CN115058274A - Lubricating oil composition for methanol fuel engine and preparation method thereof - Google Patents

Abstract

The present disclosure relates to a lubricating oil composition for a methanol-fueled engine, the lubricating oil composition containing an additive and a balance of a base oil; the base oil contains API I base oil and ester base oil; the aromatic hydrocarbon content of the API I base oil is 1-5 wt%; the additive contains a viscosity index improver and an emulsifier; the viscosity index improver is an ester viscosity index improver. The disclosure also discloses a method of making the lubricating oil composition. The lubricating oil composition for methanol fuel engines provided by the present disclosure significantly improves the emulsifying properties, anti-wear properties, and anti-corrosion properties of the lubricating oil.

Description

Lubricating oil composition for methanol fuel engine and preparation method thereof

Technical Field

The present disclosure relates to a lubricating oil, and in particular, to a lubricating oil composition for methanol-fueled engines and a method of making the same.

Background

At present, the aim of improving the quality of the ambient air is mainly achieved by developing measures of using clean energy and using alternative fuels, and the like, wherein the alcohol fuel is the most commonly used alternative fuel. According to current research and application, most engines can use low-proportion methanol gasoline (< 15%) without or with minor adjustments, but for high-proportion methanol-fueled engines (using methanol fuel above 30%), improvements in engine components are needed, while lubricating oils need to have good corrosion protection, wear resistance, and emulsifying properties.

The corrosion protection, wear resistance and emulsifying properties of the lubricating oils currently used in methanol fuel engines are still low.

Disclosure of Invention

The purpose of the present disclosure is to provide a lubricating oil composition for a methanol fuel engine and a preparation method thereof, so as to solve the technical problems of insufficient corrosion resistance, abrasion resistance and emulsifying performance of the lubricating oil for the methanol fuel engine in the prior art.

In a first aspect of the present disclosure, there is provided a lubricating oil composition for a methanol-fueled engine, the lubricating oil composition comprising an additive and a balance of a base oil; the base oil contains API I base oil and ester base oil; the aromatic hydrocarbon content of the base oil is 1-5 wt%; the additive contains a viscosity index improver and an emulsifier; the viscosity index improver is an ester viscosity index improver.

Optionally, the base oil comprises an API group III base oil; the weight ratio of the API group I base oil to the ester base oil to the API group III base oil is 10-20: 5-15: 55-70.

Optionally, the emulsifier comprises an anionic emulsifier and/or a nonionic emulsifier; preferably, the emulsifier comprises the anionic emulsifier and the nonionic emulsifier; the weight ratio of the anionic emulsifier to the nonionic emulsifier is 0.5-5: 1, and preferably 2: 1.

Optionally, the additive contains a friction reducer comprising zinc and/or molybdenum dioctyldithiophosphates; preferably, the friction reducing agent comprises zinc and molybdenum octyldialkyldithiophosphates; the weight ratio of the zinc butyl octyl dialkyl dithiophosphate to the molybdenum dialkyl dithiophosphate is 0.7-1: 0.1-0.7.

Optionally, the additive comprises an antioxidant comprising a phenolic antioxidant and/or an ammonia antioxidant; preferably, the antioxidant comprises the phenolic antioxidant and the ammonia antioxidant, and the weight ratio of the phenolic antioxidant to the ammonia antioxidant is 1: 1.7-2.2.

Optionally, the additive contains a detergent that is at least one of calcium sulfonate, calcium sulfurized alkylphenol, calcium alkyl salicylate, and magnesium alkyl salicylate; preferably, the detergent comprises calcium sulphonate.

Optionally, the additive contains a dispersant which is at least two of polyisobutylene succinimide ashless dispersant, boronized bis-polyisobutylene succinimide dispersant and mono-alkenyl polyisobutylene succinimide ashless dispersant; preferably, the dispersant comprises a polyisobutylene succinimide ashless dispersant and a boronated bis-polyisobutylene succinimide dispersant; the weight ratio of the polyisobutylene succinimide ashless dispersant to the boronized bis-polyisobutylene succinimide dispersant is 1.5-2.5: 0.5-1.5.

Optionally, the additive comprises a detergent, a dispersant, an antioxidant, a friction reducer, a pour point depressant; based on the total weight of the lubricating oil composition, the content of the detergent is 2-5 wt%, the content of the dispersant is 2-5 wt%, the content of the antioxidant is 0.5-2.1 wt%, the content of the friction reducer is 0.01-10 wt%, the content of the pour point depressant is 0.1-0.5 wt%, the content of the viscosity index improver is 0.1-50 wt%, and the content of the emulsifier is 0.05-3 wt%.

Optionally, the composition comprises 2.5 to 4.5 wt% of a detergent, 0.8 to 2.2 wt% of a polyisobutylene succinimide ashless dispersant, 0.6 to 2 wt% of a boronized bis-polyisobutylene succinimide dispersant, 0.7 to 1 wt% of zinc butyl octyl dialkyl dithiophosphate, 0.4 to 0.8 wt% of molybdenum dialkyl dithiophosphate, 1.4 to 2.1 wt% of an antioxidant, 0.15 to 0.35 wt% of a fumarate pour point depressant, 7 to 11 wt% of a polymethacrylate viscosity index improver, 0.14 to 0.19 wt% of an emulsifier and the balance of a base oil, based on the total weight of the lubricating oil composition;

the antioxidant comprises a phenol antioxidant and an ammonia antioxidant, and the weight ratio of the phenol antioxidant to the ammonia antioxidant is 0.45-0.75: 0.95-1.45;

the emulsifier contains an anionic emulsifier and a nonionic emulsifier, and the weight ratio of the anionic emulsifier to the nonionic emulsifier is 0.09-0.13: 0.04-0.07;

the weight ratio of the API group I base oil, the ester base oil and the API group III base oil is 10-18: 10-15: 60-65.

In a second aspect of the present disclosure, there is provided a method of preparing a lubricating oil composition of the first aspect, the method comprising the steps of: carrying out first mixing on the base oil and the viscosity index improver, and then adding the emulsifier for second mixing;

preferably, the temperature of the first mixing is 40-55 ℃, and the time is 30-60 min; the temperature of the second mixing is 55-62 ℃, and the time is 30-60 min.

According to the scheme disclosed by the invention, the API I base oil and the ester base oil are used, the aromatic hydrocarbon content in the base oil is controlled, and the emulsifier is used, so that the corrosion resistance, wear resistance and emulsifying performance of the lubricating oil can be obviously improved.

Additional features and advantages of the disclosure will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure without limiting the disclosure. In the drawings:

FIG. 1 is a schematic illustration of the emulsification of composition 1, composition 2 and a common commercially available product SN 5W-30.

Detailed Description

The following detailed description of specific embodiments of the present disclosure is provided in connection with the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present disclosure, are given by way of illustration and explanation only, not limitation.

A first aspect of the present disclosure provides a lubricating oil composition for a methanol-fueled engine, the lubricating oil composition containing an additive and a balance of a base oil;

the base oil contains API I base oil and ester base oil; the aromatic hydrocarbon content of the base oil is 1-5 wt%; the additive contains a viscosity index improver and an emulsifier; the viscosity index improver is an ester viscosity index improver.

The methanol fuel reacts with oxygen in the combustion process to generate carbon dioxide and a large amount of water, and when a water layer exists on the surface of the engine, abnormal abrasion can be caused, so that cylinder scuffing and tile holding are caused, a water-in-oil emulsified state needs to be formed, and the water layer is prevented from directly contacting the surface of the engine.

The water molecules are polar molecules, in order to form a water-in-oil emulsified state, the I-type base oil and the ester base oil with high aromatic hydrocarbon content are selected, the ester viscosity index improver with high polarity is selected, and in order to promote interaction of water with the I-type base oil and the ester viscosity index improver and promote emulsification, the lubricating oil composition disclosed by the invention contains a certain emulsifier.

According to the lubricating oil, the API I base oil, the ester base oil and the ester viscosity index improver are interacted with water under the action of the emulsifier to form a water-in-oil emulsified state, so that the emulsifying property of the lubricating oil is improved, the direct contact of a water layer and the surface of an engine is avoided, and the abrasion resistance and the corrosion resistance of the lubricating oil are improved.

When a methanol engine is used, methanol is easy to leak into lubricating oil from a crankcase when incompletely combusted, the methanol has strong solubility, and the lubricating oil on the cylinder wall is easy to clean, so that a lubricating oil film on a friction surface is diluted or seriously aged, the lubricating function is lost, and the abrasion is increased. Meanwhile, after methanol absorbs water, the methanol is easy to react with an antioxidant antiwear agent in the lubricating oil, so that the corrosion resistance and the abrasion resistance of the lubricating oil are weakened.

When the lubricating oil is used for a long time and contains methanol, the methanol and the water can be emulsified by using the lubricating oil composition disclosed by the invention, and the lubricating oil has better corrosion resistance and abrasion resistance.

Preferably, the ester viscosity index improver is a methacrylate viscosity index improver.

Preferably, the base oil comprises an API group III base oil; the weight ratio of the API group I base oil to the ester base oil to the API group III base oil is 10-20: 5-15: 55-70. By controlling the contents of the API I base oil and the ester base oil, the corrosion resistance and the abrasion resistance of the lubricating oil can be further improved by promoting emulsification.

Group I base oils include, but are not limited to, Ia500, Ib150, IC 500, AP/E150, AP/E600; group III base oils include, but are not limited to, HVI III4, HVI III6, S4, S6, S8, Yu4, Yu 6; ester base oils include, but are not limited to, pentaerythritol ester, sebacic acid ester, azelaic acid ester under the designation 3970.

Preferably, the viscosity index of the base oil is 120-140.

Preferably, the emulsifier comprises an anionic emulsifier and/or a nonionic emulsifier; preferably, the emulsifier comprises the anionic emulsifier and the nonionic emulsifier; the weight ratio of the anionic emulsifier to the nonionic emulsifier is 0.5-5: 1, and preferably 2: 1. The lubricating oil is usually alkalescent, the use of the anionic emulsifier and the nonionic emulsifier is beneficial to improving the emulsifying property and the emulsifying stability, and the lubricating oil can have positive influence on the anti-wear property after being emulsified.

Preferably, the additive comprises a friction reducer comprising zinc and/or molybdenum dioctyldithiophosphates; preferably, the friction reducing agent comprises zinc and molybdenum octyldialkyldithiophosphates; the weight ratio of the zinc butyl octyl dialkyl dithiophosphate to the molybdenum dialkyl dithiophosphate is 0.7-1: 0.1-0.7.

Preferably, the additive contains an antioxidant, and the antioxidant contains a phenolic antioxidant and/or an ammonia antioxidant; preferably, the antioxidant comprises the phenolic antioxidant and the ammonia antioxidant, and the weight ratio of the phenolic antioxidant to the ammonia antioxidant is 1: 1.7-2.2.

Preferably, the additive contains a detergent which is at least one of calcium sulfonate, calcium sulfurized alkylphenol, calcium alkyl salicylate and magnesium alkyl salicylate; preferably, the detergent comprises calcium sulphonate.

Preferably, the additive contains a dispersant which is at least two of polyisobutylene succinimide ashless dispersant, boronized bis-polyisobutylene succinimide dispersant and mono-alkenyl polyisobutylene succinimide ashless dispersant; preferably, the dispersant comprises polyisobutylene succinimide ashless dispersant and boronized bis-polyisobutylene succinimide dispersant; the weight ratio of the polyisobutylene succinimide ashless dispersant to the boronized bis-polyisobutylene succinimide dispersant is 1.5-2.5: 0.5-1.5.

Preferably, the additive contains a detergent, a dispersant, an antioxidant, a friction reducer, and a pour point depressant;

based on the total weight of the lubricating oil composition, the content of the detergent is 2-5 wt%, the content of the dispersant is 2-5 wt%, the content of the antioxidant is 0.5-2.1 wt%, the content of the friction reducer is 0.01-10 wt%, the content of the pour point depressant is 0.1-0.5 wt%, the content of the viscosity index improver is 0.1-50 wt%, and the content of the emulsifier is 0.05-3 wt%.

Preferably, the pour point depressant is at least one of polymethacrylate, poly-alpha-olefin and fumarate.

The detergent disclosed by the invention has a cleaning effect, has a certain influence on the emulsifying property of an oil product, and can weaken the abrasion resistance and the corrosion resistance of lubricating oil when the content of the detergent is more than 5 wt%. The dispersant mainly functions as a dispersant, and when the content of the dispersant is more than 5%, the antiwear performance of the lubricating oil is reduced.

Preferably, the composition comprises 2.5-4.5 wt% of a detergent, 0.8-2.2 wt% of a polyisobutylene succinimide ashless dispersant, 0.6-2 wt% of a boronized bis-polyisobutylene succinimide dispersant, 0.7-1 wt% of zinc butyl octyl dialkyl dithiophosphate, 0.4-0.8 wt% of molybdenum dialkyl dithiophosphate, 1.4-2.1 wt% of an antioxidant, 0.15-0.35 wt% of a fumarate pour point depressant, 7-11 wt% of a polymethacrylate viscosity index improver, 0.14-0.19 wt% of an emulsifier and the balance of base oil, based on the total weight of the lubricating oil composition;

the antioxidant comprises a phenol antioxidant and an ammonia antioxidant, and the weight ratio of the phenol antioxidant to the ammonia antioxidant is 0.45-0.75: 0.95-1.45;

the emulsifier contains an anionic emulsifier and a nonionic emulsifier, and the weight ratio of the anionic emulsifier to the nonionic emulsifier is 0.09-0.13: 0.04-0.07;

the weight ratio of the API group I base oil, the ester base oil and the API group III base oil is 10-18: 10-15: 60-65.

In a second aspect of the present disclosure, there is provided a method of making a lubricating oil composition of the first aspect, the method comprising the steps of: carrying out first mixing on the base oil and the viscosity index improver, and then adding the emulsifier for second mixing;

preferably, the temperature of the first mixing is 40-55 ℃, and the time is 30-60 min; the temperature of the second mixing is 55-62 ℃, and the time is 30-60 min. By using the method disclosed by the invention to prepare the lubricating oil, the dispersion of the viscosity index improver and the like in the base oil can be promoted, and the generation of precipitates can be avoided.

Preferably, the base oil, the viscosity index improver and the pour point depressant are first mixed, and then the dispersant, the detergent, the friction reducer, the antioxidant and the emulsifier are added for second mixing.

The present disclosure is further illustrated by the following examples. The raw materials used in the examples are all available from commercial sources.

Example 1

Composition 1 contained 3.0g of detergent (1.8g of high base calcium sulfonate and 1.2g of medium base calcium sulfonate), 2.0g of ashless polyisobutylene succinimide dispersant, 0.8g of boronated bis-polyisobutylene succinimide dispersant, 0.75g of zinc butyloctyl dialkyldithiophosphate, 0.7g of molybdenum dialkyldithiophosphate, 0.5g of phenolic antioxidant (L135, basf), 1g of ammonia antioxidant (L67, basf), 0.3g of fumarate pour point depressant, 0.1g of anionic emulsifier (sodium lauryl sulfate), 0.05g of nonionic emulsifier (Span 80), 8g of polymethacrylate index improver, 15g of group I viscosity base oil (Ib150), 10g of ester base oil (3970) and 64.8g of group III base oil (S8), based on the total weight of lubricating oil composition 1.

First mixing the 0.3g of fumarate pour point depressant, 8g of polymethacrylate viscosity index improver, 15g of group I base oil (Ib150), 10g of ester base oil (3970) and 64.8g of group III base oil (S8), and then adding 3.0g of detergent, 2.0g of polyisobutylene succinimide ashless dispersant, 0.8g of boronated bis-polyisobutylene succinimide dispersant, 0.75g of zinc octyldialkyldithiophosphate, 0.7g of molybdenum dialkyldithiophosphate, 0.5g of phenolic antioxidant, 1g of ammonia type antioxidant, 0.1g of anionic emulsifier (sodium lauryl sulfate) and 0.05g of nonionic emulsifier (Span 80) for second mixing; further, composition 1 was obtained.

The temperature of the first mixing is 50 ℃ and the time is 45 min; the temperature of the second mixing was 59 ℃ for 50 min.

Example 2

Composition 2 contained 4.0g of detergent (2g of high base calcium sulfonate, 2g of medium base calcium sulfonate), 1.0g of ashless polyisobutylene succinimide dispersant, 1.8g of boronated bis-polyisobutylene succinimide dispersant, 0.95g of zinc octyldialkyl dithiophosphate, 0.5g of molybdenum dialkyl dithiophosphate, 0.7g of phenolic antioxidant (L135, basf), 1.4g of ammonia antioxidant (L67, basf), 0.2g of fumarate pour point depressant, 0.12g of anionic emulsifier (sodium dodecylbenzene sulfonate), 0.06g of nonionic emulsifier (Tween 80), 10g of polymethacrylate viscosity index improver, 12g of group I base oil (Ib150), 15g of ester base oil (3970) and 60.4g of group III base oil (HVI III 6), based on the total weight of lubricating oil composition 2.

First mixing the 0.2g fumarate pour point depressant, 10g polymethacrylate viscosity index improver, 12g group I base oil (Ib150), 15g ester base oil (3970) and 60.4g group III base oil (HVI III 6), and then adding 4.0g detergent, 1.0g polyisobutylene succinimide ashless dispersant, 1.8g boronized bis-isobutylene succinimide dispersant, 0.95g zinc butyl octyl dialkyl dithiophosphate, 0.5g molybdenum dialkyl dithiophosphate, 0.7g phenolic antioxidant, 1.4g ammonia antioxidant, 0.12g anionic emulsifier (sodium dodecyl benzene sulfonate) and 0.06g nonionic emulsifier (Tween 80) for second mixing; further, composition 2 was obtained.

The temperature of the first mixing is 50 ℃, and the time is 30 min; the temperature of the second mixing was 62 ℃ for 30 min.

Example 3

Composition 3 contained 2.0g of detergent (0.8g of high base calcium sulfonate, 1.2g of medium base calcium sulfonate), 1.0g of ashless polyisobutylene succinimide dispersant, 1.0g of boronated bis-polyisobutylene succinimide dispersant, 0.01g of zinc butyloctyl dialkyldithiophosphate, 0.2g of phenol type antioxidant (L135, basf), 0.3g of ammonia type antioxidant (L67, basf), 0.1g of fumarate pour point depressant, 0.03g of anionic emulsifier (sodium didodecylphenyl ether disulfonate), 0.02g of nonionic emulsifier (fatty acid sorbitan ester), 50g of polymethacrylate viscosity index improver, 6.31g I base oil (Ia500), 3.22g of ester base oil (azelaic acid ester), and 34.81g of group III base oil (Yu 6), based on the total weight of lubricating oil composition 3.

First mixing the 0.1g fumarate pour point depressant, 50g polymethacrylate viscosity index improver, 6.31g I base oil (Ia500), 3.22g ester base oil (azelaic acid ester) and 34.81g group III base oil (Yu 6), and then second mixing with 2.0g detergent, 1.0g polyisobutylene succinimide ashless dispersant, 1.0g boronized bis-polyisobutylene succinimide dispersant, 0.01g zinc octyldialkyl dithiophosphate, 0.2g phenol type antioxidant, 0.3g ammonia type antioxidant, 0.03g anionic emulsifier (sodium didodecylphenyl ether disulfonate) and 0.02g nonionic emulsifier (fatty acid sorbitol ester); further, composition No. 3 was obtained.

The temperature of the first mixing is 55 ℃ and the time is 30 min; the temperature of the second mixing is 62 ℃ and the time is 30 min.

Example 4

Composition 4 contained 5.0g of detergent (2g of high base calcium sulfonate, 3g of medium base calcium sulfonate), 2.5g of ashless polyisobutylene succinimide dispersant, 2.5g of boronated bis-polyisobutylene succinimide dispersant, 9g of zinc dioctyldithiophosphate, 1g of molybdenum dialkyldithiophosphate, 1g of phenolic antioxidant (L135, basf), 1.1g of ammonia antioxidant (L67, basf), 0.5g of fumarate pour point depressant, 2g of anionic emulsifier (sodium didodecylphenyl ether disulfonate), 1g of nonionic emulsifier (Tween 80), 0.1g of polymethacrylate viscosity index improver, 14.16g I type base oil (Ia900), 10.61g of ester type base oil (sebacic ester), and 49.53g of group III base oil (S8), based on the total weight of lubricating oil composition 4.

First mixing the 0.5g fumarate pour point depressant, 0.1g polymethacrylate viscosity index improver, 14.16g I base oil (Ia900), 10.61g ester base oil (sebacic ester) and 59.53g group III base oil (S8), and then second mixing with 5.0g detergent, 2.5g polyisobutylene succinimide ashless dispersant, 2.5g boronized bis-polyisobutylene succinimide dispersant, 9g butyl octyl dialkyl zinc dithiophosphate, 1g molybdenum dialkyl dithiophosphate, 1g phenolic antioxidant, 1.1g ammonia antioxidant, 2g anionic emulsifier (sodium didodecyl phenyl ether disulfonate) and 1g nonionic emulsifier (Tween 80); further, composition 4 was obtained.

The temperature of the first mixing is 40 ℃ and the time is 60 min; the temperature of the second mixing was 55 ℃ and the time was 60 min.

Comparative example

Common commercially available SN 5W-30, SP 0W-12, CI-420W-50, and SP 0W-20.

Test example 1

Placing composition 1, composition 2 and common commercially available SN 5W-30 in a constant temperature cabinet (adding H according to the volume ratio of 1: 1) ₂ O), the temperature was set at 54 ℃ for 0.5 hour, then, composition 1, composition 2 and ordinary commercially available SN 5W-30 were stirred simultaneously for 5 minutes, and then, composition 1, composition 2 and ordinary commercially available SN 5W-30 were left to stand in the same environment for 48 hours, and the delamination of composition 1, composition 2 and ordinary commercially available SN 5W-30 was observed. The results are shown in FIG. 1 and Table 1.

TABLE 1

The addition of water to compositions 1 and 2 resulted in a lower oil layer and no water rich layer, forming a homogeneous emulsion layer, compared to the common commercial product SN 5W-30, indicating that compositions 1 and 2 had a better emulsification of water than the commercial lubricating oil.

Test example 2

Placing the composition 3 and the composition 4 and common commercial SP 0W-12 and CI-420W-50 in a constant temperature box (adding H according to the mass ratio of 1:0.5: 0.1) ₂ O and methanol) at 54 deg.C for 0.5 hr, stirring composition 3, composition 4 and common commercial SP 0W-12 and CI-420W-50 for 5min, standing composition 3, composition 4 and common commercial SP 0W-12 and CI-420W-50 in the same environment for 48 hr, 240 hr, 480 hrh and 720h, observe the delamination of composition 3, composition 4 and the common commercial SP 0W-12, CI-420W-50. The results are shown in Table 2.

TABLE 2

In contrast to the conventional commercial products SP 0W-12 and CI-420W-50, no water layer was formed after the addition of water and methanol to compositions 3 and 4, indicating that both methanol and water were emulsified by compositions 3 and 4 when the lubricating oil contained methanol.

Test example 3

The friction wear test was carried out on composition 1, composition 2, and composition 4, and comparative oils SP 0W-20, SN 5W-30, and SP 0W-12 using HFRR (high frequency reciprocating rig). The test conditions are that the contact load is 100g, the stroke is 1mm, the reciprocating frequency is 50Hz, the temperature is 50 ℃, and the test duration is 60 min. The results are shown in Table 3.

TABLE 3

Compositions 1, 2 and 4 had excellent frictional wear properties as compared with the conventional commercial products SP 0W-12, SP 0W-12 and SN 5W-30.

Test example 4

The composition 2 and the ordinary SN 5W-30 engine oil on the market were subjected to an engine durability test (400h alternating load test) on a 100% methanol engine, and after the completion of the test, the old oils of the composition 2 and the SN 5W-30 engine oil were sampled and analyzed, and the results are shown in Table 4:

TABLE 4

Composition 2 was used for 400h engine operation with 100% methanol, no engine abnormality. The commercially available SN 5W-30 engine oil is used for an engine using 100% methanol, and when the engine runs for 100 hours, the engine is normal; when the running time reaches 200h, the engine begins to generate abnormal noise, and the test is immediately terminated. The metal content of composition 2 (after 400h of operation) is significantly lower than the metal content of the commercially available SN 5W-30 (after 200h of operation). The lubricating oil of the present disclosure for a 100% methanol-using engine has excellent anti-friction wear properties while increasing the service life of the engine compared to commercially available SN 5W-30 engine oils.

The preferred embodiments of the present disclosure are described in detail with reference to the accompanying drawings, however, the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present disclosure within the technical idea of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

It should be noted that, in the above embodiments, the various features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various possible combinations will not be further described in the present disclosure.

In addition, any combination of various embodiments of the present disclosure may be made, and the same should be considered as the disclosure of the present disclosure, as long as it does not depart from the spirit of the present disclosure.

Claims (10)

1. A lubricating oil composition for a methanol-fueled engine, comprising an additive and a balance of a base oil;

the base oil contains API I base oil and ester base oil; the aromatic hydrocarbon content of the base oil is 1-5 wt%;

the additive contains a viscosity index improver and an emulsifier; the viscosity index improver is an ester viscosity index improver.

2. The lubricating oil composition according to claim 1, wherein the base oil comprises an API group III base oil, and the weight ratio of the API group I base oil to the ester base oil to the API group III base oil is 10-20: 5-15: 55-70.

3. Lubricating oil composition according to claim 1 or 2, wherein the emulsifier comprises an anionic emulsifier and/or a non-ionic emulsifier;

preferably, the emulsifier comprises the anionic emulsifier and the nonionic emulsifier;

the weight ratio of the anionic emulsifier to the nonionic emulsifier is 0.5-5: 1, and preferably 2: 1.

4. Lubricating oil composition according to claim 1 or 2, wherein the additive contains a friction reducing agent comprising zinc and/or molybdenum dioctyldithiophosphates;

preferably, the friction reducing agent comprises zinc and molybdenum octyldialkyldithiophosphates;

the weight ratio of the zinc butyl octyl dialkyl dithiophosphate to the molybdenum dialkyl dithiophosphate is 0.7-1: 0.1-0.7.

5. The lubricating oil composition according to claim 1 or 2, wherein the additive comprises an antioxidant comprising a phenolic antioxidant and/or an ammonia antioxidant;

preferably, the antioxidant comprises the phenolic antioxidant and the ammonia antioxidant, and the weight ratio of the phenolic antioxidant to the ammonia antioxidant is 1: 1.7-2.2.

6. The lubricating oil composition of claim 1 or 2, wherein the additive contains a detergent that is at least one of calcium sulfonate, calcium sulfurized alkylphenol, calcium alkyl salicylate, and magnesium alkyl salicylate;

preferably, the detergent comprises calcium sulphonate.

7. The lubricating oil composition of claim 1 or 2, wherein the additive contains a dispersant which is at least two of a polyisobutylene succinimide ashless dispersant, a borated bis-polyisobutylene succinimide dispersant and a mono-alkenyl polyisobutylene succinimide ashless dispersant;

preferably, the dispersant comprises polyisobutylene succinimide ashless dispersant and boronized bis-polyisobutylene succinimide dispersant;

the weight ratio of the polyisobutylene succinimide ashless dispersant to the boronized bis-polyisobutylene succinimide dispersant is 1.5-2.5: 0.5-1.5.

8. Lubricating oil composition according to claim 1 or 2, wherein the additive comprises a detergent, a dispersant, an antioxidant, a friction reducing agent, a pour point depressant;

based on the total weight of the lubricating oil composition, the content of the detergent is 2-5 wt%, the content of the dispersant is 2-5 wt%, the content of the antioxidant is 0.5-2.1 wt%, the content of the friction reducer is 0.01-10 wt%, the content of the pour point depressant is 0.1-0.5 wt%, the content of the viscosity index improver is 0.1-50 wt%, and the content of the emulsifier is 0.05-3 wt%.

9. The lubricating oil composition according to claim 1 or 2, wherein the composition comprises 2.5 to 4.5 wt% of a detergent, 0.8 to 2.2 wt% of a polyisobutylene succinimide ashless dispersant, 0.6 to 2 wt% of a boronated bis-polyisobutylene succinimide dispersant, 0.7 to 1 wt% of a zinc butyloctyl dialkyldithiophosphate, 0.4 to 0.8 wt% of a molybdenum dialkyldithiophosphate, 1.4 to 2.1 wt% of an antioxidant, 0.15 to 0.35 wt% of a fumarate pour point depressant, 7 to 11 wt% of a polymethacrylate viscosity index improver, 0.14 to 0.19 wt% of an emulsifier, and the balance being a base oil, based on the total weight of the lubricating oil composition;

the antioxidant comprises a phenol antioxidant and an ammonia antioxidant, and the weight ratio of the phenol antioxidant to the ammonia antioxidant is 0.45-0.75: 0.95-1.45;

the emulsifier contains an anionic emulsifier and a nonionic emulsifier, and the weight ratio of the anionic emulsifier to the nonionic emulsifier is 0.09-0.13: 0.04-0.07;

the weight ratio of the API I base oil, the ester base oil and the API III base oil is 10-18: 10-15: 60-65.

10. A process for preparing a lubricating oil composition according to any of claims 1 to 9, characterised in that the process comprises the steps of: carrying out first mixing on the base oil and the viscosity index improver, and then adding the emulsifier for second mixing;

preferably, the temperature of the first mixing is 40-55 ℃, and the time is 30-60 min; the temperature of the second mixing is 55-62 ℃, and the time is 30-60 min.

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