Perfluoroalkyl-substituted allyl quaternary ammonium salts and their preparation methods, copolymers and their preparation methods and applications, and wastewater treatment methods.

Abstract

This invention relates to the field of industrial wastewater treatment technology for natural gas purification, and discloses a perfluoroalkyl-substituted allyl quaternary ammonium salt and its preparation method, copolymer and its preparation method and application, and a method for treating wastewater. The quaternary ammonium salt has the structure shown in formula (1), wherein R1 and R2 are each independently selected from methyl or ethyl; n is an integer from 4 to 11. The quaternary ammonium salt is obtained through a nucleophilic substitution reaction between allyl amine or its derivative and a perfluoroalkyl haloalkane. The copolymer of this invention contains structural unit A from acrylamide and structural unit B from the quaternary ammonium salt, and is obtained through a polymerization reaction between acrylamide and the quaternary ammonium salt monomer. The copolymer of this invention has good salt resistance and strong hydrophobic association, and can be well adapted to the treatment of high-salt industrial wastewater or the removal of impurities in the field of natural gas purification.

Description

Technical Field

[0001] This invention relates to the field of natural gas purification industrial wastewater treatment technology, specifically to a perfluoroalkyl-substituted allyl quaternary ammonium salt and its preparation method, copolymers and their preparation methods and applications, and methods for treating wastewater. Background Technology

[0002] As my country actively promotes the green transformation of its energy structure, natural gas, as a green, efficient, and low-carbon fossil energy source, plays a crucial role. It is well known that high-salt organic industrial wastewater is generated during the exploration, development, production, gathering, transportation, and purification processes of sulfur-containing natural gas, shale gas, and tight gas. In particular, the vigorous development of deep and ultra-deep sulfur-containing natural gas in recent years has led to a continuous increase in the total production and discharge of high-salt organic wastewater from the natural gas industry. For example, the tail gas oxidation absorption process in natural gas purification plants has been gradually applied to natural gas purification. This process involves directly incinerating various sulfides in the tail gas of the sulfur recovery unit in the natural gas purification plant, converting them into SO2, and then using highly selective organic amines to absorb the SO2 after cooling. The organic amine absorption solution can be regenerated at high temperatures and recycled, while the regenerated high-concentration SO2 gas is returned to the sulfur recovery unit. However, the amine purification stage of this process generates and discharges large amounts of high-sulfate organic amine industrial wastewater, which urgently needs treatment.

[0003] Coagulation-flocculation is widely used in the treatment of industrial wastewater from natural gas purification. The key to this method lies in using a suitable flocculant. Organic polymers, inorganic flocculants, microbial flocculants, and composite flocculants are commonly used, with polyacrylamide polymer flocculants being the most widely researched and applied. However, for complex natural gas purification industrial wastewater with high sulfate and high organic amine content, conventional cationic polyacrylamide flocculants often fail to achieve good flocculation treatment results due to poor salt tolerance; they easily undergo molecular chain coiling under high salt conditions, losing their bridging ability. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of conventional cationic polyacrylamide flocculants in the prior art, such as poor salt resistance, easy molecular chain curling and loss of bridging ability under high salt conditions, and inability to achieve good flocculation treatment effect. This invention provides a perfluoroalkyl-substituted allyl quaternary ammonium salt and its preparation method, copolymer and its preparation method and application, and a method for treating wastewater.

[0005] To achieve the above objectives, a first aspect of the present invention provides a perfluoroalkyl-substituted allyl quaternary ammonium salt, wherein the quaternary ammonium salt has the structure shown in formula (1).

[0006] Formula (1), where R1 and R2 are independently selected from methyl or ethyl; n is an integer from 4 to 11.

[0007] A second aspect of the present invention provides a method for preparing a perfluoroalkyl-substituted allyl quaternary ammonium salt, wherein the method comprises: subjecting N,N-dimethylallylamine or N,N-diethylallylamine to a nucleophilic substitution reaction with a perfluoroalkyl halide to obtain the perfluoroalkyl-substituted allyl quaternary ammonium salt, wherein the molar ratio of N,N-dimethylallylamine or N,N-diethylallylamine to the perfluoroalkyl halide is 1:1.2-1.5.

[0008] A third aspect of the present invention provides a perfluoroalkyl-substituted allyl quaternary ammonium salt prepared by the preparation method provided in the second aspect of the present invention.

[0009] A fourth aspect of the present invention provides a copolymer comprising: a structural unit A derived from acrylamide and a structural unit B derived from a perfluoroalkyl-substituted allyl quaternary ammonium salt, wherein the perfluoroalkyl-substituted allyl quaternary ammonium salt is the perfluoroalkyl-substituted allyl quaternary ammonium salt of the present invention, and the molar ratio of structural unit A to structural unit B is 196-199:1-4.

[0010] The fifth aspect of the present invention provides a method for preparing a copolymer, wherein the method comprises: polymerizing acrylamide with a fluorinated cationic hydrophobic monomer in the presence of an initiator and a protective gas to obtain the copolymer.

[0011] The sixth aspect of the present invention provides a copolymer prepared by the preparation method provided in the fifth aspect of the present invention.

[0012] The seventh aspect of the present invention provides the application of the above-described copolymer as a flocculant in wastewater treatment.

[0013] Preferably, the wastewater is industrial wastewater from natural gas purification.

[0014] The eighth aspect of the present invention provides a method for treating industrial wastewater from natural gas purification, wherein a flocculant is added to the industrial wastewater from natural gas purification and stirred, wherein the industrial wastewater from natural gas purification is organic amine wastewater containing 1-4% sulfate.

[0015] Preferably, the flocculant is the copolymer described above.

[0016] Through the above technical solution, the copolymer of the present invention introduces a fluorinated cationic hydrophobic portion into polyacrylamide. Because the fluorinated hydrophobic groups can aggregate, the copolymer molecules in aqueous solution undergo intramolecular and intermolecular association under electrostatic, hydrogen bonding, or van der Waals forces, depending on the concentration. When the critical association concentration is reached, the copolymer molecules associate into aggregates, forming a huge three-dimensional network structure, significantly increasing the apparent viscosity of the solution. By introducing fluorinated hydrophobic groups, the flocculation time of the flocculant can be shortened, and the flocculation effect can be improved. The copolymer of the present invention was used as a flocculant, and its structural changes in the salt solution were compared with those of a conventional cationic polyacrylamide flocculant added to a 4% sodium sulfate solution. The results are as follows: Figure 1 , 2 As shown, from Figure 1 As can be seen, the copolymer of the present invention, when characterized by cryo-scanning electron microscopy in a 4% sodium sulfate solution, still retains a three-dimensional network structure, exhibiting a strong hydrophobic association effect and good bridging ability. Figure 2 It can be seen that conventional cationic polyacrylamide flocculants undergo molecular chain coiling under high salt conditions, forming a sheet-like solution structure, and their bridging ability is severely weakened. The copolymer flocculant of this invention and conventional cationic polyacrylamide flocculant were respectively used to treat simulated high-salt wastewater (containing 4% sodium sulfate) in diatomaceous earth suspension. The transmittance of the supernatant of the treated simulated high-salt wastewater was measured using a spectrophotometer. The flocculation treatment effects of the two flocculants on simulated high-salt wastewater within a certain concentration range were compared. The results are as follows. Figure 3 As shown, from Figure 3 It can be seen that the transmittance of the supernatant of the simulated high-salinity wastewater treated with the copolymer flocculant of this invention can reach over 93%, and when the concentration of the copolymer flocculant is 12 mg / L, the transmittance of the supernatant reaches a maximum of 99.75%. This is because the copolymer flocculant not only carries a positive charge that can neutralize the charge of the diatomaceous earth suspended matter and cause aggregation, but also has a strong hydrophobic association effect, with outstanding bridging ability under sulfate conditions, promoting the formation of large flocs, thereby better flocculating and settling the diatomaceous earth suspended matter in the simulated high-salinity wastewater; while using conventional cationic flocculants... The transmittance of the supernatant of the simulated high-salt wastewater treated with polyacrylamide flocculant was relatively poor. Moreover, the increase in transmittance of the supernatant was not significant with the increase in the dosage of conventional cationic polyacrylamide flocculant. This indicates that conventional cationic polyacrylamide flocculant is not effective in flocculating and removing diatomaceous earth suspended matter in simulated high-salt wastewater. This is because conventional cationic polyacrylamide flocculant undergoes molecular chain coiling under high salt conditions, with positive charges being embedded in the coiled molecular chains. At the same time, its bridging ability is also severely weakened, making it unable to effectively flocculate and settle diatomaceous earth suspended matter in simulated high-salt wastewater.

[0017] Furthermore, the perfluoroalkyl-substituted allyl quaternary ammonium salt synthesized in this invention as a fluorinated cationic hydrophobic monomer has surface activity and can be well dispersed in water. It does not require the addition of other small molecule surfactants to solubilize the hydrophobic monomer, thus avoiding the use of small molecule surfactants. The resulting copolymer is easy to process and will not cause environmental pollution. The copolymer of this invention is prepared by aqueous binary copolymerization, which is simple, easy to operate, and easy to control. The cationicity of the copolymer can be changed by directly adjusting the feeding ratio of the quaternary ammonium salt, without the need to introduce other cationic monomers. Attached Figure Description

[0018] Figure 1 This is a cryo-scanning electron microscope image of the copolymer obtained in Example 1-1 of the present invention in a 4% sodium sulfate solution;

[0019] Figure 2 This is a cryo-scanning electron microscope image of a commercially available cationic polyacrylamide flocculant in a 4% sodium sulfate solution.

[0020] Figure 3 The transmittance of the supernatant after flocculation and sedimentation of diatomaceous earth suspension simulating high-salt wastewater (containing 4% sodium sulfate) under different dosages of the copolymer prepared in Example 1-1 of this invention and commercially available conventional cationic polyacrylamide flocculant is measured. Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0023] A first aspect of the present invention provides a perfluoroalkyl-substituted allyl quaternary ammonium salt, wherein the quaternary ammonium salt has the structure shown in formula (1).

[0024] Formula (1), where R1 and R2 are independently selected from methyl or ethyl; n is an integer from 4 to 11.

[0025] According to the present invention, the quaternary ammonium salt has surface activity and can be well dispersed in water, eliminating the need for additional small molecule surfactants to solubilize it and avoiding the use of small molecule surfactants. The quaternary ammonium salt of the present invention is used as a fluorinated cationic hydrophobic monomer to polymerize with acrylamide, resulting in a copolymer that can be used as a flocculant in industrial wastewater treatment. On the one hand, because the quaternary ammonium salt of the present invention has surface activity, no additional small molecule surfactants are needed for solubilization during the polymerization process, making the resulting copolymer easy to process and preventing environmental pollution. On the other hand, the quaternary ammonium salt of the present invention contains fluorinated cations, and during the polymerization reaction with acrylamide, the cationicity of the copolymer can be directly changed by adjusting the feed ratio of the quaternary ammonium salt, without the need to introduce other cationic monomers.

[0026] According to the present invention, in the presence of an initiator, in order to enable the quaternary ammonium salt, as a fluorinated cationic hydrophobic monomer, to successfully polymerize with acrylamide and to give the resulting copolymer good salt resistance and good flocculation effect when treating industrial wastewater, preferably, the critical micelle concentration of the quaternary ammonium salt is 0.3-7 mmol / L.

[0027] According to the present invention, preferably, in formula (1), n ​​is 6, 7 or 9.

[0028] In this invention, the method for preparing the quaternary ammonium salt can be the preparation method provided in the second aspect of this invention.

[0029] In this invention, the composition and structure of the hydrophobic associative cationic flocculant can be determined by characterization methods such as infrared spectroscopy, or by the amount of each material fed during the preparation process.

[0030] A second aspect of the present invention provides a method for preparing a perfluoroalkyl-substituted allyl quaternary ammonium salt, wherein the method comprises: subjecting N,N-dimethylallylamine or N,N-diethylallylamine to a nucleophilic substitution reaction with a perfluoroalkyl halide to obtain the perfluoroalkyl-substituted allyl quaternary ammonium salt, wherein the molar ratio of allylamine or its derivative to the perfluoroalkyl halide is 1:1.2-1.5.

[0031] In some embodiments of the present invention, the molar ratio of N,N-dimethylallylamine to perfluoroalkyl iodoalkane is 1:1.3.

[0032] According to the present invention, the solvent for the nucleophilic substitution reaction is acetone and / or 1,4-dioxane.

[0033] In some embodiments of the present invention, the solvent for the nucleophilic substitution reaction is acetone.

[0034] According to the present invention, in order to carry out the nucleophilic substitution reaction completely and obtain the corresponding quaternary ammonium salt, preferably, the temperature of the nucleophilic substitution reaction is 35-55°C and the time is 6-24h.

[0035] More preferably, the nucleophilic substitution reaction is carried out at a temperature of 40-50°C for 8-12 hours.

[0036] In some embodiments of the present invention, the nucleophilic substitution reaction is carried out at a temperature of 40°C and a time of 12 hours.

[0037] According to the present invention, in order to enable the obtained copolymer to neutralize the charge and adsorb and bridge most of the negatively charged colloidal particles in the wastewater, and to be well adapted to the treatment of high-salt industrial wastewater or the removal of impurities in the field of natural gas purification, and to avoid the molecular chain roll-up of the flocculant copolymer molecules under high salt conditions and the weakening of the bridging ability, preferably, the perfluoroalkyl haloalkane is selected from one or more of perfluoroheptyl iodoalkane, perfluorooctyl iodoalkane, and perfluorodecyl iodoalkane.

[0038] In some embodiments of the present invention, the perfluoroalkyl iodide is perfluoroheptyl iodide, perfluorooctyl iodide, or perfluorodecyl iodide.

[0039] According to the present invention, after the nucleophilic substitution reaction is completed, the following post-treatment is performed: the solid powder product obtained from the nucleophilic substitution reaction is repeatedly washed with solvent and dried at a constant temperature to a constant weight.

[0040] In some embodiments of the present invention, after the nucleophilic substitution reaction is completed, the washing solvent is diethyl ether, and the drying temperature is 35°C.

[0041] A third aspect of the present invention provides a perfluoroalkyl-substituted allyl quaternary ammonium salt obtained by the preparation method described in the present invention.

[0042] A fourth aspect of the present invention provides a copolymer comprising: a structural unit A derived from acrylamide and a structural unit B derived from a perfluoroalkyl-substituted allyl quaternary ammonium salt, wherein the perfluoroalkyl-substituted allyl quaternary ammonium salt is the perfluoroalkyl-substituted allyl quaternary ammonium salt of the present invention, and the molar ratio of structural unit A to structural unit B is 196-199:1-4.

[0043] Preferably, the molar ratio of structural unit A to structural unit B is 197-199:1-3.

[0044] According to the present invention, in order to enable the copolymer to neutralize and adsorb bridging most of the negatively charged colloidal particles in the wastewater, and to be well adapted to the treatment of high-salt industrial wastewater or the removal of impurities in the field of natural gas purification, and to avoid molecular chain roll-up and weakening of bridging ability of the flocculant copolymer molecules under high salt conditions, preferably, structural unit A in the copolymer molecule has the structure shown in formula (2), and structural unit B has the structure shown in formula (3).

[0045] Equation (2), Formula (3), wherein R1 and R2 are independently selected from methyl or ethyl; n is an integer from 4 to 11; preferably, n is 6, 7 or 9.

[0046] In some embodiments of the present invention, the molar ratio of structural unit A to structural unit B is 197:3, 989:11, 1989:11, 199:1, 247:3, 1983:17, 4971:29, 989:11, 1987:11 or 497:3, and any value within the range formed by any two of the above values.

[0047] In some embodiments of the present invention, R1 and R2 are independently selected from methyl groups, and n is 6, 7 or 9 respectively.

[0048] According to the present invention, in order to enable the association effect to play a significant role in the bridging ability of the polymer flocculant, preferably, the weight-average molecular weight of the copolymer is 2 × 10⁻⁶. 6 -6.5×10 6 g / mol, with a critical association concentration of 0.1-0.3%.

[0049] In some embodiments of the present invention, the weight-average molecular weight of the copolymer is 6.5 × 10⁻⁶. 6 g / mol, 4×10 6 g / mol, 3.5×10 6 g / mol, 3×10 6 g / mol, 5×10 6 g / mol, 2×10 6 g / mol, 5.5×10 6 g / mol or 1×10 6 g / mol, and any value within the range formed by any two of the above values; the critical association concentration is 0.1%, 0.21%, 0.25%, 0.28%, 0.13%, 0.18% or 0.3%, and any value within the range formed by any two of the above values.

[0050] The copolymer of this invention introduces a fluorinated cationic hydrophobic portion into polyacrylamide. Because the fluorinated hydrophobic groups can aggregate, the polymer molecules in aqueous solution undergo intramolecular and intermolecular association under electrostatic, hydrogen bonding, or van der Waals forces, depending on the concentration. When a critical association concentration is reached, the copolymer molecules associate into aggregates, forming a large three-dimensional network structure, significantly increasing the apparent viscosity of the solution. Introducing fluorinated hydrophobic groups can shorten the flocculation time of the flocculant and improve the flocculation effect. The polymer of this invention was added as a flocculant to a 4% sodium sulfate solution, and the structural changes of the flocculant in the salt solution were observed. The results are as follows: Figure 1 As shown, from Figure 1 It can be seen that the copolymer flocculant still has a three-dimensional network structure in 4% sodium sulfate solution, exhibiting a strong hydrophobic association effect and good bridging ability.

[0051] In this invention, the copolymer can be prepared using the preparation method provided in the fifth aspect of this invention.

[0052] In this invention, the composition and structure of the copolymer can be determined by characterization methods such as infrared spectroscopy, or by the amount of each material fed during the preparation process.

[0053] The fifth aspect of the present invention provides a method for preparing a copolymer, wherein the method comprises: polymerizing acrylamide with a fluorinated cationic hydrophobic monomer in the presence of an initiator and a protective gas to obtain the copolymer.

[0054] According to the present invention, the solution for the polymerization reaction is an aqueous solution, and the solvent used is deionized water.

[0055] Preferably, acrylamide and fluorinated cationic hydrophobic monomers are used as solutes, and the mass fraction of the solutes in the polymerization reaction solution is controlled at 20-25%.

[0056] In some embodiments of the present invention, acrylamide and a fluorinated cationic hydrophobic monomer are used as solutes, and the mass fraction of the solutes in the polymerization reaction solution is 25%, 23%, 22% or 20%, and any value within the range formed by any two of the above values.

[0057] According to the preparation method of the present invention, in order to facilitate the polymerization reaction and obtain the copolymer, preferably, the initiator is selected from one or more of sodium persulfate, sodium sulfite, and azobisisobutyramidine hydrochloride; wherein, based on the total weight of acrylamide and fluorinated cationic hydrophobic monomer, the mass percentage of the initiator is 0.05-0.4% by weight.

[0058] Preferably, the initiator has a mass percentage of 0.1-0.3% by weight.

[0059] In some embodiments of the present invention, the initiator is a composite initiator consisting of sodium persulfate, sodium sulfite, and azobisisobutyramidine hydrochloride in a mass ratio of 2:1:7.

[0060] In some embodiments of the present invention, the initiator is 0.3%, 0.2% or 0.1% by mass, or any value within the range formed by any two of the above values.

[0061] According to the preparation method of the present invention, in order to enable the obtained copolymer to neutralize and adsorb and bridge most of the negatively charged colloidal particles in the wastewater when used as a flocculant, and to be well adapted to the treatment of high-salt industrial wastewater or the removal of impurities in the field of natural gas purification, and to avoid the molecular chain roll-up of the flocculant polymer molecules under high salt conditions, which weakens the bridging ability, preferably, the fluorinated cationic hydrophobic monomer is the above-mentioned perfluoroalkyl-substituted allyl quaternary ammonium salt.

[0062] According to the preparation method of the present invention, in order to improve the water solubility of the copolymer, preferably, the molar ratio of acrylamide to the fluorinated cationic hydrophobic monomer is 100:0.5-2.5;

[0063] More preferably, the molar ratio of acrylamide to the fluorinated cationic hydrophobic monomer is 100:0.7-2.

[0064] In some embodiments of the present invention, the molar ratio of acrylamide to the fluorinated cationic hydrophobic monomer is 100:2, 100:1.5, 100:1 or 100:0.7, and any value within the range formed by any two of the above values.

[0065] According to the preparation method of the present invention, in order to ensure the smooth progress of the polymerization reaction and obtain the copolymer, preferably, the polymerization reaction temperature is 45-55°C and the time is 4-8 hours;

[0066] Preferably, the polymerization reaction is carried out at a temperature of 45-50°C for 5-7 hours.

[0067] In some embodiments of the present invention, the polymerization reaction temperature is 50°C or 45°C, and the polymerization reaction time is 5 or 7 hours.

[0068] According to the preparation method of the present invention, in order to ensure that the polymerization initiation system is at a suitable pH to facilitate the polymerization reaction, preferably, the pH of the polymerization reaction solution is adjusted to 6-9 using sodium hydroxide. More preferably, the pH of the polymerization reaction solution is adjusted to 7-8 using sodium hydroxide.

[0069] In some embodiments of the present invention, the pH of the polymerization reaction solution is 7 or 8.

[0070] According to the preparation method of the present invention, after the polymerization reaction is completed, the following post-processing is performed: the reaction product is washed multiple times with a solvent, the washed product is placed in a vacuum oven to dry to constant weight, and then ground into powder.

[0071] Preferably, the washing solvent is ethanol, and the vacuum drying temperature is 55°C.

[0072] In some embodiments of the present invention, the fluorinated cationic hydrophobic monomers are perfluoroheptyldimethylallylammonium iodide, perfluorooctyldimethylallylammonium iodide, or perfluorodecyldimethylallylammonium iodide.

[0073] The copolymer described above can be obtained through the preparation method provided in the fifth aspect of this invention. According to the above description, when the polymer of this invention is applied as a flocculant in industrial wastewater treatment, the copolymer molecules themselves carry a positive charge, which can neutralize the negatively charged colloidal particles in the industrial wastewater, causing aggregation. Furthermore, the fluorinated hydrophobic groups inside the copolymer molecules easily aggregate in aqueous solution, exhibiting a strong hydrophobic association effect and outstanding bridging ability under sulfate conditions, promoting the formation of large flocs, thereby better flocculating and settling suspended solids in high-salt wastewater. In addition, the fluorinated cationic hydrophobic monomer synthesized in this invention has surface activity and can be well dispersed in water, eliminating the need for additional small-molecule surfactants to solubilize the hydrophobic monomer, thus avoiding the use of small-molecule surfactants. The resulting copolymer is easy to post-process and does not cause environmental pollution. The copolymer of this invention is prepared using an aqueous solution binary copolymerization method, which is simple, easy to operate, and easy to control. The cationicity of the copolymer can be directly changed by adjusting the proportion of the fluorinated cationic hydrophobic monomer in the monomer composition, without the need to introduce other cationic monomers.

[0074] The sixth aspect of the present invention provides a copolymer prepared by the preparation method provided in the fifth aspect of the present invention.

[0075] The seventh aspect of the present invention provides the application of the above-described polymer as a flocculant in wastewater treatment.

[0076] Preferably, the wastewater is industrial wastewater from natural gas purification.

[0077] The eighth aspect of the present invention provides a method for treating industrial wastewater from natural gas purification, wherein a flocculant is added to the industrial wastewater from natural gas purification and stirred, wherein the industrial wastewater from natural gas purification is organic amine wastewater containing 1-4% sulfate.

[0078] Preferably, the flocculant is the copolymer described above.

[0079] Using the copolymer of the present invention as a flocculant, flocculation treatment was performed on diatomaceous earth suspension simulating high-salt wastewater (containing 4% sodium sulfate). The transmittance of the supernatant of the treated simulated high-salt wastewater was measured using a spectrophotometer. The flocculation results are as follows: Figure 3 As shown, from Figure 3 It can be seen that, under the same experimental conditions, compared with conventional cationic polyacrylamide flocculants, the transmittance of the supernatant of simulated high-salt wastewater treated with the copolymer of the present invention can reach more than 93%, and when the copolymer concentration is 12 mg / L, the transmittance of the supernatant reaches a maximum of 99.75%. In contrast, the transmittance of the supernatant of simulated high-salt wastewater treated with conventional cationic polyacrylamide flocculants is relatively poor, and the increase in transmittance of the supernatant is not significant with the increase in the dosage of conventional cationic polyacrylamide flocculants.

[0080] The following examples illustrate the technical solution of the present invention. All raw materials and reagents used are commercially available, and room temperature refers to 15-35℃.

[0081] N,N-Dimethylallylamine, 98% purity, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0082] N,N-Diethylallylamine, with a purity greater than 98%, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0083] Perfluoroheptyl iodide, with a purity greater than 98%, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0084] Perfluorooctyl iodide, 98% purity, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0085] Perfluorodecyl iodoane, 98% purity, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0086] Sodium persulfate, analytical grade, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0087] Sodium sulfite, analytical grade, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0088] Azobisisobutyramidine hydrochloride, 97% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0089] Conventional cationic polyacrylamide flocculant, industrial grade purity, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0090] The structure and composition of perfluoroalkyl-substituted allyl quaternary ammonium salts were determined by infrared spectroscopy.

[0091] The structure and composition of copolymer molecules are determined by the amount of each material fed during the preparation process.

[0092] The weight-average molecular weight of the copolymer molecules was determined by gel permeation chromatography.

[0093] The apparent viscosity (or other physicochemical properties) of the copolymer molecules was determined using a Brookfield DV-II rotational viscometer.

[0094] Example 1

[0095] (1) Preparation of the fluorine-containing cationic hydrophobic monomer perfluoroheptyldimethylallylammonium iodide:

[0096] 1 mol of N,N-dimethylallylamine was dissolved in 3 mol of acetone and transferred to a three-necked flask. The mixture was heated to 40 °C with stirring, and then 1.3 mol of perfluoroheptyl iodide was added dropwise to the three-necked flask. After the addition was complete, the mixture was stirred and reacted for 12 hours. The product was then filtered to obtain a solid powder. The product was washed three times with diethyl ether and filtered again to obtain a washed solid powder. Finally, the washed solid powder was dried to constant weight in a 35 °C oven to obtain the target product I, perfluoroheptyldimethylallyl ammonium iodide.

[0097] The surface tension of target product I was measured, and the critical micelle concentration of target product I was found to be 7 mmol / L.

[0098] (2) Preparation of copolymer I:

[0099] Deionized water was added to the polymerization reactor. Under stirring, perfluoroheptyldimethylallylammonium iodide and acrylamide obtained in step (1) were added in sequence, and the mass fraction of the solute and the pH of the solution were controlled. Nitrogen gas was then introduced for 30 minutes and the solution was heated. Then, a composite initiator with a mass ratio of sodium persulfate, sodium sulfite and azobisisobutyramidine hydrochloride of 2:1:7 was added. Polymerization reaction was carried out. The obtained product was washed with ethanol several times, dried in a vacuum oven at 55°C to constant weight, and ground into powder to obtain copolymer I.

[0100] The weight-average molecular weight of copolymer I was determined by gel permeation chromatography, and the results are shown in Table 1.

[0101] By adjusting the reaction conditions in Example 1 (2), copolymers I-1, I-2, I-3, and I-4 can be obtained. The reaction conditions and the composition and physicochemical properties of the corresponding copolymers are shown in Table 1.

[0102] Table 1

[0103]

[0104] Example 2

[0105] (1) Preparation of the fluorine-containing cationic hydrophobic monomer perfluorooctyl dimethyl allyl ammonium iodide:

[0106] 1 mol of N,N-dimethylallylamine was dissolved in 3 mol of acetone and transferred to a three-necked flask. The mixture was heated to 40°C with stirring, and then 1.3 mol of perfluorooctyl iodide was added dropwise to the three-necked flask. After the addition was complete, the mixture was stirred and reacted for 12 hours. The product was then filtered to obtain a solid powder. The product was washed three times with diethyl ether and filtered again to obtain a washed solid powder. Finally, the washed solid powder was dried to constant weight in a 35°C oven to obtain the target product II, perfluorooctyldimethylallyl ammonium iodide.

[0107] The surface tension of target product II was measured, and the critical micelle concentration of target product II was found to be 2.5 mmol / L.

[0108] (2) Preparation of copolymer II:

[0109] Deionized water was added to the polymerization reactor. Under stirring, perfluorooctyl dimethyl allyl ammonium iodide and acrylamide obtained in step (1) were added in sequence, and the mass fraction of the solute and the pH of the solution were controlled. Nitrogen gas was then introduced for 30 minutes and the solution was heated. Then, a composite initiator with a mass ratio of sodium persulfate, sodium sulfite and azobisisobutyramidine hydrochloride of 2:1:7 was added. Polymerization reaction was carried out. The obtained product was washed with ethanol several times, dried in a vacuum oven at 55°C to constant weight, and ground into powder to obtain copolymer II.

[0110] The weight-average molecular weight of copolymer II was determined by gel permeation chromatography, and the results are shown in Table 2.

[0111] By adjusting the reaction conditions in Example 2 (2), copolymers II-1, II-2, II-3, and II-4 can be obtained. The reaction conditions and the composition and physicochemical properties of the corresponding copolymers are shown in Table 2.

[0112] Table 2

[0113]

[0114] Example 3

[0115] (1) Preparation of the fluorine-containing cationic hydrophobic monomer perfluorodecyldimethylallylammonium iodide:

[0116] 1 mol of N,N-dimethylallylamine was dissolved in 3 mol of acetone and transferred to a three-necked flask. The mixture was heated to 40 °C with stirring, and then 1.3 mol of perfluorodecyl iodide was added dropwise to the three-necked flask. After the addition was complete, the mixture was stirred and reacted for 12 hours. The product was then filtered to obtain a solid powder. The product was washed three times with diethyl ether and filtered again to obtain a washed solid powder. Finally, the washed solid powder was dried to constant weight in a constant temperature drying oven at 35 °C to obtain the target product III, perfluorodecyldimethylallyl ammonium iodide.

[0117] The surface tension of target product III was measured, and the critical micelle concentration of target product III was found to be 0.3 mmol / L.

[0118] (2) Preparation of copolymer III:

[0119] Deionized water was added to the polymerization reactor. Under stirring, perfluorodecyl dimethylallyl ammonium iodide and acrylamide obtained in step (1) were added in sequence, and the mass fraction of the solute and the pH of the solution were controlled. Nitrogen gas was then introduced for 30 minutes and the solution was heated. Then, a composite initiator with a mass ratio of sodium persulfate, sodium sulfite and azobisisobutyramidine hydrochloride of 2:1:7 was added. Polymerization reaction was carried out. The obtained product was washed with ethanol several times, dried in a vacuum oven at 55°C to constant weight, and ground into powder to obtain the copolymer III.

[0120] The weight-average molecular weight of copolymer III was determined by gel permeation chromatography, and the results are shown in Table 2.

[0121] By adjusting the reaction conditions in Example 3(2), copolymers III-1, III-2, III-3, and III-4 can be obtained. The reaction conditions and the composition and physicochemical properties of the corresponding copolymers are shown in Table 3.

[0122] Table 3

[0123]

[0124] Test Example 1

[0125] The copolymer I-1 obtained in Example 1-1 of this invention and a conventional cationic polyacrylamide flocculant were added to a 4% sodium sulfate solution, respectively. The structure of the copolymer molecules in the solution was determined by cryo-scanning electron microscopy. The results are as follows: Figure 1 and Figure 2 As shown. From Figure 1 It can be seen that the copolymer of the present invention has a three-dimensional network structure in a 4% sodium sulfate solution, exhibiting a strong hydrophobic association effect and good bridging ability. Figure 2It can be seen that conventional cationic polyacrylamide flocculants undergo molecular chain coiling under high salt conditions, forming a sheet-like solution structure, and their bridging ability is severely weakened.

[0126] Test Example 2

[0127] At 25°C, copolymer I-1 obtained in Example 1-1 was used as a flocculant, and added separately to diatomaceous earth suspension simulating high-salt wastewater (containing 4% sodium sulfate) along with conventional cationic polyacrylamide flocculant. This yielded treated solutions containing different mass concentrations of flocculants. After thorough stirring and standing for a period of time, the supernatant was collected, and its transmittance was measured using a spectrophotometer to evaluate the flocculation effect of each flocculant. The results are as follows: Figure 3 As shown.

[0128] from Figure 3 It can be seen that the transmittance of the supernatant of the simulated high-salinity wastewater treated with the copolymer of the present invention can reach over 93%, and when the concentration of the copolymer flocculant of the present invention is 12 mg / L, the transmittance of the supernatant reaches a maximum of 99.75%. This is because the copolymer flocculant of the present invention not only carries a positive charge that can neutralize the charge of the diatomaceous earth suspended matter and cause aggregation, but also has a strong hydrophobic association effect, with outstanding bridging ability under sulfate conditions, promoting the formation of large flocs, thereby better flocculating and settling the diatomaceous earth suspended matter in the simulated high-salinity wastewater; while using conventional cationic flocculants... The transmittance of the supernatant of the simulated high-salt wastewater treated with conventional cationic polyacrylamide flocculant was relatively poor. Moreover, the increase in transmittance of the supernatant was not significant with the increase in the dosage of conventional cationic polyacrylamide flocculant. This indicates that conventional cationic polyacrylamide flocculant is not effective in flocculating and removing diatomaceous earth suspended matter in simulated high-salt wastewater. This is because conventional cationic polyacrylamide flocculant undergoes molecular chain coiling under high salt conditions, with positive charges being embedded in the coiled molecular chains. At the same time, its bridging ability is also severely weakened, and it cannot effectively flocculate and settle diatomaceous earth suspended matter in simulated high-salt wastewater.

[0129] As can be seen from the above embodiments and test examples, the copolymer of the present invention still retains a three-dimensional network structure under high salt conditions. When applied to the treatment of high-salt industrial wastewater or the removal of impurities in the field of natural gas purification, the copolymer of the present invention not only carries a positive charge that can neutralize the charge of diatomaceous earth suspensions and cause aggregation, but also exhibits a strong hydrophobic association effect and has good bridging ability. In addition, the fluorinated cationic hydrophobic monomer synthesized by the present invention has surface activity and can be well dispersed in water. It does not require the addition of other small molecule surfactants to solubilize the hydrophobic monomer, thus avoiding the use of small molecule surfactants. The resulting copolymer is easy to post-process and will not cause environmental pollution. The copolymer of the present invention is prepared by aqueous solution binary copolymerization, which is simple, easy to operate, and easy to control. The cationicity of the copolymer can be changed directly by adjusting the proportion of fluorinated cationic hydrophobic monomers in the monomer composition, without the need to introduce other cationic monomers.

[0130] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various specific technical features in any suitable manner. However, these simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A process for the preparation of a perfluoroalkyl-substituted allyl quaternary ammonium salt, characterized in that, The method comprises: subjecting N,N-dimethylallylamine or N,N-diethylallylamine to a nucleophilic substitution reaction with a perfluoroalkyl halogen alkane to obtain the perfluoroalkyl-substituted allyl quaternary ammonium salt, wherein the molar ratio of N,N-dimethylallylamine or N,N-diethylallylamine to the perfluoroalkyl halogen alkane is 1:1.2-1.

5. The perfluoroalkyl halogen alkane is selected from one or more of perfluoroheptyl iodine alkane, perfluoroctyl iodine alkane, and perfluorodecyl iodine alkane.

2. The production method according to claim 1, wherein The nucleophilic substitution reaction is carried out at a temperature of 35-55°C for 6-24h.

3. The production method according to claim 2, wherein, The nucleophilic substitution reaction is carried out at a temperature of 40-50°C for 8-12h.

4. A perfluoroalkyl-substituted allyl quaternary ammonium salt obtained by the preparation method of any one of claims 1-3.

5. A copolymer characterized in that, The copolymer comprises: structural unit A from acrylamide and structural unit B from the perfluoroalkyl-substituted allyl quaternary ammonium salt, wherein the perfluoroalkyl-substituted allyl quaternary ammonium salt is the perfluoroalkyl-substituted allyl quaternary ammonium salt of claim 4, and the molar ratio of the structural unit A to the structural unit B is 196-199:1-4.

6. The copolymer of claim 5, wherein, The molar ratio of the structural unit A to the structural unit B is 197-199:1-3.

7. The copolymer of claim 5 or 6, wherein, The weight average molecular weight of the copolymer is 2 x 10 6 -6.5 x 10 6 g / mol, and the critical associating concentration is 0.1-0.3%.

8. A process for the preparation of a copolymer, characterized in that, The method comprises: subjecting acrylamide to a polymerization reaction with a fluorine-containing cationic hydrophobic monomer in the presence of an initiator and a protective gas to obtain the copolymer; wherein the fluorine-containing cationic hydrophobic monomer is the perfluoroalkyl-substituted allyl quaternary ammonium salt of claim 4.

9. The production method according to claim 8, wherein The initiator is selected from one or more of sodium persulfate, sodium sulfite, and azobisdimethylaminoformamide hydrochloride. And / or, the mass percentage of the initiator is 0.05-0.4% by weight based on the total weight of acrylamide and the fluorine-containing cationic hydrophobic monomer.

10. The production method according to claim 9, wherein The mass percentage of the initiator is 0.1-0.3% by weight based on the total weight of acrylamide and the fluorine-containing cationic hydrophobic monomer.

11. The method of making according to any one of claims 8-10, wherein, The molar ratio of acrylamide to the fluorine-containing cationic hydrophobic monomer is 100:0.5-2.

5.

12. The method of making according to claim 11, wherein, The molar ratio of acrylamide to the fluorine-containing cationic hydrophobic monomer is 100:0.7-2.

13. The method of making according to claim 11, wherein, The polymerization reaction is carried out at a temperature of 40-55°C for 4-8h. And / or, the pH of the polymerization reaction is 6-9.

14. The production method according to claim 13, wherein The polymerization reaction is carried out at a temperature of 45-50°C for 5-7h. And / or, the pH of the polymerization reaction is 7-8.

15. The method of making according to any one of claims 8-10, 12, wherein, The polymerization reaction is carried out at a temperature of 40-55°C for 4-8h. And / or, the pH of the polymerization reaction is 6-9.

16. The method of manufacturing according to claim 15, wherein, The polymerization reaction is carried out at a temperature of 45-50°C for 5-7h. And / or, the pH of the polymerization reaction is 7-8.

17. A copolymer obtained by the preparation method of any one of claims 8-16.

18. Use of the copolymer of any one of claims 5-7 and 17 as a flocculant in wastewater treatment.

19. Use according to claim 18, wherein, The wastewater is natural gas purification industrial wastewater.

20. A method of treating natural gas sweetening industrial wastewater, characterized by, The flocculant is mixed with the natural gas purification industrial wastewater, wherein the natural gas purification industrial wastewater contains 1-4% of organic amine wastewater containing sulfates. The flocculant is mixed with the natural gas purification industrial wastewater, wherein the natural gas purification industrial wastewater contains 1-4% of organic amine wastewater containing sulfates. The flocculant is a copolymer according to any one of claims 6 to 8 and 13. The flocculant is a copolymer according to any one of claims 6 to 8 and 13.

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