Novel halogenated pyrazino-phenanthroline micromolecular organic corrosion inhibitor and preparation method thereof

Abstract

The invention provides a novel halogenated pyrazino-phenanthroline small-molecule organic corrosion inhibitor and a preparation method thereof. The corrosion inhibitor comprises any one of Dppz-Br, Dppz-Cl and Dppz-F, and the structural formula of the corrosion inhibitor is shown in the description. The method comprises the following steps: step 1, selecting required phenanthroline diketone and required halogenated o-phenylenediamine as initial raw materials; 2, adding the initial raw material into a reactor filled with a required solvent, and synthesizing halogenated pyrazino-phenanthroline micromolecules in one step; step 3, judging whether the synthesized halogenated pyrazino-phenanthroline micromolecules meet requirements or not, and if so, obtaining the required organic corrosion inhibitor; according to the halogenated pyrazino phenanthroline small-molecule novel organic corrosion inhibitor and the preparation method thereof, the synthesis process of the corrosion inhibitor can be simplified, the synthesis efficiency of the corrosion inhibitor can be improved, the pollution and cost consumption of the corrosion inhibitor can be effectively reduced, the corrosion inhibition effect of the corrosion inhibitor can be improved, and the service life of the corrosion inhibitor can be prolonged. The corrosion inhibitor has an excellent anti-corrosion effect on carbon steel in a 15% hydrochloric acid acidification system.

Description

Technical Field

[0001] The invention relates to the field of corrosion inhibitors in acidification processes, and in particular to a novel halogenated pyrazine-phenanthroline small molecule organic corrosion inhibitor and a preparation method thereof. Background Art

[0002] The direct economic losses caused by corrosion each year account for about 1%-4% of the world's national GDP. The damage to the physical and chemical properties of metal materials caused by corrosion will cause about 30% of metal equipment to be scrapped, resulting in a serious waste of resources. At present, society is paying more and more attention to the economic losses and casualties caused by metal corrosion. In addition to conventional coating protection, the use of organic metal corrosion inhibitors is an efficient and low-cost anti-corrosion technology developed in recent years. Pyrazinophenanthroline can strongly coordinate with various metal ions such as iron ions to form various metal ion chelates. This type of metal ion chelate itself has a large conjugated system, which helps it to be efficiently adsorbed on the metal surface; at the same time, this type of material has a rigid bidentate planar structure containing nitrogen. The lone pair of electrons on the N atom can coordinate with the empty orbit of the metal to form a coordination bond and a bidentate pincer structure, which is more conducive to its capture of metal ions, thereby reducing corrosion active sites and inhibiting the formation of corrosion products, and ultimately effectively delaying the degree of metal corrosion.

[0003] (1) Foreign technology

[0004] Foreign scientists have studied phenanthroline structure as an organic metal corrosion inhibitor for a long time. Phenanthroline is a common metal ion chelating agent. Studies have found that it has a strong 2+ It has a strong coordination and chelation effect and is widely used in the field of metal ion detection. In 1989, Banerjee found that the corrosion inhibition rate of phenanthroline on mild steel in sulfuric acid solution exceeded 90%. In addition, IBObot synthesized a new type of phenanthroline corrosion inhibitor 2-methylnitro-1H imidazole [4,5-f] [1,10]-phenanthroline (MEIP), and used the weight loss method and UV-visible spectrophotometry to explore the corrosion inhibition performance of carbon steel in 0.5M sulfuric acid solution. At a temperature of 303K and a concentration of 10μM, the corrosion inhibition rate of MEIP on carbon steel in sulfuric acid reached 87%, and MEIP was adsorbed on the surface of carbon steel in the form of physical adsorption. And confirmed the corrosion inhibition properties of MEIP-Fe complex on metal surfaces.

[0005] (2) Domestic technology

[0006] Overall, the research on phenanthroline corrosion inhibitors in China is later than that in foreign countries, and most of them are studies on compound corrosion inhibitors. For example, Mu Guannan et al. found that o-phenanthroline has a synergistic effect with Cl- in phosphoric acid and hydrochloric acid media. The corrosion inhibitor effectively hinders the contact between the corrosive medium and carbon steel through adsorption, which leads to a significant improvement in the corrosion inhibition performance of o-phenanthroline on carbon steel in acid. Wang Lin et al. used the weight loss method to study the synergistic corrosion inhibition performance of o-phenanthroline and Br. The experiment showed that the corrosion inhibition of o-phenanthroline and potassium bromide on cold-rolled steel was significantly improved to 97%. Xueming L used the weight loss method and electrochemical technology to find that the corrosion inhibition effect of o-phenanthroline on cold-rolled steel in 0.5M sulfuric acid was significantly improved in the presence of sodium chloride.

[0007] Although there are many studies on phenanthroline corrosion inhibitors in the prior art, the current mainstream corrosion inhibitors still have the problems of high pollution, high development cost and unsatisfactory corrosion inhibition effect in strong acid environment. Therefore, it is of great significance to study how to reduce the pollution and cost consumption of corrosion inhibitors and improve the corrosion inhibition effect of corrosion inhibitors.

[0008] Patent publication number CN118812533A mentions an azapyrazine-phenanthroline small molecule organic corrosion inhibitor and a preparation method thereof. The corrosion inhibitor is Dppz-3py or Dppz-4py or Dppz-md. The method for preparing the corrosion inhibitor comprises: S1, adding o-phenanthrolinedione, 3,6-dibromo-1,2-phenylenediamine and anhydrous ethanol to a flask, refluxing at 80°C for 4h in a nitrogen atmosphere, filtering after the reaction is completed, and washing with acetone, tetramethyleneimine, and the like; Hydrofuran, petroleum ether, and deionized water are used to wash the filter cake to obtain the intermediate Dppz-br; S2, Dppz-br, reactant A, potassium carbonate are added to a two-necked flask, a mixed solvent consisting of tetrahydrofuran and water is added, palladium acetate is added, and the mixture is refluxed at 80°C in a nitrogen atmosphere for 24 hours. After the reaction is completed, suction filtration is performed, and the filter cake is washed with petroleum ether, DMF, and deionized water in turn, and the washed filter cake is vacuum dried to obtain a crude product of aza-pyrazine and phenanthroline small molecule organic corrosion inhibitor. This patent can solve the problem that the corrosion inhibition effect of o-phenanthroline organic corrosion inhibitors in the prior art is general, but the preparation of the corrosion inhibitor requires the synthesis of the intermediate product Dppz-br first, and then the final product is synthesized with the help of the intermediate. The entire synthesis process is complicated and the yield is low. Summary of the invention

[0009] In view of this, the present invention aims to propose a halogenated pyrazine and phenanthroline small molecule novel organic corrosion inhibitor and its preparation method, in order to solve the problems that the mainstream corrosion inhibitors in the prior art still have large pollution, high development cost and unsatisfactory corrosion inhibition effect in a strong acid environment; thereby achieving a process that can simplify the synthesis of corrosion inhibitors, improve the efficiency of corrosion inhibitor synthesis, and effectively reduce the pollution and cost consumption of corrosion inhibitors, improve the corrosion inhibition effect of corrosion inhibitors, and make the corrosion inhibitor have excellent anti-corrosion effect on carbon steel in a 15% hydrochloric acid acidification system. In addition, the corrosion inhibitor prepared by the present application can not only enrich the types of pyrazine and phenanthroline small molecule organic corrosion inhibitors, but also improve the corrosion inhibition performance of corrosion inhibitors.

[0010] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0011] The present invention relates to a halogenated pyrazine and phenanthroline small molecule novel organic corrosion inhibitor and a preparation method thereof. The halogenated pyrazine and phenanthroline small molecule novel organic corrosion inhibitor comprises any one of Dppz-Br, Dppz-C1, and Dppz-F; wherein the molecular structure of Dppz-Br is: The molecular structure of Dppz-Cl is: The molecular structure of Dppz-F is:

[0012] A method for preparing a halogenated pyrazine and phenanthroline small molecule novel organic corrosion inhibitor, the method is used to prepare the halogenated pyrazine and phenanthroline small molecule novel organic corrosion inhibitor, the method comprises the following steps:

[0013] Step 1, selecting the desired phenanthrolinedione and the desired halogenated o-phenylenediamine as initial raw materials;

[0014] Step 2: adding the initial raw material into a reactor filled with a desired solvent, setting the reaction environment in the reactor, and controlling the reaction temperature in the reactor to be T. After the desired reaction time t, the initial raw material is synthesized into a halogenated pyrazine and phenanthroline small molecule in one step;

[0015] Step 3: By testing the corrosion inhibition performance of the halogenated pyrazine and phenanthroline small molecule, determine whether the synthesized halogenated pyrazine and phenanthroline small molecule meets the requirements. If yes, the research and development is successful, and the desired halogenated pyrazine and phenanthroline small molecule novel organic corrosion inhibitor with excellent performance is obtained. No, by adjusting the amount of the initial raw materials and solvents in step 2, as well as the reaction conditions of the reactor, and then adjusting the structure of the halogenated pyrazine and phenanthroline small molecule, a novel organic corrosion inhibitor with excellent performance is obtained.

[0016] Furthermore, in step 1, the volume ratio of the required phenanthrolinedione to the required halogenated o-phenylenediamine is in the range of 1:1-1:1.5.

[0017] Furthermore, the desired halogenated o-phenylenediamine is any one of 4,5-dibromo-o-phenylenediamine, 4,5-dichloro-o-phenylenediamine and 4,5-difluoro-o-phenylenediamine.

[0018] Further, the halogenated o-phenylenediamine is 4,5-dibromo-o-phenylenediamine, and the desired phenanthrolinedione is o-phenanthrolinedione; the reaction formula for synthesizing Dppz-Br from o-phenanthrolinedione and 4,5-dibromo-o-phenylenediamine is:

[0019]

[0020] Further, the halogenated o-phenylenediamine is 4,5-dichloro-o-phenylenediamine, and the required phenanthrolinedione is o-phenanthrolinedione; the reaction formula for synthesizing Dppz-Cl from o-phenanthrolinedione and 4,5-dichloro-o-phenylenediamine is:

[0021]

[0022] Further, the halogenated o-phenylenediamine is 4,5-difluoro-o-phenylenediamine, and the desired phenanthrolinedione is o-phenanthrolinedione; the reaction formula for synthesizing Dppz-F from o-phenanthrolinedione and 4,5-difluoro-o-phenylenediamine is:

[0023]

[0024] Furthermore, in step 2, the required solvent includes any one of methanol, ethanol, and dioxane.

[0025] Furthermore, the value of T is 65°C-120°C, and the value of t is 2h-12h.

[0026] Further, step three includes:

[0027] Step S31: characterize the basic physical and chemical properties of the halogenated pyrazine and phenanthroline small molecule to determine whether the halogenated pyrazine and phenanthroline small molecule meets the requirements. If yes, execute step S33; if not, execute step S32;

[0028] Step S32: according to the detection result, return to step 2 to adjust the amount of initial raw materials, solvent, and reaction conditions of the reactor, so as to obtain the desired new organic corrosion inhibitor;

[0029] Step S33: Conduct electrochemical test on the halogenated pyrazine and phenanthroline small molecule to determine whether the halogenated pyrazine and phenanthroline small molecule is stable. If yes, the desired new organic corrosion inhibitor is prepared. If no, return to step S32.

[0030] Compared with the prior art, the novel organic corrosion inhibitor of halogenated pyrazine and phenanthroline small molecule and the preparation method thereof described in the present invention have the following beneficial effects:

[0031] The corrosion inhibitor prepared by the present application can not only enrich the types of pyrazine and phenanthroline small molecule organic corrosion inhibitors, but also improve the corrosion inhibition performance of the corrosion inhibitor. In industrial applications, by adding a small amount of corrosion inhibitor, metal equipment in the acidification process can be effectively protected. In addition, through the setting of the preparation method in the present application, the process of corrosion inhibitor synthesis can be simplified, the efficiency of corrosion inhibitor synthesis can be improved, and the pollution and cost consumption of the corrosion inhibitor can be effectively reduced, and the corrosion inhibition effect of the corrosion inhibitor can be improved, so that the corrosion inhibitor has excellent anti-corrosion effect on carbon steel in a 15% hydrochloric acid acidification system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which constitute part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention. In the accompanying drawings:

[0033] Figure 1 For the corrosion inhibitor molecule Dppz-F 1 Schematic diagram of H NMR spectrum;

[0034] Figure 2 For the corrosion inhibitor molecule Dppz-Cl 1 Schematic diagram of H NMR spectrum;

[0035] Figure 3 For the corrosion inhibitor molecule Dppz-Br 1 Schematic diagram of H NMR spectrum;

[0036] Figure 4 Schematic diagram of Fourier infrared spectra of three halogenated pyrazine and phenanthroline corrosion inhibitors Dppz-Br, Dppz-Cl and Dppz-F;

[0037] Figure 5 Schematic diagram of UV-visible absorption spectra (in DMF solution) of three halogenated pyrazine and phenanthroline corrosion inhibitors Dppz-Br, Dppz-Cl and Dppz-F;

[0038] Figure 6a-6c Schematic diagram of DFT density functional calculation (B3LYP, 6-31G, d, p) of three halogenated pyrazine and phenanthroline corrosion inhibitor molecules Dppz-Br, Dppz-C1 and Dppz-F;

[0039] Figure 7 It is a schematic diagram of the open circuit voltage-time curve of low carbon steel in a blank 15% hydrochloric acid solution and a hydrochloric acid solution with 25 mg / L corrosion inhibitor molecules added;

[0040] Figure 8 It is a schematic diagram of the Nyquist plot of low carbon steel in a blank 15% hydrochloric acid solution and a hydrochloric acid solution with 25 mg / L corrosion inhibitor molecules added;

[0041] Fig. 9 Schematic diagram of polarization curves of low carbon steel in a blank 15% hydrochloric acid solution and a hydrochloric acid solution with 25 mg / L corrosion inhibitor molecules added. DETAILED DESCRIPTION

[0042] The inventive concepts of the present disclosure will be described below using terms commonly used by those skilled in the art to convey the essence of their work to other persons skilled in the art. However, these inventive concepts can be embodied in many different forms and should not be considered limited to the embodiments described herein.

[0043] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0044] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0045] In order to solve the problems that the mainstream corrosion inhibitors in the prior art still have high pollution, high development cost and unsatisfactory corrosion inhibition effect in strong acid environment; this embodiment proposes a new type of halogenated pyrazine and phenanthroline small molecule organic corrosion inhibitor and a preparation method thereof, wherein the new type of halogenated pyrazine and phenanthroline small molecule organic corrosion inhibitor includes any one of Dppz-Br, Dppz-C1, and Dppz-F.

[0046] Among them, the molecular structure formula of Dppz-Br is: The molecular structure of Dppz-Cl is: The molecular structure of Dppz-F is:

[0047] A method for preparing a halogenated pyrazine and phenanthroline small molecule novel organic corrosion inhibitor, the method is used to prepare a halogenated pyrazine and phenanthroline small molecule novel organic corrosion inhibitor, the method comprises the following steps:

[0048] Step 1, selecting the desired phenanthrolinedione and the desired halogenated o-phenylenediamine as initial raw materials;

[0049] Step 2: adding the initial raw material into a reactor filled with a desired solvent, setting the reaction environment in the reactor, and controlling the reaction temperature in the reactor to be T. After the desired reaction time t, the initial raw material is synthesized into a halogenated pyrazine and phenanthroline small molecule in one step;

[0050] Step 3: By testing the corrosion inhibition performance of the halogenated pyrazine and phenanthroline small molecule, it is judged whether the synthesized halogenated pyrazine and phenanthroline small molecule meets the requirements. If yes, it is successfully developed to obtain the required halogenated pyrazine and phenanthroline small molecule novel organic corrosion inhibitor with excellent performance. No, according to the corrosion inhibition performance test results of the existing halogenated pyrazine and phenanthroline small molecule in step 3, by adjusting the amount of the initial raw material and the solvent in step 2, and the reaction conditions of the reactor, the structure of the halogenated pyrazine and phenanthroline small molecule is adjusted to meet the requirements, and the required novel organic corrosion inhibitor with excellent performance is obtained.

[0051] Among them, in step 1, the volume ratio of the required phenanthroline dione and the required halogenated o-phenylenediamine ranges from 1:1 to 1:1.5. By selecting different halogenated o-phenylenediamines, a series of halogenated pyrazine and phenanthroline Dppz-Br, Dppz-Cl and Dppz-F can be prepared; in this embodiment, the required phenanthroline dione is o-phenanthroline dione; the required halogenated o-phenylenediamine is any one of 4,5-dibromo-o-phenylenediamine, 4,5-dichloro-o-phenylenediamine and 4,5-difluoro-o-phenylenediamine.

[0052] In addition, in step 2, the required solvent includes any one of methanol, ethanol, and dioxane. The value of T is 65° C.-120° C.; the value of t is 2h-12h.

[0053] By taking advantage of the advantages of organic phenanthroline molecules that can form stable chelates with ferrous ions, excellent corrosion inhibition performance for metallic iron, strong structural modifiability and low development cost, and introducing a series of halogen atoms at the side end of pyrazinophenanthroline, the synergistic effect between phenanthroline complex small molecule corrosion inhibitor and halogen is effectively improved. Further, by systematically exploring the effect of halogen substituents on the corrosion inhibition efficiency of o-phenanthroline, a new type of halogen-substituted phenanthroline slow-release agent small molecule material with excellent corrosion inhibition performance is obtained.

[0054] Preferably, when the halogenated o-phenylenediamine is 4,5-dibromo-o-phenylenediamine, phenanthrolinedione and 4,5-dibromo-o-phenylenediamine are synthesized to obtain Dppz-Br; when the halogenated o-phenylenediamine is 4,5-dichloro-o-phenylenediamine, phenanthrolinedione and 4,5-dichloro-o-phenylenediamine are synthesized to obtain Dppz-Cl; when the halogenated o-phenylenediamine is 4,5-difluoro-o-phenylenediamine, phenanthrolinedione and 4,5-difluoro-o-phenylenediamine are synthesized to obtain Dppz-F.

[0055] By using phenanthrolinedione and different halogenated o-phenylenediamines as starting materials, a series of halogenated pyrazinophenanthroline Dppz-Br, Dppz-Cl and Dppz-F can be synthesized in one step. By constructing a series of pyrazinophenanthroline derivatives with different halogen substitutions and systematically studying the influence of halogen substituents on the corrosion inhibition performance, halogenated pyrazinophenanthroline derivatives with excellent corrosion inhibition performance are obtained.

[0056] Step three includes:

[0057] Step S31: characterize the basic physical and chemical properties of the halogenated pyrazine and phenanthroline small molecule to determine whether the halogenated pyrazine and phenanthroline small molecule meets the requirements. If yes, execute step S33; if not, execute step S32;

[0058] Step S32: according to the detection results, return to step 2, adjust the amount of the initial raw material, the solvent, and the reaction conditions of the reactor, and then adjust the structure of the halogenated pyrazine and phenanthroline small molecule to meet the requirements, and obtain the desired new organic corrosion inhibitor with excellent performance;

[0059] Step S33: Conduct electrochemical test on the halogenated pyrazine and phenanthroline small molecule to determine whether the halogenated pyrazine and phenanthroline small molecule is stable. If yes, a new organic corrosion inhibitor with excellent performance is prepared. If no, return to step S32.

[0060] By reacting phenanthroline dione with different halogenated o-phenylenediamine reagents, and changing the feed ratio, different solvents, reaction temperature and reaction time during the reaction, we finally successfully developed a high-yield halogen-substituted pyrazine and phenanthroline after multiple experimental optimizations.

[0061] Step S31 includes:

[0062] Step S311: characterize the structure of the halogenated pyrazine and phenanthroline small molecule; determine whether the structure of the halogenated pyrazine and phenanthroline small molecule is accurate, if yes, execute step S312; if no, execute step S32;

[0063] Step S312: testing the ultraviolet-visible absorption spectrum of the halogenated pyrazine and phenanthroline small molecule; judging whether the peak shape and maximum absorption peak of the ultraviolet absorption spectrum of the halogenated pyrazine and phenanthroline small molecule meet the requirements, if yes, executing step S313; if not, executing step S32;

[0064] Step S313: Density functional theory (DFT) calculation of the halogenated pyrazine and phenanthroline small molecule; determine whether the halogenated pyrazine and phenanthroline small molecule is qualified, if yes, execute step S33; if not, execute step S32.

[0065] Step S33 includes:

[0066] Step S331: perform an open circuit voltage test (OCP) on the halogenated pyrazine and phenanthroline small molecule to determine whether the halogenated pyrazine and phenanthroline small molecule is in a stable state. If yes, execute step S332; if no, execute step S32;

[0067] Step S332: Conduct electrochemical impedance and polarization curve tests on the halogenated pyrazine and phenanthroline small molecule to determine whether the halogenated pyrazine and phenanthroline small molecule meets the corrosion inhibition requirements. If yes, prepare a new organic corrosion inhibitor with excellent performance; if not, return to step S32.

[0068] By conducting electrochemical tests on the prepared series of halogenated pyrazine and phenanthroline small molecules, it can be shown that this series of corrosion inhibitors still have excellent corrosion inhibition performance in 15% hydrochloric acid solution, and the results can also provide a reference for the subsequent development of high-performance o-phenanthroline corrosion inhibitors.

[0069] In summary, the present application has conducted a series of exploratory studies on synthesis conditions and successfully synthesized three halogenated pyrazine and phenanthroline small molecule corrosion inhibitors. By changing the feeding ratio of the synthesis, different solvents, reaction temperature and reaction time and other conditions, continuous attempts were made. Finally, after multiple experimental optimizations, a high-yield halogen-substituted pyrazine and phenanthroline under the optimal reaction conditions was successfully developed. Taking Dppz-Br, Dppz-Cl and Dppz-F as examples, the final optimized preparation method and conditions are shown in Examples 1-3:

[0070] Example 1: Preparation of Dppz-Br

[0071] O-phenanthroline dione (1.00 g, 4.75 mmol) and 4,5-dibromo-o-phenylenediamine (1.51 g, 5.7 mmol) were added to a 50 mL double-necked round-bottom flask containing 25 mL of anhydrous ethanol solution, and stirred for 4 h at a reaction temperature of 80° C. in a nitrogen atmosphere. After the reaction was completed, the mixture was allowed to stand and cool to room temperature, and the mixture was filtered and washed with acetone, tetrahydrofuran, petroleum ether, and deionized water, and dried under vacuum by column chromatography to obtain a white solid Dppz-Br (yield = 75%), as shown in Table 1 below.

[0072] Among them, the reaction formula for synthesizing Dppz-Br from phenanthrolinedione, i.e., o-phenanthrolinedione, and 4,5-dibromo-o-phenylenediamine is:

[0073]

[0074] Table 1

[0075]

[0076] Example 2: Preparation of Dppz-Cl

[0077] Phenanthrolinedione (1.00 g, 4.75 mmol) and 4,5-dichloro-o-phenylenediamine (1.01 g, 5.7 mmol) were added to a 50 mL double-necked round-bottom flask containing 25 mL of anhydrous ethanol solution, and stirred at 80° C. for 4 h in a nitrogen atmosphere. After the reaction was completed, the mixture was allowed to cool to room temperature, and the mixture was filtered and washed with acetone, tetrahydrofuran, petroleum ether, and deionized water, and dried under vacuum by column chromatography to obtain a yellow solid Dppz-Cl (yield = 86%), as shown in Table 2 below.

[0078] Among them, the reaction formula for synthesizing Dppz-C1 from phenanthrolinedione, i.e., o-phenanthrolinedione, and 4,5-dichloro-o-phenylenediamine is:

[0079]

[0080] Table 2

[0081]

[0082] Example 3: Preparation of Dppz-F

[0083] Phenanthroline dione (1.00 g, 4.75 mmol) and 4,5-difluoro-o-phenylenediamine (0.83 g, 5.7 mmol) were added to a 50 mL double-necked round-bottom flask containing 25 mL of anhydrous ethanol solution, and stirred at 80° C. for 4 h in a nitrogen atmosphere. After the reaction was completed, the mixture was allowed to cool to room temperature, and the mixture was filtered and washed with acetone, tetrahydrofuran, petroleum ether, and deionized water, and dried under vacuum by column chromatography to obtain a yellow solid Dppz-F (yield = 56%), as shown in Table 3 below.

[0084] Among them, the reaction formula for synthesizing Dppz-F from phenanthrolinedione, i.e., o-phenanthrolinedione, and 4,5-difluoro-o-phenylenediamine is:

[0085]

[0086] Table 3

[0087]

[0088] The basic physical and chemical properties of the halogenated pyrazinophenanthroline small molecules prepared in Examples 1-3 were characterized:

[0089] 1) Characterization of the structure of halogenated pyrazine and phenanthroline small molecules:

[0090] The prepared halogenated pyrazine and phenanthroline was separated and purified by silica gel column chromatography, concentrated to remove the solvent, and dried in a vacuum oven for 24 hours. The solid sample was subjected to nuclear magnetic resonance hydrogen spectrum ( 1 H-NMR) Figure 1-Figure 3 ) and Fourier transform infrared spectroscopy ( Figure 4) to verify the correctness of the product structure.

[0091] 2) Ultraviolet-visible absorption spectrum test of halogenated pyrazine and phenanthroline small molecules:

[0092] The obtained halogenated pyrazine and phenanthroline small molecules were prepared into a dilute solution of N, N-dimethylformamide (DMF) and subjected to UV-visible absorption spectrum test, with the test scanning range from 250nm to 600nm. Figure 5 As shown, it can be seen that the UV absorption spectra of Dppz-Br, Dppz-C1 and Dppz-F have similar peak shapes, and the maximum absorption peaks are located at 381nm, 392nm and 394nm, respectively.

[0093] 3) Density functional theory (DFT) calculation of halogenated pyrazine and phenanthroline small molecules:

[0094] The molecular conformations and HOMO / LUMO energy levels of Dppz-Br, Dppz-Cl and Dppz-F were simulated by density functional theory (DFT) using Gaussian (B3LYP / 6-31G, d, p basis set). Figure 6a-6c As shown in the figure, the electron cloud distribution characteristics of HOMO / LUMO of Dppz-Br, Dppz-Cl and Dppz-F molecules are basically the same. The electron cloud distribution on LUMO is mainly on the pyrazine ring, while the electron cloud on HOMO is mainly distributed on the pyridine ring adjacent to pyrazine. After calculation, the relevant parameters of the three are: the band gap size relationship is: Dppz-F>Dppz-Cl>Dppz-Br.

[0095] Electrochemical tests were performed on the halogenated pyrazine and phenanthroline small molecules prepared in Examples 1-3; the corrosion effects of the three 25 mg / L corrosion inhibitors were tested in a 15% hydrochloric acid solution, where the blank experimental group was a 15% hydrochloric acid solution:

[0096] 1) Open circuit voltage test (OCP):

[0097] To ensure the accuracy of electrochemical testing during the experiment, the electrochemical test must be carried out in a stable state of the three-electrode system. When the OCP curve tends to a horizontal straight line, it indicates that the test system has reached a steady state. Figure 7 As shown, after immersion in acid solution for 45 min, the OCP curves of Dppz-Br, Dppz-Cl, Dppz-F and blank hydrochloric acid systems tend to be horizontal straight lines, and the test system is in a stable state.

[0098] 2) Electrochemical impedance and polarization curve test:

[0099] Electrochemical impedance spectroscopy is one of the most commonly used methods to study the corrosion inhibition performance of corrosion inhibitors. The interface corrosion conditions of the working electrode can be obtained by analyzing the impedance curve and polarization curve.

[0100] like Figure 8 As shown in the figure, compared with the blank group, the impedance arc radius of the corrosion inhibitor added increased significantly, and the impedance curve radius of Dppz-Cl was the largest, followed by Dppz-Br and Dppz-F. The results show that the addition of corrosion inhibitors inhibits the corrosion of carbon steel in 15% hydrochloric acid solution. At the same time, the corrosion inhibition rate of the halogenated pyrazine and phenanthroline small molecule derivatives is in the order of Dppz-Cl>Dppz-Br>Dppz-F. In addition, the corrosion inhibition rates of Dppz-Br, Dppz-Cl and Dppz-F corrosion inhibitors on carbon steel in a hydrochloric acid solution with a mass fraction of 15% are 60.7%, 68.8% and 46.2% respectively, obtained by circuit fitting of the impedance diagram. In summary, the three corrosion inhibitors have excellent corrosion inhibition properties in strong acid, and the order of corrosion inhibition rate is: Dppz-Cl>Dppz-Br>Dppz-F.

[0101] like Fig. 9 As shown in the figure, the polarization curve of Dppz-Cl is the most significantly reduced, followed by Dppz-Br and Dppz-F. The corrosion inhibition order of the three corrosion inhibitors is consistent with the order measured by electrical impedance, and the corrosion inhibition rate order is Dppz-Cl>Dppz-Br>Dppz-F. The halogenated phenanthroline corrosion inhibitor molecule developed in the present invention can effectively reduce the current density of the carbon steel corrosion process in the hydrochloric acid solution, thereby playing a significant corrosion inhibition and protection role for carbon steel.

[0102] Electrochemical impedance tests were performed on the developed Dppz-Br, Dppz-Cl and Dppz-F corrosion inhibitor molecules. In a three-electrode system, the impedance of the carbon steel electrode when the three 25 mg / L corrosion inhibitors were added to a 15% hydrochloric acid solution by mass was significantly better than that of the blank hydrochloric acid solution. The specific implementation methods and results are shown in Table 4 below:

[0103] Table 4 Product test results of Examples 1-3

[0104]

[0105] Through one-step organic synthesis, brominated, chlorinated and fluorinated pyrazinophenanthroline small molecule organic corrosion inhibitors (Dppz-Br, Dppz-Cl and Dppz-F) were successfully developed. Through testing and comparison, it was found that chlorinated pyrazinophenanthroline had the best corrosion inhibition performance in a hydrochloric acid solution with a mass fraction of 15%. Taking advantage of the strong designability of organic corrosion inhibitor molecules, three different halogenated structures were introduced into the phenanthroline structure, all of which showed excellent corrosion inhibition performance, which not only effectively broadened the application scenarios and scope of use of phenanthroline organic corrosion inhibitors, but also provided a new construction strategy for the synthesis and design modification of subsequent phenanthroline high-efficiency corrosion inhibitor molecules.

[0106] Different from patent CN1118812533A, this application simplifies the synthesis process and synthesizes the corrosion inhibitor in one step, which not only improves the yield, but also reduces the cost. Secondly, the intermediate product in the above patent is not used as a corrosion inhibitor in the field of corrosion inhibitors. Therefore, this application does not have repeatability or substitutability with the above patent, and has the advantages of simplicity and efficiency on the basis of satisfying the corrosion inhibition performance. In addition, this application successfully synthesized three halogenated pyrazine and phenanthroline organic corrosion inhibitor small molecule materials through a simple one-step organic chemical reaction and screening and optimizing the experimental conditions. In the structure of this series of molecular materials, the nitrogen atom lone pair electrons on phenanthroline and the large conjugated aromatic ring π electrons coordinate with the empty orbit of the iron atom to form a coordination bond, thereby effectively adsorbing on the metal surface, thereby effectively inhibiting the corrosion of carbon steel in a hydrochloric acid solution with a mass fraction of 15%. This application successfully developed a series of halogenated pyrazine and phenanthroline corrosion inhibitors with simple synthesis, high yield and significant anti-corrosion effect, which will have broad application prospects and practical value in the fields of oil extraction, metal pickling, machinery manufacturing, etc.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A novel small molecule organic corrosion inhibitor of halogenated pyrazine and phenanthroline, characterized in that: Including any one of Dppz-Br, Dppz-Cl, and Dppz-F; wherein the molecular structure of Dppz-Br is: The molecular structure of Dppz-Cl is: The molecular structure of Dppz-F is:

2. A method for preparing a novel small molecule organic corrosion inhibitor of halogenated pyrazine and phenanthroline, characterized in that: The method is used to prepare a novel organic corrosion inhibitor of halogenated pyrazine and phenanthroline small molecules according to claim 1, and the method comprises the following steps: Step 1, selecting the desired phenanthrolinedione and the desired halogenated o-phenylenediamine as initial raw materials; Step 2: adding the initial raw material into a reactor filled with a desired solvent, setting the reaction environment in the reactor, and controlling the reaction temperature in the reactor to be T. After the desired reaction time t, the initial raw material is synthesized into a halogenated pyrazine and phenanthroline small molecule in one step; Step three, by detecting the corrosion inhibition performance of the halogenated pyrazine and phenanthroline small molecule, determine whether the synthesized halogenated pyrazine and phenanthroline small molecule meets the requirements. If yes, the research and development is successful to obtain the required halogenated pyrazine and phenanthroline small molecule new organic corrosion inhibitor with excellent performance; if no, by adjusting the amount of the initial raw materials and solvent in step two, as well as the reaction conditions of the reactor, and then adjusting the structure of the halogenated pyrazine and phenanthroline small molecule, the required new organic corrosion inhibitor with excellent performance is obtained.

3. The method for preparing a novel organic corrosion inhibitor of halogenated pyrazine and phenanthroline small molecules according to claim 2, characterized in that: In the step 1, the volume ratio of the required phenanthrolinedione to the required halogenated o-phenylenediamine is in the range of 1:1-1:1.

5.

4. The method for preparing a novel organic corrosion inhibitor of halogenated pyrazine and phenanthroline small molecules according to claim 3, characterized in that: The desired halogenated o-phenylenediamine is any one of 4,5-dibromo-o-phenylenediamine, 4,5-dichloro-o-phenylenediamine and 4,5-difluoro-o-phenylenediamine.

5. The method for preparing a novel organic corrosion inhibitor of halogenated pyrazine and phenanthroline small molecules according to claim 4, characterized in that: The halogenated o-phenylenediamine is 4,5-dibromo-o-phenylenediamine, and the required phenanthrolinedione is o-phenanthrolinedione; the reaction formula for synthesizing Dppz-Br from o-phenanthrolinedione and 4,5-dibromo-o-phenylenediamine is:

6. The method for preparing a novel organic corrosion inhibitor of halogenated pyrazinophenanthroline small molecule according to claim 4, characterized in that: The halogenated o-phenylenediamine is 4,5-dichloro-o-phenylenediamine, and the required phenanthrolinedione is o-phenanthrolinedione; the reaction formula for synthesizing Dppz-Cl from o-phenanthrolinedione and 4,5-dichloro-o-phenylenediamine is:

7. The method for preparing a novel organic corrosion inhibitor of halogenated pyrazinophenanthroline small molecule according to claim 4, characterized in that: The halogenated o-phenylenediamine is 4,5-difluoro-o-phenylenediamine, and the required phenanthrolinedione is o-phenanthrolinedione; the reaction formula for synthesizing Dppz-F from o-phenanthrolinedione and 4,5-difluoro-o-phenylenediamine is:

8. The method for preparing a novel organic corrosion inhibitor of halogenated pyrazine and phenanthroline small molecules according to claim 2, characterized in that: In the step 2, the required solvent includes any one of methanol, ethanol and dioxane.

9. The method for preparing a novel organic corrosion inhibitor of halogenated pyrazinophenanthroline small molecule according to claim 8, characterized in that: The value of T is 65°C-120°C, and the value of t is 2h-12h.

10. The method for preparing a novel small molecule organic corrosion inhibitor of halogenated pyrazinophenanthroline according to claim 2, characterized in that: The step three comprises: Step S31: characterize the basic physical and chemical properties of the halogenated pyrazine and phenanthroline small molecule to determine whether the halogenated pyrazine and phenanthroline small molecule meets the requirements. If yes, execute step S33; if not, execute step S32; Step S32: according to the detection result, return to step 2 to adjust the amount of initial raw materials, solvent, and reaction conditions of the reactor, so as to obtain the desired new organic corrosion inhibitor; Step S33: Conduct an electrochemical test on the halogenated pyrazine and phenanthroline small molecule; determine whether the halogenated pyrazine and phenanthroline small molecule is stable. If yes, prepare the desired new organic corrosion inhibitor; if not, return to step S32.

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