A core-shell based solvent-free nanofluid, its preparation and application in capturing greenhouse gas

Abstract

This invention discloses a core-shell based solvent-free nanofluid, its preparation, and its application in capturing greenhouse gases. The nanofluid is formed by dispersing inorganic nanoparticles in a co-flowing phase of a bifunctional coupling agent and a polymer. The inorganic nanoparticles are core-shell SiO2@LDH composite particles, consisting of LDH nanosheets loaded on the surface of SiO2 nanoparticles. The LDH is a layered double hydroxide. One end of the bifunctional coupling agent is hydrolyzed to form silanol groups, which undergo a condensation reaction with the hydroxyl groups on the surface of the LDH nanosheets to form stable chemical bonds. The other end of the coupling agent has an epoxy group that undergoes a ring-opening reaction with the amino groups in the polymer, achieving covalent grafting. This invention solves the problems of poor stability, easy aggregation, and unclear functional regulation and CO2 capture mechanisms in existing technologies. The resulting nanofluid exhibits high dispersion stability and excellent flowability, achieving the goal of efficient CO2 capture.

Description

Technical Field

[0001] This invention relates to a nanofluid for capturing greenhouse gases, specifically to a core-shell based SiO2@LDH solvent-free nanofluid, its preparation, and its application in capturing greenhouse gases. Background Technology

[0002] Solvent-free nanofluids are a new class of intelligent organic-inorganic hybrid materials. Their structure is designed with a functional inorganic nanomaterial as the core and an organic oligomer molecule as the shell, achieving strong interactions at the core-shell interface through covalent or ionic bonds. This unique molecular brush configuration not only retains the functional properties conferred by the inorganic core—such as high specific surface area, tunable pore structure, and abundant active sites—but also endows the material with macroscopic fluidity similar to liquids, thus achieving synergistic optimization of solid-liquid properties at the nanoscale. Compared with traditional nanoparticle / solvent suspension systems, solvent-free nanofluids exhibit performance advantages. These materials are stable liquids at room temperature, completely eliminating volume loss, environmental pollution, and long-term stability risks caused by solvent evaporation. The steric hindrance effect of their core-shell structure effectively inhibits the aggregation and sedimentation of nanoparticles, ensuring long-term dispersion stability. Furthermore, by controlling the molecular weight, chain segment density, and functional group types of the organic shell, precise control over rheological behavior and stimulus-response characteristics can be achieved. Solvent-free nanofluids have become key materials for overcoming the mass transfer barrier at traditional solid-liquid interfaces in fields such as gas separation, heterogeneous catalysis, and energy storage and conversion.

[0003] Efficient CO2 capture is a key technology for addressing global warming and promoting the achievement of "dual carbon" goals. Current CO2 capture materials have significant limitations: solid adsorbents, with their large specific surface area and tunable pore size, capture and immobilize pollutants, offering advantages such as high selectivity and ease of recovery, but suffer from slow mass transfer rates; liquid adsorbents can rapidly contact, react with, or dissolve pollutants over a large area, achieving high mass transfer efficiency, but are prone to causing secondary pollution and require stringent operational safety measures. To integrate the advantages of both, researchers have prepared nanofluids by uniformly dispersing nanoscale solid particles in a base liquid. This approach balances the functional properties of nanoparticles with the high efficiency of flow and mass transfer of the system; however, the tendency of nanoparticles to aggregate and settle severely restricts their long-term stable application.

[0004] Existing document 1 (Chinese invention patent application with publication number CN114196188A) discloses an MXene-based solvent-free nanofluid and its preparation method. This method modifies the surface of MXene (a two-dimensional transition metal carbon / nitride) nanosheets through surface functionalization and uses them as nanofillers to improve the flame retardant, mechanical, and barrier properties of polymers. This demonstrates the application potential of solvent-free nanofluids in composite material reinforcement. However, it should be noted that MXene itself, as a two-dimensional sheet material, still faces challenges in application: firstly, its chemical stability is relatively poor, especially in water-oxygen environments where it is easily oxidized; secondly, the strong van der Waals forces between the sheets easily lead to their recombination and aggregation, making it quite challenging to achieve long-term, uniform, and stable monolayer or oligolayer dispersion in a solvent-free organic phase. Summary of the Invention

[0005] The purpose of this invention is to provide a core-shell based SiO2@LDH solvent-free nanofluid, its preparation, and its application in capturing greenhouse gases. This invention solves the problems of poor stability, easy aggregation, and unclear functional regulation and CO2 capture mechanism in existing technologies. The prepared nanofluid has high dispersion stability and excellent flowability, achieving the goal of efficient CO2 capture. It also has the advantages of being environmentally friendly and highly scalable, providing an efficient and sustainable new material system for carbon capture technology, with significant application prospects and industrialization value.

[0006] To achieve the above objectives, the present invention provides a core-shell based solvent-free nanofluid, which is formed by dispersing inorganic nanoparticles in a co-flow phase of a bifunctional coupling agent and a polymer; wherein the inorganic nanoparticles have a core-shell structure and are selected from SiO2@LDH composite particles; the core of the SiO2@LDH composite particles is SiO2 and the shell is LDH nanosheets, which are composed of LDH nanosheets loaded on the surface of SiO2 nanoparticles; the LDH nanosheets are layered double hydroxides; one end of the bifunctional coupling agent is hydrolyzed to form silanol groups, which undergo a condensation reaction with the hydroxyl groups on the surface of the LDH nanosheets to form stable chemical bonds; the other end of the coupling agent has an epoxy group that undergoes a ring-opening reaction with the amino groups in the polymer to achieve covalent grafting.

[0007] Preferably, the bifunctional coupling agent is a silane coupling agent; the polymer is a polyetheramine; the layered double hydroxide is a hydrotalcite compound or anionic clay; and the molar ratio of the inorganic nanoparticles, the bifunctional coupling agent, and the polymer is 1:1:1.

[0008] Preferably, the polyetheramine is a polyether organic oligomer with a number average molecular weight of 1800-2200; More preferably, the bifunctional coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560); the polyetheramine is a polyetheramine with a molecular weight of 2070 (M2070).

[0009] Preferably, the SiO2 nanoparticles in the SiO2@LDH composite particles have a particle size of 100 nm to 200 nm.

[0010] This invention provides a method for preparing core-shell based solvent-free nanofluids. The method comprises: adding a bifunctional coupling agent and a polymer to an organic solvent and stirring at 40 °C to 60 °C to obtain a mixed solution; ultrasonically dispersing inorganic nanoparticles into the mixed solution, adding deionized water, and stirring overnight; dialyzing in deionized water and drying at 50 °C to obtain the core-shell based solvent-free nanofluid; the SiO2@LDH composite particles are obtained by adding LDH-NS to an alcohol solution containing SiO2 nanoparticles, stirring at room temperature, centrifuging at 8000 r / min, washing with anhydrous ethanol, and drying at 60 °C.

[0011] Preferably, the LDH-NS is prepared by the following method: Add NH3·H2O solution to a solution containing Mg(NO3)2·6H2O and Al(NO3)3·9H2O, stir at 70 °C~90 °C, centrifuge, wash until neutral, disperse in deionized water, and sonicate to remove impurities.

[0012] Preferably, the molar ratio of Mg(NO3)2·6H2O to Al(NO3)3·9H2O in the solution containing Mg(NO3)2·6H2O and Al(NO3)3·9H2O is (1~3):1; the molar ratio of total metal ions in the solution containing Mg(NO3)2·6H2O and Al(NO3)3·9H2O to N in the NH3·H2O solution is 1:(8~15).

[0013] Preferably, the organic solvent is methanol or ethanol; the dialysis is performed using a 5000 molecular weight cutoff dialysis bag.

[0014] Preferably, the ratio of the inorganic nanoparticles to the mixed solution is (0.5~2) g : (15~25) mL.

[0015] This invention provides an application of the core-shell based solvent-free nanofluid as described above in the capture of greenhouse gases.

[0016] This invention discloses a core-shell based solvent-free nanofluid, its preparation, and its application in greenhouse gas capture. It overcomes the problems of poor stability, easy aggregation, and unclear functional regulation and CO2 capture mechanisms in existing technologies, and has the following advantages: This invention utilizes a "core-shell SiO2@LDH construction-silane coupling agent mediated connection" strategy. It leverages the abundant hydroxyl groups on the surface of SiO2@LDH to form covalent bonds with the silanol groups after KH560 hydrolysis, while the epoxy groups of KH560 and the amino groups of M2070 form stable chemical bonds to construct SiO2@LDH-based solvent-free nanofluids. This effectively inhibits the aggregation and sedimentation of nanoparticles, and the fluidity does not decrease after 100 days of standing.

[0017] The nanofluid SiO2@LDH-M2070 of this invention has good room temperature fluidity and can be transported in pipelines and applied in industrial applications without the addition of solvents, avoiding environmental pollution, equipment corrosion and performance degradation caused by solvent evaporation; the nanofluid is non-volatile and non-toxic, meeting the requirements of green environmental protection.

[0018] In this invention, the SiO2 in the nanofluid SiO2@LDH-M2070 provides a permanent framework for the system, and the LDH-NS loading further enriches the pore structure and adsorption sites. Simultaneously, the interlayer anions of LDH, surface hydroxyl groups, and ether bonds of M2070 form a synergistic adsorption effect, significantly enhancing the SiO2 adsorption capacity. Compared with KH560-M2070, the CO2 capture capacity of the nanofluid SiO2@LDH-M2070 of this invention is increased by 200%~300%, reaching a capture capacity of 1.39 mmol / g under 1.0 MPa conditions. Attached Figure Description

[0019] Figure 1 The figure shows the stability test results of the nanofluid SiO2@LDH-M2070 prepared in Example 1 of this invention.

[0020] Figure 2 The figure shows the flowability test results of the nanofluid SiO2@LDH-M2070 prepared in Example 1 of this invention.

[0021] Figure 3 This is a morphology diagram of the original SiO2 used in this invention.

[0022] Figure 4 This is a morphology diagram of the core-shell SiO2@LDH composite particles prepared in Comparative Example 1 of this invention.

[0023] Figure 5 The figure shows the CO2 capture performance test results of the nanofluid SiO2@LDH-M2070 prepared in Example 1 of this invention. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1 A method for preparing core-shell based solvent-free nanofluid SiO2@LDH-M2070, the method comprising: Preparation of LDH-NS: Weigh 0.02 mol Mg(NO3)2·6H2O and 0.01 mol Al(NO3)3·9H2O, dissolve them in 100 mL of deionized water, and stir until completely dissolved; add 80 mL of 7 wt.% NH3·H2O solution, stir at 80 °C for 10 min, centrifuge to obtain LDH precursor, wash with deionized water until neutral, disperse in deionized water, and sonicate for 30 min to obtain Mg-Al type LDH-NS dispersion (1 mg / mL).

[0026] Preparation of core-shell SiO2@LDH composite particles: 0.1 g of SiO2 nanoparticles with a particle size of 100 nm to 200 nm were dispersed in 10 mL of anhydrous ethanol and ultrasonically dispersed for 15 min; the above Mg-Al type LDH-NS dispersion (the mass of LDH-NS in the added Mg-Al type LDH-NS dispersion was 0.02 g) was added, and the mixture was stirred at room temperature for 6 h; after the reaction was completed, the mixture was centrifuged at 8000 r / min for 10 min, washed 3 times with anhydrous ethanol, and dried at 60℃ for 8 h to obtain core-shell SiO2@LDH composite particles.

[0027] Preparation of core-shell solvent-free nanofluid SiO2@LDH-M2070: 1 mmol of silane coupling agent KH560 and 1 mmol of polyetheramine M2070 were added to 20 mL of methanol and stirred at 323 K for 8 h to obtain an organic oligomer (denoted as KH560-M2070). SiO2@LDH (1 g) was ultrasonically dispersed in the KH560-M2070 solution, and 1 mL–2 mL of deionized water was added. The mixture was stirred overnight at 35°C. The resulting product was dialyzed in 2 L–4 L of deionized water for 3–6 days (using a 5000 molecular weight cutoff dialysis bag). The dialyzed liquid was dried at 70 °C for 48 h to obtain the core-shell solvent-free nanofluid, denoted as SiO2@LDH-M2070.

[0028] Comparative Example 1 The preparation method of SiO2@LDH composite particles is basically the same as that in Example 1, except that: Preparation of core-shell SiO2@LDH composite particles.

[0029] Comparative Example 2 A method for preparing SiO2-M2070 nanofluid, the method comprising: 1 mmol of silane coupling agent KH560 and 1 mmol of polyetheramine M2070 were added to 20 mL of methanol and stirred at 323 K for 8 h to obtain an organic oligomer (denoted as KH560-M2070). SiO2 (1 g) was ultrasonically dispersed in the KH560-M2070 solution, and 1 mL–2 mL of deionized water was added to the mixture. The mixture was stirred overnight at 35°C. The resulting product was then dialyzed in 2–4 L of deionized water for 3–6 days (using a 5000 molecular weight cutoff dialysis bag). The dialyzed liquid was dried at 70°C for 48 h to obtain a SiO2-based solvent-free nanofluid, denoted as SiO2-M2070 nanofluid.

[0030] Comparative Example 3 A method for preparing oligomer KH560-M2070, the method comprising: 1 mmol of silane coupling agent KH560 and 1 mmol of polyetheramine M2070 were added to 20 mL of methanol and stirred at 323 K for 8 h to obtain an organic oligomer (denoted as KH560-M2070). The resulting product was then dialyzed in 2 L–4 L of deionized water for 3–6 days (using a 5000 molecular weight cutoff dialysis bag). The dialyzed liquid was dried at 70 °C for 48 h to obtain the KH560-M2070 fluid.

[0031] Experiment 1: Performance Testing of SiO2@LDH-M2070 The dispersion stability and flowability of the core-shell based solvent-free nanofluid SiO2@LDH-M2070 prepared in Example 1 and the core-shell SiO2@LDH composite particles prepared in Comparative Example 1 were tested. The dispersion stability test involved dispersing the core-shell based solvent-free nanofluid SiO2@LDH-M2070 prepared in Example 1 and the SiO2@LDH composite particles prepared in Comparative Example 1 in different solvents (from left to right: water, ethanol, methanol, DMF, and acetone) and observing the precipitation at room temperature. The flowability test involved placing the core-shell based solvent-free nanofluid SiO2@LDH-M2070 prepared in Example 1 at room temperature for 100 days and observing its flowability.

[0032] like Figure 1As shown in the figure, the stability test results of the nanofluid SiO2@LDH-M2070 prepared in Example 1 of this invention are as follows: A shows the results of the SiO2@LDH composite particles prepared in Comparative Example 1 dispersed in different solvents (from left to right: water, ethanol, methanol, DMF, and acetone); B shows the results of the SiO2@LDH-M2070 prepared in Example 1 dispersed in different solvents (from left to right: water, ethanol, methanol, DMF, and acetone). Figure 1 It can be seen that the SiO2@LDH composite particles prepared in Comparative Example 1 showed obvious precipitation after being dispersed in different solvents for 24 hours and 48 hours; while the SiO2@LDH-M2070 nanofluid prepared in Example 1 did not show obvious precipitation after being dispersed in different solvents for 24 hours and 48 hours.

[0033] like Figure 2 The figure shown is a flowability test result of the nanofluid SiO2@LDH-M2070 prepared in Example 1 of this invention. Figure 2 It can be seen that SiO2@LDH-M2070 still maintains excellent fluidity after being placed at room temperature for 100 days, without precipitation or aggregation.

[0034] Experiment 2: Morphology testing of SiO2 and SiO2@LDH like Figure 3 The image shows the morphology of the original SiO2 used in this invention.

[0035] like Figure 4 The image shows the morphology of the core-shell SiO2@LDH composite particles prepared in Comparative Example 1 of this invention.

[0036] Depend on Figures 3-4 It can be seen that the morphology of the original SiO2 is as follows: Figure 3 As shown, the particles are smooth spherical. The core-shell SiO2@LDH composite particles prepared in Comparative Example 1 have a core-shell structure, specifically, smooth SiO2 spherical particles inside are wrapped with LDH nanosheets. This structure provides more grafting sites for M2070 in the SiO2@LDH-M2070 prepared in Example 1, which helps to achieve stable dispersion of SiO2@LDH-M2070 and improve CO2 capture performance.

[0037] Experiment Example 3: Application of Nanofluids to Capture CO2 The products obtained in Examples 1-2 and Comparative Example 2 were used to capture CO2. Specifically, the CO2 capture capacity of the nanofluid SiO2@LDH-M2070 prepared in Example 1, the SiO2-M2070 nanofluid in Comparative Example 2, and the organic oligomer KH560-M20270 in Comparative Example 3 were tested at 25 °C and 1 MPa. The CO2 adsorption performance was evaluated using a BSD-PH2 fully automated high-pressure gas adsorption instrument manufactured by Best Instruments Technology (Beijing) Co., Ltd. The precisely weighed sample was placed into a dedicated sample tube, ensuring the tube was sealed tightly. High-purity CO2 gas was then introduced into the sample tube. After the system pressure stabilized to the preset target value, the sample tube was sealed, allowing the sample to begin the static adsorption process under isothermal conditions. The instrument monitored and recorded the pressure decay changes in the sample tube caused by CO2 adsorption in real time using a high-precision pressure sensor, and finally calculated and output the CO2 adsorption capacity per unit mass of sample.

[0038] like Figure 5 The figure shows the CO2 capture performance test results of the nanofluid SiO2@LDH-M2070 prepared in Example 1 of this invention. KH560-M2070 was prepared in Comparative Example 3; SiO2-M2070 was prepared in Comparative Example 2; and SiO2@LDH-M2070 is the product prepared in Example 1. Figure 3 It is known that the CO2 capture capacity of the nanofluid SiO2@LDH-M2070 prepared in Example 1 is 1.39 mmol / g. KH560, the key bridging component of the nanofluid SiO2@LDH-M2070 in Example 1, is hydrolyzed to form silanol groups at one end, which then undergo a condensation reaction with the hydroxyl groups on the surface of the LDH nanosheets, forming a strong chemical bond. The epoxy groups at the other end undergo a ring-opening reaction with the amino groups in M2070, achieving covalent grafting. In contrast, the CO2 capture capacity of the organic oligomer KH560-M2070 in Comparative Example 3 is 0.55 mmol / g; and the CO2 capture capacity of SiO2-M2070 in Comparative Example 2 is 0.97 mmol / g. Therefore, this invention successfully constructs the SiO2@LDH-M2070 nanofluid through the synergistic reaction at both ends of KH560. This system exhibits stable liquid properties and non-volatile characteristics at room temperature, making it suitable for efficient CO2 capture.

[0039] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A core-shell based solvent-free nanofluid, characterized in that, The nanofluid comprises: inorganic nanoparticles dispersed in a co-flow phase of a bifunctional coupling agent and a polymer; Among them, the inorganic nanoparticles are core-shell SiO2@LDH composite particles, with SiO2 as the core and LDH nanosheets as the shell, which are composed of LDH nanosheets loaded on the surface of SiO2 nanoparticles. The LDH nanosheets are layered double hydroxides; One end of the bifunctional coupling agent is hydrolyzed to form a silanol group, which undergoes a condensation reaction with the hydroxyl groups on the surface of the LDH nanosheets to form a stable chemical bond; the other end of the epoxy group undergoes a ring-opening reaction with the amino group in the polymer to achieve covalent grafting.

2. The core-shell based solvent-free nanofluid according to claim 1, characterized in that, The bifunctional coupling agent is a silane coupling agent; the polymer is a polyetheramine; the layered double hydroxide is a hydrotalcite compound or anionic clay; the molar ratio of the inorganic nanoparticles, the bifunctional coupling agent, and the polymer is 1:1:

1.

3. The core-shell based solvent-free nanofluid according to claim 2, characterized in that, The polyetheramine is a polyether organic oligomer with a molecular weight of 2070.

4. The core-shell based solvent-free nanofluid according to claim 2, characterized in that, The SiO2 nanoparticles in the SiO2@LDH composite particles have a particle size of 100 nm to 200 nm.

5. A method for preparing core-shell based solvent-free nanofluids, characterized in that, The method includes: The bifunctional coupling agent and polymer were added to an organic solvent and stirred at 40 °C to 60 °C to obtain a mixed solution; inorganic nanoparticles were ultrasonically dispersed into the mixed solution, deionized water was added, and the mixture was stirred overnight; the mixture was dialyzed in deionized water and dried at 50 °C to obtain the core-shell based solvent-free nanofluid. The inorganic nanoparticles were obtained by adding LDH-NS to an ethanol solution containing inorganic oxide nanoparticles, stirring the reaction at room temperature, centrifuging at 8000 r / min, washing with anhydrous ethanol, and drying at 60 °C.

6. The preparation method according to claim 5, characterized in that, The LDH-NS is prepared by the following method: Add NH3·H2O solution to a solution containing Mg(NO3)2·6H2O and Al(NO3)3·9H2O, stir at 70 °C~90 °C, centrifuge, wash until neutral, disperse in deionized water, and sonicate to remove impurities.

7. The preparation method according to claim 5, characterized in that, The molar ratio of Mg(NO3)2·6H2O to Al(NO3)3·9H2O in the solution containing Mg(NO3)2·6H2O and Al(NO3)3·9H2O is (1~3):1; the molar ratio of total metal ions in the solution containing Mg(NO3)2·6H2O and Al(NO3)3·9H2O to N in the NH3·H2O solution is 1:(8~15).

8. The preparation method according to claim 5, characterized in that, The organic solvent is methanol or ethanol; the dialysis is performed using a 5000 molecular weight cutoff dialysis bag.

9. The preparation method according to claim 5, characterized in that, The ratio of the inorganic nanoparticles to the mixed solution is (0.5~2) g : (15~25) mL.

10. The application of a core-shell based solvent-free nanofluid as described in any one of claims 1 to 4 in capturing greenhouse gases.

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