A kind of thickened oil viscosity reducer based on graphene oxide nanosheet and its preparation method
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NINGBO RUIKR YONGYI TECHNOLOGY CO LTD
- Filing Date
- 2026-03-09
- Publication Date
- 2026-07-24
Smart Images
Figure CN122444935A_ABST
Abstract
Description
Technical Field
[0001] This application generally relates to the field of oilfield technology. More specifically, this application relates to a heavy oil viscosity reducer based on graphene oxide nanosheets and a method for preparing the same. Background Technology
[0002] Heavy oil, also known as heavy crude oil, presents significant challenges in its extraction, transportation, and refining processes due to its high viscosity, high density, and poor fluidity. Chemical viscosity reduction technology is one of the key methods to improve the recovery rate and fluidity of heavy oil. By adding viscosity reducers to heavy oil, its colloidal structure is altered or internal friction is reduced, thereby achieving viscosity reduction.
[0003] However, in practical applications, the viscosity-reducing effects of existing chemical viscosity reducers (such as surfactants and polymers) often heavily depend on the specific components of heavy oil (such as asphaltenes, gum content, and wax content) and the extraction environment. A viscosity reducer may be highly effective for heavy oil in one oilfield but ineffective for heavy oil with different compositions, exhibiting a "narrow matching range." Furthermore, formation conditions or crude oil properties may change at different stages of oilfield development, making it difficult for existing viscosity reducers to dynamically adjust accordingly. This results in unstable viscosity-reducing effects, increasing extraction costs and technical difficulties.
[0004] In view of this, there is an urgent need to provide a thick oil viscosity reducer with a wide range of applications and adjustable performance, as well as its preparation method, so as to meet the thick oil viscosity reduction requirements of different components and extraction stages. Summary of the Invention
[0005] In order to at least solve one or more of the technical problems mentioned above, this application proposes a solution for a heavy oil viscosity reducer based on graphene oxide nanosheets and a method for preparing the same in several aspects.
[0006] In a first aspect, this application provides a method for preparing a heavy oil viscosity reducer based on graphene oxide nanosheets, comprising the following steps: S101, amino functionalization modification: reacting graphene oxide nanosheets with diamine to obtain aminated graphene oxide; S102, introducing double bonds: subjecting the aminated graphene oxide to an amidation reaction with acrylic acid to obtain double-bond modified graphene oxide; S103, polymerization grafting: under the action of an initiator, subjecting the double-bond modified graphene oxide to a free radical polymerization reaction with vinyl acetate to obtain a graphene oxide graft product with polyvinyl acetate long chains grafted onto its surface; S104, alcoholysis: subjecting the graphene oxide graft product to an alcoholysis reaction to obtain a heavy oil viscosity reducer.
[0007] In some embodiments, in step S101, the diamine includes at least one of ethylenediamine, propylenediamine, butanediamine, pentanediamine, and hexanediamine.
[0008] In some other embodiments, in step S101, the mass ratio of the diamine to the graphene oxide nanosheets is (10~15):1.
[0009] In some other embodiments, in step S102, the mass ratio of the acrylic acid to the aminated graphene oxide is (10~15):1.
[0010] In some embodiments, in step S103, the mass ratio of the vinyl acetate to the double bond modified graphene oxide is (4~8):0.4; and / or, the reaction temperature of the free radical polymerization reaction is 40℃~60℃.
[0011] In some other embodiments, in step S103, the initiator is potassium persulfate; and / or sodium bicarbonate may be added after the free radical polymerization reaction to adjust the graphene oxide graft product to be neutral.
[0012] In some other embodiments, in step S104, the alcohol used for alcoholysis includes methanol or ethanol; and / or the alcoholysis reaction is carried out under alkaline conditions.
[0013] In some embodiments, in step S104, the mass ratio of the alcohol to the double-bond modified graphene oxide is (5~10):4.
[0014] In some other embodiments, in step S104, the reaction temperature of the alcoholysis reaction is 40°C to 60°C.
[0015] In a second aspect, this application provides a heavy oil viscosity reducer prepared according to the preparation method described in any one of the first aspects of this application.
[0016] The method and product for preparing a thick oil viscosity reducer based on graphene oxide nanosheets, as described above, demonstrate that this application's embodiments utilize a four-step reaction involving graphene oxide amination, amidation to introduce double bonds, free radical polymerization grafting of long chains, and controlled alcoholysis to prepare a structurally tunable viscosity reducer. The core of this method lies in precisely controlling the alcoholysis step, which allows for flexible adjustment of the degree of ester hydrolysis (i.e., alcoholysis ratio) of the grafted polymer chains. This alters the hydrophilic-lipophilic balance (HLB value) of the viscosity reducer molecules, enabling them to match thick oils with different components and properties. This fundamentally solves the problem of narrow compatibility of existing viscosity reducers, achieving "adapter-specificity." Furthermore, in some embodiments, by selecting specific diamines and their dosage ratios, the amino grafting density on the graphene oxide surface can be optimized, laying a solid foundation for subsequent reactions. Furthermore, in some embodiments, by controlling the material ratio and temperature in the polymerization grafting and alcoholysis reactions, the length of the grafted chain and the degree of alcoholysis can be precisely controlled, thereby achieving fine-tuning of the viscosity reducer's performance, making it more adaptable to heavy oil and with a better viscosity-reducing effect. Attached Figure Description
[0017] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of this application are illustrated by way of example and not limitation, and the same or corresponding reference numerals denote the same or corresponding parts, wherein: Figure 1 An exemplary flowchart of a method for preparing a heavy oil viscosity reducer based on graphene oxide nanosheets according to an embodiment of this application is shown. Figure 2 This is a transmission electron microscope image of graphene oxide with double bonds in the embodiments of this application; Figure 3 This is a transmission electron microscope image of the functional graphene oxide in the embodiments of this application; Figure 4 This is a transmission electron microscope (TEM) image of grafted and modified graphene oxide in the embodiments of this application. Detailed Implementation
[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0019] It should be understood that the terms "comprising" and "including" used in the specification and claims of this application indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.
[0020] It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application. As used in this specification and claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this specification and claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.
[0021] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings.
[0022] Figure 1 An exemplary flowchart illustrating a method for preparing a heavy oil viscosity reducer based on graphene oxide nanosheets according to an embodiment of this application is shown. Figure 1As shown, the preparation method 100 includes the following steps: S101, amino-functionalized modification: reacting graphene oxide nanosheets with diamine to obtain aminated graphene oxide; S102, introducing double bonds: reacting aminated graphene oxide with acrylic acid to obtain double-bond modified graphene oxide; S103, polymerization grafting: under the action of an initiator, reacting double-bond modified graphene oxide with vinyl acetate to obtain graphene oxide grafted with long chains of polyvinyl acetate on the surface; S104, alcoholysis: subjecting the graphene oxide grafted product to alcoholysis to obtain a heavy oil viscosity reducer.
[0023] In step S101, graphene oxide nanosheets refer to two-dimensional sheet-like carbon materials with a single atomic layer or a few atomic layers thickness, obtained by deep oxidation and exfoliation of graphite. Their surface and edges are rich in active oxygen-containing functional groups such as epoxy groups, hydroxyl groups, and carboxyl groups. Amino functionalization modification refers to using the amino groups at both ends of a diamine molecule (such as ethylenediamine) to undergo nucleophilic ring-opening reactions with epoxy groups and other groups on the surface of graphene oxide nanosheets, or to undergo amidation reactions with carboxyl groups, thereby covalently grafting amino groups (-NH2) onto the graphene oxide framework to obtain aminated graphene oxide.
[0024] The purpose of step S101 is to introduce highly reactive amino (-NH2) functional groups onto the surface and edges of graphene oxide sheets. The introduction of amino groups not only improves the dispersibility of graphene oxide in water, but more importantly, provides a crucial chemical "anchor" (amino group) for subsequent steps. This allows acrylic acid to be firmly grafted via amide bonds, thereby constructing a molecular bridge connecting the graphene core and the long polymer chain. This is a foundational step for ultimately achieving tunable structure and controllable performance of the viscosity reducer.
[0025] In some embodiments, in step S101, the diamine includes at least one of ethylenediamine, propylenediamine, butanediamine, pentanediamine, and hexamethylenediamine. The carbon chain length of the diamine can affect the spatial structure of the subsequent modified product. Specifically, the carbon chain length of the diamine directly affects the intermolecular spacing between the amino groups grafted onto the surface of the graphene oxide after its reaction with graphene oxide. When a diamine with a shorter carbon chain (such as ethylenediamine) is used, the inter-amino spacing is small, which can form a higher density of "anchor points" on the surface of graphene oxide. The subsequently introduced double bonds and the grafted polymer chains are arranged relatively tightly, resulting in a more compact spatial structure of the product. Conversely, when a diamine with a longer carbon chain (such as hexamethylenediamine) is used, the inter-amino spacing increases, reducing the density of surface active sites and providing greater free extension space and flexibility for the subsequently grafted polymer chains, resulting in a more porous product structure and potentially increased interlayer spacing. The preferred embodiment of this application is to select a diamine (i.e., ethylenediamine to hexamethylenediamine) with a carbon chain length of C2 to C6. This range allows for precise control of the three-dimensional spatial structure and interfacial properties of the final viscosity reducer product by adjusting the carbon chain length, while ensuring sufficient reactivity and grafting efficiency, thereby adapting to the requirements of different heavy oil systems for the molecular configuration of the viscosity reducer.
[0026] In other embodiments, in step S101, the mass ratio of the diamine to the graphene oxide nanosheets is (10~15):1 to ensure sufficient amination. Exemplarily, the mass ratio of the diamine to the graphene oxide nanosheets can be 10:1, 11:1, 12:1, 13:1, 14:1, or 15:1, or other values within the range of (10~15):1.
[0027] The aforementioned mass ratio of diamine to graphene oxide nanosheets (10~15):1 aims to ensure a sufficient excess of diamine relative to graphene oxide nanosheets. Its core technical effects are: First, it provides a high concentration of reactants to drive and almost completely react the oxygen-containing active sites (such as epoxy groups and carboxyl groups) on the surface and edges of graphene oxide, thereby achieving high-density and uniform amino functionalization and building a solid active foundation for subsequent steps; Second, the excess diamine can effectively compensate for the consumption caused by molecular diffusion, steric hindrance, or the participation of the amino groups at both ends of some amine molecules in the reaction, ensuring the thoroughness and reproducibility of the reaction. This ratio range has a key synergistic effect with the type of diamine: for diamines with shorter carbon chains and higher reactivity (such as ethylenediamine), a ratio close to the lower limit (such as 10:1) is usually sufficient for efficient grafting; while for diamines with longer carbon chains, larger molecular volumes, or relatively lower reactivity (such as hexamethylenediamine), a ratio close to or even reaching the upper limit (such as 15:1) is required to overcome the adverse effects of slowed molecular diffusion or increased steric hindrance, ensuring a degree of amination comparable to that of short-chain amines. Therefore, this preferred range not only provides a general guarantee for full functionalization but also endows the process with adaptability to diamines with different structures, ensuring that reliable amination intermediates can be obtained under different amine source selections, which is an important prerequisite for achieving subsequent tunable grafting structures.
[0028] In step S102, the amidation reaction refers to the dehydration condensation reaction between the amino group (-NH2) grafted onto the surface of the aminated graphene oxide sheet and the carboxyl group (-COOH) of the acrylic acid molecule. The principle is that the amino group acts as a nucleophile, attacking the carboxyl carbon, removing one molecule of water, and forming a stable amide bond (-CO-NH-). Through this reaction, the vinyl group (i.e., the carbon-carbon double bond, C=C) in the acrylic acid molecule is covalently "anchored" to the graphene oxide framework through the newly formed amide bond, thus obtaining double-bond modified graphene oxide. The core purpose of this step is to introduce an active double-bond structure that can participate in free radical polymerization onto the graphene oxide, providing the necessary polymerization sites for the polymerization grafting of vinyl acetate monomer in subsequent steps. Its key effects are: First, by firmly fixing the double bonds to the surface of the nanosheets through covalent bonds, it ensures that the subsequent polymer chains can grow stably and uniformly in situ; Second, the introduced double bonds, as the starting point of the polymerization reaction, directly determine the number and distribution of grafted chains, which is the basic step in constructing the tunable hybrid structure of "graphene oxide core-polymer shell", and ultimately affects the interfacial behavior and dispersion performance of the viscosity reducer in heavy oil.
[0029] In some other embodiments, in step S102, the mass ratio of acrylic acid to aminated graphene oxide is (10~15):1. Exemplarily, the mass ratio of acrylic acid to aminated graphene oxide can be 10:1, 11:1, 12:1, 13:1, 14:1, or 15:1, or other values within the range of (10~15):1.
[0030] This mass ratio (10~15):1 means that acrylic acid is used in significant excess relative to aminated graphene oxide. For example, if 0.4 grams of aminated graphene oxide is used, then 4 to 6 grams of acrylic acid need to be added. The core technical benefits are: First, the sufficient excess of acrylic acid ensures that most of the amino groups (derived from step S101) grafted onto the surface and edges of the aminated graphene oxide can participate in the amidation reaction, thereby maximizing the covalent grafting of acryloyl groups (carrying double bonds) onto the sheets and achieving high-density double bond functionalization, which is the basis for subsequent effective polymerization and grafting. Second, the excess acrylic acid can drive the reaction equilibrium towards the product direction, improving reaction efficiency and consistency. This ratio is crucially related to and synergistically related to the previous step S101: the grafting density (i.e., the number of amino groups) of the diamine in step S101 directly determines the theoretical minimum amount of acrylic acid required in step S102. The broad and excessive ratio design of (10~15):1 is precisely to accommodate the fluctuations in the degree of amination that may occur in S101 due to different types of diamines and reaction efficiencies. This ensures that even with intermediates of different amino densities, this step can still achieve stable and sufficient double bond introduction, thereby guaranteeing the robustness of the entire synthesis process and the controllability of the final viscosity reducer structure (such as the graft chain density).
[0031] In step S103, the free radical polymerization reaction is a chain polymerization process initiated by active free radicals generated by the decomposition of an initiator (such as potassium persulfate). The principle is as follows: the free radicals first attack the acryloyl double bonds grafted onto the double-bond modified graphene oxide surface, or the double bonds of the free vinyl acetate monomer in the system, initiating chain growth. This results in the in-situ growth of long polyvinyl acetate (PVAc) chains on the surface of the graphene oxide sheets, forming a chemically bonded "graphene oxide-polymer" grafted hybrid structure. The core objective of this step is to construct flexible polymer molecular "brushes" or "shells" on the rigid two-dimensional framework of graphene oxide nanosheets. The key effects are as follows: First, by combining the long-chain characteristics of the polymer with the layered characteristics of the nanosheets through covalent grafting, the interfacial activity and steric hindrance of the product in complex oil phases are significantly enhanced. Second, the grafted PVAc long chains themselves have good hydrophobicity and chain flexibility, which can effectively insert into and disperse the gum and asphaltenes aggregates in heavy oil, destroying their network structure. Third, this grafted structure provides a chemically modifiable substrate (ester group) for the subsequent alcoholysis reaction, which is the core design step to achieve the final adjustable hydrophilic-lipophilic balance of the viscosity reducer, directly determining the adaptability and efficacy of the viscosity reducer to heavy oil.
[0032] In some embodiments, in step S103, the mass ratio of vinyl acetate to double-bond modified graphene oxide is (4~8):0.4, i.e. (10~20):1. Exemplarily, the mass ratio of vinyl acetate to double-bond modified graphene oxide can be 4:0.4, 4.5:0.4, 5:0.4, 5.5:0.4, 6:0.4, 6.5:0.4, 7:0.4, 7.5:0.4, or 8:0.4, or other values within the range of (4~8):0.4.
[0033] The mass ratio (4~8):0.4 set in step S103 (i.e., the ratio of vinyl acetate monomer to the double-bond modified graphene oxide carrier) is primarily used to precisely control the length and density of the grafted polymer chains by adjusting the monomer feed amount. This ratio range is a key balance point to ensure effective grafting and avoid excessive homopolymerization: when the ratio is at the lower limit (e.g., 4:0.4), the monomer is relatively limited, tending to grow near each double-bond active site on the graphene oxide surface, forming shorter polymer chains with potentially higher graft site coverage; when the ratio is increased to the upper limit (e.g., 8:0.4), a sufficient monomer supply allows the grafted chains to continue growing, thus forming longer, flexible polymer chains, enhancing steric hindrance and interfacial disturbance capabilities, but it must be strictly controlled at the temperature (40℃~60℃) where the initiator has suitable initiation efficiency to avoid excessive self-polymerization of the monomer to form free homopolymers. The setting of this ratio is directly related to the performance of the preceding steps S101 and S102: the selection and degree of reaction of the diamine in S101 determines the amino density on the surface of graphene oxide, while the amidation efficiency in S102 determines the actual number of polymerizable double bonds converted into these amino groups, i.e., the double bond density. Therefore, the monomer feed ratio in step S103 is precisely to adapt to the potentially fluctuating number of active sites determined by the first two steps, ensuring that reliable control of the final graft product's molecular configuration (chain length, chain density) can be achieved within this ratio range under different batches or different amine source conditions. This is the basis for achieving adjustable viscosity reducer performance and adaptability to different heavy oil components.
[0034] In some embodiments, in step S103, the reaction temperature of the free radical polymerization reaction is 40°C to 60°C. Exemplarily, the reaction temperature of the free radical polymerization reaction can be 40°C, 45°C, 50°C, 55°C, or 60°C, or other values within the range of 40°C to 60°C. This temperature range is beneficial for the efficient decomposition of the initiator and for controlling the polymerization rate.
[0035] In some embodiments, in step S103, sodium bicarbonate (NaHCO3) can be added after the free radical polymerization reaction to adjust the graphene oxide graft product to be neutral. The core function of adding sodium bicarbonate (NaHCO3) after the free radical polymerization reaction is to precisely terminate the reaction and stabilize the reaction system through chemical means. Its mechanism is twofold: first, it neutralizes the reaction system. The potassium bisulfate produced after the decomposition of the polymerization initiator potassium persulfate makes the system acidic. NaHCO3, as a weak base, can quickly neutralize the acidic environment, eliminating the activation effect of hydrogen ions on the residual initiator and the growing chains; second, it quenches active free radicals. NaHCO3 or its decomposition products can effectively capture residual free radicals in the system, thereby completely terminating the chain growth reaction. This operation not only locks in the molecular weight and graft chain structure of the polymer, preventing over-reaction, but also creates a stable neutral starting environment for the subsequent alcoholysis, avoiding localized overheating and product destruction caused by violent acid-base neutralization when directly adding alkali later. It is a key step in ensuring process controllability and product reproducibility.
[0036] In step S104, the alcoholysis reaction refers to the transesterification reaction of the PVAc side chain acetate groups on the graphene oxide graft product with long polyvinyl acetate (PVAc) grafted on its surface, obtained in the previous steps, under alkaline conditions, using a short-chain alcohol (such as methanol or ethanol). The reaction principle is that the alkoxy group of the alcohol nucleophilically attacks the carbonyl carbon in the ester group, ultimately converting the ester group (-OCOCH3) into a hydroxyl group (-OH) and generating the corresponding alkyl acetate ester. The fundamental purpose of this step is to perform key chemical modifications and performance "fine-tuning" on the constructed "graphene oxide-polymer" hybrid structure. By precisely controlling the conditions of the alcoholysis reaction (such as the amount of alcohol, temperature, etc.), the ratio of acetate groups replaced by hydroxyl groups in the PVAc chain segment (i.e., the degree of alcoholysis) can be adjusted as needed, thereby achieving continuous and precise control of the balance between the hydrophilicity (from the hydroxyl group) and hydrophobicity (from the remaining acetate group) of the final viscosity reducer molecule. For example, a low degree of alcoholysis results in a product with more hydrophobic acetate groups and weak hydrophilicity; a high degree of alcoholysis results in a product with more hydrophilic hydroxyl groups and strong hydrophilicity. Therefore, by adjusting the degree of alcoholysis, the hydrophilic-lipophilic balance (HLB value) of the entire viscosity reducer molecule can be continuously adjusted, enabling it to achieve optimal matching with heavy oil systems of different polarities and compositions, thereby achieving a highly efficient and universal viscosity-reducing effect.
[0037] The core technological effect of this step is that it endows the viscosity reducer with excellent adaptive potential, enabling it to match heavy oil systems with different polarities and different gum-asphalt compositions by changing the degree of alcoholysis. This transforms a fixed-structure intermediate into a final product with adjustable performance, perfectly solving the core problem of the narrow applicability of traditional viscosity reducers. It is the most critical link in realizing the innovative concept of "the agent changes with the oil" in this application.
[0038] The alcoholysis reaction in step S104 must be carried out in an alkaline environment. The fundamental principle is that alkaline conditions are the core driving force for the efficient and controllable transesterification reaction. Specifically, the base (such as NaOH) first reacts with a short-chain alcohol (such as methanol) to generate a strong nucleophile, the alkoxide anion (CH3O-). This anion can efficiently attack the ester groups of the polyvinyl acetate side chain, initiating a nucleophilic substitution reaction. Simultaneously, the byproduct acetic acid (CH3COOH) generated by the reaction is immediately neutralized by the base. This not only removes the acidic substances that inhibit the reaction but also continuously shifts the chemical equilibrium towards the alcoholysis products, ensuring a high conversion rate. The key effect of this design is that it achieves precise control over the degree of alcoholysis, thereby enabling the customization of the hydrophilic-lipophilic balance of the viscosity reducer molecules as needed. This allows for flexible adaptation to heavy oils with different components, which is the core chemical basis for the innovative "adjuvant-dependent" function of this application.
[0039] In some embodiments, in step S104, the mass ratio of alcohol to double-bond modified graphene oxide is (5~10):4. Exemplarily, the mass ratio of alcohol to double-bond modified graphene oxide can be 5:4, 6:4, 7:4, 8:4, 9:4, or 10:4, or other values within the range of (5~10):4.
[0040] In step S104, the mass ratio of alcohol (such as methanol or ethanol) to double-bond modified graphene oxide is set at (5~10):4. The core principle is to precisely control the amount of alcohol added to regulate the degree of alcoholysis of the grafted polyvinyl acetate (PVAc) long chain. The reason for this ratio range is that the amount of alcohol, as both a reactant and a reagent, directly determines the driving force and depth of the transesterification reaction. When using a ratio close to the lower limit (e.g., 5:4), the amount of alcohol is relatively limited, mainly acting on the ester groups on the surface of the grafted chain, achieving partial alcoholysis. The product retains more hydrophobic acetate groups, suitable for heavy oils with high asphaltene content. When using a ratio close to the upper limit (e.g., 10:4), excess alcohol can more fully and deeply convert the ester groups, generating more hydrophilic hydroxyl groups, enhancing the hydrophilicity of the product, making it more suitable for heavy oil systems with high gum content or strong polarity. This ratio is fundamentally related to the performance of the preceding steps S101-S103: the amination density in step S101 and the double bond introduction efficiency in step S102 jointly determine the number of graftable PVAc chains (grafting density) in step S103, while the monomer feed ratio in step S103 determines the length of each grafted chain (total ester group). Therefore, the alcohol content ratio in S104 is actually a regulating valve designed for the total "stock" of ester groups that can be alcoholyzed, determined by the first three steps. This preferred range ensures that regardless of the grafting structure of the precursor (such as different chain lengths and densities), a specific value can be selected within this ratio range to achieve reliable and continuous control of the hydrophilic-lipophilic balance (HLB value) of the final viscosity reducer molecule. This systematically transforms the structural diversity of upstream synthesis into the broad adaptability of the end product performance, and is the core operating parameter for achieving the "one agent, multiple functions" technical effect.
[0041] In some other embodiments, in step S104, the reaction temperature of the alcoholysis reaction is 40°C to 60°C. Exemplarily, the reaction temperature of the alcoholysis reaction can be 40°C, 45°C, 50°C, 55°C, or 60°C, or other values within the range of 40°C to 60°C.
[0042] The alcoholysis reaction temperature in step S104 is set to 40℃~60℃. The core reason for this is that this range achieves the optimal balance between reaction efficiency, controllability and product structural stability: the reaction is mild at lower temperatures (such as 40℃), which is conducive to fine control of the alcoholysis process and avoids local over-reaction, and is suitable for preparing products with low degree of alcoholysis and high hydrophobicity; while higher temperatures (such as 60℃) can significantly improve the reaction rate and the diffusion and mass transfer efficiency of alcohol groups, promote the alcoholysis reaction to proceed to a deeper level, and are conducive to obtaining products with high degree of alcoholysis and strong hydrophilicity. This temperature range has a direct synergistic and complementary effect with the mass ratio of alcohol used in the same step: when the alcohol content is close to the lower limit (5:4), appropriately increasing the reaction temperature (e.g., towards 60℃) can compensate for the insufficient reactant concentration, ensuring sufficient reaction driving force by enhancing molecular kinetic energy; conversely, when the alcohol content is sufficient (10:4), using a slightly lower temperature (e.g., towards 40℃) can ensure a complete reaction while achieving smoother and more uniform control of the reaction process, avoiding product inhomogeneity due to excessively rapid reaction. Therefore, temperature and dosage together constitute a multi-dimensional "adjustment knob," which, through linkage and matching, can stably and repeatedly achieve various target products from partial alcoholysis to near-complete alcoholysis under a wide range of process conditions, thereby precisely controlling the final hydrophilic-lipophilic balance of the viscosity reducer and ensuring optimal compatibility with different heavy oil systems.
[0043] In a second aspect, this application also provides a heavy oil viscosity reducer prepared according to the preparation method described in any of the foregoing claims. This viscosity reducer uses graphene oxide nanosheets as its core, grafted with polymer chains that have undergone controlled alcoholysis. It combines the high specific surface area and high dispersibility of nanomaterials with the interfacial activity and tunable hydrophilicity / hydrophobicity of polymers, and has broad application prospects in the field of heavy oil viscosity reduction.
[0044] The heavy oil viscosity reducer provided in this application is the final product directly and necessarily obtained from the aforementioned four-step preparation method (amino functionalization modification, introduction of double bonds, polymerization grafting, and controlled alcoholysis). The core feature of this heavy oil viscosity reducer lies in its unique "core-shell" hybrid structure: a rigid two-dimensional core of graphene oxide nanosheets, with long polymer chains of precisely controlled alcoholysis grafted onto its surface via covalent bonds to form a flexible outer shell. This specific structure endows the product with a fundamental property that distinguishes it from conventional viscosity reducers—its molecular hydrophilic-lipophilic balance (HLB value) can be continuously and precisely adjusted through the key alcoholysis steps in the preparation process. Therefore, this product is not a single substance with a fixed composition, but rather a material system with customizable properties and a well-defined structure.
[0045] Example 1
[0046] 1. Amine functionalization of graphene oxide: 1.0 g of graphene oxide nanosheets were dissolved in 500 ml of pure water and ultrasonically dispersed for 10 minutes. 10 g of ethylenediamine was added while stirring, and the mixture was stirred at 30 °C for 6 hours to obtain the product. The product was then centrifuged. The precipitate was washed three times each with anhydrous ethanol and deionized water to obtain aminated graphene oxide.
[0047] 2. Introduce double bonds: 0.4 g of aminated graphene oxide was weighed and ultrasonically dispersed in 200 g of pure water. The mixture was then transferred to a 500 mL three-necked flask, and 4.0 g of acrylic acid was added. The mixture was then heated to 30 °C and stirred magnetically at 200 r / min for 1 h to allow the reaction to proceed fully. The product was obtained by centrifugation and washing three times with deionized water to obtain double-bond modified graphene oxide.
[0048] 3. Polymer grafting: Weigh 0.4 g of double-bond modified graphene oxide and ultrasonically disperse it in 200 g of pure water for 10 min. Then transfer it to a 500 mL three-necked flask, add 0.1 g of initiator (potassium persulfate), start stirring, and control the temperature at 40 °C. Then add 4 g of vinyl acetate dropwise to the three-necked flask. After all the acetate has been added, continue the reaction for another 30 min. After the reaction time is up, add 1.0 g of NaHCO3 to terminate the reaction.
[0049] 4. Alcohololysis: Add 2 g NaOH to the above mixed solution, maintain the temperature at 40℃, add 0.5 g methanol, and continue the reaction for 60 min to obtain a heavy oil viscosity reducer.
[0050] Example 2
[0051] 1. Amine functionalization of graphene oxide: 1.0 g of graphene oxide was dissolved in 500 ml of pure water and ultrasonically dispersed for 10 min. 11 g of propylenediamine was added while stirring, and the mixture was stirred at 30 °C for 6 h to obtain the product. The product was then centrifuged. The precipitate was washed three times each with anhydrous ethanol and deionized water to obtain aminated graphene oxide.
[0052] 2. Introduce double bonds: 0.4 g of aminated graphene oxide was weighed and ultrasonically dispersed in 200 g of pure water. Then, it was transferred to a 500 mL three-necked flask, 4.5 g of acrylic acid was added, and the temperature was raised to 30 °C. The mixture was then stirred magnetically at 200 r / min for 1 h to allow it to react fully and obtain the product. The product was centrifuged and washed three times with deionized water to obtain double-bonded modified graphene oxide.
[0053] 3. Polymer grafting: Weigh 0.4 g of double-bond modified graphene oxide and disperse it ultrasonically in 200 g of pure water for 10 min. Then transfer it to a 500 mL three-necked flask, add 0.1 g of initiator (potassium persulfate), start stirring, and control the temperature at 45 ℃. Then add 5 g of vinyl acetate dropwise to the three-necked flask. After all the acetate has been added, continue the reaction for another 30 min. After the reaction time is up, add 1.0 g of NaHCO3 to terminate the reaction.
[0054] 4. Alcohololysis: Add 2 g NaOH to the above mixed solution, maintain the temperature at 45℃, add 0.6 g methanol, and continue the reaction for 60 min to obtain a heavy oil viscosity reducer.
[0055] Example 3
[0056] 1. Amine functionalization of graphene oxide: 1.0 g of graphene oxide was dissolved in 500 ml of pure water and ultrasonically dispersed for 10 min. 12 g of butanediamine was added while stirring, and the mixture was stirred at 30 °C for 6 h to obtain the product. The product was then centrifuged. The precipitate was washed three times each with anhydrous ethanol and deionized water to obtain aminated graphene oxide.
[0057] 2. Introduce double bonds: 0.4 g of aminated graphene oxide was weighed and ultrasonically dispersed in 200 g of pure water. Then, it was transferred to a 500 mL three-necked flask, 5.0 g of acrylic acid was added, and the temperature was raised to 30 °C. The mixture was then stirred magnetically at 200 r / min for 1 h to allow it to react fully and obtain the product. The product was centrifuged and washed three times with deionized water to obtain double bond modified graphene oxide.
[0058] 3. Polymer grafting: Weigh 0.4 g of double-bond modified graphene oxide and ultrasonically disperse it in 200 g of pure water for 10 min. Then transfer it to a 500 mL three-necked flask, add 0.1 g of initiator (potassium persulfate), start stirring, and control the temperature at 50 ℃. Then add 6 g of vinyl acetate dropwise to the three-necked flask. After all the acetate has been added, continue the reaction for another 30 min. After the reaction time is up, add 1.0 g of NaHCO3 to terminate the reaction.
[0059] 4. Alcohololysis: Add 2g NaOH to the above mixed solution, maintain the temperature at 50℃, add 0.7g ethanol, and continue the reaction for 60min to obtain a heavy oil viscosity reducer.
[0060] Example 4
[0061] 1. Amine functionalization of graphene oxide: 1.0 g of graphene oxide was dissolved in 500 ml of pure water and ultrasonically dispersed for 10 min. While stirring, 13 g of pentanediamine was added, and the mixture was stirred at 30 °C for 6 h to obtain the product. The product was then centrifuged. The precipitate was washed three times each with anhydrous ethanol and deionized water to obtain aminated graphene oxide.
[0062] 2. Introduce double bonds: 0.4 g of aminated graphene oxide was weighed and ultrasonically dispersed in 200 g of pure water. Then, it was transferred to a 500 mL three-necked flask, 5.5 g of acrylic acid was added, and the temperature was raised to 30 °C. The mixture was then stirred magnetically at 200 r / min for 1 h to allow it to react fully and obtain the product. The product was centrifuged and washed three times with deionized water to obtain double bond modified graphene oxide.
[0063] 3. Polymer grafting: Weigh 0.4 g of double-bond modified graphene oxide and ultrasonically disperse it in 200 g of pure water for 10 min. Then transfer it to a 500 mL three-necked flask, add 0.1 g of initiator (potassium persulfate), start stirring, and control the temperature at 55 ℃. Then add 7 g of vinyl acetate dropwise to the three-necked flask. After all the acetate has been added, continue the reaction for another 30 min. After the reaction time is up, add 1.0 g of NaHCO3 to terminate the reaction.
[0064] 4. Alcohololysis: Add 2 g NaOH to the above mixed solution, maintain the temperature at 55 ℃, add 0.8 g ethanol, and continue the reaction for 60 min to obtain a heavy oil viscosity reducer.
[0065] Example 5
[0066] 1. Amine functionalization of graphene oxide: 1.0 g of graphene oxide was dissolved in 500 ml of pure water and ultrasonically dispersed for 10 min. While stirring, 14 g of hexamethylenediamine was added, and the mixture was stirred at 30 °C for 6 h to obtain the product. The product was then centrifuged. The precipitate was washed three times each with anhydrous ethanol and deionized water to obtain aminated graphene oxide.
[0067] 2. Introduce double bonds: 0.4 g of aminated graphene oxide was weighed and ultrasonically dispersed in 200 g of pure water. The mixture was then transferred to a 500 mL three-necked flask, and 6.0 g of acrylic acid was added. The mixture was then heated to 30 °C and stirred magnetically at 200 r / min for 1 h to allow the reaction to proceed fully. The product was obtained by centrifugation and washing three times with deionized water to obtain double-bond modified graphene oxide.
[0068] 3. Polymer grafting: Weigh 0.4 g of double-bond modified graphene oxide and ultrasonically disperse it in 200 g of pure water for 10 min. Then transfer it to a 500 mL three-necked flask, add 0.1 g of initiator (potassium persulfate), start stirring, and control the temperature at 60 ℃. Then add 8 g of vinyl acetate dropwise to the three-necked flask. After all the acetate has been added, continue the reaction for another 30 min. After the reaction time is up, add 1.0 g of NaHCO3 to terminate the reaction.
[0069] 4. Alcohololysis: Add 2 g NaOH to the above mixed solution, maintain the temperature at 60 ℃, add 0.9 g ethanol, and continue the reaction for 60 min to obtain a heavy oil viscosity reducer. Example 6
[0070] 1. Amine functionalization of graphene oxide: 1.0 g of graphene oxide was dissolved in 500 ml of pure water and ultrasonically dispersed for 10 min. While stirring, 15 g of hexamethylenediamine was added, and the mixture was stirred at 30 °C for 6 h to obtain the product. The product was then centrifuged. The precipitate was washed three times each with anhydrous ethanol and deionized water to obtain aminated graphene oxide.
[0071] 2. Introduce double bonds: 0.4 g of aminated graphene oxide was weighed and ultrasonically dispersed in 200 g of pure water. The mixture was then transferred to a 500 mL three-necked flask, and 4.0 g of acrylic acid was added. The mixture was then heated to 30 °C and stirred magnetically at 200 r / min for 1 h to allow the reaction to proceed fully. The product was obtained by centrifugation and washing three times with deionized water to obtain double-bond modified graphene oxide.
[0072] 3. Polymer grafting: Weigh 0.4 g of double-bond modified graphene oxide and ultrasonically disperse it in 200 g of pure water for 10 min. Then transfer it to a 500 mL three-necked flask, add 0.1 g of initiator (potassium persulfate), start stirring, and control the temperature at 60 ℃. Then add 8 g of vinyl acetate dropwise to the three-necked flask. After all the acetate has been added, continue the reaction for another 30 min. After the reaction time is up, add 1.0 g of NaHCO3 to terminate the reaction.
[0073] 4. Alcohololysis: Add 2 g NaOH to the above mixed solution, maintain the temperature at 60 ℃, add 1.0 g ethanol, and continue the reaction for 60 min to obtain a heavy oil viscosity reducer. Test Cases / Comparative Examples Test case Evaluation of viscosity reduction in heavy oil: Preparation of viscosity reducing agent solution: Add 180.0 g of target block simulated water to a 500 mL low-profile beaker, then add 20.0 g of the prepared graphene oxide nano viscosity reducing agent, and then use a vertical mechanical stirrer at 400 r / min for 60 min. After stirring evenly, an aqueous solution of graphene oxide nano viscosity reducing agent is obtained.
[0074] Viscosity Reduction Experiment: 30 g of the above-mentioned graphene oxide nano-viscosity reducer aqueous solution was added to a 250 mL beaker, followed by 70 g of dehydrated heavy oil. The constant temperature water bath was adjusted to 50℃, and the low-profile beaker was placed in the preheated water bath for 60 min. Then, a stirrer was placed in the low-profile beaker containing the above mixture, with the stirrer blades about 3 cm from the bottom of the beaker. Under the condition of maintaining a constant temperature in the low-profile beaker, the mixture was stirred at a speed of 300 r / min for 1 min to obtain the heavy oil O / W system. The rotor was completely immersed in the heavy oil O / W system, and the Brookfield viscometer was set to a speed of 6 r / min. The first apparent viscosity value was recorded at the 1st minute, and then recorded every 1 minute thereafter until the relative deviation of adjacent apparent viscosity values was less than 1%. The test was then stopped, and the arithmetic mean of adjacent data was taken as the experimental result.
[0075] Viscosity reduction results While numerous embodiments of this application have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will arise for those skilled in the art without departing from the spirit and intent of this application. It should be understood that various alternatives to the embodiments of this application described herein may be employed in the practice of this application. The appended claims are intended to define the scope of protection of this application and therefore cover equivalents or alternatives within the scope of these claims.
Claims
1. A method for preparing a heavy oil viscosity reducer based on graphene oxide nanosheets, characterized in that, Includes the following steps: S101, Amino-functionalized modification: Graphene oxide nanosheets are reacted with diamines to obtain amino-functionalized graphene oxide. S102. Introducing double bonds: The aminated graphene oxide is subjected to an amidation reaction with acrylic acid to obtain double bond modified graphene oxide. S103, Polymerization and Grafting: Under the action of an initiator, the double bond modified graphene oxide and vinyl acetate undergo a free radical polymerization reaction to obtain a graphene oxide graft product with long chains of polyvinyl acetate grafted on its surface. S104, Alcohololysis: The graphene oxide graft product is subjected to alcohololysis to obtain a heavy oil viscosity reducer.
2. The preparation method according to claim 1, characterized in that, In step S101, the diamine includes at least one of ethylenediamine, propylenediamine, butanediamine, pentanediamine, and hexanediamine.
3. The preparation method according to claim 2, characterized in that, In step S101, the mass ratio of the diamine to the graphene oxide nanosheets is (10~15):
1.
4. The preparation method according to claim 1, characterized in that, In step S102, the mass ratio of acrylic acid to aminated graphene oxide is (10~15):
1.
5. The preparation method according to claim 1, characterized in that, In step S103, The mass ratio of the vinyl acetate to the double-bond modified graphene oxide is (4~8):0.4; and / or, The reaction temperature for the free radical polymerization reaction is 40℃~60℃.
6. The preparation method according to claim 1, characterized in that, In step S103, The initiator is potassium persulfate; and / or Sodium bicarbonate was added after the free radical polymerization reaction to adjust the graphene oxide graft product to be neutral.
7. The preparation method according to claim 1, characterized in that, In step S104, The alcohols used for alcoholysis include methanol or ethanol; and / or The alcoholysis reaction is carried out under alkaline conditions.
8. The preparation method according to claim 7, characterized in that, In step S104, the mass ratio of the alcohol to the double-bond modified graphene oxide is (5~10):
4.
9. The preparation method according to claim 1 or 8, characterized in that, In step S104, the reaction temperature of the alcoholysis reaction is 40℃~60℃.
10. A heavy oil viscosity reducer prepared by the preparation method according to any one of claims 1-9.