A high-temperature-resistant CO2 corrosion inhibitor, a preparation method thereof and a composite corrosion inhibitor

Abstract

The application provides a high-temperature-resistant CO2 corrosion inhibitor, a preparation method thereof and a composite corrosion inhibitor. An imidazoline ring is synthesized by combining fluorine-containing pyridine carboxylic acid and organic polyamine, and then a long-chain alkyl thiourea is used to condense and end-cap an end amine group of the imidazoline ring side chain to obtain an asymmetric end group imidazoline corrosion inhibitor. The high-temperature-resistant CO2 imidazoline corrosion inhibitor can improve the corrosion inhibition performance of the imidazoline corrosion inhibitor at high temperature by using the synergistic adsorption barrier effect of fluorine-containing pyridine and imidazoline.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas field corrosion protection, and in particular to a high-temperature resistant CO2 corrosion inhibitor and a preparation method thereof. Background Art

[0002] Carbon steel is the most widely used material in the oil and gas industry due to its low cost, high strength, and other excellent mechanical properties. However, some performance limitations remain, such as its susceptibility to corrosion when exposed to environments rich in carbon dioxide and chloride ions. Studies have shown that, at the same pH, CO2 dissolved in oilfield produced water is more corrosive to pipeline steel than hydrochloric acid. Furthermore, with increasing oilfield development depths and the increasing adoption of heavy oil thermal recovery technology, oilfield temperatures are gradually rising. Rising temperatures also exacerbate carbon steel corrosion in oilfield environments, necessitating the addition of corrosion inhibitors to slow equipment corrosion. Imidazoline corrosion inhibitors have attracted widespread attention due to their low toxicity and excellent corrosion inhibition performance. However, as oil and gas field production environments become more demanding, the corrosion inhibition performance of the long-chain alkyl imidazoline corrosion inhibitors currently widely used in the market has been significantly reduced, or even completely ineffective, in high-temperature corrosive media.

[0003] Song Shaofu et al. from Xi'an Shiyou University studied the temperature-dependent corrosion inhibition performance of oleic acid imidazoline molecules, which exhibit excellent corrosion inhibition performance within the 40°C-100°C range. The results showed that the inhibitor's performance showed a significant decline with increasing temperature. At 60°C, the inhibition efficiency reached 79.94%, but at 100°C, it dropped to 63.01%, a significant performance degradation. In the article "Evaluation of the Corrosion Inhibition Performance of Oleic Acid Imidazoline Inhibitors for 20 Steel in Topwater with Reduced Viscosity," Wei Xianda et al. from Liaoning Shiyou University of Petrochemical Technology studied the corrosion inhibition performance of imidazoline inhibitors in topwater with reduced viscosity at temperatures between 40°C and 100°C. The results showed that at 40°C, the imidazoline inhibitor effectively inhibited corrosion, achieving an inhibition efficiency of 83%. However, as the test temperature increased, the inhibitor's performance showed a significant decline, dropping to 73.2% at 100°C, indicating poor performance. A literature review revealed that temperature is the primary factor limiting the performance of imidazoline inhibitors.

[0004] Patent CN110359053A discloses a composite imidazoline quaternary ammonium salt corrosion inhibitor and its preparation method. The raw materials include oleic acid, tetraethylene pentamine, a quaternizing agent, sodium dodecylbenzene sulfonate, and potassium iodide. The oleic acid and tetraethylene pentamine react to produce an imidazoline intermediate, which is then reacted with the quaternizing agent to produce the imidazoline quaternary ammonium salt corrosion inhibitor. The composite imidazoline quaternary ammonium salt corrosion inhibitor is prepared by compounding the imidazoline quaternary ammonium salt corrosion inhibitor with sodium dodecylbenzene sulfonate and potassium iodide. This composite imidazoline quaternary ammonium salt corrosion inhibitor was tested in an acidic medium using the coupon weight loss method. The corrosion inhibition rate at 60°C was 85% to 91%, but no data was available for testing at higher temperatures.

[0005] Patent CN104513205B discloses an imidazoline high-temperature corrosion inhibitor and a preparation method thereof, wherein the preparation method comprises: (1) uniformly mixing an organic acid, diethylenetriamine, and xylene at 70-90°C, heating to 150-170°C, reacting for 1.5-2.5h, further heating to 175-185°C, reacting for 1.5-2.5h, and then heating to 180-210°C and reacting for 1.5-2.5h. When no water droplets appear in the condenser, cooling the reaction system to 100-120°C, distilling off xylene and diethylenetriamine, and cooling to 35-45°C at room temperature to obtain an imidazoline intermediate; (2) adding triethylamine, mixing uniformly, and then dropwise adding fluorinated alkylsulfonyl fluoride, heating to 50-55°C, and reacting for 22-26h to obtain an imidazoline high-temperature corrosion inhibitor. According to tests, the slow-release efficiency of the prepared oleic acid imidazoline corrosion inhibitor at a test temperature of 120° C. is no more than 81%.

[0006] As can be seen from the above prior art, existing imidazoline corrosion inhibitors, due to limitations in their molecular structure, cannot maintain stable corrosion inhibition efficiency at different temperatures, and their slow-release efficiency is low at high temperatures. Therefore, developing an imidazoline corrosion inhibitor that can operate in high-temperature oilfield environments and has high corrosion inhibition efficiency is an urgent problem to be solved. Summary of the Invention

[0007] In response to the limitations of existing technologies, the present invention provides a high-temperature CO2-resistant imidazoline corrosion inhibitor. This inhibitor is synthesized by combining fluorinated pyridinecarboxylic acid with an organic polyamine to form an imidazoline ring, which is then capped by condensing a long-chain alkylthiourea with the terminal amine groups of the imidazoline ring side chains. This inhibitor, with asymmetric end groups, utilizes the synergistic adsorption and barrier effects of fluorinated pyridine and imidazoline to improve the corrosion inhibition performance of the imidazoline inhibitor at high temperatures.

[0008] The technical solutions of the present invention are as follows:

[0009] The present invention provides a high-temperature resistant CO2 imidazoline corrosion inhibitor having the following molecular structure (shown in Formula 1):

[0010]

[0011] Wherein, m is an integer not less than 0, and n=0 or 2.

[0012] Furthermore, in Formula I, the value of m is any one of 1, 11, and 17.

[0013] The present invention has shown through theoretical and experimental studies that the molecular design of Formula I can improve the corrosion inhibition performance of the imidazoline corrosion inhibitor at high temperatures by utilizing the synergistic adsorption and barrier effect of fluorine-containing pyridine and imidazoline.

[0014] Furthermore, the release efficiency of the high temperature resistant CO2 imidazoline corrosion inhibitor at 120°C is above 80%, preferably above 85%.

[0015] The present invention also provides a method for preparing the high-temperature resistant CO2 imidazoline corrosion inhibitor, which comprises the following steps:

[0016] S1: reacting fluorinated pyridine carboxylic acid with organic polyamine to obtain an imidazoline intermediate;

[0017] S2: reacting the imidazoline intermediate with a long-chain alkylthiourea to obtain an imidazoline corrosion inhibitor with an asymmetric terminal group.

[0018] Furthermore, the method comprises the following steps:

[0019] S1: A fluorinated pyridine carboxylic acid is subjected to an amidation reaction with an organic polyamine at a temperature of 120-140° C., and then the temperature is raised to 180-200° C. for a dehydration cyclization reaction for 2-4 hours to obtain an imidazoline intermediate;

[0020] S2: After cooling the reaction system to 100-140° C., long-chain alkylthiourea is added and the reaction is continued for 1-3 hours to obtain an imidazoline corrosion inhibitor having an asymmetric terminal group.

[0021] Furthermore, the molar ratio of the fluorine-containing pyridine carboxylic acid to the organic polyamine is 1:1.05. If the organic amine is excessive (less than 1:1.05), the yield of the imidazoline intermediate increases, but if the organic amine is too excessive, the amidation reaction is insufficient, resulting in the formation of an intermediate byproduct amide.

[0022] Furthermore, the molar ratio of the imidazoline intermediate to the long-chain alkylthiourea is 1:1.1.

[0023] Furthermore, the organic polyamine is tetraethylenepentamine or diethylenetriamine, preferably tetraethylenepentamine.

[0024] Furthermore, the long-chain alkyl carboxylic acid is one or more of ethylthiourea, dodecylthiourea, and stearylthiourea. Preferably, the long-chain alkyl carboxylic acid is stearylthiourea.

[0025] The present invention also provides a composite corrosion inhibitor, which is obtained by compounding the imidazoline corrosion inhibitor with one or more of mercapto alcohol, unsaturated alcohol, and halogen compounds, and can further improve the high temperature resistance of the thiourea-based imidazoline corrosion inhibitor.

[0026] Furthermore, the mercapto alcohol is mercaptoethanol; the unsaturated alcohol is propynol; and the halogen compound is iodide.

[0027] Furthermore, when compounded, the amount of the imidazoline corrosion inhibitor is 10-30%; the amount of the mercapto alcohol is 0-8%, the amount of the unsaturated alcohol is 0-5%, and the amount of the halogen compound is 0-5%, based on the total mass of the composite corrosion inhibitor.

[0028] The high-temperature resistant CO2 corrosion inhibitor and the composite corrosion inhibitor containing the same of the present invention can be used as oil field corrosion inhibitors or protective agents for metal equipment in pickling environments. At a service temperature of 120-150°C, the corrosion inhibition efficiency reaches more than 92%, and has very excellent high-temperature corrosion inhibition performance.

[0029] The beneficial results of the present invention are:

[0030] (1) The present invention provides a novel imidazoline corrosion inhibitor resistant to high-temperature CO2 corrosion media. By utilizing synergistic adsorption, an imidazoline ring is first synthesized from fluorine-containing pyridine carboxylic acid and an organic polyamine, and then a long-chain alkylthiourea is condensed and capped with the amino group of the imidazoline ring side chain to obtain an imidazoline corrosion inhibitor with excellent performance in high-temperature CO2 corrosion media, and has very strong corrosion inhibition performance at high temperatures.

[0031] (2) The synthesis process is simple and the corrosion inhibition effect is good. It is suitable for corrosion protection of N80 low carbon steel. It still maintains excellent corrosion inhibition performance under high temperature conditions of 120°C and can effectively prevent the corrosion of carbon steel in high temperature CO2 environment. The corrosion inhibition efficiency is above 80%.

[0032] (3) The high temperature resistant CO2 corrosion inhibitor group is used as the main corrosion inhibitor and compounded with the synergist to further improve the corrosion inhibition performance of the corrosion inhibitor in a high temperature environment. The corrosion inhibition efficiency can basically be maintained at more than 90% at a high temperature of 120-150°C. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] Example 1

[0035] A high-temperature resistant CO2 imidazoline corrosion inhibitor, wherein m=11 in the molecular structure of Formula I, is prepared as follows:

[0036] S1: Solid 3-fluoropyridine-2-carboxylic acid, diethylenetriamine, and an appropriate amount of xylene water-carrying agent were added to a three-necked flask. Several grains of zeolite were added and amidation was carried out at 120°C for 4 hours. The temperature was then further increased to 220°C for dehydration and cyclization for 2 hours to obtain an imidazoline intermediate, wherein the molar ratio of 3-fluoropyridine-2-carboxylic acid to diethylenetriamine was 1:1.05;

[0037] S2: After cooling the reaction system to 100° C., dodecylthiourea in an amount equal to the molar ratio of 3-fluoropyridine-2-carboxylic acid was added and the reaction was continued for 2 hours. After the reaction was completed, water and xylene were removed by rotary evaporation to obtain an imidazoline corrosion inhibitor with an asymmetric terminal group.

[0038] Example 2

[0039] A high-temperature resistant CO2 imidazoline corrosion inhibitor, wherein m=1 in the molecular structure of Formula I, is prepared as follows:

[0040] S1: Solid 3-fluoropyridine-2-carboxylic acid, tetraethylenepentamine, and an appropriate amount of xylene water-carrying agent were added to a three-necked flask. Several grains of zeolite were added and amidation was carried out at 120°C for 4 hours. The temperature was then further increased to 220°C for dehydration and cyclization for 2 hours to obtain an imidazoline intermediate, wherein the molar ratio of 3-fluoropyridine-2-carboxylic acid to tetraethylenepentamine was 1:1.05;

[0041] S2: After cooling the reaction system to 100° C., ethylthiourea in an amount equal to the molar ratio of 3-fluoropyridine-2-carboxylic acid was added and the reaction was continued for 2 hours. After the reaction was completed, water and xylene were removed by rotary evaporation to obtain an imidazoline corrosion inhibitor with an asymmetric terminal group.

[0042] Example 3

[0043] A high-temperature resistant CO2 imidazoline corrosion inhibitor, wherein m=11 in the molecular structure of Formula I, is prepared as follows:

[0044] S1: Solid 3-fluoropyridine-2-carboxylic acid, tetraethylenepentamine, and an appropriate amount of xylene water-carrying agent were added to a three-necked flask. Several grains of zeolite were added and amidation was carried out at 120°C for 4 hours. The temperature was then further increased to 220°C for dehydration and cyclization for 2 hours to obtain an imidazoline intermediate, wherein the molar ratio of 3-fluoropyridine-2-carboxylic acid to tetraethylenepentamine was 1:1.05;

[0045] S2: After cooling the reaction system to 100° C., dodecylthiourea in an amount equal to the molar ratio of 3-fluoropyridine-2-carboxylic acid was added and the reaction was continued for 2 hours. After the reaction was completed, water and xylene were removed by rotary evaporation to obtain an imidazoline corrosion inhibitor with an asymmetric terminal group.

[0046] Example 4

[0047] A high-temperature resistant CO2 imidazoline corrosion inhibitor, wherein m=17 in the molecular structure of Formula I, is prepared as follows:

[0048] S1: Solid 3-fluoropyridine-2-carboxylic acid, tetraethylenepentamine, and an appropriate amount of xylene water-carrying agent were added to a three-necked flask. Several grains of zeolite were added and amidation was carried out at 140°C for 4 hours. The temperature was then further increased to 220°C for dehydration and cyclization for 2 hours to obtain an imidazoline intermediate, wherein the molar ratio of 3-fluoropyridine-2-carboxylic acid to tetraethylenepentamine was 1:1.05;

[0049] S2: After cooling the reaction system to 100° C., stearyl thiourea in an amount equal to the molar ratio of 3-fluoropyridine-2-carboxylic acid is added and the reaction is continued for 2 hours. After the reaction is completed, water and xylene are removed by rotary evaporation to obtain an imidazoline corrosion inhibitor with an asymmetric terminal group.

[0050] Example 5

[0051] Mercaptoethanol was added to the high-temperature resistant CO2 imidazoline corrosion inhibitor synthesized in Example 4 to prepare a composite corrosion inhibitor, wherein the mass ratio of mercaptoethanol to imidazoline was 1:4.

[0052] Example 6

[0053] Propynol was added to the high-temperature resistant CO2 imidazoline corrosion inhibitor synthesized in Example 4 to prepare a composite corrosion inhibitor, wherein the mass ratio of propynol to imidazoline was 1:4.

[0054] Example 7

[0055] Potassium iodide was added to the high-temperature resistant CO2 imidazoline corrosion inhibitor synthesized in Example 4 to prepare a composite corrosion inhibitor, wherein the mass ratio of potassium iodide to imidazoline was 1:4.

[0056] Example 8

[0057] Mercaptoethanol, potassium iodide and propargyl alcohol were added to the high-temperature resistant CO2 imidazoline corrosion inhibitor synthesized in Example 4 to prepare a composite corrosion inhibitor, wherein the mass ratio of mercaptoethanol, potassium iodide, propargyl alcohol and imidazoline was 1:1:1:4.

[0058] Test Case

[0059] The performance of corrosion inhibitor molecules was evaluated using the weight loss method.

[0060] Experimental apparatus: Autoclave

[0061] Experimental temperature: 120℃, 150℃

[0062] Experimental time: 24 hours

[0063] Corrosion material: N80 steel

[0064] Corrosive medium: 1MPa CO2 is introduced into 3% NaCl solution, and a mixed system of different corrosion inhibitors with a concentration of 200mg / L is added.

[0065] The commercially available diethylenetriamine imidazoline oleate was used as a comparative example.

[0066] The specific steps of the weight loss method are as follows:

[0067] The interior of the autoclave was cleaned, and the appropriate amount of corrosion inhibitor was added to a prepared 3% NaCl solution. The washed N80 steel metal coupons were then suspended and immersed in the corrosion solution. CO₂ gas was then passed through the autoclave for half an hour to remove oxygen. The autoclave was then heated to the desired experimental temperature and 1 MPa CO₂ gas was passed through. After 24 hours of corrosion, the coupons were removed and washed with water, alcohol, and acetone, followed by drying with cold air. The mass was weighed, and the corrosion rate and inhibition ratio were calculated. The relevant test results are shown in Table 1.

[0068] The corrosion rate is calculated as follows: Where Δm is the mass loss before and after corrosion, unit is g, S is the area of ​​the coupon, unit is cm 2 , t is the experimental time, in h.

[0069] The corrosion inhibition efficiency calculation formula is as follows: η=(V0-V inh ) / V0, where V0 is the corrosion rate of the blank without adding corrosion inhibitor, V inh It is the corrosion rate after adding corrosion inhibitor, in millimeters per year (mm / a).

[0070] Table 1 Weightlessness test results

[0071]

[0072] As can be seen from Table 1, the high-temperature resistant CO2 imidazoline corrosion inhibitors synthesized in Examples 1-4 of the present invention have slightly different corrosion inhibition efficiencies under 120°C and 1MPaCO2 experimental conditions, but the overall corrosion inhibition efficiency remains at a high level, and are corrosion inhibitors with excellent performance, proving that the high-temperature resistant CO2 imidazoline corrosion inhibitor of the present invention still has good corrosion inhibition performance under high temperature and harsh conditions when used alone.

[0073] Further analysis of Examples 5-7 shows that the performance of the synergist is significantly improved after compounding with the high temperature resistant CO2 imidazoline corrosion inhibitor as the main corrosion inhibitor, wherein the synergistic effect between the synergist and the main agent is in the order of propargyl alcohol>mercaptoethanol>I - , and from Example 8, it can be seen that the composite corrosion inhibitor obtained by compounding the three synergists (mercaptoethanol, potassium iodide, and propynyl alcohol) with the main corrosion inhibitor has the best performance.

[0074] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent variation based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A high temperature resistant CO2 imidazoline corrosion inhibitor, characterized in that, The high temperature resistant CO2 imidazoline corrosion inhibitor has the following molecular structure: Formula I Wherein, m is an integer not less than 0, and n=0 or 2.

2. The high temperature resistant CO2 imidazoline corrosion inhibitor according to claim 1, characterized in that The value of m is any one of 1, 11, and 17.

3. A method for preparing a high temperature resistant CO2 imidazoline corrosion inhibitor according to claim 1 or 2, characterized in that: The method comprises the following steps: S1: A fluorinated pyridine carboxylic acid is subjected to an amidation reaction with an organic polyamine at a temperature of 120-140° C., and then the temperature is raised to 180-200° C. for a dehydration cyclization reaction for 2-4 hours to obtain an imidazoline intermediate; S2: After cooling the reaction system to 100-140° C., long-chain alkylthiourea is added and the reaction is continued for 1-3 hours to obtain an imidazoline corrosion inhibitor having an asymmetric terminal group.

4. The preparation method according to claim 3, characterized in that The molar ratio of the fluorine-containing pyridine carboxylic acid to the organic polyamine is 1:1.

05.

5. The preparation method according to claim 4, characterized in that The molar ratio of the imidazoline intermediate to the long-chain alkylthiourea is 1:1.

1.

6. The preparation method according to claim 5, characterized in that The organic polyamine is tetraethylenepentamine or diethylenetriamine.

7. The preparation method according to claim 6, characterized in that The long-chain alkylthiourea is one or more of ethylthiourea, dodecylthiourea and stearyl alkylthiourea.

8. A composite corrosion inhibitor, characterized in that: The corrosion inhibitor is obtained by compounding the imidazoline corrosion inhibitor according to any one of claims 1 to 7 with one or more of mercapto alcohol, unsaturated alcohol and halogen compound.

9. The composite corrosion inhibitor according to claim 8, characterized in that The mercapto alcohol is mercaptoethanol, the unsaturated alcohol is propynol, and the halogen compound is iodide.

10. The composite corrosion inhibitor according to claim 9, characterized in that When compounded, the amount of the imidazoline corrosion inhibitor is 10-30%; the amount of the mercapto alcohol is 0-8%, the amount of the unsaturated alcohol is 0-5%, and the amount of the halogen compound is 0-5%, based on the total mass of the composite corrosion inhibitor.

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