performed. The evaluation results are shown in Tables 5 to 10.

[0186] <Extraction Experiment> The experiment was carried out according to the following procedure: (1) 40 ml of sample oil and 40 ml of methanol were taken into a reaction vessel (200 ml flask). (2) The above mixture was stirred at 300 rpm for 30 minutes at room temperature. (3) After stirring was completed, it was left to stand overnight and the sample oil was separated. (4) The separated sample oil was washed twice with 40 ml of methanol. (5) The remaining methanol was removed from the sample oil after methanol washing using an evaporator. (6) The properties of the obtained processed oil were evaluated by the following method.

[0187] [Comparative Examples 2, 6, 9, 11] Using furfural as an extractant, the following extraction experiments were conducted using sample oils 1, 3, 4, and 5, and the evaluations described below were performed. The evaluation results are shown in Tables 5, 7, 8, and 9.

[0188] <Extraction Experiment> The experiment was carried out according to the following procedure: (1) 40 ml of sample oil and 40 ml of furfural were taken into a reaction vessel (200 ml flask). (2) The above mixture was stirred at 300 rpm for 30 minutes at room temperature. (3) After stirring, it was left to stand overnight and the sample oil was separated. (4) The separated sample oil was washed twice with 40 ml of methanol. (5) The remaining methanol was removed from the sample oil after methanol washing using an evaporator. (6) The properties of the obtained treated oil were evaluated by the following method.

[0189] [Comparative Examples 3 and 7] Using an ionic liquid (1-butyl-1-methylpyrrolidinium / bis(trifluoromethanesulfonyl)imide) as an extractant, the following extraction experiments were conducted using sample oils 1 and 3, and the evaluations described below were performed. The evaluation results are shown in Tables 5 and 7.

[0190] <Extraction Experiment> (1) 40 ml of sample oil and 40 ml of ionic liquid (1-butyl-1-methylpyrrolidinium / bis(trifluoromethanesulfonyl)imide) were taken into a reaction vessel (200 ml flask). (2) The above mixture was stirred at 300 rpm for 30 minutes at room temperature. (3) After stirring, it was left to stand overnight and the sample oil was separated. (4) The separated sample oil was washed twice with 40 ml of methanol. (5) The remaining methanol was removed from the sample oil after methanol washing using an evaporator. (6) The properties of the obtained processed oil were evaluated by the following method.

[0191] <Elemental Analysis> The calcium, zinc, molybdenum, boron, and phosphorus content of each sample oil composition before and after the extraction experiment was measured using an ICP plasma emission spectrometer. The sulfur content was measured according to JIS K 2541-6:2013 (Crude oil and petroleum products - Test methods for sulfur content - Part 6: Ultraviolet fluorescence method) if it was less than 500 ppm by mass on a total basis of the sample oil composition, and according to ASTM D6443 (Fluorescent X-ray method) if it was 500 ppm by mass or more on a total basis of the sample oil composition. The nitrogen content was measured according to JIS K 2609:1998 (Crude oil and petroleum products - Test methods for nitrogen content - Chemiluminescence method). The ratio (mass ratio) of the content of each element in the sample oil composition after the extraction experiment to the content in the sample oil composition before the extraction experiment was calculated and evaluated based on the following criteria. (1) Phosphorus - Evaluation A: 5% or less, Evaluation B: More than 5% and 15% or less, Evaluation C: More than 15% (2) Sulfur - Evaluation A: 10% or less, Evaluation B: More than 10% and 20% or less, Evaluation C: More than 20% (3) Nitrogen - Evaluation A: 10% or less, Evaluation B: More than 10% and 25% or less, Evaluation C: More than 25% (4) Calcium - Evaluation A: 35% or less, Evaluation B: More than 35% and 70% or less, Evaluation C: More than 70% (5) Zinc - Evaluation A: 15% or less, Evaluation B: More than 15% and 30% or less, Evaluation C: More than 30% (6) Molybdenum - Evaluation A: 10% or less, Evaluation B: More than 10% and 15% or less, Evaluation C: More than 15% (7) Boron - Evaluation A: 5% or less, Evaluation B: More than 5% and 15% or less, Evaluation C: More than 15% In this example, evaluations A and B were considered acceptable. The results are shown in Tables 5-13.

[0192] <Acid Value> The acid value of each sample oil composition before and after the extraction experiment was measured in accordance with JIS K2501 2003 (indicator photometric method). The results are shown in Tables 5 to 13.

[0193] <Base Number> The base number of each sample oil composition before and after the extraction experiment was measured by potentiometric titration (hydrochloric acid method) in accordance with JIS K2501 2003. The results are shown in Tables 5 to 13.

[0194] <Infrared Absorption (IR) Spectra> Infrared absorption (IR) spectra were measured using the liquid film method in accordance with JIS K0117. Using a KBr-fixed cell with a path length of 0.1 mm, each sample oil composition before and after the extraction experiment was evaluated using samples diluted in mineral oil A or B, respectively. The sample oil compositions used for measurement were sample oils 1-3 before the extraction test and the sample oils after the extraction test of Examples 9, 14, 20 and Comparative Examples 1, 4, 5. The results are shown in Figures 1-9. • Instrument name: FTIR-6200 (manufactured by JASCO Corporation) • Resolution: 4 cm －１ • Number of measurements: 16 • Measurement temperature: Room temperature (Figure 1, before extraction experiment): 1600 cm² －１ Nearby, 1510 cm －１ Nearby, and 970 cm －１ Peaks were observed in the vicinity, which are presumed to originate from (C=O)-N, C=C, and P-O-H, respectively. In Figure 2, each peak remains large, whereas in Figure 3, each peak is smaller, indicating that additives in the lubricating oil composition have been extracted. Also, in Figure 4 (before the extraction experiment), at 3650 cm⁻¹ －１ Nearby, 1730 cm －１ Nearby, 1600 cm －１ Nearby, 1510 cm －１ Nearby, and between 1280 and 1200 cm －１ and 970 cm －１Peaks were observed in the vicinity, which are presumed to originate from Ph-O-H, (C=O)-O, (C=O)-N, C=C, and P-O-H, respectively. In Figure 5, each peak remains large, whereas in Figure 6, each peak is smaller, indicating that additives in the lubricating oil composition have been extracted. Also, in Figure 7 (before the extraction experiment), at 3650 cm⁻¹ －１ Nearby, 1740 cm －１ Nearby, 1600 cm －１ Nearby, 1520 cm －１ Nearby, and 980 cm －１ Peaks were observed in the vicinity, which are presumed to originate from Ph-O-H, (C=O)-O, (C=O)-N, C=C, and P-O, respectively. In Figure 8, each peak remains large, whereas in Figure 9, each peak is smaller, indicating that the additives in the lubricating oil composition have been extracted.

[0195]

[0196]

[0197]

[0198]

[0199]

[0200]

[0201]

[0202]

[0203]

[0204] From Tables 5 to 10, the following can be seen. As shown in Examples 1 to 30, when a deep eutectic solvent produced from a nonionic substance is used as an extractant, the content of each element in the lubricating oil composition is greatly reduced, and the acid value and base value are greatly reduced, indicating excellent extraction performance for substances such as additives and degradation products in the lubricating oil composition. In contrast, as shown in Comparative Examples 1 to 12, when general extraction solvents such as methanol, furfural, or ionic liquids are used, the decrease in the content of each element in the lubricating oil composition, as well as the decrease in the acid value and base value, is lower compared to Examples 1 to 30, indicating inferior extraction performance. Furthermore, from Table 11, the following can be seen. As shown in Examples 31 and 32, even when the hydrogen bond donor and hydrogen bond acceptor are mixed separately with the lubricating oil composition, the same extraction performance as in Examples 1 to 10 can be achieved. Furthermore, from Tables 12 and 13, the following can be seen. As shown in Examples 33 and 34, it can be seen that even with a small amount of extractant used, extraction performance equivalent to or better than that of Examples 16 and 28 can be achieved by repeatedly performing the extraction operation.

[0205] [Extractant Recovery and Regeneration Test] The extractant recovery and regeneration test was conducted according to the following procedure.

[0206] <Example 1 of Extractant Recovery and Regeneration> A total of 200 g of extractants (deep eutectic solvent containing extracted oil degradation products, impurities, and residual additives, etc.) separated and recovered in Examples 1, 11, 16, 26, and 28 were subjected to vacuum distillation under the following conditions. This yielded 57 g of camphor, a nonionic hydrogen bond acceptor (vacuum distillation conditions: 80-110°C, 10 mmHg), and 124 g of indole, a nonionic hydrogen bond donor (vacuum distillation conditions: 100-120°C, 2.5 mmHg). Of this, 19 g of residue, including oil degradation products, impurities, and residual additives, was disposed of as waste.

[0207] <Example 2 of Extractant Recovery and Recycling> A total of 200 g of the extractant (deep eutectic solvent containing extracted oil degradation products, impurities, and residual additives, etc.) separated and recovered in Examples 10, 15, 20, 27, and 30 was subjected to vacuum distillation under the following conditions. This yielded 119 g of thymol, a nonionic hydrogen bond donor (vacuum distillation conditions: 90-120°C, 5 mmHg), and 65 g of coumarin, a nonionic hydrogen bond acceptor (vacuum distillation conditions: 130-160°C, 2.5 mmHg). Of this, 16 g of residue, including oil degradation products, impurities, and residual additives, was disposed of as waste.

[0208] [Example 35] Using the indole and camphor obtained in [Example 1 of Extractant Recovery and Regeneration], the deep eutectic solvent was regenerated in the same manner as in Production Example 5 in Table 3. Using this regenerated deep eutectic solvent as the extractant, an extraction experiment similar to that in Example 1 was performed and evaluated. The evaluation results are shown in Table 14.

[0209] [Example 36] Using the thymol and coumarin obtained in [Example 2 of Extractant Recovery and Regeneration], the deep eutectic solvent was regenerated in the same manner as in Production Example 44 in Table 3. Using this regenerated deep eutectic solvent as an extractant, an extraction experiment similar to that in Example 10 was performed and evaluated. The evaluation results are shown in Table 14.

[0210] <Elemental Analysis> The nitrogen and phosphorus content of each sample oil composition before and after the extraction experiment was measured using an ICP plasma emission spectrometer. The nitrogen content was measured in accordance with JIS K 2609:1998 (Crude oil and petroleum products - Nitrogen content test method - Chemiluminescence method). The ratio (mass ratio) of the content of each element in the sample oil composition after the extraction experiment to the content in the sample oil composition before the extraction experiment was calculated and evaluated based on the following criteria: - Evaluation A: 10% or less, or elemental analysis below the detection limit - Evaluation B: Greater than 10% and 25% or less - Evaluation C: Greater than 25% In this example, evaluations A and B were considered acceptable. The results are shown in Table 14.

[0211] <Acid Value, Base Value> The acid value and base value of each sample oil composition before and after the extraction experiment were measured using the same method as in Examples 1 to 34 and Comparative Examples 1 to 12 described above. The results are shown in Table 14.

[0212]

[0213] From Table 14 and Examples 1 and 2 of extractant recovery and regeneration, the following can be seen. As shown in Examples 35 and 36, when the recovered and regenerated deep eutectic solvent is used as an extractant, the content of each element in the lubricating oil composition is greatly reduced, and the acid value and base value are also greatly reduced, similar to Examples 1 and 10 in Table 5, where a new deep eutectic solvent is used as an extractant. Therefore, it is clear that the recovered and regenerated deep eutectic solvent also acts effectively as an extractant. Furthermore, in Examples 1 and 2 of extractant recovery and regeneration, the residue disposed of as waste containing oil degradation products, impurities, and residual additives was approximately 10% of the waste oil used, indicating its effectiveness in reducing the amount of waste treated.

[0214] [Waste Oil Recycling Test] A waste oil recycling test was conducted according to the following procedure.

[0215] [Sample Oil 7] Commercially available waste oil (recycled heavy oil) was used. The acid value, base value, and elemental analysis values ​​of the waste oil are as shown in Table 15.

[0216] [Preparation of Sample Oil 8] The waste oil from Sample Oil 7 was distilled under reduced pressure, and the fraction at 200-280°C / 2.4 mmHg was used. The acid value, base value, and elemental analysis values ​​of the distilled component are as shown in Table 16.

[0217] [Examples 37-41] Using deep eutectic solvents prepared from nonionic substances obtained in Production Examples 5 (indole / camphor), 6 (indole / coumarin), 13 (indole / thymol), 16 (N-phenyl-1-naphthylamine / coumarin), and 44 (thymol / coumarin) as extractants, the following extraction experiments were conducted using sample oil 7, and the evaluations described below were performed. The evaluation results are shown in Table 15.

[0218] <Extraction Experiment> The experiment was carried out according to the following procedure: (1) 50 ml of sample oil 7 and 100 ml of the extractant (deep eutectic solvent) for each production example were placed in a reaction vessel (200 ml flask). The mixture was stirred at 300 rpm for 30 minutes at room temperature. (2) After stirring, it was left to stand overnight and the sample oil 7 was separated. (3) The separated sample oil 7 was washed three times with 50 ml of methanol. After methanol washing, the remaining methanol was removed from the sample oil using an evaporator. (4) The properties of the obtained processed oil were evaluated by the method described below.

[0219] [Examples 42-44] Extraction experiments were conducted in the same manner as in Examples 37-41, except that the deep eutectic solvent produced from the nonionic substance obtained in Production Examples 5, 6, and 44 was used as the extractant, and sample oil 8 was used. The results of the evaluation are shown in Table 16.

[0220] [Comparative Examples 13 and 15] Using methanol as an extractant, the following extraction experiments were conducted using sample oils 7 and 8, and the evaluations described below were performed. The evaluation results are shown in Tables 15 and 16.

[0221] <Extraction Experiment> The experiment was carried out according to the following procedure: (1) 50 ml of sample oil and 100 ml of methanol were taken into a reaction vessel (200 ml flask). (2) The above mixture was stirred at 300 rpm for 30 minutes at room temperature. (3) After stirring, it was left to stand overnight and the sample oil was separated. (4) The separated sample oil was washed three times with 50 ml of methanol. (5) The remaining methanol was removed from the sample oil after methanol washing using an evaporator. (6) The properties of the obtained processed oil were evaluated by the following method.

[0222] [Comparative Examples 14 and 16] Using furfural as an extractant, the following extraction experiments were conducted using sample oils 7 and 8, and the evaluations described below were performed. The evaluation results are shown in Tables 15 and 16.

[0223] <Extraction Experiment> The experiment was carried out according to the following procedure: (1) 50 ml of sample oil and 100 ml of furfural were taken into a reaction vessel (200 ml flask). (2) The above mixture was stirred at room temperature at 300 rpm for 30 minutes. (3) After stirring, it was left to stand overnight and the sample oil was separated. (4) The separated sample oil was washed three times with 50 ml of methanol. (5) The remaining methanol was removed from the sample oil after methanol washing using an evaporator. (6) The properties of the obtained processed oil were evaluated by the following method.

[0224] <Elemental Analysis> The calcium, copper, iron, zinc, molybdenum, potassium, sodium, magnesium, silicon, boron, and phosphorus content of each sample oil composition before and after the extraction experiment was measured using an ICP plasma emission spectrometer. The sulfur content was measured according to JIS K 2541-6:2013 (Crude oil and petroleum products - Test methods for sulfur content - Part 6: Ultraviolet fluorescence method) if it was less than 500 ppm by mass on a total basis of the sample oil composition, and according to ASTM D6443 (Fluorescent X-ray method) if it was 500 ppm by mass or more on a total basis of the sample oil composition. The nitrogen content was measured according to JIS K 2609:1998 (Crude oil and petroleum products - Test methods for nitrogen content - Chemiluminescence method). Chlorine content was measured in accordance with JPI-5S-64-2002 (Petroleum Products - Chlorine Content Test Method - Microcoulometric Titration Method). The ratio (mass ratio) of the content of each element in the sample oil composition after the extraction experiment to the content in the sample oil composition before the extraction experiment was calculated. For Examples 37 to 41 and Comparative Examples 13 and 14, the following criteria were used for evaluation: Evaluation A: 40% or less, or elemental analysis below the detection limit; Evaluation B: greater than 40% and 70% or less; Evaluation C: greater than 70%. The results are shown in Table 15. For Examples 42 to 44 and Comparative Examples 15 and 16, the following criteria were used for evaluation: Evaluation A: 10% or less, or elemental analysis below the detection limit; Evaluation B: greater than 10% and 20% or less; Evaluation C: greater than 20%. The results are shown in Table 16. In these examples, evaluations A and B were considered acceptable.

[0225] <Acid Value, Base Value> The acid value and base value of each sample oil composition before and after the extraction experiment were measured using the same method as in Examples 1 to 34 and Comparative Examples 1 to 12 described above. The results are shown in Tables 15 and 16.

[0226] <Infrared Absorption (IR) Spectra> Infrared absorption (IR) spectra were measured using the liquid film method in accordance with JIS K0117. Using a KBr-fixed cell with a path length of 0.1 mm, each sample oil composition before and after the extraction experiment was evaluated using samples diluted in mineral oil A or B, respectively. The sample oil compositions used for measurement were sample oils 7 and 8 before the extraction test, and the sample oils after the extraction test of Examples 37 and 42 and Comparative Examples 13 and 15. The results are shown in Figures 10 to 15. • Instrument name: FTIR-6200 (manufactured by JASCO Corporation) • Resolution: 4 cm －１ • Number of measurements: 16 • Measurement temperature: Room temperature (Figure 10, before extraction experiment): 1740 cm² －１ Nearby, 1600 cm －１ Peaks were observed in the vicinity, which are presumed to originate from (C=O)-O and (C=O)-N, respectively. Also, the range was 3600-2600 cm. －１ and 1500-800cm －１ The spectrum is broad overall (peak-shaped) in the waste oil, suggesting that the absorption of various molecular species overlaps, and the uneven concentration of components suppresses molecular motion and vibration, resulting in the formation of broad peaks. In Figure 11, each peak remains large, whereas in Figure 12, each peak becomes smaller, and the spectrum is generally flat, indicating that additives and impurities in the waste oil have been extracted. Also, in Figure 13 (before the extraction experiment), at 1740 cm⁻¹ －１ Nearby, 1600 cm －１ Nearby, 1120 cm －１ Peaks were observed in the vicinity, which are presumed to originate from (C=O)-O, (C=O)-N, and C-O, respectively. In Figure 14, each peak remains, whereas in Figure 15, each peak has disappeared or become smaller, indicating that additives and impurities in the waste oil have been extracted.

[0227]

[0228] Table 15 shows the following: As shown in Examples 37 to 41, when a deep eutectic solvent produced from a nonionic substance is used as an extractant, the content of each element in the waste oil (recovered heavy oil) is greatly reduced, and the acid value and base value are also greatly reduced, indicating excellent extraction performance for substances such as additives and degradation products in the waste oil (recovered heavy oil). In contrast, as shown in Comparative Examples 13 and 14, when methanol or furfural, which are common extraction solvents, are used, the content of each element in the waste oil, as well as the rate of reduction in acid value and base value, is lower compared to the examples, indicating inferior extraction performance.

[0229]

[0230] Furthermore, the following can be seen from Table 16. As shown in Examples 42 to 44, when a deep eutectic solvent produced from a nonionic substance is used as an extractant, the content of each element in the fraction obtained by vacuum distillation of waste oil is greatly reduced, and the acid value and base value are greatly reduced. This indicates that the extraction performance of substances such as additives and degradation products in the fraction obtained by vacuum distillation of waste oil is excellent. These results show that when a pretreatment step by distillation is combined with an extraction treatment method using a deep eutectic solvent produced from a nonionic substance as an extractant, the content of almost all elements in the recovered oil is greatly reduced, and the acid value and base value are greatly reduced, indicating excellent waste oil recycling performance. In contrast, as shown in Comparative Examples 15 and 16, when methanol or furfural, which are common extraction solvents, are used, the content of each element in the recovered oil, as well as the rate of reduction in acid value and base value, is lower compared to the examples, indicating inferior extraction performance.

[0231] S0: Waste oil recovery process S10: Pretreatment process S1: Extractant manufacturing process S2: Extraction process S3: Separation and recovery process S4: Extractant regeneration process S5: Refining process S100: Waste oil treatment oil addition process T: Base oil manufacturing process T1: Vacuum distillation process T2: Hydrocracking process T3: Dewaxing process T4: Hydrofinishing process E0: Waste oil storage facility E1: Extractant manufacturing facility E2: Extraction facility E3: Separation and recovery facility E4: Extractant regeneration facility E5: Refining facility E6: Addition facility E10: Pretreatment facility ET: Base oil manufacturing facility ET1: Vacuum distillation facility ET2: Hydrocracking facility ET3: Dewaxing facility ET4: Hydrofinishing facility A: Addition route A B: Addition route B 10: Waste oil 100: Pre-treated waste oil 11: Extractant 12: Extractant component 13: Oil component 14: Recycled extractant 15: Extractant remaining in the oil component 16: Waste oil treatment oil 17: Waste containing one or more substances selected from dissolved and dispersed materials 20: Raw material oil 21: Base oil

Claims

1. A method for producing a base oil, comprising: an extraction step of mixing waste oil with an extractant containing a non-oil-soluble deep eutectic solvent to extract one or more substances selected from the dissolved and dispersed products; and a waste oil treatment step of adding the waste oil treated through the extraction step to a base oil production step.

2. The method for producing a base oil according to claim 1, wherein in the extraction step, the extractant is mixed with the waste oil so that the ratio of (extractant) / (waste oil) by volume is 0.1 to 5.

0.

3. A method for producing a base oil according to claim 1 or 2, comprising an extractant production step of producing an extractant containing a non-oil-soluble deep eutectic solvent which is a mixed product of one or more nonionic hydrogen bond donors selected from nonionic hydrogen bond acceptors, prior to the extraction step, and using the obtained extractant in the extraction step.

4. The method for producing a base oil according to claim 3, wherein the hydrogen bond donor has a proton dissociation energy of -400 kcal / mol or more, and the hydrogen bond acceptor has a proton affinity energy of -180 kcal / mol or less.

5. The HSP value of the hydrogen bond donor is D ｄ , the HSP value of the hydrogen bond receptor is D ａ When the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor in the extractant is x:y, the HSP value D of the deep eutectic solvent, represented by the following formula (1), is 17 MPa. ０．５ The method for producing a base oil according to claim 3 or 4, as described above. D = D ｄ x + D ａ ・y ... (1) However, in equation (1) above, x + y = 1.

6. A method for producing a base oil according to any one of claims 1 to 5, wherein the base oil production process for adding the waste oil treatment oil includes at least one of a hydrogenation refining step and a dewaxing step.

7. A method for producing a base oil according to any one of claims 1 to 6, further comprising a separation and recovery step of separating and recovering the extractant and oil after extracting and removing one or more substances selected from the dissolved and dispersed materials from the mixture obtained in the extraction step.

8. The method for producing a base oil according to claim 7, further comprising a refining step of washing the oil obtained in the separation and recovery step with a non-oil-soluble light solvent.

9. A method for producing a base oil according to claim 7 or 8, further comprising an extractant regeneration step for regenerating the extractant obtained in the separation and recovery step.

10. The method for producing a base oil according to claim 9, wherein the extractant includes a regenerated extractant obtained by the extractant regeneration step.

11. A base oil manufacturing apparatus comprising: an extraction facility for mixing waste oil with an extractant containing a non-oil-soluble deep eutectic solvent to extract one or more substances selected from the dissolved and dispersed products; a base oil manufacturing facility; and an additive facility for adding the waste oil treated by the extraction facility to the base oil manufacturing facility.

12. A method for regenerating used extractants, comprising regenerating the used extractant after the separation and recovery step in the method for producing a base oil according to any one of claims 7 to 10 by vacuum distillation.

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