Preparation method and application of graphene composite lubricant

Abstract

The invention discloses a preparation method and application of a graphene composite lubricant, graphite, a strong oxidizing acid and a strong oxidant are mixed for oxidation reaction, after the reaction is completed, a reducing agent is added to terminate the oxidation reaction, the pH value of the solution is adjusted to be alkaline, then a metal oxide catalyst is added, oxygen-containing gas is blown in at the same time, and a composite material is obtained after the reaction. And cleaning the obtained composite material, and drying at high temperature to obtain the solid powder composite lubricant. The metal oxide catalyst is introduced in the preparation process, so that the reaction efficiency is improved, and the manganous-manganic oxide / graphene composite material with a more stable structure is formed.

Description

Technical Field

[0001] The present invention belongs to the technical field of lubricating materials, and particularly relates to a preparation method and application of a graphene composite lubricant. Background Art

[0002] In modern industrial production such as mining and metallurgy, the efficient and stable operation of mechanical equipment relies on high-quality lubricants and greases. When traditional lubricant greases are used to deal with complex working conditions, their lubricating performance, anti-wear ability and stability are often difficult to meet the requirements, resulting in shortened equipment life and increased maintenance time and labor costs.

[0003] In recent years, the rise of nanomaterials has brought new opportunities for improving the performance of lubricants. Graphene has excellent mechanical properties, ultra-high specific surface area, good chemical stability and lubricating performance, and can effectively reduce the friction coefficient. Manganese tetraoxide has a unique crystal structure with magnetism, can be adsorbed on the metal friction surface to form a protective film, and enhance the lubricating effect. By compounding the two to prepare a lubricant, the metal adsorption performance of magnetic manganese tetraoxide and the high-efficiency lubricating and anti-wear performance of graphene can be better exerted, playing a role of targeted lubrication, which can greatly extend the service life of equipment and reduce the equipment maintenance cost.

[0004] Chinese patent document CN 107805530 A discloses a graphene / manganese tetraoxide composite nano-lubricating additive and its synthesis method. Graphite is mixed with concentrated sulfuric acid and potassium permanganate with a high mass ratio and undergoes an oxidation reaction to obtain a mixed solution containing graphite oxide and / or graphene oxide; hydrogen peroxide is added to the mixed solution to reduce the unreacted potassium permanganate, and after dilution with water and ultrasonic treatment for a predetermined time, a graphene oxide mixed solution is obtained; the pH of the graphene oxide mixed solution is adjusted to alkaline, and manganese tetraoxide is obtained by reaction and loaded on graphene oxide, and the mixture is evaporated or filtered to obtain a solid product; the solid product is subjected to a reduction treatment at a high temperature to obtain a graphene / manganese tetraoxide composite product; the graphene / manganese tetraoxide composite product is washed and then ball-milled to obtain a graphene / manganese tetraoxide composite nano-lubricating additive. The reaction time for preparing the manganese tetraoxide / graphene composite lubricant is long and the reaction efficiency is low. Summary of the Invention

[0005] In order to overcome the problems in the prior art, the present invention provides a preparation method and application of a composite lubricant. A metal oxide catalyst is introduced during the preparation process, which improves the reaction efficiency and forms a more stable manganese tetraoxide / graphene composite material.

[0006] To solve the above technical problems, the technical solution proposed by the present invention is as follows:

[0007] The present invention provides a preparation method of a composite lubricant, comprising the following steps:

[0008] S1. Mix graphite, a strong oxidizing acid, and a strong oxidizing agent and conduct an oxidation reaction to obtain a mixture containing graphene oxide.

[0009] S2. Add a reducing agent to the mixture obtained in step S1 to terminate the oxidation reaction, and then adjust the pH of the solution to alkaline to obtain a reaction solution.

[0010] S3. Add a metal oxide catalyst to the reaction solution obtained in step S2, and simultaneously introduce an oxygen-containing gas. After the reaction, a composite material is obtained.

[0011] S4. Wash the composite material obtained in step S3 and then dry it at a high temperature to obtain a solid powder composite lubricant.

[0012] As an alternative embodiment, in the preparation method provided by the present invention, the metal oxide catalyst is selected from one or more of iron oxide, cobalt oxide, cerium oxide, and lanthanum oxide.

[0013] As an alternative embodiment, in the preparation method provided by the present invention, the addition amount of the metal oxide catalyst is 0.01-1% of the mass of the graphite in step S1.

[0014] As an alternative embodiment, in the preparation method provided by the present invention, the reaction time after adding the metal oxide catalyst is 0.5-2 h.

[0015] As an alternative embodiment, in the preparation method provided by the present invention, the metal oxide catalyst is dissolved in a solution and removed by washing after the reaction ends.

[0016] As an alternative embodiment, in the preparation method provided by the present invention, the oxygen content in the oxygen-containing gas is 20-30%.

[0017] As an alternative embodiment, in the preparation method provided by the present invention, the graphite is flake graphite or amorphous graphite.

[0018] As an alternative embodiment, in the preparation method provided by the present invention, the strong oxidizing acid is selected from one or more of concentrated sulfuric acid, concentrated nitric acid, and perchloric acid.

[0019] As an alternative embodiment, in the preparation method provided by the present invention, the strong oxidizing agent is potassium permanganate with a purity greater than 99%.

[0020] As an alternative embodiment, in the preparation method provided by the present invention, the reducing agent is selected from one or more of hydrogen peroxide, oxalic acid, and sodium sulfite.

[0021] As an alternative embodiment, in the preparation method provided by the present invention, in step S1, under a stirring state, graphite is infiltrated in a strong oxidizing acid, and then a strong oxidizing agent is added, and reacted for 1-2 h to obtain a strong oxidizing reaction system mixture, and the temperature during the reaction process is 10-30 °C.

[0022] As an alternative embodiment, in the preparation method provided by the present invention, in step S1, the strong oxidizing reaction system mixture is added to deionized water for reaction, the reaction temperature is 70-95 °C, the stirring speed is 80-120 r / min, and the reaction time is 60 min.

[0023] As an alternative embodiment, in the preparation method provided by the present invention, in step S4, the composite material is washed with deionized water, and then solid-liquid separation is performed, and the drying temperature is 105-1000 °C.

[0024] Based on the same technical concept, the present invention also provides the application of the composite lubricant obtained by the above preparation method in the preparation of grease, and the mass fraction of the composite lubricant in the grease is 0.01-2%.

[0025] As an alternative embodiment, in the application provided by the present invention, the grease further includes a base oil and a saponifying agent.

[0026] As an alternative embodiment, in the application provided by the present invention, the base oil is selected from one or more of mineral oil, synthetic oil, animal and vegetable oil, polyalpha-olefin, and ester oil; the saponifying agent is selected from one of sodium-based grease soap thickener, aluminum-based grease soap thickener, barium-based grease soap thickener, lithium-based grease soap thickener, polyurea-based soap thickener, calcium sulfonate-based soap thickener, composite soap thickener, and calcium-based soap thickener.

[0027] Furthermore, the grease further includes an extreme pressure anti-wear agent, an antioxidant or a rust inhibitor. The antioxidant is selected from one or more of diphenylamine, phenyl-α-naphthylamine, zinc dialkyldithiophosphate, and 4,4'-methylenebis(2,6-di-tert-butylphenol); the extreme pressure anti-wear agent is selected from one or two of molybdenum disulfide and phosphate ester; the rust inhibitor is selected from one or two of barium sulfonate and sodium nitrite.

[0028] In the present invention, various additives also need to be prepared according to the specific use of the base grease. The antioxidant can prevent the lithium-based grease from oxidizing and deteriorating during use; the extreme pressure anti-wear agent is used to improve the anti-wear performance of the lithium-based grease under high load; the rust inhibitor can prevent the metal surface from rusting.

[0029] Lithium soap is the key thickener for lithium-based greases, mainly formed by the reaction of fatty acids and lithium hydroxide. Calcium soap thickeners mainly consist of fatty acid calcium soaps, such as calcium stearate. Sodium soap thickeners are mainly fatty acid sodium soaps, such as sodium stearate. Sodium soap thickeners are mainly fatty acid sodium soaps, such as sodium stearate. Aluminum soap thickeners are generally fatty acid aluminum soaps, such as aluminum stearate. Barium soap thickeners use fatty acid barium soaps as the main thickeners, such as barium ricinoleate. Composite soap thickeners are composed of two or more metal soaps, and common ones include composite lithium-based soaps, composite calcium-based soaps, etc. Calcium sulfonate soap thickeners mainly consist of calcium sulfonate, and usually also contain some additives to improve performance. Polyurea-based soap thickeners are polyurea compounds formed by the reaction of isocyanates and amines.

[0030] As an alternative embodiment, in the application provided by the present invention, the preparation method of the grease includes the following steps:

[0031] (1) Put the base oil into the reaction kettle, heat it to 80 - 100 °C, then add the composite lubricant, and stir to obtain a mixture.

[0032] (2) Add the saponifying agent to the mixture, stir evenly, and then raise the temperature to 120 - 150 °C to carry out the saponification reaction.

[0033] (3) After the saponification reaction is completed, cool down to 80 - 100 °C, then add the antioxidant, extreme pressure anti-wear agent, and rust inhibitor, and continue to stir and react to obtain the grease.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) In the present invention, a catalyst is introduced, enabling manganese ions to rapidly undergo hydrolysis and oxidation-reduction reactions with graphene oxide in an aerobic and alkaline environment, improving the reaction efficiency and forming a manganese ferrite / graphene composite material with a stable structure and uniform particle size.

[0036] (2) The composite grease in the present invention can resist chemical reactions such as oxidation and hydrolysis, maintaining the stability of its lubricating performance. At the same time, additives such as antioxidants and rust inhibitors added act synergistically with the composite lubricant, further extending the service life of the grease and reducing the equipment maintenance and replacement costs caused by grease failure. In the high-temperature accelerated aging test, the time for the composite grease of the present invention to maintain stable lubricating performance at 150 °C is extended by 2 - 3 times compared to traditional greases.

[0037] (3) The introduction of the metal oxide catalyst in the present invention enables efficient large-scale production, reduces production costs, and is conducive to the wide application and promotion of the product.

[0038] (4) The composite lubricant in the present invention is applicable to various types of base oils and additive combinations. It can flexibly adjust the formula of the grease according to different usage scenarios and equipment requirements, and prepare high-performance greases that meet the requirements of various working conditions, such as high-temperature resistant greases applicable to high-temperature environments, low-noise greases applicable to high-speed rotating equipment, and rust-proof greases applicable to marine environments, etc., having broad market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0040] Figure 1 Electron microscopy test results of the composite lubricant prepared for Example 1;

[0041] Figure 2 Electron microscopy test results of the composite lubricant prepared for Comparative Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] For the convenience of understanding the present invention, the following will describe the present invention more comprehensively and meticulously in combination with the specification and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0043] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0044] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0045] Example 1

[0046] Preparation method of the composite lubricant, comprising the following steps:

[0047] (1) Mixing and preliminary reaction: In a low-temperature environment, 210 kg of earthy graphite is slowly added to 4000 L of sulfuric acid solution with a mass fraction of 98 wt%, the addition time is 0.5 hour, and the stirring speed is 120 r / min. Subsequently, 590 kg of potassium permanganate particles are slowly added to the mixed solution, the addition time is 2.5 hours, and continuous stirring is carried out.

[0048] (2) Oxidation reaction: Slowly add the above mixture to 10,000 L of deionized water over a period of 0.5 hours. Then, place the mixture in a water bath, control the temperature at 95 °C, maintain for 60 minutes, and the stirring speed is 100 r / min.

[0049] (3) Reaction termination and color change: Add 500 L of a 30 wt% hydrogen peroxide solution to the mixture at a uniform rate over a period of 45 minutes. After addition, continue stirring for 30 minutes.

[0050] (4) Adjust the pH value: Slowly add approximately 4000 kg of flaky KOH to the mixed solution, and use a pH meter to monitor the pH value of the solution in real-time. Stop adding KOH when the pH value is greater than 8.0.

[0051] (5) Catalytic reaction: Add 1 kg of the catalyst cerium oxide to the mixed solution, and the reaction time is 0.5 h. At the same time, introduce air. Manganese ions rapidly undergo hydrolysis and oxidation-reduction reactions with graphene oxide in an aerobic and alkaline environment to form a manganese tetraoxide / graphene composite material.

[0052] (6) Product separation and purification: Separate the solid and liquid of the manganese tetraoxide / graphene composite material using a filter press. Repeat the steps of dissolution, filtration, and washing three times to completely remove soluble impurities in the product. Finally, dry the manganese tetraoxide / graphene composite material at 105 °C for 1 hour to obtain a solid powder lubricant of the manganese tetraoxide / graphene nanocomposite material.

[0053] Example 2

[0054] A preparation method of a composite lubricant, comprising the following steps:

[0055] (1) Mixing and preliminary reaction: Slowly add 210 kg of flake graphite to 4000 L of a 98 wt% sulfuric acid solution at a low temperature environment over a period of 0.5 hours, and the stirring speed is 120 r / min. Subsequently, slowly add 590 kg of potassium permanganate particles to the mixed solution over a period of 2.5 hours while continuously stirring.

[0056] (2) Oxidation reaction: Slowly add the above mixture to 10,000 L of deionized water over a period of 3.5 hours. Then, place the mixture in a water bath, control the temperature at 95 °C, maintain for 60 minutes, and the stirring speed is 100 r / min.

[0057] (3) Reaction termination and color change: Add 500 L of a 30 wt% hydrogen peroxide solution to the mixture at a uniform rate over a period of 45 minutes. After addition, continue stirring for 30 minutes.

[0058] (4) Adjust the pH value: Slowly add approximately 4000 kg of flaky KOH to the mixed solution, and use a pH meter to monitor the pH value of the solution in real time. When the pH value is greater than 8.0, stop adding KOH.

[0059] (5) Catalytic reaction: Add 0.5 kg of cobalt oxide catalyst to the mixed solution, and at the same time introduce air. Manganese ions rapidly undergo hydrolysis and oxidation-reduction reactions with graphene oxide in an aerobic and alkaline environment. The reaction time is 2 h to form a manganese tetraoxide / graphene composite material.

[0060] (6) Product separation and purification: Separate the solid and liquid of the manganese tetraoxide / graphene composite material using a filter press. Repeat the steps of dissolution, filtration, and washing three times to completely remove soluble impurities in the product. Finally, dry the manganese tetraoxide / graphene composite material at 105 °C for 1 hour to obtain a solid powder lubricant of the manganese tetraoxide / graphene nanocomposite material.

[0061] Example 3

[0062] A preparation method of a composite lubricant, comprising the following steps:

[0063] (1) Mixing and preliminary reaction: Slowly add 210 kg of flake graphite to 4000 L of sulfuric acid solution with a mass fraction of 98 wt% in a low-temperature environment. The addition time is 0.5 h, and the stirring speed is 120 r / min. Subsequently, slowly add 590 kg of potassium permanganate particles to the mixed solution. The addition time is 2.5 h, and continuous stirring is maintained.

[0064] (2) Oxidation reaction: Slowly add the above mixture to 10000 L of deionized water. The addition time is 3.5 h. Then, place the mixture in a water bath, control the temperature at 95 °C, keep it for 60 minutes, and the stirring speed is 100 r / min.

[0065] (3) Reaction termination and color change: Add 500 L of a 30 wt% hydrogen peroxide solution to the mixture at a uniform rate. The addition time is 45 minutes. After addition, continue stirring for 30 minutes.

[0066] (4) Adjust the pH value: Slowly add approximately 4000 kg of flaky KOH to the mixed solution, and use a pH meter to monitor the pH value of the solution in real time. When the pH value is greater than 8.0, stop adding KOH.

[0067] (5) Catalytic reaction: Add 0.7 kg of lanthanum oxide catalyst to the mixed solution. The reaction time is 1 h, and at the same time introduce air. Manganese ions rapidly undergo hydrolysis and oxidation-reduction reactions with graphene oxide in an aerobic and alkaline environment to form a manganese tetraoxide / graphene composite material.

[0068] (6) Product separation and purification: The manganese tetraoxide / graphene composite material is subjected to solid-liquid separation using a filter press. This step of dissolution, filter pressing, and washing is repeated three times to completely remove soluble impurities in the product. Finally, the manganese tetraoxide / graphene composite material is dried at 105 °C for 1 hour to obtain a solid powder lubricant of the manganese tetraoxide / graphene nanocomposite material.

[0069] Comparative Example 1

[0070] The difference from Example 1 is that the catalyst cerium oxide is not used, and the remaining steps are the same as those in Example 1.

[0071] Comparing with the preparation method in Example 1, it can be seen that the reaction time is relatively long during the preparation process of Comparative Example 1, which takes 2 - 3 days, while the reaction can be completed within 0.5 - 2 hours with the addition of the catalyst in the example. The composite lubricants prepared in Example 1 and Comparative Example 1 are subjected to electron microscopy detection. In Comparative Example 1, the structure of the manganese tetraoxide / graphene composite material without the catalyst is a loose rod-like spherical structure, and the structure is as Figure 2 shown, and the lubricating effect as a lubricant is poor. In Example 1, the structure of the manganese tetraoxide / graphene composite material with the added catalyst is a dense flake-like spherical structure, and the structure is as Figure 1 shown, and it has excellent anti-wear and friction-reducing effects during the lubrication process.

[0072] Application Example

[0073] A method for preparing a grease, comprising the following steps:

[0074] (1) Castor oil is selected as the base oil, and 800 kg of castor oil is added to the reaction kettle and heated to 80 - 100 °C.

[0075] (2) 120 kg of fatty acid and 10 kg of lithium hydroxide are slowly added to the heated castor oil while stirring, so that the raw materials are fully mixed evenly. Under stirring conditions, the temperature of the materials in the reaction kettle is raised to 120 °C - 150 °C for saponification reaction. During the reaction process, the fatty acid reacts chemically with lithium hydroxide to form lithium fatty acid soap, which is the thickening agent of the lithium-based grease. The saponification reaction time is generally 2 h - 4 h, and the temperature is lowered to 80 - 100 °C.

[0076] (3) 5 kg of the prepared manganese tetraoxide / graphene composite lubricant, 10 kg of diphenylamine antioxidant, and 15 kg of barium sulfonate rust inhibitor are added, and the stirring speed is 600 r / min. They are added to the base oil containing additives, and stirring is continued for 1.5 hours, and the stirring speed is controlled at 400 r / min to form a manganese tetraoxide / graphene composite grease.

[0077] The tribological properties of the original lithium-based grease, the grease added with manganese tetraoxide / graphene prepared in Example 1, and the grease added with manganese tetraoxide / graphene prepared in Comparative Example 1 were detected using a four-ball friction and wear testing machine system, and the results are shown in Table 1 below:

[0078] Table 1: Tribological property test results

[0079] Addition amount of manganese tetraoxide / graphene Friction coefficient Wear scar diameter / μm 0 wt% 0.062 610 0.5 wt% (catalyst used in the preparation of Example 1) 0.031 316 0.5 wt% (catalyst not used in the preparation of Comparative Example 1) 0.046 428

[0080] As can be seen from Table 1, compared with the grease prepared using the composite lubricant prepared in Comparative Example 1, the grease prepared using the manganese tetraoxide / graphene composite material (adding a catalyst) prepared in Example 1 has a lower friction coefficient and a smaller wear scar diameter, and has excellent anti-wear and friction reduction effects during the lubrication process. The grease prepared using the composite lubricant in Comparative Example 1 has a higher friction coefficient and a larger wear scar diameter, and has a poorer lubrication effect as a lubricant.

[0081] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited only to these descriptions. For those of ordinary skill in the art to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A preparation method of a graphene composite lubricant, characterized in that, It includes the following steps: S1. Mix graphite, strong oxidizing acid and strong oxidant and carry out an oxidation reaction to obtain a mixture containing graphene oxide; S2. Add a reducing agent to the mixture obtained in step S1 to terminate the oxidation reaction, and then adjust the pH of the solution to alkaline to obtain a reaction solution; S3. Add a metal oxide catalyst to the reaction solution obtained in step S2, and at the same time introduce an oxygen-containing gas. After the reaction, a composite material is obtained; S4. Wash the composite material obtained in step S3 and dry it at high temperature to obtain a solid powder composite lubricant.

2. The preparation method of the composite lubricant according to claim 1, characterized in that, The metal oxide catalyst is selected from one or more of iron oxide, cobalt oxide, cerium oxide, and lanthanum oxide.

3. The preparation method of the composite lubricant according to claim 1, characterized in that, The addition amount of the metal oxide catalyst is 0.01-1% of the mass of graphite in step S2.

4. The preparation method of the composite lubricant according to claim 1, characterized in that The reaction time after adding the metal oxide catalyst is 0.5-2 h.

5. The preparation method of the composite lubricant according to claim 1, characterized in that, The metal oxide catalyst is dissolved in the solution and removed by washing after the reaction ends.

6. The preparation method of the composite lubricant according to claim 1, wherein The oxygen content in the oxygen-containing gas is 20-100%.

7. The preparation method of the composite lubricant according to claim 1, characterized in that, The graphite is flake graphite or earthy graphite; the strong oxidizing acid is selected from one or more of concentrated sulfuric acid, concentrated nitric acid, and perchloric acid; the strong oxidant is potassium permanganate with a purity greater than 99%; the reducing agent is selected from one or more of hydrogen peroxide, oxalic acid, and sodium sulfite.

8. Use of the composite lubricant obtained by the preparation method according to any one of claims 1-7 in the preparation of grease, characterized in that, The mass fraction of the composite lubricant in the grease is 0.01-2%.

9. The application according to claim 8, wherein The grease also includes a base oil and a saponifier; the base oil is selected from one or more of mineral oil, synthetic oil, animal and vegetable oil, polyalphaolefin, and ester oil; the saponifier is selected from one of sodium-based grease saponifier, aluminum-based grease saponifier, barium-based grease saponifier, lithium-based grease saponifier, polyurea-based grease saponifier, calcium sulfonate-based grease saponifier, composite soap saponifier, and calcium-based soap saponifier.

10. The application according to claim 8, wherein The preparation method of the grease includes the following steps: (1) Put the base oil into a reaction kettle, heat it to 80-100 °C, and then add the composite lubricant and stir to obtain a mixture; (2) Add the saponifier to the mixture, stir evenly, and then raise the temperature to 120-150 °C to carry out a saponification reaction; (3) After the saponification reaction is completed, lower the temperature to 80-100 °C, add an antioxidant, an extreme pressure anti-wear agent, and a rust inhibitor, and continue to stir and react to obtain the grease.

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