Long-acting methanol engine oil and its preparation method and application

Abstract

This invention discloses a long-life methanol engine oil, its preparation method, and its application. The lubricating oil composition comprises: 30-35% API Group III or higher hydroisomerized base oil, 45.2-49.3% API Group IV polyalphaolefin (PAO), 8.6-10.5% composite additives meeting ACEA C3-2023 or Dexos1 GEN 3 requirements, 2-3% polyetheramine dispersant, 1.2-1.8% amine and phenolic composite antioxidant, 5-5.5% viscosity index improver, and emulsifiers, pour point depressants, and rust inhibitors. Through the synergistic effect of the high-performance composite additives and specific polyetheramines, this invention addresses the acid corrosion, abnormal piston ring area deposition, and emulsified rust problems in methanol engines within a system containing viscosity index improvers. It exhibits excellent long-term alkalinity retention, high-temperature deposit inhibition, oxidation resistance, and wear resistance, providing long-term comprehensive protection for methanol engines.

Description

Technical Field

[0001] This invention relates to engine oils, specifically to a long-life methanol engine oil, its preparation method, and its application. Background Technology

[0002] Methanol, as a clean fuel, is increasingly used in internal combustion engines. However, methanol combustion produces a large amount of formic acid (HCOOH) and small amounts of other organic acids. These acidic substances easily seep into the crankcase, causing rapid depletion of the total base number (TBN) of the lubricating oil, leading to acid corrosion and rust on key friction pairs such as cylinder liners, bearings, and camshafts. General-purpose engine oils have insufficient base number retention and acid neutralization speed. Secondly, incomplete combustion of methanol produces intermediate products such as aldehydes, ketones, and formate esters. These substances interact with engine oil oxidation products, easily forming hard, viscous varnish and carbon deposits in the high-temperature piston ring grooves, piston skirts, and oil rings. Unlike traditional soot deposits, these deposits are more likely to cause piston ring sticking, leading to increased blow-by, abnormal oil consumption, and reduced power. Furthermore, at low temperatures, unburned methanol and some oxidation products (such as water-soluble organic matter) are more likely to condense and mix into the engine oil, emulsifying with oxidation products and water in the oil to form low-temperature sludge, clogging the oil pump filter and oil passages.

[0003] Therefore, developing a specialized lubricating oil that can efficiently and persistently neutralize strong organic acids and effectively inhibit and remove deposits specific to methanol fuel is crucial for ensuring the long-term reliable operation of methanol engines. While existing technologies address methanol engine oils, they primarily focus on solving single problems (such as demulsification or preventing viscosity index improver failure), and remain insufficient in addressing the comprehensive challenges of acid corrosion, the formation of specific deposits, and the long-term stability of the oil. Summary of the Invention

[0004] Purpose of the Invention: The purpose of this invention is to provide a lubricating oil composition suitable for long-life engines using pure methanol (M100) or a high proportion of methanol as fuel, as well as its preparation method and application. This lubricating oil, through a unique additive formulation, addresses key issues such as abnormal deposition in the piston ring area caused by methanol combustion products, rapid degradation of oil base number, and emulsification for rust prevention, thereby comprehensively ensuring the long-term reliable operation of methanol engines.

[0005] Technical Solution: The long-life methanol engine oil of the present invention, based on 100% of the total mass of the composition, comprises: 30-35% API Group III or higher hydroisomerized base oil, 45.2-49.3% API Group IV polyalphaolefin (PAO); 8.6%-10.5% composite additives; 2-3% ashless dispersant polyetheramine; 1.2%-1.8% antioxidant, which is a mixture of amine and phenolic antioxidants; 5%-5.5% viscosity index improver; 0.5%-1% emulsifier; 0.2%-0.4% pour point depressant; and 0.3%-0.5% rust inhibitor.

[0006] Preferably, the composite additive meets the C3 technical specification in ACEA-2023 or the General Motors Dexos-1 GEN3 technical requirements, and its manufacturers include Infineon Technologies, Afton, Lubrizol, and Chevron Additives. It possesses excellent antioxidant and detergency / dispersing properties.

[0007] Preferably, the ashless dispersant polyetheramine is a monoamine with polypropylene glycol or polyethylene glycol / polypropylene glycol as its main chain. Polyetheramines have excellent dispersing and solubilizing effects on polar oxygen-containing deposits produced by methanol combustion.

[0008] Preferably, the antioxidant is a mixture of amine and phenolic antioxidants in a mass ratio of 1:1 to 2:1. Preferably, the antioxidant is a complex of alkylated diphenylamine and a phenolic ester antioxidant.

[0009] Preferably, the base oil has a kinematic viscosity of 4~8 mm at 100°C. 2 / s.

[0010] Preferably, the total base number (TBN) of the lubricating oil formulation is not less than 12 mgKOH / g.

[0011] Preferably, the emulsifier is a polymethacrylate. This ensures that the water produced after methanol combustion remains in an emulsified state, preventing water separation and abnormal engine wear.

[0012] Preferably, the rust inhibitor is at least one selected from zinc naphthenate, sodium petroleum sulfonate, barium petroleum sulfonate, and calcium petroleum sulfonate. Calcium petroleum sulfonate is preferred as the rust inhibitor.

[0013] Preferably, the pour point depressant is a methacrylate.

[0014] Preferably, the viscosity index improver has a shear index (SSI) ≤ 5.

[0015] The preparation method of the long-life methanol engine oil of the present invention includes adding the composite additive, ashless dispersant polyetheramine, antioxidant, viscosity index improver, emulsifier, pour point depressant and rust inhibitor sequentially to the base oil at 60~75℃ and under stirring conditions, and stirring at 700~900rpm for 30~50min.

[0016] The long-life methanol engine oil described in this invention is used in engines fueled with pure methanol (M100) or methanol by volume exceeding 50%.

[0017] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: This invention employs composite additives that meet the ACEA-2023 C3 technical specifications or the General Motors Dexos-1 GEN 3 technical requirements, and synergistically combines them with polyetheramine dispersants of a specific structure and high-performance antioxidants. This achieves efficient neutralization of acidic substances, strong inhibition and dispersion of unconventional deposits, and solves the problem of oil emulsification and rust prevention, constructing a completely new long-lasting protective system. Specifically, it has excellent acid neutralization capabilities, reducing the problem of excessively rapid consumption of oil base value and minimizing high-temperature deposits and carbon buildup. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to embodiments and comparative examples.

[0019] Lubricating oil samples of Examples 1-3 and Comparative Examples 1-4 were prepared according to the formulations shown in Table 1.

[0020] All raw materials used in this invention can be purchased from the market.

[0021] Table 1. Composition of Examples 1-3 and Comparative Examples 1-4

[0022] Table 2. Physicochemical property test data of Examples 1-3 and Comparative Examples 1-4

[0023] Remark: 1) High-Temperature Determination and Anti-Deposition Simulation Test (TEOST MHT-4): This test simulates the formation of high-temperature deposits in the piston ring groove region; 2) Oil aging test: In the laboratory, the working conditions of continuous formic acid contamination of engine oil are simulated, and the change of total base number (TBN) over time is monitored; 3) Pressure Differential Scanning Calorimetry (PDSC): The longer the test result time, the longer the service life of the oil. 4) Emulsion retention: Separation indicates poor emulsion retention.

[0024] Referring to Table 2, data from Example 1 and Comparative Example 1, and the data from the high-temperature detergency and anti-deposit capability simulation test (TEOSTMHT-4), show that the addition of the composite additive and polyetheramine dispersant of the present invention has significant advantages in inhibiting high-temperature varnish and deposits (simulating methanol combustion-derived deposits); it provides more durable and faster acid neutralization capability, effectively protecting the engine from acid corrosion and exhibiting superior oxidation resistance. Compared with Comparative Example 1, Example 2 shows that the polyetheramine with a monoamine structure has excellent detergency and dispersibility as well as oil acid neutralization performance. Compared with Comparative Example 2, Examples 1-3 show that oils meeting Dexos-1 GEN 3 technical specifications have good detergency and dispersibility as well as oil acid neutralization performance. Compared with Comparative Example 3, Examples 1-3 show that the formulation oils composed of API Group III and Group IV base oils have a longer service life, as indicated by aging tests and differential pressure scanning calorimetry. Compared with Comparative Example 4, Examples 2 shows excellent emulsification retention.

[0025] Table 3 shows the performance indicators of the used oil sampled after 15,000 km of driving: Table 3 Performance Indicators of Used Oil After 15,000km of Driving Tests

[0026] As can be seen from Table 3, Example 1 has superior base value retention and excellent acid neutralization performance compared to Comparative Example 1; the wear element content of the examples in the table is lower than that of Comparative Example 1, and they have excellent anti-corrosion and wear performance.

[0027] Conclusion: The long-life methanol engine lubricant provided by this invention innovatively adopts composite additives that meet the technical specifications of ACEA-2023 C3 or the requirements of General Motors Dexos-1 GEN 3, combined with a high-efficiency dispersant containing monoamine polyether amines. It not only rapidly and persistently neutralizes the large amount of acidic substances produced by methanol combustion, preventing corrosion, but also specifically inhibits and disperses high-temperature deposits and low-temperature sludge, effectively preventing piston ring sticking. Simultaneously, the optimized antioxidant system extends the oil's service life. This lubricant comprehensively solves the core challenges of methanol fuel to the lubrication system, providing crucial assurance for the long-term, efficient, and reliable operation of methanol engines.

Claims

1. A long-lasting methanol engine oil, characterized in that, Based on 100% of the total mass of the composition, it contains: 30-35% API Group III and above hydroisomerized base oil, 45.2-49.3% API Group IV polyalphaolefin (PAO); 8.6%-10.5% composite additives; 2-3% ashless dispersant polyetheramine; 1.2%-1.8% antioxidant; 5%-5.5% viscosity index improver; 0.5%-1% emulsifier; 0.2%-0.4% pour point depressant; and 0.3%-0.5% rust inhibitor.

2. The long-life methanol engine oil according to claim 1, characterized in that, The composite additive meets the C3 technical specification in ACEA-2023 or the technical requirements of General Motors Dexos-1 GEN 3.

3. The long-life methanol engine oil according to claim 1, characterized in that, The ashless dispersant polyetheramine is a monoamine with polypropylene glycol or polyethylene glycol / polypropylene glycol as the main chain.

4. The long-life methanol engine oil according to claim 1, characterized in that, The antioxidant is a mixture of amine and phenolic antioxidants in a mass ratio of 1:1 to 2:

1.

5. The long-life methanol engine oil according to claim 4, characterized in that, The amines are alkylated diphenylamines, and the phenols are phenolic ester type antioxidants.

6. The long-life methanol engine oil according to claim 1, characterized in that, The base oils are Group III and Group IV base oils, with a kinematic viscosity of 4~8 mm at 100°C. 2 / s.

7. The long-life methanol engine oil according to claim 1, characterized in that, The emulsifier is a polymethacrylate.

8. The long-life methanol engine oil according to claim 1, characterized in that, The rust inhibitor is at least one of zinc naphthenate, sodium petroleum sulfonate, barium petroleum sulfonate, and calcium petroleum sulfonate.

9. A method for preparing the long-life methanol engine oil according to any one of claims 1-8, characterized in that, The process involves adding the composite additive, ashless dispersant polyetheramine, antioxidant, viscosity index improver, emulsifier, pour point depressant, and rust inhibitor to the base oil at 60-75°C and under stirring conditions, and stirring until homogeneous.

10. Use of the long-life methanol engine oil according to any one of claims 1-8 or the long-life methanol engine oil prepared by the preparation method according to claim 9 in an engine using pure methanol (M100) or methanol as fuel by volume exceeding 50%.

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