Low-corrosivity crude oil decalcifying agent and preparation method thereof

Abstract

The invention discloses a low-corrosivity crude oil decalcifying agent and a preparation method thereof. The low-corrosivity crude oil decalcifying agent comprises the following components: a selective chelating agent, polyether quaternary ammonium salt and a sulfonate surfactant, the selective chelating agent has high selectivity on calcium ions and high water solubility with chelates of the calcium ions, so that the selective chelating agent has an excellent decalcification effect; the decalcifying agent does not contain inorganic acid, so that the decalcifying agent has low corrosion to equipment; the polyether quaternary ammonium salt has the effects of neutralizing surface charges of water-phase liquid drops, promoting coalescence of the liquid drops and stabilizing and flocculating clay particles; the sulfonate surfactant has the effect of dispersing asphaltene and metal compound particles, so that a solid interface film on the surface of a water-phase liquid drop is collapsed, and liquid drop coalescence is promoted; the three components synergistically play a role in improving the decalcification effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of petroleum decalcification technology, in particular to a low-corrosion crude oil decalcification agent and a preparation method thereof. BACKGROUND

[0002] The crude oil decalcification agent is a chemical agent added to remove calcium impurities (usually in the form of calcium naphthenate, calcium chloride and other inorganic and organic calcium salts) existing in crude oil. These calcium impurities can cause serious harm to the refining process, such as catalyst poisoning, equipment fouling and corrosion, etc. An ideal crude oil decalcification agent should have the following key properties: (1) high decalcification efficiency: it can quickly and completely react with calcium ions to form stable compounds that are easy to separate; (2) excellent selectivity: it preferentially reacts with harmful metal ions such as calcium, magnesium and iron, and as little as possible with valuable metals (such as vanadium and nickel) or other components in the crude oil to avoid unnecessary side reactions that cause yield loss or property changes; (3) good compatibility and compatibility: including compatibility with crude oil and compatibility with demulsifiers, without causing emulsification, precipitation or other stability problems, and preferably having certain demulsification function; (4) easy separation of generated products: the compounds (such as precipitates) generated after reaction with calcium should have good oil-repellent and water-repellent properties, and can quickly transfer from the oil phase to the water phase and be completely removed with the water discharge process of electric desalting; (5) high safety: the corrosion of the decalcification agent to the equipment, pipelines and storage tanks of the refinery should be as low as possible to avoid introducing new equipment damage risks. However, the existing decalcification agents have the problems of insufficient selectivity, poor compatibility with demulsifiers, difficulty in separation and poor corrosion resistance to equipment.

[0003] In view of this, the present application is proposed. SUMMARY

[0004] The present application proposes a low-corrosion crude oil decalcification agent and a preparation method thereof, aiming to improve one or more technical problems in the background art.

[0005] The present application is implemented as follows: In a first aspect, the present application provides a low-corrosion crude oil decalcification agent, comprising the following components: a selective chelating agent, a polyether quaternary ammonium salt and a sulfonate surfactant; the selective chelating agent has the following formula I molecular structure: (I); in the formula, R is H or methyl.

[0006] The selective chelating agent provided by the present application has high selectivity to calcium ions, and the chelate of the selective chelating agent and calcium ions has high water solubility, so that the selective chelating agent has excellent decalcification effect; the decalcification agent does not contain inorganic acid, so the corrosion of the equipment is low. The low-corrosion crude oil decalcification agent provided by the present application further adds polyether quaternary ammonium salt and sulfonate surfactant, and the two can promote the coalescence of liquid droplets in crude oil and promote the dissolution of the chelate into the water phase, thereby improving the decalcification effect.

[0007] In the soft-hard acid-base theory, calcium ions belong to hard acid, and iron ions and nickel ions belong to relatively soft acid, so the use of hard base ligand is beneficial to improve the selectivity to calcium ions. The hard base ligand includes oxygen-containing ligand (COO-, -OH, etc.), hard nitrogen ligand (A-C=N, A is an electron-withdrawing group), and the tertiary amine on the broad-spectrum metal chelating agent (such as ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, etc.) belongs to soft base coordination group, so the selective chelating agent provided by the present application has higher selectivity to calcium ions, and the structure of the chelate of the selective chelating agent and calcium ions is shown in the accompanying Figure 3 Secondly, the radius of calcium ions is larger than that of iron ions and nickel ions, so the sensitivity to steric hindrance is weaker, and therefore calcium ions can better adapt to ligands with large steric hindrance and strong molecular structure rigidity than iron ions and nickel ions. In contrast, the broad-spectrum metal chelating agent (such as ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, etc.) has high molecular flexibility, so it can twist freely to build a molecular cage matching the metal ions, and therefore the selectivity is poor. The selective chelating agent obtained by molecular structure design in the present application has high matching to the radius of calcium ions, so it has high selectivity. Furthermore, the selective chelating agent contains free hydroxyl groups (with hydration effect) and has low content of hydrophobic alkyl groups, so the chelate of the selective chelating agent and calcium ions has higher hydrophilicity, which is beneficial to transfer to the water phase after chelating metal ions, thereby improving the decalcification rate. The polymer type decalcification agent has high content of hydrophobic alkyl groups, and generally has better oil solubility than the selective chelating agent, which is not conducive to the transfer of the chelate to the water phase, resulting in the decrease of the decalcification efficiency; on the other hand, the molecular chain segment of the polymer type decalcification agent has high flexibility, so the ion selectivity is also low.

[0008] In some embodiments, the polyether quaternary ammonium salt is at least one of polyquaternium-10 and polyquaternium-42; the polyether quaternary ammonium salt has the effects of neutralizing the surface charge of the water phase droplets, promoting the coalescence of the droplets, and stabilizing the flocculation of clay particles.

[0009] In some embodiments, the sulfonate surfactant is at least one of lignin sulfonate, alkylbenzene sulfonate and alkyl sulfonate; the sulfonate surfactant has the effects of dispersing asphaltene and metal compound particles, thereby breaking the solid interface film on the surface of the water phase droplets and promoting the coalescence of the droplets.

[0010] In some embodiments, the low-corrosion crude oil decalcifying agent further comprises a steric-hindering agent selected from at least one of sorbitol, mannitol and glycerol. The low-corrosion crude oil decalcifying agent provided by the present application can further improve the water solubility of the chelate of the selective chelating agent and calcium ions and prevent the chelate from transferring back to the oil phase by adding the steric-hindering agent. The principle is as follows: the steric-hindering agent has high water solubility and forms a thick hydration layer after being dissolved in water, so it has weak affinity with the chelate, i.e. there is repulsion (steric hindrance), so it is more inclined to stay in the solution, so that the concentration of the steric-hindering agent in the area near the chelate is low, in other words, the concentration of water molecules in the area near the chelate is relatively high, so that the chelate is stabilized and is difficult to transfer back to the oil phase.

[0011] In some embodiments, the low-corrosion crude oil decalcifying agent further comprises an inorganic salt selected from at least one of ammonium chloride, ammonium nitrate and ammonium sulfate; the addition of the inorganic salt can improve the polarity of the water phase, so as to improve the dehydration efficiency of electric dehydration.

[0012] In some embodiments, the low-corrosion crude oil decalcifying agent comprises the following components in percentage by mass: 40% to 70% of the selective chelating agent, 1% to 10% of the polyether quaternary ammonium salt, 1% to 5% of the sulfonate surfactant, 0% to 15% of the steric-hindering agent, 0% to 8% of the inorganic salt, and the balance being the solvent.

[0013] In some embodiments, the solvent comprises at least one of water, ethylene glycol ether, ethanol, propanol, isopropanol, petroleum ether, toluene and xylene.

[0014] In the second aspect, the present application provides a preparation method of the low-corrosion crude oil decalcifying agent described above, comprising the following steps: (1) preparing the selective chelating agent: performing Schiff base reaction of carboxyl-protected serine and carboxyl-protected 2-oxo-propionic acid or carboxyl-protected 2-oxo-acetic acid under the catalysis of alkali; and obtaining the intermediate product, which is deprotected, purified and dried to obtain the selective chelating agent; (2) mixing the selective chelating agent, the polyether quaternary ammonium salt and the sulfonate surfactant to obtain component A; (3) dissolving the steric-hindering agent and the inorganic salt in the solvent to obtain component B; (4) mixing component A and component B to obtain the low-corrosion crude oil decalcifying agent.

[0015] In some embodiments, the carboxyl-protected serine is serine benzyl ester hydrochloride or serine methyl ester hydrochloride.

[0016] In some embodiments, the carboxyl-protected 2-oxo-propionic acid is tert-butyl 2-oxo-propionate, benzyl 2-oxo-propionate or methyl pyruvate.

[0017] In some embodiments, the carboxyl-protected 2-oxoacetic acid is tert-butyl 2-oxoacetate, benzyl 2-oxoacetate or methyl oxalate.

[0018] In some embodiments, the base is N,N-diisopropylethylamine or / and triethylamine.

[0019] In some embodiments, the solvent for the Schiff base reaction is dichloromethane or toluene.

[0020] In some embodiments, the temperature for the Schiff base reaction is 25-40℃ and the time is 8-24h.

[0021] In some embodiments, the deprotection refers to removing the carboxyl-protecting group, i.e. converting the carboxylate group of the intermediate product into a carboxyl group, and the deprotection is performed by selecting any one or a combination of two of the following (1)-(3): (1) dissolving the intermediate product in an alcohol, adding a palladium-carbon catalyst, and then stirring the reaction under hydrogen; (2) dissolving the intermediate product in a solution of trifluoroacetic acid in dichloromethane and stirring the reaction; (3) dissolving the intermediate product in an alkaline aqueous solution and stirring the reaction.

[0022] The present application has the following beneficial effects: The present application provides a low-corrosive crude oil decalcifying agent, which contains a selective chelating agent having high selectivity for calcium ions and a high water solubility of the chelate with calcium ions, thus having excellent decalcification effect; and the decalcifying agent does not contain inorganic acid, thus having low corrosion to equipment. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0024] Figure 1 The ultraviolet absorption spectrum of the chelate obtained by mixing the selective chelating agent prepared in Example 1 of the present application with different metal ions; Figure 2 The ultraviolet absorption spectrum of the chelate obtained by mixing the selective chelating agent prepared in Example 2 of the present application with different metal ions.

[0025] Figure 3 The structural schematic diagram of the chelate of the selective chelating agent prepared in Example 1 of the present application with calcium ions. DETAILED DESCRIPTION

[0026] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions suggested by the manufacturers are adopted. If the manufacturers of the reagents or instruments are not specified, the conventional products that can be purchased in the market are adopted.

[0027] In the description of the embodiments of the present application, the technical terms "first", "second" and the like are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0028] Reference to "embodiments" herein means that the specific features, structures or properties described in connection with the embodiments can be included in at least one embodiment of the present application. The appearance of this phrase at various places in the specification does not necessarily refer to the same embodiment, nor is it mutually exclusive or alternative to other embodiments.

[0029] In the embodiments of the present application, the term "or / and" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A or / and B, which can mean that A exists alone, A and B exist simultaneously, and B exists alone.

[0030] In addition, the character " / " herein generally represents that the associated objects before and after are in an "or" relationship.

[0031] In the embodiments of the present application, the meaning of "multiple" is two or more (including two), and similarly, "multiple groups" means two or more groups (including two groups), and "multiple layers" means two or more layers (including two layers), unless otherwise specified and limited.

[0032] In the embodiments of the present application, the meaning of "at least one" is one or more than one.

[0033] The specific meanings of the above terms in the embodiments of the present application can be understood by those skilled in the art according to specific circumstances.

[0034] The features and properties of the present application will be further described below in combination with the embodiments.

[0035] Embodiment 1

[0036] A low-corrosive crude oil decalcification agent, according to the mass percentage, includes the following components: 60% selective chelating agent, 5% polyquaternary ammonium salt-10 and 1% sodium lignosulfonate, and the balance is ethylene glycol ether; The selective chelating agent has the following formula I-1 structure: (Formula I-1).

[0037] A method for preparing a low-corrosive crude oil decalcifying agent, comprising the following steps: (1) Measure the amount of serine benzyl ester hydrochloride and 2-oxoacetic acid benzyl ester, dissolve them in anhydrous dichloromethane, and add 4A molecular sieves. After nitrogen replacement, inject triethylamine, stir at 25°C for 12h, filter and dry the obtained reaction solution to obtain an intermediate product; wherein the molar ratio of serine benzyl ester hydrochloride and 2-oxoacetic acid benzyl ester is 1:1; the molar amount of triethylamine is 1.5 times that of serine benzyl ester hydrochloride; the mass of molecular sieves is 5 times the theoretical yield of water; (2) Dissolve the intermediate product in methanol, add palladium-carbon catalyst (10wt% Pd), then pass in hydrogen, and stir at room temperature for 8h. Filter and dry the obtained reaction solution to obtain a selective chelating agent; wherein the mass of palladium-carbon catalyst is 11 times the theoretical yield of toluene; the reaction pressure is maintained at 0.2MPa by passing in hydrogen; The selective chelating agent has the following structure: 1 H-NMR (400MHz, CDCl3): 2.32 (t, CH, 1H), 3.7~3.9 (m, CH2, 2H), 6.28 (s, OH, 1H), 8.17 (s, N=CH, 1H), 12.14 (s, COOH, 1H), 12.25 (s, COOH, 1H).

[0038] (3) Mix the selective chelating agent, polyquaternary ammonium salt-10, and sodium lignosulfonate, and dissolve them in ethylene glycol ether to obtain a low-corrosive crude oil decalcifying agent.

[0039] Polyquaternary ammonium salt-10 (chloride-2-hydroxy-3-(trimethylammonium) propyl polyethylene oxide cellulose ether) and sodium lignosulfonate are purchased from Shanghai Sigma-Aldrich.

[0040] Example 2

[0041] The difference between Example 1 and Example 2 is that the selective chelating agent has the following structure I-2: (Formula I-2).

[0042] A method for preparing a low-corrosive crude oil decalcifying agent, comprising the following steps: (1) Measure the amount of serine benzyl ester hydrochloride and 2-oxoacetic acid benzyl ester, dissolve them in anhydrous dichloromethane, and add 4A molecular sieves. After nitrogen replacement, inject triethylamine, stir at 25°C for 12h, filter and dry the obtained reaction solution to obtain an intermediate product; wherein the molar ratio of serine benzyl ester hydrochloride and 2-oxoacetic acid benzyl ester is 1:1; the molar amount of triethylamine is 1.5 times that of serine benzyl ester hydrochloride; the mass of molecular sieves is 5 times the theoretical yield of water; (2) The intermediate product is dissolved in a mixed solution of ethanol and water (v(methanol):v(water)=1:1), and sodium hydroxide is added to make the concentration of sodium hydroxide 2M, and heated to 60°C to reflux for 12h. The obtained reaction liquid is placed in an ice water bath at 0°C, 1M hydrochloric acid is added to adjust the pH to 2, then dichloromethane is added to extract the target product 3 times, and the organic phase is combined and dried by rotary evaporation to obtain the selective chelating agent.

[0043] The selective chelating agent of the present application has the following advantages: 1 H-NMR (400MHz, CDCl3): 2.07(s, CH3, 3H), 2.34(t, CH, 1H), 3.7~3.9(m, CH2, 2H), 6.29(s, OH, 1H), 12.16(s, COOH, 1H), 12.27(s, COOH, 1H).

[0044] (3) The selective chelating agent, polyquaternary ammonium salt-10 and sodium lignosulfonate are mixed and dissolved in ethylene glycol ether to obtain a low-corrosion crude oil decalcification agent.

[0045] Example 3

[0046] A low-corrosion crude oil decalcification agent, according to mass percentage, includes the following components: 60% selective chelating agent (formula I-1), 5% polyquaternary ammonium salt-10, 1% sodium lignosulfonate and 5% sorbitol, and the balance is ethylene glycol ether.

[0047] The rest is the same as example 1.

[0048] Example 4

[0049] A low-corrosion crude oil decalcification agent, according to mass percentage, includes the following components: 60% selective chelating agent (formula I-1), 5% polyquaternary ammonium salt-10, 1% sodium lignosulfonate and 4% ammonium sulfate, and the balance is ethylene glycol ether.

[0050] The rest is the same as example 1.

[0051] Example 5

[0052] A low-corrosion crude oil decalcification agent, according to mass percentage, includes the following components: 60% selective chelating agent (formula I-1), 5% polyquaternary ammonium salt-10, 1% sodium lignosulfonate, 5% sorbitol and 4% ammonium sulfate, and the balance is ethylene glycol ether.

[0053] The rest is the same as example 1.

[0054] Example 6

[0055] A low-corrosive crude oil decalcifying agent, comprising the following components in percentage by mass: 40% of a selective chelating agent (Formula I-1), 10% of polyquaternium-42, 5% of sodium myristyl sulfonate, 15% of mannitol, and 2% of ammonium chloride, with the balance being water.

[0056] The rest is the same as Example 1.

[0057] Polyquaternium-42 (polyoxyethylene dimethyl imino ethylene dimethyl imino ethylene dichloride) is purchased from Saimin Chemical (Shanghai) Co., Ltd.

[0058] Example 7

[0059] A low-corrosive crude oil decalcifying agent, comprising the following components in percentage by mass: 70% of a selective chelating agent (Formula I-1), 1% of polyquaternium-42, 1% of sodium cetyl benzene sulfonate, and 8% of ammonium nitrate, with the balance being toluene.

[0060] The rest is the same as Example 1.

[0061] Comparative Example 1 A low-corrosive crude oil decalcifying agent, comprising the following components in percentage by mass: 60% of a selective chelating agent (Formula I-1) and 1% of sodium lignosulfonate, with the balance being ethylene glycol ethyl ether.

[0062] The rest is the same as Example 1.

[0063] Comparative Example 2 A low-corrosive crude oil decalcifying agent, comprising the following components in percentage by mass: 60% of a selective chelating agent (Formula I-1), 5% of polyquaternium-10, with the balance being toluene.

[0064] Comparative Example 3 A low-corrosive crude oil decalcifying agent, comprising the following components in percentage by mass: 60% of diethylene triamine pentaacetic acid, 5% of polyquaternium-10, and 1% of sodium lignosulfonate, with the balance being ethylene glycol ethyl ether.

[0065] Comparative Example 4 A low-corrosive crude oil decalcifying agent, comprising the following components in percentage by mass: 60% of maleic acid-acrylic acid copolymer sodium salt, 5% of polyquaternium-10, and 1% of sodium lignosulfonate, with the balance being ethylene glycol ethyl ether.

[0066] Maleic acid-acrylic acid copolymer sodium salt is purchased from Shandong Zhengtai New Material Co., Ltd.

[0067] The rest is the same as Example 1.

[0068] Test Example 1 A concentration of 1×10 -5M The methanol solution of selective chelating agent prepared by example 1 and example 2 of the present application, take several 3mL methanol solution of selective chelating agent placed in a cuvette, then add 30μL of methanol, 1×10 -3 M The methanol solution of selective chelating agent prepared by example 1 and example 2 of the present application, take several 3mL methanol solution of selective chelating agent placed in a cuvette, then add 30μL of methanol, 1×10 -3 M The methanol solution of selective chelating agent prepared by example 1 and example 2 of the present application, take several 3mL methanol solution of selective chelating agent placed in a cuvette, then add 30μL of methanol, 1×10 -3 M The methanol solution of selective chelating agent prepared by example 1 and example 2 of the present application, take several 3mL methanol solution of selective chelating agent placed in a cuvette, then add 30μL of methanol, 1×10 Figure 1 and as shown in the attached Figure 2 .

[0069] As can be seen from the figure, the absorption spectrum of the methanol solution of selective chelating agent appears strong ultraviolet absorption band at 200~300nm and weak ultraviolet absorption band at 300-340 nm. When calcium chloride is added, the absorption peaks at 230nm and 320nm are red shifted and the intensity decreases; when iron chloride is added, the absorption peaks at 230nm and 320nm are also red shifted and the intensity decreases, but the degree is less than that of calcium chloride; when nickel chloride is added, the absorption peaks change little, which shows that the selective chelating agent provided by the present application has the highest selectivity for calcium ion, followed by iron ion, and has poor chelating ability for nickel ion.

[0070] Test example 2 The calcium stearate and emulsifier span80 are dissolved in toluene to obtain a calcium solution with a calcium ion concentration of 0.1g / L and a mass percentage of span80 of 5%, and the size exclusion agent mannitol is dissolved in deionized water to obtain a mannitol solution with a concentration of 5g / L; the calcium solution and the test group solution or deionized water are mixed in proportion, and a water-in-oil emulsion is obtained after homogenization at 2000rpm for 15min; the selective chelating agent is added to the emulsion (the selective chelating agent is added according to the ratio of the molar amount of calcium ion n(Ca) to the molar amount of selective chelating agent n(selective chelating agent) of 1:2~3), and homogenization is carried out at 500rpm for 10min, then the demulsifier SP-169 (purchased from Haian Petroleum Chemical Industry in Jiangsu Province) is added and homogenization is continued for 10min, and the emulsion is left to stand for 30min, and the toluene phase is taken and the calcium content is tested by inductively coupled plasma emission spectrometry, and the calcium removal rate = (1- calcium content in toluene phase after demulsification ÷ initial calcium content) ×100%, and the results are shown in Table 1.

[0071] Table 1

[0072] As shown in Table 1, the addition of the steric hindrance agent solution is beneficial to the improvement of the calcium removal rate, because the steric hindrance agent is beneficial to the improvement of the water solubility of the chelate. Secondly, with the decrease of n(Ca):n(selective chelating agent), i.e. the more the amount of the selective chelating agent, the calcium removal rate first increases and then decreases, because the chelate competes with the free selective chelating agent which is not coordinated for dissolving in the aqueous phase, and if the selective chelating agent is too much, the chelate remains in the aqueous phase.

[0073] Test Example 3 The calcium content in the experimental crude oil is 104 ppm, and the gum is 13%. 285 g of the experimental crude oil, 15 g of distilled water and 130 ppm of the demulsifier SP-169 are mixed uniformly, and are preheated at 80°C for 30 min. After preheating, the mixture is transferred to a device with a stirrer and stirred at a strength of 1500 r / min for 10 min, and is then transferred to a YS-3 type electric desalting tester for secondary desalting. The addition amount of the calcium removal agent in the primary desalting is 1200 μg / L, and an equal amount of water is supplemented in the secondary desalting, and the calcium removal agent is supplemented at 600 μg / L. The test conditions are as follows: the electric desalting temperature is 100°C, the strong electric field strength is 1500 V / cm, the residence time is 10 min, the weak electric field strength is 400 V / cm, the residence time is 15 min, and the sedimentation time is 30 min. The metal elements before and after the electric desalting are determined by inductively coupled plasma emission spectrometry on the middle sample in the oil phase, and the calcium removal rate and the nickel removal rate are calculated. The calcium removal rate = (calcium content in the crude oil - calcium content in the oil phase after desalting) / calcium content in the crude oil x 100%, after the desalting is completed, the bottom valve is opened to discharge the residue, the residue is dried and weighed to obtain the residue amount, and the residue rate = residue amount after desalting ÷ mass of the experimental crude oil x 100% is calculated. The results are shown in Table 2.

[0074] Table 2

[0075] As shown in Table 2, the selectivity of calcium ions in Example 2 is higher than that in Example 1, because the R group in Formula I is methyl, which makes the steric hindrance of the selective chelating agent larger, and thus the chelating ability of the nickel ions is weaker. In Example 3, Example 4 and Example 5, the steric hindrance agent, inorganic salt and steric hindrance agent and inorganic salt are added respectively, and thus the calcium removal rate is higher. In Comparative Example 3 and Comparative Example 4, diethylenetriamine pentaacetic acid and polycarboxylic acid are used as the chelating agent respectively, and it can be seen that both the calcium removal rate and the selectivity of calcium ions are poorer than those in Example 1. The low calcium removal rate is due to the poor water solubility of diethylenetriamine pentaacetic acid and polycarboxylic acid, and the low selectivity of calcium ions is due to the large degree of freedom of the molecular chain segments of the two. In Comparative Example 1 and Comparative Example 2, the polyether quaternary ammonium salt and sulfonate surfactant are not added respectively, and thus the calcium removal rate is poorer than that in Example 1, which indicates that the two can promote demulsification and improve the water solubility of the chelate.

[0076] The residue composition after desalting includes sludge (asphaltene, clay, metal compound particles) and chelation flocculation, etc., and the residue rate can reflect the demulsification and flocculation of the decalcifying agent. From the data in Table 2, it can be seen that the comparative example 1 and the comparative example 2 do not add polyquaternary ammonium salt and sodium lignosulfonate respectively relative to the example 1, and therefore the residue rate is low.

[0077] The preferred embodiments of the present application have been described above, but the present application is not limited to the above examples, and various modifications and changes can be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A low-corrosive crude oil decalcifying agent, characterized in that: The invention comprises the following components: a selective chelating agent, a polyether quaternary ammonium salt and a sulfonate surfactant; the selective chelating agent has the following molecular structure of formula I: (I); wherein R is H or methyl.

2. The low-corrosive crude oil decalcifying agent according to claim 1, characterized in that: The polyether quaternary ammonium salt is at least one of polyquaternium-10 and polyquaternium-42.

3. The low-corrosive crude oil decalcifying agent according to claim 1, characterized in that: The sulfonate surfactant is at least one of lignin sulfonate, alkylbenzene sulfonate and alkyl sulfonate.

4. The low-corrosive crude oil decalcifying agent according to any one of claims 1 to 3, characterized in that: The low-corrosive crude oil decalcifying agent further comprises an exclusion agent, wherein the exclusion agent is selected from at least one of sorbitol, mannitol and glycerol; And / or, the low-corrosive crude oil decalcifying agent further comprises an inorganic salt, and the inorganic salt is selected from at least one of ammonium chloride, ammonium nitrate and ammonium sulfate.

5. The low-corrosive crude oil decalcifying agent according to claim 4, characterized in that: The low-corrosive crude oil decalcifying agent comprises the following components, calculated by mass percentage: 40%~70% selective chelating agent, 1~10% polyether quaternary ammonium salt, 1%~5% sulfonate surfactant, 0~15% exclusion agent and 0~8% inorganic salt, the balance is solvent.

6. The low-corrosive crude oil decalcifying agent according to claim 5, characterized in that: The solvent includes at least one of water, glycol ether, ethanol, propanol, isopropanol, petroleum ether, toluene and xylene.

7. The method for preparing the low-corrosive crude oil decalcifying agent according to any one of claims 1 to 6, characterized in that: The steps include: (1) Preparation of a selective chelating agent: Carboxyl protected serine and carboxyl protected 2-oxopropionic acid or carboxyl protected 2-oxoacetic acid are subjected to a Schiff base reaction under base catalysis; the obtained intermediate product is deprotected, purified, and dried to obtain a selective chelating agent; (2) mixing a selective chelating agent, a polyether quaternary ammonium salt, and a sulfonate surfactant to obtain component A; (3) Dissolving the exclusion agent and inorganic salt in a solvent to obtain component B; (4) Component A and component B are mixed to obtain a low-corrosive crude oil decalcifying agent.

8. The preparation method according to claim 7, characterized in that The carboxyl protected serine is serine benzyl ester hydrochloride or serine methyl ester hydrochloride; and / or, the carboxyl-protected 2-oxopropionic acid is tert-butyl 2-oxopropionate, benzyl 2-oxopropionate or methyl pyruvate; And / or, the carboxyl-protected 2-oxoacetic acid is tert-butyl 2-oxoacetate, benzyl 2-oxoacetate or methyl glyoxylate.

9. The preparation method according to claim 7 or 8, characterized in that The base is N,N-diisopropylethylamine and / or triethylamine; and / or, the solvent for the Schiff base reaction is dichloromethane or toluene; And / or, the temperature of the Schiff base reaction is 25-40° C., and the time is 8-24 hours.

10. The preparation method according to claim 7, characterized in that The deprotection refers to the removal of the carboxyl protecting group, that is, converting the carboxylate group of the intermediate product into a carboxyl group, and the deprotection is performed by selecting any one of the following (1) to (3) or a combination of two methods: (1) dissolving the intermediate product in alcohol, adding a palladium carbon catalyst, and then introducing hydrogen to stir the reaction; (2) dissolving the intermediate product in a dichloromethane solution of trifluoroacetic acid and stirring the reaction; (3) dissolving the intermediate product in an alkaline aqueous solution and stirring the reaction.

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