Antioxidant as well as preparation method and application thereof

Abstract

The invention belongs to the field of lubricating oil additives, and particularly relates to an antioxidant as well as a preparation method and application thereof. The antioxidant at least comprises one of the following structures: R1, R2, R5 and R7 are all phenyl-containing alkyl groups and are positioned at para-position, ortho-position or two positions of amino groups; and R3, R4, R6 and R8 are all alkyl groups and are respectively connected to R1, R2, R5 and R7. The antioxidant disclosed by the invention has excellent oxidation resistance, and compared with a single amine antioxidant containing benzene ring olefin substituent, the antioxidant disclosed by the invention has better solubility; and compared with a single non-phenyl substituent amine type antioxidant, the amine type antioxidant has higher thermal stability.

Description

Technical Field

[0001] This invention belongs to the field of lubricating oil additives, specifically relating to an antioxidant, its preparation method, and its application. Background Technology

[0002] Antioxidants are a crucial class of lubricating oil additives, significantly improving the oxidation stability of oils, preventing spoilage and deterioration, and extending their service life. Currently, global antioxidant production ranks second only to detergents and dispersants and viscosity index improvers, and continues to maintain strong growth momentum. Amine-type antioxidants, in particular, are the most widely used type, effectively preventing oil oxidation as free radical scavenging antioxidants. The most common amine-type antioxidant is diphenylamine. Due to its strong toxicity, poor oil solubility, and photodegradation, diphenylamine's use is limited. Domestic and international researchers have improved upon these shortcomings by alkylating diphenylamine, developing products such as dioctyl diphenylamine, butyloctyl diphenylamine, and dinonyl diphenylamine. These products each possess unique properties, exhibiting not only excellent antioxidant performance but also being ashless and phosphorus-free, thus finding widespread application in internal combustion engine oils and turbine oils.

[0003] Chinese invention patent application CN105646232A discloses a method for preparing 4,4'-di(phenylisopropyl)diphenylamine. In the presence of activated clay as a catalyst, diphenylamine and α-methylstyrene are reacted at a temperature of 105-165℃ to produce crude 4,4'-di(phenylisopropyl)diphenylamine. After filtration, the crude product is recrystallized with a solvent, and then centrifuged, dried, pulverized, or granulated to obtain high-purity 4,4'-di(phenylisopropyl)diphenylamine. This solid particulate antioxidant is a commonly used antioxidant in rubber and plastics, but its solubility in oil is relatively limited.

[0004] Chinese invention patent application CN101020643A discloses a process for preparing nonyl diphenylamine by alkylation reaction. The process uses nonene and diphenylamine as raw materials and carries out alkylation reaction in the presence of aluminum trichloride as catalyst. After the reaction is completed, the product is purified by acid washing, alkali washing, water washing, decolorization, filtration and vacuum distillation to obtain liquid nonyl diphenylamine product.

[0005] Chinese invention patent application CN105777557A discloses an alkylation reaction of mixed amines, in which naphthylamine and aniline are mixed, and then a mixed olefin is added to carry out an alkylation reaction to obtain a mixed alkylation substitution product of mixed amines, which involves substitution at different positions on the raw materials.

[0006] The products described above all involve the substitution of a single olefin component or a mixture of olefins on an amine source. This invention provides a novel alkylated amine antioxidant. First, an olefin containing a benzene ring is alkylated onto aniline. Then, a second olefin undergoes further alkylation onto the phenyl group of the olefin containing the benzene ring. This structure exhibits better solubility compared to amine antioxidants with a single benzene-ring olefin substituent, and higher thermal stability compared to amine antioxidants with a single non-phenyl substituent. Currently, reports of such structures are rare. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides an antioxidant, its preparation method, and its applications. The antioxidant of this invention exhibits superior solubility and thermal stability, and is less prone to discoloration.

[0008] To achieve the above-mentioned objectives of this invention, the specific technical solution adopted by this invention is as follows:

[0009] An antioxidant, said antioxidant comprising at least one of the following structures:

[0010]

[0011] Among them, R1, R2, R5, and R7 are all alkyl groups containing phenyl groups, located at the para, ortho, or both positions of the amino group; R3, R4, R6, and R8 are all alkyl groups, and are attached to R1, R2, R5, and R7 respectively.

[0012] Preferably, the alkyl group containing phenyl is selected from one or more C8-C14 olefins.

[0013] Preferably, the alkyl group is selected from one or more C4-C14 olefins.

[0014] This invention also relates to a method for preparing the above-mentioned antioxidant, comprising the following steps:

[0015] (1) Mix the amine source and catalyst, add an olefin containing a benzene ring, react, and distill to obtain product 1;

[0016] (2) An olefin was added to product 1, the reaction was carried out, the catalyst was removed by filtration after cooling, and the antioxidant was obtained by distillation.

[0017] Preferably, the method for preparing the catalyst in step (1) includes the following steps:

[0018] S1. Add activated clay, alumina and silica gel to a mixed solution of trifluoroacetic acid and methanesulfonic acid, react and calcine to obtain solid substance 1;

[0019] S2. Mix solid substance 1 with a mixture of ferric chloride and copper chloride, add it to anhydrous ethanol and stir, dry it and then calcine it to obtain the catalyst.

[0020] More preferably, the mass ratio of activated clay, alumina and silica gel in step S1 is 6-8:1-3:1, and the volume ratio of trifluoroacetic acid and methanesulfonic acid is 1:0.8-1.2.

[0021] More preferably, the mass ratio of the total mass of the activated clay, alumina and silica gel in the mixed solution in step S1 is 1:2-10.

[0022] More preferably, the reaction temperature in step S1 is 60-120℃, the reaction time is 7-10h, the calcination temperature is 150-260℃, and the calcination time is 10-15h.

[0023] More preferably, the mass ratio of ferric chloride to copper chloride in step S2 is 1:0.8-1.2, and the mass ratio of solid substance 1 to the mixture of ferric chloride and copper chloride is 1:2-4.

[0024] More preferably, the stirring temperature in step S2 is 55-65℃, the stirring time is 4-8h, the calcination temperature is 280-350℃, and the calcination time is 6-12h.

[0025] Preferably, the amine source in step (1) is selected from one or both of N-phenylaniline and phenylnaphthylamine.

[0026] Preferably, the amount of catalyst added in step (1) is 10%-30% of the mass fraction of the amine source, and the molar ratio of the amine source to the olefin containing a benzene ring is 1:3-10.

[0027] Preferably, the olefin containing a benzene ring in step (1) is added under a nitrogen atmosphere, the reaction temperature is 100-180℃, and the reaction time is 3-15h.

[0028] Preferably, the molar ratio of the olefin in step (2) to the olefin containing a benzene ring in step (1) is 1-2:1.

[0029] Preferably, the reaction temperature in step (2) is 100-180℃, the reaction time is 5-13h, and the temperature after cooling is 50-70℃.

[0030] This invention also relates to the application of the above-mentioned antioxidants or antioxidants prepared by the above-mentioned methods in the preparation of lubricating oils or greases.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The antioxidant in this invention has excellent antioxidant properties and better solubility compared with single amine antioxidants containing benzene ring olefin substituents; and higher thermal stability compared with single non-phenyl substituent amine antioxidants.

[0033] (2) The initial decomposition temperature of the antioxidant in this invention is 352.55℃, and the complete decomposition temperature is as high as 392.63℃, indicating that the additive has good thermal stability and can meet the harsh operating environment of lubricating oil. Attached Figure Description

[0034] Figure 1 This is the mass spectrum of the antioxidant in Example 1;

[0035] Figure 2 This is the thermogravimetric diagram of the antioxidant in Example 1. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to specific embodiments. The following embodiments are not intended to limit the present invention, but only to illustrate the present invention. Unless otherwise specified, the experimental methods used in the following embodiments are generally performed under conventional conditions. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0037] Example 1

[0038] A method for preparing an antioxidant is as follows:

[0039] (1) Add 16.9g of N-phenylaniline and 2g of catalyst to a four-necked flask equipped with a condenser and a stirrer, purge the air with nitrogen, add 35.4g of 2-phenylpropene, heat to 130℃ and react for 10h, then distill to obtain product 1.

[0040] (2) Add 33.6g of diisobutylene to product 1, react at 150℃ for 8h, cool down to 70℃, filter off the catalyst, and distill off the excess olefin to obtain 58.2g of antioxidant.

[0041] The catalyst preparation steps are as follows: Commercially available activated clay, alumina, and silica gel are added to a mixed solution of trifluoroacetic acid and methanesulfonic acid in a mass ratio of 7:2:1. The total mass ratio of activated clay, alumina, and silica gel to the mixed acid is 1:5. The mixture is reacted at 100℃ for 8 hours, followed by calcination at 200℃ for 13 hours. The calcined solid is then mixed with a mixture of ferric chloride and copper chloride in a mass ratio of 1:3, added to anhydrous ethanol, and stirred at 60℃ for 6 hours. After the solvent is completely evaporated, the mixture is dried in an oven and then calcined at 320℃ for 8 hours to obtain the catalyst.

[0042] The mass spectrum of the antioxidant is as follows: Figure 1 As shown, the structure of this antioxidant is as follows:

[0043]

[0044] Example 2

[0045] A method for preparing an antioxidant is as follows:

[0046] (1) Add 16.9g of N-phenylaniline and 5.07g of catalyst to a four-necked flask equipped with a condenser and a stirrer, purge the air with nitrogen, add 35.4g of 2-phenylpropene, heat to 130℃ and react for 10h, then distill to obtain product 1.

[0047] (2) Add 33.6g of diisobutylene to product 1, react at 150℃ for 8h, cool down to 70℃, filter off the catalyst, and distill off the excess olefin to obtain 59.3g of antioxidant.

[0048] The catalyst preparation steps are as follows: Commercially available activated clay, alumina, and silica gel are added to a mixed solution of trifluoroacetic acid and methanesulfonic acid in a mass ratio of 7:2:1. The total mass ratio of activated clay, alumina, and silica gel to the mixed acid is 1:2. The mixture is reacted at 60℃ for 10 hours, followed by calcination at 150℃ for 15 hours. The calcined solid is then mixed with a mixture of ferric chloride and copper chloride in a mass ratio of 1:2, added to anhydrous ethanol, and stirred at 55℃ for 8 hours. After the solvent is completely evaporated, the mixture is dried in an oven and then calcined at 280℃ for 12 hours to obtain the catalyst.

[0049] Example 3

[0050] A method for preparing an antioxidant is as follows:

[0051] (1) Add 21.9g of phenylmethylnaphthylamine and 5.07g of catalyst to a four-necked flask equipped with a condenser and a stirrer, purge the air with nitrogen, add 35.4g of 2-phenylpropene, heat to 130℃ and react for 10h, then distill to obtain product 1;

[0052] (2) Add 33.6g of diisobutylene to product 1, react at 150℃ for 8h, cool down to 70℃, filter off the catalyst, and distill off excess olefins to obtain 62.4g of antioxidant.

[0053] The catalyst preparation steps are as follows: Commercially available activated clay, alumina, and silica gel are added to a mixed solution of trifluoroacetic acid and methanesulfonic acid in a mass ratio of 7:2:1. The total mass ratio of activated clay, alumina, and silica gel to the mixed acid is 1:10. The mixture is reacted at 120℃ for 7 hours, followed by calcination at 260℃ for 10 hours. The calcined solid is then mixed with a mixture of ferric chloride and copper chloride in a mass ratio of 1:4, added to anhydrous ethanol, and stirred at 65℃ for 4 hours. After the solvent is completely evaporated, the mixture is dried in an oven and then calcined at 350℃ for 6 hours to obtain the catalyst.

[0054] Example 4

[0055] A method for preparing an antioxidant is as follows:

[0056] (1) Add 16.9g of N-phenylaniline and 5.07g of catalyst to a four-necked flask equipped with a condenser and a stirrer, purge the air with nitrogen, add 59g of 2-phenylpropene, heat to 130℃ and react for 10h, then distill to obtain product 1.

[0057] (2) Add 56g of diisobutylene to product 1, react at 150℃ for 8h, cool down to 70℃, filter off the catalyst, and distill off excess olefin to obtain 78.2g of antioxidant.

[0058] The catalyst preparation steps are as follows: Commercially available activated clay, alumina, and silica gel are added to a mixed solution of trifluoroacetic acid and methanesulfonic acid in a mass ratio of 7:2:1. The total mass ratio of activated clay, alumina, and silica gel to the mixed acid is 1:10. The mixture is reacted at 120℃ for 7 hours, followed by calcination at 260℃ for 10 hours. The calcined solid is then mixed with a mixture of ferric chloride and copper chloride in a mass ratio of 1:4, added to anhydrous ethanol, and stirred at 65℃ for 4 hours. After the solvent is completely evaporated, the mixture is dried in an oven and then calcined at 350℃ for 6 hours to obtain the catalyst.

[0059] The structure of this antioxidant is as follows:

[0060]

[0061] Example 5

[0062] A method for preparing an antioxidant is as follows:

[0063] (1) Add 16.9g of N-phenylaniline and 5.07g of catalyst to a four-necked flask equipped with a condenser and a stirrer, purge the air with nitrogen, add 35.4g of 2-phenylpropene, heat to 130℃ and react for 10h, then distill to obtain product 1.

[0064] (2) Add 22.4g of diisobutylene and 11.2g of isobutylene to product 1, react at 150℃ for 8h, cool down to 70℃, filter off the catalyst, and distill off the excess olefin to obtain 51.2g of antioxidant.

[0065] The catalyst preparation steps are as follows: Commercially available activated clay, alumina, and silica gel are added to a mixed solution of trifluoroacetic acid and methanesulfonic acid in a mass ratio of 7:2:1. The total mass ratio of activated clay, alumina, and silica gel to the mixed acid is 1:2. The mixture is reacted at 60℃ for 10 hours, followed by calcination at 150℃ for 15 hours. The calcined solid is then mixed with a mixture of ferric chloride and copper chloride in a mass ratio of 1:2, added to anhydrous ethanol, and stirred at 55℃ for 8 hours. After the solvent is completely evaporated, the mixture is dried in an oven and then calcined at 280℃ for 12 hours to obtain the catalyst.

[0066] The structure of this antioxidant is as follows:

[0067]

[0068] Comparative Example 1

[0069] The only difference between this comparative example and Example 1 is that only one phenyl-containing alkane was added.

[0070] The preparation method is as follows: 16.9g of N-phenylaniline and 2g of catalyst were added to a four-necked flask equipped with a condenser and a stirrer. Nitrogen gas was introduced to replace the air, and then 35.4g of 2-phenylpropene was added. The temperature was raised to 130℃ and reacted for 10h. After cooling to 70℃, the catalyst was filtered off, and the excess olefin was distilled off to obtain 38.5g of product.

[0071] Comparative Example 2

[0072] The only difference between this comparative example and Example 1 is that only one phenyl-free olefin was added.

[0073] The preparation method is as follows: 16.9g of N-phenylaniline and 2g of catalyst were added to a four-necked flask equipped with a condenser and a stirrer. Nitrogen gas was introduced to replace the air, and 33.6g of diisobutylene was added. After reacting at 150℃ for 8 hours, the catalyst was filtered off, and the excess olefin was distilled off to obtain 34.2g of product.

[0074] Comparative Example 3

[0075] The only difference between this comparative example and Example 1 is that a phenyl-free olefin was added first, followed by a phenyl-containing olefin.

[0076] The preparation method is as follows:

[0077] (1) 16.9g of N-phenylaniline and 2g of catalyst were added to a four-necked flask equipped with a condenser and a stirrer. Nitrogen gas was introduced to replace the air, and 33.6g of diisobutylene was added. After reacting at 150℃ for 8h, product 1 was obtained by distillation.

[0078] (2) After cooling product 1 to 130℃, 35.4g of 2-phenylpropene was added and reacted for 10h. After cooling to 70℃, the catalyst was filtered off, and the excess olefin was distilled off to obtain 46.3g of product. The target substance was not obtained.

[0079] Effect test

[0080] Test Example 1: Stability / Solubility Test

[0081] The antioxidants from Example 1 and Comparative Example 1, as well as commercially available antioxidant 445 (diphenylamine containing only phenyl substituents), were added to YUBASE-6 base oil at a dosage of 2%. The oil was stored at different temperatures and observed for 15 days. The test results are shown in Table 1.

[0082] Table 1. Results of stability / solubility tests

[0083]

[0084]

[0085] Test Example 2: Oxidative Thermal Decomposition Temperature Test

[0086] Thermogravimetric analysis (TGA) was performed on Example 1, Comparative Example 2, and commercially available amine-type antioxidants (containing non-phenyl substituents). The test results are shown in Table 2. The antioxidant of Example 1 of this invention has the highest thermal decomposition initiation temperature and the highest thermal decomposition termination temperature, indicating that it can be used in high-temperature conditions. Thermogravimetric diagram is shown below. Figure 2 As shown.

[0087] Table 2 Thermogravimetric analysis results

[0088] Group Thermal decomposition initiation temperature / °C Thermal decomposition termination temperature / °C Example 1 352.55 392.63 Comparative Example 2 254.2 293.23 Commercially available L57 232.31 290.16 BASF L06 265.4 295.85

[0089] Test Example 3 Antioxidant Performance Test

[0090] The antioxidants from Examples 1 and 3-5 of this invention, as well as Comparative Examples 1-2 and commercially available antioxidants, were added to YUbase-6 at a dosage of 0.3% for oxidative stability testing (RPVOT method: refer to SH / T 0193-92; PDSC method: refer to ASTM D6168). The test results are shown in Table 3. Compared with commonly used antioxidants, the antioxidants of this invention exhibit excellent antioxidant properties.

[0091] Table 3 Results of antioxidant performance test

[0092] Group RPVOT / 150℃ / min PDSC / 180℃ / min Example 1 276 44 Example 3 423 82 Example 4 248 32 Example 5 256 36 Comparative Example 1 201 24 Comparative Example 2 206 26 Retail price 445 196 28 Commercially available L57 236 20

[0093] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. An antioxidant, characterized in that, The antioxidant comprises at least one of the following structures: Among them, R1, R2, R5, and R7 are all alkyl groups containing phenyl groups, located at the para, ortho, or both positions of the amino group; R3, R4, R6, and R8 are all alkyl groups, and are attached to R1, R2, R5, and R7 respectively.

2. The antioxidant according to claim 1, characterized in that, The alkyl group containing phenyl is selected from one or more C8-C14 olefins.

3. The antioxidant according to claim 1, characterized in that, The alkyl group is selected from one or more C4-C14 olefins.

4. A method for preparing the antioxidant according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Mix the amine source and catalyst, add an olefin containing a benzene ring, react, and distill to obtain product 1; (2) An olefin was added to product 1, the reaction was carried out, the catalyst was removed by filtration after cooling, and the antioxidant was obtained by distillation.

5. The preparation method according to claim 4, characterized in that, The preparation method of the catalyst in step (1) includes the following steps: S1. Add activated clay, alumina and silica gel to a mixed solution of trifluoroacetic acid and methanesulfonic acid, react and calcine to obtain solid substance 1; S2. Mix solid substance 1 with a mixture of ferric chloride and copper chloride, add it to anhydrous ethanol and stir, dry it and then calcine it to obtain the catalyst.

6. The preparation method according to claim 5, characterized in that, In step S1, the mass ratio of activated clay, alumina, and silica gel is 6-8:1-3:1, and the volume ratio of trifluoroacetic acid and methanesulfonic acid is 1:0.8-1.

2.

7. The preparation method according to claim 5, characterized in that, The mass ratio of the total mass of activated clay, alumina and silica gel in the mixed solution in step S1 is 1:2-10.

8. The preparation method according to claim 5, characterized in that, The reaction temperature in step S1 is 60-120℃, the reaction time is 7-10h, the calcination temperature is 150-260℃, and the calcination time is 10-15h.

9. The preparation method according to claim 5, characterized in that, In step S2, the mass ratio of ferric chloride to copper chloride is 1:0.8-1.2, and the mass ratio of solid substance 1 to the mixture of ferric chloride and copper chloride is 1:2-4.

10. The preparation method according to claim 5, characterized in that, The stirring temperature in step S2 is 55-65℃, the stirring time is 4-8h, the calcination temperature is 280-350℃, and the calcination time is 6-12h.

11. The preparation method according to claim 4, characterized in that, The amine source mentioned in step (1) is selected from one or both of N-phenylaniline and phenylnaphthylamine.

12. The preparation method according to claim 4, characterized in that, The amount of catalyst added in step (1) is 10%-30% of the mass fraction of the amine source, and the molar ratio of the amine source to the olefin containing a benzene ring is 1:3-10.

13. The preparation method according to claim 4, characterized in that, The olefin containing a benzene ring mentioned in step (1) is added under a nitrogen atmosphere, the reaction temperature is 100-180℃, and the reaction time is 3-15h.

14. The preparation method according to claim 4, characterized in that, The molar ratio of the olefin in step (2) to the olefin containing a benzene ring in step (1) is 1-2:

1.

15. The preparation method according to claim 4, characterized in that, The reaction temperature in step (2) is 100-180℃, the reaction time is 5-13h, and the temperature after cooling is 50-70℃.

16. The use of an antioxidant according to any one of claims 1-3 or an antioxidant prepared by any one of claims 4-15 in the preparation of lubricating oils or greases.

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