Functional L-proline-based bis-Schiff base corrosion inhibitor as well as preparation method and application thereof
By reacting L-proline with sodium hydroxide and terephthalaldehyde, a functionalized L-proline-based bischiff base corrosion inhibitor was prepared, which solved the problem of poor effect of existing corrosion inhibitors at low concentrations and achieved efficient metal corrosion inhibition.
Patent Information
- Application Number
- CN202510189941.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-20
- Publication Date
- 2025-06-06
AI Technical Summary
The existing Double Schiff alkali corrosion inhibitor has poor corrosion inhibition effect at low concentrations, and there are very few reports of preparation methods using L-proline as the nitrogen source.
Functionalized L-proline and sodium hydroxide were prepared by dissolving L-proline and sodium hydroxide in ethanol solution, and then adding terephthalaldehyde in ethanol solution dropwise, and performing nucleophilic addition reaction.
This corrosion inhibitor has a significant corrosion inhibiting effect, can better inhibit metal corrosion, the corrosion inhibition efficiency reaches 96.96%, and the preparation process is simple.
Smart Images
Figure CN120097884A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of corrosion inhibitor synthesis, and in particular to a functionalized L-proline-based bis-Schiff base corrosion inhibitor and a preparation method and application thereof. Background Art
[0002] Since the 20th century, the corrosion inhibitor anti-corrosion method has been widely used in petrochemical, marine engineering and other industries. The corrosion inhibitor anti-corrosion method has the advantages of low cost, simple process and excellent anti-corrosion effect. Among them, the -C=N- functional group of Schiff base has good stability and excellent coordination ability. The surface of carbon steel is due to the H in the acidic solution. + The adsorption of Cl - Physical adsorption occurs on the carbon steel surface through Coulomb force; chemical adsorption occurs due to the presence of electron-rich N atoms and aromatic rings in the Schiff base structure.
[0003] There are four methods for synthesizing double Schiff base corrosion inhibitors, generally the drop-by-drop method. The first is the direct synthesis method, in which aldehydes and amines are directly mixed and reacted in a certain proportion. This method has a high yield, but there are more side reactions and the product treatment is more complicated. The second is the step-by-step reaction method, in which a fresh Schiff base solution is first made and then a metal salt is added. This method can reduce the formation of by-products by controlling the reaction conditions. The third is the template synthesis method, which is suitable for situations where the reactant activity is low or the product is unstable. Metal ions are used as templates to improve the yield and conversion rate, and are easy to separate and purify. The fourth is the drop-by-drop method, in which the amine compound is first mixed with the metal ion solution, and then the aldehyde or ketone solution is added dropwise, and stirred vigorously to form a complex.
[0004] Currently reported double Schiff base corrosion inhibitors include salicyl phthalic acid imide, N,N'-disalicylicyl-1,2-phthalimide, etc., which have poor corrosion inhibition effect at low concentrations. However, there are very few reports on the preparation of double Schiff base corrosion inhibitors using L-proline as a nitrogen source. Therefore, it is of great research significance and market value to develop a carbon dot corrosion inhibitor that uses green raw material L-proline as a nitrogen source, has a simple preparation process, and has excellent corrosion inhibition performance. Summary of the invention
[0005] The first object of the present invention is to provide a functionalized L-proline-based bis-Schiff base corrosion inhibitor, which has excellent corrosion inhibition performance.
[0006] The second object of the present invention is to provide a method for preparing a functionalized L-proline-based bis-Schiff base corrosion inhibitor, which has a simple preparation process.
[0007] The present invention provides a method for preparing a functionalized L-proline-based bis-Schiff base corrosion inhibitor, comprising the following steps:
[0008] S1. Take L-proline and sodium hydroxide, dissolve them in ethanol solution, heat them in an oil bath and stir them to dissolve to form solution A;
[0009] S2. Add terephthalaldehyde ethanol solution dropwise to solution A, continue heating and stirring for nucleophilic addition reaction, and prepare an L-proline-based bis-Schiff base;
[0010] S3. After cooling the L-proline-based bis-Schiff base obtained in step S2 to room temperature, the L-proline-based bis-Schiff base is removed from the mixture and dried to obtain a functionalized L-proline-based bis-Schiff base corrosion inhibitor.
[0011] Preferably, the mass ratios of L-proline, sodium hydroxide and terephthalaldehyde in step S1 and step S2 are 1-2.5, 0.2-0.4 and 0.5-1.25.
[0012] Preferably, in step S1, the mass volume ratio of L-proline to ethanol is (1-2.5) g: (25-50) ml.
[0013] Preferably, the mass volume ratio of terephthalaldehyde to ethanol in the ethanol solution of terephthalaldehyde in step S2 is (0.5-1.25) g: (50-100) ml.
[0014] Preferably, the temperature of the oil bath in step S1 is 36-38°C.
[0015] Preferably, the heating and stirring time in step S2 is 6 to 8 hours.
[0016] Preferably, the specific steps of removing impurities in step S3 are: washing the L-proline-based bis-Schiff base with ethanol for multiple times, and performing centrifugal separation after each washing to complete the impurity removal.
[0017] Preferably, the specific steps of drying in step S3 are: air-drying under natural conditions for 2 to 3 days to complete drying.
[0018] The present invention also provides a functionalized L-proline-based bis-Schiff base corrosion inhibitor prepared by the above preparation method.
[0019] The above-mentioned functionalized L-proline-based bis-Schiff base corrosion inhibitor is used in the field of preventing corrosion of Q235 carbon steel materials.
[0020] Beneficial effects:
[0021] The functionalized L-proline-based bis-Schiff base corrosion inhibitor of the present invention has nitrogen, oxygen and benzene ring adsorption sites, and can provide lone electron pairs to form coordination bonds with iron atoms, so that the corrosion inhibitor molecules are better adsorbed on the metal surface and the corrosion process is slowed down.
[0022] Compared with other double Schiff base corrosion inhibitors, the functionalized L-proline-based double Schiff base corrosion inhibitor of the present invention has a more significant corrosion inhibition effect and can better inhibit metal corrosion. This shows that the functionalized L-proline-based double Schiff base corrosion inhibitor has a stronger adsorption capacity and can better coordinate with the metal surface to form a dense adsorption protective layer.
[0023] The functionalized L-proline-based bis-Schiff base corrosion inhibitor of the present invention is a highly efficient corrosion inhibitor, exhibits a good corrosion inhibition effect, and is a yellow powder at room temperature. When the present invention synthesizes the functionalized L-proline-based bis-Schiff base corrosion inhibitor, L-proline and terephthalaldehyde are used as raw materials, and the characteristics of the terephthalaldehyde molecule having two carbon-based functional groups and the L-proline molecule having a secondary amine are utilized to connect the nitrogen atom in L-proline with the carbon atom on the carbon group on the terephthalaldehyde through a nucleophilic addition reaction and then remove a molecule of water to synthesize the functionalized L-proline-based bis-Schiff base corrosion inhibitor. The preparation method of the present invention is simple to operate, the raw materials are easily available and cheap, the synthesis time is short, and the synthesis temperature is appropriate. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 This is a Fourier transform infrared absorption spectrum of the functionalized L-proline-based bis-Schiff base corrosion inhibitor sample prepared in Example 1 of the present invention;
[0025] Figure 2 Schematic diagram of a three-electrode test system;
[0026] Figure 3 AC impedance spectra of Q235 carbon steel with different concentrations of the functionalized L-proline-based bis-Schiff base inhibitor prepared in Example 2 added to 1 M hydrochloric acid solution;
[0027] Figure 4 It is the equivalent circuit diagram corresponding to the electrochemical impedance spectroscopy in Test Example 1 of the present invention;
[0028] Figure 5 It is a polarization curve diagram of Q235 carbon steel after being immersed in a 1M hydrochloric acid solution to which the functionalized L-proline-based bis-Schiff base corrosion inhibitor prepared in Example 2 with different concentrations is added for 1 hour;
[0029] Figure 6 Polarization curves of Q235 carbon steel immersed in 1M hydrochloric acid solution to which 0 mg / L and 50 mg / L of the functionalized L-proline-based bis-Schiff base corrosion inhibitor prepared in Example 2 were added at different temperatures for 1 hour. DETAILED DESCRIPTION
[0030] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.
[0031] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this description, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.
[0032] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0033] Example 1
[0034] A method for preparing a functionalized L-proline-based bis-Schiff base corrosion inhibitor comprises the following steps:
[0035] S1. Take 1g L-proline and 0.2g sodium hydroxide, dissolve in 25ml ethanol solution, heat the oil bath to 36℃, stir and dissolve to form solution A;
[0036] S2. 0.5 g of terephthalaldehyde in 50 ml of ethanol solution was added dropwise to solution A, and heating and stirring were continued for 6 h. After nucleophilic addition reaction, an L-proline-based bis-Schiff base was prepared;
[0037] S3. The L-proline-based bis-Schiff base obtained in step S2 is cooled to room temperature, rinsed with ethanol three times, and centrifuged and removed from the ethanol solution after each rinse to complete impurity removal, and air-dried under natural conditions for 2 days to obtain a functionalized L-proline-based bis-Schiff base corrosion inhibitor.
[0038] Example 2
[0039] A method for preparing a functionalized L-proline-based bis-Schiff base corrosion inhibitor comprises the following steps:
[0040] S1. Take 1.5g L-proline and 0.3g sodium hydroxide, dissolve in 40ml ethanol solution, heat the oil bath to 37°C, stir and dissolve to form solution A;
[0041] S2. 0.8 g of terephthalaldehyde in 70 ml of ethanol solution was added dropwise to solution A, and heating and stirring were continued for 8 h. After nucleophilic addition reaction, an L-proline-based bis-Schiff base was prepared;
[0042] S3. The L-proline-based bis-Schiff base obtained in step S2 is cooled to room temperature, rinsed with ethanol three times, and centrifuged and removed from the ethanol solution after each rinse to complete impurity removal, and air-dried under natural conditions for 2 days to obtain a functionalized L-proline-based bis-Schiff base corrosion inhibitor.
[0043] Example 3
[0044] A method for preparing a functionalized L-proline-based bis-Schiff base corrosion inhibitor comprises the following steps:
[0045] S1. Take 2.5g L-proline and 0.4g sodium hydroxide, dissolve in 50ml ethanol solution, heat the oil bath to 38°C, stir and dissolve to form solution A;
[0046] S2. 1.25 g of terephthalaldehyde in 100 ml of ethanol solution was added dropwise to solution A, and heating and stirring were continued for 7 h. After nucleophilic addition reaction, an L-proline-based bis-Schiff base was prepared;
[0047] S3. The L-proline-based bis-Schiff base obtained in step S2 is cooled to room temperature, rinsed with ethanol three times, and centrifuged and removed from the ethanol solution after each rinse to complete impurity removal, and air-dried under natural conditions for 3 days to obtain a functionalized L-proline-based bis-Schiff base corrosion inhibitor.
[0048] Fourier transform infrared spectroscopy characterization: The functionalized L-proline-based bis-Schiff base corrosion inhibitor prepared in Example 1 was subjected to infrared spectroscopy analysis, and the Fourier transform infrared absorption spectrum was obtained as shown in the following figure: Figure 1 As shown. Figure 1 It can be seen that the infrared absorption spectrum of the functionalized L-proline-based bis-Schiff base corrosion inhibitor prepared in Example 1 of the present invention includes different absorption bands, 3400-2600 cm -1 The stretching vibration peaks of OH and benzene ring -CH appeared in the range of 1697.22 cm -1 The characteristic peak of C=O of carboxyl group appeared at 1603.66cm-1, and the stretching vibration absorption peak of -C=N- appeared at 1603.66cm-1. The results showed that the functionalized L-proline-based double Schiff base corrosion inhibitor structure was successfully synthesized by dropwise addition method.
[0049] The functionalized L-proline-based bis-Schiff base corrosion inhibitor prepared in Example 2 of the present invention was evaluated by an electrochemical method.
[0050] Test Example 1: The electrochemical workstation is CS310H, and the test adopts a three-electrode system: the working electrode is made of Q235 carbon steel, the reference electrode is a saturated calomel electrode, and the auxiliary electrode is a platinum electrode. Figure 2As shown. Q235 carbon steel is encapsulated with epoxy resin into a cylindrical electrode. The electrode is encapsulated on one end of the epoxy resin and welded with copper wire to lead out the conduction circuit. The exposed area of the working electrode is 3.14cm 2 Except for the exposed surface in contact with the solution, the other end surfaces are encapsulated with epoxy resin. The exposed surface of the working electrode is polished with 240, 600, 1000 and 2000 mesh SiC sandpaper, then cleaned with deionized water and anhydrous ethanol, dried with cold air and placed in a vacuum dryer for use. The AC impedance test frequency is 10 -2 ~10 4 Hz, amplitude 5mV. The experiment was carried out in 1M hydrochloric acid solution, with five groups, where the concentrations of corrosion inhibitor were 0mg / L, 5mg / L, 10mg / L, 20mg / L, and 50mg / L, respectively, and the experimental temperature was 25°C. The test was started after the open circuit potential reached stability. The AC impedance spectra of Q235 carbon steel with different concentrations of functionalized L-proline-based bis-Schiff base corrosion inhibitor added in 1M hydrochloric acid solution were obtained as follows Figure 3 shown.
[0051] Use later Figure 4 The equivalent circuit diagram shown is used to fit the above impedance spectrum and calculate the corrosion inhibition efficiency, and the corrosion inhibition efficiency is calculated using formula (1):
[0052]
[0053] In the formula: IE EIS is the corrosion inhibition efficiency, %; is the charge transfer resistance of the blank group, Ω; R ct is the charge transfer resistance after adding corrosion inhibitor, Ω.
[0054] The fitting results of the AC impedance spectrum of Q235 with different concentrations of functionalized L-proline-based bis-Schiff base inhibitor added in 1 M hydrochloric acid solution are shown in Table 1.
[0055] Table 1
[0056]
[0057] In the table: C is the concentration of corrosion inhibitor, mg / L; R s is the solution resistance, Ω; CPE is the constant phase element; R ct is the charge transfer resistance, Ω; η is the corrosion inhibition efficiency, %.
[0058] From the fitting data shown in Table 1, it can be seen that the charge transfer resistance of the blank group without corrosion inhibitor is small, indicating that serious corrosion has occurred on the metal surface. When different concentrations of functionalized L-proline-based bis-Schiff base corrosion inhibitor are added, the charge transfer resistance increases significantly, indicating that the functionalized L-proline-based bis-Schiff base corrosion inhibitor can effectively inhibit the corrosion of metals. When the corrosion inhibitor concentration is 50 mg / L, the corrosion inhibition efficiency of the functionalized L-proline-based bis-Schiff base corrosion inhibitor is the best, up to 96.96%.
[0059] Test Example 2: The polarization curve of Q235 carbon steel in 1M hydrochloric acid solution with different concentrations of functionalized L-proline-based bis-Schiff base was measured according to the method described in Test Example 1. The scanning range was ±220mV relative to the open circuit potential, the scanning rate was 0.5mV / s, and the sampling frequency was 1Hz. The obtained polarization curve is shown in Figure 5 As shown, the corrosion inhibition efficiency is calculated using formula (2):
[0060]
[0061] Where: η is the corrosion inhibition efficiency, %; is the corrosion current of the blank control group after immersion for 1 hour, Amp / cm2; I O The corrosion current after immersion for 1 hour after adding the functionalized L-proline-based bis-Schiff base corrosion inhibitor, Amp / cm 2 .
[0062] The fitting results of the polarization curves of Q235 carbon steel after immersion in 1M hydrochloric acid solution with different concentrations of functionalized L-proline-based bis-Schiff base corrosion inhibitor for 1 h are shown in Table 2.
[0063] Table 2
[0064] C(mg / L) <![CDATA[I o (Amp / cm 2 )]]> <![CDATA[E o (Volts)]]> Corrosion inhibition efficiency η(%) 0 <![CDATA[6.1×10 -4 ]]> -0.43 - 5 <![CDATA[8.7×10 -5 ]]> -0.41 85.73 10 <![CDATA[4.9×10 -5 ]]> -0.42 91.96 20 <![CDATA[4.4×10 -5 ]]> -0.41 92.78 50 <![CDATA[4.2×10 -5 ]]> -0.42 93.11
[0065] In the table: C is the concentration of corrosion inhibitor, mg / L; E o is the corrosion potential, Volts; I o is the corrosion current, Amp / cm 2 ; η is the corrosion inhibition efficiency, %.
[0066] As shown in Table 2, after adding the functionalized L-proline-based bis-Schiff base corrosion inhibitor, the corrosion current of Q235 carbon steel decreased, indicating that the functionalized L-proline-based bis-Schiff base corrosion inhibitor has a significant inhibitory effect. When the concentration of the corrosion inhibitor is 10 mg / L, the corrosion inhibition efficiency can reach 91.96%.
[0067] Test Example 3: The polarization curves of Q235 carbon steel in 1M hydrochloric acid solution with different concentrations of functionalized L-proline-based bis-Schiff base added at different temperatures were measured according to the method described in Test Example 2. The scanning range was ±220 mV relative to the open circuit potential, the scanning rate was 0.5 mV / s, and the sampling frequency was 1 Hz. The obtained polarization curves are shown in Figure 6 As shown, the corrosion inhibition efficiency is calculated using formula (2):
[0068]
[0069] The fitting results of the polarization curves of Q235 carbon steel immersed in 1M hydrochloric acid solution with 0 mg / L and 50 mg / L functionalized L-proline-based bis-Schiff base corrosion inhibitor added at different temperatures for 1 h are shown in Table 3.
[0070] Table 3
[0071]
[0072]
[0073] In the table: C is the concentration of corrosion inhibitor, mg / L; T is the Kelvin temperature, K; E o is the corrosion potential, Volts; I o is the corrosion current, Amp / cm 2 ; η is the corrosion inhibition efficiency, %.
[0074] It can be seen from Table 3 that after adding the functionalized L-proline-based bis-Schiff base corrosion inhibitor, the corrosion current of Q235 carbon steel will increase with the increase of temperature, but the corrosion inhibition efficiency is still 86.11% at 40°C when the corrosion inhibitor concentration is 50 mg / L, indicating that the L-proline-based bis-Schiff base corrosion inhibitor has a significant inhibitory effect.
[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing a functionalized L-proline-based bis-Schiff base corrosion inhibitor, characterized in that: The following steps are involved: S1. Take L-proline and sodium hydroxide, dissolve them in ethanol solution, heat them in an oil bath and stir them to dissolve to form solution A; S2. Add terephthalaldehyde ethanol solution dropwise to solution A, continue heating and stirring for nucleophilic addition reaction, and prepare an L-proline-based bis-Schiff base; S3. After cooling the L-proline-based bis-Schiff base obtained in step S2 to room temperature, the L-proline-based bis-Schiff base is removed from the mixture and dried to obtain a functionalized L-proline-based bis-Schiff base corrosion inhibitor.
2. The method for preparing the functionalized L-proline-based bis-Schiff base corrosion inhibitor according to claim 1, characterized in that: The mass ratios of L-proline, sodium hydroxide and terephthalaldehyde in step S1 and step S2 are 1-2.5, 0.2-0.4 and 0.5-1.
25.
3. The method for preparing the functionalized L-proline-based bis-Schiff base corrosion inhibitor according to claim 2, characterized in that: The mass volume ratio of L-proline to ethanol in step S1 is (1-2.5) g: (25-50) ml.
4. The method for preparing the functionalized L-proline-based bis-Schiff base corrosion inhibitor according to claim 2, characterized in that: In the step S2, the mass volume ratio of terephthalaldehyde to ethanol in the ethanol solution of terephthalaldehyde is (0.5-1.25) g: (50-100) ml.
5. The method for preparing the functionalized L-proline-based bis-Schiff base corrosion inhibitor according to claim 1, characterized in that: The temperature of the oil bath in step S1 is 36-38°C.
6. The method for preparing the functionalized L-proline-based bis-Schiff base corrosion inhibitor according to claim 1, characterized in that: The heating and stirring time in step S2 is 6 to 8 hours.
7. The method for preparing the functionalized L-proline-based bis-Schiff base corrosion inhibitor according to claim 1, characterized in that: The specific steps of removing impurities in step S3 are: washing the L-proline-based bis-Schiff base with ethanol for multiple times, and performing centrifugal separation after each washing to complete the impurity removal.
8. The method for preparing the functionalized L-proline-based bis-Schiff base corrosion inhibitor according to claim 1, characterized in that: The specific steps of drying in step S3 are: air-drying under natural conditions for 2 to 3 days to complete the drying.
9. A functionalized L-proline-based bis-Schiff base corrosion inhibitor prepared by the preparation method according to any one of claims 1 to 8.
10. Use of the functionalized L-proline-based bis-Schiff base corrosion inhibitor according to claim 9 in the field of preventing corrosion of Q235 carbon steel materials.