Dendrimer composition for preventing gas channeling and carbon sequestration, hydrogel and preparation method and application thereof

Abstract

The invention discloses a dendritic macromolecular composition for gas channeling prevention and underground carbon sequestration, hydrogel as well as a preparation method and application of the dendritic macromolecular composition. The dendritic macromolecule composition is prepared from the following components in percentage by weight: 0.06 to 0.4 percent of dendritic macromolecules; 0.8-1.6 wt% of sodium carboxymethyl cellulose, and the balance of water. The dendritic macromolecules are at least one of second-generation and third-generation dendritic macromolecules prepared from ester monomers and amine monomers through iterative Michael addition reaction by taking amino-terminated dendritic macromolecules as cores; the ester monomer is methyl acrylate; the amine monomer is selected from one of tris (2-aminoethyl) amine, diethyltriamine and triethyltetramine. CO2 is introduced into the composition to form hydrogel with a three-dimensional network structure, the hydrogel has high-density active sites, and the reaction efficiency with CO2 can be remarkably improved, so that long-term channeling sealing and carbon sequestration performance is exerted in the CO2-EOR process, the problem of oil displacement efficiency reduction caused by gas channeling is relieved, and blocking-sealing integrated carbon sequestration is realized.

Description

Dendritic macromolecular compositions, hydrogels, their preparation methods, and applications for preventing gas channeling and carbon fixation Technical Field

[0001] This invention belongs to the field of intelligent water-soluble polymers, specifically relating to the preparation of a CO2-thickening reversible dendritic macromolecular hydrogel and its application in the field of carbon capture and carbon sequestration. Background Technology

[0002] CO2-enhaced oil recovery (CO2-EOR) is a technology that can both enhance oil recovery and achieve carbon sequestration. This technology injects CO2 into oil wells, simultaneously increasing oil recovery and storing the CO2 underground, perfectly unifying oil displacement and carbon fixation. However, due to formation heterogeneity and the presence of fractures, injected CO2 often channels through high-permeability channels or fractures, reducing its oil displacement and sequestration efficiency. In recent years, the advent of CO2 thickening polymers has offered hope for solving this problem. CO2 thickening polymers are smart materials whose aqueous solutions can transform from low viscosity to high viscosity or gel after absorbing CO2. However, currently reported CO2 thickening polymers generally suffer from limited carbon sequestration and insufficient gel strength, and their simple molecular structures make it difficult to control their performance through structural design, thus hindering their long-term carbon sequestration and sealing performance in the CO2-EOR process. Therefore, there is an urgent need to develop a superior carbon sequestration material that can absorb CO2 and undergo a solution-to-gel transformation.

[0003] Therefore, developing a CO2-responsive dendritic macromolecular gel that combines multiple active sites, high CO2 response efficiency, and excellent stability is not only of significant scientific research value but also has remarkable engineering application prospects. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem of insufficient CO2 sequestration rate in existing CO2 flooding and storage technologies, and to provide a dendritic macromolecular composition, hydrogel, preparation method and application for preventing gas channeling and underground carbon sequestration, thereby exerting long-term channeling prevention and carbon sequestration performance in CO2-EOR process, alleviating the problem of reduced oil displacement efficiency caused by gas channeling, and realizing a new carbon sequestration paradigm of "blocking-storage" integration.

[0005] The dendritic macromolecular composition for preventing gas channeling and underground carbon sequestration described in this invention, namely a CO2-responsive composition, has the following components and their mass contents: 0.06%~0.4wt% dendritic macromolecules; 0.8%~1.6wt% sodium carboxymethyl cellulose (NaCMC); and the balance being water; the sum of the weight percentages of each component is 100%.

[0006] The dendritic macromolecule is a dendritic polyamine compound formed generation by generation through iterative Michael addition reactions between ester compounds and amine compounds, and through aminolysis reactions, with the core being tris(2-aminoethyl)amine; the ester compound is methyl acrylate; and the amine compound is selected from at least one of tris(2-aminoethyl)amine, diethylenetriamine, and triethylenetetramine.

[0007] This invention, through experimental comparison, reveals that the generation of dendritic macromolecules plays a decisive role in their performance. The first-generation (G1) system, when combined with NaCMC, lacks CO2-responsive thickening ability; while the second-generation (G2) and third-generation (G3) systems both exhibit significant in-situ gelation. Among these, the G3 system performs best, exhibiting the highest CO2 absorption (21.53 mg CO2·g) under high temperature and pressure (45℃, 10 MPa). -1 Therefore, the dendritic macromolecule is at least one of the second-generation (G2) and third-generation (G3) dendritic macromolecules. The second-generation dendritic macromolecules, depending on the amine compound, include three variants, denoted as SCUG2S, SCUG2D, and SCUG2T, respectively. Their terminal functional groups are amino groups, introduced by at least one of the terminal amines diethylenetriamine, triethylenetetramine, and tris(2-aminoethyl)amine. The first-generation dendritic macromolecule is denoted as SCUG1, and the third-generation dendritic macromolecule is denoted as SCUG3. SCUG1 and SCUG2S are synthesized according to literature reports, while SCUG2D, SCUG2T, and SCUG3 are designed and synthesized in this invention.

[0008] The above composition is further prepared by the following method: (1) Synthesizing the semi-generation product: The previous generation amino-terminated dendritic macromolecule is dissolved in methanol, and methyl acrylate is added dropwise under nitrogen protection at 0~5℃. The molar ratio of methyl acrylate to dendritic macromolecule is 1:(25~40). After reacting at 0~5℃ for 0.5~1.5h, the temperature is raised to room temperature and the reaction continues for about 55~65h. The solvent and excess monomer are removed by rotary evaporation under reduced pressure to obtain the semi-generation product.

[0009] (2) Synthesis of the full-generation product: The semi-generation product was dissolved in methanol, and an amine compound was added dropwise under nitrogen protection at 0-5℃. The molar ratio of the amine compound to the semi-generation product was 1:(40-60). The reaction was carried out at 0-5℃ for 0.5-1.5 h, and then the reaction was continued at room temperature for about 6-8 days (1 day is 24 h). Subsequently, the solvent was removed under reduced pressure, and the excess polyamine was removed by azeotropic distillation with a toluene:methanol volume ratio of 90:10. If necessary, the product was washed with anhydrous diethyl ether and dried under vacuum to obtain amino-terminated dendritic macromolecules.

[0010] The amine compound is selected from tri(2-aminoethyl)amine, diethylenetriamine, and triethylenetetramine. The amine monomer is terminally tri(2-aminoethyl)amine to obtain SCUG2S; terminal amine is diethylenetriamine to obtain SCUG2D; terminal amine is triethylenetetramine to obtain SCUG2T; and further iteration based on the second generation, with tri(2-aminoethyl)amine end-capping, yields SCUG3.

[0011] In the above composition, the mass ratio of sodium carboxymethyl cellulose (NaCMC) to dendritic macromolecules is 1:(0.002~0.003), preferably 1:0.002.

[0012] When CO2 is introduced into the mixture, it dissolves in water to form carbonic acid. A large number of amino groups in the dendritic macromolecules are protonated, forming positively charged cationic quaternary ammonium salts. Sodium carboxymethyl cellulose contains numerous anionic carboxylate groups, which can electrostatically interact (associate) with the cationic quaternary ammonium salts. At this point, the dendritic macromolecules act as "cationic crosslinking agents," forming a three-dimensional crosslinked network. This macroscopically manifests as an increase in viscosity, achieving a transformation from solution to gel. This three-dimensional network structure and high-density active sites significantly enhance the reaction efficiency with CO2.

[0013] This invention presents a dendritic macromolecular composition that achieves an innovative technical approach integrating "dynamic plugging-in-situ carbon sequestration" through multifunctional integration at the molecular level. Its core mechanism lies in the synergistic effect of plugging and carbon sequestration: the gel utilizes the nanoscale size and adjustable stiffness of dendritic macromolecules to preferentially enter and plug high-permeability channels, forcing CO2 to migrate and diffuse towards low-permeability regions; simultaneously, its high-density amino groups on the surface can rapidly chemically bond with CO2, converting free CO2 into a stable chemically bound state. This technological breakthrough not only effectively alleviates the problem of decreased oil displacement efficiency caused by gas channeling but also constructs a novel integrated "plugging-storage" carbon sequestration paradigm, providing a more reliable technical solution for carbon sequestration in oil and gas reservoirs.

[0014] The present invention provides a method for preparing the above-mentioned dendritic macromolecular composition, comprising the following steps: (1) dissolving NaCMC and inorganic salt (if present) in water and shearing and dispersing at a rate of 800-1200 rpm for 20-30 minutes to form a homogeneous aqueous phase; (2) injecting dendritic macromoleculars into the aqueous phase at a mass ratio of NaCMC to dendritic macromoleculars of 1:(0.002-0.003), stirring at room temperature (200-300 rpm) for 20-30 minutes to obtain a mixture.

[0015] The mixture is in a solution state. CO2 is introduced into the mixture for cross-linking for 20 minutes to form a three-dimensional network structure.

[0016] In the above method, the dendritic macromolecule is further prepared by an iterative Michael addition reaction of an ester compound and an amine compound; the ester monomer is methyl acrylate; and the amine monomer is selected from tris(2-aminoethyl)amine, diethylenetriamine, or triethylenetetramine.

[0017] In the above method, further, to simulate the composition of formation water, the aqueous phase in step (1) may also contain inorganic salts. The inorganic salts are at least one of sodium chloride, sodium carbonate, sodium bicarbonate, and magnesium chloride.

[0018] In the above method, the water is preferably deionized water.

[0019] The present invention also provides a dendritic macromolecular hydrogel, which is obtained by introducing CO2 into a mixed solution of the above-mentioned dendritic macromolecular composition.

[0020] The present invention also provides the application of the above-mentioned dendritic macromolecular composition in preventing gas channeling and plugging leaks during CO2 oil displacement.

[0021] The present invention also provides the application of the above-described dendritic macromolecular composition in carbon capture and storage. Further, it provides its application in underground carbon sequestration.

[0022] The present invention also provides dendritic macromolecules prepared by the above method, wherein the preparation method is the same as the preparation method of dendritic macromolecules in the composition.

[0023] This invention also provides the combined application of the above-mentioned dendritic macromolecules and sodium carboxymethyl cellulose in preventing gas channeling and underground carbon sequestration.

[0024] Compared with existing technologies, the present invention has the following beneficial effects: 1. The dendritic macromolecular composition of the present invention, with its three-dimensional topological structure, synergistically enhances the effect with NaCMC. Through iterative molecular design, the number of terminal amino groups of the dendritic macromolecular structure increases exponentially compared with traditional small molecule amines. The three-dimensional network surface has a high density of amino sites, which can directly react with CO2 and undergo protonation, further inducing strong electrostatic interactions within the gel, causing a significant increase in the viscosity of the system. This allows for the efficient capture of more CO2 molecules through spatial confinement, resulting in a CO2 absorption efficiency significantly superior to similar PEI solutions. This mechanism achieves synergistic enhancement of both carbon fixation and sealing functions, effectively sealing high-permeability channels, assisting CO2 in displacing crude oil from low-permeability channels, improving oil recovery while simultaneously increasing CO2 underground storage rate, achieving highly efficient synergy between CO2 oil displacement and storage processes.

[0025] 2. The dendritic macromolecular gel provided by the present invention not only has excellent CO2 absorption performance, but also can achieve intelligent response through CO2 triggering, thereby forming a gel to seal the pores of underground reservoirs.

[0026] 3. The dendritic macromolecular composition structure described in this invention can be customized to adapt to complex geological formations. By controlling the generation number of the dendritic macromolecules (G1-G3) and adjusting the NaCMC concentration (0.8~1.6wt%), the gel mechanical properties can be designed in a directional manner, and the gel viscosity (500~100000 mPa·s) can be enhanced.

[0027] 4. The method described in this invention has mild reaction conditions, low raw material costs, and the resulting dendritic macromolecules can be directly dissolved in water for application without post-processing, which is beneficial for large-scale production and application. Attached Figure Description

[0028] Figure 1 shows the infrared spectrum of SCUG2T prepared in Example 3.

[0029] Figure 2 shows the NMR spectrum of SCUG2T prepared in Example 3.

[0030] Figure 3 shows the infrared spectrum of SCUG2D prepared in Example 4.

[0031] Figure 4 shows the NMR spectrum of SCUG2D prepared in Example 4.

[0032] Figure 5 shows the infrared spectrum of SCUG3 prepared in Example 5.

[0033] Figure 6 shows the NMR spectrum of SCUG3 prepared in Example 5.

[0034] Figure 7 shows the dynamic viscoelastic behavior of the SCUG1 / NaCMC composite solution after CO2 is introduced.

[0035] Figure 8 shows the viscosity of the SCUG1 / NaCMC composite solution before and after CO2 saturation as a function of shear rate.

[0036] Figure 9 shows the dynamic viscoelastic behavior of the SCUG2S / NaCMC composite system under CO2 stimulation.

[0037] Figure 10 shows the viscosity of the SCUG2S / NaCMC composite solution before and after CO2 saturation as a function of shear rate.

[0038] Figure 11 shows the dynamic viscoelastic behavior of the SCUG2T / NaCMC composite solution after CO2 is introduced.

[0039] Figure 12 shows the viscosity of the SCUG2T / NaCMC composite solution before and after CO2 saturation as a function of shear rate.

[0040] Figure 13 shows the dynamic viscoelastic behavior of the SCUG2D / NaCMC composite solution after CO2 is introduced.

[0041] Figure 14 shows the viscosity of the SCUG2D / NaCMC composite solution as a function of shear rate before and after CO2 saturation.

[0042] Figure 15 shows the dynamic viscoelastic behavior of the SCUG3 / NaCMC composite solution after CO2 is introduced.

[0043] Figure 16 shows the viscosity of the SCUG3 / NaCMC composite solution before and after CO2 saturation as a function of shear rate.

[0044] Figure 17 shows the CO2 absorption curve of the SCUG / NaCMC composite solution at 45℃ and 10MPa.

[0045] Figure 18 shows the chemical structural formulas of five dendritic macromolecules of SCUG (a, b, c, d, and e are SCUG1, SCUG2S, SCUG2D, SCUG2T, and SCUG3, respectively).

[0046] Figure 19 is a comparison of the pressure difference changes in the water and SCUG2S system during CO2 displacement. Detailed Implementation

[0047] The present invention will be further illustrated below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above-described invention, and these improvements and adjustments still fall within the scope of protection of the invention.

[0048] Example 1 This example provides a method for preparing the first-generation dendritic macromolecule SCUG1. The synthetic route includes the following two steps: Step 1: Synthesis of the semi-generation product (G0.5). In a 250 mL round-bottom flask, 4.3872 g (30 mmol) of tris(2-aminoethyl)amine (TAEA) was dissolved in 25 mL of methanol. The reaction system was placed in an ice-water bath at 0-5°C and stirred under a nitrogen atmosphere. A 25 mL methanol solution containing 19.37 g (225 mmol) of methyl acrylate was slowly added dropwise using a constant-pressure dropping funnel. After the addition was complete, the reaction was continued at 0-5°C for 1 hour. Subsequently, the reaction system was removed from the ice bath, allowed to naturally warm to room temperature (25°C), and stirred for 48 hours to ensure the Michael addition reaction was complete. Thin-layer chromatography (TLC) was used to monitor the reaction until the starting material spot disappeared. After the reaction was completed, excess reagents and solvents were removed by rotary evaporation at a temperature below 40°C under reduced pressure to obtain a colorless oily product, which was designated as the first-generation semi-generation product SCUG0.5 (or G0.5).

[0049] Step 2: Synthesis of the first-generation fully metabolized product (SCUG1). In a 250 mL round-bottom flask, the product SCUG0.5 (2.17 g, 3.3 mmol) obtained in the previous step was dissolved in 20 mL of methanol. The reaction system was placed in an ice-water bath at 0–5°C and stirred under a nitrogen atmosphere. A 20 mL methanol solution containing 5.8 g (39.6 mmol) of tris(2-aminoethyl)amine (TAEA) was slowly added dropwise using a constant-pressure dropping funnel. After the addition was complete, the reaction was continued at 0–5°C for 1 hour. The ice bath was then removed, and the reaction system was heated to room temperature (25°C) and stirred continuously for 7 days. The complete disappearance of the ester characteristic peaks was confirmed by ¹H NMR spectroscopy. After the reaction was complete, methanol was removed under reduced pressure using a rotary evaporator. Subsequently, excess tris(2-aminoethyl)amine was removed by azeotropic distillation using a toluene-methanol azeotropic mixture (90:10 v / v). Finally, residual toluene was removed by azeotropic distillation with methanol, and the remaining methanol was removed under vacuum to obtain the first-generation amino-terminated dendritic macromolecule, denoted as the final product SCUG1 (or G1.0).

[0050] The first-generation dendritic macromolecule SCUG1 was successfully prepared using the two-step synthesis method described above. Its structure is consistent with the target molecular formula and can be used for subsequent performance comparison studies.

[0051] Example 2, Step 1: Synthesis of the semi-generation product (G0.5), using tris(2-aminoethyl)amine as the central molecule, dissolved in an appropriate amount of methanol, placed in an ice-water bath at 0-5°C and stirred under a nitrogen atmosphere. Methyl acrylate was slowly added dropwise using a constant-pressure dropping funnel. After the addition was complete, the reaction was continued at 0-5°C for 1 hour. Subsequently, the reaction system was removed from the ice bath, naturally heated to room temperature (25°C), and stirred for 48 hours to ensure the Michael addition reaction was complete. Thin-layer chromatography (TLC) was used to monitor until the starting material spot disappeared. After the reaction was completed, excess reagents and solvents were removed by rotary evaporation under reduced pressure at below 40°C to obtain a pale yellow viscous liquid (first-generation ester-terminated dendritic molecule, denoted as product G0.5).

[0052] Step 2: Synthesize the first-generation full-form product (G1.0). Using the previously obtained product G0.5 as the base, dissolve it in an appropriate amount of methanol and place it in an ice-water bath at 0-5°C with stirring under a nitrogen atmosphere. Slowly add tris(2-aminoethyl)amine. After the addition is complete, continue the reaction at 0-5°C for 1 hour. Then remove the ice bath, raise the reaction system to room temperature (25°C), and continue stirring for 7 days, monitoring by TLC until the starting material spot completely disappears. After the reaction is complete, transfer the reaction solution to a dialysis bag with a molecular weight cutoff of 1000 Da and dialyze against deionized water for 3 days, changing the water every 12 hours. Finally, freeze-dry the dialyzed solution to obtain a white flocculent solid (first-generation amino-terminated dendritic macromolecule, denoted as product G1.0).

[0053] Step 3: Synthesize the semi-generation product (G1.5). Using product G1.0 as the center, dissolve it in an appropriate amount of methanol and place it in an ice-water bath at 0-5°C with stirring under a nitrogen atmosphere. Slowly add methyl acrylate dropwise. After the addition is complete, continue the reaction at 0-5°C for 1 hour. Then remove the ice bath, raise the reaction system to room temperature (25°C), and continue stirring for 60 hours, monitoring by TLC until the starting material disappears. After the reaction is complete, use a rotary evaporator at below 40°C under reduced pressure to remove excess reagents and solvent, obtaining a pale yellow viscous liquid (denoted as product G1.5).

[0054] Step 4: Synthesize the second-generation full-form product (G2.0). Using product G1.5 as the center, dissolve it in an appropriate amount of methanol and place it in an ice-water bath at 0-5°C with stirring under a nitrogen atmosphere. Slowly add tris(2-aminoethyl)amine. After the addition is complete, continue the reaction at 0-5°C for 1 hour. Then remove the ice bath, raise the reaction system to room temperature (25°C), and continue stirring for 7 days, monitoring by TLC until the starting material spot completely disappears. After the reaction is complete, transfer the reaction solution to a dialysis bag with a molecular weight cutoff of 1000 Da and dialyze against deionized water for 4 days, changing the water every 12 hours. Finally, freeze-dry the dialyzed solution to obtain a yellow viscous liquid (second-generation amino-terminated dendritic macromolecule, denoted as the final product SCUG2S).

[0055] Subsequently, a dendritic macromolecular hydrogel was prepared: 0.2 wt% of dendritic macromolecules, 1.0 wt% of NaCMC, 0.45 wt% of inorganic salts and 98.45 wt% of water were weighed by weight percentage; the inorganic salts were first dissolved in deionized water, and then sodium carboxymethyl cellulose (NaCMC) was slowly added while stirring. After it was completely dissolved to form a homogeneous and transparent solution, the dendritic macromolecules were added, and stirring was continued until the mixture was homogeneous.

[0056] Example 3 This example provides a method for preparing the second-generation dendritic macromolecule SCUG2T using triethylenetetramine as the terminal reagent. The synthetic route includes the following four steps: Step 1: Synthesize the semi-generation product (G1.5) using G1 from Example 1. In a 250 mL round-bottom flask, 3.41 g (1 mmol) of the first-generation full-generation product G1.0 (prepared from Example 1) was dissolved in 20 mL of methanol. The reaction system was placed in an ice-water bath at 0-5°C and stirred under a nitrogen atmosphere. A 5 mL methanol solution containing 2.84 g (33.0 mmol) of methyl acrylate was slowly added dropwise using a constant-pressure dropping funnel. After the addition was complete, the reaction was continued at 0-5°C for 1 hour. Subsequently, the reaction system was removed from the ice bath, allowed to naturally warm to room temperature (25°C), and stirred for 60 hours. Thin-layer chromatography (TLC) was used to monitor the reaction until the starting material spot disappeared. After the reaction was completed, excess reagents and solvents were removed by rotary evaporation at a temperature below 40°C and under reduced pressure, yielding a pale yellow viscous liquid, which is the first-generation half-generation product, denoted as product G1.5.

[0057] Step 2: Synthesis of the second-generation full-generation product (SCUG2T). In a 250 mL round-bottom flask, the product G1.5 (3.41 g, 1 mmol) obtained in the previous step was dissolved in 20 mL of methanol. The reaction system was placed in an ice-water bath at 0–5°C and stirred under a nitrogen atmosphere. A 20 mL methanol solution containing 7.01 g (48 mmol) of triethylenetetramine was slowly added dropwise using a constant-pressure dropping funnel. After the addition was complete, the reaction was continued at 0–5°C for 1 hour. Subsequently, the ice bath was removed, and the reaction system was heated to room temperature (25°C) and stirred continuously for 7 days, monitored by TLC until the starting material spot completely disappeared. After the reaction was completed, most of the solvent was removed using a rotary evaporator under reduced pressure. Subsequently, excess triethylenetetramine was removed by azeotropic distillation using a toluene-methanol azeotropic mixture (90:10 v / v). The crude product was washed twice with anhydrous diethyl ether for further purification, yielding a highly viscous liquid. Finally, the residual ether was removed under vacuum to obtain a light yellow viscous liquid, which is the second-generation amino-terminal dendritic macromolecule, denoted as the final product SCUG2T.

[0058] No characteristic peaks (δ ≈ 3.6 ppm) or olefin proton signals were observed in the 1H NMR spectrum, and the dominant peak was the ortho-methylene peak of the amine in the 2.3–3.4 ppm region, indicating that the ester terminal group had been completely amination-dissociated and a polyamine dendritic structure had been successfully constructed. The infrared spectrum showed peaks in the 3200–3500 cm⁻¹ region. -1 A broad N–H stretching vibration peak appears at ~1650 cm⁻¹, and extends to ~1650 cm⁻¹. -1 It exhibits a distinct characteristic absorption of amide C=O at ~1730 cm⁻¹, but no absorption was detected at ~1730 cm⁻¹. -1The presence of the ester carbonyl peak further confirms that the intermediate has been completely transformed. The NMR and IR results corroborate each other, verifying the successful synthesis of the second-generation dendritic macromolecule SCUG2T, whose terminal functional group is triethylenetetramine. Its structure matches the target molecular formula and can be used for subsequent preparation and performance studies of composite gels.

[0059] Subsequently, a dendritic macromolecular hydrogel was prepared: 0.2 wt% of dendritic macromolecules, 1.0 wt% of NaCMC, 0.45 wt% of inorganic salts and 98.45 wt% of water were weighed by weight percentage; the inorganic salts were first dissolved in deionized water, and then sodium carboxymethyl cellulose (NaCMC) was slowly added while stirring. After it was completely dissolved to form a homogeneous and transparent solution, the dendritic macromolecules were added, and stirring was continued until the mixture was homogeneous.

[0060] Example 4 This example provides a method for preparing the second-generation dendritic macromolecule SCUG2D using diethylenetriamine as the terminal reagent. The synthetic route includes the following steps: Step 1: Synthesis of the semi-generation product (G1.5). In a 250 mL round-bottom flask, 3.41 g (1 mmol) of the first-generation full-generation product G1.0 (prepared in Example 1) was dissolved in 20 mL of methanol. The reaction system was placed in an ice-water bath at 0-5°C and stirred under a nitrogen atmosphere. A 5 mL methanol solution containing 2.84 g (33.0 mmol) of methyl acrylate was slowly added dropwise using a constant-pressure dropping funnel. After the addition was complete, the reaction was continued at 0-5°C for 1 hour. Subsequently, the reaction system was removed from the ice bath, allowed to naturally warm to room temperature (25°C), and stirred for 60 hours. Thin-layer chromatography (TLC) was used to monitor the reaction until the starting material spot disappeared. After the reaction was completed, excess reagents and solvents were removed by rotary evaporation at a temperature below 40°C and under reduced pressure, yielding a pale yellow viscous liquid, which is the first-generation half-generation product, denoted as product G1.5.

[0061] Step 2: Synthesis of the second-generation full-generation product (SCUG2D). In a 250 mL round-bottom flask, the product G1.5 (3.41 g, 1 mmol) obtained in the previous step was dissolved in 20 mL of methanol. The reaction system was placed in an ice-water bath at 0–5°C and stirred under a nitrogen atmosphere. A 20 mL methanol solution containing 4.94 g (48 mmol) of diethylenetriamine was slowly added dropwise using a constant-pressure dropping funnel. After the addition was complete, the reaction was continued at 0–5°C for 1 hour. Subsequently, the ice bath was removed, and the reaction system was heated to room temperature (25°C) and stirred continuously for 7 days, monitored by TLC until the starting material spot completely disappeared. After the reaction was completed, most of the solvent was removed using a rotary evaporator under reduced pressure. Subsequently, excess diethylenetriamine was removed by azeotropic distillation using a toluene-methanol azeotropic mixture (90:10 v / v). The crude product was washed twice with anhydrous diethyl ether for further purification, yielding a highly viscous liquid. Finally, the residual ether was removed under vacuum to obtain a light yellow viscous liquid, which is the second-generation amino-terminal dendritic macromolecule, denoted as the final product SCUG2D.

[0062] Infrared spectroscopy and proton nuclear magnetic resonance (NMR) spectroscopy (see Figures 3 and 4) revealed no characteristic signals of ester methoxy groups or unsaturated olefin protons in the proton NMR spectrum, indicating that the ester intermediate had undergone complete aminolysis and formed a stable polyamine structure. The infrared spectrum showed a distinct amino stretching vibration absorption peak in the 3200–3500 cm⁻¹ region and a characteristic absorption peak of the amide bond at approximately 1650 cm⁻¹, while no characteristic absorption of the ester carbonyl group was observed. These NMR and infrared analysis results corroborate each other, proving that the second-generation dendritic macromolecule SCUG2D, terminated with diethylenetriamine, has been successfully synthesized. Its structure matches the target molecular formula and can be used for subsequent preparation and performance studies of composite gels.

[0063] Subsequently, a dendritic macromolecular hydrogel was prepared: 0.2 wt% of dendritic macromolecules, 1.0 wt% of NaCMC, 0.45 wt% of inorganic salts and 98.45 wt% of water were weighed by weight percentage; the inorganic salts were first dissolved in deionized water, and then sodium carboxymethyl cellulose (NaCMC) was slowly added while stirring. After it was completely dissolved to form a homogeneous and transparent solution, the dendritic macromolecules were added, and stirring was continued until the mixture was homogeneous.

[0064] Example 5 This example provides a method for preparing the third-generation dendritic macromolecule SCUG3. The synthetic route is an iterative improvement upon the second-generation method, comprising the following two steps: Step 1: Synthesis of the semi-generation product (G2.5). In a 250 mL round-bottom flask, 2.54 g (1.1 mmol) of the second-generation full-generation product G2.0S (prepared in Example 1) was dissolved in 5 mL of methanol. The reaction system was placed in an ice-water bath at 0-5°C and stirred under a nitrogen atmosphere. A 5 mL methanol solution containing 2.84 g (33.0 mmol) of methyl acrylate was slowly added dropwise using a constant-pressure dropping funnel. After the addition was complete, the reaction was continued at 0-5°C for 1 hour. Subsequently, the reaction system was removed from the ice bath, allowed to naturally warm to room temperature (25°C), and stirred for 60 hours. Thin-layer chromatography (TLC) was used to monitor the reaction until the starting material spot disappeared. After the reaction was completed, excess reagents and solvents were removed by rotary evaporation at a temperature below 40°C and under reduced pressure to obtain a yellow oily product, which is the second-generation half-generation product, denoted as product G2.5.

[0065] Step 2: Synthesis of the third-generation fully metabolized product (SCUG3). In a 250 mL round-bottom flask, the product G2.5 (4.37 g, 1 mmol) obtained in the previous step was dissolved in 20 mL of methanol. The reaction system was placed in an ice-water bath at 0–5°C and stirred under a nitrogen atmosphere. A 40 mL methanol solution containing 14.04 g (96 mmol) of tris(2-aminoethyl)amine was slowly added dropwise using a constant-pressure dropping funnel. After the addition was complete, the reaction was continued at 0–5°C for 1 hour. Subsequently, the ice bath was removed, and the reaction system was heated to room temperature (25°C) and stirred continuously for 7 days, monitored by TLC until the starting material spot completely disappeared. After the reaction was completed, most of the solvent was removed using a rotary evaporator under reduced pressure. Subsequently, excess tris(2-aminoethyl)amine was removed by azeotropic distillation using a toluene-methanol azeotropic mixture (90:10 v / v). The crude product was washed twice with anhydrous diethyl ether for further purification, yielding a highly viscous liquid. Finally, the residual ether was removed under vacuum to obtain a light yellow viscous liquid, which is the third-generation amino-terminal dendritic macromolecule, denoted as the final product SCUG3.

[0066] The 1H NMR spectrum showed a dominant signal from the ortho-methylene group of the amine, with no characteristic peaks related to ester groups or unsaturated bonds, indicating that the ester units were completely converted during the reaction. The IR spectrum showed a broad and continuous absorption peak of amino stretching vibrations, accompanied by obvious characteristic absorption of amide bonds, indicating that the polyamine-type dendritic structure had been stably formed. Based on these characterization results, it can be confirmed that the third-generation dendritic macromolecule SCUG3 was successfully synthesized according to the expected structure. This high-generation dendritic molecule has more terminal functional groups and can be used for the preparation and research of subsequent high-performance composite gels.

[0067] Subsequently, a dendritic macromolecular hydrogel was prepared: 0.2 wt% of dendritic macromolecules, 1.0 wt% of NaCMC, 0.45 wt% of inorganic salts and 98.45 wt% of water were weighed by weight percentage; the inorganic salts were first dissolved in deionized water, and then sodium carboxymethyl cellulose (NaCMC) was slowly added while stirring. After it was completely dissolved to form a homogeneous and transparent solution, the dendritic macromolecules were added, and stirring was continued until the mixture was homogeneous.

[0068] Example 6 This example measures the CO2 thickening properties of dendritic macromolecular compositions of different generations prepared by the method described in this invention.

[0069] Experimental Methods: The dendritic macromolecules (SCUG1, SCUG2S, SCUG2T, SCUG2D, SCUG3) obtained in Examples 1 to 5 were respectively compounded with NaCMC to prepare aqueous solutions with a mass concentration of 1 wt% NaCMC / 0.2 wt% SCUG. Using an Anton Paar MCR302 rotational rheometer, the steady-state rheological (viscosity as a function of shear rate) and dynamic rheological (storage modulus G' and loss modulus G'' as a function of frequency / strain) curves of each system before and after the introduction of CO2 were measured at 45 ºC.

[0070] Results and Analysis: 1. SCUG1 / NaCMC System: As shown in Figure 7, in an aqueous solution without CO2, the SCUG1 / NaCMC composite solution exhibits typical Newtonian fluid behavior, with its viscosity not changing significantly with shear rate. After introducing CO2, the rheological properties of the system did not change significantly, and the viscosity did not increase by an order of magnitude. Figure 8 shows that the storage modulus (G') in the dynamic rheological test was always lower than the loss modulus (G''), indicating that the system failed to form a three-dimensional gel network. This result suggests that the first-generation dendritic macromolecules, due to their limited number of functional groups, have weak electrostatic crosslinking with NaCMC and do not possess significant CO2 thickening ability.

[0071] 2. SCUG2S / NaCMC System: As observed in Figures 9 and 10, the SCUG2S / NaCMC system underwent a fundamental transformation after CO2 introduction. Steady-state rheological tests showed that its zero-shear viscosity increased by several orders of magnitude, exhibiting significant shear-thinning behavior, a characteristic of typical soft gels. Dynamic rheological tests further confirmed that after CO2 introduction, the storage modulus (G') of the system exceeded the loss modulus (G'') across the entire testing frequency range, confirming the successful construction of the elastic gel network. This result indicates that second-generation dendritic macromolecules possess effective CO2-responsive thickening capabilities.

[0072] 3. SCUG2T / NaCMC and SCUG2D / NaCMC systems: The results in Figures 11 and 12 show that both the SCUG2T and SCUG2D systems exhibit similar gelation behavior to SCUG2S under CO2 stimulation, with significant increases in viscosity and modulus, successfully achieving a sol-gel transition. This demonstrates that the CO2-responsive thickening ability of second-generation dendritic macromolecules has a certain degree of universality for its terminal amine group types (triethylenetetramine and diethylenetriamine).

[0073] 4. SCUG2D / NaCMC and SCUG2D / NaCMC Systems: The results in Figures 13 and 14 show that both the SCUG2T and SCUG2D systems exhibit similar gelation behavior to SCUG2S under CO2 stimulation, with significant increases in viscosity and modulus, successfully achieving a sol-gel transition. This demonstrates that the CO2-responsive thickening ability of second-generation dendritic macromolecules has a certain degree of universality for its terminal amine group types (triethylenetetramine and diethylenetriamine).

[0074] 5. SCUG3 / NaCMC System: As shown in Figures 15 and 16, the SCUG3 / NaCMC system exhibits the best CO2 thickening performance. After CO2 introduction, its viscosity increases most significantly, and the difference between G' and G'' in the dynamic modulus test is the largest, indicating the formation of a gel with the highest strength and the most complete network structure. This is closely related to the highest functional group density of the SCUG3 molecule.

[0075] Conclusion: The above experimental results fully demonstrate that the dendritic macromolecules prepared in this invention (from the second generation onwards) exhibit excellent CO2-responsive thickening capabilities when combined with NaCMC. Their thickening efficiency is positively correlated with the generation number of the dendritic macromolecules, with the third generation (SCUG3) showing the best performance. This pattern provides a clear basis for precise molecular design tailored to the needs of different application scenarios.

[0076] Example 7 This example measures the carbon fixation properties of dendritic macromolecular composite gels of different generations prepared by the method described in this invention.

[0077] The CO2 absorption test procedure is as follows: The polymers obtained in Examples 1-5 were prepared into a 1wt% NaCMC / 0.2wt% SCUG aqueous solution, and 100 mL was placed in an absorption bottle. The absorption bottle was then placed in a 45ºC constant temperature pressure vessel, and the gas valve was adjusted to maintain a CO2 gas flow rate of 2 mL × min. −1The pressure is 10 MPa. A gas drying device and a micro gas flow meter are placed on the right side to periodically measure the gas flow rate at the outlet and record the changes in inlet and outlet gas flow rates over time. The absorption reaction ends when the inlet and outlet gas flow rates are equal and do not change within a certain time. The difference between the inlet and outlet flow rates within a certain time is the reaction rate between the absorbent and CO2 during that time. The absorption capacity can be calculated by the cumulative difference in flow rates between the inlet and outlet flow meters during the reaction time, as shown in Figure 17.

[0078] Results and Analysis: As shown in Figure 17, the CO2 absorption order under high temperature and high pressure (45℃, 10 MPa) conditions was: SCUG3 (21.53 mg / g) > SCUG2S (19.72 mg / g) > SCUG2D (18.57 mg / g) > SCUG2T (18.34 mg / g) >> SCUG1 (15.35 mg / g).

[0079] Example 8: This example measures the blocking performance of the SCUG2S dendritic macromolecules prepared by the method described in this invention. A glass microsphere chip is used as a porous media model to simulate and evaluate the blocking performance of the system of this invention. First, the chip is connected to a pressure sensor, and the test solution is injected to achieve pore saturation. Under the same chip and injection conditions (0.1 ml / min), water and SCUG2S composite systems are used as test solutions, respectively, and the pressure changes during CO2 displacement are compared and analyzed.

[0080] As shown in Figure 19, when water is used as the saturated solution, the inlet pressure first rises briefly and then falls during the introduction of CO2, and then remains at a low level, which is only the resistance generated by the flow of conventional fluid. No significant pressure increase was observed afterward, indicating that CO2 forms a dominant channel in it, and the water system cannot form an effective blockage in the porous medium.

[0081] In contrast, when the SCUG2S compound system was used as a saturated solution, although the inlet pressure rapidly increased after CO2 was introduced and then decreased as a dominant channel formed during subsequent injection, the pressure slowly increased again with the continuous injection of CO2. This phenomenon indicates that the SCUG2S system forms a blocking structure in the porous medium under the action of CO2, significantly increasing the fluid flow resistance and thus effectively inhibiting further CO2 crossflow. Calculations based on the pressure change results showed that the blocking rate of the SCUG2S compound system in the simulated porous medium was 84.8%, significantly higher than that of the water system, demonstrating excellent blocking performance. The above results indicate that the CO2-responsive compound system described in this invention can achieve in-situ blocking in porous media, thereby effectively inhibiting further CO2 crossflow and exhibiting good blocking performance.

Claims

1. A dendritic macromolecular composition for preventing gas migration and underground carbon sequestration, characterized in that, Its components and their mass content are as follows: 0.06%~0.4% dendritic macromolecules; 0.8%~1.6% sodium carboxymethyl cellulose; and the balance being water; the sum of the weight percentages of each component is 100%; the dendritic macromolecules are dendritic polyamine compounds constructed generation by generation through iterative Michael addition reactions between ester compounds and amine compounds, and aminolysis reactions, with the generation number being at least the second generation; the ester compound is methyl acrylate; the amine compound is at least one of tri(2-aminoethyl)amine, diethyltriamine, and triethyltetraamine.

2. The composition according to claim 1, characterized in that, The dendritic macromolecules were prepared by the following methods: (1) Synthesis of the semi-generation product: The previous generation amino-terminated dendritic macromolecules were dissolved in methanol, and methyl acrylate was added dropwise under nitrogen protection at 0-5℃. The molar ratio of methyl acrylate to dendritic macromolecules was 1:(25-40). The reaction was carried out at 0-5℃ for 0.5-1.5h, and then the temperature was raised to room temperature and the reaction was continued for 55-65h. After the reaction was completed, the solvent and excess monomer were removed by rotary evaporation under reduced pressure to obtain the semi-generation product; (2) Synthesis of the full-generation product: The semi-generation product was dissolved in methanol, and amine compounds were added dropwise under nitrogen protection at 0-5℃. The molar ratio of amine compounds to semi-generation product was 1:(40-60). The reaction was carried out at 0-5℃ for 0.5-1.5h. The reaction was then brought to room temperature and continued for approximately 6-8 days. Subsequently, the solvent was removed under reduced pressure, and excess amine compounds were removed by azeotropic distillation with a toluene:methanol volume ratio of 90:

10. The product was washed with anhydrous diethyl ether and vacuum dried to obtain a second-generation amino-terminated dendritic macromolecule. The amine compounds were selected from one of tris(2-aminoethyl)amine, diethyltriamine, and triethyltetraamine. The product was further iterated based on the second generation and capped with tris(2-aminoethyl)amine to obtain a third-generation product.

3. The composition according to claim 1, characterized in that, The mass ratio of sodium carboxymethyl cellulose (NaCMC) to dendritic macromolecules is 1:(0.002~0.003).

4. A method for preparing the composition according to any one of claims 1 to 3, comprising the following steps: (1) Dissolve sodium carboxymethyl cellulose in water to form an aqueous phase; (2) Inject dendritic macromolecules into the aqueous phase at a mass ratio of sodium carboxymethyl cellulose to dendritic macromolecules of 1:(0.002~0.003), stir at room temperature for 20~30 minutes to obtain a mixture.

5. The method according to claim 6, characterized in that, Step (1) The aqueous phase may also contain inorganic salts, wherein the inorganic salts are at least one of sodium chloride, sodium carbonate, sodium bicarbonate and magnesium chloride.

6. A dendritic macromolecular hydrogel, characterized in that, It is obtained by passing CO2 into a mixed solution of the dendritic macromolecular composition of claim 1.

7. The application of the dendritic macromolecular composition of claim 1 in preventing gas channeling and plugging leaks during CO2 oil displacement processes.

8. The use of the dendritic macromolecular composition of claim 1 in carbon capture and storage.

9. A dendritic macromolecule, characterized in that, The product was prepared by the following methods: (1) Synthesis of the semi-substituted product: The previous generation amino-terminated dendritic macromolecule was dissolved in methanol, and methyl acrylate was added dropwise under nitrogen protection at 0-5℃. The molar ratio of methyl acrylate to dendritic macromolecule was 1:(25-40). The reaction was carried out at 0-5℃ for 0.5-1.5 h, and then the temperature was raised to room temperature and the reaction was continued for 55-65 h. After the reaction was completed, the solvent and excess monomer were removed by rotary evaporation under reduced pressure to obtain the semi-substituted product; (2) Synthesis of the fully substituted product: The semi-substituted product was dissolved in methanol, and an amine compound was added dropwise under nitrogen protection at 0-5℃. The molar ratio of the amine compound to the semi-substituted product was 1:(40-60). The reaction was carried out at 0-5℃ for 0.5-1.5 h. The reaction was then brought to room temperature and continued for approximately 6-8 days. Subsequently, the solvent was removed under reduced pressure, and excess amine compounds were removed by azeotropic distillation with a toluene:methanol volume ratio of 90:

10. The product was washed with anhydrous diethyl ether and vacuum dried to obtain a second-generation amino-terminated dendritic macromolecule. The amine compounds were selected from one of tris(2-aminoethyl)amine, diethyltriamine, and triethyltetraamine. The product was further iterated based on the second generation and capped with tris(2-aminoethyl)amine to obtain a third-generation product.

10. The combined application of the dendritic macromolecules of claim 9 and sodium carboxymethyl cellulose in preventing gas channeling and underground carbon sequestration.

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