A type of halogen-free water-soluble long-chain imidazoline corrosion inhibitor containing a carboxylate structure, and its preparation method and application

Abstract

The present invention belongs to the field of chemical application, and specifically relates to a type of halogen-free water-soluble long-chain imidazoline corrosion inhibitor containing a carboxylate structure, and a preparation method and application thereof. The preparation method is to synthesize a long-chain imidazoline using a long-chain organic acid and diethylenetriamine as raw materials, react the long-chain imidazoline with citric anhydride, and then adjust the pH with an alkaline solution to obtain a halogen-free water-soluble long-chain imidazoline corrosion inhibitor containing a carboxylate structure. The corrosion inhibitor is characterized by good dispersibility in water. After being adsorbed on a metal, the carboxylate is converted into a carboxyl group in an acidic environment, so that the hydrophilicity of the corrosion inhibitor film is weakened, and it is not easy to fall off in an aqueous corrosive medium, thereby achieving a long-term corrosion inhibition effect.

Description

Technical Field

[0001] The invention belongs to the field of chemical application, and specifically relates to a halogen-free water-soluble long-chain imidazoline corrosion inhibitor containing a carboxylate structure, and a preparation method and application thereof. Background Art

[0002] The corrosion of metal materials exists in almost all areas of industrial production and living facilities, causing huge losses and harm to society, and may even cause serious production safety accidents. Adding corrosion inhibitors has the advantages of strong operability, high economic benefits, quick results, and overall protection, and has become one of the effective means to prevent corrosion of metal equipment.

[0003] Imidazoline corrosion inhibitors and their derivatives have the advantages of being green, non-toxic, and having good corrosion inhibition effects, and are widely used. Long-chain fatty acid imidazolines have poor water solubility and are difficult to disperse when used in an aqueous system, resulting in very poor corrosion inhibition effects. For this reason, long-chain fatty acid imidazolines generally need to be quaternized with benzyl chloride to prepare quaternized imidazolines. For example, patent CN105085402A uses rosin acid, diethylenetriamine, and benzyl chloride as raw materials to synthesize imidazoline quaternary ammonium salt corrosion inhibitors; patent CN104829539A uses adipic acid, polyamines, thiourea, and benzyl chloride as raw materials to synthesize diimidazoline quaternary ammonium salts. Quaternized imidazolines are surface active and have improved dispersion effects. However, since most quaternization agents are carcinogens and contain Cl - , which can also cause metal corrosion. For this reason, industry personnel have been committed to developing water-soluble, environmentally friendly imidazoline corrosion inhibitors that can replace imidazoline quaternary ammonium salts. For example, patent CN101705112A uses long-chain fatty acids, polyamines, and glacial acetic acid as raw materials, and adopts a "one-pot method". First, the primary amine and secondary amine (except one secondary amine group) of the polyamine are acylated on nitrogen to generate polyamides, and then the long-chain fatty acid end is dehydrated to generate an imidazoline ring to generate an imidazoline corrosion inhibitor containing one or more acetyl groups. In the first step of the synthesis, it is difficult to ensure that the long-chain fatty acid is connected to one end of the polyamine, and when the other amine groups are amidated, the amine groups adjacent to the end are retained without acylation. Due to the high activity of acetic acid, it reacts preferentially and the probability of generating the target intermediate is very small. Due to the large steric hindrance of the polyamine end, the ring-forming reaction requires a temperature of up to 240°C. Moreover, the corrosion inhibitor only uses amide as a hydrophilic group, and its hydrophilicity is low. In actual use, a surfactant still needs to be added as an auxiliary agent. Patent CN104370819A reports that firstly a monoamide is synthesized from long-chain fatty acids and polyamines, and then two molecules of amide are linked together with long-chain dibasic acids, and high-temperature dehydration is performed to generate an intermediate containing four imidazoline rings, and then all secondary amines are N-alkylated with acrylic acid to generate a macromolecular corrosion inhibitor containing multiple imidazoline rings and multiple carboxyl groups. The intermediate of this method has a large molecular weight, a large steric hindrance to the ring-forming reaction, and a temperature of 275°C. It is difficult to ensure the generation of four imidazoline rings, which is not conducive to industrial production. At the same time, the molecular weight is large, the viscosity is high, and it is difficult to operate.

[0004] Therefore, it is a problem that the industry needs to solve to overcome the shortcomings of existing imidazoline corrosion inhibitors, such as poor dispersibility in water, or containing halide ions and being difficult to prepare, and to develop non-quaternary ammonium salt-type imidazoline corrosion inhibitors with excellent corrosion inhibition performance and good dispersibility in an aqueous environment. Summary of the invention

[0005] The purpose of the present invention is to provide an imidazoline corrosion inhibitor containing a non-quaternary ammonium salt type hydrophilic group, a preparation method thereof and an application thereof. The imidazoline corrosion inhibitor has the following structure:

[0006]

[0007] Wherein, R is a straight chain or branched hydrocarbon group with 10 to 20 carbon atoms, and X is Na + , K + or NH4 + .

[0008] The halogen-free water-soluble long-chain imidazoline corrosion inhibitor of the present invention is a non-quaternary ammonium salt type corrosion inhibitor, which can be used in the treatment process of acidic oilfield sewage and industrial wastewater. The corrosion inhibitor is characterized by good dispersibility in water. After being adsorbed on the metal, the carboxylate is converted into a carboxyl group in an acidic environment, so that the hydrophilicity of the corrosion inhibitor film is weakened, and it is not easy to fall off in an aqueous corrosive medium, thereby achieving a long-term corrosion inhibition effect.

[0009] The present invention also provides a method for preparing a halogen-free water-soluble long-chain imidazoline corrosion inhibitor containing a carboxylate structure, which specifically comprises the following steps:

[0010] (1) Anhydrous citric acid reacts with acetic anhydride to obtain citric anhydride;

[0011] (2) A long-chain organic acid reacts with diethylenetriamine through amidation and cyclization to generate a long-chain imidazoline;

[0012] (3) Amidation reaction of long-chain imidazoline with citric anhydride to obtain citric acid monoamide long-chain imidazoline;

[0013] (4) neutralizing the carboxyl group of the product of step (3) into a carboxylate to obtain a halogen-free, water-soluble, long-chain imidazoline corrosion inhibitor containing a carboxylate structure.

[0014] Wherein, in step (1), the molar ratio of acetic anhydride to anhydrous citric acid is 2-1; the reaction solvent can be one or a mixture of acetic acid, propionic acid, butyric acid; and the reaction temperature is 30-50°C.

[0015] The long-chain organic acids in step (2) include: lauric acid, myristic acid, oleic acid, linoleic acid, stearic acid, ricinoleic acid, tall oil acid, and eicosanoic acid;

[0016] The molar ratio of diethylenetriamine to long-chain organic acid is 1.5 to 1; a water-carrying agent may be added to promote the reaction, and the water-carrying agent may be one or a mixture of benzene, toluene, and xylene;

[0017] The reaction temperature is 120-230°C, and the reaction time is 6-12h.

[0018] In step (3), the molar ratio of citric anhydride to long-chain imidazoline is 1.2 to 1;

[0019] A solvent may be added to improve fluidity, and the solvent may be one or a mixture of DMF, THF, acetone;

[0020] The reaction temperature is 60-100°C and the reaction time is 1-3h.

[0021] The reagent used for neutralization and pH adjustment in step (4) includes sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide or ammonia water, and the pH adjustment range is 6 to 9.

[0022] In the above preparation steps, the preferred molar ratio of acetic anhydride to anhydrous citric acid in step (1) is 1.2:1, and the solvent is preferably acetic acid.

[0023] The preferred molar ratio of diethylenetriamine to organic acid in step (2) is 1.2:1.

[0024] The preferred reaction temperature in step (2) is 140-210° C., and the reaction time is 8-10 h.

[0025] The preferred solvent in step (3) is THF.

[0026] The preferred reaction temperature in step (3) is 70-90°C.

[0027] Beneficial effects: The present invention provides a type of halogen-free water-soluble long-chain imidazoline corrosion inhibitor containing a carboxylate structure, and a preparation method and application thereof. The corrosion inhibitor is characterized by good dispersibility in water. After being adsorbed on the metal, the carboxylate is converted into a carboxyl group in an acidic environment, the hydrophilicity of the corrosion inhibitor film is weakened, and it is not easy to fall off in an aqueous corrosive medium. The corrosion inhibition effect is good, and it can be used in the treatment of acidic oilfield sewage and industrial wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the infrared spectrum of citric anhydride.

[0029] Figure 2 This is the infrared spectrum of oleic acid imidazoline.

[0030] Figure 3 This is the infrared spectrum of the halogen-free water-soluble long-chain imidazoline ① obtained in Example 1. DETAILED DESCRIPTION

[0031] The following specific embodiments are used to illustrate the present application and provide a further understanding, but the embodiments are given only as examples and are not considered to be the entire technical solution of the present invention, nor are they intended to limit the overall technical solution of the present invention. Any simple change or replacement of the same or similar technical features shall fall within the scope of protection of the present invention.

[0032] Example 1

[0033] Add anhydrous citric acid (0.125 mol, 24.04 g), acetic anhydride (0.15 mol, 9.01 g) and 30 mL of acetic acid to a 250 mL four-necked flask equipped with a thermometer and mechanical stirring, control the temperature to 35°C, and stir until the citric acid is completely dissolved into a transparent solution. Add 100 mL of dichloroethane and continue stirring until white crystals precipitate. After standing for 6 hours, filter with suction. After washing and filtering the crystals with dichloroethane 3 times, dry them under vacuum conditions for 12 hours to obtain white powdery citric anhydride (infrared spectrum as shown in the attached figure). Figure 1 The yield was 97.23%.

[0034] Attached Figure 1 Medium 3433cm -1 is the absorption peak of the hydroxyl group in citric anhydride, 1867cm -1 and 1789cm -1 The absorption peak is caused by the vibration coupling of two carbonyl groups connected to the same carbon atom in the anhydride structure, and the wave number difference between the high-frequency absorption peak and the low-frequency wave number peak is 78 cm -1 , more than 60cm -1 , indicating that it is a five-membered cyclic anhydride, confirming the synthesis of citric anhydride product.

[0035] Add oleic acid (0.03 mol, 7.25 g), diethylenetriamine (0.036 mol, 3.71 g) and xylene (50 mL) to a 250 mL four-necked flask equipped with a mechanical stirrer, insert a thermometer and a reflux condenser, and pass nitrogen protection. Turn on the stirring, heat to 140 ° C, react for 2 hours, and then add a water separator to react and dehydrate for 1 hour, remove 38 mL of xylene, and leave a small amount of xylene. Heat to 190 ° C and cyclize for 6 hours. After desolvation, oleic acid imidazoline (infrared spectrum as shown in the attached Figure 2 The yield was 98.17%.

[0036] Attached Figure 2 Medium 3300cm -1 The stretching vibration peak of -NH- bond is at 1641cm -1 The peak at 721cm is the stretching vibration peak of -C=N- bond, proving the synthesis of imidazoline ring; -1 It is the carbon-hydrogen vibration absorption peak of four or more consecutive methylene groups.

[0037] Dissolve the prepared oleic acid imidazoline in THF (30 mL). Add the prepared citric anhydride (0.03 mol, 5.28 g) and THF (50 mL) in a 250 mL four-necked flask equipped with a thermometer and mechanical stirring, stir evenly, insert a condenser and pass nitrogen protection, heat to 80 ° C, add the prepared oleic acid imidazoline solution dropwise, react for 1 hour, and remove the solvent to obtain citric acid monoamide oleic acid imidazoline.

[0038] The above product was then neutralized with sodium carbonate solution to a pH of 9 to obtain a halogen-free, water-soluble, long-chain imidazoline containing a carboxylate structure (infrared spectrum as shown in the attached figure). Figure 3 shown).

[0039] Attached Figure 3 Middle 3423cm -1 The absorption vibration peak of hydroxyl group is at 2925cm -1 and 2854cm -1 It is the carbon-hydrogen absorption peak of methyl and methylene; 1712cm -1 The absorption peak of -C=O- in carboxyl group is at 1608cm -1 The characteristic peak of imidazoline ring -C=N- is at 1463cm -1 The stretching vibration absorption peak of the carbonyl group of amide is at 721cm -1 There are four consecutive carbon-hydrogen vibration absorption peaks of methylene.

[0040] Example 2

[0041] Add anhydrous citric acid (0.125 mol, 24.04 g), acetic anhydride (0.15 mol, 9.01 g) and 30 mL of acetic acid to a 250 mL four-necked flask equipped with a thermometer and mechanical stirring; control the temperature to 35°C and stir until the citric acid is completely dissolved into a transparent solution. Add 100 mL of dichloroethane and continue stirring until white crystals precipitate. Let it stand for 6 hours and then filter. Wash and filter the crystals with dichloroethane 3 times and dry them under vacuum for 12 hours to obtain white powdery citric anhydride with a yield of 94.39%.

[0042] Stearic acid (0.03 mol, 8.53 g), diethylenetriamine (0.036 mol, 3.71 g) and xylene (50 mL) were added to a 250 mL four-necked flask equipped with a mechanical stirrer, and a thermometer and a reflux condenser were inserted, and nitrogen was passed through for protection. Stirring was started, and the mixture was heated to 140°C and reacted for 2 h. After adding a water separator to react and dehydrate for 1 h, 38 mL of xylene was removed, and a small amount of xylene was left. The mixture was heated to 190°C and the cyclization reaction was carried out for 6 h. After removing the solvent, stearic acid imidazoline was obtained with a yield of 97.56%.

[0043] Dissolve the above-prepared stearic acid imidazoline in THF (30 mL). Add the above-prepared citric anhydride (0.03 mol, 5.28 g) and THF (20 mL) into a 250 mL four-necked flask equipped with a thermometer and mechanical stirring, stir evenly, insert a condenser and pass nitrogen protection, heat to 80°C, dropwise add the above-prepared stearic acid imidazoline solution, react for 1 hour, and remove the solvent to obtain citric acid monoamide stearic acid imidazoline.

[0044] The above product is then neutralized with sodium carbonate solution to a pH of 9 to obtain a halogen-free, water-soluble, long-chain imidazoline containing a carboxylate structure②.

[0045] Example 3

[0046] Add anhydrous citric acid (0.10 mol, 19.20 g), acetic anhydride (0.15 mol, 9.01 g) and 30 mL of acetic acid to a 250 mL four-necked flask equipped with a thermometer and mechanical stirring, control the temperature to 40 ° C, and stir until the citric acid is completely dissolved into a transparent solution. Add 100 mL of dichloroethane and continue stirring until white crystals precipitate. After standing for 6 hours, filter. Wash and filter the crystals with dichloroethane 3 times and dry them under vacuum for 12 hours to obtain white powdery citric anhydride with a yield of 98.49%.

[0047] Add lauric acid (0.03 mol, 6.01 g), diethylenetriamine (0.036 mol, 3.71 g) and xylene (50 mL) to a 250 mL four-necked flask equipped with a mechanical stirrer, insert a thermometer and a reflux condenser, and pass nitrogen protection. Turn on the stirring, heat to 140 ° C, react for 2 hours, add a water separator to react and dehydrate for 1, remove 38 mL of xylene, and leave a small amount of xylene; heat to 190 ° C, and cyclize for 6 hours. After removing the solvent, lauric acid imidazoline is obtained with a yield of 96.24%.

[0048] Dissolve the lauric acid imidazoline prepared above in THF (30 mL). Add the citric anhydride prepared above (0.03 mol, 5.28 g) and THF (50 mL) to a 250 mL four-necked flask equipped with a thermometer and mechanical stirring, stir evenly, insert a condenser and pass nitrogen protection, heat to 80°C, dropwise add the lauric acid imidazoline solution prepared above, react for 1 hour, and remove the solvent to obtain citric acid monoamide lauric acid imidazoline.

[0049] The above product is then neutralized with sodium carbonate solution to a pH of 8 to obtain a halogen-free water-soluble long-chain imidazoline containing a carboxylate structure.

[0050] Example 4

[0051] Add anhydrous citric acid (0.12 mol, 21.35 g), acetic anhydride (0.15 mol, 9.01 g) and 30 mL of acetic acid to a 250 mL four-necked flask equipped with a thermometer and mechanical stirring, control the temperature to 40 ° C, and stir until the citric acid is completely dissolved into a transparent solution. Add 100 mL of dichloroethane and continue stirring until white crystals precipitate. After standing for 6 hours, filter. Wash and filter the crystals with dichloroethane 3 times and dry them under vacuum for 12 hours to obtain white powdery citric anhydride with a yield of 97.26%.

[0052] Add oleic acid (0.02 mol, 5.65 g), diethylenetriamine (0.03 mol, 3.10 g) and xylene (50 mL) to a 250 mL four-necked flask equipped with a mechanical stirrer, insert a thermometer and a reflux condenser, and pass nitrogen protection. Turn on the stirring, heat to 140 ° C, react for 2 hours, add a water separator to react and dehydrate for 1 hour, remove 38 mL of xylene, and leave a small amount of xylene; heat to 190 ° C, and cyclize for 6 hours. After removing the solvent, lauric acid imidazoline is obtained with a yield of 96.89%.

[0053] Dissolve the prepared oleic acid imidazoline in THF (30 mL). Add citric anhydride (0.024 mol, 4.24 g) and THF (50 mL) into a 250 mL four-necked flask equipped with a thermometer and mechanical stirring, stir evenly, insert a condenser and pass nitrogen protection, heat to 80°C, dropwise add the prepared lauric acid imidazoline solution, react for 1 hour, and remove the solvent to obtain citric acid monoamide lauric acid imidazoline.

[0054] The above product is then neutralized with sodium carbonate solution to a pH of 7 to obtain a halogen-free water-soluble long-chain imidazoline containing a carboxylate structure④.

[0055] Example 5 Effect Experiment

[0056] (1) Water solubility test

[0057] The experiment refers to the performance evaluation method of corrosion inhibitors for oilfield produced water in SY / T 5273-2000, and compares the halogen-free water-soluble long-chain imidazoline prepared in Examples 1, 2, 3, and 4 with unmodified oleic acid imidazoline, stearic acid imidazoline, lauric acid imidazoline and quaternized modified commercial oleic acid imidazoline quaternary ammonium salt, commercial stearic acid imidazoline quaternary ammonium salt, and commercial lauric acid imidazoline quaternary ammonium salt. The synthetic products of equal mass are weighed to observe the dissolution and dispersion of the corrosion inhibitor in water. The solubility properties of the corrosion inhibitor in water and the HLB value are shown in Table 1:

[0058] Table 1

[0059]

[0060] It can be seen from the test results in Table 1 above that this type of halogen-free long-chain imidazoline has good water solubility and dispersibility.

[0061] (2) Corrosion inhibition performance test

[0062] The experiment refers to SY / T 5273-2000 Performance Evaluation Method of Corrosion Inhibitor for Oilfield Produced Water, and the corrosion inhibition rate is tested using the rotating hanging piece weight loss method.

[0063] The 1mol / L H2SO4 solution is used as the acid corrosion system, and the corrosion inhibitor product is added directly. The specification is 5.0×2.5×0.2cm 3 of 20 # Steel sheet was used as corrosion test material, the test temperature was 30℃, the rotation speed was 100r / min, the corrosion time was 24h, and the corrosion inhibitor with the addition amount of 0.1g / L and 0.2g / L was tested. # Corrosion inhibition rate of carbon steel.

[0064] According to the formula The corrosion inhibition rate was calculated, where △m0 is the mass loss of the blank test steel sheet; △m1 is the mass loss of the test steel sheet after adding the corrosion inhibitor. The experimental results are shown in Table 2:

[0065] Table 2

[0066]

[0067]

[0068]

[0069] The experimental results show that the halogen-free water-soluble long-chain imidazoline corrosion inhibitor containing a carboxylate structure prepared by the present invention exhibits good corrosion inhibition performance and has broad application prospects in the treatment of acidic oilfield sewage and industrial wastewater.

Claims

1. A halogen-free water-soluble long-chain imidazoline corrosion inhibitor containing a carboxylate structure, characterized in that: The corrosion inhibitor has the following general formula: R is a hydrocarbon group of 10 to 20 carbon atoms, derived from the group remaining after removing the carboxyl group from one of lauric acid, myristic acid, oleic acid, linoleic acid, stearic acid, tall oil acid, and eicosanoic acid, and X is Na + , K + or NH4 + .

2. A method for preparing the halogen-free water-soluble long-chain imidazoline corrosion inhibitor containing a carboxylate structure according to claim 1, characterized in that: The preparation method steps are as follows: (1) Anhydrous citric acid reacts with acetic anhydride to obtain citric anhydride; (2) A long-chain organic acid reacts with diethylenetriamine through amidation and cyclization to generate a long-chain imidazoline; (3) Amidation reaction of long-chain imidazoline with citric anhydride to obtain citric acid monoamide long-chain imidazoline; (4) neutralizing the carboxyl group of the product of step (3) into a carboxylate to obtain a halogen-free, water-soluble, long-chain imidazoline corrosion inhibitor containing a carboxylate structure.

3. The method for preparing the halogen-free water-soluble long-chain imidazoline corrosion inhibitor containing a carboxylate structure according to claim 2, characterized in that: Step (1) The molar ratio of acetic anhydride to anhydrous citric acid is 2-1; and the reaction temperature is 30-50°C.

4. The method for preparing the halogen-free water-soluble long-chain imidazoline corrosion inhibitor containing a carboxylate structure according to claim 2, characterized in that: The long-chain organic acid in step (2) is one of lauric acid, myristic acid, oleic acid, linoleic acid, stearic acid, tall oil acid and eicosanoic acid.

5. The method for preparing the halogen-free water-soluble long-chain imidazoline corrosion inhibitor containing a carboxylate structure according to claim 2, characterized in that: In step (2), the molar ratio of diethylenetriamine to long-chain organic acid is 1.5-1, the reaction temperature is 120-230° C., and the reaction time is 6-12 h.

6. The method for preparing the halogen-free water-soluble long-chain imidazoline corrosion inhibitor containing a carboxylate structure according to claim 2, characterized in that: In step (3), the molar ratio of citric anhydride to long-chain imidazoline is 1.2-1; the reaction temperature is 60-100° C., and the reaction time is 1-3 h.

7. The method for preparing the halogen-free water-soluble long-chain imidazoline corrosion inhibitor containing a carboxylate structure according to claim 2, characterized in that: The reagent used for neutralization and pH adjustment in step (4) is sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide solution or ammonia water.

8. The method for preparing the halogen-free water-soluble long-chain imidazoline corrosion inhibitor containing a carboxylate structure according to claim 7, characterized in that: The pH adjustment range in step (4) is 6 to 9.

9. The use of the halogen-free water-soluble long-chain imidazoline corrosion inhibitor containing a carboxylate structure according to claim 1, characterized in that: The corrosion inhibitor is used for treating acidic oilfield sewage and industrial wastewater.

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