Antirust agent for methanol fuel as well as preparation method and application of antirust agent

Abstract

The invention belongs to the technical field of lubricating oil additives, and particularly relates to an antirust agent for methanol fuel as well as a preparation method and application thereof. The structural general formula of the antirust agent for the methanol fuel is shown as a formula (1), in the formula (1), R1 is aryl or aryl alkyl, R2 is C8-C12 aliphatic alkyl, n is 1-3, and m is 7-20. The raw materials used in the invention are nontoxic and harmless, chloride ions for promoting metal corrosion are not introduced, and the obtained antirust agent has no acid value and ash content, is easily soluble in methanol, and also has high-temperature oxidation resistance. (1).

Description

Technical Field

[0001] This invention belongs to the field of lubricating oil additive technology, specifically relating to a rust inhibitor for methanol fuel, its preparation method, and its application. Background Technology

[0002] The alternative use of renewable and environmentally friendly fuels can reduce dependence on petroleum and decrease exhaust emissions. Among the many liquid alternative fuels, methanol fuel has received considerable attention and importance. Both pure methanol and methanol-gasoline blends have been used to varying degrees in many countries. However, due to the unique properties of methanol fuel, problems such as corrosion, wear, and residue can occur during its use. To address these issues, functional additives such as rust inhibitors can be added to improve the performance of methanol fuel in vehicles.

[0003] Imidazolines and their derivatives, due to the high basicity of the nitrogen in their ring structure, can be converted into low-basic salts upon reaction with organic acids. These low-basic salts result in lower toxicity in marine environments, making them suitable for offshore oil extraction and natural gas production. However, due to their unique structure, imidazolines and their derivatives require chemical modification to increase molecular polarity and solubility when used in methanol fuels.

[0004] Chinese invention patent application CN113698350A discloses a method for preparing a high-efficiency imidazoline-type rust inhibitor, including the following steps: (1) Set up a water separation device, add weighed vegetable oleic acid to a four-necked flask, start stirring, and start heating under nitrogen protection. When the temperature reaches 100℃, start adding polyene polyamine dropwise to the reaction flask. When the temperature reaches 140-180℃, keep the reaction at this temperature for 3-6 hours; (2) Then continue heating to 180-260℃ and keep the reaction at this temperature for 3-6 hours. Stop the reaction and start cooling to obtain a pale yellow imidazoline derivative; (3) When the temperature drops to 60℃, add dodecenyl succinic anhydride to the reaction flask. During the process, control the reaction temperature to not exceed 125℃. When the temperature rises to 125℃, continue the reaction for 3-4 hours to obtain a high-efficiency imidazoline-type rust inhibitor with good oil solubility and excellent rust prevention performance. The highly efficient imidazoline-type rust inhibitor prepared by this method has excellent solubility in base oils of various viscosities, but it cannot be dissolved in methanol fuel.

[0005] Chinese invention patent application CN107385450A discloses a polyethylene glycol oleic acid imidazoline corrosion inhibitor and its preparation method. It introduces a polyethylene glycol segment into the oleic acid imidazoline structure, improving the water solubility of the oleic acid imidazoline by increasing molecular polarity. However, this preparation method uses polyethylene glycol, sodium hydroxide, and epichlorohydrin to prepare the intermediate product epoxy polyethylene glycol. First, epichlorohydrin is a hazardous chemical, flammable and toxic to humans during use, and is listed as a Group 2A carcinogen. Second, after preparing the intermediate product using this method, a large amount of chloride ions remain in the reaction system. Removing chloride ions is a major challenge for water-soluble rust inhibitors, and the presence of excessive chloride ions will affect the corrosion inhibition performance of the imidazoline derivative. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, the present invention aims to provide a rust inhibitor for methanol fuel, its preparation method, and its application. The rust inhibitor preparation method of the present invention uses non-toxic and harmless raw materials, produces a product free of chloride ion residue, and improves its solubility in methanol fuel by adjusting the degree of polymerization of the polyether segments.

[0007] This invention is achieved through the following technical solution: A rust inhibitor for methanol fuel, characterized in that its general structural formula is shown in formula (1): (1) Wherein, R1 is an aromatic group or an aromatic hydrocarbon group, R2 is a C8-C12 aliphatic hydrocarbon group, n is 1-3, and m is 7-20.

[0008] This invention also relates to a method for preparing the above-mentioned rust inhibitor for methanol fuel, comprising the following steps: (1) Mix aromatic carboxylic acids with polyene polyamines and react them at elevated temperature to obtain imidazoline derivative intermediates; (2) After cooling the imidazoline intermediate, add alcohol ether carboxylic acid and react to obtain the rust inhibitor for methanol fuel.

[0009] Preferably, the aromatic carboxylic acid in step (1) is selected from any one of benzoic acid, phenylacetic acid, phenylpropionic acid, naphthoic acid and naphthaleneacetic acid.

[0010] Preferably, the polyene polyamine in step (1) is selected from any one of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0011] Preferably, the molar ratio of the aromatic carboxylic acid to the polyene polyamine in step (1) is 0.8-1.05:1.

[0012] Preferably, step (1) includes two heating reactions: the first heating is to 140℃-160℃ and the reaction is to 1-3h, and the second heating is to 200℃-240℃ and the reaction is to 4-8h.

[0013] Preferably, the molar ratio of the imidazoline intermediate to the alcohol ether carboxylic acid in step (2) is 1.0-1.2:1.

[0014] Preferably, the number of ethoxy groups in the alcohol ether carboxylic acid described in step (2) is 5-12. When it is less than 5, it is an oil-soluble product; when it is more than 12, it is a water-soluble product.

[0015] Preferably, the number of alkane carbon atoms in the alcohol ether carboxylic acid described in step (2) is 8-12.

[0016] Preferably, the temperature after cooling in step (2) is 130℃-150℃, and the reaction time is 3-5h.

[0017] Preferably, step (2) further includes a vacuum distillation step after the reaction.

[0018] This invention also relates to the application of the rust inhibitor for methanol fuel prepared by the above-mentioned method in methanol fuel.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The rust inhibitor preparation method of the present invention uses non-toxic and harmless raw materials, does not introduce chloride ions that promote metal corrosion, and the resulting imidazoline derivative has no acid value, no ash content, is easily soluble in methanol, and also has high-temperature antioxidant properties. Attached Figure Description

[0020] Figure 1 This is the 1H NMR spectrum of the rust inhibitor for methanol fuel in Example 1 of this invention; Figure 2 This is the 1H NMR spectrum of the rust inhibitor for methanol fuel in Example 2 of this invention; Figure 3 This is the 1H NMR spectrum of the rust inhibitor for methanol fuel in Example 3 of this invention. Detailed Implementation

[0021] 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.

[0022] Emulsogen COL 070, brand: Clariant; Alcohol ether carboxylic acid AEC-9H, product number S11402115, was purchased from Shandong Yousuo Chemical Technology Co., Ltd. Emulsogen COL 100, brand: Clariant.

[0023] Example 1 A method for preparing a rust inhibitor for methanol fuel, comprising the following steps: (1) Add 97g benzoic acid and 103g diethylenetriamine to the reactor, heat to 140℃ and react for 3 hours, then heat to 200℃ and react for 8 hours to obtain an imidazoline derivative intermediate. The structure of the imidazoline derivative intermediate is shown in formula (2). (2) (2) After cooling the imidazoline derivative intermediate to 130℃, 552g of alcohol ether carboxylic acid COL 070 was added, and the reaction was maintained at 130℃ for 5 hours. After the reaction was completed, the product was distilled under reduced pressure to obtain a rust inhibitor for methanol fuel, the structure of which is shown in formula (3). The product yield was 96.1%. The product structure was tested by Fourier transform infrared spectroscopy, mass spectrometry, and nuclear magnetic resonance spectroscopy, and the product purity was tested by liquid chromatography. According to the analysis, the infrared spectrum (KBr pellet) was as follows: at a wavenumber of 1617 cm⁻¹ -1 The absorption peak is the stretching vibration peak of the C=N double bond on the imidazoline ring, at a wavenumber of 1635 cm⁻¹. -1 The absorption peak is the stretching vibration peak of the amide, at a wavenumber of 1600 cm⁻¹. -1 The absorption peak is a characteristic peak of the benzene ring, at a wavenumber of 1109 cm⁻¹. -1 The absorption peak is the stretching vibration peak of the ethoxy group; ESI-MS mass spectrometry: molecular ion peak [M] = 724.0; 1H NMR spectrum as follows: Figure 1 As shown in the figure, integration of the liquid chromatogram reveals a product purity of 99.3%.

[0024] (3) Example 2 A method for preparing a rust inhibitor for methanol fuel, comprising the following steps: (1) Add 142 g of phenylacetic acid and 146 g of triethylenetetramine to the reactor, heat to 160°C and react for 1 hour, then heat to 240°C and react for 4 hours to obtain an imidazoline derivative intermediate. The structure of the imidazoline derivative intermediate is shown in formula (4). (4) (2) After cooling the imidazoline derivative intermediate to 150℃, 533g of alcohol ether carboxylic acid AEC-9H was added, and the reaction was maintained at 150℃ for 3 hours. After the reaction was completed, the product was distilled under reduced pressure to obtain a rust inhibitor for methanol fuel, the structure of which is shown in formula (5). The product yield was 97.5%. The product structure was tested by Fourier transform infrared spectroscopy, mass spectrometry, and nuclear magnetic resonance spectroscopy, and the product purity was tested by liquid chromatography. The infrared spectrum (KBr pellet) was as follows: at a wavenumber of 1615 cm⁻¹ -1 The absorption peak is the stretching vibration peak of the C=N double bond on the imidazoline ring, at a wavenumber of 1635 cm⁻¹. -1 The absorption peak is the stretching vibration peak of the amide, at a wavenumber of 1600 cm⁻¹. -1 The absorption peak is a characteristic peak of the benzene ring, at a wavenumber of 1109 cm⁻¹. -1 The absorption peak is the stretching vibration peak of the ethoxy group; ESI-MS mass spectrometry: molecular ion peak [M] = 869.2; 1H NMR spectrum as follows: Figure 2 As shown in the figure, integration of the liquid chromatogram reveals a product purity of 99.5%.

[0025] (5) Example 3 A method for preparing a rust inhibitor for methanol fuel, comprising the following steps: (1) Add 150 g of phenylpropionic acid and 189 g of tetraethylenepentamine to the reactor, heat to 150°C and react for 2 hours, then heat to 220°C and react for 6 hours to obtain an imidazoline derivative intermediate. The structure of the imidazoline derivative intermediate is shown in formula (6). (6) (2) After cooling the imidazoline derivative intermediate to 140℃, 572 g of alcohol ether carboxylic acid COL 100 was added, and the reaction was maintained at 140℃ for 4 hours. After the reaction was completed, the product was distilled under reduced pressure to obtain a rust inhibitor for methanol fuel, the structure of which is shown in formula (7). The product yield was 95.8%. The product structure was tested by Fourier transform infrared spectroscopy, mass spectrometry, and nuclear magnetic resonance spectroscopy, and the product purity was tested by liquid chromatography. According to the analysis, the infrared spectrum (KBr pellet) was as follows: at a wavenumber of 1615 cm⁻¹ -1 The absorption peak is the stretching vibration peak of the C=N double bond on the imidazoline ring, at a wavenumber of 1634 cm⁻¹. -1 The absorption peak is the stretching vibration peak of the amide, at a wavenumber of 1600 cm⁻¹. -1 The absorption peak is a characteristic peak of the benzene ring, at a wavenumber of 1110 cm⁻¹. -1 The absorption peak is the stretching vibration peak of the ethoxy group; ESI-MS mass spectrometry: molecular ion peak [M] = 914.2; 1H NMR spectrum is attached. Figure 3 As shown in the figure, integration of the liquid chromatogram reveals a product purity of 99.6%.

[0026] (7) Comparative Example 1 The difference between this comparative example and Example 1 is that the aromatic carboxylic acid in step (1) is phenylbutyric acid, and the steps are as follows: (1) Add 130 g of phenylbutyric acid and 103 g of diethylenetriamine to the reactor, heat to 140°C and react for 3 hours, then heat to 200°C and react for 8 hours to obtain an imidazoline derivative intermediate.

[0027] (2) After cooling the imidazoline derivative intermediate to 130°C, add 552g of alcohol ether carboxylic acid COL 070 and maintain the reaction at 130°C for 5 hours. After the reaction is completed, distill under reduced pressure to obtain the rust inhibitor for methanol fuel.

[0028] Comparative Example 2 The difference between this comparative example and Example 1 is that, referring to Chinese invention patent application CN113698350A, a rust inhibitor was prepared using dodecenylsuccinic acid as a raw material in step (2). The preparation method steps are as follows: (1) Add 97g benzoic acid and 103g diethylenetriamine to the reactor, heat to 140℃ and react for 3 hours, then heat to 200℃ and react for 8 hours to obtain an imidazoline derivative intermediate. The structure of the imidazoline derivative intermediate is shown in formula (1).

[0029] (2) After cooling the imidazoline derivative intermediate to 130°C, add 284g of dodecenyl succinic acid and maintain the reaction at 130°C for 5 hours. After the reaction is completed, distill under reduced pressure to obtain the rust inhibitor for methanol fuel.

[0030] Comparative Example 3 The difference between this comparative example and Example 1 is that the reaction temperature in step (2) is 120°C, and the steps are as follows: (1) Add 97g benzoic acid and 103g diethylenetriamine to the reactor, heat to 140℃ and react for 3 hours, then heat to 200℃ and react for 8 hours to obtain an imidazoline derivative intermediate. The structure of the imidazoline derivative intermediate is shown in formula (1).

[0031] (2) After cooling the imidazoline derivative intermediate to 130°C, add 552g of alcohol ether carboxylic acid COL 070 and keep the reaction at 120°C for 5 hours. After the reaction is completed, distill under reduced pressure to obtain the rust inhibitor for methanol fuel.

[0032] Comparative Example 4 The difference between this comparative example and Example 1 is that the molar ratio of the imidazoline intermediate to the alcohol ether carboxylic acid in step (2) is 1.4:1, and the steps are as follows: (1) Add 97g benzoic acid and 103g diethylenetriamine to the reactor, heat to 140℃ and react for 3 hours, then heat to 200℃ and react for 8 hours to obtain an imidazoline derivative intermediate. The structure of the imidazoline derivative intermediate is shown in formula (1).

[0033] (2) After cooling the imidazoline derivative intermediate to 130°C, add 394 g of alcohol ether carboxylic acid COL 070 and keep the reaction at 120°C for 5 hours. After the reaction is completed, distill under reduced pressure to obtain the rust inhibitor for methanol fuel.

[0034] Comparative Example 5 The difference between this comparative example and Example 1 is that the molar ratio of the imidazoline intermediate to the alcohol ether carboxylic acid in step (2) is 0.8:1, and the steps are as follows: (1) Add 97g benzoic acid and 103g diethylenetriamine to the reactor, heat to 140℃ and react for 3 hours, then heat to 200℃ and react for 8 hours to obtain an imidazoline derivative intermediate. The structure of the imidazoline derivative intermediate is shown in formula (1).

[0035] (2) After cooling the imidazoline derivative intermediate to 130°C, add 690 g of alcohol ether carboxylic acid COL 070 and keep the reaction at 120°C for 5 hours. After the reaction is completed, distill under reduced pressure to obtain the rust inhibitor for methanol fuel.

[0036] Performance testing Test Example 1 To verify the performance of the methanol fuel rust inhibitor of the present invention, the methanol fuel rust inhibitors formed in Example 1 and Comparative Examples 1-5 were added to methanol at 0.5% (mass fraction). First, the solubility performance was observed, and then a copper strip corrosion test was conducted in accordance with GB / T 5096-2017 "Petroleum Products Copper Strip Corrosion Test Method". The results are shown in Table 1.

[0037] Table 1 Solubility

[0038] As shown in Table 1, the rust inhibitors prepared in Example 1 and Comparative Example 5 have good solubility in methanol, but Comparative Example 5 has poor copper corrosion inhibition performance. The rust inhibitors prepared in Comparative Examples 1-4 are difficult to dissolve in methanol, and their copper corrosion inhibition performance is also poor. This is because the difference between Comparative Example 1 and Example 1 is that the aromatic carboxylic acid in step (1) is phenylbutyric acid, which leads to the growth of the alkane chain in the rust inhibitor structure, reducing the polarity of the product, and thus decreasing its solubility in polar solvents. The difference between Comparative Example 2 and Example 1 is that, referring to Chinese invention patent application CN113698350A, the rust inhibitor is prepared using dodecenylsuccinic acid as a raw material in step (2). The imidazoline derivative prepared by Comparative Example 2 is an oil-soluble rust inhibitor and cannot be dissolved in polar solvents. The difference between Comparative Example 3 and Example 1 is that the reaction temperature in step (2) is 120°C. As the reaction temperature decreases, the imidazoline derivative intermediate and the alcohol ether carboxylic acid cannot react sufficiently, and the unreacted imidazoline derivative cannot dissolve in polar solvents. The difference between Comparative Examples 4 and 5 and Example 1 is that the molar ratio of the imidazoline intermediate to the alcohol ether carboxylic acid is different in step (2). When the molar ratio is less than 1:1, the alcohol ether carboxylic acid is in excess. Although the solubility of the product in methanol is not affected, it reduces the effective component of the rust inhibitor, thereby affecting the corrosion inhibition performance. When the molar ratio is greater than 1:1, the imidazoline derivative intermediate is in excess, and the excess imidazoline derivative will affect the solubility of the product in methanol.

[0039] Test Example 2 To further verify the performance of the methanol fuel rust inhibitor of the present invention, the commercially available imidazoline derivative product heptadecenylimidazoline quaternary ammonium salt (Wuhan Camike Technology Co., Ltd.), the rust inhibitors prepared in Comparative Example 2, and Examples 1-3 were evaluated. The specific schemes are as follows: The rust inhibitors prepared by heptadecenyl imidazoline quaternary ammonium salt, Comparative Example 2, and Examples 1-3 were applied to Kunlun M100 methanol fuel additive, replacing part of the rust and corrosion inhibitors in the original formulation. The rust and corrosion inhibitory performance of the imidazoline derivative of the present invention in methanol fuel was investigated. The formed M100 methanol fuel additive was added to methanol at 0.5% (mass fraction). First, the solubility was observed. Then, according to Appendix A (Metal Corrosion Test Glassware Method) of GB / T 34548-2017 "Methanol Gasoline Additives for Vehicles", various rust tests were carried out on test pieces. The smaller the change value of the test piece, the better the rust prevention performance. The test results are shown in Table 2.

[0040] Table 2 Rust and Corrosion Prevention Performance Tests

[0041] Table 2 shows that the Kunlun M100 methanol fuel additive is clear and transparent after being added to methanol. The methanol fuel additive formed after introducing the rust inhibitors prepared in Examples 1-3 also remains clear and transparent in methanol. However, the formulation containing the rust inhibitor prepared in Comparative Example 2 and heptadecenyl imidazoline quaternary ammonium salt precipitates, indicating that the imidazoline derivative of this invention has good solubility in methanol after modification. Rust tests show that after introducing the rust inhibitors prepared in Examples 1-3, the methanol fuel additive maintains the same rust and corrosion prevention performance as the Kunlun M100 methanol fuel additive, and the change value of the test pieces in methanol meets the requirements of GB / T 34548-2017. However, Comparative Example 2 and heptadecenyl imidazoline quaternary ammonium salt cannot dissolve in methanol, resulting in insufficient rust and corrosion prevention performance of the methanol fuel additive.

[0042] Thermogravimetric analysis was performed on the rust inhibitors prepared in Examples 1-3 and Comparative Example 2, and the results are shown in Table 3. The table shows that, compared to heptadecenyl imidazoline, the rust inhibitor of the present invention exhibits significantly improved thermal stability and is suitable for application under higher temperature conditions.

[0043] Table 3 Thermogravimetric Analysis

[0044] The rust inhibitors prepared in Examples 1-3 and Comparative Example 2 were added to Kunlun KE3028 polyol ester base oil at 0.15% (mass fraction). The static antioxidant properties of the samples were investigated by high-temperature red line oxidation test at 175℃. The changes in acid value of the lubricating oil samples during the test are shown in Table 4.

[0045] Table 4. Acid value of oil products in high-temperature oven test (mg KOH / g)

[0046] As shown in Table 4, after adding the rust inhibitor of Comparative Example 2 to KE3028 and conducting a high-temperature oxidation test, the increase in oil acid value was the same as that of the blank sample, indicating that the rust inhibitor of Comparative Example 2 had no antioxidant properties. After adding KE3028 to the rust inhibitors prepared in Examples 1-3, the increase in oil acid value after 72 hours of oxidation testing was all less than 290%, far less than the 780% increase in the blank sample. This indicates that the rust inhibitors prepared in Examples 1-3 have certain antioxidant properties.

[0047] 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. A rust inhibitor for methanol fuel, characterized in that, The general structural formula is shown in equation (1): （1） Wherein, R1 is an aromatic group or an aromatic hydrocarbon group, R2 is a C8-C12 aliphatic hydrocarbon group, n is 1-3, and m is 7-20.

2. A method for preparing the rust inhibitor for methanol fuel according to claim 1, characterized in that, Includes the following steps: (1) Mix aromatic carboxylic acids with polyene polyamines and react them at elevated temperature to obtain imidazoline derivative intermediates; (2) After cooling the imidazoline intermediate, add alcohol ether carboxylic acid and react to obtain the rust inhibitor for methanol fuel.

3. The preparation method according to claim 2, characterized in that, The aromatic carboxylic acid mentioned in step (1) is selected from one of benzoic acid, phenylacetic acid, phenylpropionic acid, naphthoic acid and naphthaleneacetic acid.

4. The preparation method according to claim 2, characterized in that, The polyene polyamine mentioned in step (1) is selected from any one of diethylenetriamine, triethylenetetramine and tetraethylenepentamine.

5. The preparation method according to claim 2, characterized in that, The molar ratio of aromatic carboxylic acid to polyene polyamine in step (1) is 0.8-1.05:

1.

6. The preparation method according to claim 2, characterized in that, Step (1) includes two heating reactions. The first heating is to 140℃-160℃ and the reaction is carried out for 1-3 hours. The second heating is to 200℃-240℃ and the reaction is carried out for 4-8 hours.

7. The preparation method according to claim 1, characterized in that, The molar ratio of the imidazoline intermediate to the alcohol ether carboxylic acid in step (2) is 1.0-1.2:

1.

8. The preparation method according to claim 2, characterized in that, The temperature after cooling in step (2) is 130℃-150℃, and the reaction time is 3-5h.

9. The preparation method according to claim 2, characterized in that, Step (2) includes a vacuum distillation step after the reaction.

10. The application of a rust inhibitor for methanol fuel prepared by the method according to any one of claims 2-9 in methanol fuel.

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