A preparation method of neutralizing corrosion inhibitor

Abstract

The present invention provides a preparation method of a neutralization corrosion inhibitor, belongs to the technical field of metal corrosion inhibition, and comprises the following steps: imidazoline quaternary ammonium salt is uniformly mixed with thiourea, high temperature reaction, cooling, recrystallization, and thiourea imidazoline quaternary ammonium salt is obtained, i.e., corrosion inhibition component; 4-pyridyl amidoxime, silane and distilled water are mixed and heated and stirred, isocyanate cross-linking agent, octadecylamine polyoxyethylene ether, ammonia, and stirring is continued to obtain a neutralization component; corrosion inhibition component, neutralization component, lignin sulfonate, distilled water are stirred uniformly to obtain a neutralization corrosion inhibitor. The technical solution provided by the present invention avoids the problem that the existing neutralization corrosion inhibitor is prone to produce crystalline salts in an acidic environment, promotes corrosion under scale, and also improves the overall neutralization corrosion inhibition capacity.

Description

Technical Field

[0001] The invention relates to the technical field of metal corrosion inhibition, and in particular to a method for preparing a neutralizing corrosion inhibitor. Background Art

[0002] Metal corrosion refers to the damage caused by chemical or electrochemical reactions between metals and the surrounding medium. The occurrence of metal corrosion not only affects the service life and function of metal materials, but also poses a serious threat to the safety and operating efficiency of equipment. In recent years, due to the worsening of crude oil quality and the addition of various chemical agents during the oil production process, the acid value, sulfur content, chlorine content and salt content in crude oil have continued to rise, further causing the equipment to be exposed to corrosive media for a long time, accelerating the corrosion of refinery equipment, and greatly shortening the service life of oil and gas field equipment and gathering pipelines, making the corrosion protection of equipment face more difficulties.

[0003] In the petroleum and chemical industries, the metal corrosion problem in the top cooling system of the atmospheric and vacuum unit of the refinery is particularly prominent. The corrosion of this system mainly comes from the corrosive components in the crude oil, such as inorganic salts and sulfur-containing and chlorine-containing compounds. These components will generate corrosive gases such as HCl and H2S at high temperatures, and form an acidic corrosive environment of HCl-H2S-H2O with a low pH value after condensation, posing a serious corrosion threat to the equipment, thereby affecting the normal operation and service life of the equipment. In order to effectively deal with these problems, it is particularly important to take appropriate anti-corrosion measures. In recent years, the corrosion protection technology of the top cooling system of the atmospheric and vacuum unit of the refinery has mainly focused on the use of corrosion inhibitors, the selection of corrosion-resistant materials and the use of inner wall coatings. In particular, corrosion inhibitors have become an effective means of metal corrosion protection due to their low cost, simple operation, quick effect and suitability for long-term use. Existing neutralizing corrosion inhibitors, such as water-soluble imidazoline corrosion inhibitors, have certain corrosion inhibition effects on equipment corrosion in the top cooling system of the atmospheric and vacuum unit of an oil refinery, but their corrosion inhibition effect is still relatively single, which makes their corrosion inhibition performance in an acidic environment relatively poor. The single imidazoline component cannot meet the corrosion protection requirements well, and it is easy to react with acid to generate crystalline salts that are deposited on the metal surface, causing a local oxygen-deficient environment, thereby causing under-deposit corrosion and aggravating equipment damage.

[0004] Therefore, it is necessary to provide a method for preparing a neutralizing corrosion inhibitor to solve the problems existing in the above-mentioned prior art. Summary of the invention

[0005] In view of this, the present invention provides a method for preparing a neutralizing corrosion inhibitor, which not only improves the corrosion inhibition component and the neutralizing component therein, avoiding the problem that the existing neutralizing corrosion inhibitor is prone to produce crystalline salts in an acidic environment and promotes under-scale corrosion, but also improves the overall neutralization and corrosion inhibition ability.

[0006] To achieve the above object, the present invention provides a method for preparing a neutralizing corrosion inhibitor, comprising the following steps:

[0007] S1, mixing the imidazoline quaternary ammonium salt and thiourea uniformly, reacting at high temperature, cooling, and recrystallizing to obtain a thiourea-based imidazoline quaternary ammonium salt, i.e., a corrosion inhibition component;

[0008] S2, mixing 4-pyridyl amidoxime, silane and distilled water, heating and stirring, adding isocyanate crosslinking agent, octadecylamine polyoxyethylene ether and ammonia water, and continuing to stir to obtain a neutralization component;

[0009] S3. Evenly stir the corrosion inhibition component, the neutralization component, the lignin sulfonate and the distilled water to obtain a neutralization corrosion inhibitor.

[0010] The present invention prepares thiourea-based imidazoline quaternary ammonium salt as a corrosion inhibition component. The imidazoline quaternary ammonium salt with a thiourea group has a better sustained-release effect than a common imidazoline quaternary ammonium salt. First, the nitrogen-containing five-membered ring structure of the imidazoline ring and the nitrogen atom in the quaternary ammonium salt have strong electrophilicity, can attract electrons on the metal surface, form a coordination bond with the metal surface, and combine with the metal matrix to form a firm protective film. In addition, the sulfur element in the thiourea group combines with the empty orbit of the metal surface through a lone pair of electrons to generate a sulfide protective layer, which is adsorbed on the metal surface in the protective film in the form of physical adsorption and chemical adsorption to form a firmer and denser adsorption film, so as to slow down the corrosion of the metal surface and further improve the overall sustained-release effect.

[0011] In the preparation process of the neutralization component, the present invention first uses silane to treat 4-pyridyl amidoxime to improve its hydrophilicity and introduce multiple polar groups (such as amino groups), and then uses isocyanate to cross-link the silane-treated 4-pyridyl amidoxime and octadecylamine polyoxyethylene ether to obtain a neutralization component having both pH neutralization performance and good corrosion inhibition performance. Among them, the pyridine ring in the 4-pyridyl amidoxime has alkalinity and can work with ammonia water to neutralize the acidic substances in the solution to generate soluble 4-pyridyl amidine salts, which can not only avoid the occurrence of under-scale corrosion caused by the formation of crystalline salts, but also increase the pH value of the solution. In an acidic environment, 4-pyridyl amidoxime reacts with hydrogen ions or acidic substances in an acidic medium through the nitrogen atom of its oxime group to inhibit the progress of the corrosion reaction. This neutralization can change the pH value near the metal surface, reduce the attack of acidic substances on the metal, and thus effectively prevent corrosion. Moreover, the 4-pyridyl amidoxime treated with silane is further compounded with octadecylamine polyoxyethylene ether under the action of an isocyanate crosslinking agent to introduce a polar group (such as an amide group or an amino group), which helps to improve the water solubility of octadecylamine polyoxyethylene ether, further improve the dispersibility and overall stability of the neutralization component in the aqueous medium, and octadecylamine polyoxyethylene ether reacts with metal ions through the alkalinity of its amine group to reduce metal corrosion and further improve the neutralization slow-release performance. In addition, the present invention utilizes the property of octadecylamine polyoxyethylene ether to form a dense monolayer adsorption film on the metal surface, adsorbs the neutralization component on the metal surface, further enhances the density and stability of the film, and improves the metal corrosion inhibition effect.

[0012] Optionally, the imidazoline quaternary ammonium salt in step S1 is prepared by mixing oleic acid, diethylenetriamine and xylene with high-speed stirring, heating at 130-150° C. for 2 h, heating to 190-210° C. for further 2 h for cyclization reaction, cooling to 90-100° C., slowly adding benzyl chloride, heating the resulting mixture under reflux for 3-5 h, and finally evaporating the solvent to obtain the imidazoline quaternary ammonium salt.

[0013] The invention uses the amine group of diethylenetriamine as a nitrogen source, reacts with oleic acid under high temperature conditions to promote the generation of an imidazoline ring, and the benzyl chloride reacts with the nitrogen atom in the imidazoline ring through a nucleophilic substitution reaction to generate a benzyl-substituted imidazoline structure. The benzyl chloride provides a chlorine atom that can undergo a nucleophilic reaction with the imidazoline nitrogen atom to form a quaternary ammonium salt structure. Finally, thiourea reacts with the imidazoline quaternary ammonium salt to introduce a thiourea group to obtain a thiourea-based imidazoline quaternary ammonium salt. The specific reaction formula is as follows:

[0014]

[0015] Optionally, the high temperature reaction time in step S1 is 1.5-2 hours and the temperature is 90-120°C.

[0016] Optionally, after the high-temperature reaction in step S1, the temperature is lowered to 50-60° C., and a mixed solvent of acetone and toluene is added for recrystallization and purification to finally obtain a thiourea imidazoline quaternary ammonium salt.

[0017] Optionally, the mixing ratio of acetone to toluene in the mixed solvent of acetone and toluene is (1-2):1.

[0018] Optionally, the octadecylamine polyoxyethylene ether in step S2 is prepared by uniformly mixing octadecylamine and potassium hydroxide, heating to 90-100° C. in a nitrogen environment, slowly adding atomized ethylene oxide after evacuation, reacting for 0.5-1.5 h, cooling, and discharging to obtain the product.

[0019] Optionally, in step S2, 4-pyridyl amidoxime, silane and distilled water are heated and stirred, and isocyanate crosslinking agent, octadecylamine polyoxyethylene ether and ammonia water are added and stirred for 30 minutes to obtain a neutralization component.

[0020] Optionally, in step S3, the heating and stirring temperature is 90° C., the rotation speed is 400 r / min, and the time is 30 min.

[0021] Optionally, the silane in step S3 is any one of 3-aminopropyltriethoxysilane, γ-aminopropyltriethoxysilane, and γ-isocyanatepropyltrialkoxysilane.

[0022] Optionally, the neutralizing corrosion inhibitor comprises the following raw materials in parts by weight: 30 parts of corrosion inhibition component, 20 parts of neutralizing component, 5 parts of lignin sulfonate, and 45 parts of distilled water;

[0023] Among them, the corrosion inhibition component includes the following raw materials in mass parts: 10-15 parts of imidazoline quaternary ammonium salt and 1-3 parts of thiourea; the neutralization component includes the following raw materials in mass parts: 3-8 parts of 4-pyridyl amidoxime, 0.3-0.5 parts of silane, 0.5-1 parts of isocyanate crosslinking agent, 10-15 parts of octadecylamine polyoxyethylene ether, and 1-5 parts of ammonia water.

[0024] The above technical solution of the present invention includes at least the following beneficial effects:

[0025] 1. The present invention utilizes the nitrogen atom in thiourea to undergo a substitution reaction with the amino group of imidazoline quaternary ammonium salt to obtain a thiourea-based imidazoline quaternary ammonium salt having a good adsorption and corrosion inhibition effect under neutral solution and medium and low temperature conditions. The nitrogen atom in the imidazoline quaternary ammonium salt forms a coordination bond with the metal surface, so that it is combined with the metal matrix to form a firm protective film, and the sulfur element in the thiourea group is combined with the empty orbital of the metal surface to generate a sulfide protective layer that is adsorbed on the metal surface in the protective film to form a firmer and denser adsorption film, so as to slow down the corrosion of the metal surface and further improve the overall slow-release effect.

[0026] 2. In the neutralization component prepared by the present invention, the pyridine ring in 4-pyridyl amidoxime and ammonia water work together to neutralize the acidic substances in the solution to generate soluble 4-pyridyl amidine salts, thereby avoiding the occurrence of under-scale corrosion caused by the formation of crystalline salts and increasing the pH of the solution. At the same time, it is compounded with octadecylamine polyoxyethylene ether to increase the water solubility of octadecylamine polyoxyethylene ether. In addition, octadecylamine polyoxyethylene ether reacts with metal ions through the alkalinity of its amine group to reduce metal corrosion and further improve the neutralization and sustained-release performance.

[0027] 3. The present invention utilizes the property of octadecylamine polyoxyethylene ether to form a dense monolayer adsorption film on the metal surface, adsorbs the neutralizing component on the metal surface, further enhances the density and stability of the film, and improves the metal corrosion inhibition effect. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described in combination with the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0029] Example 1

[0030] 26 parts of oleic acid, 12 parts of diethylenetriamine and 40 parts of xylene were stirred and mixed uniformly at high speed, heated at 140°C for 2h, heated to 200°C and heated for 2h for cyclization reaction, cooled to 95°C, slowly added 12 parts of benzyl chloride, and the resulting mixture was heated under reflux for 3h, and finally the solvent was evaporated to obtain imidazoline quaternary ammonium salt. 13 parts of imidazoline quaternary ammonium salt were mixed uniformly with 3 parts of thiourea, reacted at 110°C for 1.5h, cooled to 50°C, and added a mixed solvent of acetone and toluene for recrystallization and purification to obtain thiourea imidazoline quaternary ammonium salt as a corrosion inhibition component; wherein the mixing ratio of acetone to toluene in the mixed solvent of acetone and toluene is 2:1.

[0031] 15 parts of octadecylamine and 0.15 parts of potassium hydroxide were mixed evenly, heated to 90°C in a nitrogen environment, 24.6 parts of atomized ethylene oxide were slowly added after vacuuming, and then reacted for 0.5h, cooled, and discharged to obtain octadecylamine polyoxyethylene ether. 3 parts of 4-pyridyl amidoxime, 0.3 parts of 3-aminopropyltriethoxysilane and 50 parts of distilled water were mixed, stirred at 90°C at 400r / min for 30min, 0.5 parts of isocyanate crosslinker, 10 parts of octadecylamine polyoxyethylene ether, and 1 part of ammonia water were added and stirred for 30min to obtain a neutralization component.

[0032] 30 parts of the corrosion inhibition component, 20 parts of the neutralization component, 5 parts of lignin sulfonate and 45 parts of distilled water were stirred evenly to obtain a neutralization corrosion inhibitor.

[0033] Example 2

[0034] 25 parts of oleic acid, 10 parts of diethylenetriamine and 40 parts of xylene were stirred and mixed uniformly at high speed, heated at 150°C for 2 hours, heated to 190°C and heated for another 2 hours for cyclization reaction, cooled to 90-100°C, slowly added 10 parts of benzyl chloride, and the resulting mixture was heated under reflux for 5 hours, and finally the solvent was evaporated to obtain imidazoline quaternary ammonium salt. 10 parts of imidazoline quaternary ammonium salt were mixed uniformly with 1 part of thiourea, reacted at 90°C for 2 hours, cooled to 60°C, and added with a mixed solvent of acetone and toluene for recrystallization and purification to obtain thiourea imidazoline quaternary ammonium salt as a corrosion inhibition component; wherein the mixing ratio of acetone to toluene in the mixed solvent of acetone and toluene was 1:1.

[0035] 15 parts of octadecylamine and 0.15 parts of potassium hydroxide were mixed evenly, heated to 100°C in a nitrogen environment, 24.6 parts of atomized ethylene oxide were slowly added after vacuuming, and then reacted for 1.5 hours, cooled, and discharged to obtain octadecylamine polyoxyethylene ether. 8 parts of 4-pyridyl amidoxime, 0.5 parts of 3-aminopropyltriethoxysilane and 50 parts of distilled water were mixed, stirred at 90°C at 400r / min for 30 minutes, 1 part of isocyanate crosslinking agent, 13 parts of octadecylamine polyoxyethylene ether, and 5 parts of ammonia water were added and stirred for 30 minutes to obtain a neutralization component.

[0036] 30 parts of the corrosion inhibition component, 20 parts of the neutralization component, 5 parts of lignin sulfonate and 45 parts of distilled water were stirred evenly to obtain a neutralization corrosion inhibitor.

[0037] Example 3

[0038] 30 parts of oleic acid, 15 parts of diethylenetriamine and 40 parts of xylene were stirred and mixed uniformly at high speed, heated at 130°C for 2h, heated to 210°C and heated for another 2h for cyclization reaction, cooled to 100°C, slowly added 13 parts of benzyl chloride, and the resulting mixture was heated under reflux for 5h, and finally the solvent was evaporated to obtain imidazoline quaternary ammonium salt. 15 parts of imidazoline quaternary ammonium salt were mixed uniformly with 3 parts of thiourea, reacted at 120°C for 1.5h, cooled to 60°C, and added a mixed solvent of acetone and toluene for recrystallization and purification to obtain thiourea imidazoline quaternary ammonium salt as a corrosion inhibition component; wherein the mixing ratio of acetone to toluene in the mixed solvent of acetone and toluene is 1.5:1.

[0039] 15 parts of octadecylamine and 0.15 parts of potassium hydroxide were mixed evenly, heated to 90°C in a nitrogen environment, 24.6 parts of atomized ethylene oxide were slowly added after vacuuming, and then reacted for 1 hour, cooled, and discharged to obtain octadecylamine polyoxyethylene ether. 6 parts of 4-pyridyl amidoxime, 0.4 parts of γ-isocyanate propyl trialkoxysilane and 50 parts of distilled water were mixed, stirred at 90°C at 400r / min for 30 minutes, 0.7 parts of isocyanate crosslinking agent, 12 parts of octadecylamine polyoxyethylene ether, and 4 parts of ammonia water were added and stirred for 30 minutes to obtain a neutralization component.

[0040] 30 parts of the corrosion inhibition component, 20 parts of the neutralization component, 5 parts of lignin sulfonate and 45 parts of distilled water were stirred evenly to obtain a neutralization corrosion inhibitor.

[0041] Example 4

[0042] 26 parts of oleic acid, 10 parts of diethylenetriamine and 40 parts of xylene were stirred and mixed uniformly at high speed, heated at 140°C for 2 hours, heated to 190°C and heated for another 2 hours for cyclization reaction, cooled to 90°C, slowly added 10 parts of benzyl chloride, and the resulting mixture was heated under reflux for 3 hours, and finally the solvent was evaporated to obtain imidazoline quaternary ammonium salt. 10 parts of imidazoline quaternary ammonium salt were mixed uniformly with 1 part of thiourea, reacted at 90°C for 2 hours, cooled to 50°C, and added with a mixed solvent of acetone and toluene for recrystallization and purification to obtain thiourea imidazoline quaternary ammonium salt as a corrosion inhibition component; wherein the mixing ratio of acetone to toluene in the mixed solvent of acetone and toluene is 2:1.

[0043] 15 parts of octadecylamine and 0.15 parts of potassium hydroxide were mixed evenly, heated to 90°C in a nitrogen environment, 24.6 parts of atomized ethylene oxide were slowly added after vacuuming, and then reacted for 1.5 hours, cooled, and discharged to obtain octadecylamine polyoxyethylene ether. 3 parts of 4-pyridyl amidoxime, 0.3 parts of γ-aminopropyltriethoxysilane and 50 parts of distilled water were mixed, stirred at 400r / min at 90°C for 30 minutes, 0.5 parts of isocyanate crosslinker, 10 parts of octadecylamine polyoxyethylene ether, and 1 part of ammonia water were added and stirred for 30 minutes to obtain a composite neutralizer.

[0044] 30 parts of the corrosion inhibition component, 20 parts of the neutralization component, 5 parts of lignin sulfonate and 45 parts of distilled water were stirred evenly to obtain a neutralization corrosion inhibitor.

[0045] Example 5

[0046] 28 parts of oleic acid, 12 parts of diethylenetriamine and 40 parts of xylene were stirred and mixed uniformly at high speed, heated at 140°C for 2 hours, heated to 210°C and heated for another 2 hours for cyclization reaction, cooled to 95°C, 11 parts of benzyl chloride were slowly added, and the resulting mixture was heated under reflux for 4 hours, and finally the solvent was evaporated to obtain imidazoline quaternary ammonium salt. 13 parts of imidazoline quaternary ammonium salt were mixed uniformly with 2 parts of thiourea, reacted at 110°C for 1.5 hours, cooled to 55°C, and a mixed solvent of acetone and toluene was added for recrystallization and purification to obtain thiourea imidazoline quaternary ammonium salt as a corrosion inhibition component; wherein the mixing ratio of acetone to toluene in the mixed solvent of acetone and toluene was 1.5:1.

[0047] 15 parts of octadecylamine and 0.15 parts of potassium hydroxide were mixed evenly, heated to 90°C in a nitrogen environment, 24.6 parts of atomized ethylene oxide were slowly added after vacuuming, and then reacted for 1 hour, cooled, and discharged to obtain octadecylamine polyoxyethylene ether. 6 parts of 4-pyridyl amidoxime, 0.35 parts of γ-aminopropyltriethoxysilane and 50 parts of distilled water were mixed, stirred at 400r / min at 90°C for 30 minutes, 0.7 parts of isocyanate crosslinking agent, 12 parts of octadecylamine polyoxyethylene ether, and 3 parts of ammonia water were added and stirred for 30 minutes to obtain a neutralization component.

[0048] 30 parts of the corrosion inhibition component, 20 parts of the neutralization component, 5 parts of lignin sulfonate and 45 parts of distilled water were stirred evenly to obtain a neutralization corrosion inhibitor.

[0049] Example 6

[0050] 27 parts of oleic acid, 14 parts of diethylenetriamine and 40 parts of xylene were stirred and mixed uniformly at high speed, heated at 135°C for 2 hours, heated to 190°C and heated for another 2 hours for cyclization reaction, cooled to 90-100°C, 12 parts of benzyl chloride were slowly added, and the resulting mixture was heated under reflux for 5 hours, and finally the solvent was evaporated to obtain imidazoline quaternary ammonium salt. 15 parts of imidazoline quaternary ammonium salt were mixed uniformly with 1 part of thiourea, reacted at 90-120°C for 1.5 hours, cooled to 60°C, and a mixed solvent of acetone and toluene was added for recrystallization and purification to obtain thiourea imidazoline quaternary ammonium salt as a corrosion inhibition component; wherein the mixing ratio of acetone to toluene in the mixed solvent of acetone and toluene was 1:1.

[0051] 15 parts of octadecylamine and 0.15 parts of potassium hydroxide were mixed evenly, heated to 90°C in a nitrogen environment, 24.6 parts of atomized ethylene oxide were slowly added after vacuuming, and then reacted for 1 hour, cooled, and discharged to obtain octadecylamine polyoxyethylene ether. 3 parts of 4-pyridyl amidoxime, 0.3 parts of γ-isocyanate propyl trialkoxysilane and 50 parts of distilled water were mixed, stirred at 90°C at 400r / min for 30 minutes, 0.5 parts of isocyanate crosslinking agent, 15 parts of octadecylamine polyoxyethylene ether, and 1 part of ammonia water were added and stirred for 30 minutes to obtain a neutralization component.

[0052] 30 parts of the corrosion inhibition component, 20 parts of the neutralization component, 5 parts of lignin sulfonate and 45 parts of distilled water were stirred evenly to obtain a neutralization corrosion inhibitor.

[0053] The present invention also carries out comparative examples and related tests.

[0054] Comparative Example 1

[0055] Compared with Example 1, the difference is that the thiourea imidazoline quaternary ammonium salt is not prepared, and the imidazoline quaternary ammonium salt is directly used as the corrosion inhibition component, and the other components and preparation steps are completely the same to prepare a neutralizing corrosion inhibitor.

[0056] Comparative Example 2

[0057] Compared with Example 1, the difference is that in the process of preparing the neutralizing component, no silane is added to treat 4-pyridyl amidoxime, and no isocyanate is added for cross-linking, that is, 3 parts of 4-pyridyl amidoxime, 50 parts of distilled water, 10 parts of octadecylamine polyoxyethylene ether, and 1 part of ammonia water are mixed and stirred for 30 minutes to obtain the neutralizing component; the other components and preparation steps are completely consistent, and finally a neutralizing corrosion inhibitor is prepared.

[0058] Comparative Example 3

[0059] Compared with Example 1, the difference is that 4-pyridyl amidoxime is directly used as the neutralizing component, and the other components and preparation steps are completely consistent to prepare a neutralizing corrosion inhibitor.

[0060] Comparative Example 4

[0061] Compared with Example 1, the difference is that octadecylamine polyoxyethylene ether is directly used as the neutralizing component, and the other components and preparation steps are completely consistent to prepare a neutralizing corrosion inhibitor.

[0062] Performance testing

[0063] The neutralization corrosion inhibitors obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were subjected to basic performance tests according to the national standard GB / T35509-2017 Application and Evaluation of Corrosion Inhibitors in Oil and Gas Fields. The basic performance test results are shown in Table 1.

[0064] Table 1

[0065]

[0066] As can be seen from Table 1, Examples 1 to 6 all have good water solubility and are uniform liquids, and the average pour point of Examples 1 to 6 is ≤-10°C, which meets the national standard.

[0067] Combined with the results of Table 1, it is found that in Comparative Example 2, 4-pyridyl amidoxime is not treated with silane and isocyanate is not added for cross-linking, and Comparative Example 3 directly uses 4-pyridyl amidoxime as a neutralizing component, resulting in a small amount of precipitation of the neutralizing corrosion inhibitor. This is because the solubility of 4-pyridyl amidoxime in water is limited, which in turn has a certain effect on the pour point; Comparative Example 4 directly uses octadecylamine polyoxyethylene ether as a neutralizing component. Although octadecylamine polyoxyethylene ether has good water solubility, its stability in strong acid or high temperature environment is poor, resulting in a small amount of precipitation of the prepared neutralizing corrosion inhibitor, which can also maintain a uniform liquid state at room temperature; the pH value of the neutralizing corrosion inhibitor prepared in Comparative Examples 1 to 4 is slightly lower than that in Examples 1 to 6, which is configured to be an aqueous solution with a volume concentration of 10%, thereby having a certain effect on the corrosion inhibition effect.

[0068] The corrosion inhibition performance of Examples 1 to 6 and Comparative Examples 1 to 4 was evaluated by the static corrosion rate evaluation method at normal pressure in SY / T5405-1996 "Test Methods and Evaluation Indicators for Acidification Corrosion Inhibitors". The neutralized corrosion inhibitors prepared in Examples 1 to 6 and Comparative Examples 1 to 4 were prepared into a 2% aqueous solution by volume in a volumetric flask. The prepared test pieces were placed in a 15% hydrochloric acid solution and a specified amount of neutralized corrosion inhibitor in a 90°C constant temperature water bath for 4 hours to perform a static hanging test, and the corrosion rate was measured and compared with the blank test performed at the same time to calculate the corrosion inhibition rate. The results of pH value, corrosion rate and corrosion inhibition rate are shown in Table 2.

[0069] Table 2

[0070]

[0071] As shown in Table 2, the corrosion rate of the neutralization corrosion inhibitor prepared in Examples 1 to 6 is significantly reduced compared to that in Comparative Examples 1 to 4, and the corrosion inhibition rate is significantly improved, all reaching more than 90%. Among them, Comparative Example 1 only uses imidazoline quaternary ammonium salt as the corrosion inhibition component and Comparative Example 4 only uses octadecylamine polyoxyethylene ether as the neutralization component. The results show that the corrosion rate in a 90°C constant temperature water bath is significantly improved, thereby significantly reducing the corrosion inhibition rate. Although Comparative Example 2 adds octadecylamine polyoxyethylene ether and 4-pyridyl amidoxime during the preparation of the neutralization component, the corrosion inhibition rate is improved compared to Comparative Examples 3 and Comparative Example 4, which only adds one of them, but there is still a big gap with Example 1.

[0072] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a neutralizing corrosion inhibitor, characterized in that: The following steps are involved: S1. Mix the imidazoline quaternary ammonium salt and thiourea uniformly, react at high temperature for 1.5-2h at a temperature of 90-120°C, cool to 50-60°C, and recrystallize to obtain a thiourea-based imidazoline quaternary ammonium salt, i.e., a corrosion inhibition component; S2, 4-pyridyl amidoxime, silane and distilled water were mixed and heated with stirring, the temperature of heating and stirring was 90°C, the speed was 400r / min, the time was 30min, isocyanate crosslinking agent, octadecylamine polyoxyethylene ether, ammonia water were added, and stirring was continued for 30min to obtain a neutralization component; S3, stirring the corrosion inhibition component, the neutralization component, the lignin sulfonate and the distilled water to obtain a neutralization corrosion inhibitor; The imidazoline quaternary ammonium salt is prepared by mixing oleic acid, diethylenetriamine and xylene by high-speed stirring, heating at 130-150° C. for 2 hours, heating to 190-210° C. for further 2 hours for cyclization reaction, cooling to 90-100° C., slowly adding benzyl chloride, heating the obtained mixture under reflux for 3-5 hours, and finally evaporating the solvent to obtain the imidazoline quaternary ammonium salt.

2. The method for preparing a neutralizing corrosion inhibitor according to claim 1, characterized in that: After the high temperature reaction in step S1, the temperature is lowered to 50-60° C., and a mixed solvent of acetone and toluene is added for recrystallization and purification to finally obtain thiourea imidazoline quaternary ammonium salt.

3. The method for preparing a neutralizing corrosion inhibitor according to claim 2, characterized in that: The mixing ratio of acetone to toluene in the mixed solvent of acetone and toluene is (1-2):

1.

4. The method for preparing a neutralizing corrosion inhibitor according to claim 1, characterized in that: The octadecylamine polyoxyethylene ether in step S2 is prepared by uniformly mixing octadecylamine and potassium hydroxide, heating to 90-100° C. in a nitrogen environment, slowly adding atomized ethylene oxide after vacuuming, reacting for 0.5-1.5 hours, cooling, and discharging to obtain the obtained product.

5. The method for preparing a neutralizing corrosion inhibitor according to claim 1, characterized in that: The silane in step S3 is any one of 3-aminopropyltriethoxysilane, γ-aminopropyltriethoxysilane and γ-isocyanatepropyltrialkoxysilane.

6. A method for preparing a neutralizing corrosion inhibitor according to any one of claims 1 to 5, characterized in that: The neutralizing corrosion inhibitor comprises the following raw materials in parts by weight: 30 parts of corrosion inhibition component, 20 parts of neutralizing component, 5 parts of lignin sulfonate, and 45 parts of distilled water; Among them, the corrosion inhibition component includes the following raw materials in mass parts: 10-15 parts of imidazoline quaternary ammonium salt and 1-3 parts of thiourea; the neutralization component includes the following raw materials in mass parts: 3-8 parts of 4-pyridyl amidoxime, 0.3-0.5 parts of silane, 0.5-1 parts of isocyanate crosslinking agent, 10-15 parts of octadecylamine polyoxyethylene ether, and 1-5 parts of ammonia water.

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