Perfluoroalkyl-substituted allyl quaternary ammonium salt and preparation method therefor, copolymer as well as preparation method therefor and use thereof, and wastewater treatment method

Abstract

The present invention relates to the technical field of industrial wastewater treatment in natural gas purification, and disclosed are a perfluoroalkyl-substituted allyl quaternary ammonium salt and a preparation method therefor, a copolymer as well as a preparation method therefor and a use thereof, and a wastewater treatment method. The quaternary ammonium salt has a structure represented by formula (1), wherein R1 and R2 are each independently selected from methyl or ethyl; and n is an integer from 4 to 11. The quaternary ammonium salt is obtained by a nucleophilic substitution reaction between allylamine or a derivative thereof and perfluoroalkyl halide. The copolymer of the present invention contains a structural unit A from acrylamide and a structural unit B from the quaternary ammonium salt, and is obtained by a polymerization reaction between the acrylamide and the quaternary ammonium salt monomer. The copolymer of the present invention has relatively good salt resistance and relatively strong hydrophobic association, and can be well adapted to high-salinity industrial wastewater treatment or impurity removal in the field of natural gas purification.

Description

Perfluoroalkyl-substituted allyl quaternary ammonium salt and preparation method, copolymer and preparation method and application, and method for treating wastewater

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application No. 202311252219.6 filed on September 26, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of natural gas purification industrial wastewater treatment, and in particular to a perfluoroalkyl-substituted allyl quaternary ammonium salt and a preparation method thereof, a copolymer and a preparation method and application thereof, and a wastewater treatment method. Background Art

[0004] As my country actively promotes a green transformation of its energy mix, natural gas, as a green, efficient, and low-carbon fossil energy source, plays a crucial role. It's well known that the exploration, development, production, gathering, transportation, and purification and processing of sour natural gas, shale gas, and tight gas generate high-salinity organic industrial wastewater. In particular, the vigorous development of sour natural gas from deep and ultra-deep formations in recent years has led to a continuous increase in the total volume of high-salinity organic wastewater produced by the natural gas industry. For example, the oxidation absorption process for off-gas from natural gas purification plants has been gradually applied to natural gas purification. This process directly incinerates various sulfides in the off-gas from the sulfur recovery unit of a natural gas purification plant, converting them into SO2. After cooling, the SO2 is absorbed using highly selective organic amines. 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 liquid purification stage of this process generates a large amount of high-sulfate organic amine industrial wastewater, which urgently needs treatment.

[0005] Coagulation-flocculation is widely used in the treatment of industrial wastewater from natural gas purification. The key to this method lies in the use of an appropriate flocculant. Organic polymer, inorganic, microbial, and composite flocculants are among the most commonly used, with polyacrylamide polymer flocculants being the most widely researched and applied. However, for the complex composition of high-sulfate and high-organic amine natural gas purification industrial wastewater, conventional cationic polyacrylamide flocculants often suffer from poor salt tolerance. In high-salinity conditions, their molecular chains tend to curl, losing their bridging ability and failing to achieve effective flocculation treatment results.

[0006] Summary of the Invention

[0007] The purpose of the present invention is to overcome the problems of poor salt tolerance of conventional cationic polyacrylamide flocculants in the prior art, which are prone to molecular chain curling and loss of bridging ability under high salt conditions, and are unable to achieve a good flocculation treatment effect. The present invention provides a perfluoroalkyl-substituted allyl quaternary ammonium salt and a preparation method, a copolymer and a preparation method and application thereof, and a method for treating wastewater.

[0008] In order to achieve the above object, the first aspect of the present invention provides a perfluoroalkyl-substituted allyl quaternary ammonium salt, wherein the quaternary ammonium salt has a structure shown in formula (1),

[0009] Wherein, R1 and R2 are independently selected from methyl or ethyl; n is an integer of 4-11.

[0010] 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.

[0011] The third aspect of the present invention provides a perfluoroalkyl-substituted allyl quaternary ammonium salt prepared by the preparation method provided by the second aspect of the present invention.

[0012] The fourth aspect of the present invention provides a copolymer, wherein the copolymer comprises: 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 described in the present invention, and the molar ratio of the structural unit A:structural unit B is 196-199:1-4.

[0013] A fifth aspect of the present invention provides a method for preparing a copolymer, wherein the method comprises: polymerizing acrylamide and a fluorine-containing cationic hydrophobic monomer in the presence of an initiator and a protective gas to obtain the copolymer.

[0014] The sixth aspect of the present invention provides a copolymer prepared by the preparation method provided by the fifth aspect of the present invention.

[0015] A seventh aspect of the present invention provides use of the above copolymer as a flocculant in wastewater treatment.

[0016] Preferably, the wastewater is natural gas purification industrial wastewater.

[0017] An eighth aspect of the present invention provides a method for treating natural gas purification industrial wastewater, wherein a flocculant is added to the natural gas purification industrial wastewater and stirred;

[0018] Wherein, the flocculant is the above-mentioned copolymer.

[0019] Preferably, the natural gas purification industrial wastewater is organic amine wastewater containing 1-4% sulfate.

[0020] Through the above technical solution, the copolymer of the present invention introduces a fluorinated cationic hydrophobic moiety into polyacrylamide. Because the fluorinated hydrophobic groups can aggregate, the copolymer molecules of the present invention, depending on their concentration, undergo intramolecular and intermolecular association under the action of electrostatic, hydrogen bonding, or van der Waals forces. When the 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. The introduction of fluorinated hydrophobic groups can shorten the flocculation time of the flocculant and improve the flocculation effect. The copolymer of the present invention was used as a flocculant, and a conventional cationic polyacrylamide flocculant was added to a 4% sodium sulfate solution, respectively. The structural changes of the two flocculants in the salt solution were compared. The results are shown in Figures 1 and 2. As can be seen from Figure 1, the copolymer of the present invention still has a three-dimensional network structure in a 4% sodium sulfate solution, as characterized by cryo-scanning electron microscopy, showing a strong hydrophobic association effect and good bridging ability. However, as can be seen from Figure 2, the conventional cationic polyacrylamide flocculant undergoes molecular chain curling under high salt conditions, forming a sheet-like solution structure, and its bridging ability is seriously weakened. The copolymer flocculant of the present invention and the conventional cationic polyacrylamide flocculant were respectively used in the treatment of diatomite suspension simulated high-salt wastewater (containing 4% sodium sulfate), and the transmittance of the supernatant of the simulated high-salt wastewater after treatment was measured by spectrophotometer. The flocculation treatment effects of the two flocculants on the simulated high-salt wastewater were compared within a certain addition concentration range. The results are shown in FIG3 . As can be seen from FIG3 , the transmittance of the supernatant of the simulated high-salt wastewater treated with the copolymer flocculant of the present invention can reach more than 93%, and when the addition 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 has a positive charge that can neutralize the charge of the diatomite suspension and cause polymerization, but also has a strong The hydrophobic association effect of the conventional cationic polyacrylamide flocculant is outstanding in the presence of sulfate, which promotes the formation of large flocs, thereby better flocculating and settling the diatomaceous earth suspended solids in the simulated high-salt wastewater; while the night light transmittance of the supernatant of the simulated high-salt wastewater treated with the conventional cationic polyacrylamide flocculant is relatively poor, and with the increase in the dosage of the conventional cationic polyacrylamide flocculant, the increase in the supernatant transmittance is not large, indicating that the conventional cationic polyacrylamide flocculant has a poor flocculation and removal effect on the diatomaceous earth suspended solids in the simulated high-salt wastewater. This is because the conventional cationic polyacrylamide flocculant undergoes molecular chain curling under high salt conditions, and the positive charge is embedded in the curled molecular chain. At the same time, the bridging ability is also severely weakened, and it cannot flocculate and settle the diatomaceous earth suspended solids in the simulated high-salt wastewater well.

[0021] In addition, the perfluoroalkyl-substituted allyl quaternary ammonium salt synthesized as a fluorine-containing cationic hydrophobic monomer of the present invention has surface activity and can be well dispersed in water. No other small molecule surfactant is needed to solubilize the hydrophobic monomer, thus avoiding the use of small molecule surfactants. The obtained copolymer is easy to post-process and does not cause environmental pollution. The copolymer of the present invention is prepared by a binary copolymerization method in aqueous solution, which has a simple preparation process, is easy to operate, and is convenient to control. The cationicity of the copolymer can be changed by directly adjusting the feeding ratio of the quaternary ammonium salt without introducing other cationic monomers. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG1 is a cryo-scanning electron micrograph of the copolymer obtained in Example 1-1 of the present invention in a 4% sodium sulfate solution;

[0023] FIG2 is a cryo-scanning electron micrograph of a commercially available cationic polyacrylamide flocculant in a 4% sodium sulfate solution;

[0024] FIG3 shows the transmittance of the supernatant after flocculation and sedimentation of a diatomaceous earth suspension simulating high-salt wastewater (containing 4% sodium sulfate) at different dosages of the copolymer prepared in Example 1-1 of the present invention and a commercially available conventional cationic polyacrylamide flocculant. DETAILED DESCRIPTION

[0025] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0026] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0027] The first aspect of the present invention provides a perfluoroalkyl-substituted allyl quaternary ammonium salt, wherein the quaternary ammonium salt has a structure shown in formula (1),

[0028] Wherein, R1 and R2 are independently selected from methyl or ethyl; n is an integer of 4-11.

[0029] According to the present invention, described quaternary ammonium salt has surface activity, can be well dispersed in water, does not need to add other small-molecule surfactants to solubilize quaternary ammonium salt, avoids the use of small-molecule surfactant.Using quaternary ammonium salt of the present invention as fluorine-containing cation hydrophobic monomer and acrylamide to carry out polyreaction, obtain in industrial waste water treatment as multipolymer of flocculant, on the one hand, because quaternary ammonium salt of the present invention has surface activity, does not need to add other small-molecule surfactants to solubilize in the polyreaction process, makes the multipolymer aftertreatment obtained easy and can not pollute the environment; On the other hand, quaternary ammonium salt of the present invention contains fluorine-containing cation, when carrying out polyreaction with acrylamide, can directly change the cationic degree of multipolymer by adjusting the charging ratio of quaternary ammonium salt, does not need to introduce other cationic monomers.

[0030] According to the present invention, in order to enable the quaternary ammonium salt as a fluorine-containing cationic hydrophobic monomer to smoothly undergo polymerization with acrylamide only in the presence of an initiator, and to enable the obtained copolymer to have 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.

[0031] According to the present invention, preferably, in formula (1), n ​​is 6, 7 or 9.

[0032] In the present invention, the method for preparing the quaternary ammonium salt can adopt the preparation method provided by the second aspect of the present invention.

[0033] In the present invention, the composition and structure of the hydrophobically associating cationic flocculant can be determined by characterization means such as infrared spectroscopy, or by the feeding amount of each material during the preparation process.

[0034] 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.

[0035] In some embodiments of the present invention, the molar ratio of N,N-dimethylallylamine to perfluoroalkyl iodide is 1:1.3.

[0036] According to the present invention, the solvent for the nucleophilic substitution reaction is acetone and / or 1,4-dioxane.

[0037] In some embodiments of the present invention, the solvent for the nucleophilic substitution reaction is acetone.

[0038] According to the present invention, in order to allow the nucleophilic substitution reaction to proceed completely and obtain the corresponding quaternary ammonium salt, preferably, the temperature of the nucleophilic substitution reaction is 35-55° C. and the time is 6-24 hours.

[0039] More preferably, the temperature of the nucleophilic substitution reaction is 40-50° C., and the time is 8-12 h.

[0040] In some embodiments of the present invention, the temperature of the nucleophilic substitution reaction is 40° C. and the time is 12 h.

[0041] According to the present invention, in order to make the prepared copolymer undergo electrical neutralization, adsorption and bridging effects with most negatively charged colloidal particles in wastewater, and to be well adapted to the treatment of high-salt industrial wastewater or removal of impurities in the field of natural gas purification, and to avoid molecular chain coiling of the flocculant copolymer molecules under high salt conditions and weakening of the bridging ability, preferably, the perfluoroalkyl halide is selected from one or more of perfluoroheptyl iodide, perfluorooctyl iodide, and perfluorodecyl iodide.

[0042] In some embodiments of the present invention, the perfluoroalkyl iodide is perfluoroheptyl iodide, perfluorooctyl iodide or perfluorodecyl iodide.

[0043] According to the present invention, after the nucleophilic substitution reaction is completed, the following post-treatment is further performed: the solid powder product obtained by the nucleophilic substitution reaction is repeatedly washed with a solvent, and dried at a constant temperature to a constant weight.

[0044] 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.

[0045] The third aspect of the present invention provides a perfluoroalkyl-substituted allyl quaternary ammonium salt obtained by the preparation method of the present invention.

[0046] The fourth aspect of the present invention provides a copolymer, wherein the copolymer comprises: 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 described in the present invention, and the molar ratio of the structural unit A:structural unit B is 196-199:1-4.

[0047] Preferably, the molar ratio of the structural unit A:structural unit B is 197-199:1-3.

[0048] According to the present invention, in order to make the copolymer react with most of the negatively charged colloidal particles in the wastewater to generate electrical neutralization, adsorption and bridging, and be well adapted to the treatment of high-salt industrial wastewater or removal of impurities in the field of natural gas purification, and to avoid molecular chain coiling of the flocculant copolymer molecules under high salt conditions and weakening of the bridging ability, preferably, the structural unit A in the copolymer molecule has the structure shown in formula (2), and the structural unit B has the structure shown in formula (3).

[0049] Wherein, R1 and R2 are independently selected from methyl or ethyl; n is an integer of 4-11; preferably, n is 6, 7 or 9.

[0050] In some embodiments of the present invention, the molar ratio of structural unit A: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.

[0051] In some embodiments of the present invention, R1 and R2 are independently selected from methyl, and n is 6, 7 or 9. According to the present invention, in order to make the associative effect 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 -6.5×10 6 g / mol, and the critical association concentration is 0.1-0.3%.

[0052] In some embodiments of the present invention, the weight average molecular weight of the copolymer is 6.5×10 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.

[0053] The copolymer of the present invention introduces a fluorinated cationic hydrophobic moiety into polyacrylamide. Because the fluorinated hydrophobic groups can aggregate, the polymer molecules of the present invention, depending on their concentration, undergo intramolecular and intermolecular association under the action of electrostatic, hydrogen bonding, or van der Waals forces. When the critical association concentration is reached, the copolymer molecules associate into aggregate structures, forming a large three-dimensional network structure, which significantly increases the apparent viscosity of the solution. By introducing the fluorinated hydrophobic groups, the flocculation time of the flocculant can be shortened and the flocculation effect can be improved. The polymer of the present 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 shown in Figure 1. As can be seen from Figure 1, the copolymer flocculant still has a three-dimensional network structure in the 4% sodium sulfate solution, exhibiting a strong hydrophobic association effect and good bridging ability.

[0054] In the present invention, the method for preparing the copolymer can adopt the preparation method provided in the fifth aspect of the present invention.

[0055] In the present invention, the composition and structure of the copolymer can be determined by characterization means such as infrared spectroscopy, or by the amount of each material added during the preparation process.

[0056] A fifth aspect of the present invention provides a method for preparing a copolymer, wherein the method comprises: polymerizing acrylamide and a fluorine-containing cationic hydrophobic monomer in the presence of an initiator and a protective gas to obtain the copolymer.

[0057] According to the present invention, the solution for the polymerization reaction is an aqueous solution, and the solvent used is deionized water.

[0058] Preferably, acrylamide and fluorine-containing cationic hydrophobic monomer are used as solutes, and the mass fraction of the solutes in the polymerization reaction solution is controlled at 20-25%.

[0059] In some embodiments of the present invention, acrylamide and a fluorine-containing cationic hydrophobic monomer are used as solutes, and the mass fractions of the solutes in the polymerization reaction solution are 25%, 23%, 22% or 20%, respectively, and any value within the range formed by any two of the above values.

[0060] According to the preparation method of the present invention, in order to smoothly carry out the polymerization reaction to obtain the copolymer, preferably, the initiator is selected from one or more of sodium persulfate, sodium sulfite, and azobisisobutylamidine hydrochloride; wherein the mass percentage of the initiator is 0.05-0.4 weight% based on the total weight of acrylamide and the fluorine-containing cationic hydrophobic monomer.

[0061] Preferably, the mass percentage of the initiator is 0.1-0.3 wt %.

[0062] In some embodiments of the present invention, the initiator is a composite initiator in which the mass ratio of sodium persulfate, sodium sulfite and azobisisobutylamidine hydrochloride is 2:1:7.

[0063] In some embodiments of the present invention, the mass percentage of the initiator is 0.3%, 0.2% or 0.1%, or any value within the range formed by any two of the above values.

[0064] According to the preparation method of the present invention, in order to enable the prepared copolymer to be used as a flocculant to undergo electrical neutralization, adsorption and bridging effects on the majority of negatively charged colloidal particles in wastewater, and to be well adapted to the treatment of high-salt industrial wastewater or removal of impurities in the field of natural gas purification, and to avoid molecular chain coiling of flocculant polymer molecules under high salt conditions and weakening of bridging ability, preferably, the fluorine-containing cationic hydrophobic monomer is the above-mentioned perfluoroalkyl-substituted allyl quaternary ammonium salt.

[0065] According to the preparation method of the present invention, in order to make the copolymer have better water solubility, preferably, the molar ratio of acrylamide to the fluorine-containing cationic hydrophobic monomer is 100:0.5-2.5;

[0066] More preferably, the molar ratio of acrylamide to the fluorine-containing cationic hydrophobic monomer is 100:0.7-2.

[0067] In some embodiments of the present invention, the molar ratio of acrylamide to the fluorine-containing cationic hydrophobic monomer is 100:2, 100:1.5, 100:1 or 100:0.7, or any value within the range formed by any two of the above values.

[0068] According to the preparation method of the present invention, in order to make the polymerization reaction proceed smoothly to obtain the copolymer, preferably, the polymerization reaction temperature is 45-55° C. and the time is 4-8 hours.

[0069] Preferably, the polymerization reaction temperature is 45-50° C. and the time is 5-7 hours.

[0070] In some embodiments of the present invention, the polymerization reaction temperature is 50° C. or 45° C., and the polymerization reaction time is 5 h or 7 h.

[0071] According to the preparation method of the present invention, in order to make the polymerization initiation system at an appropriate pH to facilitate the polymerization reaction, preferably, the pH of the polymerization reaction solution is adjusted to 6-9 using sodium hydroxide. Preferably, the pH of the polymerization reaction solution is adjusted to 7-8 using sodium hydroxide.

[0072] In some embodiments of the present invention, the pH of the polymerization reaction solution is 7 or 8.

[0073] According to the preparation method of the present invention, after the polymerization reaction is completed, the following post-treatment is further performed: the reaction product is washed multiple times with a solvent, the washed product is placed in a vacuum oven and dried to a constant weight, and then ground into powder.

[0074] Preferably, the washing solvent is ethanol, and the vacuum drying temperature is 55°C.

[0075] In some embodiments of the present invention, the fluorine-containing cationic hydrophobic monomer is perfluoroheptyldimethylallylammonium iodide, perfluorooctyldimethylallylammonium iodide or perfluorodecyldimethylallylammonium iodide.

[0076] By the preparation method provided by the fifth aspect of the present invention, the above-mentioned copolymer can be obtained. According to the above statement, when the polymer of the present invention is used as a flocculant in industrial wastewater treatment, since the copolymer molecules themselves carry a positive charge, they can neutralize the negatively charged colloidal particles in the industrial wastewater and cause polymerization; and the fluorine-containing hydrophobic groups inside the copolymer molecules are easy to aggregate in aqueous solution, with a strong hydrophobic association effect and outstanding bridging ability under sulfate, which promotes the formation of large flocs, thereby better flocculating and settling suspended matter in high-salt wastewater. In addition, the fluorine-containing 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 pollute the environment. The preparation of the copolymer of the present invention adopts the method of binary copolymerization in aqueous solution, which has a simple preparation process, is easy to operate, and is easy to control. The cationic degree of the copolymer can be changed directly by adjusting the ratio of the fluorine-containing cationic hydrophobic monomer in the monomer composition, without the need to introduce other cationic monomers.

[0077] The sixth aspect of the present invention provides a copolymer prepared by the preparation method provided by the fifth aspect of the present invention.

[0078] A seventh aspect of the present invention provides use of the above polymer as a flocculant in wastewater treatment.

[0079] Preferably, the wastewater is natural gas purification industrial wastewater.

[0080] An eighth aspect of the present invention provides a method for treating natural gas purification industrial wastewater, wherein a flocculant is added to the natural gas purification industrial wastewater and stirred, wherein the flocculant is the above-mentioned copolymer.

[0081] Preferably, the natural gas purification industrial wastewater is organic amine wastewater containing 1-4% sulfate.

[0082] The copolymer of the present invention was used as a flocculant to carry out flocculation treatment of diatomaceous earth suspension-simulated high-salt wastewater (containing 4% sodium sulfate). The light transmittance of the supernatant of the treated simulated high-salt wastewater was measured by spectrophotometer. The flocculation results are shown in FIG3 . As can be seen from FIG3 , under the same experimental conditions, compared with the conventional cationic polyacrylamide flocculant, the light transmittance of the supernatant of the simulated high-salt wastewater treated with the copolymer of the present invention can reach more than 93%, and when the copolymer addition concentration is 12 mg / L, the light transmittance of the supernatant reaches a maximum of 99.75%. However, the light transmittance of the supernatant of the simulated high-salt wastewater treated with the conventional cationic polyacrylamide flocculant is relatively poor, and the increase in the light transmittance of the supernatant is not significant as the dosage of the conventional cationic polyacrylamide flocculant increases.

[0083] The following examples are used to illustrate the technical solutions of the present invention, wherein the raw materials and reagents used are commercially available, and room temperature refers to 15-35°C.

[0084] N,N-dimethylallylamine, purity 98%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0085] N,N-diethylallylamine, purity greater than 98%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0086] Perfluoroheptyliodide, purity greater than 98%, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0087] Perfluorooctyl iodide, purity 98%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0088] Perfluorodecyl iodide, purity 98%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0089] Sodium persulfate, analytical grade, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0090] Sodium sulfite (analytical grade) was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0091] Azobisisobutylamidine hydrochloride, purity 97%, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0092] Conventional cationic polyacrylamide flocculant, industrial grade purity, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0093] The structures and compositions of the perfluoroalkyl-substituted allyl quaternary ammonium salts were determined by infrared spectroscopy.

[0094] The structure and composition of the copolymer molecules are determined by the feeding amount of each material during the preparation process.

[0095] The weight average molecular weight of the copolymer molecules was determined by gel permeation chromatography.

[0096] The apparent viscosity (or other physicochemical performance parameters) of the copolymer molecules was measured using a Brookfield DV-II rotational viscometer.

[0097] Example 1

[0098] (1) Preparation of fluorine-containing cationic hydrophobic monomer perfluoroheptyldimethylallylammonium iodide:

[0099] 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 reacted with stirring for 12 hours, and a solid powder product was obtained by filtration; the product was repeatedly washed three times with ether and filtered to obtain a washed solid powder product; and the washed solid powder product was finally dried in a constant temperature drying oven at 35°C to constant weight to obtain the target product I perfluoroheptyldimethylallylammonium iodide.

[0100] The surface tension of the target product I was measured, and the critical micelle concentration of the target product I was found to be 7 mmol / L.

[0101] (2) Preparation of copolymer I:

[0102] Deionized water is added to a polymerization reaction kettle, and perfluoroheptyldimethylallylammonium iodide and acrylamide prepared in step (1) are added in sequence under stirring, and the mass fraction of the solute and the pH of the solution are controlled; nitrogen is then introduced for 30 minutes, and the solution is heated; a composite initiator of sodium persulfate, sodium sulfite and azobisisobutylamidine hydrochloride in a mass ratio of 2:1:7 is then added; a polymerization reaction is carried out; the obtained product is washed with ethanol several times, placed in a vacuum oven at 55°C and dried to constant weight, and ground into powder to obtain the copolymer I.

[0103] The weight average molecular weight of the copolymer I was obtained by gel permeation chromatography (GPC). The results are shown in Table 1.

[0104] 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 compositions and physicochemical properties of the corresponding copolymers are shown in Table 1:

[0105] Table 1

[0106] Example 2

[0107] (1) Preparation of fluorine-containing cationic hydrophobic monomer perfluorooctyl dimethyl allyl ammonium iodide:

[0108] 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 while 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 reacted with stirring for 12 hours and filtered to obtain a solid powder product; the product was repeatedly washed three times with ether and filtered to obtain a washed solid powder product; finally, the washed solid powder product was dried in a constant temperature drying oven at 35°C to constant weight to obtain the target product II perfluorooctyl dimethylallylammonium iodide.

[0109] The surface tension of target product II was measured, and the critical micelle concentration of target product II was 2.5 mmol / L.

[0110] (2) Preparation of copolymer II:

[0111] Deionized water is added to a polymerization reaction kettle, and perfluorooctyldimethylallylammonium iodide and acrylamide prepared in step (1) are added in sequence under stirring, and the mass fraction of the solute and the pH of the solution are controlled; nitrogen is then introduced for 30 minutes, and the solution is heated; a composite initiator of sodium persulfate, sodium sulfite and azobisisobutylamidine hydrochloride in a mass ratio of 2:1:7 is then added; a polymerization reaction is carried out; the obtained product is washed with ethanol several times, placed in a vacuum oven at 55°C and dried to constant weight, and ground into powder to obtain the copolymer II.

[0112] The weight average molecular weight of the copolymer II was obtained by gel permeation chromatography. The results are shown in Table 2.

[0113] 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 compositions and physicochemical properties of the corresponding copolymers are shown in Table 2:

[0114] Table 2

[0115] Example 3

[0116] (1) Preparation of fluorine-containing cationic hydrophobic monomer perfluorodecyldimethylallylammonium iodide:

[0117] 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 reacted with stirring for 12 hours and filtered to obtain a solid powder product; the product was repeatedly washed three times with ether and filtered to obtain a washed solid powder product; and the washed solid powder product was finally dried in a constant temperature drying oven at 35°C to constant weight to obtain the target product III perfluorodecyl dimethylallylammonium iodide.

[0118] The surface tension of the target product III was measured, and the critical micelle concentration of the target product III was found to be 0.3 mmol / L.

[0119] (2) Preparation of copolymer III:

[0120] Deionized water is added to a polymerization reaction kettle, and perfluorodecyldimethylallylammonium iodide and acrylamide prepared in step (1) are added in sequence under stirring, and the mass fraction of the solute and the pH of the solution are controlled; nitrogen is then introduced for 30 minutes, and the solution is heated; a composite initiator of sodium persulfate, sodium sulfite and azobisisobutylamidine hydrochloride in a mass ratio of 2:1:7 is then added; a polymerization reaction is carried out; the obtained product is washed with ethanol several times, placed in a vacuum oven at 55°C and dried to constant weight, and ground into powder to obtain the copolymer III.

[0121] The weight average molecular weight of the copolymer III was obtained by gel permeation chromatography. The results are shown in Table 2.

[0122] 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 compositions and physicochemical properties of the corresponding copolymers are shown in Table 3:

[0123] Table 3

[0124] Test Example 1

[0125] Copolymer I-1 prepared in Example 1-1 of the present invention and a conventional cationic polyacrylamide flocculant were added to a 4% sodium sulfate solution, and the molecular structure of the copolymer in solution was determined by cryo-scanning electron microscopy. The results are shown in Figures 1 and 2. As can be seen from Figure 1, 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. However, as can be seen from Figure 2, the conventional cationic polyacrylamide flocculant undergoes molecular chain curling in the presence of high salt, forming a sheet-like solution structure, and its bridging ability is severely weakened.

[0126] Test Example 2

[0127] At 25°C, copolymer I-1 prepared in Example 1-1 was added as a flocculant, and a conventional cationic polyacrylamide flocculant was added to a diatomaceous earth suspension simulating high-salt wastewater (containing 4% sodium sulfate), respectively, to obtain treated solutions containing different mass concentrations of flocculants. After being fully stirred and allowed to stand for a period of time, the supernatant was collected and the transmittance of the supernatant was measured using a spectrophotometer to evaluate the flocculation effect of each flocculant. The results are shown in Figure 3.

[0128] As can be seen from FIG3 , the transmittance of the supernatant of the simulated high-salinity wastewater treated with the copolymer of the present invention can reach more than 93%, and when the addition 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 has a positive charge that can neutralize the charge of the diatomaceous earth suspension and cause aggregation, but also has a strong hydrophobic association effect and outstanding bridging ability under sulfate, which promotes the formation of large flocs, thereby better flocculating and settling the diatomaceous earth suspension in the simulated high-salinity wastewater; while the conventional positive ions The night light transmittance of the supernatant of the simulated high-salt wastewater after treatment with the ionic polyacrylamide flocculant is relatively poor, and with the increase in the dosage of the conventional cationic polyacrylamide flocculant, the increase in the supernatant light transmittance is not large, indicating that the conventional cationic polyacrylamide flocculant has a poor flocculation and removal effect on the diatomaceous earth suspended matter in the simulated high-salt wastewater. This is because the conventional cationic polyacrylamide flocculant undergoes molecular chain curling under high salt conditions, and the positive charge is embedded in the curled molecular chain. At the same time, the bridging ability is also severely weakened, and it cannot flocculate and settle the diatomaceous earth suspended matter in the simulated high-salt wastewater well.

[0129] It can be seen from the above embodiments and test examples that the copolymer of the present invention still has 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 undergo polymerization, but also exhibits a strong hydrophobic association effect and has good bridging ability. In addition, the fluorine-containing 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 does not cause pollution to the environment. The preparation of the copolymer of the present invention adopts a binary copolymerization method of aqueous solution. The preparation process is simple, easy to operate, and easy to control. The cationicity of the copolymer can be changed directly by adjusting the proportion of the fluorine-containing cationic hydrophobic monomer in the monomer composition, without the need to introduce other cationic monomers.

[0130] The preferred embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the specific technical features in any appropriate manner. However, these simple variations and combinations should also be regarded as the contents disclosed by the present invention and fall within the scope of protection of the present invention.

Claims

1. A perfluoroalkyl-substituted allyl quaternary ammonium salt, characterized in that: The quaternary ammonium salt has a structure shown in formula (1), Wherein, R1 and R2 are each independently selected from methyl or ethyl; and n is an integer of 4-11.

2. The quaternary ammonium salt according to claim 1, wherein The critical micelle concentration of the quaternary ammonium salt is 0.3-7 mmol / L; Preferably, n is 6, 7 or 9.

3. A method for preparing 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 halide to obtain the perfluoroalkyl-substituted allyl quaternary ammonium salt, wherein the molar ratio of the N,N-dimethylallylamine or N,N-diethylallylamine to the perfluoroalkyl halide is 1:1.2-1.

5.

4. The preparation method according to claim 3, wherein The temperature of the nucleophilic substitution reaction is 35-55°C and the time is 6-24h; Preferably, the temperature of the nucleophilic substitution reaction is 40-50°C and the time is 8-12h; And / or, the perfluoroalkyl halide is selected from one or more of perfluoroheptyl iodide, perfluorooctyl iodide and perfluorodecyl iodide.

5. A perfluoroalkyl-substituted allyl quaternary ammonium salt obtained by the preparation method according to claim 3 or 4.

6. A copolymer, characterized in that The copolymer comprises: 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 according to any one of claims 1-2 and 5, and the molar ratio of the structural unit A:structural unit B is 196-199:1-4.

7. The copolymer according to claim 6, wherein The structural unit A has a structure shown in formula (2), and the structural unit B has a structure shown in formula (3), wherein R1 and R2 are each independently selected from methyl or ethyl; n is an integer of 4-11, preferably 6, 7 or 9; Preferably, the molar ratio of the structural unit A:structural unit B is 197-199:1-3.

8. The copolymer according to claim 6 or 7, wherein The weight average molecular weight of the copolymer is 2×10 6 -6.5×10 6 g / mol, and the critical association concentration is 0.1-0.3%.

9. A method for preparing a copolymer, characterized in that: The method comprises: in the presence of an initiator and a protective gas, polymerizing acrylamide and a fluorine-containing cationic hydrophobic monomer to obtain the copolymer; wherein the fluorine-containing cationic hydrophobic monomer is the perfluoroalkyl-substituted allyl quaternary ammonium salt described in any one of claims 1-2 and 5.

10. The preparation method according to claim 9, wherein: The initiator is selected from one or more of sodium persulfate, sodium sulfite, and azobisisobutyramidine hydrochloride; And / or, based on the total weight of acrylamide and the fluorine-containing cationic hydrophobic monomer, the mass percentage of the initiator is 0.05-0.4 weight %, preferably 0.1-0.3 weight %.

11. The preparation method according to claim 9 or 10, wherein: The molar ratio of acrylamide to the fluorine-containing cationic hydrophobic monomer is 100:0.5-2.5, preferably 100:0.7-2.

12. The preparation method according to claims 9-11, wherein: The polymerization reaction temperature is 40-55°C and the time is 4-8h, preferably the polymerization reaction temperature is 45-50°C and the time is 5-7h; And / or, the pH of the polymerization reaction is 6-9, preferably 7-8.

13. A copolymer obtained by the preparation method according to any one of claims 9 to 12.

14. Use of the copolymer according to any one of claims 6 to 8 and 13 as a flocculant in wastewater treatment.

15. The use according to claim 14, wherein: The waste water is natural gas purification industrial waste water.

16. A method for treating natural gas purification industrial wastewater, characterized in that: Mixing flocculants with natural gas purification industrial wastewater; Wherein, the flocculant is the copolymer described in any one of claims 6-8 and 13.

17. The method according to claim 16, wherein: The natural gas purification industrial wastewater contains 1-4% of sulfate organic amine wastewater.

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