Fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle as well as preparation method and application of fluorescent metal corrosion inhibitor

Abstract

The invention belongs to the fields of chemistry, material science and corrosion engineering, and discloses a fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle as well as a preparation method and application of the fluorescent metal corrosion inhibitor. Five-membered ring furan is introduced into fluorophore coumarin through a simple and efficient Schiff base reaction, the fluorophore coumarin is well coordinated with iron ions through Schiff base carbon-nitrogen double bonds, furan heterocyclic rings and oxygen heteroatoms of the fluorophore coumarin, metal corrosion inhibition can be achieved, the use amount of the corrosion inhibitor can be detected through fluorescence, and the application range is wide. And environmental pollution caused by excessive use is avoided. Under the conditions that the temperature is 30 DEG C, the corrosion inhibition time is 8 hours and the corrosion inhibition concentration is 7 * 10 <-5 > mol / L, the fluorescent metal corrosion inhibitor shows the best corrosion inhibition effect on carbon steel, and the corrosion inhibition efficiency can reach 73.25%.

Description

Technical Field

[0001] The invention belongs to the fields of chemistry, material science and corrosion engineering, and relates to a fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle, and a preparation method and application thereof. Background Art

[0002] Metal corrosion is a common problem, especially in industrial production. The corrosion of metal equipment not only affects its service life, but may also cause safety accidents. In order to cope with this problem, corrosion inhibitors are widely used in the field of metal corrosion protection. There are many types of corrosion inhibitors in the prior art, but most of them have some problems. Traditional corrosion inhibitors, such as certain pyrimidine derivatives, indazole derivatives and quinoline derivatives, although they have certain corrosion inhibition effects, are often difficult to degrade and cause pollution to the environment, especially the increasingly serious water pollution problem. During the use of these corrosion inhibitors, the presence of a large number of heteroatoms (O, N, S) and aromatic ring structures can effectively inhibit the corrosion process, but their poor biodegradability brings a long-term burden to the environment. In addition, when using existing corrosion inhibitors, there is often a lack of effective online monitoring methods. Traditional detection methods are not only time-consuming and labor-intensive, but also difficult to reflect the adsorption and concentration changes of corrosion inhibitors on the metal surface in real time. This makes it impossible to accurately control the amount of corrosion inhibitor added in practical applications, which may lead to waste of resources and may fail to achieve the expected anti-corrosion effect due to insufficient corrosion inhibitors. The common metal corrosion inhibitors on the market, such as some organic corrosion inhibitors and inorganic corrosion inhibitors, can slow down metal corrosion to a certain extent, but their corrosion inhibition efficiency is generally not high. According to existing literature reports, under the best conditions of use, the corrosion inhibition efficiency of these corrosion inhibitors can often only reach about 50%-60%, which is difficult to meet the needs of some high-demand industrial applications. Summary of the invention

[0003] In order to overcome the shortcomings of the prior art, the present invention provides a fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle, and its preparation method and application. The five-membered ring furan is introduced into the fluorophore coumarin through a simple and efficient Schiff base reaction, and the Schiff base carbon-nitrogen double bond and furan heterocycle, as well as the oxygen heteroatom of the fluorophore coumarin itself, are used to make it well coordinated with the iron ion, which can not only achieve metal corrosion inhibition, but also make it possible to detect the amount of corrosion inhibitor by fluorescence, avoiding the pollution of the environment caused by excessive use. The fluorescent metal corrosion inhibitor is at a temperature of 30°C, a corrosion inhibition time of 8 hours, and a corrosion inhibition concentration of 7×10 -5 Under the condition of mol / L, it exhibits the best corrosion inhibition effect on carbon steel, and the corrosion inhibition efficiency can reach 73.25%.

[0004] The above object of the present invention is achieved through the following technical solutions:

[0005] A fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle, the fluorescent metal corrosion inhibitor is named CR-O, and its specific structural formula is as follows:

[0006]

[0007] The preparation method of the fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle is as follows: 4-diethylamino salicylaldehyde, diethyl malonate and piperidine are mixed in anhydrous ethanol, and the mixed solution is stirred and refluxed to obtain a crude product coumarin ester CR1; the coumarin ester CR1 is dissolved in an ethanol solution, hydrazine hydrate is slowly added dropwise, the reaction solution is stirred at room temperature, and the precipitated solid is filtered under reduced pressure to obtain a crude product CR2; CR2 and aldehyde are mixed with ethanol as a solvent to obtain a mixed solution, the solution is heated to reflux, the reaction solution is cooled at room temperature, and the solvent is removed by vacuum filtration to obtain a yellow powder fluorescent metal corrosion inhibitor CR-O; the specific reaction route is as follows:

[0008]

[0009] The preparation method of the fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle is specifically carried out as follows:

[0010] S1. 10 mmol 4-diethylamino salicylaldehyde, diethyl malonate and 4-6 ml piperidine are mixed in 120-150 ml anhydrous ethanol to obtain a mixed solution, and the mixed solution is stirred and refluxed to obtain compound CR1;

[0011] S2. 0.70 mmol of compound CR1 is further dissolved in 60-80 ml of ethanol solution, 3-5 ml of hydrazine hydrate is slowly added dropwise, and the reaction solution is stirred to obtain compound CR2;

[0012] S3.1.82mmol compound CR2 and aldehyde use ethanol as solvent; the prepared mixed solution is heated to reflux at 80-85°C for 2 hours, the reaction solution is cooled to 25°C and filtered to obtain the fluorescent metal corrosion inhibitor CR-O.

[0013] Furthermore, in step S1, the molar ratio of 4-diethylaminosalicylaldehyde to diethyl malonate is 1:2-3.

[0014] Furthermore, in step S1, the mixed solution is stirred and refluxed for 6 hours.

[0015] Furthermore, in step S2, the reaction solution was stirred at 25° C. for 30 min.

[0016] Furthermore, in step S3, the aldehyde is furfural.

[0017] Further, in step S3, the molar ratio of compound CR2 and is 1:1-1.5.

[0018] The present invention also claims the use of the fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle prepared by the above preparation method in slow-release metal materials, specifically in slow-release of carbon steel. The application conditions are: the fluorescent metal corrosion inhibitor is at a temperature of 30°C, the corrosion inhibition time is 8 hours, and the concentration of the fluorescent metal corrosion inhibitor is 7×10 -5 Under the condition of mol / L, it can inhibit the corrosion of low carbon steel.

[0019] The beneficial effects of the present invention compared with the prior art are:

[0020] The preparation method provided by the present invention not only retains the fluorescence properties of coumarin, but also introduces the active sites of furan heterocycles, thereby enhancing the interaction between the corrosion inhibitor and the metal surface. Compound CR-O has excellent fluorescence properties, which makes it possible to monitor the distribution and concentration of the corrosion inhibitor on the metal surface in real time through fluorescence detection. Compared with traditional corrosion inhibitors, this fluorescence monitoring method is more intuitive and accurate, which helps to optimize the amount of corrosion inhibitor used and avoid waste and potential problems caused by excessive use. At the same time, due to its efficient corrosion inhibition performance, it can reduce corrosion to metals, thereby extending the service life of metal equipment and reducing resource waste and environmental pollution caused by corrosion. Compound CR-O is not only suitable for the corrosion protection of common metal materials such as carbon steel, but may also be expanded to the corrosion protection field of other metal materials. The results of weight loss experiments show that at a temperature of 30°C, a corrosion inhibition time of 8 hours, and a corrosion inhibition concentration of 7×10 -5 Under the condition of mol / L, it exhibits the best corrosion inhibition effect on carbon steel, and the corrosion inhibition efficiency can reach 73.25%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the H NMR spectrum of compound CR-O in Example 1 of the present invention in DMSO;

[0022] Figure 2 is the carbon NMR spectrum of compound CR-O in Example 1 of the present invention in DMSO;

[0023] Figure 3 This is a diagram of a weight loss method experimental device in Example 4 of the present invention;

[0024] Figure 4 It is a time-corrosion inhibition efficiency diagram in comparative examples 1 to 7 of the present invention;

[0025] Figure 5 It is the temperature-corrosion inhibition efficiency diagram in comparative examples 4, 8 to 11 of the present invention;

[0026] Figure 6 It is the concentration-corrosion inhibition efficiency diagram in comparative examples 8, 12 to 15 of the present invention;

[0027] Figure 3Middle: 1. Test piece fixing and hanging device, 2. Constant temperature water bath, 3. Beaker, 4. Low carbon steel sheet. DETAILED DESCRIPTION

[0028] The present invention is described in detail below by specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0029] The preparation method provided by the present invention not only retains the fluorescence characteristics of coumarin, but also introduces the active site of furan heterocycle, thereby enhancing the interaction between the corrosion inhibitor and the metal surface. Its efficient corrosion inhibition performance can reduce the corrosion of metals, thereby extending the service life of metal equipment and reducing resource waste and environmental pollution caused by corrosion.

[0030] Example 1

[0031] A method for preparing fluorescent metal corrosion inhibitors based on coumarin and furan heterocycles;

[0032] Step 1: Synthesis of Compound CR1

[0033]

[0034] Synthesis of compound CR1: 4-diethylamino salicylaldehyde (10 g, 10 mmol), diethyl malonate (16 g, 20 mmol) and piperidine (5 mL) were mixed in anhydrous ethanol (150 ml), and the mixture was stirred and refluxed for 6 hours. During the process, thin layer chromatography (TLC) was used to determine whether the reactants were synthesized. The reaction solution was cooled to 25°C at room temperature and then poured into 100 mL of ice water. The precipitate was filtered, washed with water, dried, and recrystallized in toluene to obtain 7.9 g of yellow crystalline solid with a yield of 52.83%.

[0035] Step 2: Synthesis of Compound CR2

[0036]

[0037] Synthesis of compound CR2: Coumarin ester CR1 (4 g, 0.70 mmol) was dissolved in 60 ml of ethanol solution, and 4 ml of hydrazine hydrate was slowly added. The reaction solution was stirred at 25 ° C for 30 min. The precipitated solid was filtered under reduced pressure to obtain a yellow solid powder (0.62 mmol, 3.6 g) with a yield of 94.59%. The crude product did not need to be purified and was directly used in the next reaction.

[0038] Step 3: Synthesis of compound CR-O

[0039]

[0040] Synthesis of compound CR-O: The ethanol solution of compound CR2 (500 mg, 1.82 mmol) and aldehyde (2.73 mmol) was heated at 80°C for 2 hours. After TLC confirmed the completion of the reaction, the reaction solution was cooled at room temperature, and the precipitated solid was filtered under reduced pressure to obtain 0.3148 g of yellow powder, which was a fluorescent metal corrosion inhibitor with a yield of 47.70%.

[0041] 1 H-NMR (500MHz, DMSO-d6): δ (ppm) 11.66 (s, 1H, O = C-NH-), 8.75 (s, 1H, = CH-), 8.36 (s, 1H, -N = CH-), 7.87 (s, 1H ,-ArH),(d,1H,J=9Hz,-ArH),6.90(s,1H,-ArH),6.78(d,1H,J=11.73Hz,=CH-O-),6.65(m,2H,=CH-CH=CH-O- ),3.50(q,4H,J=7Hz,`-N-CH2-),1.15(t,6H,J=6.9Hz,-CH2CH3).13C-NMR(125MHz,DMSOd6):δ(ppm)161.9,1 59.5,157.9,153.2,149.8,149.0,145.8,138.5,132.3,114.5,112.7,110.8,108.9,108.3,96.4,44.9,12.8.

[0042] Application Example 1

[0043] The fluorescent metal corrosion inhibitor CR-O prepared in Example 1 was prepared with 1 mol / L hydrochloric acid solution at a concentration of 7×10 -5 mol / L fluorescent metal corrosion inhibitor; soak the low-carbon steel sheet in a hydrochloric acid system with fluorescent metal corrosion inhibitor, the hydrochloric acid system is 1mol / L. The low-carbon steel sheet is slow-released under the conditions of temperature 30°C and corrosion inhibition time of 8 hours.

[0044] Application Comparative Example 1

[0045] At a temperature of 25°C, the inhibition time is 2 hours, and the concentration of fluorescent metal inhibitor is 9×10 -5 mol / L, the slow release is carried out on the low carbon steel sheet. Other conditions are the same as those in Application Example 1.

[0046] Application Comparative Example 2

[0047] At a temperature of 25°C, the corrosion inhibition time is 4 hours, and the concentration of fluorescent metal corrosion inhibitor is 9×10 -5 mol / L, the slow release is carried out on the low carbon steel sheet. Other conditions are the same as those in Application Example 1.

[0048] Application Comparative Example 3

[0049] At a temperature of 25°C, the inhibition time is 6 hours and the concentration of fluorescent metal inhibitor is 9×10 -5 mol / L, the slow release is carried out on the low carbon steel sheet. Other conditions are the same as those in Application Example 1.

[0050] Application Comparative Example 4

[0051] At a temperature of 25°C, the inhibition time is 8 hours and the concentration of fluorescent metal inhibitor is 9×10 -5 mol / L, the slow release is carried out on the low carbon steel sheet. Other conditions are the same as those in Application Example 1.

[0052] Application Comparative Example 5

[0053] At a temperature of 25°C, the inhibition time is 10 hours, and the concentration of fluorescent metal inhibitor is 9×10 -5 mol / L, the slow release is carried out on the low carbon steel sheet. Other conditions are the same as those in Application Example 1.

[0054] Application Comparative Example 6

[0055] At a temperature of 25°C, the corrosion inhibition time is 24 hours, and the concentration of fluorescent metal corrosion inhibitor is 9×10 -5 mol / L, the slow release is carried out on the low carbon steel sheet. Other conditions are the same as those in Application Example 1.

[0056] Application Comparative Example 7

[0057] No fluorescent metal corrosion inhibitor is added, and the rest is the same as in Application Example 1.

[0058] Application Comparative Example 8

[0059] At a temperature of 30°C, the inhibition time is 8 hours, and the concentration of fluorescent metal inhibitor is 9×10 -5 mol / L, the slow release is carried out on the low carbon steel sheet. Other conditions are the same as those in Application Example 1.

[0060] Application Comparative Example 9

[0061] At a temperature of 35°C, the inhibition time is 8 hours, and the concentration of fluorescent metal inhibitor is 9×10 -5 mol / L, the slow release is carried out on the low carbon steel sheet. Other conditions are the same as those in Application Example 1.

[0062] Application Comparative Example 10

[0063] At a temperature of 40°C, the inhibition time is 8 hours, and the concentration of fluorescent metal inhibitor is 9×10 -5 mol / L, the slow release is carried out on the low carbon steel sheet. Other conditions are the same as those in Application Example 1.

[0064] Application Comparative Example 11

[0065] At a temperature of 45°C, the inhibition time is 8 hours, and the concentration of fluorescent metal inhibitor is 9×10 -5 mol / L, the slow release is carried out on the low carbon steel sheet. Other conditions are the same as those in Application Example 1.

[0066] Application Comparative Example 12

[0067] At a temperature of 30°C, the inhibition time is 8 hours, and the concentration of fluorescent metal inhibitor is 7×10 -5 mol / L, the slow release was carried out on the low carbon steel sheet. Other conditions are the same as those in Application Example 1.

[0068] Application Comparative Example 13

[0069] At a temperature of 30°C, the inhibition time was 8 hours, and the concentration of fluorescent metal inhibitor was 5×10 -5 mol / L, the slow release is carried out on the low carbon steel sheet. Other conditions are the same as those in Application Example 1.

[0070] Application Comparative Example 14

[0071] At a temperature of 30°C, the inhibition time was 8 hours, and the concentration of fluorescent metal inhibitor was 3×10 -5 mol / L, the slow release is carried out on the low carbon steel sheet. Other conditions are the same as those in Application Example 1.

[0072] Application Comparative Example 15

[0073] At a temperature of 30°C, the inhibition time was 8 hours, and the concentration of fluorescent metal inhibitor was 1×10 -5 mol / L, the slow release is carried out on the low carbon steel sheet. Other conditions are the same as those in Application Example 1.

[0074] Applied experimental research: Weightlessness testing

[0075] The present invention uses a weight loss experiment to detect the corrosion inhibition effect of CR-O (application examples and application comparison examples). The corrosion environment in the experiment is a 1 mol / L hydrochloric acid solution. In order to eliminate the influence of other factors, 20# low carbon steel (carbon content 0.17-0.24%) is selected for the experiment. The weight change of the low carbon steel sheet after the experiment is measured in three groups and the average value is taken. The experiment is carried out in a constant temperature environment, and a beaker is used to hold a blank or corrosion inhibitor experiment under different application examples and application comparison conditions, and then placed in a constant temperature water bath to ensure its temperature.

[0076] Treatment method for rusty low carbon steel sheets:

[0077] (1) First, clean the low-carbon steel specimen with cotton wool in deionized water, and then rinse the specimen with deionized water;

[0078] (2) Use absorbent cotton to clean the low carbon steel test piece twice in anhydrous ethanol, using about 50 ml per 10 pieces;

[0079] (3) Use a hair dryer to dry the undried anhydrous ethanol on the test piece;

[0080] (4) In this experiment, 400, 600, and 1000 grade water-sandpaper was used to polish the surface of the low-carbon steel specimen;

[0081] (5) Rinse the polished low-carbon steel sheet with anhydrous ethanol and deionized water, and then blow dry with a hair dryer;

[0082] (6) Spread the treated low-carbon steel sheet flat on the filter paper and wrap it up. After drying in a dryer, it can be weighed and used.

[0083] In the attached Figure 3 After the weight loss experiment is completed, the low-carbon steel sheet is taken out, dried with a hair dryer, and then weighed. The weighed low-carbon steel sheet is still processed according to the processing steps before other experiments. After the experiment, the corrosion inhibition efficiency should be calculated.

[0084] The corrosion inhibition efficiency IE can be calculated by the following formula:

[0085]

[0086] W- is the average weight loss when adding corrosion inhibitor. W0- is the average weight loss when not adding corrosion inhibitor

[0087] By the attached Figure 4 It shows that the highest corrosion inhibition efficiency is 70.25% at 8h, and the anti-corrosion performance for low-carbon steel sheets is the best. The slow-release efficiency shows an upward trend from 2h to 8h, and the slow-release efficiency begins to decline after 8h, and 8h is the time with the highest slow-release efficiency. The reason for this phenomenon may be that the corrosion inhibitor is constantly adsorbed by the low-carbon steel sheet before 8h, but at 8h, the surface of the low-carbon steel sheet has been saturated with adsorption. Even if the time continues to increase, the corrosion inhibitor on the surface of the low-carbon steel sheet will no longer continue to increase, and maintain a certain stability. And as time continues to increase, the low-carbon steel sheet is constantly corroded, the adsorption film on the surface will be destroyed, and the corrosion inhibition efficiency will also decrease.

[0088] By the attached Figure 5 As shown in the figure, the highest corrosion inhibition efficiency at 30°C is 72.29%, which has the best anti-corrosion performance for low-carbon steel sheets. As the temperature rises, the corrosion inhibition efficiency shows a downward trend. The reason for this phenomenon is that as the temperature rises, the intermolecular forces decrease, the thermal motion of the corrosive particles in the acidic system and the molecules on the surface of the metal material will intensify, and the adsorption of the corrosion inhibitor on the surface of the low-carbon steel sheet will be greatly weakened. Therefore, as the temperature rises, the corrosion inhibition efficiency will continue to decline.

[0089] Attached Figure 6 It is shown that when the corrosion inhibitor concentration is 7x10 -5mol / L, the highest corrosion inhibition efficiency is 73.25%, and the corrosion protection performance for #20 low carbon steel sheet is the best. And as the concentration of corrosion inhibitor decreases, the corrosion inhibition efficiency also begins to decrease. The reason for this phenomenon is that as the concentration of corrosion inhibitor decreases, the corrosion inhibitor factor added to the hydrochloric acid system also decreases. Under the same conditions, the corrosion protection factor that can be adsorbed by #20 low carbon steel sheet will also decrease, and the corrosion inhibition efficiency will decrease.

[0090] By analyzing the spectrum of CR-O and conducting a weight loss experiment, the basic anti-corrosion performance of CR-O can be obtained. This can solve the problem of controlling the amount of corrosion inhibitor used. The experimental results show that the metal corrosion inhibitor based on coumarin and furan heterocycle has a good corrosion resistance at a temperature of 30°C, a usage time of 8h and a concentration of 7x10 -5 mol / L has the best corrosion inhibition efficiency for 20# low carbon steel with carbon content (0.17-0.24%), which can prevent corrosion more effectively.

[0091] The above-described embodiments are only preferred embodiments of the present invention, but not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle, characterized in that the fluorescent The metal corrosion inhibitor is named CR-O, and its specific structural formula is as follows:

2. Use of the fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle as claimed in claim 1 in slow-release metal materials.

3. A method for preparing a fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle as claimed in claim 1, characterized in that: 4-Diethylamino salicylaldehyde, diethyl malonate and piperidine are mixed in anhydrous ethanol, and the mixed solution is stirred and refluxed to obtain a crude product of coumarin ester CR1; coumarin ester CR1 is dissolved in an ethanol solution, hydrazine hydrate is slowly added dropwise, the reaction solution is stirred at room temperature, and the precipitated solid is filtered under reduced pressure to obtain a crude product CR2; CR2 and aldehyde are mixed with ethanol as a solvent to obtain a mixed solution, the solution is heated to reflux, the reaction solution is cooled at room temperature, and the solvent is removed by vacuum filtration to obtain a yellow powder fluorescent metal corrosion inhibitor CR-O; the specific reaction route is as follows:

4. The preparation method according to claim 3, characterized in that: The specific steps are as follows: S1. 10 mmol 4-diethylamino salicylaldehyde, diethyl malonate and 4-6 ml piperidine are mixed in 120-150 ml anhydrous ethanol to obtain a mixed solution, and the mixed solution is stirred and refluxed to obtain compound CR1; S2. 0.70 mmol of compound CR1 is further dissolved in 60-80 ml of ethanol solution, 3-5 ml of hydrazine hydrate is slowly added dropwise, and the reaction solution is stirred to obtain compound CR2; S3.1.82mmol compound CR2 and aldehyde use ethanol as solvent; the prepared mixed solution is heated to reflux at 80-85°C for 2 hours, the reaction solution is cooled to 25°C and filtered to obtain the fluorescent metal corrosion inhibitor CR-O.

5. The preparation method according to claim 4, characterized in that: In step S1, the molar ratio of 4-diethylaminosalicylaldehyde to diethyl malonate is 1:2-3.

6. The preparation method according to claim 4, characterized in that: In step S1, the mixed solution is stirred and refluxed for 6 hours.

7. The preparation method according to claim 4, characterized in that: In step S2, the reaction solution was stirred at 25°C for 30 min.

8. The preparation method according to claim 4, characterized in that: In step S2 and step S3, the aldehyde is furfural.

9. The preparation method according to claim 4, characterized in that: In step S3, the molar ratio of compound CR2 and is 1:1-1.

5.

10. Use of the fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle prepared by the preparation method according to any one of claims 3 to 9 in slow-release metal materials.

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