Corrosion inhibitor under oxygen-carbon dioxide coexistence resisting condition as well as preparation method and application of corrosion inhibitor

Abstract

The invention discloses a corrosion inhibitor under an oxygen-carbon dioxide coexistence resistant condition as well as a preparation method and application thereof, and belongs to the field of corrosion prevention of oil and gas fields. The corrosion inhibitor at least comprises 20-40 parts of a corrosion inhibitor main agent, 3-7 parts of a synergist, 0.8-1.2 parts of a surfactant, 45-55 parts of a solvent, 10-18 parts of amino acid and 4-8 parts of a deoxidant. The corrosion inhibitor main agent is prepared from 15 to 25 parts of dihexyl hydrogen phosphate and 5 to 15 parts of oleic acid imidazoline; the synergist is prepared from 3 to 7 parts of organic alkynol; the corrosion inhibitor under the oxygen-carbon dioxide coexistence resisting condition has efficient corrosion inhibition performance in the oxygen and carbon dioxide coexistence environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil and gas field corrosion prevention, in particular, the present application relates to a kind of corrosion inhibitor under oxygen-carbon dioxide coexisting condition and its preparation method and application. BACKGROUND

[0002] With the popularization and application of carbon dioxide gas flooding stimulation measures in oil field, and the inevitable oxygen-rich environment in surface gathering process, high concentration of carbon dioxide and oxygen are dissolved in produced water system at the same time, forming a complex environment of "oxygen-carbon dioxide gas synergistic corrosion"; carbon dioxide dissolves in water to form carbonic acid, making the water body acidic, providing a continuous medium condition for the electrochemical corrosion of metal surface; and oxygen as a strong cathode depolarizer will further accelerate the cathode reaction rate in acidic environment.

[0003] The current mainstream corrosion inhibitor (imidazoline, organic amine and quaternary ammonium salt compounds) mainly aims at carbon dioxide corrosion, and its protection mechanism relies on the formation of chemical / physical adsorption between the polar groups in the molecule and the metal surface to build a protective film; but in the coexisting environment of carbon dioxide and oxygen, the competitive adsorption of oxygen directly reduces the effective coverage of the corrosion inhibitor on the metal surface, and the strong oxidizing property destroys the molecular structure of the corrosion inhibitor, resulting in the discontinuity of the adsorption film; the compounded system is always difficult to break through the technical bottleneck of synergistic corrosion due to the destruction of oxygen to each component, salt ion interference and other problems, resulting in a significant decrease in corrosion inhibition rate in actual application, which is difficult to meet the on-site protection needs.

[0004] Therefore, in view of the above problems, it is urgent to develop a corrosion inhibitor under oxygen-carbon dioxide coexisting condition to solve the problem of metal corrosion in the coexisting environment of carbon dioxide and oxygen. SUMMARY

[0005] In view of the above problems, the purpose of the present application is to provide a corrosion inhibitor preparation method and application under oxygen-carbon dioxide coexisting condition.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is as follows: the preparation method of the corrosion inhibitor under oxygen-carbon dioxide coexisting condition, by weight, including 20-40 parts of corrosion inhibitor main agent, 3-7 parts of synergist, 0.8-1.2 parts of surfactant, 45-55 parts of solvent, 10-18 parts of amino acid, 4-8 parts of oxygen scavenger; the corrosion inhibitor main agent is composed of 15-25 parts of dihexyl hydrogen phosphate and 5-15 parts of imidazoline oleate.

[0007] Further, the structural formula of dihexyl hydrogen phosphate is shown as formula I: .

[0008] Further, the structural formula of imidazoline oleate is shown as formula II: .

[0009] A further improvement of the present invention is that the surfactant is one of cetyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, and sodium lauryl sulfate; and the solvent is one of isopropyl alcohol, propanol, and ethanol.

[0010] A further improvement of the present invention is that the amino acid is a mixture of L-histidine, lysine and tryptophan, and the mass ratio of the three is 1:(0.7-0.9):(0.3-0.5); the oxygen scavenger is one or more of hydrazine, dimethyl ketoxime, isoascorbic acid and sodium ascorbate; and the organic alkynol includes one or more of propynol, 1,4-butynediol and hexynol.

[0011] A further improvement of the present invention is that dihexyl hydrogen phosphate is prepared by the following process: S11 adding hexanol, toluene and phosphorous acid to an enameled reactor, evacuating to -0.09 MPa, filling with nitrogen with a purity of ≥99.99%, repeating 3 times to replace oxygen, and stirring at 40°C for 10-15 minutes; heating to 80±2°C, reflux for 1 hour to remove moisture, and obtaining a mixed solution; S12 adding polyphosphoric acid to the mixed solution, cooling to 35-40°C in an ice bath, and then adding phosphorus pentoxide in batches, keeping warm and stirring for 1 hour, then heating to 85±5°C, keeping warm and reacting for 6 hours, and cooling to 20-25°C after the reaction is completed; S13 adding 5% Na2CO3 solution (volume ratio 1:1) to the reaction solution, stirring for 30 minutes, standing and separating, taking the upper organic phase, and fractionating the organic phase under reduced pressure to obtain a light yellow liquid dihexyl hydrogen phosphate.

[0012] A further improvement of the present invention is that the molar ratio of hexanol, phosphorus pentoxide, polyphosphoric acid, phosphorous acid and toluene is 1:(0.2-0.4):(0.008-0.01):(0.01-0.015):(0.3-0.6).

[0013] A further improvement of the present invention is that the organic alkynol is one or more of propynol, 1,4-butynediol, and hexynol.

[0014] The present invention further provides a method for preparing the above-mentioned corrosion inhibitor resistant to oxygen-carbon dioxide coexistence conditions. The above-mentioned corrosion inhibitor main agent, synergist, surfactant, solvent, amino acid and scavenger are added to a reactor by weight, and the stirring temperature is 25-30°C, the stirring rate is 300r / min, and the stirring time is 30 minutes to obtain the above-mentioned corrosion inhibitor resistant to oxygen-carbon dioxide coexistence conditions.

[0015] Compared with the prior art, the application has the beneficial effects that, especially in a complex environment containing oxygen and carbon dioxide, dihexyl hydrogen phosphate exhibits excellent corrosion inhibition performance, and the core reasons are as follows: firstly, the strong polarity of the phosphorus-oxygen double bond and the lone pair of electrons of the oxygen atom can be combined with the active sites on the metal surface through coordination bonds, adsorbed on the metal surface and form an adsorption protective layer, reduce the number of active centers of the corrosion reaction, thereby inhibit the accelerating effect of oxygen as a cathode depolarizer and the electrochemical corrosion of carbon dioxide to form carbonic acid on the metal; secondly, the negative ions of the phosphate ester combine with the metal ions produced by corrosion to form an insoluble precipitate film, which forms a physical barrier to the metal substrate, hinders the penetration of oxygen, carbon dioxide and corrosive ions, plays a scale inhibition role, avoids the accumulation of corrosion products to form a local corrosion cell, and further enhances the inhibition effect on carbon dioxide corrosion; in the molecular structure of the oleic acid imidazoline of the application, the lone pair of electrons of the nitrogen atom of the imidazoline ring can form a coordination bond with the empty orbital of the metal surface atom, and the hydroxyl group can be combined with the hydroxyl group on the metal surface through hydrogen bonding, and the two kinds of synergistic strengthening of the physical and chemical adsorption of the molecule on the metal surface ensure the stability and rapidity of the adsorption; the long-chain alkyl group derived from oleic acid is closely arranged by means of intermolecular van der Waals force, which significantly improves the order and density of the adsorption film, reduces the voids of the film layer, and its hydrophobic property can effectively isolate the diffusion of corrosion media such as water, carbon dioxide and oxygen to the metal surface; the "adsorption film + precipitate film" of dihexyl hydrogen phosphate and the dense adsorption film of oleic acid imidazoline synergize to block the corrosion medium through coordination bonds, hydrogen bonds and hydrophobic long chains; the organic alkyne alcohol enhances the adsorption capacity of the main agent on the metal surface to resist the competitive adsorption of oxygen; the surfactant improves the dispersibility of the agent to ensure the uniformity of adsorption; the amino acid fills the adsorption gap by assisting film formation through N, O and other atoms; the deoxidizer reduces the oxygen content of the system and reduces the oxidative degradation of the corrosion inhibitor molecules by oxygen; the multi-component synergistic effect solves the problem of easy damage of the adsorption film of the traditional corrosion inhibitor in the coexisting environment and the decrease of the corrosion inhibition efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The synthesis path of dihexyl hydrogen phosphate of the application. DETAILED DESCRIPTION

[0017] The content of the application can be more easily understood by referring to the following detailed description of the preferred implementation method of the application and the included examples; unless otherwise defined, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the application belongs; when there is a conflict, the definition in the specification shall prevail.

[0018] The application provides an oxygen-carbon dioxide coexisting condition resistant corrosion inhibitor, which comprises at least 20-40 parts of corrosion inhibitor main agent, 3-7 parts of synergist, 0.8-1.2 parts of surfactant, 45-55 parts of solvent, 10-18 parts of amino acid and 4-8 parts of oxygen scavenger by weight.

[0019] In an embodiment, the amino acid is a mixture of L-histidine, lysine and tryptophan.

[0020] In an embodiment, the mass ratio of the L-histidine to the lysine and the tryptophan is 1:(0.7-0.9):(0.3-0.5); preferably, the mass ratio of the L-histidine, the lysine and the tryptophan is 1:0.8:0.4.

[0021] In an embodiment, the preparation raw material of the dihexyl hydrogen phosphate in the corrosion inhibitor main agent comprises hexanol, phosphorus pentoxide, polyphosphoric acid, phosphorous acid and toluene; the molar ratio of the preparation raw material of the dihexyl hydrogen phosphate in the corrosion inhibitor main agent is 1:(0.2-0.4):(0.008-0.01):(0.01-0.015):(0.3-0.6).

[0022] The preparation method of the dihexyl hydrogen phosphate comprises the following steps: S11, adding hexanol, toluene and phosphorous acid into an agate reaction kettle, vacuumizing to-0.09 MPa, filling nitrogen with purity of ≥99.99%, repeating oxygen replacement for 3 times, stirring at 40℃ for 10-15 minutes; increasing temperature to 80±2℃, refluxing for 1 hour to remove water, obtaining a mixed solution; the mass ratio of the hexanol, toluene and phosphorous acid is 1:0.4:0.01; S12, cooling the mixed solution to 35-40℃ by ice bath, slowly adding polyphosphoric acid in a thin stream, then adding phosphorus pentoxide in batches, keeping temperature at 40±1℃ and stirring for 1 hour, then increasing temperature to 85±5℃, keeping temperature and reacting for 6 hours, and cooling to 20-25℃ after the reaction is completed; the mass ratio of the polyphosphoric acid and the phosphorus pentoxide is 4:5; S13, adding 5% Na2CO3 solution (volume ratio 1:1) into the reaction solution in S12, stirring for 30 minutes, standing and separating, reducing pressure and distilling the upper organic phase to obtain dihexyl hydrogen phosphate in light yellow liquid.

[0023] In an embodiment, the raw materials for preparing the imidazoline oleate in the corrosion inhibitor main agent include oleic acid, diethylene triamine and dimethylbenzene; the molar ratio of the oleic acid, diethylene triamine and dimethylbenzene is 1: (1-1.2): (0.8-1); preferably, the molar ratio of the oleic acid, diethylene triamine and dimethylbenzene is 1:1.1:0.9.

[0024] In an embodiment, the surfactant is one of hexadecyl trimethyl ammonium bromide, sodium dodecyl benzene sulfonate and sodium dodecyl sulfate; the solvent includes one of isopropyl alcohol, propanol and ethanol; the organic acetylenic alcohol includes one or more of propargyl alcohol, 1,4-butynediol and hexynol; the oxygen scavenger is one or more of hydrazine, dimethyl ketone oxime, erythorbic acid and sodium ascorbate; preferably, the surfactant is hexadecyl trimethyl ammonium bromide; the solvent is isopropyl alcohol; the organic acetylenic alcohol is 1,4-butynediol; and the oxygen scavenger is dimethyl ketone oxime.

[0025] The method for preparing the corrosion inhibitor main agent in the present application is as follows: 15-25 parts of dihexyl hydrogen phosphate and 5-15 parts of imidazoline oleate are mixed uniformly according to weight parts.

[0026] In another aspect of the present application, a method for preparing a corrosion inhibitor resistant to oxygen and carbon dioxide coexisting conditions is provided, which comprises the following steps: adding a corrosion inhibitor main agent, a synergist, a surfactant, a solvent, an amino acid and an oxygen scavenger into a reactor according to weight parts, stirring at a temperature of 25-30°C and a stirring rate of 300 r / min for 30 minutes to obtain the corrosion inhibitor resistant to oxygen and carbon dioxide coexisting conditions, the effect of which is based on the synergistic mechanism of "adsorption film" and "precipitation film": in the molecular structure of dihexyl hydrogen phosphate, the strong polarity of phosphorus-oxygen double bond and the lone pair of electrons of oxygen atom can be combined with the active sites on the metal surface through coordination bond, adsorbed on the metal surface and formed an adsorption protective layer to reduce the number of active centers of corrosion reaction; the negative ions of phosphate ester are combined with metal ions generated by corrosion to form an insoluble precipitation film, which not only protects the metal but also plays a scale inhibition role.

[0027] In the molecular structure of the imidazoline oleate in the present application, the lone pair of electrons of the nitrogen atom in the imidazoline ring can form a coordination bond with the empty orbital of the metal surface atom, and the hydroxyl group can be combined with the hydroxyl group on the metal surface through hydrogen bond, the physical and chemical adsorption of the two synergistic molecules on the metal surface ensures the stability and rapidity of adsorption; the long-chain alkyl group derived from oleic acid is closely arranged by means of intermolecular van der Waals force, which significantly improves the order and compactness of the adsorption film, reduces the voids in the film layer, and its hydrophobic property can effectively isolate the diffusion of corrosion media such as water, carbon dioxide and oxygen to the metal surface.

[0028] Amino acids are amphoteric compounds containing both acidic carboxyl and basic amino groups, which can be prepared by protein hydrolysis and can be completely decomposed in the natural environment. The core reason why amino acid substances have corrosion inhibition effect is that the N, O, S and other atoms with strong electronegativity in the molecules can easily give electrons to form bonds with metal surface atoms, and then be adsorbed on the metal surface in a directional manner and form a protective film.

[0029] The hydrophilic group of the surfactant molecule can be preferentially adsorbed on the metal surface by electrostatic attraction, chemical adsorption or hydrogen bonding, and the hydrophobic group faces the solution to form a dense directional adsorption film, which physically isolates water, oxygen and other corrosion media to inhibit anodic and cathodic reactions; the micelles formed when reaching the critical micelle concentration can wrap the insoluble components to achieve solubilization, improve the dispersibility and stability of the corrosion inhibitor; and the micelles can also synergistically adsorb with amino acid and other components through hydrogen bonding, thicken the isolation barrier and enhance the corrosion inhibition efficiency; and the micelles can also reduce the surface tension of the solution and improve the wettability of the metal surface, so as to ensure uniform spreading of the corrosion inhibition components to avoid corrosion blind spots.

[0030] The application will be described in detail below by way of examples; it is necessary to point out here that the following examples are only used to further illustrate the application and cannot be understood as limiting the protection scope of the application, and some non-essential improvements and adjustments made by the person skilled in the art based on the content of the above application still belong to the protection scope of the application.

[0031] In addition, if not otherwise specified, the raw materials used are commercially available and purchased from National Medicine Chemical Reagents.

[0032] The corrosion inhibitor for resisting oxygen-carbon dioxide coexistence conditions comprises, by weight, at least 30 parts of a corrosion inhibitor main agent, 5 parts of a synergist, 1 part of a surfactant, 47 parts of a solvent, 11 parts of an amino acid and 6 parts of an oxygen scavenger; the corrosion inhibitor main agent is composed of 20 parts of dihexyl hydrogen phosphate and 10 parts of imidazoline oleate; the amino acid is a mixture of L-histidine, lysine and tryptophan, and the mass ratio of the L-histidine, lysine and tryptophan is 1:0.8:0.4; the preparation raw materials of the dihexyl hydrogen phosphate in the corrosion inhibitor main agent include hexanol, phosphorus pentoxide, polyphosphoric acid, phosphorous acid and toluene, and the molar ratio of the hexanol, phosphorus pentoxide, polyphosphoric acid, phosphorous acid and toluene is 1:0.25:0.01:0.01:0.5; the preparation raw materials of the imidazoline oleate in the corrosion inhibitor main agent include oleic acid, diethylene triamine and dimethylbenzene; the molar ratio of the oleic acid, diethylene triamine and dimethylbenzene is 1:1.1:0.9; the surfactant is hexadecyl trimethyl ammonium bromide; the solvent is isopropyl alcohol; the synergist is 1, 4-butynediol; and the oxygen scavenger is dimethyl ketoxime.

[0033] The preparation method of the corrosion inhibitor under the coexistence of oxygen and carbon dioxide comprises the following steps: adding, by weight, corrosion inhibitor main agent, synergist, surfactant, solvent, amino acid and oxygen scavenger into a reactor, mixing and stirring uniformly to obtain the corrosion inhibitor under the coexistence of oxygen and carbon dioxide.

[0034] The preparation method of the dihexyl hydrogen phosphate comprises the following steps: S11, adding hexanol, toluene and phosphorous acid into an enamel reaction kettle, vacuumizing to-0.09 MPa, filling nitrogen with purity of ≥99.99%, replacing oxygen for 3 times, stirring at 40℃ for 10-15 minutes; increasing temperature to 80±2℃, refluxing for 1h to remove moisture to obtain a mixed solution; the mass ratio of the hexanol, toluene and phosphorous acid is 1:0.4:0.01; S12, slowly adding polyphosphoric acid in a thin stream to the mixed solution cooled to 35-40℃ by ice bath, then adding phosphorus pentoxide in batches, keeping temperature at 40±1℃ and stirring for 1h, then increasing temperature to 85±5℃, keeping temperature and reacting for 6 hours, and cooling to 20-25℃ after the reaction is completed; the mass ratio of the polyphosphoric acid and the phosphorus pentoxide is 4:5; S13, adding 5% Na2CO3 solution (volume ratio 1:1) into the reaction solution in S12, stirring for 30 minutes, standing and separating, and reducing pressure to distill the upper organic phase to obtain dihexyl hydrogen phosphate in light yellow liquid.

[0035] In example 2, the corrosion inhibitor under the coexistence of oxygen and carbon dioxide comprises, by weight, at least 35 parts of corrosion inhibitor main agent, 6 parts of synergist, 1 part of surfactant, 44 parts of solvent, 10 parts of amino acid and 4 parts of oxygen scavenger; the corrosion inhibitor main agent is composed of 22 parts of dihexyl hydrogen phosphate and 13 parts of imidazoline oleate; the amino acid is a mixture of L-histidine, lysine and tryptophan, and the mass ratio of the L-histidine, lysine and tryptophan is 1:0.7:0.4; the preparation raw materials of the dihexyl hydrogen phosphate in the corrosion inhibitor main agent include hexanol, phosphorus pentoxide, polyphosphoric acid, phosphorous acid and toluene, and the molar ratio of the hexanol, phosphorus pentoxide, polyphosphoric acid, phosphorous acid and toluene is 1:0.25:0.01:0.01:0.5; the preparation raw materials of the imidazoline oleate in the corrosion inhibitor main agent include oleic acid, diethylene triamine and dimethylbenzene; the molar ratio of the oleic acid, diethylene triamine and dimethylbenzene is 1:1.1:0.9; the surfactant is cetyltrimethylammonium bromide; the solvent is isopropyl alcohol; the synergist is 1,4-butynediol; and the oxygen scavenger is dimethyl ketoxime.

[0036] The preparation methods of the corrosion inhibitor under the coexistence of oxygen and carbon dioxide, the dihexyl hydrogen phosphate and the imidazoline oleate are the same as those in example 1.

[0037] The corrosion inhibitor under the coexistence of oxygen and carbon dioxide resistant condition comprises at least 28 parts of corrosion inhibitor main agent, 4 parts of synergist, 1 part of surfactant, 49 parts of solvent, 14 parts of amino acid and 4 parts of oxygen scavenger by weight; the corrosion inhibitor main agent is composed of 15 parts of dihexyl hydrogen phosphate and 13 parts of imidazoline oleate; the amino acid is a mixture of L-histidine, lysine and tryptophan, and the mass ratio of L-histidine, lysine and tryptophan is 1:0.8:0.5; the preparation raw material of dihexyl hydrogen phosphate in the corrosion inhibitor main agent comprises hexanol, phosphorus pentoxide, polyphosphoric acid, phosphorous acid and toluene, and the molar ratio of hexanol, phosphorus pentoxide, polyphosphoric acid, phosphorous acid and toluene is 1:0.25:0.01:0.01:0.5; the preparation raw material of imidazoline oleate in the corrosion inhibitor main agent comprises oleic acid, diethylene triamine and dimethylbenzene; the molar ratio of oleic acid, diethylene triamine and dimethylbenzene is 1:1.1:0.9; the surfactant is hexadecyl trimethyl ammonium bromide; the solvent is isopropyl alcohol; the synergist is 1,4-butynediol; and the oxygen scavenger is dimethyl ketone oxime.

[0038] The preparation method of the corrosion inhibitor under the coexistence of oxygen and carbon dioxide resistant condition, the dihexyl hydrogen phosphate and the imidazoline oleate is same as that in embodiment 1.

[0039] The corrosion inhibitor under the coexistence of oxygen and carbon dioxide resistant condition comprises at least 20 parts of corrosion inhibitor main agent, 3 parts of synergist, 0.8 parts of surfactant, 45 parts of solvent, 10 parts of amino acid and 4 parts of oxygen scavenger by weight; the corrosion inhibitor main agent is composed of 15 parts of dihexyl hydrogen phosphate and 5 parts of imidazoline oleate; the amino acid is a mixture of L-histidine, lysine and tryptophan, and the mass ratio of L-histidine, lysine and tryptophan is 1:0.7:0.4; the preparation raw material of dihexyl hydrogen phosphate in the corrosion inhibitor main agent comprises hexanol, phosphorus pentoxide, polyphosphoric acid, phosphorous acid and toluene, and the molar ratio of hexanol, phosphorus pentoxide, polyphosphoric acid, phosphorous acid and toluene is 1:0.25:0.01:0.01:0.5; the preparation raw material of imidazoline oleate in the corrosion inhibitor main agent comprises oleic acid, diethylene triamine and dimethylbenzene; the molar ratio of oleic acid, diethylene triamine and dimethylbenzene is 1:1.1:0.9; the surfactant is hexadecyl trimethyl ammonium bromide; the solvent is isopropyl alcohol; the synergist is 1,4-butynediol; and the oxygen scavenger is dimethyl ketone oxime.

[0040] The preparation method of the corrosion inhibitor under the coexistence of oxygen and carbon dioxide resistant condition, the dihexyl hydrogen phosphate and the imidazoline oleate is same as that in embodiment 1.

[0041] Example 5: The corrosion inhibitor under the coexistence of oxygen and carbon dioxide, by weight, at least includes 40 parts of corrosion inhibitor main agent, 3 parts of synergist, 0.8 parts of surfactant, 45 parts of solvent, 10 parts of amino acid and 4 parts of oxygen scavenger; the corrosion inhibitor main agent is composed of 25 parts of dihexyl hydrogen phosphate and 15 parts of imidazoline oleate; the amino acid is a mixture of L-histidine, lysine and tryptophan, and the mass ratio of L-histidine, lysine and tryptophan is 1:0.7:0.4; the preparation raw material of dihexyl hydrogen phosphate in the corrosion inhibitor main agent includes hexanol, phosphorus pentoxide, polyphosphoric acid, phosphorous acid and toluene, and the molar ratio of hexanol, phosphorus pentoxide, polyphosphoric acid, phosphorous acid and toluene is 1:0.25:0.01:0.01:0.5; the preparation raw material of imidazoline oleate in the corrosion inhibitor main agent includes oleic acid, diethylene triamine and dimethylbenzene; the molar ratio of oleic acid, diethylene triamine and dimethylbenzene is 1:1.1:0.9; the surfactant is cetyltrimethylammonium bromide; the solvent is isopropyl alcohol; the synergist is 1,4-butynediol; and the oxygen scavenger is dimethyl ketone oxime.

[0042] The preparation method of the corrosion inhibitor under the coexistence of oxygen and carbon dioxide, the dihexyl hydrogen phosphate and the imidazoline oleate is same as that in example 1.

[0043] Comparative example 1: The corrosion inhibitor under the coexistence of oxygen and carbon dioxide, by weight, at least includes 30 parts of corrosion inhibitor main agent, 5 parts of synergist, 1 part of surfactant, 47 parts of solvent, 11 parts of amino acid and 6 parts of oxygen scavenger; the corrosion inhibitor main agent is composed of 30 parts of imidazoline oleate; the amino acid is a mixture of L-histidine, lysine and tryptophan, and the mass ratio of L-histidine, lysine and tryptophan is 1:0.8:0.4; the preparation raw material of dihexyl hydrogen phosphate in the corrosion inhibitor main agent includes hexanol, phosphorus pentoxide, polyphosphoric acid, phosphorous acid and toluene, and the molar ratio of hexanol, phosphorus pentoxide, polyphosphoric acid, phosphorous acid and toluene is 1:0.25:0.01:0.01:0.5; the preparation raw material of imidazoline oleate in the corrosion inhibitor main agent includes oleic acid, diethylene triamine and dimethylbenzene; the molar ratio of oleic acid, diethylene triamine and dimethylbenzene is 1:1.1:0.9; the surfactant is cetyltrimethylammonium bromide; the solvent is isopropyl alcohol; the synergist is 1,4-butynediol; and the oxygen scavenger is dimethyl ketone oxime.

[0044] The preparation method of the corrosion inhibitor under the coexistence of oxygen and carbon dioxide, the dihexyl hydrogen phosphate and the imidazoline oleate is same as that in example 1.

[0045] The oxygen-carbon dioxide coexisting condition resistant corrosion inhibitor, the dihexyl hydrogen phosphate, and the preparation method of the imidazoline oleate are the same as those in Example 1.

[0046] The oxygen-carbon dioxide coexisting condition resistant corrosion inhibitor, the dihexyl hydrogen phosphate, and the preparation method of the imidazoline oleate are the same as those in Example 1.

[0047] The oxygen-carbon dioxide coexisting condition resistant corrosion inhibitor, the dihexyl hydrogen phosphate, and the preparation method of the imidazoline oleate are the same as those in Example 1.

[0048] The oxygen-carbon dioxide coexisting condition resistant corrosion inhibitor, the dihexyl hydrogen phosphate, and the preparation method of the imidazoline oleate are the same as those in Example 1.

[0049] Corrosion inhibitor performance test: the corrosion inhibition effect evaluation test is based on the People's Republic of China oil and gas industry standard SY / T 5273-2014 "corrosion inhibitor performance index and evaluation method for oilfield produced water treatment", the test conditions are 55℃, simulated field water solution, CO2 pressure 0.1 MPa, the dissolved oxygen content in water at test temperature is 4ppm, the rotating speed is 300r / min, and the hanging piece material is L360 carbon steel.

[0050] Table 1 corrosion inhibition rate of the corrosion inhibitor prepared in examples 1-5 and comparative examples 1-3 .

[0051] Performance test results: corrosion inhibitor corrosion inhibition rate analysis under oxygen-carbon dioxide coexisting conditions: comparative examples 1-5 and comparative examples 1-3 prepared by the prepared compound corrosion inhibitor sample is tested, the results are shown in table 1; from table 1, examples 1-5 can achieve high corrosion inhibition rate, which shows that the corrosion inhibitor prepared by the present application has excellent corrosion inhibition performance in the oxygen and carbon dioxide coexisting environment; among them, the corrosion inhibition rate of example 1 reaches 93.7%, which is the highest value in the examples, which reflects the optimal synergistic effect of the balanced ratio of dihexyl hydrogen phosphate and oleic acid imidazoline; compared with example 1, the corrosion inhibition performance of comparative examples 1-3 is significantly reduced, because: comparative example 1 lacks dihexyl hydrogen phosphate component, only retains oleic acid imidazoline, and the corrosion inhibition rate is reduced to 89.7%; although oleic acid imidazoline can form an adsorption film with the metal surface through the imidazoline ring, but lack of the synergistic effect of the precipitated film of dihexyl hydrogen phosphate, it cannot effectively block the competitive adsorption of O2 and the acid corrosion of CO2, the increase of the exposed active sites on the metal surface, the oxygen accelerates the cathodic depolarization reaction, resulting in the decrease of the corrosion inhibition efficiency; the amount of deoxidizer in comparative example 2 is 3 parts (lower than the lower limit of 4 parts in example 1), and the corrosion inhibition rate is reduced to 86.6%; the insufficient amount of deoxidizer leads to the residual oxygen in the system cannot be effectively removed, and the oxygen as a strong oxidizing agent will destroy the molecular structure of the corrosion inhibitor, at the same time, accelerate the cathodic reaction (O2+2H2O+4e - =4OH -), causing the continuity of the adsorption film to be broken, the penetration of the corrosive medium to be intensified, and the corrosion inhibition performance to be significantly reduced; the amino acid ratio of the comparative example 3 is 1:1:0.6 (exceeding the range of 1:0.8:0.4 of the example 1), and the corrosion inhibition rate is reduced to 90.1%; the imbalance of the amino acid ratio weakens the auxiliary film-forming effect, the repulsive force between the excess lysine (1 part) and tryptophan (0.6 part) molecules is increased, the film layer gap cannot be tightly filled, oxygen and carbon dioxide are more easily penetrated to the metal surface, and the corrosion inhibition effect is inhibited; in summary, the high corrosion inhibition rate of the example is derived from the complete technical solution of "main agent synergy + auxiliary component strengthening", while the comparative examples fail to have the synergistic effect due to the lack of the core component or the deviation from the key parameters, and the difference between the two directly proves that the present application effectively solves the corrosion problem in the environment where oxygen and carbon dioxide coexist by limiting the key features such as the composition of the main agent of the corrosion inhibitor, the amount of the oxygen scavenger, and the ratio of the amino acids, and embodies the inventiveness of the present application.

Claims

1. A corrosion inhibitor resistant to oxygen-carbon dioxide coexistence conditions, characterized in that: The invention comprises, by weight, 20-40 parts of a corrosion inhibitor main agent, 3-7 parts of a synergist, 0.8-1.2 parts of a surfactant, 45-55 parts of a solvent, 10-18 parts of an amino acid, and 4-8 parts of an oxygen scavenger; the corrosion inhibitor main agent is composed of 15-25 parts of dihexyl hydrogen phosphate and 5-15 parts of oleic acid imidazoline; the synergist comprises 3-7 parts of an organic alkynol.

2. The corrosion inhibitor resistant to oxygen-carbon dioxide coexistence conditions according to claim 1, characterized in that: The structural formula of the dihexyl hydrogen phosphate is HO-P(O)(OC6H 13 )2, containing a phosphate group -OP(O)(OH)- and two hexyl chains (-C6H 13 ).

3. The corrosion inhibitor resistant to oxygen-carbon dioxide coexistence conditions according to claim 1, characterized in that: The structural formula of the oleic acid imidazoline comprises an imidazoline ring, a hydroxyl group and a long-chain alkyl group derived from oleic acid, and the imidazoline ring is connected to the long-chain alkyl group and the hydroxyl group via a nitrogen atom.

4. The corrosion inhibitor resistant to oxygen-carbon dioxide coexistence conditions according to claim 1, characterized in that: The surfactant is one of cetyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, and sodium lauryl sulfate; and the solvent is one of isopropyl alcohol, propanol, and ethanol.

5. The corrosion inhibitor resistant to oxygen-carbon dioxide coexistence conditions according to claim 1, characterized in that: The amino acid is a mixture of L-histidine, lysine and tryptophan, and the mass ratio of L-histidine, lysine and tryptophan is 1:(0.7-0.9):(0.3-0.5); the oxygen scavenger is one or more of hydrazine, dimethylketoxime, isoascorbic acid and sodium ascorbate.

6. A method for preparing dihexyl hydrogen phosphate, characterized in that: The following steps are involved: S11. Add hexanol, toluene and phosphorous acid to an enameled reactor, evacuate to -0.09 MPa, fill with nitrogen with a purity of ≥99.99%, repeat 3 times to replace oxygen, and stir at 40°C for 10-15 minutes; heat to 80±2°C, reflux for 1 hour to remove moisture, and obtain a mixed solution; S12. Add polyphosphoric acid to the mixed solution, cool to 35-40°C in an ice bath, and then add phosphorus pentoxide in batches, keep warm and stir for 1 hour, then heat to 85±5°C, keep warm and react for 6 hours, and cool to 20-25°C after the reaction is completed; S13. Add 5% Na2CO3 solution to the reaction solution at a volume ratio of 1:1; stir for 30 minutes, let stand and separate, then take the upper organic phase, and conduct vacuum distillation on the organic phase to obtain a light yellow liquid dihexyl hydrogen phosphate.

7. The method for preparing dihexyl hydrogen phosphate according to claim 6, wherein The molar ratio of the hexanol, phosphorus pentoxide, polyphosphoric acid, phosphorous acid and toluene is 1: (0.2-0.4): (0.008-0.01): (0.01-0.015): (0.3-0.6).

8. A method for preparing a corrosion inhibitor resistant to oxygen and carbon dioxide coexistence according to any one of claims 1 to 5, characterized in that: The corrosion inhibitor main agent, synergist, surfactant, solvent, amino acid and deoxidizer were added to the reactor in parts by weight, with stirring temperature of 25-30°C, stirring speed of 300 r / min and stirring time of 30 minutes to obtain a corrosion inhibitor resistant to oxygen-carbon dioxide coexistence conditions.

9. Use of the corrosion inhibitor according to any one of claims 1 to 5 or the corrosion inhibitor prepared by the preparation method according to claim 8 in the field of oil and gas field corrosion protection.

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