A one-step green synthesis method for preparing polyquaternary ammonium salts

Abstract

The invention discloses a one-step green synthesis method for preparing polyquaternary ammonium salts. The preparation method comprises the following steps: mixing polyamines, inorganic alkaline substances and water, adding dimethyl sulfate thereto for reaction, and obtaining a solution of the polyquaternary ammonium salts after the reaction is completed. Compared with the two-step method, the one-step method not only saves the step of preparing intermediates, but also shortens the reaction time, and the product is an aqueous solution (no need for post-treatment separation) and can be directly used as an oil displacement agent or oilfield auxiliary agent, thereby reducing energy consumption and raw material consumption and improving economic benefits. The one-step method is a method that conforms to the principle of green chemistry and is conducive to the industrial production and application of polyquaternary ammonium salts.

Description

Technical Field

[0001] The invention relates to the field of organic synthesis, and in particular to a one-step green synthesis method for preparing polyquaternary ammonium salts. Background Art

[0002] Quaternary ammonium salts are widely used chemical products, among which mono-, di- and poly-quaternary ammonium salts have important applications in oil field development. They can be used as molecular deposition (MD) film agents to form nano-scale molecular deposition films on the surface and inside of the reservoir through electrostatic interactions with the reservoir surface / interface, thereby changing the wettability and permeability of the reservoir and improving the recovery rate. In addition, quaternary ammonium salts can also be used as clay stabilizers, anti-swelling and plugging-removing injection agents, effectively improving the water-oil well injection effect (Gao Manglai, Yu Kai. Use of monomolecular diquaternary ammonium salts in oil field oil recovery and crude oil demulsification [P]. Beijing: CN1227305A, 1999. Gao Manglai. Use of monomolecular monoquaternary ammonium salts and monomolecular quaternary ammonium salts [P]. Beijing: CN1510101A, 2002. Gao Manglai. Catalytic cracking use of monomolecular quaternary ammonium salts [P]. Beijing: CN1509814A, 2002. Gao Manglai. Use of monomolecular quaternary ammonium salt compounds as clay stabilizers, anti-swelling and plugging-removing injection agents [P]. Beijing: CN1556169A, 2004.).

[0003] Luo et al. (Wettability studies of reduced-charge montmorillonites modified by quaternary ammonium salts using capillary rise test [J]. Powder Technology, 2014 (266): 167-174.) used a two-step method to prepare a series of quaternary ammonium salts. The entire synthesis process is complicated. The two-step method requires the generation of intermediate products and then reacts with dimethyl sulfate to generate the final product. This process involves changes in multiple reagents, solvents, and conditions, and requires precise control of parameters such as reaction temperature, time, and pH value. Summary of the invention

[0004] The object of the present invention is to provide a one-step green synthesis method for preparing polyquaternary ammonium salts, so as to promote the industrial production of polyquaternary ammonium salts and their application in oil field development. The present invention uses polyamines as raw materials, drips dimethyl sulfate under alkaline solution conditions, and synthesizes a series of polyquaternary ammonium salts. The preparation method of the present invention has a single raw material, a short reaction time, a high raw material utilization rate, and is simple to operate, does not require post-processing, and has no carbon emission.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A one-step green synthesis method for preparing polyquaternary ammonium salts, the preparation method comprising the following steps:

[0007] The polyamine, the inorganic alkaline substance and water are mixed, and dimethyl sulfate is added thereto for reaction. After the reaction is completed, a solution of the polyquaternary ammonium salt is obtained.

[0008] The present invention selects dimethyl sulfate as the methylating agent, and can methylate the polyamine only in an alkaline solution. The reaction activity is high, and the concentration of the finally obtained polyquaternary ammonium salt solution can be ensured to be appropriate, and the solution can be directly used without post-treatment.

[0009] According to the preparation method of the present invention, preferably, the structural formula of the polyamine is: H2N-(CH2CH2NH) n -H, wherein n is an integer from 2 to 10.

[0010] According to the preparation method of the present invention, preferably, the polyamine is selected from one or a combination of two or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine.

[0011] According to the preparation method of the present invention, preferably, the inorganic alkaline substance is selected from one or a combination of two or more of sodium hydroxide, sodium bicarbonate, and sodium carbonate; more preferably, the inorganic alkaline substance is sodium hydroxide.

[0012] In the preparation method of the present invention, compared with sodium carbonate and sodium bicarbonate, the sample content obtained by using sodium hydroxide as a reactant is the highest and has good solubility. The sample content is 9% higher than that using sodium carbonate on average, and 13% higher than that using sodium bicarbonate on average.

[0013] According to the preparation method of the present invention, preferably, the volume ratio of water to polyamine is (4.0-9.0):1.0.

[0014] During the research and development process of the present invention, it was found that the molar ratio of polyamine, dimethyl sulfate and inorganic alkaline substance has a great relationship with the amount of water used. Within the above-defined range of water usage, when the polyamine is diethylenetriamine, preferably, the molar ratio of diethylenetriamine, dimethyl sulfate and inorganic alkaline substance is 1:(5.0-6.0):(2.0-2.5); more preferably 1:(5.3-5.6):(2.0-2.2).

[0015] Wherein when the inorganic alkaline substance is sodium hydroxide, its addition ratio can be appropriately adjusted to reduce the waste of raw materials and the generation of byproducts water and sodium sulfate. When the sodium hydroxide addition ratio is 2.0-2.2, the pH of the final product can be controlled at a relatively suitable value. The addition ratio of dimethyl sulfate should not be too high to prevent incomplete reaction of dimethyl sulfate, resulting in the generation of a byproduct such as potassium sulfate sodium. When the dimethyl sulfate addition ratio is 5.3-5.6, the final sample concentration can be controlled at a higher level. Below when the polyamine is triethylenetetramine or tetraethylenepentamine or pentaethylenehexamine, the molar ratio of polyamine, dimethyl sulfate and inorganic alkaline substance is similar to this, and in the case of the above-defined water dosage, its specific molar ratio is as follows, and similarly when the inorganic alkaline substance is sodium hydroxide, its addition ratio can be appropriately adjusted to reduce, and its addition amount can control the pH of the final product at a relatively suitable value when it is in a more preferred range.

[0016] When the polyamine is triethylenetetramine, preferably, the molar ratio of triethylenetetramine, dimethyl sulfate and inorganic alkaline substance is 1:(10.0-11.0):(6.0-7.0); more preferably 1:(10.7-11.0):(6.6-7.0).

[0017] When the polyamine is tetraethylenepentamine, preferably, the molar ratio of the tetraethylenepentamine, dimethyl sulfate and inorganic alkaline substance is 1:(8.0-9.0):(7.0-8.0); more preferably 1:(8.4-8.7):(7.0-7.2).

[0018] When the polyamine is pentaethylenehexamine, preferably the molar ratio of pentaethylenehexamine, dimethyl sulfate and inorganic alkaline substance is 1:(10.0-11.0):(8.0-9.0); more preferably 1:(9.8-10.1):(8.0-8.2).

[0019] According to the preparation method of the present invention, preferably, the dimethyl sulfate is added dropwise into the reaction system; more preferably, the dimethyl sulfate is added dropwise into the reaction system under ice-water bath conditions, and after the addition is completed, the temperature is raised to 30-40° C. (more preferably 35-40° C.) and the reaction is carried out for 4h-7h.

[0020] The one-step preparation method of polyquaternary ammonium salt provided by the present invention is to directly react polyamine containing primary amine and secondary amine with dimethyl sulfate to generate polyquaternary ammonium salt by methylation reaction, and the required conditions are simple, the cost is low, the operation is simple, the yield is high, and no complicated post-treatment is required. The concentration of the obtained product can reach more than 25%, and the yield is more than 85%. The present invention is a product synthesis method specifically for a series of specific oilfield additives such as polyamines. The obtained product is directly an aqueous solution and can be directly used as an oilfield additive such as an oil displacement agent without post-treatment; it has the advantages of high economic value, no need to use expensive catalysts, and suitable for on-site operation.

[0021] The invention adopts a one-step method to quickly and efficiently synthesize a series of polyquaternary ammonium salts, and the raw materials are single, low in price, carbon-free, high in utilization rate, simple in operation, low in reaction temperature, and short in time, which is more conducive to the industrial production of polyquaternary ammonium salts and the application of polyquaternary ammonium salts as oilfield adjuvants such as oil displacement agents in oilfield development.

[0022] The polyquaternary ammonium salts synthesized by the present invention have higher chemical activity and stronger green environmental protection compared with traditional quaternary ammonium salts. They can interact with the negative charge on the surface / interface of oil reservoir minerals, and form a monolayer film by electrostatic self-assembly on the surface / interface of oil reservoir minerals at a lower concentration and in a shorter time, which can change the wettability of oil reservoir minerals, thereby improving the recovery rate of oil reservoirs. The polyquaternary ammonium salts have the functions of novel oil displacement agents and oilfield additives (such as clay stabilizers, anti-swelling agents, unblocking agents and bactericides, etc.), and their raw material sources are wide and low in cost, the use concentration is low and environmentally friendly, the displacement loss is small and the geological damage is small, and the construction process is simple and effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the infrared spectrum of octamethyldiethylenetriammonium trimethylsulfate obtained in Example 1.

[0024] Figure 2 This is the H NMR spectrum of octamethyldiethylenetriammonium trimethylsulfate obtained in Example 1.

[0025] Figure 3 This is the FT-IR spectrum of decamethyltriethylenetetraammonium obtained in Example 2.

[0026] Figure 4 This is the H NMR spectrum of decamethyltriethylenetetraammonium obtained in Example 2. DETAILED DESCRIPTION

[0027] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. It should be understood by those skilled in the art that the following specific description is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0028] All numerical specifications herein (e.g., temperature, time, concentration, and weight, etc., including ranges for each thereof) are generally approximate values ​​that may be appropriately varied (+) or (-) in increments of 0.1 or 1.0. All numerical specifications may be understood as being preceded by the term "about."

[0029] Example 1

[0030] This embodiment prepares diethylenetriammonium methyl sulfate, comprising the following steps:

[0031]

[0032] Take 1.05g (0.026mol) of sodium hydroxide and put it into a three-necked round-bottom flask. Add 9mL of deionized water and stir to dissolve. Take 1.04g (0.010mol) of diethylenetriamine and stir to dissolve. In a cold water bath, slowly stir and add 7.17g (0.047mol) of dimethyl sulfate. After the addition is completed, stir and react at 40°C for 5h to obtain a sample concentration of 26.7% and a yield of 88.6%.

[0033] Figure 1 The infrared spectrum of the obtained diethylenetriammonium methyl sulfate is shown in FIG. Figure 1 Medium, 3017cm -1 The peak at is CH3OSO3 - The CH stretching vibration absorption is due to the electron-withdrawing group OSO3 - The influence of 2961cm makes the absorption frequency larger; -1 、2851cm -1 The peaks at 3000-2800 cm-1 are the CH stretching vibration absorptions of methyl (-CH3) and methylene (-CH2-). -1 Absorption occurs in , so the compound is saturated; 1638cm -1 CC stretch vibration absorption, 1485cm -1 It is the CH bending vibration absorption (CH in-plane bending) of methyl (-CH3), 1278cm -1 The peak at 1258 cm is the CH bending vibration absorption (CH in-plane bending) of methylene (-CH2). -1 , 1218cm -1 It is OSO3 - S=O stretching vibration absorption, 1059cm -1 , 1030cm -1 It is CH3OSO3 - Medium CO stretching vibration absorption, 960cm -1 , 926cm -1 It is CN stretch vibration absorption, 759cm-1 , 619cm -1 and 577cm -1 It is CH3OSO3 - Absorption of SO stretching vibration.

[0034] Figure 2 This is the NMR spectrum of the obtained octamethyldiethylenetriammonium trimethylsulfate. Figure 2 According to the analysis of the chemical shift (δ value) and coupling splitting of protons in different environments, the substance has hydrogen nucleus information in five different environments, so the compound should have five groups of peaks. However, due to the small difference in the hydrogen chemical environment of the methylene in the compound, the peaks at δ3.98-3.99 could not be separated, so four groups of peaks appeared in the spectrum.

[0035] 1 H NMR (600MHz, D2O): δ = 3.20 (s, 18H, terminal-N-CH3), 3.26 (s, 6H, middle-N-CH3), 3.98-3.99 (m, 8H, CH2, undissolved), 3.63 (s, 9H, CH3OSO3 - ).

[0036] The content of C, H and N in the obtained octamethyldiethylenetriammonium trimethylsulfate was characterized by elemental analysis, and the results were as follows: 15 H 41 N3O 12 S3 element analysis results: calculated value (%), C: 32.66; H: 7.49; N: 7.62; measured value (%), C: 32.58; H: 7.46; N: 7.60. It can be seen that the content of C, H, and N elements is close to the calculated value, which indicates that the synthesized product is consistent with the target product.

[0037] The method used in this embodiment to detect the sample concentration is based on CN114137149A, which is as follows:

[0038] Weigh a certain amount of the sample (160 mg) with a 1 / 10000 balance and place it in a 50 mL beaker, add 5 mL of sodium acetate buffer solution with pH = 4.7, and then add 30 mL of 0.02 N sodium tetraphenylborate solution. After the precipitation is formed, leave it for 1 hour, filter the precipitation twice, until the filtrate is clear and has no turbidity. Wash the filter residue with distilled water for 3 times, combine the filtrate and the washing liquid, and put it in a 250 mL conical flask, add 10 mL of 0.1 N NaOH, add 2 drops of bromophenol blue indicator and 8 mL of chloroform, and titrate with 0.02 N tetrabutylammonium bromide. Until the chloroform layer changes from colorless and transparent to the beginning of light blue precipitation, and the water layer changes from light purple to blue.

[0039] The sample content is based on the formula:

[0040]

[0041] Where, c is the content of quaternary ammonium salt in the sample to be tested, 100%; N a is the molar concentration of sodium tetraphenylborate solution, mol / L; V a is the amount of sodium tetraphenylborate titrant used, mL; N b is the molar concentration of the active ingredient in the tetrabutylammonium bromide solution, mol / L; V b is the amount of tetrabutylammonium bromide solution used, mL; W is the mass of the water sample to be tested, g; n is the number of quaternary ammonium cations contained in each quaternary ammonium salt molecule.

[0042] The amount of tetrabutylammonium bromide solution used in this embodiment is 18.64 mL, and the quaternary ammonium salt content in the solution is calculated to be 26.7%. The sample concentrations in the subsequent embodiments are all measured using this method, so it will not be repeated here.

[0043] The following Table 1 explores the dosage of each raw material, and the reaction conditions and results are shown in Table 1:

[0044] Table 1 Diethylenetriamine reaction conditions and results

[0045]

[0046] It can be seen that when the amount of deionized water is fixed (the ratio of deionized water to polyamine is 8.3:1, in the range of (4.0-9.0):1.0), the molar ratio of diethylenetriamine, dimethyl sulfate and sodium hydroxide is close to 1: (5.3-5.6): (2.0-2.2), the obtained sample concentration and yield are greatly increased, and the sample concentration is suitable for the industrial standard concentration of more than 25%. At the same time, appropriately lowering the reaction temperature will not have a significant effect on the sample concentration. It is recommended that the reaction time be controlled to be more than 4 hours. The optimal temperature can be controlled in the range of 35°C to 40°C.

[0047] Comparative Example 1

[0048] This comparative example uses a two-step method to prepare diethylenetriammonium methyl sulfate with reference to CN105524606A, comprising the following steps:

[0049] 0.3 mol of diethylenetriamine was added to a reaction flask, deionized water was added, 2.7 mol of formic acid and 1.8 mol of formaldehyde were reacted in a cold water bath, the temperature was raised to 100°C, refluxed for 12 hours, cooled, 120 mL of 6 mol / L hydrochloric acid was added, and the solvent was removed by rotary evaporation. 130 mL of 10 mol / L NaOH solution was slowly added dropwise in a cold water bath, and the oil layer was separated by a separatory funnel to obtain the intermediate product pentamethyldiethylenetriamine. Secondly, it was reacted with 19 mL (0.2 mol) of dimethyl sulfate in N, N-dimethylformamide (DMF), the water bath was slowly heated to 60°C, and the temperature was kept for 1 hour. After the solid was washed with DMF and ethyl acetate and filtered, it was dried in a vacuum drying oven for 3 hours to obtain the product octamethyldiethylenetriammonium. The final sample was a crystalline solid with a total yield of 56.1%.

[0050] Comparative Example 1 The entire synthesis process is complicated. The two-step method requires first reacting diethylenetriamine with formaldehyde to generate an intermediate product, and then reacting with dimethyl sulfate to generate the final product. This process involves changes in multiple reagents, solvents and conditions, and requires precise control of parameters such as reaction temperature, time and pH value. The final product also requires complicated post-treatment, and the entire synthesis process takes 80-90 hours, while the one-step method only takes 4-7 hours.

[0051] By comparing the two synthesis methods of diethylenetriammonium methyl sulfate salt (Example 1 and Comparative Example 1), it can be seen that the method used in the present invention is simple to operate, the synthesis time is extremely short, and the product can be directly used as a commercial product. The one-step method of the present invention only requires direct reaction of diethylenetriamine and dimethyl sulfate under alkaline conditions, and no solvent or reagent needs to be changed during the reaction, nor does it require precise control of reaction parameters.

[0052] Example 2

[0053] This embodiment prepares triethylene tetraammonium methyl sulfate, comprising the following steps:

[0054]

[0055] Take 2.80g (0.070mol) of sodium hydroxide and put it into a three-necked round-bottom flask, add 8mL (the volume ratio with polyamine is 5.3:1) of deionized water and stir to dissolve, take 1.46g (0.010mol) of triethylenetetramine and stir to dissolve, under cold water bath conditions, slowly stir and add 13.87g (0.11mol) of dimethyl sulfate dropwise, after the addition is completed, stir and react at 40°C for 4h to obtain a sample concentration of 26.74% and a yield of 86.92%.

[0056] Table 2

[0057]

[0058] The molecular formula of the target product decamethyltriethylenetetraammonium is C 20 H 54 O 16 N4S4, the detected element percentage is shown in Table 2 above, where N% = 7.61% deviates from the theoretical value by 0.01%, C% = 32.43% deviates from the theoretical value by 0.26%, H% = 6.85% deviates from the theoretical value by 0.56%, and S% = 16.88% deviates from the theoretical value by 0.56%. The data error is very small.

[0059] The FT-IR spectrum of the product decamethyltriethylenetetramethyleneimine is as follows Figure 3 As shown. Figure 3 It can be seen that at 3474cm -1 The peak belongs to the -OH in the water produced by the product absorbing water, 2960cm -1 and 2851cm -1 The stretching vibration peaks of -CH3 and -CH2 are 1485 cm -1 The in-plane rocking vibration peak of -CH3 and -CH2 is 1465 cm -1 The absorption peak of 1256cm is the characteristic peak of quaternary ammonium salt CN. -1 It is the antisymmetric stretching of -SO4, 1064cm -1 It is the symmetric stretching of -SO4.

[0060] like Figure 4 As shown, the product is decamethyltriethylenetetramethylenetetramethylene 1 The H NMR detection data are δ3.32 (s, 18H, 6CH3), 3.41 (s, 18H, 4CH3), 3.76 (s, 12H, 4CH3), 4.14 (t, 12H, 4CH2), which are consistent with the theoretical structure.

[0061] Example 3

[0062] This embodiment prepares triethylene tetraammonium methyl sulfate, comprising the following steps:

[0063]

[0064] Take 2.80g (0.070mol) of sodium hydroxide and put it into a three-necked round-bottom flask, add 8mL (the volume ratio with polyamine is 5.3:1) of deionized water and stir to dissolve, take 1.46g (0.010mol) of triethylenetetramine and stir to dissolve, under cold water bath conditions, slowly stir and add 13.87g (0.11mol) of dimethyl sulfate, after adding, stir and react at 30°C for 6h to obtain a sample concentration of 25.12% and a yield of 84.65%.

[0065] When the volume ratio of water to polyamine is in the range of (4.0-9.0):1.0, the molar ratio of triethylenetetramine, dimethyl sulfate and alkali is preferably 1:(10.0-11.0):(6.0-7.0), which can meet the concentration of the obtained sample to meet the industrial standard of 25% or above; more preferably 1:(10.7-11.0):(6.6-7.0), and the yield is further improved. For example, in Examples 2 and 3, the molar ratio of triethylenetetramine, dimethyl sulfate and sodium hydroxide is 1:11:7, and the obtained sample concentrations are 26.74% and 25.12%, respectively, and the yields are 86.92% and 84.65%, respectively.

[0066] Example 4

[0067] This embodiment prepares tetraethylene pentaammonium methyl sulfate, comprising the following steps:

[0068]

[0069] Take 1.05g (0.026mol) of sodium hydroxide and put it into a three-necked round-bottom flask, add 4mL (the volume ratio with polyamine is 6.2:1) of deionized water and stir to dissolve, take 0.645g (0.0034mol) of tetraethylenepentamine and stir to dissolve, under cold water bath condition, slowly stir and add 3.65g (0.029mol) of dimethyl sulfate, after adding, stir and react at 38°C for 6.5h to obtain a sample concentration of 29.2% and a yield of 87.4%.

[0070] When the volume ratio of water to polyamine is in the range of (4.0-9.0):1.0, the molar ratio of tetraethylenepentamine, dimethyl sulfate, and alkali is preferably 1:(8.0-9.0):(7.0-8.0), which can meet the concentration of the obtained sample to be applicable to the industrial standard concentration of more than 25%; more preferably 1:(8.4-8.7):(7.0-7.2), the sample concentration and yield are further improved. For example, in this embodiment, the molar ratio of tetraethylenepentamine, dimethyl sulfate, and sodium hydroxide is 1:8.5:7.6, the obtained sample concentration is 29.2%, and the yield is 87.4%.

[0071] Example 5

[0072] The preparation of pentaethylene hexaammonium methyl sulfate in this embodiment comprises the following steps:

[0073]

[0074] Take 1.05g (0.026mol) of sodium hydroxide and put it into a three-necked round-bottom flask, add 6mL (the volume ratio with polyamine is 8.3:1) of deionized water and stir to dissolve, take 0.69g (0.0030mol) of pentaethylenehexamine and stir to dissolve, under cold water bath conditions, slowly stir and add 3.76g (0.030mol) of dimethyl sulfate, after the addition is completed, stir and react at 38°C for 6.5h to obtain a sample concentration of 25.0% and a yield of 87.0%.

[0075] When the volume ratio of water to polyamine is in the range of (4.0-9.0):1.0, the molar ratio of pentaethylene hexamine, dimethyl sulfate, and alkali is preferably 1:(10.0-11.0):(8.0-9.0), which can meet the concentration of the obtained sample to be applicable to the industrial standard concentration of more than 25%; more preferably 1:(9.8-10.1):(8.0-8.2), and the yield is further improved. In this embodiment, the molar ratio of tetraethylene pentamine, dimethyl sulfate, and sodium hydroxide is 1:10:8.7, the obtained sample concentration is 25.0%, and the yield is 87.0%.

[0076] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A one-step green synthesis method for preparing polyquaternary ammonium salts, characterized in that: The preparation method comprises the following steps: Mixing polyamine, inorganic alkaline substance and water, adding dimethyl sulfate thereto for reaction, and obtaining a solution of the polyquaternary ammonium salt after the reaction is completed; The polyamine is selected from one or a combination of two or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine; The inorganic alkaline substance is selected from sodium hydroxide; The polyamine is diethylenetriamine, and the molar ratio of diethylenetriamine, dimethyl sulfate and inorganic alkaline substance is 1:(5.0-6.0):(2.0-2.5); The polyamine is triethylenetetramine, and the molar ratio of triethylenetetramine, dimethyl sulfate and inorganic alkaline substance is 1:(10.0-11.0):(6.0-7.0); The polyamine is tetraethylenepentamine, and the molar ratio of tetraethylenepentamine, dimethyl sulfate and inorganic alkaline substance is 1:(8.0-9.0):(7.0-8.0); The polyamine is pentaethylenehexamine, and the molar ratio of pentaethylenehexamine, dimethyl sulfate and inorganic alkaline substance is 1:(10.0-11.0):(8.0-9.0); The volume ratio of water to polyamine is (4.0-9.0):1.

0.

2. The preparation method according to claim 1, characterized in that: The dimethyl sulfate is added dropwise into the reaction system under ice-water bath conditions, and after the addition is completed, the temperature is raised to 30-40° C. and reacted for 4-7 hours.

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