Preparation method of modified imidazoline type quaternary ammonium salt and modified imidazoline corrosion inhibitor

Abstract

The application relates to a preparation method of modified imidazoline type quaternary ammonium salt and a modified imidazoline corrosion inhibitor, and belongs to the technical field of oil and gas field chemicals. The preparation method comprises the following steps: citric acid and polyamine are subjected to an amidation dehydration reaction, and then subjected to a cyclization dehydration reaction to generate an imidazoline intermediate; the imidazoline intermediate is subjected to a substitution reaction, a coupling reaction and a quaternary ammonium reaction in sequence to generate the modified imidazoline type quaternary ammonium salt; the substitution reaction is a reaction of the imidazoline intermediate and a hydrogen halide acid; the coupling reaction is a reaction of a substitution product and a Grignard reagent; and the quaternary ammonium reaction is a reaction of a coupling reaction product and a benzyl halide. The modified imidazoline type quaternary ammonium salt prepared by the application can be more firmly adsorbed on the surface of metal materials, change the oxidation and reduction potential of the metal materials, and also reduce the potential to achieve the corrosion inhibition purpose; in addition, the hydrophobic long-chain group in the modified imidazoline type quaternary ammonium salt can improve the corrosion inhibition performance of the compound. + ​

Description

Technical Field

[0001] The invention relates to a preparation method of a modified imidazoline type quaternary ammonium salt and a modified imidazoline corrosion inhibitor, belonging to the technical field of oil and gas field chemicals. Background Art

[0002] Metal corrosion is a widespread problem across all industries, causing economic losses and damaging the ecological environment. Therefore, adding corrosion inhibitors is a long-term and effective measure to prevent metal corrosion in environmental media. In oil and gas field production systems, the pH value of the aqueous medium is generally between 5.5 and 6.5, with high mineralization and high levels of CO2. This leads to widespread and severe corrosion of pipelines and equipment in the production system.

[0003] Currently, the primary measure for on-site corrosion control in oil and gas fields is to add corrosion inhibitors to the wellbore. A reasonable dosing cycle and dosage can effectively slow the corrosion of oil and water pipeline equipment. The corrosion inhibition mechanism of the corrosion inhibitors added to major oil and gas fields is mostly based on chemical adsorption. The hydrophilic polar groups of highly electronegative elements such as O, N, P, and S in the corrosion inhibitors adsorb onto active points on the metal surface or the entire surface, changing the metal surface charge state and interfacial properties, stabilizing the energy state of the metal surface, increasing the activation energy of the corrosion reaction, and slowing the corrosion rate. Currently, imidazoline-type corrosion inhibitors are commonly used in major oil and gas fields, and there is considerable research on the synthesis and inhibition mechanism of imidazoline corrosion inhibitors.

[0004] A Chinese invention patent application, publication number CN115710229A, discloses a water-soluble bisimidazoline corrosion inhibitor and its preparation method. The method involves subjecting an organic acid and a polyamine to an amidation reaction at 140-160°C for 2 hours in the presence of xylene as a water-carrying agent. The reaction is then heated to 200-220°C for a cyclization reaction for 6 hours to obtain an imidazoline intermediate. The intermediate is then reacted with a quaternary ammonium reagent at 80-90°C for 5 hours to obtain the water-soluble bisimidazoline corrosion inhibitor. This corrosion inhibitor, which possesses a bisimidazoline structure and double functional groups, exhibits excellent water solubility and high surface activity. It exhibits stronger adsorption on metal surfaces than conventional monocyclic imidazoline corrosion inhibitors and exhibits a high corrosion inhibition rate. However, the symmetrical bisimidazoline hydrophobic groups are prone to folding, affecting the inhibitor's corrosion inhibition properties. Furthermore, single imidazoline corrosion inhibitors exhibit poor pitting resistance and high-temperature resistance in highly salinized oil and gas wells.

[0005] Chinese invention patent application publication number CN115820237A discloses a corrosion inhibitor for carbon dioxide flooding and its preparation method. The inhibitor is formulated from a modified imidazoline derivative, a surfactant, hexamethylenetetramine, iodide, propargyl alcohol, and a solvent. However, the invention provides a modified imidazoline derivative for use as a corrosion inhibitor. However, the inhibitor's adsorption and corrosion inhibition properties are relatively low, and propargyl alcohol is highly toxic, posing significant safety risks during preparation, transportation, and on-site refilling. Summary of the Invention

[0006] The first object of the present invention is to provide a method for preparing a modified imidazoline-type quaternary ammonium salt, so as to solve the problems of poor adsorption performance, pitting resistance and high temperature resistance of imidazoline-type corrosion inhibitors in the prior art.

[0007] The second object of the present invention is to provide a modified imidazoline corrosion inhibitor to solve the problem in the prior art that the liquid corrosion inhibitor for oil and water wells is not tightly bonded to the surface of the pipe and is easily eroded.

[0008] In order to achieve the above objectives, the first technical solution of the present invention is:

[0009] A method for preparing a modified imidazoline quaternary ammonium salt comprises the following steps: citric acid and polyamine undergo amidation dehydration reaction, followed by cyclization dehydration reaction to generate an imidazoline intermediate, and the imidazoline intermediate undergoes substitution reaction, coupling reaction and quaternization reaction in sequence to generate a modified imidazoline quaternary ammonium salt;

[0010] The substitution reaction is a reaction between an imidazoline intermediate and a hydrohalic acid; the coupling reaction is a reaction between a substitution product and a Grignard reagent; and the quaternization reaction is a reaction between a coupling reaction product and a benzyl halide.

[0011] The invention conducts an amidation dehydration reaction on citric acid and polyamine, and then conducts a cyclization dehydration reaction to generate an imidazoline intermediate containing three five-membered rings. The intermediate is then reacted with a hydrohalic acid to replace the hydroxyl group of the intermediate with a halogen group. The obtained substance is then subjected to a coupling reaction with a Grignard reagent to replace the halogen group (i.e., a hydrophobic long-chain group) in the intermediate with an alkyl group in the Grignard reagent. Finally, the five-membered ring of the imidazoline quaternary ammonium salt is modified with a benzyl halide to obtain a modified imidazoline quaternary ammonium salt.

[0012] The modified imidazoline quaternary ammonium salt of the present invention has three five-membered rings, and the C=N double bond on the ring and the lone pair of electrons on the N atom undergo covalent adsorption on the metal surface, which can be more firmly adsorbed on the surface of the metal material, changing the H + The redox potential of the modified imidazoline quaternary ammonium salt can be increased, and at the same time, it can also complex some oxidants in the protective medium, thereby reducing its potential to achieve the purpose of corrosion inhibition. In addition, the hydrophobic long-chain groups (R groups) in the modified imidazoline quaternary ammonium salt are directionally arranged on the metal surface to form a dense hydrophobic layer, which can not only hinder the diffusion and migration of corrosion products, but also improve the corrosion inhibition performance of the compound.

[0013] In order to promote the occurrence of the amidation dehydration reaction, preferably, the citric acid and the polyamine undergo the amidation dehydration reaction in a solvent, and the solvent is xylene. Xylene not only acts as a solvent in the reaction, but also acts as a water-carrying agent to promote the reaction.

[0014] More preferably, the molar ratio of citric acid to xylene is (1-1.05):(0.5-0.8).

[0015] In order to improve the efficiency of the amidation dehydration reaction and the substitution reaction, preferably, the molar ratio of the citric acid to the polyamine is (1-1.05): (3.5-4), and the molar ratio of the hydrohalic acid to the citric acid is (0.5-0.7): (1-1.05).

[0016] More preferably, the hydrohalic acid is one or more of hydroiodic acid, hydrobromic acid, and hydrochloric acid. The substitution reaction activities of these three hydrohalic acids with the hydroxyl group on the imidazoline intermediate are hydroiodic acid>hydrobromic acid>hydrochloric acid.

[0017] In order to facilitate the substitution reaction, preferably, the hydrohalic acid is hydroiodic acid.

[0018] In order to ensure the synthesis of modified imidazoline quaternary ammonium salt, preferably, the molar ratio of the Grignard reagent to citric acid is (1.1-1.3): (1-1.05), and the molar ratio of the benzyl halide to citric acid is (3.5-4.0): (1-1.05).

[0019] More preferably, the Grignard reagent is R-Mg-X, where R is a C6-C8 n-alkyl group and X is bromine or iodine, such as heptylmagnesium bromide.

[0020] More preferably, the benzyl halide is benzyl chloride. The chlorine in benzyl chloride has a strong electronegativity and is more reactive, which is more conducive to the reaction.

[0021] Preferably, the temperature of the amidation dehydration reaction is 140-160° C., and the reaction time is 2.5-3 h. At this temperature, citric acid and polyamines are prone to undergo amidation dehydration reaction, which facilitates the formation of intermediates. The temperature of the substitution reaction is 20-40° C., and the reaction time is 0.5-2 h. When the substitution reaction is carried out at this temperature, the substitution efficiency is high.

[0022] Preferably, the coupling reaction temperature is 145-160°C for 3-4 hours, and the quaternization reaction temperature is 100-120°C for 3-5 hours. Reacting at this temperature facilitates modification of the five-membered ring.

[0023] In order to make the amino groups in the polyamine form a five-membered ring, preferably, the temperature of the cyclodehydration reaction is 200-230° C., and the reaction time is 4-6 hours.

[0024] In order to improve the adsorptivity of the modified imidazoline type quaternary ammonium salt, preferably, the polyamine is polyethylene polyamine. Polyethylene polyamine contains two or more vinyl groups and three or more amino groups. The polyethylene polyamine is one or more of diethylene triamine, triethylene tetramine, and tetraethylene pentamine. More preferably, triethylene tetramine is used. The modified imidazoline type quaternary ammonium salt obtained with triethylene tetramine has a better sustained-release effect and a high sustained-release rate.

[0025] The second technical solution of the present invention is:

[0026] A modified imidazoline corrosion inhibitor is composed of the following components: modified imidazoline quaternary ammonium salt, pyridine, hexamethylenetetramine, thiourea, and water;

[0027] The modified imidazoline type quaternary ammonium salt is prepared by the above-mentioned preparation method of the modified imidazoline type quaternary ammonium salt.

[0028] The modified imidazoline corrosion inhibitor of the present invention is obtained by compounding a modified imidazoline quaternary ammonium salt, pyridine, urotropine, thiourea, and water. The three five-membered rings and hydrophobic long-chain groups of the modified imidazoline quaternary ammonium salt enhance the corrosion inhibitor's adsorption capacity and sustained-release effect on the surface of metal materials. The nitrogen atoms on the six-membered heterocyclic ring in the pyridine molecular structure form coordination bonds with iron atoms on the steel surface, allowing adsorption on the steel surface. The lone electron pairs on the nitrogen atoms in the tetranitrogen heterocyclic ring structure of urotropine form coordination bonds with iron atoms on the steel surface, allowing adsorption on the steel surface. The sulfur atoms and nitrogen atoms in the thiourea molecular structure form coordination bonds with iron atoms on the steel surface, inhibiting corrosion reactions on the metal surface. All three auxiliary agents can synergistically adsorb with the modified triimidazoline quaternary ammonium salt, preventing the adsorption film from falling off at high temperatures and improving corrosion inhibition performance. The modified imidazoline corrosion inhibitor of the present invention has the advantages of high corrosion inhibition rate, good economic efficiency, and strong safety.

[0029] In order to make the modified imidazoline corrosion inhibitor have better corrosion inhibition performance, it is preferably composed of the following components in parts by mass: 15-20 parts of modified imidazoline quaternary ammonium salt, 1-3 parts of pyridine, 1-3 parts of urotropine, 3-8 parts of thiourea, and 18-22 parts of water. DETAILED DESCRIPTION

[0030] The preparation method of the modified imidazoline type quaternary ammonium salt of the present invention adopts the following steps:

[0031] (1) Mixing citric acid and polyamine in a solvent, heating to 140-160°C, stirring, condensing and refluxing for 2.5-3 hours to carry out amidation dehydration reaction;

[0032] (2) heating to 200-230°C and carrying out cyclodehydration reaction for 4-6 hours;

[0033] (3) cooling to 135-145°C and distilling for 0.5-1 h to distill off the excess solvent and polyamine and obtain the trimidazoline intermediate;

[0034] (4) mixing the trimidazoline intermediate with a hydrogen halide acid, maintaining the temperature at 20-40°C and stirring for 0.5-2 h to perform a substitution reaction and obtain a substituted product;

[0035] (5) mixing the substituted product with a Grignard reagent R-Mg-X, heating to 145-160°C and refluxing for 3-4 h to perform a coupling reaction, and then cooling to room temperature to obtain a coupled product;

[0036] (6) mixing the coupled product with a benzyl halide, heating to 100-120°C and refluxing for 3-5 h to perform a quaternary ammonium reaction, and then cooling to obtain the modified trimidazoline quaternary ammonium salt.

[0037] The reaction process involved in the above preparation method is as follows:

[0038]

[0039]

[0040] The technical solutions of the present application are further described below in combination with specific embodiments.

[0041] I. Embodiment of the preparation method of the modified imidazoline quaternary ammonium salt of the present application

[0042] Embodiment 1

[0043] The preparation method of the modified imidazoline quaternary ammonium salt of the present embodiment adopts the following steps:

[0044] (1) adding 1 mol of citric acid, 3.5 mol of triethylenetetramine and 0.5 mol of dimethylbenzene into a reaction kettle, heating to 145°C, stirring and condensing refluxing for 3 h to perform an amide dehydration reaction;

[0045] (2) heating to 210°C and performing a cyclization dehydration reaction for 4 h;

[0046] (3) cooling to 140°C and distilling for 40 min to distill off the excess dimethylbenzene and triethylenetetramine and obtain the trimidazoline intermediate.

[0047] (4) adding 0.5 mol of hydroiodic acid into the trimidazoline intermediate obtained in step (3), maintaining the temperature at 25°C and stirring for 0.5 h to perform a substitution reaction and obtain a mixture I;

[0048] (5) adding 1.1 mol of hexyl magnesium bromide into the mixture I of step (4), heating to 150°C, refluxing for 3.5 h to perform a coupling reaction, and then cooling to room temperature to obtain a mixture II;

[0049] (6) To the mixture II of step (5), 3.5 mol of benzyl chloride was added, heated to 100°C, refluxed for 3h, and after cooling, the red-brown viscous liquid obtained was the modified tri-imidazoline quaternary ammonium salt, with an active ingredient content of 76%.

[0050] Example 2

[0051] The preparation method of the modified imidazoline type quaternary ammonium salt of this example used the following steps:

[0052] (1) 1 mol of citric acid, 3.7 mol of triethylenetetramine, and 0.5 mol of dimethylbenzene were added to a reaction kettle, heated to 150°C, stirred, and condensed to reflux for 2.5h to perform an amidation dehydration reaction;

[0053] (2) The temperature was further increased to 220°C, and the reaction was performed for 4.5h to perform a cyclization dehydration reaction;

[0054] (3) The temperature was decreased to 140°C, and the reaction was performed for 0.5h to distill excess dimethylbenzene and triethylenetetramine, and obtain a tri-imidazoline intermediate;

[0055] (4) 0.6 mol of hydriodic acid was added to the tri-imidazoline intermediate obtained in step (3), and the temperature was maintained at 30°C, and the reaction was performed for 1h to perform a substitution reaction, and obtain mixture I;

[0056] (5) 1.1 mol of heptyl magnesium bromide was added to the mixture I of step (4), heated to 150°C, refluxed for 3h to perform a coupling reaction, and after cooling to room temperature, mixture II was obtained;

[0057] (6) To the mixture II of step (5), 3.8 mol of benzyl chloride was added, heated to 110°C, refluxed for 3.5h, and after cooling, the red-brown viscous liquid obtained was the modified tri-imidazoline quaternary ammonium salt, with an active ingredient content of 76%.

[0058] Examples 3-8

[0059] The preparation method of the modified imidazoline type quaternary ammonium salt of examples 3-8 used the following steps:

[0060] (1) Citric acid, triethylenetetramine, and dimethylbenzene were added to a reaction kettle in proportion, heated to a certain temperature, stirred, and condensed to reflux for a certain time to perform an amidation dehydration reaction;

[0061] (2) The temperature was further increased to a certain temperature, and the reaction was performed for a certain time to perform a cyclization dehydration reaction;

[0062] (3) The temperature was decreased to a certain temperature, and the reaction was performed for a certain time to distill excess dimethylbenzene and triethylenetetramine, and obtain a tri-imidazoline intermediate;

[0063] (4) adding hydroiodic acid to the triimidazoline intermediate obtained in step (3) in proportion, heating to a certain temperature, and refluxing for a certain time to carry out a substitution reaction to obtain a mixture I;

[0064] (5) adding a Grignard reagent R-Mg-X to the mixture I of step (4) in proportion, heating to a certain temperature, refluxing for a certain time, performing a coupling reaction, and then cooling to room temperature to obtain a mixture II;

[0065] (6) Adding benzyl chloride to the mixture II of step (5) in proportion, heating to a certain temperature, refluxing for a certain time, carrying out a quaternization reaction, and cooling to obtain a modified triimidazoline quaternary ammonium salt.

[0066] The process parameters and Grignard reagents involved in the examples are shown in Table 1.

[0067] Table 1 Reagents and process parameters involved in the examples

[0068]

[0069]

[0070] 2. Examples of the Modified Imidazoline Corrosion Inhibitor of the Present Invention

[0071] Example 9

[0072] The modified imidazoline corrosion inhibitor of this embodiment is composed of the following components in parts by mass: 16 parts of the modified imidazoline quaternary ammonium salt prepared in Example 1, 2 parts of pyridine, 1 part of urotropine, 5 parts of thiourea, and 19 parts of water.

[0073] The specific method is to stir and mix the above ingredients.

[0074] Example 10

[0075] The modified imidazoline corrosion inhibitor of this embodiment is composed of the following components in parts by mass: 16.2 parts of the modified imidazoline quaternary ammonium salt prepared in Example 2, 2.1 parts of pyridine, 1.1 parts of urotropine, 5.1 parts of thiourea, and 19.1 parts of water.

[0076] Examples 11-16

[0077] The modified imidazoline corrosion inhibitors of Examples 11-16 were compounded with the modified imidazoline quaternary ammonium salts prepared in Examples 3-8, respectively. The specific composition of the ingredients is shown in Table 2.

[0078] Table 2 Modified imidazoline corrosion inhibitors of Examples 8-13

[0079]

[0080] 3. Comparative Examples

[0081] Comparative Example 1

[0082] The modified imidazoline corrosion inhibitor of this comparative example is composed of the following components in parts by mass: 40 parts of a modified imidazoline derivative, 15 parts of OP-10, 5 parts of urotropine, 3 parts of cuprous iodide, 6 parts of propargyl alcohol, 10 parts of water, and 30 parts of isopropyl alcohol.

[0083] The preparation method of the modified imidazoline derivative of this comparative example adopts the following steps:

[0084] (1) 2 mol of oleic acid and 2.2 mol of tetraethylenepentamine were mixed and reacted at 180° C. for 4.5 hours to obtain a first mixture;

[0085] (2) The first mixture obtained in step (1) was cooled to 50° C., 2 mol of carbon disulfide was added, the mixture was heated to 60° C. and reacted for 3 h, and then 90 g of a 20% formaldehyde solution was added and stirred until no heat was released to obtain a second mixture;

[0086] (3) adding 1.2 mol of phosphorous acid to the second mixture obtained in step (2), mixing, and then performing a third reaction to obtain a modified imidazoline derivative.

[0087] Comparative Example 2

[0088] The preparation method of the imidazoline corrosion inhibitor in this comparative example adopts the following steps: lauric acid and ethylenediamine are mixed in a molar ratio of 1:1.2 under the condition of 20% xylene as a water-carrying agent, an amidation reaction is carried out at 150°C for 2 hours, and the temperature is continuously raised to 220°C for a cyclization reaction for 6 hours to obtain an imidazoline intermediate; then the imidazoline intermediate and 1,6-dichlorohexane are mixed in a molar ratio of 2:0.8, and the mixture is reacted at 80°C for 5 hours to obtain a water-soluble bisimidazoline corrosion inhibitor.

[0089] Comparative Example 3

[0090] The preparation method of the corrosion inhibitor of this comparative example adopts the following steps: 1 mol of benzoic acid and 2.6 mol of xylene are added to an ethanol solution, and then 1.6 g of catalyst boric acid and a few grains of zeolite are added, and the mixture is heated to 100 ° C., 0.6 mol of diethylenetriamine is added dropwise, the temperature is adjusted to 90 ° C., 0.05 g of chain transfer agent AMSD is added, and then 1 mol of acrylic acid is added dropwise, and the reaction is continued for 3.5 hours to obtain the terpolymer corrosion inhibitor.

[0091] 5. Experimental Examples

[0092] In this experimental example, the corrosion inhibition performance of the corrosion inhibitors of Examples 1-16, Comparative Examples 2 and 3, and the imidazoline derivative in Comparative Example 1 was tested. The results are shown in Tables 3 and 4.

[0093] To evaluate the corrosion inhibition performance of the modified imidazoline quaternary ammonium salts of Examples 1-8 and the modified imidazoline liquid corrosion inhibitors of Examples 9-16, the static uniform corrosion inhibition rate, indoor dynamic uniform corrosion inhibition rate, and pitting corrosion inhibition rate of the modified imidazoline quaternary ammonium salts of Examples 1-8, the modified imidazoline liquid corrosion inhibitors of Examples 9-16, the corrosion inhibitors of Comparative Examples 2 and 3, and the imidazoline derivative of Comparative Example 1 were tested. The corrosion inhibition rate was tested according to the corrosion inhibition rate evaluation procedures specified in the standard SY / T 5273-2014, "Performance Indicators and Evaluation Methods for Corrosion Inhibitors for Oilfield Produced Water Treatment."

[0094] As shown in Table 3, the static uniform corrosion inhibition rate, indoor dynamic uniform corrosion inhibition rate, and pitting corrosion inhibition rate of the modified imidazoline type quaternary ammonium salts of Examples 1-8 of the present invention are all better than the corrosion inhibitors of Comparative Examples 2 and 3 and the imidazoline derivative in Comparative Example 1, and have excellent corrosion inhibition performance. The evaluation concentrations of Examples 1-8 in Table 3 refer to the concentrations of the active ingredients of the modified imidazoline type quaternary ammonium salts.

[0095] As shown in Table 4, the modified imidazoline corrosion inhibitors of Examples 9 to 16 of the present invention have excellent static uniform corrosion inhibition rate, indoor dynamic uniform corrosion inhibition rate and pitting corrosion inhibition rate.

[0096] Table 3 Corrosion inhibition performance test results

[0097]

[0098]

[0099] Table 4 Corrosion inhibition performance test results of corrosion inhibitors

[0100]

Claims

1. A method for preparing a modified imidazoline type quaternary ammonium salt, characterized in that: The following steps are involved: Citric acid and polyamine undergo amidation dehydration reaction, followed by cyclization dehydration reaction to generate an imidazoline intermediate, which then undergoes substitution reaction, coupling reaction and quaternization reaction in sequence to generate a modified imidazoline-type quaternary ammonium salt; The substitution reaction is a reaction between an imidazoline intermediate and a hydrohalic acid; the coupling reaction is a reaction between a substitution product and a Grignard reagent; the quaternization reaction is a reaction between a coupling reaction product and a benzyl halide; the polyamine is polyethylene polyamine; and the Grignard reagent is R-Mg-X, where R is a C6-C8 n-alkyl group and X is bromine or iodine.

2. The preparation method of modified imidazoline type quaternary ammonium salt according to claim 1, wherein The molar ratio of the citric acid to the polyamine is (1-1.05): (3.5-4), and the molar ratio of the hydrohalic acid to the citric acid is (0.5-0.7): (1-1.05).

3. The preparation method of modified imidazoline type quaternary ammonium salt according to claim 1, wherein The molar ratio of the Grignard reagent to the citric acid is (1.1-1.3): (1-1.05), and the molar ratio of the benzyl halide to the citric acid is (3.5-4.0): (1-1.05).

4. The preparation method of the modified imidazoline type quaternary ammonium salt according to claim 1 or 2, wherein The temperature of the amidation dehydration reaction is 140-160° C., and the reaction time is 2.5-3 hours; the temperature of the substitution reaction is 20-40° C., and the reaction time is 0.5-2 hours.

5. The preparation method of the modified imidazoline type quaternary ammonium salt according to claim 1 or 3, wherein The coupling reaction temperature is 145-160° C., and the reaction time is 3-4 hours; the quaternization reaction temperature is 100-120° C., and the reaction time is 3-5 hours.

6. The preparation method of modified imidazoline type quaternary ammonium salt according to claim 1, wherein The temperature of the cyclodehydration reaction is 200-230° C., and the reaction time is 4-6 hours.

7. A modified imidazoline corrosion inhibitor, characterized in that The invention is composed of the following components: modified imidazoline type quaternary ammonium salt, pyridine, hexamethylenetetramine, thiourea and water; The modified imidazoline type quaternary ammonium salt is prepared by the preparation method of the modified imidazoline type quaternary ammonium salt according to any one of claims 1 to 6.

8. The modified imidazoline corrosion inhibitor according to claim 7, characterized in that The invention is composed of the following components in parts by mass: 15-20 parts of modified imidazoline type quaternary ammonium salt, 1-3 parts of pyridine, 1-3 parts of urotropine, 3-8 parts of thiourea and 18-22 parts of water.

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