CN114957543B

CN114957543B - Reverse demulsifier and preparation method thereof

Info

Publication number: CN114957543B
Application number: CN202210386180.6A
Authority: CN
Inventors: 任小丽; 段明; 方申文; 张潇月; 王淇海
Original assignee: Southwest Petroleum University
Current assignee: Southwest Petroleum University
Priority date: 2022-07-01
Filing date: 2022-07-01
Publication date: 2023-07-07
Anticipated expiration: 2042-07-01
Also published as: CN114957543A

Abstract

The invention provides a reverse demulsifier and a preparation method thereof, and relates to the technical field of demulsifiers. The reverse demulsifier is prepared by the following steps: firstly, modifying purine by adopting 5-bromo-1-pentene, then performing emulsion polymerization on unsaturated quaternary ammonium salt monomer and modified purine monomer under the condition of adding anionic emulsifier, and after polymerization, adding acrylic ester monomer for further modification to finally obtain the reverse demulsifier. The reverse demulsifier prepared by the invention has the characteristics of high deoiling rate, small dosage and the like, and the use method is simple, does not need complex equipment and procedures, and is suitable for industrial popularization.

Description

Reverse demulsifier and preparation method thereof

Technical Field

The invention belongs to the technical field of demulsifiers, and particularly relates to a reverse demulsifier and a preparation method thereof.

Background

At present, most of the oil fields in China enter the middle and later stages of water injection exploitation, the output of the oil field produced liquid is larger and larger, the water content of part of the produced liquid is up to 80-90%, and the demulsification treatment of the produced liquid is more and more difficult. And the treatment of the oilfield produced fluid is one of the important conditions for guaranteeing the normal exploitation of the oilfield. The domestic independent research and development of various reverse demulsifiers is difficult to meet the treatment requirement of produced liquid, and the low-water oil content after demulsification is high, so that the cost and difficulty of a sewage treatment system are increased.

Disclosure of Invention

In order to solve at least one of the problems, the invention provides a novel preparation method of the reverse demulsifier and the demulsifier prepared by the method, wherein the method is simple, raw materials are easy to obtain, and the reverse demulsifier has the characteristics of high deoiling rate, small dosage and the like.

The technical scheme of the invention is as follows: a method of preparing a reverse demulsifier comprising the steps of:

s1, modification of purine: adding equimolar amount of purine and potassium carbonate into a solvent, wherein 1-1.5 g of purine is added into each 10ml of solvent, then reacting for 1h at 70-90 ℃, then dropwise adding 5-bromo-1-pentene with equimolar amount of purine, cooling the reaction solution to room temperature after reacting for 24h, filtering, and purifying to obtain modified purine, wherein the purine is one of guanine and adenine; the process mainly comprises the steps of reacting secondary amine in purine with alkyl halide, and grafting pentene capable of participating in subsequent reaction onto purine ring;

s2, synthesizing a reverse demulsifier: adding an unsaturated quaternary ammonium salt monomer and a modified purine monomer with the mass ratio of 4-8:1 into water, deoxidizing, then adding an anionic emulsifier and hydrochloric acid, uniformly mixing, wherein the molar ratio of the hydrochloric acid to the modified purine monomer is 1:1, and then performing emulsion polymerization under the action of an initiator for 4-10 h, wherein the total mass concentration of the two monomers is not less than 45%; cooling to 20-35 ℃ after polymerization, adding acrylic ester monomers and alkali for neutralizing hydrochloric acid, adding water to ensure that the total mass concentration of the reaction monomers is not less than 20%, and continuously reacting for 12-24 hours at 20-35 ℃ to obtain the modified purine monomers and the acrylic ester monomers, wherein the molar ratio of the modified purine monomers to the acrylic ester monomers is 1:0.3-1.2.

In S2, the term "a base for neutralizing the hydrochloric acid" means that the added base is capable of completely neutralizing the hydrochloric acid added in the previous step, and the base used in the process is usually an inorganic base such as sodium hydroxide, potassium hydroxide, sodium carbonate, etc.

In S1, the specific operations of filtering and purifying are as follows: filtering the reacted product, collecting filtrate, regulating pH of the filtrate to 1-2, freezing for 12h at-4-0 ℃, filtering, placing the filtered solid phase into petroleum ether, regulating pH of petroleum ether solution to be neutral, filtering again, drying the solid phase obtained after filtering again to obtain the target product, and purifying the modified purine through the process.

In one embodiment of the present invention, the unsaturated quaternary ammonium salt monomer is one of methacryloxyethyl trimethyl ammonium chloride and diallyl dimethyl ammonium chloride.

Preferably, the unsaturated quaternary ammonium salt monomer is methacryloxyethyl trimethyl ammonium chloride.

One embodiment of the present invention is that the structural formula of the acrylic monomer is: ch2=ch-CO-O-R, where R is one of an alkyl group having a carbon chain length of not more than 4 or a hydroxyl-containing alkyl group, such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, and the like, but is not limited to these examples. Meanwhile, the carbon chain length of R is limited to be not more than 4, and when the carbon chain length of R is more than 4, the finally prepared emulsion is unstable, layering phenomenon can occur, and the demulsification effect is poor.

Preferably, the acrylic monomer is 4-hydroxybutyl acrylate, and when the acrylic monomer is adopted, the effect is relatively better, because when the carbon chain length of R is not more than 4, the longer the carbon chain length is, the better the final effect is, and meanwhile, after hydroxyl is introduced into acrylic ester, the viscosity of the whole system is increased, and the molecular weight is also relatively increased.

One embodiment of the invention is that the anionic emulsifier is one of sodium dodecyl sulfate and sodium dodecyl benzene sulfonate, and the concentration of the anionic emulsifier is 1.5-2 g/L. Of the anionic emulsifiers, more anionic emulsifiers can be used in the present invention, but sodium dodecyl sulfate and sodium dodecyl benzene sulfonate are preferable in terms of cost and ease of obtaining.

One embodiment of the invention is that the initiator is persulfate, and the addition amount of the initiator is 0.4-1.2% of the total mass of the two monomers; as for the initiator, it is not limited to persulfate, but it has been found through a lot of experiments by the inventors that when persulfate is used as the initiator, it has the following advantages: the initiation rate is moderate, while the temperature required for its initiation is relatively low. Therefore, in the present invention, persulfate is preferable as the initiator.

In one embodiment of the invention, after the acrylic ester monomer is added in S2, the acrylic ester monomer is reacted for 12 to 24 hours at the temperature of 25 ℃, and the inventor tests that the effect of the prepared product is optimal when the temperature is 25 ℃.

Another object of the present invention is to provide a reverse demulsifier prepared by any one of the above methods. The reverse demulsifier has the characteristics of high deoiling rate, small dosage and the like, and the use method is simple, and complex equipment and procedures are not required.

The invention has the beneficial effects that:

1. the reverse demulsifier has the advantages of high deoiling rate, less consumption, high oil-water separation speed and easy separation, demulsifies and destabilizes produced water, accelerates the oil-water separation speed, and is applied to the field of treatment of oil-containing sewage in petroleum exploitation.

2. The process for treating the produced water is simple, insoluble flocs can be rapidly produced by adding a certain amount of the product into the produced water and fully stirring, and the process is carried out through sedimentation separation and filtration, so that complex equipment and procedures are not required.

3. The invention has the advantages of easily available raw materials and simple synthesis process.

Drawings

FIG. 1 is an infrared spectrum of modified adenine in example 1;

FIG. 2 is a nuclear magnetic resonance spectrum of modified adenine in example 1;

FIG. 3 is an infrared spectrum of the reverse demulsifier 1 of example 1.

Detailed Description

In order to make the technical scheme and technical advantages of the present invention more clear, the technical scheme in the implementation process of the present invention will be clearly and completely described below with reference to the embodiments and the accompanying drawings.

The experimental methods used in the following examples are conventional methods unless otherwise specified.

Materials, reagents and the like used in the examples described below are commercially available unless otherwise specified.

In the following examples, the oilfield produced water was from a field in the Bohai sea, the initial turbidity value was 475NTU, and the oil content was 1560mg/L.

In the following examples, hydrochloric acid was used at a concentration of 37%.

In the following examples, methacryloyloxyethyl trimethyl ammonium chloride was used as an aqueous solution thereof in an effective content of 80%.

In the following examples, acryloyloxyethyl trimethyl ammonium chloride was used as an aqueous solution thereof in an effective content of 80%.

In the following examples, diallyldimethyl ammonium chloride was used as an aqueous solution thereof in an effective amount of 65%.

The acrylic monomer is shown in the formula 1, wherein R groups are one of linear alkyl groups and hydroxyl-containing linear alkyl groups, and the carbon chain number of the linear alkyl groups is less than or equal to 4;

CH ₂ =ch-CO-O-R1

Example 1

Modification synthesis of adenine: weigh 10g adenine and 10.23. 10.23g K ₂ CO ₃ Adding the mixture into a three-neck flask, adding 100ml of N-N dimethylformamide, placing the mixture into a constant-temperature water bath at 80 ℃ for reaction for 1h, and slowly dropwise adding 11.03g of 5-bromo-1-pentene by using a constant-pressure dropping funnel for reaction for 24h to obtain light yellow liquid. The reaction solution is cooled to room temperature, filtered by suction, the filtrate is collected, HCl is added dropwise to adjust the pH to 1-2, and white solid is gradually separated out. Freezing at 0deg.C for 12 hr, vacuum filtering again, collecting the solid in a beaker filled with 50ml petroleum ether, adding dropwise ammonia water to adjust pH of the solution to pH=7, filtering again to obtain solid, and vacuum drying at 60deg.C for 12 hr to obtain modified adenine. The specific reaction process of the process is as follows:

synthesis of reverse demulsifier: taking 26g of methacryloxyethyl trimethyl ammonium chloride aqueous solution, adding 4.16g of modified adenine, 17.75g of deionized water, 0.05g of sodium dodecyl sulfate and 2.01g of hydrochloric acid, after the hydrochloric acid is completely dissolved in the system, turning on a heating switch, keeping the temperature at 60 ℃, introducing nitrogen to remove oxygen for 20min, adding 0.01g of ammonium persulfate, initiating polymerization for 8h, cooling to 25 ℃, adding 1.75g of methyl acrylate, 0.816g of sodium hydroxide and 84.88g of deionized water, and continuing stirring to react for 12h to obtain F-1. The reaction of this process is specifically shown below:

example 2

This embodiment differs from embodiment 1 in that: in the reverse demulsifier synthesis process, 26g of methacryloyloxyethyl trimethyl ammonium chloride aqueous solution is replaced by 32g of diallyl dimethyl ammonium chloride aqueous solution, 17.75g of deionized water is replaced by 11.75g of deionized water, and the rest steps are the same, so that F-2 is finally prepared.

Example 3

This embodiment differs from embodiment 1 in that: in the reverse demulsifier synthesis process, 1.75g of methyl acrylate is replaced by 2.04g of ethyl acrylate, 84.88g of deionized water is replaced by 84.31g of deionized water, and the rest steps are the same, so that F-3 is finally prepared.

Example 4

This embodiment differs from embodiment 1 in that: in the reverse demulsifier synthesis process, 1.75g of methyl acrylate is replaced by 2.61g of butyl acrylate, 84.88g of deionized water is replaced by 87.16g of deionized water, and the rest steps are the same, so that F-4 is finally prepared.

Example 5

This embodiment differs from embodiment 1 in that: in the reverse demulsifier synthesis process, 1.75g of methyl acrylate is replaced by 2.37g of 2-hydroxyethyl acrylate, 84.88g of deionized water is replaced by 85.96g of deionized water, and the rest steps are the same, so that F-5 is finally prepared.

Example 6

This embodiment differs from embodiment 1 in that: in the reverse demulsifier synthesis process, 1.75g of methyl acrylate is replaced by 2.92g of 4-hydroxybutyl acrylate, 84.88g of deionized water is replaced by 88.72g of deionized water, and the rest steps are the same, so that F-6 is finally prepared.

Example 7

This embodiment differs from embodiment 1 in that: 17.7g of deionized water was replaced with 23.30g, and the rest of the steps were the same, to finally obtain F-7.

Example 8

Synthesis of modified guanine 10g of guanine and 9.14. 9.14g K are weighed out ₂ CO ₃ Adding the mixture into a three-neck flask, adding 100ml of N-N dimethylformamide, placing the mixture into a constant-temperature water bath at 80 ℃ for reaction for 1h, and then slowly dropwise adding 9.88g of 5-bromo-1-pentene by using a constant-pressure dropping funnel for reaction for 48h to obtain light yellow liquid. The reaction solution is cooled to room temperature, filtered by suction, the filtrate is collected, HCl is added dropwise to adjust the pH to 1-2, and white solid is gradually separated out. Freezing at 0deg.C for 12 hr, vacuum filtering again, collecting the solid in a beaker filled with 50ml petroleum ether, adding dropwise ammonia water to adjust pH of the solution to pH=7, filtering again to obtain solid, and vacuum drying at 60deg.C for 12 hr to obtain modified guanine.

The reverse demulsifier is synthesized by taking 26g of methacryloxyethyl trimethyl ammonium chloride aqueous solution, adding 4.16g of modified guanine, 17.84g of deionized water, 0.05g of sodium dodecyl sulfate and 1.87g of hydrochloric acid, turning on a heating switch after the hydrochloric acid is completely dissolved in the system, keeping the temperature at 60 ℃, adding 0.01g of ammonium persulfate after deoxidizing by introducing nitrogen for 20min, initiating polymerization for 8h, cooling to 25 ℃, adding 2.72g of 4-hydroxybutyl acrylate, 0.76g of sodium hydroxide and 87.91g of deionized water, and continuing stirring for reacting for 12h to obtain F-8.

Example 9

This embodiment differs from embodiment 6 in that: f-9 was obtained by replacing 2.92g of 4-hydroxybutyl acrylate with 1.75g of 4-hydroxybutyl acrylate, and replacing 88.72g of deionized water with 82.36g of deionized water, all in the same manner.

Example 10

This embodiment differs from embodiment 6 in that: f-10 was obtained by replacing 2.92g of 4-hydroxybutyl acrylate with 3.50g of 4-hydroxybutyl acrylate, and replacing 88.72g of deionized water with 91.61g of deionized water, all in the same manner.

Example 11

This embodiment differs from embodiment 6 in that: 0.05g of sodium dodecyl sulfate was replaced with 0.05g of sodium dodecyl benzene sulfonate, and the other steps were the same, to finally obtain F-11.

Comparative example 1

This embodiment differs from embodiment 6 in that: 0.05g of sodium dodecyl sulfate is replaced by 0.05g of Tween 80, and the rest steps are the same, so that D-1 is finally prepared.

Comparative example 2

This embodiment differs from embodiment 6 in that: 0.05g of sodium dodecyl sulfate was replaced with 0.05g of dodecyl trimethyl ammonium bromide, and the other steps were the same, to finally obtain D-2.

Comparative example 3

This comparative example differs from example 1 in that: in the reverse demulsifier synthesis process, 1.75g of methyl acrylate is replaced by 2.89g of amyl acrylate, 84.88g of deionized water is replaced by 88.56g of deionized water, and the rest steps are the same, so that D-3 is finally prepared.

Comparative example 4

This comparative example differs from example 1 in that: in the reverse demulsifier synthesis process, 26g of the aqueous solution of methacryloyloxyethyl trimethyl ammonium chloride is replaced by 26g of the aqueous solution of acryloyloxyethyl trimethyl ammonium chloride, and the rest steps are the same, so that D-4 is finally prepared.

Comparative example 5

This comparative example differs from example 1 in that: in the reverse demulsifier synthesis process, 17.70g of deionized water is replaced by 39.14g of deionized water, and the rest steps are the same, so that D-5 is finally prepared.

Comparative example 6

This comparative example differs from example 1 in that: in the reverse demulsifier synthesis process, 88.34g of deionized water is replaced by 127.38g of deionized water, and the rest steps are the same, so that D-6 is finally prepared.

In particular, regarding the reverse demulsifiers prepared in the above examples and comparative examples, the inventors found that, when the kinds of the emulsifiers were changed, the various reverse demulsifiers were found to have different results, and the stability and the residue of the emulsion synthesized under three different emulsifiers were observed under standing 48, as shown in the following table.

	Kinds of emulsifying agents	Stability and residue evaluation
			S-6	Anions (v-v)	The emulsion has no residue and good stability
S-10	Anions (v-v)	The emulsion has small amount of polymer residue and good stability
			D-1	Nonionic	The emulsion has more residues and poor stability, and sediment is generated after 48 hours
D-2	Cations (cationic)	Integral caking, failure to form an emulsion

To further illustrate the effectiveness of the reverse demulsifiers prepared in the above examples, the reverse demulsifiers prepared in the above examples 1 to 11 and comparative examples 1 to 5 were tested as follows.

1. Spectral testing

The modified purine of example 1 was taken and subjected to the following test:

infrared analysis: as shown in FIG. 1, 3228cm ^-1 And 3113cm ^-1 The strong peak of (2) belongs to N-H stretching vibration of primary amine; 2931cm ^-1 The strong peak at the position is the stretching vibration peak of the methine C-H bond on the purine ring; 1677cm ^-1 The peak at which belongs to the stretching vibration of the c=n double bond on the purine ring; 1602cm ^-1 Out-of-plane bending vibration belonging to primary amine N-H on purine ring; 660cm ^-1 Belongs to the out-of-plane bending vibration of N-H on pyrimidine ring. 1477cm ^-1 Out-of-plane bending vibration peaks of C-H of methylene appear; 999cm ^-1 、910cm ^-1 Out-of-plane bending vibrations of the olefinic hydrogen occur, which peaks belong to the characteristic absorption peaks of terminal olefins. Taken together, adenine was demonstrated to react successfully with 5-bromo-1-pentene and the target product was obtained.

Nuclear magnetic analysis: as shown in fig. 2, the peak at δ=8.30 ppm is ascribed to adenine six-membered ring-n=ch-N-, the peak at δ=8.23 ppm is ascribed to-n=ch-N-, on adenine five-membered ring, and the peak at δ=5.68 ppm is ascribed to-ch=ch on carbon atom with pendant pentenyl group attached to double bond ₂ The peak at δ=4.87 ppm is ascribed to pentenyl-ch=ch ₂ The peak at δ=4.21 ppm is attributed to-N-CH on the carbon atom attached to the N atom on the purine ring ₂ -CH ₂ -, delta=1.96 ppm peak ascribed to-CH on the side chain pentenyl ₂ -CH ₂ The peak at-CH-, delta=1.89 ppm is ascribed to-CH on pentenyl ₂ -CH ₂ -CH ₂ -. In the above, adenine reacts with 5-bromo-1-pentene successfully, and the objective product is obtained.

Taking the reverse demulsifier 1, and carrying out infrared scanning test on the reverse demulsifier, wherein the scanning result is shown in figure 3: at 3411cm ^-1 The peak at which is due to the characteristic stretching vibration of-N-H. At 1726cm ^-1 Is due to C=O stretching vibration absorption in methyl acrylate and methacryloyloxyethyl trimethyl ammonium chloride, 1635cm ^-1 The peak of (2) is generated by C=N stretching vibration on adenine ring. -CH ₂ and-CH ₃ The bending vibration absorption peaks of (C) appear at 1470cm respectively ^-1 And 1402cm ^-1 Where it is located. 1153cm ^-1 The peak at which corresponds to the stretching vibration peak of C-O in methyl acrylate. 950cm ^-1 Is the face on the purine nucleus=c-HThe outer shrinkage vibration peak. In view of the above, the reverse demulsifier has been successfully prepared.

2. Turbidity removal and oil removal test

50mL of the produced liquid of the oil field of the Bohai sea is taken and placed in a water removal bottle, and is firstly placed in a constant-temperature water bath at 75 ℃ for preheating for 10min; and then taking out the dehydration bottle filled with the produced liquid after preheating, adding the synthetic reverse emulsion breaker emulsion with the content of 50mg/L into the dehydration bottle, manually shaking the dehydration bottle up and down vigorously for 100 min, continuously heating the dehydration bottle after adding the medicament in a 75 ℃ water bath kettle at constant temperature for 10min, taking out the dehydration bottle, and standing for 5min. Removing a water sample at the lower layer of the dehydration bottle after standing, measuring the turbidity value of the water sample by a turbidity meter, and then calculating the turbidity removal rate; the OIL content was measured with an JC-OIL-6 type infrared spectrophotometry OIL meter and the OIL removal rate was calculated. The results are shown in the following table.

The final measurement results are shown in table 1.

Table 1 turbidity removal measurement results

1. The reverse demulsifier synthesized by comparing the turbidity reduction results and the oil removal effects of F-1, F-2 and D-4 synthesized under different cationic monomers has the best demulsification effect compared with the reverse demulsifier synthesized by taking diallyl dimethyl ammonium chloride and methacryloyloxyethyl trimethyl ammonium chloride as cationic monomers; when acryloyloxyethyl trimethyl ammonium chloride is adopted as a cationic monomer, the effect of the synthesized reverse demulsifier is poorer, and the actual use requirement is difficult to meet.

2. Compared with F-1, F-3, F-4, F-5 and F-6 are obtained by changing the types of acrylic ester, and the demulsifier synthesized by the reverse phase demulsifier has the best demulsification effect when the ester is acrylic acid-2-hydroxybutyl ester, because the cationic groups in the demulsifier can adsorb and bridge the action after the agent is added into sewage, the ester groups can adsorb to an oil-water interface, and the strength of the oil-water interface film is reduced, so that the oil-water separation is realized. As the carbon chain of the acrylic ester is increased, the hydrophobicity is increased, the hydrophobic substance is easier to generate interaction with oil drops, the demulsification effect is enhanced, and the coalescence and floating of the oil drops are facilitated, so that the demulsification effect of butyl acrylate is better than that of ethyl acrylate and methyl acrylate. Meanwhile, after hydroxyl is introduced into acrylic ester, the viscosity of the product is increased, and the molecular weight is increased, so that the demulsification effect of the acrylic acid-4-hydroxybutyl ester is best.

However, the carbon chain of the acrylic ester cannot be too long, see D-3, when the number of carbon atoms of the main chain is more than 4, stable emulsion cannot be formed, layering phenomenon is presented, and meanwhile, the demulsification effect is poor finally, so that the actual requirement is difficult to meet.

3. The modified purine is modified guanine when F-8 is obtained by changing the type of the modified purine as compared with F-6. The effect of the reverse demulsifier synthesized by using the modified guanine as a primary amine monomer is lower than that of adenine.

4. Compared with F-6, F-9 and F-10 are obtained by changing the molar ratio of the modified purine to the acrylic ester, and when the molar ratio of the modified purine to the acrylic acid-2-hydroxybutyl ester is too high, the acrylic acid-2-hydroxybutyl ester cannot be completely reacted, so that the demulsification effect is poor. When the molar ratio is too low, the effect of the demulsifier is low due to the low grafting ratio.

5. Compared with F-6, the anionic emulsifier used in the synthesis process is changed into a nonionic emulsifier and a cationic emulsifier to obtain D-1 and D-2, and compared with the results of three different types of nonionic, anionic and cationic emulsifiers, the anionic emulsifier has less synthetic emulsion residues and good emulsion stability; the nonionic emulsifier synthesizes emulsion, which has the effect similar to that of the reverse demulsifier prepared by the anionic emulsifier under certain conditions, but has the advantages of more residues, poor emulsion stability, long-term sediment generation, difficult storage and inapplicability to industrial application; the cationic emulsifier is integrally agglomerated in the emulsion synthesis process, so that emulsion cannot be formed, and meanwhile, the emulsion breaking effect is not achieved; and when F-11 is combined and the emulsifier is replaced by sodium dodecyl benzene sulfonate, only a small amount of polymer residues exist in the emulsion, and the demulsification effect is good. In summary, it is known that anionic emulsifiers should be selected for the polymerization system.

6. Compared with F-1, the monomer concentration of the polymerization of the methacryloyloxyethyl trimethyl ammonium chloride and the modified adenine is reduced from 50% to 45%, and the reverse demulsifier F-7 and the reverse demulsifier D-5 are respectively obtained by 40%, when the concentration of the monomer is lower than 45%, the turbidity reduction rate and the oil removal rate are greatly reduced, so that the concentration of the monomer is kept to be not lower than 45% during polymerization; after methyl acrylate is added, the system concentration is reduced from 20% to 15%, and the reverse demulsifier D-6 is obtained, and the demulsification performance is too low. In conclusion, the total mass concentration of the quaternary ammonium salt monomer and the modified purine monomer is not less than 45%, and the total mass concentration of the reaction monomer is not less than 20% by adding water into the acrylate monomer after polymerization.

The present invention is not limited to the above-mentioned embodiments, but is intended to be limited to the following embodiments, and any modifications, equivalents and modifications can be made to the above-mentioned embodiments without departing from the scope of the invention.

Claims

1. A method of preparing a reverse demulsifier comprising the steps of:

s1, modification of purine: adding equimolar amount of purine and potassium carbonate into a solvent, wherein 1-1.5 g of purine is added into each 10ml of solvent, then reacting for 1h at 70-90 ℃, then dropwise adding 5-bromo-1-pentene with equimolar amount of purine, cooling the reaction solution to room temperature after reacting for 24h, filtering, and purifying to obtain modified purine, wherein the purine is one of guanine and adenine;

s2, synthesizing a reverse demulsifier: adding an unsaturated quaternary ammonium salt monomer and a modified purine monomer with the mass ratio of 4-8:1 into water, deoxidizing, then adding an anionic emulsifier and hydrochloric acid, uniformly mixing, wherein the molar ratio of the hydrochloric acid to the modified purine monomer is 1:1, and then performing emulsion polymerization under the action of an initiator for 4-10 hours, wherein the total mass concentration of the two monomers is not less than 45%; cooling to 20-35 ℃ after polymerization, adding an acrylic ester monomer and alkali for neutralizing hydrochloric acid, adding water to ensure that the total mass concentration of the reaction monomer is not less than 20%, and continuously reacting for 12-24 hours at 20-35 ℃, wherein the molar ratio of the modified purine monomer to the acrylic ester monomer is 1:0.3-1.2.

2. The method according to claim 1, wherein in S1, the specific operations of filtering and purifying are as follows: filtering the reacted product, collecting filtrate, regulating the pH of the filtrate to 1-2, freezing for 12 hours at the temperature of-4~0 ℃, filtering, placing the filtered solid phase into petroleum ether, regulating the pH of the petroleum ether solution to be neutral, filtering again, and drying the solid phase obtained after the filtering again to obtain the target product.

3. The method according to claim 1, wherein the unsaturated quaternary ammonium salt monomer is one of methacryloxyethyl trimethyl ammonium chloride and diallyl dimethyl ammonium chloride.

4. A method according to claim 3, wherein the unsaturated quaternary ammonium salt monomer is methacryloxyethyl trimethyl ammonium chloride.

5. The method of claim 1, wherein the acrylic monomer has the structural formula: CH (CH) ₂ And =ch-CO-O-R, wherein R is one of an alkyl group having a carbon chain length of not more than 4 or an alkyl group having a carbon chain length of not more than 4 and containing a hydroxyl group.

6. The method of claim 5, wherein the acrylic monomer is 4-hydroxybutyl acrylate.

7. The method according to claim 1, wherein the anionic emulsifier is one of sodium dodecyl sulfate and sodium dodecyl benzene sulfonate, and the concentration of the anionic emulsifier is 1.5-2 g/L.

8. The method according to claim 1, wherein the initiator is persulfate, and the amount of the initiator added is 0.4-1.2% of the total mass of the two monomers.

9. The process of claim 1, wherein in S2, after addition of the acrylic monomer, the reaction is carried out at 25℃for 12 to 24 hours.

10. A reverse demulsifier prepared by the method of any one of claims 1-9.