Anti-corrosion inhibitor and preparation method thereof

Abstract

The invention relates to the technical field of inhibitors, in particular to an anti-corrosion inhibitor and a preparation method thereof.The inhibitor comprises an active compound, ethyl 6-methyl-2-oxo-3, 4-dihydropyrimidine-5-carboxylate serves as a dihydropyrimidone skeleton of the active compound, the fourth site of the skeleton is connected with 4-((1-(4-R-benzyl)-1H-1, 2, 4-triazolo [3, 4-b] pyrimidone), and the second site of the skeleton is connected with a compound of 4-((1-(4-R-benzyl)-1H-1, 2, 4-b)-1, 2, 4-b] pyrimidone. In the structural formula I, R is one of hydrogen, fluorine, chlorine, bromine or iodine, and in the structural formula II, R is one of hydrogen, fluorine, chlorine, bromine or iodine. The invention can solve the problems of strong acidic corrosion and high consumption of traditional corrosion inhibitors in pickling / chemical cleaning of steel in the prior art.

Description

Technical Field

[0001] This invention relates to the field of inhibitor technology, and in particular to an anti-corrosion inhibitor and its preparation method. Background Technology

[0002] Pickling for rust removal and chemical cleaning for maintenance commonly use acidic media such as hydrochloric acid. However, acids significantly accelerate corrosion of steel equipment and pipelines, threatening heat exchange efficiency and equipment lifespan. Therefore, in engineering, organic inhibitors are often added to reduce the corrosion rate to an acceptable level. Organic compounds containing nitrogen, oxygen, and sulfur coordinating atoms exhibit good corrosion inhibition capabilities. However, under different acidity, temperature, and ionic strength conditions, there is still significant room for improvement in existing inhibitors regarding the balance between low-dose high efficiency and formulation availability and scalability. Summary of the Invention

[0003] In view of the above technical problems, the present invention provides a corrosion inhibitor and its preparation method to solve the problems of strong acid corrosion and high dosage of traditional corrosion inhibitors in pickling / chemical cleaning.

[0004] Other features and advantages of this disclosure will become apparent from the following detailed description, or may be learned in part from practice of this disclosure.

[0005] According to one aspect of the present invention, a corrosion inhibitor is provided, the inhibitor comprising an active compound having an ethyl 6-methyl-2-oxo-3,4-dihydropyrimidin-5-carboxylic acid ester as a dihydropyrimidinone skeleton, wherein a 4-((1-(4-R-benzyl)-1H-1,2,3-triazol-4-yl)methoxy)phenyl group is attached at the 4 position of the skeleton, wherein R is one of hydrogen, fluorine, chlorine, bromine or iodine; Alternatively, the inhibitor may include one of the enantiomers, racemates, and tautomers of the active compound, as well as its crystal form and solvate.

[0006] Furthermore, the inhibitor is a solution formulation, and the solvent is selected from ethanol, water, or a mixture of ethanol and water.

[0007] Furthermore, the inhibitor is used to inhibit corrosion of pipes in an acidic medium, wherein the acidic medium is an aqueous solution of hydrochloric acid.

[0008] According to a second aspect of this disclosure, a method for preparing a corrosion inhibitor is provided, the method comprising the following steps: S1) 4-hydroxybenzaldehyde and propyne bromide were refluxed in acetone in the presence of potassium carbonate to give 4-(prop-2-alkynoxy)benzaldehyde. S2) In an ethanol-water mixed solvent, in the presence of a catalytic system of copper(II) acetate monohydrate, sodium ascorbate, and 1,10-o-phenanthroline monohydrate, the 4-(propane-2-alkynoxy)benzaldehyde undergoes a 1,3-dipolar cycloaddition with sodium azide and a 4-R-benzyl halide to give an aldehyde-triazole intermediate, wherein R is one of hydrogen, fluorine, chlorine, bromine, or iodine; S3) Under the catalysis of cerium trifluoromethanesulfonate or its hydrate, the aldehyde-triazole intermediate is reacted with ethyl acetoacetate and urea in ethanol in a three-component biginelli reaction in the same reaction vessel to obtain the above-mentioned active compound.

[0009] Furthermore, in step S1, the molar ratio of 4-hydroxybenzaldehyde:propyne bromide:potassium carbonate is 1:(1.5-1.7):(1.2-1.4), and the reflux time is 2-3 hours.

[0010] Furthermore, the dosage of the catalytic system in step S2 is: 5 mol% copper(II) acetate monohydrate, 5 mol% 1,10-o-phenanthroline monohydrate, and sodium ascorbate for in-situ reduction of copper(II) to copper(I).

[0011] Furthermore, in step S3, the amount of cerium trifluoromethanesulfonate used is 15-25 mol% of the substrate molar amount, and the reaction is completed by stirring at 20-30°C for 2-4 days.

[0012] Furthermore, the crude product of the active compound obtained in step S3 is purified by silica gel column chromatography, wherein the eluent for the silica gel column chromatography is a mixed solvent of dichloromethane and ethanol.

[0013] Furthermore, the eluent is a mixed solvent of dichloromethane and C1–C3 alcohol in a volume ratio of (99.5:0.5)–(90:10).

[0014] The technical solution disclosed herein has the following beneficial effects: The inhibitor disclosed herein can significantly improve charge transfer resistance and reduce double-layer capacitance with small amounts of dosage, and has high inhibition efficiency with EIS fitting; it can also achieve near-level high-efficiency inhibition for different substituents, and has stable surface adsorption / protective layer formation ability under acid washing conditions; the target heterocycle can be obtained through a multi-component strategy, and the target product can be obtained through a one-pot reaction with high yield. Attached Figure Description

[0015] Figure 1 This is a flowchart of a corrosion inhibitor as described in the embodiments of this specification; Figure 2 This diagram illustrates the synthesis reaction process of 4-(propan-2-acetyloxy)benzaldehyde in the examples of this specification. Figure 3 This diagram illustrates the synthetic reaction process of the aldehyde-triazole intermediate in the examples of this specification. Figure 4 This diagram illustrates the synthesis reaction process of the compounds used in the examples of this specification. Detailed Implementation

[0016] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make this disclosure more comprehensive and complete, and to fully convey the concept of example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a full understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure may be practiced with one or more of these specific details omitted. In other instances, well-known technical solutions are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0017] Furthermore, the accompanying drawings are merely illustrative of this disclosure. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted.

[0018] Example 1

[0019] Reference Figure 1 The diagram shown is a flowchart illustrating a method for preparing an anti-corrosion inhibitor according to an embodiment of the present invention. This method may specifically include the following steps S1-S3: In step S1, as Figure 2 As shown, 4-hydroxybenzaldehyde and propyne bromide were refluxed in acetone in the presence of potassium carbonate to give 4-(prop-2-acetyloxy)benzaldehyde.

[0020] In this process, 4-hydroxybenzaldehyde is mixed with acetone and stirred. Propylene bromide and anhydrous potassium carbonate (K2CO3) are added at a molar ratio of 1:(1.5-1.7):(1.2-1.4). The mixture is reacted under reflux for 2-3 hours. After routine washing with water, extraction and drying, 4-(prop-2-acetyloxy)benzaldehyde is obtained.

[0021] In step S2, as Figure 3 As shown, in an ethanol-water mixed solvent, in the presence of a catalytic system of copper(II) acetate monohydrate, sodium ascorbate, and 1,10-o-phenanthroline monohydrate, sodium azide and 4-benzyl halide (X = Cl / Br) were added, microwaved at about 90 degrees Celsius for 15 minutes, and stirred continuously to obtain an aldehyde-triazole intermediate.

[0022] In step S3, as Figure 4 As shown, the aldehyde-triazole intermediate is reacted with ethyl acetoacetate and urea in ethanol in a three-component biginelli reaction in the same reaction vessel under the catalysis of cerium trifluoromethanesulfonate or its hydrate to obtain the compound.

[0023] Specifically, the intermediate is dissolved in ethanol with ethyl acetoacetate and urea, and 15-25 mol% of cerium trifluoromethanesulfonate or its hydrate is added. The mixture is stirred at 20-30 °C for 2-4 days to complete the three-component bicene reaction in the same reaction vessel. After solvent removal by rotary evaporation, the compound was purified by silica gel column chromatography using a dichloromethane / ethanol system (preferably 98:2 by volume, or dichloromethane and C1–C3 alcohol (99.5:0.5)–(90:10)). The target component was collected and concentrated to obtain a compound with an ethyl 6-methyl-2-oxo-3,4-dihydropyrimidine-5-carboxylic acid ester as its backbone and 4-((1-(4-benzyl)-1H-1,2,3-triazol-4-yl)methoxy)phenyl linked at the 4-position. This compound can form a racemic mixture or a single enantiomer. Different crystal forms or solvates can be obtained by crystallization with different solvents, and the above morphologies do not change its backbone and spectroscopic characteristics. That is, the compound can exist in tautomer forms (such as ketone-ene tautomerism), but this tautomerism does not change its backbone structure and properties, and is considered part of this embodiment.

[0024] Example 2

[0025] In another specific embodiment, the same process windows (S1, S2, S3) and catalytic system as in Example 1 are used, but the 4-benzyl halide in step S2 is replaced with 4-fluorobenzyl chloride, while other feed ratios, solvent composition, and reaction time remain unchanged, yielding the target compound R=F. Purification is also performed using silica gel column chromatography with a dichloromethane / ethanol system (98:2, v / v). The ethanol ratio can be finely adjusted within the range of (99.5:0.5)–(90:10) based on column efficiency. The obtained compound can be recrystallized from the solvent to obtain an ethanol solvate or a solvent-free crystalline form.

[0026] Example 3

[0027] In another specific embodiment, the process and conditions are the same as in Example 1, except that the 4-benzyl halide in step S2 is replaced with 4-chlorobenzyl chloride to obtain the target compound R=Cl. The preparation process and purification conditions are the same as for R=H / F. Good separation is achieved using dichloromethane / ethanol (98:2, v / v) as the column chromatography eluent. Under these conditions, the product exhibits a typical ethyl ester triplet and a tetrahydropyrimidine-CH singlet in its 1H NMR spectrum, and triazole quaternary carbon and carbonyl carbon signals in its 1C NMR spectrum. The product structure is well-defined and reproducible.

[0028] Example 4

[0029] In a further embodiment, using the same process window as in the aforementioned examples, the 4-benzyl halide in step S2 is replaced with 4-bromobenzyl bromide to obtain the target compound with R=Br; other conditions remain unchanged. The crude product is purified by elution with a dichloromethane / C1–C3 alcohol system (using ethanol as an example, volume fraction 1–10%) to obtain the target compound with a purity ≥95%. The eluent can be removed by rotary evaporation and the residual ethanol can be removed by drying under reduced pressure at 40–50 °C. If necessary, recrystallization with ethyl acetate / n-hexane can be used to obtain a solid sample for long-term retention or further crystal form screening.

[0030] Example 5

[0031] In another embodiment, using the aforementioned process and conditions, the 4-benzyl halide in step S2 is replaced with 4-iodobenzyl bromide to obtain the target compound R=I. This compound exhibits comparable column chromatography expansion compared to R=H / F / Cl / Br, and the suitable eluent range remains dichloromethane and C1–C3 alcohols (99.5:0.5)–(90:10). This embodiment can also obtain different crystal forms by changing the crystallization solvent or temperature program.

[0032] In one embodiment of a solution formulation, any of the target compounds (e.g., R=H or R=Cl) is dissolved in ethanol or an ethanol-water mixture to prepare a stock solution (e.g., 1.0 g·L⁻¹). -1 When using, add it to the hydrochloric acid aqueous solution according to the volume ratio (e.g., 1 mol·L⁻¹). -1 In HCl, the final concentration of the inhibitor is 1–100 ppm, preferably 5–20 ppm; if the solid is added directly, it should first be dissolved in a small amount of ethanol before adding it to the acidic medium and stirring until homogeneous. The prepared solution formulation shows no obvious precipitation or discoloration after being placed in a sealed container at room temperature and protected from light for at least 30 days; compounds with different R substituents show good solubility and compatibility in this formulation system.

[0033] In an alternative process embodiment, to demonstrate the process options and boundaries, 4-(propane-2-alkynoxy)benzaldehyde is first prepared according to step S1, and then a biginelli reaction is carried out to obtain a dihydropyrimidinone intermediate with a propyne side chain (ethanol is used as the solvent, and p-toluenesulfonic acid monohydrate can be used as the acid catalyst, and the temperature is maintained at 60 °C for 40–60 h). Then, in ethanol-water, using a copper(II) acetate / 1,10-phenanthroline / sodium ascorbate system as the catalytic system, sodium azide and 4-R-benzyl halide are added to carry out a one-pot three-component click reaction to obtain the target compound with the same skeleton and substituents as in the aforementioned embodiment.

[0034] In this embodiment, the method is carried out in the order of substitution of bicene and click, namely: firstly, 4-(propane-2-alkynoxy)benzaldehyde, ethyl acetoacetate and urea are reacted in ethanol at 60 °C for 40-60 hours under the catalysis of p-toluenesulfonic acid monohydrate to obtain a dihydropyrimidinone intermediate with a propyne side chain; subsequently, a three-component click reaction is carried out with sodium azide and 4-R-benzyl halide in the catalytic system described in step S2 to obtain a corrosion inhibitor.

[0035] In the product implementation, the product of step S3 is a corrosion inhibitor. The inhibitor includes an active compound with an ethyl 6-methyl-2-oxo-3,4-dihydropyrimidin-5-carboxylic acid ester as its dihydropyrimidinone skeleton. A 4-((1-(4-R-benzyl)-1H-1,2,3-triazol-4-yl)methoxy)phenyl group is attached to the 4-position of the skeleton, where R is one of hydrogen, fluorine, chlorine, bromine, or iodine. Regarding the structure, isomers, crystal forms, and solvates of the active compound, the target molecules 8–12 obtained through step S3 are all heterocyclic combinations of 1,4-disubstituted-1,2,3-triazol-dihydropyrimidinone. The product is a stable organic molecule obtained under conventional conditions. It may form corresponding solvates or different crystal forms depending on the crystallization solvent, and may be an enantiomer, racemate, or tautomer. These morphologies do not change its skeletal structure or electrochemical inhibitory activity.

[0036] The corrosion inhibitor can be formulated as a solution. Preferably, any one of compounds 8–12 is dissolved in ethanol or ethanol-water (e.g., 1:1–2:1, v / v) to form a stock solution, which is then added to the target acidic medium as needed to achieve a final concentration of 10 ppm; alternatively, a small amount of solid can be dissolved in ethanol first and then injected into the pickling solution and mixed thoroughly.

[0037] In the specific implementation and verification of corrosion protection, a three-electrode system can be used for electrochemical impedance spectroscopy (EIS) testing. API 5L X52 steel is used as the working electrode (exposed area approximately 1 cm², chemical composition mass fraction: C 0.080, Mn 1.06, Si 0.26, Ti 0.003, V 0.054, Nb 0.041, P 0.019, S 0.003, Al 0.039, Ni 0.019, Ceq 0.274, balance Fe, pretreated according to metallographic standards before testing). Saturated Ag / AgCl is used as the reference electrode, and a graphite rod is used as the counter electrode. Impedance tests are performed in 1 mol·L⁻¹ HCl for blank and compound 8–12 (final concentration 10 ppm). The charge transfer resistance Rct and double-layer capacitance Cdl are obtained by fitting an R(Q)R equivalent circuit. The results are as follows: In the blank system, Rct ≈ 30 Ω·cm^2 and Cdl ≈ 310 µF·cm^-2. After adding the inhibitor, Rct significantly increased to approximately 565–733 Ω·cm^2 (corresponding to representative values ​​for compounds 9–10: 564.9 and 733.0 Ω·cm^2), and Cdl decreased to approximately 35–83 µF·cm^-2, with an inhibition efficiency (IE) of approximately 95% (compounds 8–12 were 95.1%, 94.7%, 95.9%, 94.8%, and 95.6%, respectively). This directly demonstrates the effective inhibition of steel corrosion by the active compounds in hydrochloric acid media.

[0038] Specifically, Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the claims.

[0039] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. An anticorrosion inhibitor characterized by comprising: The inhibitor comprises an active compound with an ethyl 6-methyl-2-oxo-3,4-dihydropyrimidine-5-carboxylate as a dihydropyrimidinone skeleton, a 4-((1-(4-R-benzyl)-1H-1,2,3-triazol-4-yl)methoxy)phenyl group connected to the 4-position of the skeleton, wherein R is one of hydrogen, fluorine, chlorine, bromine or iodine; Or, the inhibitor comprises one of enantiomers, racemates, tautomers of the active compound, and crystal forms and solvates thereof.

2. The corrosion-prevention inhibitor according to claim 1, characterized by, The inhibitor is a solution preparation, and the solvent is selected from ethanol, water or an ethanol-water mixed solvent.

3. The corrosion-prevention inhibitor according to claim 1, characterized by, The inhibitor is used for corrosion inhibition of pipe materials in an acidic medium, which is an aqueous hydrochloric acid solution.

4. A method for producing an anticorrosive inhibitor, characterized by, The method comprises the following steps: S1) refluxing 4-hydroxybenzaldehyde with propargyl bromide in the presence of potassium carbonate in acetone to obtain 4-(prop-2-ynyloxy)benzaldehyde; S2) in an ethanol-water mixed solvent, in the presence of a catalytic system of copper(II) acetate monohydrate, sodium ascorbate and 1,10-phenanthroline monohydrate, subjecting the 4-(prop-2-ynyloxy)benzaldehyde to 1,3-dipolar cycloaddition with sodium azide and a 4-R-benzyl halide to obtain an aldehyde-triazole intermediate, wherein R is one of hydrogen, fluorine, chlorine, bromine or iodine; S3) under the catalysis of cerium trifluoromethanesulfonate or its hydrate, subjecting the aldehyde-triazole intermediate to a three-component Bigninelli reaction with ethyl acetoacetate and urea in ethanol in the same reaction vessel to obtain the active compound of claim 1.

5. The method of claim 4, wherein the corrosion inhibitor is prepared by the steps of: In step S1, the molar ratio of 4-hydroxybenzaldehyde:propargyl bromide:potassium carbonate is 1:(1.5-1.7):(1.2-1.4), and the refluxing time is 2-3 hours.

6. The method of claim 4, wherein the corrosion inhibitor is prepared by the steps of: In step S2, the dosing amount of the catalytic system is 5 mol% of copper(II) acetate monohydrate and 5 mol% of 1,10-phenanthroline monohydrate, and sodium ascorbate is used to reduce copper(II) to copper(I) in situ.

7. The method of claim 4, wherein the corrosion inhibitor is prepared by the steps of: In step S3, the amount of cerium trifluoromethanesulfonate is 15-25 mol% of the molar amount of the substrate, and the reaction is completed under stirring at 20-30°C for 2-4 days.

8. The method of claim 4, wherein the corrosion inhibitor is prepared by the steps of: The crude product of the active compound obtained in step S3 is purified by silica gel column chromatography, and the eluent of the silica gel column chromatography is a mixed solvent of dichloromethane and ethanol.

9. The method of claim 8, wherein the corrosion inhibitor is prepared by the steps of: The eluent is a mixed solvent of dichloromethane and C1-C3 alcohol with a volume ratio of (99.5:0.5)-(90:10).

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