A carbon quantum dot asphaltene inhibitor modified by a hydrophobic long carbon chain and a preparation method and application thereof

Abstract

This invention discloses a carbon quantum dot asphaltene inhibitor modified with hydrophobic long carbon chains, its preparation method, and its application, belonging to the field of oilfield unblocking technology. Citric acid and ethylenediamine are dissolved in distilled water. After the reaction is heated, the supernatant is collected by centrifugation to obtain a carbon quantum dot solution. An inorganic acid solution is then added, followed by an oxidation reaction, washing, and drying to obtain carboxylated carbon quantum dots. These are then mixed uniformly with N-aminopolyhexylamine and a solvent, a coupling agent is added, and after an amidation reaction, the mixture is rotary evaporated, washed with water, centrifuged, and dried to obtain the carbon quantum dot asphaltene inhibitor modified with hydrophobic long carbon chains. This invention utilizes π-π interactions, electrostatic attraction, hydrogen bonding, and van der Waals forces to interact with asphaltene molecules, forming a strong adsorption. The grafted hydrophobic long carbon chains create significant steric hindrance between asphaltene molecules, hindering the formation of large-scale parallel stacking, preventing direct contact and aggregation of asphaltene molecules, and significantly improving the inhibitor efficiency.

Description

Technical Field

[0001] This invention belongs to the field of oilfield unblocking technology, specifically relating to a carbon quantum dot asphaltene inhibitor modified with hydrophobic long carbon chains, its preparation method, and its application. Background Technology

[0002] With the continuous growth of energy demand and the rapid development of the petroleum industry, the quality control and processing technology of petroleum products have become important research directions. In the petroleum refining process, the presence of asphaltenes poses numerous challenges to the refining process and the properties of the final product. As a high-molecular-weight polymer in petroleum, asphaltenes have high viscosity, are difficult to dissolve, and can lead to pipeline blockage, equipment wear, and product quality degradation during processing. Therefore, developing effective asphaltenes inhibitors is crucial for improving petroleum processing efficiency and product quality.

[0003] Traditional asphaltenes inhibitors mainly consist of small molecule compounds and inorganic materials. While these traditional inhibitors can alleviate asphaltenes deposition to some extent, their effectiveness is often limited by insufficient solubility, poor stability, and weak selectivity. In recent years, the emergence of nanomaterials has brought new breakthroughs to this field. Among them, carbon quantum dots (CQDs), as a novel carbon nanomaterial, have become a research hotspot due to their unique optical properties, good biocompatibility, and other chemical properties. Carbon quantum dots are carbon nanomaterials, typically ranging in size from 2 to 10 nanometers, possessing excellent fluorescence properties and chemical stability. By introducing various functional groups onto the surface of carbon quantum dots, their chemical and physical properties can be significantly altered. For example, grafting long-chain alkyl groups or other hydrophobic groups onto the surface of carbon quantum dots can improve their dispersibility and stability in oily media. This modification not only enhances the hydrophobicity of carbon quantum dots but also strengthens their interaction with asphaltenes molecules in the oil phase. Carbon quantum dots modified with hydrophobic long carbon chains offer significant advantages: firstly, the hydrophobic modification enables the carbon quantum dots to exist stably in oily media, effectively reducing the deposition and aggregation of asphaltene; secondly, the surface functional groups of carbon quantum dots can form strong interactions with asphaltene molecules, further inhibiting their aggregation behavior. This method not only improves the performance of carbon quantum dots in oil production but also effectively addresses the shortcomings of traditional inhibitors in practical applications.

[0004] Currently, although some studies have attempted to use carbon quantum dots to suppress asphaltene deposition, these studies have focused on the basic properties of raw carbon quantum dots, and systematic research on how to improve their suppression effect through surface modification techniques is still lacking. Therefore, developing a method for preparing carbon quantum dot asphaltene inhibitors modified with hydrophobic long carbon chains will provide new ideas and solutions for asphaltene suppression technology. This will not only help improve the suppression effect in the oil extraction process, but also is expected to play an important role in improving the quality of petroleum products and reducing processing costs. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains, its preparation method and application, so as to solve the technical problem of asphaltenes easily agglomerating and depositing during crude oil extraction and refining.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a method for preparing carbon quantum dot asphaltenes inhibitors modified with hydrophobic long carbon chains, comprising the following steps:

[0008] S1: Dissolve citric acid and ethylenediamine in distilled water, heat the mixture and collect the supernatant after the reaction is complete, then centrifuge to obtain a carbon quantum dot solution;

[0009] S2: Add an inorganic acid solution to the carbon quantum dot solution obtained in step S1, and after oxidation reaction, washing and drying, obtain carboxylated carbon quantum dots;

[0010] S3: N-aminopolyhexylamine, solvent and carboxylated carbon quantum dots obtained in step S2 are mixed evenly, a coupling agent is added, and after amidation reaction, carbon quantum dot asphaltenes inhibitor modified by hydrophobic long carbon chain is obtained by rotary evaporation, water washing, centrifugation and drying.

[0011] Preferably, in step S1, the mass ratio of citric acid, ethylenediamine, and distilled water is 1:(1~2.5):(15~30).

[0012] Preferably, in step S1, the temperature of the heating reaction is 160~200℃ and the time is 4~10h.

[0013] Preferably, in step S2, the volume ratio of carbon quantum dot solution to inorganic acid solution is (30~50):1; the inorganic acid solution is any one of sulfuric acid, nitric acid and hydrochloric acid, and the mass concentration of the inorganic acid solution is 20%~60%.

[0014] Preferably, in step S2, the oxidation reaction is carried out at a temperature of 25~80℃ for 2~8h.

[0015] Preferably, in step S3, the mass ratio of carboxylated carbon quantum dots, N-aminopolyhexylamine, and solvent is 1:(2~3):(35~50); the solvent is any one of N,N-dimethylformamide, dimethyl sulfoxide, and tetrahydrofuran.

[0016] Preferably, in step S3, the coupling agent is any one of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, 1,3-dicyclohexylcarbodiimide, and N-hydroxysuccinimide; the amount of coupling agent added is 5% to 10% of the mass of the carboxylated carbon quantum dots.

[0017] Preferably, in step S3, the amidation reaction is carried out at a temperature of 25-35°C for 6-12 hours.

[0018] This invention also discloses a carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains, prepared by the above-described method. The general structural formula of the above-described carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains is as follows:

[0019] ;

[0020] Where n is the degree of aggregation, and the value of n ranges from 10 to 30.

[0021] The present invention also discloses the application of the carbon quantum dot asphaltene inhibitor modified with hydrophobic long carbon chains prepared by the above preparation method in crude oil extraction and petroleum refining, characterized in that the dispersion stability at 30°C is 88.5%~91.8%; and the dispersion stability at 150°C is 89.7%~95.9%.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention provides a method for preparing a carbon quantum dot asphaltene inhibitor modified with hydrophobic long carbon chains. Compared to traditional asphaltene inhibitors, this invention promotes the amidation reaction between carboxyl groups and N-aminopolyhexylamine on the surface of carbon quantum dots under the action of a coupling agent, thereby attaching N-aminopolyhexylamine to the surface of carbon quantum dots and synthesizing a carbon quantum dot asphaltene inhibitor. The modified carbon quantum dot inhibitor can interact with asphaltene molecules through π-π interactions, electrostatic attraction, hydrogen bonding, and van der Waals forces, effectively inhibiting their aggregation and deposition. Simultaneously, the carbon quantum dot inhibitor possesses a nanoscale size and a large specific surface area, forming a significant steric hindrance effect by adsorbing onto asphaltene molecules, effectively preventing direct contact and aggregation between asphaltene molecules, thus significantly improving inhibition efficiency and stabilizing the dispersion system. Furthermore, the hydrophobic long side-chain structure hinders the formation of large-scale parallel stacking, maintaining stable dispersion of asphaltene, thereby effectively preventing the formation of organic scale and significantly improving the efficiency of the inhibitor. Simultaneously, its nanoscale size and large specific surface area enable it to penetrate low-permeability and ultra-low-permeability reservoirs, effectively reducing viscosity and preventing deposition in the internal oil phase.

[0024] This invention also discloses a carbon quantum dot asphaltene inhibitor modified with hydrophobic long carbon chains prepared by the above-mentioned method. This inhibitor possesses nanoscale size and a large specific surface area, enabling it to effectively penetrate low-permeability and ultra-low-permeability reservoirs, achieving excellent viscosity reduction in the internal oil phase and effectively preventing deposition. Simultaneously, it enhances crude oil fluidity; the addition of the inhibitor helps maintain crude oil fluidity, reducing the increase in fluid resistance caused by asphaltene deposition, making crude oil easier to extract and transport, thereby improving oilfield production efficiency. The carbon quantum dot asphaltene inhibitor prepared by this invention also has a cost advantage. Its preparation raw material is low-cost and readily available citric acid, and the reaction process is simple and easy to control, suitable for large-scale production, helping to reduce inhibitor production costs and overall oilfield operating costs. Furthermore, this carbon quantum dot asphaltene inhibitor exhibits good chemical stability, maintaining its inhibitory effect under different temperature and pressure conditions, reducing asphaltene deposition problems caused by condition fluctuations.

[0025] This invention also discloses the application of the hydrophobic long-carbon chain modified carbon quantum dot asphaltene inhibitor prepared by the above-mentioned method in crude oil extraction and petroleum refining. The carbon quantum dot inhibitor prepared by this invention, through its unique molecular structure design, generates a strong interaction with asphaltene molecules, effectively dispersing asphaltene and significantly reducing the risk of formation blockage. The addition of the inhibitor reduces fluid resistance caused by asphaltene deposition, making crude oil flow smoother, thereby improving the efficiency of oilfield extraction and transportation. By effectively inhibiting asphaltene deposition, this inhibitor can also reduce internal blockage and corrosion of equipment, extend equipment service life, and reduce maintenance costs and economic losses caused by downtime. Attached Figure Description

[0026] Figure 1 This is a synthetic circuit diagram of the carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains disclosed in this invention.

[0027] Figure 2 The infrared spectrum of the carbon quantum dot asphaltene inhibitor modified with hydrophobic long carbon chains prepared in Example 2 of this invention.

[0028] Figure 3 This is a histogram showing the particle size distribution of the carbon quantum dot asphaltene inhibitor modified with hydrophobic long carbon chains disclosed in this invention. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] Unless otherwise specified, all technical and scientific terms used herein have the common meaning as understood by those skilled in the art in relation to the invention, and in the event of any conflict, the definitions in this specification shall prevail.

[0032] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0033] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0034] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0035] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0036] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0037] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0038] The present invention will now be described in further detail with reference to the accompanying drawings:

[0039] During crude oil extraction and refining, asphaltene often aggregates, flocculates, and deposits due to temperature and pressure fluctuations and changes in crude oil composition. These phenomena can lead to blockages in oil well formations and pipelines, ultimately affecting recovery rates and production efficiency. To address this problem, this invention aims to construct a carbon quantum dot asphaltene inhibitor modified with hydrophobic long carbon chains. This inhibitor suppresses the aggregation and deposition of asphaltene particles, reduces associated risks in crude oil production and transportation, and improves the stability and economic efficiency of the oil extraction and refining process.

[0040] This invention discloses a method for preparing carbon quantum dot asphaltenes inhibitors modified with hydrophobic long carbon chains, comprising the following steps:

[0041] S1: Dissolve citric acid and ethylenediamine in distilled water to form a homogeneous solution, then pour it into a high-pressure reactor and heat it for a period of time. After the reaction is complete, collect the supernatant by centrifugation to obtain a carbon quantum dot solution.

[0042] S2: An inorganic acid solution is added to a carbon quantum dot solution, and carboxyl groups are introduced onto the surface of the carbon quantum dots through an oxidation reaction. After the reaction is complete, the solution is washed repeatedly with excess distilled water to remove the acidic solution, and then dried to obtain carboxylated carbon quantum dots.

[0043] S3: Carboxylated carbon quantum dots, N-aminopolyhexylamine, and solvent were mixed evenly. A coupling agent was added to activate the reaction between the carboxyl and amino groups. After heating to a certain temperature, the mixture was stirred to carry out an amidation reaction. After the reaction was completed, a carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains was obtained by rotary evaporation, washing with water, centrifugation, and drying.

[0044] As an optional option, in step S1, the mass ratio of citric acid, ethylenediamine and distilled water is 1:(1~2.5):(15~30), the reaction temperature is 160~200℃, and the reaction time is 4~10h.

[0045] As an optional option, in step S2, the inorganic acid solution is one of sulfuric acid, nitric acid, and hydrochloric acid, and the mass concentration of the inorganic acid solution is 20%~60%; the volume ratio of carbon quantum dot solution to inorganic acid solution is (30~50):1; the oxidation reaction temperature is 25~80℃, and the reaction time is 2~8h.

[0046] As an optional step, in step S3, the solvent is one of N,N-dimethylformamide, dimethyl sulfoxide, and tetrahydrofuran; the mass ratio of carboxylated carbon quantum dots, N-aminopolyhexylamine, and solvent is 1:(2~3):(35~50); the coupling agent is one of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, 1,3-dicyclohexylcarbodiimide, and N-hydroxysuccinimide; the amount of coupling agent added is 5~10wt% of the mass of carboxylated carbon quantum dots; the amidation reaction temperature is 25~35℃, and the reaction time is 6~12h.

[0047] This invention provides a carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains. The general structural formula of this carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains is as follows:

[0048] ;

[0049] Where n is the degree of aggregation, and the value of n ranges from 10 to 30.

[0050] Based on the analysis of asphaltene molecular structure, this invention grafts N-aminopolyhexylamine onto the edges of carboxylated carbon quantum dot molecules through carboxylation and amidation reactions. The resulting carbon quantum dot asphaltene inhibitor exhibits strong π-π interactions with asphaltene molecules and provides steric hindrance through hydrophobic side chains, effectively preventing further polymerization and deposition of asphaltene molecules, thus significantly improving oil recovery. Furthermore, the carbon quantum dot asphaltene inhibitor possesses nanoscale size and a large specific surface area, enabling it to penetrate low-permeability and ultra-low-permeability reservoirs, effectively reducing viscosity and preventing deposition in the internal oil phase. It also offers cost advantages, as its preparation raw material is low-cost and readily available citric acid, and the reaction process is simple and easily controlled, making it suitable for large-scale production.

[0051] This invention provides an application of a hydrophobic long-carbon chain modified carbon quantum dot asphaltene inhibitor prepared according to the above-described method in crude oil extraction and petroleum refining. When used as a scale inhibitor in oilfields, the grafting of alkyl long chains onto the surface of the carbon quantum dots improves their dispersibility and stability in oily media. The presence of numerous hydrophobic side chains further hinders the formation of large-scale parallel stacking, maintaining stable dispersion of asphaltene and effectively preventing the formation of organic scale, thus significantly improving the inhibitor's efficiency. Furthermore, the carbon quantum dot asphaltene inhibitor possesses nanoscale size and a large specific surface area, enabling effective penetration into low-permeability and ultra-low-permeability reservoirs, achieving good viscosity reduction and effectively preventing deposition in the internal oil phase. Simultaneously, it enhances crude oil fluidity; the addition of the inhibitor helps maintain crude oil fluidity, reducing fluid resistance increases caused by asphaltene deposition, making crude oil easier to extract and transport, thereby improving oilfield production efficiency. It also extends equipment lifespan. By effectively inhibiting asphaltene deposition, the inhibitor reduces internal equipment blockage, thereby extending the service life of related equipment and reducing maintenance costs and downtime. By increasing recovery rates, reducing maintenance costs, extending equipment lifespan, and minimizing losses due to downtime, the application of this inhibitor can significantly improve the economic benefits of oil fields.

[0052] Example 1

[0053] A method for preparing a carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains includes the following steps:

[0054] S1: Dissolve 10g of citric acid and 10g of ethylenediamine in 150g of distilled water to form a homogeneous solution. Pour the solution into a high-pressure reactor and heat at 160℃ for 4 hours. After the reaction is complete, collect the supernatant by centrifugation to obtain a carbon quantum dot solution.

[0055] S2: Take 30 mL of carbon quantum dot solution and add 1 mL of 30% sulfuric acid solution to introduce carboxyl groups onto the surface of the carbon quantum dots through an oxidation reaction. The oxidation reaction temperature is 25℃ and the reaction time is 2 h. After the reaction is completed, 10 g of carboxylated carbon quantum dot solid is obtained after washing and drying.

[0056] S3: 1g of carboxylated carbon quantum dot solid was mixed with 2g of N-aminopolyhexylamine and 35g of N,N-dimethylformamide, and 0.05g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide was added. The mixture was heated to 25°C and stirred for 6 hours. Then, it was subjected to rotary evaporation, washing with water, centrifugation and drying to obtain carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains.

[0057] Example 2

[0058] A method for preparing a carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains includes the following steps:

[0059] S1: Dissolve 12g of citric acid and 24g of ethylenediamine in 180g of distilled water to form a homogeneous solution. Pour the solution into a high-pressure reactor and heat at 200℃ for 10 hours. After the reaction is complete, collect the supernatant by centrifugation to obtain a carbon quantum dot solution.

[0060] S2: Take 40 mL of carbon quantum dot solution and add 1 mL of 20% nitric acid solution to introduce carboxyl groups onto the surface of the carbon quantum dots through an oxidation reaction. The oxidation reaction temperature is 80℃ and the reaction time is 8 h. After the reaction is completed, 11 g of carboxylated carbon quantum dot solid is obtained after washing and drying.

[0061] S3: 1.5g of carboxylated carbon quantum dot solid was mixed with 3g of N-aminopolyhexylamine and 52.5g of dimethyl sulfoxide, and 0.15g of 1,3-dicyclohexylcarbodiimide was added. The mixture was heated to 35°C and stirred for 12h. Then, it was subjected to rotary evaporation, washing with water, centrifugation and drying to obtain carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains.

[0062] Example 3

[0063] A method for preparing a carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains includes the following steps:

[0064] S1: Dissolve 8g of citric acid and 20g of ethylenediamine in 240g of distilled water to form a homogeneous solution. Pour the solution into a high-pressure reactor and heat at 160℃ for 5 hours. After the reaction is complete, collect the supernatant by centrifugation to obtain a carbon quantum dot solution.

[0065] S2: Take 30 mL of carbon quantum dot solution and add 1 mL of 30% hydrochloric acid solution to introduce carboxyl groups onto the surface of the carbon quantum dots through an oxidation reaction. The oxidation reaction temperature is 35℃ and the reaction time is 4 h. After the reaction is completed, 6 g of carboxylated carbon quantum dot solid is obtained after washing and drying.

[0066] S3: 0.8g of carboxylated carbon quantum dot solid was mixed with 2.4g of N-aminopolyhexylamine and 40g of tetrahydrofuran, and 0.04g of N-hydroxysuccinimide was added. The mixture was heated to 25°C and stirred for 6 hours. Then, it was subjected to rotary evaporation, washing with water, centrifugation and drying to obtain a hydrophobic long-chain modified carbon quantum dot asphaltenes inhibitor.

[0067] Example 4

[0068] A method for preparing a carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains includes the following steps:

[0069] S1: Dissolve 15g of citric acid and 15g of ethylenediamine in 300g of distilled water to form a homogeneous solution. Pour the solution into a high-pressure reactor and heat at 200℃ for 7 hours. After the reaction is complete, collect the supernatant by centrifugation to obtain a carbon quantum dot solution.

[0070] S2: Take 50 mL of carbon quantum dot solution and add 1 mL of 60% sulfuric acid solution to introduce carboxyl groups onto the surface of the carbon quantum dots through an oxidation reaction. The oxidation reaction temperature is 25℃ and the reaction time is 8 h. After the reaction is completed, 12 g of carboxylated carbon quantum dot solid is obtained after washing and drying.

[0071] S3: 2g of carboxylated carbon quantum dot solid was mixed with 6g of N-aminopolyhexylamine and 100g of N,N-dimethylformamide, and 0.1g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide was added. The mixture was heated to 35°C and stirred for 12h. Then, it was subjected to rotary evaporation, water washing, centrifugation and drying to obtain hydrophobic long-chain modified carbon quantum dot asphaltenes inhibitor.

[0072] Example 5

[0073] A method for preparing a carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains includes the following steps:

[0074] S1: Dissolve 10g of citric acid and 25g of ethylenediamine in 150g of distilled water to form a homogeneous solution. Pour the solution into a high-pressure reactor and heat at 170℃ for 4 hours. After the reaction is complete, collect the supernatant by centrifugation to obtain a carbon quantum dot solution.

[0075] S2: Take 35 mL of carbon quantum dot solution and add 1.5 mL of 60% nitric acid solution to introduce carboxyl groups onto the surface of the carbon quantum dots through an oxidation reaction. The oxidation reaction temperature is 50℃ and the reaction time is 2 h. After the reaction is completed, 8 g of carboxylated carbon quantum dot solid is obtained after washing and drying.

[0076] S3: 1.2g of carboxylated carbon quantum dot solid was mixed with 3.6g of N-aminopolyhexylamine and 42g of dimethyl sulfoxide, and 0.12g of N-hydroxysuccinimide was added. The mixture was heated to 32℃ and stirred for 10h. Then, it was subjected to rotary evaporation, washing with water, centrifugation and drying to obtain a hydrophobic long-chain modified carbon quantum dot asphaltenes inhibitor.

[0077] Example 6

[0078] A method for preparing a carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains includes the following steps:

[0079] S1: Dissolve 9g of citric acid and 9g of ethylenediamine in 135g of distilled water to form a homogeneous solution. Pour the solution into a high-pressure reactor and heat at 175℃ for 5 hours. After the reaction is complete, collect the supernatant by centrifugation to obtain a carbon quantum dot solution.

[0080] S2: Take 30 mL of carbon quantum dot solution and add 1 mL of 30% hydrochloric acid solution to introduce carboxyl groups onto the surface of the carbon quantum dots through an oxidation reaction. The oxidation reaction temperature is 80℃ and the reaction time is 8 h. After the reaction is completed, wash and dry to obtain 8 g of carboxylated carbon quantum dot solid.

[0081] S3: 1g of carboxylated carbon quantum dot solid was mixed with 2.8g of N-aminopolyhexylamine and 38g of tetrahydrofuran, and 0.1g of 1,3-dicyclohexylcarbodiimide was added. The mixture was heated to 28℃ and stirred for 8h. Then, it was subjected to rotary evaporation, washing with water, centrifugation and drying to obtain hydrophobic long-chain modified carbon quantum dot asphaltenes inhibitor.

[0082] See Figure 1 This is a diagram illustrating the reaction mechanism for preparing the carbon quantum dot asphaltenes inhibitor disclosed in this invention. As can be seen from the diagram, citric acid and ethylenediamine are used as raw materials. After the reaction is carried out in an autoclave and heated, an acidic solution is added to introduce carboxyl groups. After the reaction is completed, the carboxylated carbon quantum dot solid and N-aminopolyhexylamine undergo an amidation reaction through washing and drying to introduce N-aminopolyhexylamine hydrophobic long chains, thereby endowing it with surface activity and obtaining a carbon quantum dot asphaltenes inhibitor modified with hydrophobic long chains.

[0083] Performance Characterization

[0084] Taking Example 2 as an example, the hydrophobic long carbon chain modified carbon quantum dot asphaltene inhibitor prepared in this example was characterized by infrared spectroscopy, and the results are as follows: Figure 2As shown.

[0085] Figure 2 The image shows the infrared spectrum of the carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains prepared in Example 2 of this invention. Figure 2 It can be seen that 3410 cm - The absorption peak at ¹ is attributed to the stretching vibration of the -OH bond; the peak at 2923 cm⁻¹ is also attributed to this vibration. - ¹ and 2815 cm - At position ¹, absorption peaks for the stretching vibrations of the -CH bond appeared; at 1728 cm⁻¹ - The absorption peak at ¹ is due to the stretching vibration of the -C=O bond; 1678 cm⁻¹ - The absorption peak at ¹ corresponds to the stretching vibration of the -C=O bond in the amide group; 1076 cm⁻¹ - The absorption peak at ¹ represents the -CN vibration of amine alkyl groups. Based on the infrared spectral characteristics, it can be inferred that a hydrophobic long carbon chain has been successfully introduced into the molecular structure edge of carbon quantum dots, and the carbon quantum dot asphaltenes inhibitor has been successfully synthesized.

[0086] To characterize the particle size distribution of a carbon quantum dot asphaltene inhibitor modified with hydrophobic long carbon chains, a nanolaser particle size analyzer was used to measure the particle size distribution of the carbon quantum dot asphaltene inhibitor, thus characterizing its particle size characteristics. Figure 3 As shown.

[0087] Figure 3 This is a histogram showing the particle size distribution of the carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains disclosed in this invention. Figure 3 As can be seen, the asphaltene inhibitor modified with hydrophobic long carbon chains exhibits a uniform particle size distribution, concentrated at (9±0.5) nm, with the main particle size below 10 nm, consistent with the typical particle size characteristics of carbon quantum dots. Furthermore, the particle size of the asphaltene inhibitor modified with hydrophobic long carbon chains is slightly larger than that of pure carbon quantum dots, primarily due to the introduction of hydrophobic long carbon chain structures onto its surface. Long carbon chain modification not only increases particle volume but also endows it with special properties such as hydrophobicity, steric hindrance, and chemical stability, further enhancing its dispersibility and inhibition performance in oilfield applications. This structural design achieves highly efficient inhibition of asphaltene by enhancing the interaction force between carbon quantum dots and asphaltene molecules.

[0088] To characterize the effect of hydrophobic long-carbon chain modified carbon quantum dot asphaltene inhibitors on asphaltene dispersion inhibition, the dispersion stability of hydrophobic long-carbon chain modified carbon quantum dot asphaltene inhibitors and carboxylated carbon quantum dots prepared in Examples 1, 2, 4, and 6 of this invention was tested. The test method was as follows: the hydrophobic long-carbon chain modified carbon quantum dot asphaltene inhibitors were dissolved in toluene at a mass ratio of 1:2 and dispersed for later use. A heavy oil sample extracted from Changqing Oilfield had an asphaltene content of 16.9% and a density of 0.9677 g / cm³. To determine its dispersion stability, 1 g of heavy oil sample was taken, 13 mL of n-heptane was added, and then 770 ppm of hydrophobic long-carbon chain modified carbon quantum dot asphaltene inhibitors or carboxylated carbon quantum dots were added. After stirring evenly, the mixture was allowed to stand at different temperatures for 24 h, and the solid phase mass was measured by centrifugation as m2. The dispersion stability was calculated using the formula: m1 - m2 / m1. The experimental results are detailed in Table 1.

[0089] Table 1. Results of dispersion stability tests under different temperature conditions

[0090]

[0091] As can be seen from the results in Table 1, the asphaltene inhibitors prepared by modifying hydrophobic long carbon chains in the embodiments of the present invention exhibit significant advantages in dispersion stability. Specifically, the dispersion stability of the asphaltene inhibitors modified by hydrophobic long carbon chains in each embodiment exceeds 88%, which is far superior to the dispersion effect of unmodified carboxylated carbon quantum dots. This result indicates that the asphaltene inhibitors modified by hydrophobic long carbon chains developed in this invention not only demonstrate excellent performance in inhibiting the aggregation and precipitation of asphaltene particles, but also maintain a good dispersion state over a long period of time, significantly improving the stability of the material. This superior performance provides a reliable technical guarantee for preventing blockage of equipment such as oil wells and oil pipelines under complex working conditions, further verifying the potential value of the present invention in practical applications.

[0092] This invention discloses a method for preparing a carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains. First, carbon quantum dots are carboxylated using an acidic solution. Then, an amidation reaction is performed to connect the hydrophobic long carbon chain N-aminopolyhexylamine to the carboxyl groups on the carbon quantum dots, ultimately obtaining a hydrophobic long carbon chain modified carbon quantum dot asphaltenes inhibitor. This inhibitor can interact with asphaltenes molecules through π-π interactions, electrostatic attraction, hydrogen bonding, and van der Waals forces, resulting in strong adsorption of asphaltenes. The grafted hydrophobic long carbon chains create significant steric hindrance between asphaltenes molecules, hindering the formation of large-scale parallel stacking, effectively preventing direct contact and aggregation of asphaltenes molecules, thus maintaining stable dispersion of the system, effectively preventing the formation of organic scale, and significantly improving inhibitor efficiency. The advantages of this carbon quantum dot inhibitor lie in its nanoscale size and large specific surface area, enabling it to penetrate low-permeability and ultra-low-permeability reservoirs, effectively reducing viscosity and preventing deposition in the internal oil phase. It also has a cost advantage, as its raw material is low-cost and readily available citric acid, and the reaction process is simple and easy to control, making it suitable for large-scale production.

[0093] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains, characterized in that, Includes the following steps: S1: Dissolve citric acid and ethylenediamine in distilled water, heat the mixture and collect the supernatant after the reaction is complete, then centrifuge to obtain a carbon quantum dot solution; S2: Add an inorganic acid solution to the carbon quantum dot solution obtained in step S1, and after oxidation reaction, washing and drying, obtain carboxylated carbon quantum dots; S3: N-aminopolyhexylamine, solvent and carboxylated carbon quantum dots obtained in step S2 are mixed evenly, a coupling agent is added, and after amidation reaction, carbon quantum dot asphaltenes inhibitor modified by hydrophobic long carbon chain is obtained by rotary evaporation, water washing, centrifugation and drying. The coupling agent is any one of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, 1,3-dicyclohexylcarbodiimide, and N-hydroxysuccinimide; the amount of the coupling agent added is 5% to 10% of the mass of the carboxylated carbon quantum dots; The structural formula of the N-aminopolyhexylamine is: ； Where n is the degree of aggregation, and the value of n ranges from 10 to 30.

2. The method for preparing carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains according to claim 1, characterized in that, In step S1, the mass ratio of citric acid, ethylenediamine and distilled water is 1:(1~2.5):(15~30).

3. The method for preparing carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains according to claim 1, characterized in that, In step S1, the temperature of the heating reaction is 160~200℃, and the time is 4~10h.

4. The method for preparing carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains according to claim 1, characterized in that, In step S2, the volume ratio of the carbon quantum dot solution to the inorganic acid solution is (30~50):1; the inorganic acid solution is either sulfuric acid or nitric acid, and the mass concentration of the inorganic acid solution is 20%~60%.

5. The method for preparing carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains according to claim 1, characterized in that, In step S2, the oxidation reaction is carried out at a temperature of 25-80°C for 2-8 hours.

6. The method for preparing carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains according to claim 1, characterized in that, In step S3, the mass ratio of the carboxylated carbon quantum dots, N-aminopolyhexylamine, and solvent is 1:(2~3):(35~50); the solvent is any one of N,N-dimethylformamide, dimethyl sulfoxide, and tetrahydrofuran.

7. The method for preparing carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains according to claim 1, characterized in that, In step S3, the amidation reaction is carried out at a temperature of 25-35°C for 6-12 hours.

8. A carbon quantum dot asphaltenes inhibitor modified with hydrophobic long carbon chains, characterized in that, The carbon quantum dot asphaltenes inhibitor prepared by any one of claims 1 to 7 has the following general structural formula: ； Where n is the degree of aggregation, and the value of n ranges from 10 to 30.

9. The application of the hydrophobic long-carbon chain modified carbon quantum dot asphaltene inhibitor prepared by the method according to any one of claims 1 to 7 in crude oil extraction and petroleum refining, characterized in that, The dispersion stability at 30℃ is 88.5%~91.8%; the dispersion stability at 150℃ is 89.7%~95.9%.

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