Carbon quantum dot modified polystyrene oil displacement material and preparation method thereof
阅读说明：本技术 一种碳量子点改性聚苯乙烯驱油材料及其制备方法 (Carbon quantum dot modified polystyrene oil displacement material and preparation method thereof ) 是由 林凌 余文可 罗云翔 李鑫 古晗 王国静 于 2020-11-20 设计创作，主要内容包括：本发明公开了一种碳量子点改性聚苯乙烯驱油材料的制备方法,首先将柠檬酸均匀溶解在去离子水中,通过微波法一步合成,再经纯化得到羧基化碳量子点；然后通过可逆加成-断裂转移法反应合成单伯胺基聚苯乙烯,最后将羧基化碳量子点、单伯胺基聚苯乙烯和1,1-羰基二咪唑缩合剂在30-50℃下搅拌反应3小时,将溶液倒入无水乙醇中,析出的聚合物即为碳量子点改性聚苯乙烯,用作驱油材料。该法合成的驱油材料能有效的降低界面张力且具有良好的洗油能力；将其应用在驱油上,相比于水驱和羧基化碳量子点溶液驱能有明显的提高采收率。(The invention discloses a preparation method of a carbon quantum dot modified polystyrene oil displacement material, which comprises the steps of uniformly dissolving citric acid in deionized water, synthesizing by a microwave method in one step, and purifying to obtain a carboxylated carbon quantum dot; and then synthesizing monoprimary amine polystyrene through a reversible addition-fragmentation transfer method, finally stirring and reacting the carboxylated carbon quantum dots, the monoprimary amine polystyrene and the 1, 1-carbonyl diimidazole condensing agent at 30-50 ℃ for 3 hours, pouring the solution into absolute ethyl alcohol, and separating out a polymer, namely the carbon quantum dot modified polystyrene, which is used as an oil displacement material. The oil displacement material synthesized by the method can effectively reduce the interfacial tension and has good oil washing capacity; the application of the compound in oil displacement can obviously improve the recovery ratio compared with water displacement and carboxylated carbon quantum dot solution displacement.)
1. A preparation method of a carbon quantum dot modified polystyrene oil displacement material is characterized in that aminated polystyrene and carboxylated carbon quantum dots are subjected to amide condensation reaction to prepare the carbon quantum dot modified polystyrene which is used as the oil displacement material.
2. The method for preparing the carbon quantum dot modified polystyrene flooding material of claim 1, wherein the aminated polystyrene is monoprimary amino polystyrene, and the molecular structural formula is as follows:
wherein n is an integer of 5 to 15.
3. The preparation method of the carbon quantum dot modified polystyrene flooding material of claim 2, characterized by comprising the following steps:
s1, preparing a carboxylated carbon quantum dot;
s2, preparing monoprimary amino polystyrene, comprising the following substeps:
s21, mixing 1-butanethiol, carbon disulfide, chloroform and triethylamine, stirring at room temperature for 3 hours, adding N-bromomethylphthalimide, and continuing to react for 16 hours to obtain a chain transfer agent;
s22, adding a chain transfer agent and azobisisobutyronitrile into a reaction container, adding styrene under the argon atmosphere, heating to 60 ℃, and reacting for 4-24h to obtain a RAFT polymerization product;
s23, dissolving the RAFT polymerization product and azobisisobutyronitrile in a benzene solvent under the argon atmosphere, then adding tri-n-butyltin hydride, heating to 50-80 ℃, reacting for 1-5h to obtain modified polystyrene with trithiocarbonate groups removed, then reacting the modified polystyrene with trithiocarbonate groups removed with hydrazine hydrate at 50-100 ℃ for 5-24h in the presence of DMF, pouring the mixed solution into methanol for precipitation, washing the precipitate with water, and drying to obtain the mono-primary-amine polystyrene;
and S3, carrying out amide condensation reaction on the carboxylated carbon quantum dots and monoprimary amino polystyrene to obtain the carboxylated carbon dot modified polystyrene.
4. The method for preparing the carbon quantum dot modified polystyrene flooding material of claim 3, wherein the step S3 is as follows: the carboxylated carbon quantum dots, monoprimary amine polystyrene and 1, 1-carbonyl diimidazole condensing agent are stirred and reacted for 3 hours at the temperature of 30-50 ℃, the solution is poured into absolute ethyl alcohol, and the precipitated polymer is the carbon quantum dot modified polystyrene.
5. The method for preparing the carbon quantum dot modified polystyrene flooding material of claim 3, wherein the carboxylated carbon quantum dot is prepared from anhydrous citric acid, the anhydrous citric acid is ultrasonically dispersed in deionized water, the mixture is placed in a microwave oven for heating reaction at 400-1000W power for 3-8 minutes to obtain a mixture of the carboxylated carbon quantum dot, and the mixture is purified to obtain the carboxylated carbon quantum dot.
6. The method for preparing the carbon quantum dot modified polystyrene flooding material of claim 5, wherein the mixture of the carboxylated carbon quantum dots is subjected to the following purification treatment operations: adding deionized water into the mixture of the carboxylated carbon quantum dots, performing ultrasonic treatment for 5-30 minutes to uniformly disperse the mixture, and directly dialyzing if the mixture has no solid residues; if the residue exists, performing centrifugal separation to remove the residue, and then performing dialysis; the dialysis operation is: adding the solution containing the carboxylated carbon quantum dots into a 500-1000D dialysis bag, dialyzing with deionized water for 48 hours, adding one third of the volume of the dialysis bag during dialysis, changing water every 6 hours, and freeze-drying the dialyzed solution containing the carboxylated carbon quantum dots to obtain pure carboxylated carbon quantum dots.
7. A carbon quantum dot modified polystyrene flooding material, which is characterized by being prepared by the preparation method of the carbon quantum dot modified polystyrene flooding material according to any one of claims 1 to 6.
8. The carbon quantum dot modified polystyrene flooding material of claim 7, wherein in use, the carbon quantum dot modified polystyrene is mixed with deionized water to prepare a uniform solution, namely the flooding fluid.
Technical Field
The invention relates to the technical field of oil and gas exploitation, in particular to a carbon quantum dot modified polystyrene oil displacement material and a preparation method thereof.
Background
The nano particles can maintain and even better show the physical and chemical properties of the nano particles in a micro scale, have the characteristics of large surface area, strong surface energy and the like, and can change the wettability of rock walls, reduce the tension of oil-water interfaces and increase the viscosity of the interfaces. Therefore, the nanoparticles dispersed in the fluid have great application prospect in improving the recovery ratio of crude oil. For example, the carbon quantum dots are composed of dispersed spheroidal carbon particles, the size is extremely small and is less than 10nm, so that the carbon quantum dots can be used as an oil displacement material to be prepared into an oil displacement fluid. However, the temperature resistance of the flooding fluid prepared by the nano particles is poor. Under the high-temperature environment, particles in the nanofluid can agglomerate and settle. Therefore, the oil displacement agent cannot be used for oil displacement under the high-temperature oil and gas reservoir environment of the stratum, and influences the oil displacement efficiency, so that the oil displacement efficiency is reduced.
Disclosure of Invention
The invention aims to provide a carbon quantum dot modified polystyrene oil displacement material and a preparation method thereof, aiming at the problem of poor temperature resistance when carbon quantum dots are used as an oil displacement agent. Synthesizing primary amino polystyrene by RAFT polymerization; and then, carboxylic carbon quantum dots are grafted on monoprimary amino polystyrene through an amide condensation reaction to prepare carbon quantum dot modified polystyrene, and the carbon quantum dot modified polystyrene is used as an oil displacement material and applied to oil displacement to obviously improve the recovery rate.
The invention provides a preparation method of a carbon quantum dot modified polystyrene oil displacement material, which comprises the following steps:
s1, preparing a carboxylated carbon quantum dot: ultrasonically dispersing anhydrous citric acid in deionized water, and placing the deionized water in a microwave oven for heating reaction for 3-8 minutes at the power of 400-1000W to obtain a mixture of carboxylated carbon quantum dots; adding deionized water into the mixture, performing ultrasonic treatment for 5-30min to disperse the mixture uniformly, performing dialysis directly if the mixture has no solid residue, and centrifuging to remove residue if the mixture has residue, and retaining clear liquid in which the carboxylated carbon quantum dot is located; the dialysis operation is: adding the solution containing the carboxylated carbon quantum dots into a 500-1000D dialysis bag, dialyzing with deionized water for 48 hours, adding one third of the volume of the dialysis bag during dialysis, changing water every 6 hours, and freeze-drying the dialyzed solution containing the carboxylated carbon quantum dots to obtain pure carboxylated carbon quantum dots.
S2, preparing monoprimary amino polystyrene, comprising the following substeps:
s21, mixing 1-butanethiol, carbon disulfide, chloroform and triethylamine, stirring at room temperature for 3 hours, adding N-bromomethylphthalimide, and continuing to react for 16 hours to obtain a chain transfer agent; the synthetic route of the chain transfer agent is as follows:
s22, adding a chain transfer agent and azobisisobutyronitrile into a reaction container, adding styrene under an argon atmosphere, and heating to 60 ℃. Reacting for 4-24h to obtain RAFT polymerization product with the following structural formula:
wherein n is an integer in the range of 5-15.
S23, dissolving the RAFT polymerization product and azobisisobutyronitrile in a benzene solvent under the argon atmosphere, then adding tri-n-butyltin hydride, heating to 50-80 ℃, and reacting for 1-5h to obtain modified polystyrene with trithiocarbonate groups removed; then, reacting the modified polystyrene with the removed trithiocarbonate groups with hydrazine hydrate for 5-24h at 50-100 ℃ in the presence of DMF, pouring the mixture into methanol for precipitation, washing the precipitate with water to remove DMF, crushing, and transferring to a vacuum oven at 40 ℃ for drying to obtain the primary amino polystyrene; the reaction process is as follows:
wherein n is an integer in the range of 5-15.
S3, adding 50-500mg of carboxylated carbon quantum dots, 1-10g of monoprimylamine polystyrene and 1, 1-carbonyldiimidazole condensing agent into a reaction vessel, reacting for 1-4 hours at 30-100 ℃ under stirring at the rotating speed of 1500r/min by using a stirrer 100, pouring the solution into absolute ethyl alcohol, separating out a polymer, filtering and drying to obtain the carboxylated carbon quantum dot graft modified polystyrene. The molar ratio of the amount of condensing agent to monoprimary amino polystyrene is 1: 1.
Preferably, step S1 is specifically: mixing 0.5-3g of anhydrous citric acid with 5-50mL of deionized water, then placing the mixture in an ultrasonic washing instrument, and ultrasonically dispersing for 2-10min to completely dissolve the citric acid; then the solution is placed in a microwave oven for heating reaction for 3-8 minutes under the power of 400-1000W to obtain a mixture containing the carbon carboxylated quantum dots. Adding 10-100mL of deionized water into the mixture containing the carboxylated carbon quantum dots, performing ultrasonic treatment for 5-30min to uniformly disperse the mixture, directly dialyzing the mixture if the mixture has no solid residues, separating the mixture if the mixture has the residues by using a high-speed centrifuge at 8000r/min, centrifuging for 5-10min, removing the residues, and retaining the supernatant of the carboxylated carbon quantum dots; adding the supernatant into a 500-1000D dialysis bag, dialyzing with deionized water for 48h, adding one third of the volume of the dialysis bag during dialysis, and changing water every 6 h. And freeze-drying the dialyzed carboxylated carbon-containing quantum dots to obtain the purified carboxylated carbon quantum dots.
When the carbon quantum dot modified polystyrene oil displacement material is used as an oil displacement material, the carbon quantum dot modified polystyrene is mixed with deionized water to prepare a uniform solution, namely the oil displacement fluid.
Compared with the prior art, the invention has the advantages that:
according to the invention, the carboxylated carbon quantum dots are grafted on the monoprimary amino polystyrene to obtain the quantum dot modified polystyrene, and the quantum dot modified polystyrene can be used as an oil displacement material and applied to oil displacement to obviously improve the recovery rate. The oil displacement material can effectively reduce interfacial tension and has good oil washing capacity. Test results show that the oil recovery rate of the flooding fluid prepared from the carbon quantum dot modified polystyrene and the deionized water is obviously higher than that of water flooding and carboxylic carbon quantum dot flooding.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Detailed Description
The following description of the preferred embodiments of the present invention is provided for the purpose of illustration and description, and is in no way intended to limit the invention.
Example 1
Preparation of carboxylated carbon quantum dots: 2g of anhydrous citric acid and 20mL of deionized water are mixed and placed in an ultrasonic cleaning instrument to completely dissolve the citric acid; and then placed in a microwave oven for 700W reaction for 4min to obtain a mixture. Adding 20mL of deionized water into the obtained mixture, placing the mixture in an ultrasonic washing instrument, and performing ultrasonic treatment for 5min to uniformly disperse the mixture; transferring into a centrifuge tube, and separating for 5min at 8000r/min with a high speed centrifuge; collecting supernatant, dialyzing, transferring the supernatant into 500-1000D dialysis bag, dialyzing with deionized water for 48h, and changing water every 6 h. And transferring the dialyzed solution out for freeze drying to obtain a solid product, namely the purified carboxylated carbon quantum dot.
Example 2
Preparation of carboxylated carbon quantum dots: mixing 0.5g of anhydrous citric acid with 5mL of deionized water, then placing the mixture in an ultrasonic washing instrument, and ultrasonically dispersing for 10min to completely dissolve the mixture; and then placing the solution in a microwave oven for heating reaction for 8 minutes under the power of 400W to obtain a mixture containing the carboxylated carbon quantum dots. Adding 100mL of deionized water into the mixture containing the carboxylated carbon quantum dots, performing ultrasonic treatment for 30min to uniformly disperse the mixture, directly dialyzing the mixture if the mixture has no solid residues, separating the mixture if the mixture has the residues by using a high-speed centrifuge, centrifuging the mixture at 8000r/min for 5-10min, and retaining the supernatant of the carboxylated carbon quantum dots; adding the supernatant into a 500-1000D dialysis bag, dialyzing with deionized water for 48h, adding one third of the volume of the dialysis bag during dialysis, and changing water every 6 h. And freeze-drying the dialyzed carboxylated carbon-containing quantum dots to obtain the purified carboxylated carbon quantum dots.
Example 3
Preparing the primary amino polystyrene, which comprises the following substeps:
(1) synthesis of Chain Transfer Agent (CTA):
in a dry three-necked flask equipped with a polytetrafluoroethylene rotor, a constant pressure dropping funnel and a condenser tube, 3.57g of 1-butanethiol, 6.07g of carbon disulfide and 25ml of chloroform were added, and 8.21g of triethylamine was slowly dropped under stirring, and the solution became orange-yellow with the formation of the intermediate triethylamine butyltrithiocarbonate. After the solution was stirred at room temperature for 3 hours, 9.59g of N-bromomethylphthalimide was added in portions slowly for not less than 30 min. The mixture solution thickened with the formation of bromide salt and the reaction was continued at room temperature for 16 h. After the reaction, 20ml of chloroform was added to dilute the reaction mixture, and the organic phase was successively diluted with deionized water and H2SO4(2M), deionized water and saturated brine. After washing, the organic layer was extracted with anhydrous MgSO4Drying overnight, filtering the solid material, removing the solvent by rotary evaporation to give a yellow solid, recrystallizing the crude product in hot ethanol, and transferring to a vacuum oven at 45 ℃ to dry overnight to give a bright yellow material, i.e. a chain transfer agent for RAFT polymerisation, in about 88.28% yield.
(2) RAFT polymerisation: adding 2.85g of synthesized Azobisisobutyronitrile (AIBN) with chain transfer and 1.17g into a three-neck flask provided with a polytetrafluoroethylene rotor and a spherical condenser in sequence, repeatedly ventilating for 3 times by an argon balloon and a three-way device, injecting 30.42g of styrene into the three-neck flask by using an injector, sealing the three-neck flask, heating to 60 ℃, reacting for 8 hours, opening the three-neck flask to allow oxygen to enter a quenching reaction, adding a polymer into methanol for multiple times of precipitation, shearing, filtering, transferring to a vacuum oven at 45 ℃ for drying to obtain a yellow solid, namely a RAFT polymerization reaction product (bis-phthalimide-terminated polystyrene).
(3) Removing the protecting group: 3.03g of synthesized bis-phthalimide-terminated polystyrene and 0.39g of azodiisobutyronitrile are sequentially added into a dry three-neck flask provided with a polytetrafluoroethylene rotor and a spherical condenser, after repeated ventilation for 3 times through an argon balloon and a three-way device, a proper amount of 20ml of benzene is injected into the flask by an injector to dissolve reactants, after complete dissolution, 5.24g of tri-n-butyltin hydride is added into the flask, the flask is heated to 70 ℃, and the color of the solution gradually becomes lighter from the initial yellow along with the reaction; after reacting for 3h, opening the three-neck flask to allow oxygen to enter for quenching reaction, after the solution is cooled to room temperature, concentrating the reaction solution through a rotary evaporator, pouring the mixed solution into methanol to precipitate a polymer, purifying for multiple times, filtering, transferring to a vacuum oven at 50 ℃ and drying overnight to obtain a light yellow solid substance, namely the modified polystyrene with the trithiocarbonate groups removed.
Adding 1.35g of modified polystyrene with the removed trithiocarbonate group into a dry three-neck flask provided with a polytetrafluoroethylene rotor and a spherical condenser, repeatedly ventilating for 3 times by using an argon balloon and a three-way device, injecting 25ml of DMF and 0.34g of hydrazine hydrate into the flask by using an injector, sealing a reaction system, reacting for 12 hours at 80 ℃, pouring the mixture into methanol for precipitation, washing the solid with water to remove DMF, crushing, transferring the solid into a vacuum oven at 45 ℃, and drying to obtain a white solid substance, namely the monoprimylamine-based polystyrene with the removed phthalimide group.
Example 4
Preparation of carboxylated carbon point modified polystyrene: 50mg of the carboxylated carbon quantum dot prepared in the example 1, 3g of monoprimary amino polystyrene prepared in the example 3 and 0.81g of 1, 1-carbonyl diimidazole are sequentially added into a three-neck flask provided with a polytetrafluoroethylene stirring paddle and a condensing tube, and are stirred at the temperature of 45 ℃ and the rotating speed of a stirrer of 1200r/min to react for 3 hours, the solution is poured into absolute ethyl alcohol to separate out a polymer, and the polymer is filtered and dried to obtain the carboxylated carbon quantum dot modified polystyrene.
Example 5
Carboxylated carbon quantum dot graft modified polystyrene: 500mg of the carboxylated carbon quantum dot prepared in example 2, 10g of monoprimary amino polystyrene prepared in example 3 and 2.7g of 1, 1-carbonyldiimidazole condensing agent are stirred in a three-neck flask with a polytetrafluoroethylene stirring paddle and a condenser tube at 100 ℃ and at the rotating speed of 100r/min for reaction for 4 hours, and then the solution is poured into absolute ethyl alcohol to separate out a polymer, and the polymer is filtered and dried to obtain the carboxylated carbon quantum dot graft modified polystyrene.
Example 6
Preparing an oil displacement fluid by adopting the carboxylated carbon quantum dot modified polystyrene prepared in the example 4: mixing the carboxylated carbon quantum dot modified polystyrene with a deionized water solution to prepare a uniform solution with the concentration of 0.2 wt%, thus obtaining the oil displacement fluid.
The oil displacement experiment by adopting the oil displacement fluid is as follows:
(1) treating a rock core: and drying the core, measuring the diameter and the length of the core, and weighing the dry weight of the core. And (3) vacuumizing the rock core for 4h under the pressure condition of-0.1 MPa to saturate bound water. The wet weight of the core is called after the saturated water, the mass increased before and after the saturated water of the core is calculated, the porosity and the pore volume of the core water drive are obtained according to the mass change of the core (in the experiment, the porosity of the core water drive is 8.73% and the pore volume is 49.9mL) and the water drive permeability is calculated according to the Darcy formula K which is Q mu LA delta p, the saturated oil (viscosity is 5.32cp) is carried out on the core at the injection speed of 0.35mL/min, the water drainage volume of the core is recorded by using a cylinder at the outlet end until the water does not flow out any more, and the total volume of the drained water is the volume of the saturated oil. The core was aged for 12h after being saturated with oil.
(2) After the aging is finished, the water is used for displacing the oil until no oil is discharged (the water content is higher than 98%) at 0.35mL/min, then the oil is displaced by 0.2 wt% of 1.5PV oil displacement fluid, and then the water is used for displacing the oil until no oil is discharged (the water content is higher than 98%). Recording the volume of oil and water discharged by the oil-water separator every 10min in the displacement process, and dividing the volume of oil discharged from the outlet end oil-water separator by the volume of saturated oil to obtain the recovery ratio; calculating real-time recovery efficiency and instantaneous water content; the recovery rate is 42.5 percent in the first stage of water flooding, the recovery rate is improved to 47.5 percent when the displacement fluid with the weight percent of 0.2 percent of 1.5PV is displaced, then the water flooding is performed, the recovery rate is improved to 51.15 percent after the displacement is finished, and the total displacement recovery rate is improved by 8.65 percent.
Comparative example 1
The nano fluid prepared by the carboxylated carbon quantum dot prepared in the example 1 is used for carrying out an oil displacement experiment, and the operation is as follows:
(1) treating a rock core: and drying the core, and weighing the dry weight of the core. And (3) vacuumizing the rock core for 4h under the pressure condition of-0.1 MPa to saturate bound water. And weighing the saturated water, calculating the mass of the core before and after the saturated water, and obtaining the water-drive porosity of the core of 8.64% and the pore volume of 51.1mL according to the mass change of the core. After the water drive permeability is calculated according to the Darcy formula K-Q [ mu ] LA [ delta ] p, saturated oil (viscosity 5.33cp) is injected into the core at the injection speed of 0.35mL/min, the water discharge volume of the core is recorded by using a measuring cylinder at the outlet end until water does not flow out any more, and the total volume of the discharged water is the volume of the saturated oil. The core was aged for 12h under experimental conditions after being saturated with oil.
(2) After the aging is finished, water is used for displacing the nano-particles until no oil is discharged (the water content is higher than 98%) at 0.35mL/min, then the nano-particles are displaced by 0.2 wt% of 1.5PV carboxylated carbon quantum dot nano-fluid, and then water is used for displacing the nano-particles until no oil is discharged (the water content is higher than 98%). Recording the volume of oil and water discharged by the oil-water separator every 10min in the displacement process, calculating the real-time recovery ratio and the instantaneous water content, and dividing the volume of oil discharged from the oil-water separator at the outlet end by the volume of saturated oil to obtain the recovery ratio; the recovery rate is 43.05 percent in the first stage of water flooding, the recovery rate is only increased to 44.5 percent in the displacement of 0.2wt percent of 1.5PV of the carboxylated carbon quantum dot nano fluid, and then the recovery rate is also only increased to 45.06 percent after the water flooding is finished, and the total displacement recovery rate is increased by 2.01 percent.
From the experimental results of example 6 and comparative example 1, it can be seen that the oil recovery rate of the carboxylated carbon quantum dot modified polystyrene oil displacement agent is obviously improved compared with water flooding and carboxylated carbon quantum dot flooding.
Example 7
Thermal stability test experiment:
(1) thermal stability experiment of carboxylated carbon quantum dot solution: preparing a 0.2 wt% solution of the carboxylated carbon quantum dots by using deionized water, putting the solution into a hydrothermal kettle, aging the hydrothermal kettle for 2 hours at 130 ℃, 150 ℃ and 170 ℃, respectively, keeping the carboxylated carbon quantum dot nanofluid clear and transparent at any time under the condition of 130 ℃, deepening the color at 150 ℃, and separating out solids at 170 ℃. The carboxylated carbon quantum dots can be stably dispersed in water at 130 ℃ and have good high-temperature resistance.
(2) Stability experiment of carboxylated carbon quantum dot modified polystyrene solution: preparing a solution with the concentration of 0.2 wt% from the carboxylated carbon point modified polystyrene, putting the solution into a hydrothermal kettle, aging the solution for 2 hours at 140 ℃, 160 ℃ and 180 ℃, respectively, keeping the carboxylated carbon point modified polystyrene solution uniformly dispersed at 140 ℃, and also uniformly dispersed at 160 ℃, wherein slightly agglomerated components appear at 180 ℃. The carboxylated carbon quantum dot modified polystyrene can be stably dispersed in water at 160 ℃, has excellent high temperature resistance, is obviously superior to the carboxylated carbon quantum dot, and is suitable for high-temperature oil and gas reservoirs.
Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.