Synthetic ether-based lubricating oil and method for producing and use thereof

Abstract

The application discloses a synthetic ether type base oil and a preparation method and application thereof, and a structural formula of the synthetic ether type base oil is shown as formula V. The synthetic ether type base oil provided by the application has higher tolerance to water content in lubricating oil, higher emulsion resistance as base oil of lubricating oil, can change the lipophilic-hydrophilic balance of original emulsion, can be separated faster after mixing with water, and allows higher dissolved water content in lubricating oil without abnormal phenomena such as emulsification, turbidity and reduced transparency. Meanwhile, the base oil does not contain polyoxyethylene chain segments, polyoxypropylene chain segments and hydroxyl groups with high hydrophilicity in the molecular structure, has higher compatibility with common base oils such as mineral oil, and is especially suitable for being applied to lubricating oil products such as steam turbine oil, marine lubricating oil, anti-wear hydraulic oil, compressor oil, oil film oil and gear oil.

Description

Technical Field

[0001] This invention relates to the field of lubricant preparation technology, and in particular to a synthetic ether-type base oil and its preparation method. Background Technology

[0002] Lubricating oil, as a liquid lubricant, is mainly used in various types of machinery to reduce friction and protect the machinery and machined parts. It plays an important role in lubrication, cooling, rust prevention, cleaning, sealing, and buffering. my country has formulated a classification standard for lubricating oils based on international standards. Lubricating oils are divided into 19 categories according to their application, the most commonly used of which are total loss system oils, hydraulic oils, gear oils, internal combustion engine oils, and rust preventives.

[0003] Lubricating oils generally consist of two parts: base oil and additives. Base oil is the main component of lubricating oil, determining its basic properties. Base oils are mainly divided into two categories: mineral base oils and synthetic base oils. Fully synthetic base oils are a type of high-quality lubricating oil raw material. Compared with mineral oils, they have better low-temperature fluidity, higher viscosity index, better oxidation resistance and thermal stability, higher shear resistance under heavy mechanical shear stress, and lower volatility. They also have advantages such as being green and energy-saving, safe and non-toxic, and having lower overall operating costs.

[0004] Lubricating oils are prone to mixing with water during use, forming emulsions. This is especially true for turbine oils, hydraulic oils, industrial gear oils, and marine system lubricating oils, which inevitably contain cooling water, condensate, and other moisture. Before the moisture content exceeds the lubricating oil's maximum allowable dissolved water content and reaches its water absorption saturation point, the presence of water in the lubricating oil will not be apparent, such as emulsification, turbidity, or reduced transparency. However, as the moisture content increases further, exceeding the water absorption saturation point, the lubricating oil undergoes emulsification, leading to deterioration in lubrication performance, especially when containing surface-active additives. If the lubricating oil itself has poor anti-emulsification properties and cannot quickly separate oil and water, a stable oil film cannot form between the contact surfaces of friction components, causing excessive wear and even chemical corrosion of mechanical components, thus affecting production and safety. Therefore, the quality indicators for these types of oils must require them to have good oil-water separation capabilities; this oil-water separation capability is commonly referred to as the oil's anti-emulsification property.

[0005] Currently, lubricating oils are often used in applications where a small amount of water vapor is mixed in, forming a water-in-oil (w / o) emulsion that is more difficult to demulsify. Existing technologies address the poor demulsibility of lubricating oils by adding demulsifiers and adjusting the overall lubricating oil formulation. However, this often results in other lubricating oil properties failing to meet standards and making it difficult to cope with the complex and varied conditions encountered in actual use. In particular, the most widely used and effective demulsifier in my country is ethylene oxide-propylene oxide copolymer, whose polyoxyethylene and polyoxypropylene segments are hydrophilic, leading to drawbacks such as immiscibility with mineral oil products. Furthermore, polyol ester base oils contain ester bonds, which are prone to hydrolysis at high water content. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a synthetic ether-type base oil and its preparation method. This synthetic ether-type base oil, while ensuring excellent performance, also has excellent demulsification ability, does not require the use of additional demulsifiers, has high tolerance to water content in lubricating oil, and will not undergo hydrolysis.

[0007] To achieve the above and other related objectives, the present invention is obtained through the following technical solution.

[0008] This invention first discloses a synthetic ether-type base oil, wherein the compound in the synthetic ether-type base oil has the structural formula shown in Formula V.

[0009]

[0010] Wherein, R0 is a straight-chain alkyl or ether group with 1 to 30 carbon atoms, a branched non-cyclic alkyl group, a cyclic alkyl group without side chains, or a cyclic alkyl group with side chains; R1 is a straight-chain alkyl group with 1 to 12 carbon atoms; R2 is a straight-chain alkyl group with 1 to 4 carbon atoms; and n is an integer ≥2.

[0011] Preferably, R0 is a straight-chain alkyl or ether group with 5 to 15 carbon atoms, a branched non-cyclic alkyl group, or a cyclic alkyl group with side chains. For example, the number of carbon atoms in R0 can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15.

[0012] Preferably, R1 is a straight-chain alkyl group with 2 to 5 carbon atoms, such as R1 having 2, 3, 4, or 5 carbon atoms.

[0013] Preferably, R2 is a straight-chain alkyl group with 1 to 2 carbon atoms, such as R2 having 1 or 2 carbon atoms.

[0014] Preferably, n is 2, 3, 4, 5 or 6.

[0015] Preferably, the compound of formula V comprises:

[0016]

[0017]

[0018] Preferably, the compound of formula IV comprises:

[0019]

[0020] Preferably, the pour point of the synthetic ether-type base oil is not higher than -30°C. More preferably, the pour point of the synthetic ether-type base oil is -70 to -30°C, such as -70°C, -65°C, -60°C, -55°C, -50°C, -45°C, -40°C, -35°C, or -30°C. Even more preferably, the pour point of the synthetic ether-type base oil is -63 to -37°C.

[0021] Preferably, the viscosity index of the synthetic ether-type base oil is not less than 130. More preferably, the viscosity index of the synthetic ether-type base oil is 130 to 180, such as 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, or 180.

[0022] Preferably, the synthetic ether-type base oil has a kinematic viscosity of 5.0–8.0 mm at 40°C. 2 / s, such as 5.0mm 2 / s, 5.5mm 2 / s, 6.0mm 2 / s, 6.5mm 2 / s, 7.0mm 2 / s, 7.5mm 2 / s, 8.0mm 2 / s.

[0023] Preferably, the synthetic ether-type base oil has a kinematic viscosity of 1.5–3.5 mm at 100°C. 2 / s, such as 1.5mm 2 / s, 1.6mm 2 / s, 1.7mm 2 / s, 1.8mm 2 / s, 1.9mm 2 / s, 2.0mm 2 / s, 2.1mm 2 / s, 2.2mm 2 / s, 2.3mm 2 / s, 2.4mm 2 / s, 2.5mm 2 / s, 2.6mm 2 / s, 2.7mm 2 / s, 2.8mm2 / s, 2.9mm 2 / s, 3.0mm 2 / s, 3.1mm 2 / s, 3.2mm 2 / s, 3.3mm 2 / s, 3.4mm 2 / s, 3.5mm 2 / s. More preferably, the kinematic viscosity of the synthetic ether-type base oil at 100°C is 2.0–3.0 mm. 2 / s. More preferably, the kinematic viscosity of the synthetic ether-type base oil at 100°C is 2.0–2.5 mm. 2 / s.

[0024] This invention also discloses a method for preparing synthetic ether-type base oils, comprising the following steps:

[0025] 1) Compound I undergoes a sulfonation reaction to yield compound II, and the reaction route is as follows:

[0026]

[0027] 2) Compound II undergoes a bromine substitution reaction to yield compound III. The reaction route is as follows:

[0028]

[0029] 3) Compound III and compound IV undergo a substitution reaction to prepare a synthetic ether-type base oil. The reaction route is as follows:

[0030]

[0031] Preferably, when the structural formula of compound V is V-1, its preparation method is as follows:

[0032] 1) Compound I-1 undergoes sulfonation to yield compound II-1, and the reaction route is as follows:

[0033]

[0034] 2) Compound II-1 undergoes a bromine substitution reaction to yield compound III-1. The reaction route is as follows:

[0035]

[0036] 3) Compound III-1 and compound IV-1 undergo a substitution reaction to obtain compound V-1. The reaction route is as follows:

[0037]

[0038] Preferably, when the structural formula of compound V is V-2, its preparation method is as follows:

[0039] 1) Compound I-1 undergoes sulfonation to yield compound II-1, and the reaction route is as follows:

[0040]

[0041] 2) Compound II-1 undergoes a bromine substitution reaction to yield compound III-1. The reaction route is as follows:

[0042]

[0043] 3) Compound III-1 and compound IV-2 undergo a substitution reaction to obtain compound V-2. The reaction route is as follows:

[0044]

[0045] Preferably, when the structural formula of compound V-3 is V-3, its preparation method is as follows:

[0046] 1) Compound I-3 undergoes sulfonation to yield compound II-3, and the reaction route is as follows:

[0047]

[0048] 2) Compound II-3 undergoes a bromine substitution reaction to yield compound III-3. The reaction route is as follows:

[0049]

[0050] 3) Compound III-3 and compound IV-3 undergo a substitution reaction to obtain compound V-3. The reaction route is as follows:

[0051]

[0052] Preferably, when the compound of formula V-4 has the structural formula V-4, its preparation method is as follows:

[0053] 1) Compound I-3 undergoes sulfonation to yield compound II-3, and the reaction route is as follows:

[0054]

[0055] 2) Compound II-3 undergoes a bromine substitution reaction to yield compound III-3. The reaction route is as follows:

[0056]

[0057] 3) Compound III-3 and compound IV-4 undergo a substitution reaction to obtain compound V-4. The reaction route is as follows:

[0058]

[0059] Preferably, when the structural formula of compound V is V-5, its preparation method is as follows:

[0060] 1) Compound I-1 undergoes sulfonation to yield compound II-1, and the reaction route is as follows:

[0061]

[0062] 2) Compound II-1 undergoes a bromine substitution reaction to yield compound III-1. The reaction route is as follows:

[0063]

[0064] 3) Compound III-1 and compound IV-5 undergo a substitution reaction to obtain compound V-5. The reaction route is as follows:

[0065]

[0066] Preferably, when the structural formula of compound V is V-6, its preparation method is as follows:

[0067] 1) Compound I-1 undergoes sulfonation to yield compound II-1, and the reaction route is as follows:

[0068]

[0069] 2) Compound II-1 undergoes a bromine substitution reaction to yield compound III-1. The reaction route is as follows:

[0070]

[0071] 3) Compound III-1 and compound IV-6 undergo a substitution reaction to obtain compound V-6. The reaction route is as follows:

[0072]

[0073] Preferably, when the structural formula of compound V is V-7, its preparation method is as follows:

[0074] 1) Compound I-7 undergoes sulfonation to yield compound II-7, and the reaction route is as follows:

[0075]

[0076] 2) Compound II-7 undergoes a bromine substitution reaction to yield compound III-7. The reaction route is as follows:

[0077]

[0078] 3) Compound III-7 and compound IV-7 undergo a substitution reaction to obtain compound V-7. The reaction route is as follows:

[0079]

[0080] Preferably, when the structural formula of compound V is V-8, its preparation method is as follows:

[0081] 1) Compound I-8 undergoes sulfonation to yield compound II-8, and the reaction route is as follows:

[0082]

[0083] 2) Compound II-8 undergoes a bromine substitution reaction to yield compound III-8. The reaction route is as follows:

[0084]

[0085] 3) Compound III-8 and compound IV-8 undergo a substitution reaction to obtain compound V-8. The reaction route is as follows:

[0086]

[0087] Preferably, when the structural formula of compound V is V-9, its preparation method is as follows:

[0088] 1) Compound I-8 undergoes sulfonation to yield compound II-8, and the reaction route is as follows:

[0089]

[0090] 2) Compound II-8 undergoes a bromine substitution reaction to yield compound III-8. The reaction route is as follows:

[0091]

[0092] 3) Compound III-8 and compound IV-9 undergo a substitution reaction to obtain compound V-9. The reaction route is as follows:

[0093]

[0094] Preferably, when the structural formula of compound V is V-10, its preparation method is as follows:

[0095] 1) Compound I-8 undergoes sulfonation to yield compound II-8, and the reaction route is as follows:

[0096]

[0097] 2) Compound II-8 undergoes a bromine substitution reaction to yield compound III-8. The reaction route is as follows:

[0098]

[0099] 3) Compound III-8 and compound IV-10 undergo a substitution reaction to prepare compound V-10. The reaction route is as follows:

[0100]

[0101] Preferably, in step 1), the reaction system contains a sulfonating agent, wherein the sulfonating agent is methanesulfonyl chloride (abbreviated as MsCl).

[0102] Preferably, in step 1), the molar ratio of the sulfonating agent to the compound of formula I is (1.0–1.4):1, and the sulfonating agent is in excess in order to convert more of the compound of formula I into the compound of formula II. More preferably, the molar ratio of the sulfonating agent to the compound of formula I is (1.2–1.4):1, such as 1.2:1, 1.3:1, or 1.4:1.

[0103] Preferably, in step 1), the reaction system uses the first organic solvent as the reaction medium.

[0104] Preferably, in step 1), the first organic solvent is one or both selected from dichloromethane and trichloromethane.

[0105] Preferably, in step 1), the reaction system further contains an acid-binding agent, wherein the acid-binding agent is an organic base containing at least one nitrogen atom. More preferably, the acid-binding agent is one or more selected from triethylamine, N,N-diisopropylethylamine, pyridine, α-methylpyridine, 4-dimethylaminopyridine, and quinoline. Even more preferably, the acid-binding agent is triethylamine. The acid-binding agent neutralizes the HCl generated in step 1), preventing HCl from affecting the reaction equilibrium and promoting the reaction equilibrium to the right, thereby playing a catalytic role.

[0106] Preferably, in step 1), the molar ratio of the acid-binding agent to the compound of formula I is (1.2–1.8):1. More preferably, the molar ratio of the acid-binding agent to the compound of formula I is (1.4–1.6):1, such as 1.4:1, 1.5:1, or 1.6:1. Excessive use of the acid-binding agent will result in waste of raw materials, while insufficient use will affect the catalytic effect.

[0107] The reaction in step 1) must be carried out at a low temperature. Too high a temperature will cause the reaction to be too vigorous, the product to turn yellow, and methanesulfonyl chloride has strong irritant and flammable properties. High temperatures will cause it to volatilize, which is not conducive to safe operation. Preferably, the reaction temperature in step 1) is (0-15)℃.

[0108] Preferably, step 1) includes the dropwise addition of MsCl to the compound of formula I, triethylamine, and the first organic solvent, which have been cooled to 0–15°C. During this process, an ice bath is used to control the temperature of the reaction system to remain between 0 and 15°C. Since the reaction in step 1) is highly exothermic, this effectively prevents temperature runaway and ensures complete reaction.

[0109] Preferably, step 1) further includes a post-processing step. The post-processing step includes separation and impurity removal. More preferably, the separation involves first quenching the reaction to form layers, then separating the liquid to obtain the organic phase. More preferably, water quenching is used. The aqueous phase obtained after separation can be extracted with dichloromethane, and the organic phases are combined. More preferably, the impurity removal includes one or more of water washing, drying, filtration, and evaporation. More preferably, the water washing uses saturated brine to wash the organic phase. More preferably, the drying uses anhydrous magnesium sulfate to dry the organic phase. More preferably, the filtration involves solid-liquid separation of the system after drying with a desiccant to extract the organic phase. More preferably, the evaporation uses a rotary evaporator to remove the solvent, with a heating temperature of 30–50°C and a vacuum degree of 0.1–20 kPa during evaporation.

[0110] Preferably, in step 2), the reaction system contains a brominating agent, which is one or more selected from sodium bromide, lithium bromide, and potassium bromide. More preferably, the brominating agent is selected from lithium bromide.

[0111] Preferably, the molar ratio of the brominating agent to the compound of formula II is (1.2–2.0):1. To promote complete bromination of the bromination reaction, the amount of brominating agent used is in excess relative to the compound of formula II. More preferably, the molar ratio of the brominating agent to the compound of formula II is (1.5–2.0):1, such as 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, or 2.0:1.

[0112] Preferably, in step 2), the reaction system contains a second organic solvent. Preferably, the second organic solvent is one or more selected from butanone, acetone, acetonitrile, tetrahydrofuran, dichloromethane, and trichloromethane.

[0113] Preferably, the reaction temperature in step 2) is 0–25°C. Since the reaction process involves slow exothermic reactions, an ice bath is usually required during the reaction to keep the temperature below room temperature, prevent overheating, better control the reaction process, and ensure the smooth progress of the reaction.

[0114] Preferably, in step 2), the reaction time is at least 8 hours. More preferably, the reaction time is 10 to 20 hours.

[0115] Preferably, step 2) further includes a post-processing step. The post-processing step includes evaporation, separation, and impurity removal. More preferably, the evaporation uses the second organic solvent, and the evaporation temperature is 30–50°C, and the vacuum degree is 0.1–20 kPa. More preferably, the separation involves first adding water to separate the layers, and then separating the liquid to obtain an organic phase and an aqueous phase. Preferably, the aqueous phase is extracted with ethyl acetate, and the organic phases are combined. The impurity removal includes one or more of water washing, drying, filtration, evaporation, and distillation. More preferably, the water washing uses one or two of water and a saturated saline solution to wash the organic phase. More preferably, the drying uses anhydrous magnesium sulfate to dry the organic phase. More preferably, the filtration is a solid-liquid separation of the system after drying with the addition of a desiccant to extract the organic phase. More preferably, the evaporation uses a rotary evaporator to remove the solvent, and the evaporation temperature is 30–50°C, and the vacuum degree is 0.1–20 kPa. More preferably, the distillation uses vacuum distillation to purify the product.

[0116] Preferably, in step 3), the molar ratio of the hydroxyl groups in compound III to compound IV is (1.0–1.6):1. Compound III is used in excess to promote the substitution reaction. More preferably, the molar ratio of compound III to compound IV is (1.2–1.6):1, such as 1.2:1, 1.3:1, 1.4:1, 1.5:1, or 1.6:1.

[0117] Preferably, in step 3), the reaction system contains a hydrogen-removing agent. The hydrogen-removing agent is one or more selected from lithium diisopropylaminolithium, n-butyllithium, tert-butyllithium, sodium hydride, potassium carbonate, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, and potassium tert-butoxide. The amount of the hydrogen-removing agent is usually adjusted according to its alkalinity to enable it to undergo the alcohol dehydrogenation reaction, thereby promoting the reaction in step 3).

[0118] Preferably, in step 3), the molar ratio of the dehydrogenating agent to the hydroxyl group in the compound of formula IV is (1.0 to 3.0):1, such as 1.0:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2.0:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, or 3.0:1.

[0119] Preferably, in step 3), the reaction system contains a third organic solvent.

[0120] Preferably, in step 3), the third organic solvent is one or more selected from N,N-dimethylformamide, tetrahydrofuran, dioxane, and chloroform.

[0121] Preferably, in step 3), the reaction temperature is ≥40℃. Too low a temperature will affect the reaction, while too high a temperature will cause overheating. To better control the reaction process and ensure its smooth progress, the reaction temperature is (40~150)℃. More preferably, the reaction temperature is 40~80℃, such as 40℃, 50℃, 60℃, 70℃, or 80℃.

[0122] Preferably, in step 3), the reaction time is at least 12 hours, and more preferably (18 to 24) hours.

[0123] Preferably, step 3) further includes a post-processing step. The post-processing step includes separation and impurity removal. More preferably, the separation involves first quenching the reaction to form layers, then separating the liquid to obtain the organic phase. More preferably, water quenching is used, followed by liquid-liquid separation to obtain the organic phase, extraction of the aqueous phase with ethyl acetate, and combining the organic phases. More preferably, the impurity removal includes one or more of water washing, drying, filtration, and evaporation. More preferably, the water washing involves washing the organic phase with one or both of water and saturated brine. More preferably, the drying is done using anhydrous magnesium sulfate to dry the organic phase. More preferably, the filtration is done by extracting the organic phase. More preferably, the evaporation is done using a rotary evaporator to remove the solvent, with the evaporation temperature at 30–50°C and the vacuum degree at 0.1–20 kPa.

[0124] Preferably, the synthetic ether-type base oil is used in the field of lubricating oil, such as turbine oil, hydraulic oil, compressor oil, oil film oil, gear oil, and marine system lubricating oil.

[0125] As described above, the synthetic ether-type base oil provided by this invention has a completely lipophilic side of its molecule and a hydrophilic ether bond at the tail, resulting in higher tolerance to water content in lubricating oils. When used as a lubricating oil base oil, it exhibits superior demulsibility and can separate more quickly after mixing with water, allowing for higher dissolved water content in the lubricating oil without exhibiting abnormal phenomena such as emulsification, turbidity, or reduced transparency. The synthetic ether-type base oil molecule does not contain highly hydrophilic polyoxyethylene segments, polyoxypropylene segments, or hydroxyl groups, resulting in higher solubility in mineral oils. Furthermore, compared to polyol ester base oils, the synthetic ether-type base oil molecule does not contain ester bonds, eliminating concerns about ester bond hydrolysis due to high water content. Therefore, the synthetic ether-type base oil is particularly suitable for lubricating oils requiring anti-emulsification performance, such as turbine oils, marine lubricating oils, anti-wear hydraulic oils, compressor oils, oil film oils, and gear oils.

[0126] The synthetic ether-based base oil in this application has a relatively low pour point, ensuring its lubricating effect even at low temperatures, making machine start-up easier. The synthetic ether-based base oil also has a high viscosity index, and its viscosity is not temperature-sensitive, guaranteeing a wide operating temperature range to meet diverse temperature requirements. This eliminates the need for seasonal oil changes, reducing operating costs. Furthermore, the preparation method of the synthetic ether-based base oil in this invention is simple to operate, uses readily available raw materials, causes minimal environmental pollution, and is easy to industrialize. Detailed Implementation

[0127] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0128] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0129] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0130] Example 1

[0131] In this embodiment, one specific compound of formula V-1 is:

[0132]

[0133] The specific synthetic route is shown in the figure below:

[0134]

[0135] The specific preparation method is as follows:

[0136] (1) Preparation of compound II-1

[0137] 1,4-Butanediol monomethyl ether (75 g, 0.72 mol) was added to a three-necked flask (1 L), and dichloromethane (30 mL) and triethylamine (150 mL, 1.07 mol) were added to dissolve compound I-1. After complete dissolution, the mixture was cooled to 0–5 °C in an ice bath, and methanesulfonyl chloride (72.5 mL, 0.94 mol) was slowly added dropwise at 0–5 °C. After the addition was complete, the mixture was stirred continuously at 0–5 °C for 5 min. The reaction was then determined to be complete by TLC (using petroleum ether / ethyl acetate as the eluent, with a volume ratio of 1:1).

[0138] After the reaction was completed, the reaction solution was poured into ice water (350 mL), and the organic phase was obtained by separation. The aqueous phase was extracted with dichloromethane, the organic phases were combined, washed once with saturated brine, dried with anhydrous magnesium sulfate, and then filtered. The filtrate was then evaporated under rotary evaporation at 30 °C and a vacuum of 20 kPa to remove the solvent, yielding compound II-1 (125 g, 0.69 mol). The product did not require further purification and was directly used for the next reaction.

[0139] (2) Preparation of compound III-1

[0140] Compound of formula II-1 was added to a three-necked flask (1L), dissolved in 350mL of butanone, and lithium bromide (92g, 1.06mol) was added dropwise at room temperature. The mixture was cooled in an ice-water bath, and the reaction temperature was controlled between 5 and 25°C. After stirring for 13h, TLC was performed (using petroleum ether / ethyl acetate as the eluent in a volume ratio of 1:1) to determine whether the reaction was complete.

[0141] After the reaction was completed, the reaction solution was evaporated to remove the butanone and poured into ice water (350 mL). The organic phase was obtained by separation. The aqueous phase was extracted once with ethyl acetate. The organic phases were combined and washed once with saturated brine. Then, the solution was dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation at 30 °C and a vacuum of 10 kPa to obtain the product compound III-1 (88.5 g, 0.53 mol). The total yield of the two steps (1) and (2) was 73.6%, and the purity was 97.3%.

[0142] 1 H-NMR (Bruker 400MHz, CDCl3): δ3.33 (2H,t,J=7.3Hz), 3.27 (2H,t,J=6.9Hz), 3.19 (3H,s), 1.83 (2H,tt,J=7.5,7.3Hz), 1.78 (2H,tt,J=7.5,6.9Hz).

[0143] (3) Preparation of compound V-1

[0144] 1,2-Tetradecanediol (46 g, 0.2 mol, 0.4 mol hydroxyl group) was added to a three-necked flask (1 L), and N,N-dimethylformamide (60 mL) was added to dissolve it. The mixture was cooled to 5 °C in an ice-water bath, and sodium hydride (16.8 g, 0.7 mol) was added. The mixture was stirred for 0.5 h, and then heated to room temperature. Compound III-1 (83.5 g, 0.5 mol) was added dropwise at room temperature. After the addition was completed in 1 h, the mixture was stirred at 40 °C for 20 h. The reaction was then analyzed by TLC (using petroleum ether / ethyl acetate with a volume ratio of 10:1) to determine if the reaction was complete.

[0145] After the reaction was completed, the reaction solution was poured into ice water (350 mL), and the organic phase was obtained by separation. The aqueous phase was extracted twice with ethyl acetate. The organic phases were combined and washed once with water and once with saturated saline solution. The solution was then dried with anhydrous magnesium sulfate, filtered, and the filtrate was evaporated under a vacuum of 10 kPa at 45 °C to remove the solvent and unreacted small molecule compounds, yielding 48 g of product V-1 compound, 0.12 mol. The yield of step (3) was 59.6%, and the purity was 95.7%.

[0146] 1 H-NMR(Bruker 400MHz, CDCl3): δ3.76(1H,tt,J=6.2,3.9Hz), 3.58(2H,d,J=3.9Hz), 3.40(2H,t,J=7.4Hz), 3.37(2H,t,J=7.3Hz), 3.31(4H,t,J=7.4H z),3.19(6H,s),1.79~1.85(8H,m),1.50(2H,td,J=7.3,6.2Hz),1.42(2H,tt,J=7.3,7.1Hz),1.19~1.28(18H,m),0.86(3H,t,J=7.0Hz)

[0147] Example 2

[0148] In this embodiment, a specific compound of formula V-2 is:

[0149]

[0150] The specific synthetic route is shown in the figure below:

[0151]

[0152] The specific preparation method is as follows:

[0153] (3) Preparation of compound V-2

[0154] The preparation method was the same as in Example 1. Compound III-1 was prepared using the preparation method in Example 1. The mass of compound III-1 was 83.5 g and 0.5 mol. Compound IV-2 was prepared using 1,2-decanediol, with a mass of 35 g and 0.2 mol (0.4 mol of hydroxyl group). Sodium hydride was used as the dehydrogenating agent, with a mass of 16.8 g and 0.70 mol. The reaction temperature was 55 °C. The amount of N,N-dimethylformamide was 60 mL. The reaction time was 20 h. The mass of the final product, compound V-2, was 43.5 g and 0.125 mol. The yield of step (3) was 62.7%, and the purity was 96.6%.

[0155] 1 H-NMR(Bruker 400MHz, CDCl3): δ3.76 (1H, tt, J=6.2, 3.9Hz), 3.58 (2H, d, J=3.9Hz), 3.40 (2H, t, J=7.4Hz), 3.37 (2H, t, J=7.3Hz), 3.31 (4H, t, J=7.4Hz ), 3.19 (6H, s), 1.78~1.85 (8H, m), 1.50 (2H, td, J=7.3, 6.2Hz), 1.42 (2H, tt, J=7.3, 7.1Hz), 1.18~1.26 (10H, m), 0.87 (3H, t, J=7.0Hz).

[0156] Example 3

[0157] In this embodiment, a specific compound of formula V-3 is:

[0158]

[0159] The specific synthetic route is shown in the figure below:

[0160]

[0161] The specific preparation method is as follows:

[0162] (1) Preparation of compound II-3

[0163] The preparation steps were the same as in Example 1, except that the compound of formula I-3 was prepared using ethylene glycol monoethyl ether, with an amount of 72.5 g and 0.80 mol of ethylene glycol monoethyl ether, an amount of 160 mL and 1.14 mol of triethylamine, an amount of 77 mL and 0.99 mol of methanesulfonyl chloride, and an amount of 30 mL of dichloromethane. The reaction temperature was 0–5 °C, and the mass of the product compound of formula II-3 was 129.5 g and 0.77 mol.

[0164] (2) Preparation of compound III-3

[0165] The preparation steps were the same as in Example 1, wherein the mass of lithium bromide was 102 g and 1.17 mol, the amount of butanone was 350 mL, the reaction time was 15 h, the reaction temperature was 5–25 °C, and the mass of the product compound III-3 was 91 g and 0.59 mol. The total yield of the two steps (1) and (2) was 74.3%, and the purity was 98.4%.

[0166] 1H-NMR (400MHz, CDCl3): δ3.65 (2H, t, J=6.1Hz), 3.35~3.47 (4H, m), 1.24 (3H, t, J=7.0Hz).

[0167] (3) Preparation of compound V-3

[0168] The preparation method was the same as in Example 1, wherein the mass of compound III-3 was 148 g and 0.97 mol, compound IV-3 was prepared using trimethylolpropane, the mass of trimethylolpropane was 34 g and 0.25 mol (0.75 mol of hydroxyl group), the mass of sodium hydride was 28.8 g and 1.2 mol, the amount of N,N-dimethylformamide was 60 mL, the reaction temperature was 65 °C, the reaction time was 22 h, and the mass of the final product compound V-3 was 63 g and 0.18 mol. The yield of step (3) was 71.9% and the purity was 93.4%.

[0169] 1 H-NMR(Bruker 400MHz, CDCl3): δ3.65 (12H, t, J=4.5Hz), 3.41 (6H, q, J=7.0Hz), 3.20 (6H, s), 1.42 (2H, q, J=7.6Hz), 1.24 (9H, t, J=7.0Hz), 0.84 (3H, t, J=7.6Hz).

[0170] Example 4

[0171] In this embodiment, a specific compound of formula V-4 is:

[0172]

[0173] The specific synthetic route is shown in the figure below:

[0174]

[0175] The specific preparation method is as follows:

[0176] (3) Preparation of compound V-4

[0177] The preparation method was the same as in Example 1. Compound III-3 was prepared using the preparation method in Example 3. The mass of compound III-3 was 199 g and 1.3 mol. Compound IV-4 was prepared using pentaerythritol, with a mass of 34 g and 0.25 mol (1.0 mol of hydroxyl group). The mass of sodium hydride was 38.4 g and 1.6 mol. The amount of N,N-dimethylformamide was 60 mL. The reaction temperature was 70 °C and the reaction time was 22 h. The mass of the final product, compound V-4, was 72 g and 0.17 mol. The yield of step (3) was 67.8% and the purity was 91.5%.

[0178] 1 H-NMR (Bruker 400MHz, CDCl3): δ3.66 (16H, t, J=4.5Hz), 3.41 (8H, q, J=7.0Hz), 3.23 (8H, s), 1.23 (12H, t, J=7.0Hz).

[0179] Example 5

[0180] In this embodiment, a specific compound of formula V-5 is:

[0181]

[0182] The specific synthetic route is shown in the figure below:

[0183]

[0184] The specific preparation method is as follows:

[0185] (3) Preparation of compound V-5

[0186] The preparation method was the same as in Example 1. Compound III-1 was prepared using the preparation method in Example 1. The mass of compound III-1 was 83.5 g and 0.5 mol. Compound IV-5 was hydrogenated bisphenol A, with a mass of 48 g and 0.2 mol (0.4 mol of hydroxyl group). The amount of N,N-dimethylformamide was 80 mL. Sodium hydride was used as the dehydrogenating agent, with a mass of 16.8 g and 0.70 mol. The reaction temperature was 55 °C and the reaction time was 20 h. The mass of the final product, compound V-5, was 51.5 g and 0.125 mol. The yield of step (3) was 62.4% and the purity was 97.8%.

[0187] 1H-NMR(Bruker 400MHz, CDCl3): δ3.63 (2H, quint, J = 2.8Hz), 3.38 (4H, t, J = 7.2Hz), 1.74 (4H, tt, J = 7.2, 7.0Hz), 1.69 (8H, m), 1.67 ~ 1.73 (8H, dtd, J = 13.2,6.5,2.8Hz),1.39(2H,tt,J=7.1,7.0Hz),1.36(4H,tt,J=10.3,2.8Hz),1.26~1.31(10H,m),0.96(6H,s),0.86(6H,t,J=7.0Hz)

[0188] Example 6

[0189] The specific structural formula of compound V-6 in this embodiment is as follows:

[0190]

[0191] The specific synthetic route is shown in the figure below:

[0192]

[0193] The specific preparation method is as follows:

[0194] (3) Preparation of compound V-6

[0195] The preparation method was the same as in Example 1. Compound III-1 was prepared using the preparation method in Example 1. The mass of compound III-1 was 254 g (1.52 mol). Compound IV-6 was prepared using pentaerythritol, with a mass of 51 g and 0.2 mol (1.2 mol of hydroxyl group). The amount of N,N-dimethylformamide was 80 mL, and the amount of sodium hydride was 42 g and 1.75 mol. The reaction temperature was 55 °C, and the reaction time was 20 h. The mass of the final product, compound V-6, was 106 g and 0.14 mol. The yield of step (3) was 68.7%, and the purity was 88.2%.

[0196] 1 H-NMR (Bruker 400MHz, CDCl3): δ3.36(12H,t,J=7.4Hz), 3.31(12H,t,J=7.4Hz), 3.20(4H,s), 3.19(12H,s), 3.18(18H,s), 1.78~1.87(24H,m)

[0197] Example 7

[0198] In this embodiment, a specific compound of formula V-7 is:

[0199]

[0200] The specific synthetic route is shown in the figure below:

[0201]

[0202] The specific preparation method is as follows:

[0203] (1) Preparation of compounds of formula II-7

[0204] The preparation method was the same as in Example 1, except that the compound of formula I-7 used 1,3-propanediol monomethyl ether, with an amount of 72.5 g (0.80 mol) of 1,3-propanediol monomethyl ether, 40 mL of chloroform, 191 mL of triethylamine, 1.36 mol of methanesulfonyl chloride, and 77 mL (0.99 mol). The reaction temperature was 0–5 °C, and the mass of the product compound of formula II-7 was 131 g (0.78 mol).

[0205] (2) Preparation of compounds of formula III-7

[0206] The preparation method is the same as in Example 1, wherein the amount of sodium bromide is 144.6 g and 1.40 mol, the solvent is acetonitrile and the amount is 300 mL, the reaction time is 18 h, the reaction temperature is 5-25 °C, and the mass of the product compound III-7 is 87.5 g and 0.57 mol. The total yield of the two steps (1) and (2) is 71.5%, and the purity is 97.8%.

[0207] 1 H-NMR (400MHz, CDCl3): δ3.30 (2H,t,J=4.4Hz), 3.20 (3H,s), 3.15 (2H,t,J=6.6Hz), 2.05 (2H,tt,J=6.6,4.4Hz).

[0208] (3) Preparation of compound V-7

[0209] The preparation method was the same as in Example 1, except that 1,2-tetradecanediol was used as the compound IV-7, with an amount of 46 g (0.20 mol) of 1,2-tetradecanediol and 0.4 mol of hydroxyl groups. The amount of compound III-7 was 76.5 g (0.5 mol). Tetrahydrofuran was used as the solvent, with an amount of 60 mL. Sodium ethoxide was used as the dehydrogenating agent, with an amount of 54.4 g and 0.8 mol. The reaction temperature was 55 °C, and the reaction time was 23 h. The mass of the product V-7 was 45.5 g and 0.12 mol, with a yield of 60.7% and a purity of 96.9%.

[0210] 1 H-NMR(Bruker 400MHz, CDCl3): δ3.75(1H,tt,J=6.2,3.9Hz), 3.57(2H,d,J=3.9Hz), 3.35(2H,t,J=5.0Hz), 3.31(2H,t,J=4.9Hz), 3.23~3.27(4H,m) ,3.19(6H,s),1.95~2.01(4H,m),1.52(2H,td,J=7.3,6.2Hz),1.41(2H,tt,J=7.3,7.1Hz),1.18~1.26(18H,m),0.86(3H,t,J=7.0Hz).

[0211] Example 8

[0212] In this embodiment, a specific compound of formula V-8 is:

[0213]

[0214] The specific synthetic route is shown in the figure below:

[0215]

[0216] The specific preparation method is as follows:

[0217] (1) Preparation of compounds of formula II-8

[0218] The preparation method was the same as in Example 1, except that the compound of formula I-8 was prepared using 1,5-pentanediol monobutyl ether, with an amount of 128 g (0.8 mol), 40 mL of chloroform, 160 mL of triethylamine (1.14 mol), and 77 mL of methanesulfonyl chloride (0.99 mol). The reaction temperature was 0–5 °C, and the mass of the product compound of formula II-8 was 185 g (0.78 mol).

[0219] (2) Preparation of compound III-8

[0220] The preparation method was the same as in Example 1, except that the amount of potassium bromide used was 139 g (1.17 mol), the solvent was acetonitrile (60 mL), the reaction time was 19 h, and the mass of the product compound III-8 obtained was 125.5 g (0.56 mol). The overall yield of the two steps (1) and (2) was 70.3%, and the purity was 96.7%.

[0221] 1H-NMR (400MHz, CDCl3) δ3.34~3.45(4H,m),3.27(2H,t,J=6.9Hz),1.81(2H,tt,J=7.5,6.9Hz),1 .74(2H,tt,J=7.2,7.0Hz), 1.67(2H,tt,J=7.4,6.9Hz), 1.33~1.48(4H,m), 0.88(3H,t,J=7.1Hz).

[0222] (3) Preparation of compound V-8

[0223] The preparation method was the same as in Example 1. In this method, 1,2-octanediol was used as the compound IV-8, with an amount of 29.2 g and 0.2 mol of 1,2-octanediol and 0.4 mol of hydroxyl groups. Compound III-8 was prepared using the method in Example 8, with an amount of 116 g and 0.52 mol of compound III-8. Dioxane was used as the solvent, with an amount of 50 mL. Potassium ethoxide was used as the dehydrogenating agent, with an amount of 50.5 g and 0.6 mol. The reaction temperature was 50 °C and the reaction time was 22 h. The mass of the product V-8 was 52.5 g and 0.12 mol. The yield of step (3) was 60.9% and the purity was 98.3%.

[0224] 1 H-NMR(Bruker 400MHz, CDCl3): δ3.75(1H,tt,J=6.2,3.9Hz), 3.57(2H,d,J=3.9Hz), 3.35(2H,t,J=5.0Hz), 3.31(2H,t,J=4.9Hz), 3.22~3.28(4H,m) ,3.19(6H,s),1.96~2.01(4H,m),1.52(2H,td,J=7.3,6.2Hz), 1.41(2H,tt,J=7.3,7.1Hz), 1.18~1.26(18H,m),0.86(3H,t,J=7.0Hz).

[0225] Example 9

[0226] In this embodiment, a specific compound of formula V-9 is:

[0227]

[0228] The specific synthetic route is shown in the figure below:

[0229]

[0230] The specific preparation method is as follows:

[0231] (3) Preparation of compound V-9

[0232] The preparation method was the same as in Example 1. In this method, 1,2-decanediol was used as the compound IV-9, with an amount of 35 g and 0.2 mol (0.4 mol of hydroxyl group). Compound III-8 was prepared using the method in Example 8, with an amount of 115 g and 0.5 mol. N,N-dimethylformamide was used as the solvent, with an amount of 60 mL. Sodium hydride was used as the dehydrogenating agent, with an amount of 16.8 g and 0.70 mol. The reaction temperature was 55 °C, and the reaction time was 20 h. The mass of the product V-9 was 55.5 g and 0.12 mol. The yield of step (3) was 60.5%, and the purity was 97.9%.

[0233] 1 H-NMR(Bruker 400MHz, CDCl3): δ3.76(1H,tt,J=6.2,3.9Hz), 3.58(2H,d,J=3.9Hz), 3.41(2H,t,J=7.2Hz), 3.30~3.37(10H,m), 1.70~1.774 (8H,m),1.67(4H,tt,J=7.2,6.9Hz),1.50(2H,td,J=7.3,6.2Hz),1.37~1.44(10H,m),1.21~1.28(6H,m),0.82~0.89(9H,m).

[0234] Example 10

[0235] In this embodiment, a specific compound of formula V-10 is:

[0236]

[0237] The specific synthetic route is shown in the figure below:

[0238]

[0239] The specific preparation method is as follows:

[0240] (3) Preparation of compound V-10

[0241] The preparation method was the same as in Example 1. In this method, compound IV-10 was prepared using trimethylolpropane, with an amount of 34 g and 0.25 mol (0.75 mol of hydroxyl group). Compound III-8 was prepared using the method described in Example 8, with an amount of 251 g and 1.125 mol. N,N-dimethylformamide was used as the solvent, with an amount of 60 mL. Sodium hydride was used as the dehydrogenating agent, with an amount of 28.8 g and 1.2 mol. The reaction temperature was 65 °C, and the reaction time was 22 h. The mass of the product V-10 was 82.5 g and 0.175 mol. The yield of step (3) was 70.2%, and the purity was 93.0%.

[0242] 1 H-NMR(Bruker 400MHz, CDCl3): δ3.31~3.44(18H,m),3.19(6H,s),1.75(12H,tt,J=7.2,6.9Hz),1.67( 6H,tt,J=7.2,6.9Hz), 1.38~1.45(14H,m), 0.88(9H,t,J=7.1Hz), 0.83(3H,t,J=7.5Hz).

[0243] The synthetic ether-type base oils prepared in Examples 1-10 were subjected to performance tests including kinematic viscosity, viscosity index, pour point, copper strip corrosion resistance, and demulsibility. The test methods are as follows:

[0244] The kinematic viscosity and viscosity index were determined using the test method for transparent fluids in ASTM D 445, "Test Method for Kinematic Viscosity of Transparent and Opaque Liquids", and the kinematic viscosity of synthetic ether base oils was tested at 100°C and 40°C.

[0245] Pour point was determined using the method specified in ASTM D97-96a, "Standard Method for Testing Pour Point of Petroleum Products".

[0246] The corrosion of copper sheets was determined by following the procedure in GB / T 5096-2017 "Test Method for Corrosion of Copper Sheets in Petroleum Products" (9.3 Test Tube Procedure: Applicable to Most Liquid Products), and the test was conducted at 100℃ for 3 hours. The corresponding corrosion level was recorded.

[0247] The demulsibility was determined using the method in ASTM D1401-19, "Standard Test Method for Water Separability of Petroleum and Synthetic Liquids," which tested the separation performance of synthetic ether base oils from water. The test temperature was 54±1℃. 40 mL of oil and 40 mL of water were mixed and stirred, and the time it took for the emulsion layer to decrease to 3 mL and 0 mL was recorded. The time was expressed in minutes. The shorter the water separation time, the better the demulsibility.

[0248] The test results of Examples 1-10 are shown in Table 1:

[0249] Table 1

[0250]

[0251] As shown in Table 1, the synthetic ether-type base oil of this invention has a high viscosity index and a low pour point. The viscosity indices are all greater than 138, indicating that the viscosity of the synthetic ether-type base oil is not sensitive to temperature. The pour points are all below -36°C, indicating that the coolant flows and pours easily at low temperatures. This ensures that the base oil can still provide lubrication at low temperatures, making it easy to start the machine at low temperatures. It can also meet a wide range of temperature requirements, eliminating the need for seasonal oil changes and reducing operating costs.

[0252] Regarding copper sheet corrosion, the examples in Table 1 all reach level 1a, meaning they are non-corrosive to copper sheets and will not cause corrosion or damage to related equipment during use, thus requiring no special anti-corrosion treatment.

[0253] Regarding demulsibility, the separation time of the synthetic ether-type base oils in Examples 1, 2, 5, 6, and 7 from water was significantly shorter. The separation time of the base oils in Examples 3-4 from water increased slightly. The separation time of the synthetic ether-type base oils in Examples 8-10 increased significantly when the emulsion layer decreased by 3 mL, and their demulsibility was not as good as that of Examples 1-7.

[0254] The synthetic ether-type base oils prepared in Examples 1, 2, 5, 6, and 7 have a methoxy group at the end of their molecules; the synthetic ether-type base oils prepared in Examples 3 and 4 have an ethoxy group at the end of their molecules; and the synthetic ether-type base oils prepared in Examples 8-10 have a n-butoxy group at the end of their molecules. The methoxy group is more hydrophilic than the ethoxy group, and the ethoxy group is more hydrophilic than the n-butoxy group. Therefore, the synthetic ether-type base oils formed in Examples 1, 2, 5, 6, and 7 can tolerate a higher dissolved water content and are less prone to emulsification, turbidity, and reduced transparency. This is reflected in the faster separation speed of the base oil from water, as seen in the anti-emulsification test results.

[0255] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A synthetic ether-type base oil, characterized in that, The synthetic ether-type base oil is one or more compounds selected from the formulas V-1, V-2, V-3, V-5, V-6, V-7, V-8, V-9, and V-10. 、 、 、 、 、 、 、 、 。 2. The synthetic ether-type base oil according to claim 1, characterized in that, The viscosity index of the synthetic ether-type base oil is not less than 130; And / or, the synthetic ether-type base oil has a kinematic viscosity of 5.0~8.0 mm at 40°C. 2 / s; And / or, the synthetic ether-type base oil has a kinematic viscosity of 1.5~3.5 mm at 100°C. 2 / s; And / or, the pour point of the synthetic ether-type base oil does not exceed -30°C.

3. A method for preparing a synthetic ether-type base oil as described in any one of claims 1 to 2, characterized in that, The preparation method includes the following steps: 1) Compound I undergoes a sulfonation reaction to yield compound II, and the reaction route is as follows: ； 2) Compound II undergoes a bromine substitution reaction to yield compound III. The reaction route is as follows: ； 3) Compound III and compound IV undergo a substitution reaction to prepare a synthetic ether-type base oil. The reaction route is as follows: ； Among them, the compound of formula I has the following structure: 、 、 、 ； Compound IV has the following structure: 、 、 、 、 、 。 4. The preparation method according to claim 3, characterized in that: In step 1), The reaction system contains a sulfonating agent, namely methanesulfonyl chloride; And / or, the reaction system also contains a first organic solvent; And / or, the reaction system also contains an acid-binding agent, said acid-binding agent being an organic base containing at least one nitrogen atom; And / or, the reaction temperature is 0–15℃.

5. The preparation method according to claim 4, characterized in that, The molar ratio of the sulfonating agent to the compound of formula I is (1.0–1.4):1; And / or, the first organic solvent is one or both selected from dichloromethane and trichloromethane; And / or, the molar ratio of the acid-binding agent to the compound of formula I is (1.2~1.8):

1.

6. The preparation method according to claim 3, characterized in that: In step 2): The reaction system contains a brominating agent, which is selected from one or more of sodium bromide, lithium bromide, and potassium bromide; And / or, the reaction system contains a second organic solvent; And / or, the reaction temperature is 0~25℃.

7. The preparation method according to claim 6, characterized in that: The molar ratio of the brominating agent to the compound of formula II is (1.2–2.0):1; And / or, the second organic solvent is one or more selected from butanone, acetone, acetonitrile, tetrahydrofuran, dichloromethane and trichloromethane.

8. The preparation method according to claim 3, characterized in that: In step 3), The molar ratio of the hydroxyl groups in the compound of formula III to those in the compound of formula IV is (1.0–1.6):1; And / or, the reaction system also contains a hydrogen-removing agent; And / or, the reaction system contains a third organic solvent; And / or, the reaction temperature is ≥40℃.

9. The preparation method according to claim 8, characterized in that: The molar ratio of the dehydrogenating agent to the hydroxyl group in the compound of formula IV is (1.0–3.0):1; And / or, the hydrogen-removing agent is one or more selected from lithium diisopropylaminolithium, n-butyllithium, tert-butyllithium, sodium hydride, potassium carbonate, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, and potassium tert-butoxide. And / or, the third organic solvent is one or more selected from N,N-dimethylformamide, tetrahydrofuran, dioxane, and chloroform.

10. Use of a synthetic ether-type base oil as described in any one of claims 1-2 or a compound as shown in formula V-4 as a base oil in the field of lubricating oils, characterized in that, The structural formula of compound V-4 is as follows: 。

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