Natural gas compressor cylinder oil composition and preparation method thereof

Abstract

The invention discloses a natural gas compressor cylinder oil composition, which is prepared from the following ingredients in percentage by mass: 88.0 to 93.5 percent of oil soluble PAG polyether base oil, 5.0 to 8.0 percent of ionic liquid, 1.5 to 3.5 percent of antioxidants, 0.03 to 0.1 percent of metal deactivators, 0.05 to 0.12 percent of ash-free extreme pressure anti-wear agents, 0.08 to 0.15 percent of antirust agents and 0.005 to 0.03 percent of anti-foaming agents. The invention also discloses a preparation method of the composition, which specifically comprises the following steps: adding the oil-soluble PAG polyether and the ionic liquid into a blending kettle, stirring, then adding the antioxidant, the metal deactivator, the ash-free extreme pressure anti-wear agent and the antirust agent, stirring, and finally adding the anti-foaming agent, and stirring. According to the invention, the ionic liquid which is not easy to absorb methane gas is selected from the oil-soluble PAG polyether base oil as a lubricating oil additive, so that the overall methane gas flushing and diluting resisting effect of the lubricating oil is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of compressor lubricating oil, and in particular relates to a natural gas compressor cylinder oil composition, and also relates to a preparation method of the composition. Background Art

[0002] Reciprocating natural gas compressors are the most commonly used injection and pressure equipment in underground gas storage facilities. The key to lubricating oil is to prevent the end cylinder of the compressor from flushing, absorbing and diluting the lubricating oil with natural gas. Hydrocarbon gases (mainly methane) have similar polarity to oil-soluble polyether molecules. Hydrocarbon gases have greater solubility in this type of base oil and are easily soluble in oil-soluble polyether lubricating oil products under high temperature and high pressure conditions, causing the viscosity of the oil to decrease and the oil film to be weakened by flushing, resulting in the cylinder being unable to be effectively protected, resulting in increased cylinder wear. Ionic liquids are a type of "designable solvent" with extremely low vapor pressure, almost no volatility, and selective solubility.

[0003] A Chinese patent (application number: 201110455478.X, publication number: CN 103184089A) discloses a method for improving the anti-liquid alkane washing performance of polyether synthetic oil. By increasing the content of hydrophilic monomer ethylene oxide (water-soluble PAG) in the polyether of the base oil, the anti-liquid alkane washing ability of the polyether is improved, so that the finished oil has a strong anti-liquid alkane washing ability, prolongs the service life of the oil product, and ensures the use requirements of the hydrocarbon gas compressor system.

[0004] A Chinese patent (application number: 202110437722.3, publication number: CN113136257A) discloses a mixture for hydrocarbon gas synthetic compressor oil. The polyether base oil uses an ethylene oxide and propylene oxide chain molar ratio of 75%:25% (water-soluble PAG), which can provide good lubrication, sealing, cooling and other functions for the compressor, and has excellent resistance to dilution of light hydrocarbons, viscosity-temperature resistance, thermal oxidation stability and low carbon deposition tendency.

[0005] The above technologies all increase the ethylene oxide content in water-soluble PAG polyether base oil to increase the polarity of the base oil to resist the flushing and dilution of methane gas. There are no reports on using the gas selective absorption and separation properties of ionic liquids as additives in pure oily polyether base oils to improve the oil's resistance to alkane flushing and dilution. Summary of the invention

[0006] The object of the present invention is to provide a natural gas compressor cylinder oil composition, which has excellent anti-alkane dilution washing ability and lubricity.

[0007] Another object of the present invention is to provide a method for preparing the natural gas compressor cylinder oil composition.

[0008] The technical solution adopted by the present invention is that the natural gas compressor cylinder oil composition includes the following components in terms of mass percentage: 88.0-93.5% of oil-soluble PAG polyether base oil, 5.0-8.0% of ionic liquid, 1.5-3.5% of antioxidant, 0.03-0.1% of metal passivator, 0.05-0.12% of ashless extreme pressure anti-wear agent, 0.08-0.15% of rust inhibitor, and 0.005%-0.03% of anti-foaming agent, and the sum of the mass percentages of the above components is 100%.

[0009] The present invention is also characterized in that:

[0010] The structural formula of ionic liquid is as follows:

[0011]

[0012] The antioxidant is one or two of alkyl diphenylamine and naphthylamine.

[0013] The metal passivator is a liquid methylbenzotriazole derivative.

[0014] The ashless extreme pressure anti-wear agent is an ashless liquid dithiophosphate.

[0015] The rust inhibitor is liquid alkenyl succinic acid half fat.

[0016] The antifoaming agent is 1# compound antifoaming agent T921 or 2# compound antifoaming agent T922.

[0017] Another technical solution adopted by the present invention is a method for preparing a natural gas compressor cylinder oil composition, which is specifically as follows: first, add oil-soluble PAG polyether and ionic liquid into a blending kettle, heat to 40-45°C and stir for 0.5 hour, then add antioxidant, metal passivator, ashless extreme pressure anti-wear agent, rust inhibitor in sequence, heat to 60-65°C and stir for 2.0 hour, finally, add anti-foaming agent, stir at 60-65°C for 0.5 hour to obtain a natural gas compressor cylinder oil composition.

[0018] The beneficial effects of the present invention are as follows: the present invention selects pure oily PAG polyether as the base oil, supplemented with ionic liquid to improve the overall polarity of the oil product, so as to achieve the purpose of improving the oil product's resistance to natural gas dissolution and dilution performance, and at the same time adds antioxidants, anti-wear agents, metal passivators, rust inhibitors and anti-foaming agents to improve the oil product's antioxidant, anti-wear and anti-rust and anti-corrosion properties, thereby meeting the overall needs of equipment lubrication. DETAILED DESCRIPTION

[0019] The present invention is described in detail below with reference to specific embodiments.

[0020] The natural gas compressor cylinder oil composition of the present invention comprises the following components in percentage by mass: 88.0-93.5% of oil-soluble PAG polyether base oil, 5.0-8.0% of ionic liquid, 1.5-3.5% of antioxidant, 0.03-0.1% of metal passivator, 0.05-0.12% of ashless extreme pressure anti-wear agent, 0.08-0.15% of rust inhibitor, and 0.005%-0.03% of anti-foaming agent, and the sum of the percentages by mass of the above components is 100%.

[0021] Oil-soluble PAG polyether base oil has good viscosity-temperature performance, low-temperature fluidity, excellent high-temperature stability and lubricity;

[0022] Ionic liquids contain groups such as imidazole and phenoxyacetic acid, can be dissolved in oily PAG polyether base oil, and the polarity of the anion end can effectively resist methane dissolution, and have excellent compatibility with a variety of functional agents.

[0023] The structural formula of ionic liquid is as follows:

[0024]

[0025] The advantage of selecting ionic liquids of this structural type is that they are easily soluble in oily PAG polyethers, which helps to evenly disperse the polar ends in the oil, increase the polarity of the oil, and resist the dissolution of methane molecules. In addition, ionic liquids of this structural type also have auxiliary properties of rust and corrosion prevention.

[0026] The antioxidant is one or both of alkyl diphenylamine and naphthylamine, which has good antioxidant properties and can reduce the generation of piston ring deposits;

[0027] Metal passivator is a liquid methylbenzotriazole derivative that can form a protective film on the metal surface to prevent rust and corrosion, and also has certain wear reduction and anti-wear properties.

[0028] The ashless extreme pressure anti-wear agent is an ashless liquid dithiophosphate, which can exert better thermal stability in the polyether system, provide long-lasting anti-wear performance, is not easily decomposed and consumed, and exhibits good toughness.

[0029] The rust inhibitor is liquid alkenyl succinic acid half fat, which has good anti-rust and moisture-proof properties and protects the alloy surface.

[0030] The antifoaming agent is a composite antifoaming agent, specifically 1# composite antifoaming agent T921 or 2# composite antifoaming agent T922, which can take into account antifoaming properties, oil solubility, stability, etc., and has good compatibility with other additives.

[0031] The preparation method of the natural gas compressor cylinder oil composition of the present invention is specifically as follows: first, 88.0-93.5% of oil-soluble PAG polyether and 5.0-8.0% of ionic liquid are added into a blending kettle, the temperature is raised to 40-45°C and stirred for 0.5 hour, then 1.5-3.5% of antioxidant, 0.03-0.1% of metal passivator, 0.05-0.12% of ashless extreme pressure anti-wear agent, 0.08-0.15% of rust inhibitor are added in sequence, the temperature is raised to 60-65°C and stirred for 2.0 hours, and finally, 0.005%-0.03% of anti-foaming agent is added, and the mixture is stirred at 60-65°C for 0.5 hour to obtain the natural gas compressor cylinder oil composition.

[0032] The present invention uses oil-soluble PAG polyether base oil with ionic liquid and related functional additives and water-soluble PAG polyether base oil with related functional additives, and uses a self-built anti-alkane flushing test (RH02ZB.0011-2004, patent number CN103184089 A) The results are shown in Table 1 below:

[0033] Table 1 Test results of different formulations against alkane flushing

[0034]

[0035] Judging from the test results, the performance of the oil-soluble PAG combined with ionic liquid scheme and the water-soluble PAG scheme in the liquid alkane flushing resistance test is equivalent and can meet the standard requirements.

[0036] The natural gas compressor cylinder oil composition of the present invention is suitable for the exhaust cylinder end lubrication system of the natural gas unit of the high-pressure underground gas storage compressor. It has excellent resistance to alkane dilution and flushing, lubricity, thermal stability and other properties, meets the unique requirements for cylinder lubricating oil in the equipment operation manual, and ensures smooth movement of the equipment.

[0037] Example 1

[0038] The natural gas compressor cylinder oil composition of the present invention has a formulation as shown in Table 2 below:

[0039] Table 2 Composition and proportion of cylinder oil of natural gas compressor in Example 1

[0040]

[0041] The performance test of the natural gas compressor cylinder oil prepared in this embodiment is shown in Table 3.

[0042] Table 3 Performance data of natural gas compressor cylinder oil in Example 1

[0043]

[0044]

[0045]

[0046] From the data comparison in Table 3, it can be seen that the natural gas compressor cylinder oil composition of the present invention has good viscosity-temperature property, excellent anti-oxidation performance, the rotating oxygen bomb can reach more than 650min, and the anti-wear performance is also outstanding. In the evaluation of the key performance "anti-alkane flushing ability", a self-built method (RH02ZB.0011-2004, patent number CN 103184089 A) is used for quantitative comparison. The developed oil product is 7% higher than the competing product in this performance, proving that the formula design has better performance and can meet the lubrication needs of high-pressure natural gas compressor cylinders.

[0047] Example 2

[0048] The natural gas compressor cylinder oil composition of the present invention has a formulation as shown in Table 4 below:

[0049] Table 4 Composition and ratio of natural gas compressor cylinder oil composition in Example 2

[0050] name quality% Polyether base oil 92.0 Ionic Liquids 5.0 Alkyl diphenylamine 2.5 Liquid methylbenzotriazole derivatives 0.08 Ashless liquid dithiophosphate 0.1 Liquid alkenyl succinate hemiester 0.30 Composite antifoaming agent 0.02

[0051] Example 3

[0052] The natural gas compressor cylinder oil composition of the present invention has a formulation as shown in Table 5 below:

[0053] Table 5 Composition and proportion of natural gas compressor cylinder oil composition in Example 3

[0054] name quality% Polyether base oil 91.0 Ionic Liquids 6.5％ Alkyl diphenylamine 1.2 Naphthylamine 0.8 Liquid methylbenzotriazole derivatives 0.08 Ashless liquid dithiophosphate 0.1 Liquid alkenyl succinate hemiester 0.30 Composite antifoaming agent 0.02

[0055] The composition of the present invention selects an ionic liquid that is not easy to absorb methane gas as a lubricant additive in an oil-soluble PAG polyether base oil to improve the overall resistance of the lubricant to methane gas flushing and dilution, meet the lubrication requirements of the high-pressure compression end of the gas storage reservoir, and specifically quantitatively evaluate its anti-alkane flushing performance.

Claims

1. A natural gas compressor cylinder oil composition, characterized in that: The invention comprises the following components in percentage by mass: 88.0-93.5% of oil-soluble PAG polyether base oil, 5.0-8.0% of ionic liquid, 1.5-3.5% of antioxidant, 0.03-0.1% of metal passivator, 0.05-0.12% of ashless extreme pressure anti-wear agent, 0.08-0.15% of rust inhibitor, and 0.005%-0.03% of anti-foaming agent. The sum of the percentage by mass of the above components is 100%.

2. The natural gas compressor cylinder oil composition according to claim 1, characterized in that: The structural formula of the ionic liquid is as follows:

3. The natural gas compressor cylinder oil composition according to claim 1, characterized in that: The antioxidant is one or two of alkyl diphenylamine and naphthylamine.

4. The natural gas compressor cylinder oil composition according to claim 1, characterized in that: The metal passivator is a liquid methylbenzotriazole derivative.

5. The natural gas compressor cylinder oil composition according to claim 1, characterized in that: The ashless extreme pressure anti-wear agent is an ashless liquid dithiophosphate.

6. The natural gas compressor cylinder oil composition according to claim 1, characterized in that: The rust inhibitor is liquid alkenyl succinic acid half fat.

7. The natural gas compressor cylinder oil composition according to claim 1, characterized in that: The antifoaming agent is 1# composite antifoaming agent T921 or 2# composite antifoaming agent T922.

8. The method for preparing the natural gas compressor cylinder oil composition according to any one of claims 1 to 7, characterized in that: Specifically, first, add oil-soluble PAG polyether and ionic liquid into a blending kettle, heat to 40-45°C and stir for 0.5 hour, then add antioxidant, metal passivator, ashless extreme pressure anti-wear agent, rust inhibitor in sequence, heat to 60-65°C and stir for 2.0 hour, finally, add anti-foaming agent, stir at 60-65°C for 0.5 hour, and you can get a natural gas compressor cylinder oil composition.

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