Heat-conducting and carbon-fixing dual-effect nano-emulsified composite fluid and preparation method thereof

Abstract

The application discloses a kind of heat-conducting-carbon sequestration double-effect nano-emulsified composite fluid and preparation method thereof, belong to geothermal energy development and carbon sequestration technical field.Aiming at the problems of poor heat conduction of existing heat-conducting fluid, low CO2 sequestration efficiency and easy to weaken the structure of filling body, the application is compounded by deionized water, methanol, choline chloride, ethylene glycol, polydimethylsiloxane, graphene oxide and nanometer silicon dioxide according to weight parts, and CO2 is loaded after step-by-step dispersion, gradient shear emulsification and vacuum degassing.Choline chloride and ethylene glycol form a eutectic solvent in advance, combined with pulse ultrasonic temperature control process, to ensure uniform dispersion of nanoparticles.The composite emulsion droplet size is 50-300nm, the thermal conductivity coefficient is 0.4-0.85W / (m·K), and the CO2 fixation rate is 1.1-2.9mol / L.In the cycle, it not only can efficiently take heat, but also can promote CO2 and filling body to occur carbonation reaction to realize in-situ reinforcement, perfectly solve the contradiction between "heat extraction" and "strength preservation", realize the synergistic effect of geothermal exploitation and carbon sequestration.

Description

Technical Field

[0001] This invention relates to the field of geothermal energy development and carbon sequestration technology, and in particular to a thermally conductive and carbon-fixing dual-effect nanoemulsion composite liquid and its preparation method. Background Technology

[0002] Driven by the "dual carbon" goals, geothermal energy, as a clean and renewable local energy source, is an important development direction for my country's energy structure transformation and carbon reduction. my country's coal mining areas are rich in medium- and low-temperature geothermal resources. Promoting the technology of coal mine backfilling and geothermal co-extraction can control surface subsidence and ensure mine production safety through backfilling mining, while also leveraging the porous media of the backfill body to achieve geothermal energy extraction and CO2 geological sequestration. This technology combines multiple values ​​of engineering safety, resource development, and ecological protection, and is one of the core technological pathways for the green transformation of mining areas.

[0003] In geothermal co-extraction systems, the heat transfer fluid is the core carrier for heat transfer and carbon sequestration, and its performance directly determines the geothermal extraction efficiency, carbon sequestration effect, and long-term stability of the backfill. In existing engineering applications, heat transfer fluids are mainly divided into two categories: water-based and gas-based. Water-based fluids, represented by pure water, possess a certain thermal conductivity, but during long-term circulation, they react with the hydrated gel and active calcium and magnesium components within the backfill, accelerating the decomposition of hydration products, causing the backfill's strength to deteriorate or even its structure to collapse, seriously threatening the long-term stability of the goaf. Simultaneously, pure water has a limited CO2 dissolution capacity, failing to achieve the synergistic effect of efficient carbon sequestration and carbon fixation. Gas-based fluids, mainly composed of gases such as CO2 and nitrogen, can avoid hydration and deterioration of the backfill, but they have low thermal conductivity and weak heat exchange capacity. Furthermore, they are prone to gas channeling and fingering phenomena in porous media, resulting in extremely low sweep efficiency and heat collection efficiency, making it difficult to meet engineering requirements for CO2 utilization and sequestration.

[0004] To improve the performance of thermally conductive fluids, existing technologies attempt to add nanoparticles to aqueous solutions to increase thermal conductivity or use conventional emulsion systems to improve mass transfer. However, these approaches still have significant drawbacks: ordinary nanoparticles tend to agglomerate and settle in aqueous solutions, exhibiting poor long-term stability and limited improvement in thermal conductivity; conventional emulsion systems have large droplet sizes and insufficient interfacial stability, making it difficult to efficiently load and retain CO2 molecules, and also difficult to improve the sweep efficiency of porous media through microstructural control; more importantly, existing modified fluids cannot simultaneously achieve the multiple objectives of "high-efficiency thermal conductivity - high CO2 loading - reinforcement of filling structure," making them unsuitable for the complex operating conditions of coal mine backfilling and geothermal co-extraction.

[0005] In summary, existing heat-conducting fluids generally suffer from insufficient thermal conductivity, low sweep efficiency in porous media, poor CO2 utilization, and are prone to causing mechanical degradation of the filling material. There is an urgent need to develop a novel heat-conducting composite fluid that combines high thermal conductivity, high carbon sequestration capacity, and high sweep efficiency, while also being able to reinforce the filling material through carbonation reaction, in order to support the engineering application of the synergistic technology of filling-geothermal-carbon sequestration in mining areas. Summary of the Invention

[0006] The present invention aims to provide a thermally conductive and carbon-fixing dual-effect nanoemulsion composite liquid and its preparation method. This method involves adding graphene oxide and nano-silica to a conventional emulsion composite solution to prepare nanoscale emulsion droplets. This nanoemulsion composite liquid effectively improves thermal conductivity, enhances CO2 sequestration capacity, and solves the problem of low sweep efficiency of conventional thermally conductive fluids in porous media. During the absorption of heat energy in the porous media of the filling body, the CO2 molecules of the nanoemulsion composite liquid react with the active calcium and magnesium components and hydrated gel in the filling body to generate carbonic acid products, thereby effectively reinforcing the microstructure of the porous media and improving the overall mechanical properties of the filling body. Furthermore, during the recycling of the nanoemulsion composite liquid, continuous replenishment of CO2 can further improve the CO2 utilization efficiency and sequestration effect.

[0007] To achieve the above-mentioned objectives, the present invention employs the following technical solution: a thermally conductive and carbon-fixing dual-effect nanoemulsion composite liquid, comprising, by weight: 30-75 parts deionized water, 5-25 parts methanol, 2.5-10 parts choline chloride, 5-30 parts ethylene glycol, 5-20 parts polydimethylsiloxane, 0.01-5 parts graphene oxide, and 0.1-10 parts nano-silica;

[0008] The composite liquid is a CO2-loaded nanoemulsion system.

[0009] Furthermore, choline chloride and ethylene glycol are formulated into a eutectic solvent at a mass ratio of 1:(1.2~2.5) to serve as a component of the continuous phase of the composite liquid. Utilizing the excellent solubility and extremely low vapor pressure of the eutectic solvent, the drawbacks of traditional organic solvents such as volatility and instability are effectively overcome. Simultaneously, its rich hydrogen-bonded donor-acceptor properties significantly enhance the physical adsorption capacity of CO2 in the continuous phase, providing a chemical basis for subsequent efficient carbon fixation.

[0010] Furthermore, the nano-silica has a particle size of 10 nm to 500 nm and a specific surface area of ​​25 m² / g to 400 m² / g. By limiting the microscopic size and specific surface area range of the nano-silica, effective anchoring of the particles at the emulsion droplet interface is ensured. The abundant adsorption sites provided by the high specific surface area significantly increase the gas-liquid contact interface, thereby significantly improving the solubility and retention rate of CO2 molecules, while enhancing the suspension stability of the system.

[0011] Furthermore, the emulsion droplet size of the composite liquid is 50nm~300nm, with the contact angle of the nano-silica maintained at 60°~90°. Controlling the emulsion droplets at the nanoscale and strictly limiting the contact angle range of the nano-silica ensures that the droplet surface has a suitable hydrophilic-lipophilic balance. This prevents droplet aggregation and demulsification due to excessive affinity, and also utilizes the "Pickering" stabilizing effect of solid particles to form a stable Jamin effect in the pores of the filling medium, effectively improving the sweep efficiency and plugging ability of the fluid in the porous medium.

[0012] Furthermore, the composite liquid has a thermal conductivity of 0.4 W / m·K to 0.85 W / m·K and a CO2 fixation rate of 1.1 mol / L to 2.9 mol / L. These performance parameters quantify the excellent performance of the composite liquid under actual working conditions. The high thermal conductivity ensures efficient heat extraction during geothermal exploitation, while the extremely high CO2 fixation rate verifies the significant advantages of this system in carbon sequestration, achieving the dual functions of "heat extraction" and "carbon sequestration."

[0013] A method for preparing a thermally conductive and carbon-fixing dual-effect nanoemulsion composite liquid includes the following steps:

[0014] Step 1: Preparation of eutectic solvent stock solution: Mix choline chloride and ethylene glycol at a mass ratio of 1:(1.2~2.5), heat to 55~85℃, and stir at 300~750r / min for 1~2h until a transparent homogeneous liquid is formed, thus obtaining the eutectic solvent stock solution;

[0015] Step 2: Preparation of graphene oxide suspension: Mix graphene oxide and deionized water at a mass ratio of (0.01~5):10, stir at 200 r / min for 1~10 min, and then treat with ultrasonic dispersion to obtain graphene oxide suspension;

[0016] Step 3: Preparation of nano-silica suspension: Methanol and deionized water are mixed evenly at a mass ratio of (15~30):100 to obtain a first mixture. Nano-silica is mixed with the first mixture at a mass ratio of (0.1~3):10 and treated with the ultrasonic dispersion method described in Step 2 to obtain nano-silica suspension.

[0017] Step 4: Preparation of continuous phase solution: Mix methanol and deionized water at a mass ratio of (15~30):100, stir at 500 r / min for 5~15 min to obtain a second mixture, add the eutectic solvent stock solution from step 1 to the second mixture, the mass ratio of the eutectic solvent stock solution to the second mixture is (10~25):100, stir at 700 r / min for 10~25 min to obtain a continuous phase solution;

[0018] Step 5: Preparation of functionalized continuous phase solution: Add the graphene oxide suspension from step 2 to the continuous phase solution from step 4, stir at 800 r / min for 10-25 min, then add the nano silica suspension from step 3, stir at 1000 r / min for 20-40 min to obtain the functionalized continuous phase solution.

[0019] Step 6: Preparation of conventional emulsion solution: Heat polydimethylsiloxane to 30~45℃ and stir at 300r / min for 10min. Then, add it dropwise to the functionalized continuous phase solution of step 5 at a flow rate of 1~2mL / min using a dropper. Stir at 1500r / min for 20~40min during the dropwise addition to obtain a conventional emulsion solution.

[0020] Step 7: Preparation of nanoemulsion composite liquid: Transfer the conventional emulsion solution from step 6 to a homogenizer and homogenize it at a high speed of 7500~20000 r / min for 5~30 min. Then, treat it under vacuum conditions of -0.08MPa for 5~20 min to remove trapped air and obtain nanoemulsion composite liquid.

[0021] Step 8, CO2 loading: Transfer the nanoemulsion composite liquid from step 7 to a sealed reactor, and introduce CO2 gas into the reactor at a flow rate of 0.1~1.5L / min for 20~200min to obtain CO2 nanoemulsion composite liquid.

[0022] Furthermore, the ultrasonic dispersion method involves using an ultrasonic disperser with a 3s on / 3s off pulse mode, an ultrasonic frequency of 20kHz~60kHz, an ultrasonic power of 150W~500W, and a cumulative ultrasonic time of 30~60min. During the ultrasonic treatment, the water in the ultrasonic disperser is replaced every 2min~5min to control the water temperature in the ultrasonic disperser below 35℃. The use of an on / off pulse ultrasonic mode combined with strict temperature control measures effectively provides high-intensity shear force to exfoliate nanoparticle aggregates while avoiding damage to the graphene oxide sheet structure or failure of the nano-silica surface modification due to localized high temperatures caused by cavitation effects, thus ensuring the long-term dispersion stability of the nanofiller in the liquid phase.

[0023] Furthermore, the viscosity of the polydimethylsiloxane after heating to 30-45°C is 0.5-10 mPa·s. Preheating the polydimethylsiloxane to a specific temperature range to precisely control its low viscosity state facilitates the rapid spreading and oriented alignment of the surfactant on the droplet surface under high-speed shear, significantly reducing interfacial tension. This promotes the formation of a nanoemulsion with uniform particle size and strong stability, preventing flocculation or phase inversion during emulsification.

[0024] Furthermore, after vacuum treatment at -0.08 MPa, the volume of the resulting CO2 nanoemulsion composite liquid remained at 95%~99% of its volume before vacuum treatment. By limiting the volume retention rate after vacuum treatment, the compactness and strength of the emulsion film were cleverly verified, indicating that the composite liquid prepared by this process not only successfully removed the mixed air (preventing air bubbles from occupying CO2 adsorption sites), but also had a compact droplet structure without rupture or Austronesian ripening, ensuring the performance stability of the product during storage and transportation.

[0025] Further, in step 1, the mass ratio of choline chloride to ethylene glycol is 1:1.5, the heating temperature is 60℃, the stirring speed is 550 r / min, and the stirring time is 1.5 h; in step 7, the homogenization emulsification speed is 17500 r / min, the homogenization time is 20 min, and the vacuum treatment time is 10 min; in step 8, the CO2 gas flow rate is 1 L / min, and the gas flow time is 120 min. The composite liquid prepared using this set of optimized process parameters exhibits uniform emulsion droplet size distribution, excellent nanoparticle dispersibility, and can stably achieve high thermal conductivity and high CO2 fixation rate. The preparation process has good repeatability and is suitable for large-scale production applications.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) In the prior art, although water-based fluids have good thermal conductivity, they are prone to causing the decomposition of hydration products and weakening of strength in the filling material. However, this invention changes the traditional physical heat exchange mechanism by introducing the synergistic effect of choline chloride / ethylene glycol eutectic solvent and CO2. During the cyclic endothermic process of the composite liquid, CO2 molecules in the liquid phase react with the active calcium and magnesium components in the filling material to form dense calcium carbonate / magnesium carbonate precipitates. This process not only does not weaken the filling material like traditional water flow, but also plays a role in "in-situ reinforcement", significantly improving the density and compressive strength of the filling material, and perfectly solving the contradiction between "heat extraction" and "strength preservation" in geothermal extraction.

[0028] (2) Unlike simple doping of single nanoparticles, this invention utilizes the high thermal conductivity of graphene oxide and the interfacial modification properties of nano-silica to construct a three-dimensional thermally conductive network inside micron-sized emulsion droplets. The graphene oxide sheets act as a "thermal bridge" to significantly improve the thermal conductivity of the matrix, while the nano-silica acts as a "separator" to effectively prevent the stacking and aggregation of the graphene oxide sheets.

[0029] (3) The nanoemulsion composite liquid prepared by this invention has a unique microstructure: nano silica particles (contact angle 60°~90°) are adsorbed at the oil-water interface to form a dense solid particle film (Pickering stabilization mechanism), which effectively inhibits droplet aggregation; at the same time, the eutectic solvent is rich in hydrogen bond acceptors and has a strong affinity for CO2. This dual mechanism of "physical encapsulation + chemical adsorption" makes the CO2 fixation rate of the composite liquid reach an astonishing 1.78~2.10 mol / L (Examples 1-5), which is much higher than that of traditional water-based solutions and comparative examples, effectively preventing gas escape and truly realizing the synergistic effect of geothermal development and carbon sequestration.

[0030] (4) The present invention has made two key innovations in the preparation process: First, it adopts the pulsed ultrasonic mode of "on 3s / off 3s" and strictly controls the water temperature below 35℃ with high frequency water exchange. While ensuring the ultrasonic peeling strength, it avoids the graphene oxide sheets from being damaged by cavitation heat effect and retains its complete sp² hybrid structure. Second, it designs a gradient shearing process from low speed stirring (300 r / min) to high speed homogenization (17500 r / min) and combines it with vacuum degassing process (volume retention rate of 95%~99%) to ensure the uniform distribution of nanoparticles in micron-sized droplets and the long-term stability of the system. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Of course, the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] This invention provides a thermally conductive and carbon-fixing dual-effect nanoemulsion composite liquid, which, by weight, comprises: 30-75 parts deionized water, 5-25 parts methanol, 2.5-10 parts choline chloride, 5-30 parts ethylene glycol, 5-20 parts polydimethylsiloxane, 0.01-5 parts graphene oxide, and 0.1-10 parts nano-silica.

[0033] The nano-silica has a particle size of 10nm~500nm and a specific surface area of ​​25m² / g~400m² / g.

[0034] The emulsion droplet size of the composite liquid is 50nm~300nm, and the contact angle of the nano-silica is maintained at 60°~90°.

[0035] The composite liquid has a thermal conductivity of 0.4 W / m·K to 0.85 W / m·K and a CO2 fixation rate of 1.1 mol / L to 2.9 mol / L.

[0036] This invention also provides a method for preparing a thermally conductive and carbon-fixing dual-effect nanoemulsion composite liquid, comprising the following steps:

[0037] Step 1: Preparation of eutectic solvent stock solution: Mix choline chloride and ethylene glycol at a mass ratio of 1:(1.2~2.5), heat to 55~85℃, and stir at 300~750r / min for 1~2h until a transparent homogeneous liquid is formed, thus obtaining the eutectic solvent stock solution.

[0038] Step 2: Preparation of graphene oxide suspension: Mix graphene oxide and deionized water at a mass ratio of (0.01~5):10, stir at 200 r / min for 1~10 min, and then treat with ultrasonic dispersion to obtain graphene oxide suspension; The ultrasonic dispersion method is as follows: Use an ultrasonic disperser with a pulse mode of 3s on / 3s off, ultrasonic frequency of 20kHz~60kHz, ultrasonic power of 150W~500W, and cumulative ultrasonic time of 30~60 min; During the ultrasonic treatment, the water in the ultrasonic disperser is replaced every 2 min~5 min to control the water temperature in the ultrasonic disperser below 35 ℃.

[0039] Step 3: Preparation of nano-silica suspension: Methanol and deionized water are mixed evenly at a mass ratio of (15~30):100 to obtain a first mixture. Nano-silica is mixed with the first mixture at a mass ratio of (0.1~3):10 and treated with the ultrasonic dispersion method described in Step 2 to obtain nano-silica suspension.

[0040] Step 4: Preparation of continuous phase solution: Mix methanol and deionized water at a mass ratio of (15~30):100, stir at 500 r / min for 5~15 min to obtain a second mixture, add the eutectic solvent stock solution from step 1 to the second mixture, the mass ratio of the eutectic solvent stock solution to the second mixture is (10~25):100, stir at 700 r / min for 10~25 min to obtain a continuous phase solution;

[0041] Step 5: Preparation of functionalized continuous phase solution: Add the graphene oxide suspension from step 2 to the continuous phase solution from step 4, stir at 800 r / min for 10-25 min, then add the nano silica suspension from step 3, stir at 1000 r / min for 20-40 min to obtain the functionalized continuous phase solution.

[0042] Step 6: Preparation of conventional emulsion solution: Heat polydimethylsiloxane to 30~45℃ and stir at 300r / min for 10min. Then, add it dropwise to the functionalized continuous phase solution of step 5 at a flow rate of 1~2mL / min using a dropper. During the dropwise addition, stir at 1500r / min for 20~40min to obtain a conventional emulsion solution. The viscosity of the polydimethylsiloxane after heating to 30~45℃ is 0.5~10mPa·s.

[0043] Step 7: Preparation of nanoemulsion composite liquid: Transfer the conventional emulsion solution from Step 6 to a homogenizer and homogenize it at a high speed of 7500~20000 r / min for 5~30 min. Then, treat it under vacuum conditions of -0.08MPa for 5~20 min to remove trapped air and obtain nanoemulsion composite liquid. The volume of the nanoemulsion composite liquid is maintained at 95%~99% of the volume before vacuum treatment.

[0044] Step 8, CO2 loading: Transfer the nanoemulsion composite liquid from step 7 to a sealed reactor, and introduce CO2 gas into the reactor at a flow rate of 0.1~1.5L / min for 20~200min to obtain CO2 nanoemulsion composite liquid.

[0045] To further understand the preparation method of the thermally conductive-carbon-solidifying dual-effect nanoemulsion composite liquid provided by the present invention, the following detailed description is provided in conjunction with the embodiments.

[0046] Example 1

[0047] Step 1: Transfer choline chloride and ethylene glycol to a glass reactor with a mass ratio of choline chloride to ethylene glycol of 1:1.5. Heat to 60°C and stir at 550 r / min for 1.5 h until a transparent and homogeneous liquid is formed, thus obtaining a eutectic solvent stock solution.

[0048] Step 2: Mix graphene oxide and deionized water at a mass ratio of 0.1:10, and stir the mixture at 200 r / min for 1–10 min. Use an ultrasonic disperser with a pulse mode of 3 s on / 3 s off to ultrasonically treat the resulting mixture for a cumulative ultrasonic time of 40 min. During this process, the water in the ultrasonic disperser is replaced every 5 min to control the water temperature below 35 ℃, ensuring sufficient dispersion of graphene oxide and avoiding the influence of excessively high temperatures on the properties of graphene oxide. The ultrasonically treated mixture yields a graphene oxide suspension.

[0049] Step 3: Add methanol to deionized water at a mass ratio of 25:100 and mix thoroughly to obtain a first mixture. Add nano-silica to the first mixture at a mass ratio of 0.1:10 and then treat it using the ultrasonic dispersion method described in Step 2 to obtain a nano-silica suspension.

[0050] Step 4: Add methanol to deionized water at a mass ratio of 25:100. Mix and stir at 500 r / min for 10 min until homogeneous to obtain a second mixture. Add the eutectic solvent stock solution from step S1 to the second mixture at a mass ratio of 15:100. Mix and stir at 700 r / min for 20 min to obtain a continuous phase solution.

[0051] Step 5: Add the graphene oxide suspension from Step 2 to the continuous phase solution from Step 4, mix and stir at 800 r / min for 15 min, and after stirring evenly, add the nano silica suspension from Step 3, mix and stir at 1000 r / min for 30 min to obtain the functionalized continuous phase solution.

[0052] Step 6: Heat polydimethylsiloxane to 40°C and stir at 300 r / min for 10 min. After stirring evenly, use a dropper to add polydimethylsiloxane to the functionalized continuous phase solution in step 5 at a rate of 1 mL / min, while stirring at 1500 r / min for 30 min to obtain a conventional emulsion solution.

[0053] Step 7: Transfer the conventional emulsion solution from Step 6 to a homogenizer and homogenize it at 17500 r / min for 20 min. Then, treat it under vacuum at -0.08 MPa for 10 min to remove trapped air and obtain the nano-emulsion composite solution.

[0054] Step 8: Transfer the nanoemulsion composite liquid to a sealed reactor, and then inject CO2 gas into the reactor at a flow rate of 1L / min for 120min to obtain CO2 nanoemulsion composite liquid.

[0055] Step 9: Analyze the thermal conductivity and CO2 fixation rate of the CO2 nanoemulsion composite liquid obtained in Step 8.

[0056] Example 2

[0057] Step 1: Transfer choline chloride and ethylene glycol to a glass reactor with a mass ratio of choline chloride to ethylene glycol of 1:1.5. Heat to 60°C and stir at 550 r / min for 1.5 h until a transparent and homogeneous liquid is formed, thus obtaining a eutectic solvent stock solution.

[0058] Step 2: Mix graphene oxide and deionized water at a mass ratio of 0.25:10, and stir the mixture at 200 r / min for 1–10 min. Use an ultrasonic disperser with a pulse mode of 3 s on / 3 s off to ultrasonically treat the resulting mixture for a cumulative ultrasonic time of 40 min. During this process, the water in the ultrasonic disperser is replaced every 5 min to control the water temperature below 35 ℃, ensuring sufficient dispersion of graphene oxide and avoiding the influence of excessively high temperatures on the properties of graphene oxide. The ultrasonically treated mixture yields a graphene oxide suspension.

[0059] Step 3: Add methanol to deionized water at a mass ratio of 25:100 and mix thoroughly to obtain a first mixture; add nano-silica to the first mixture at a mass ratio of 0.1:10, and then treat with the ultrasonic dispersion method described in Step 2 to obtain a nano-silica suspension.

[0060] Step 4: Add methanol to deionized water at a mass ratio of 25:100. Mix and stir at 500 r / min for 10 min until homogeneous to obtain a second mixture. Add the eutectic solvent stock solution from step S1 to the second mixture at a mass ratio of 15:100. Mix and stir at 700 r / min for 20 min to obtain a continuous phase solution.

[0061] Step 5: Add the graphene oxide suspension from Step 2 to the continuous phase solution from Step 4, mix and stir at 800 r / min for 15 min, and after stirring evenly, add the nano silica suspension from Step 3, mix and stir at 1000 r / min for 30 min to obtain the functionalized continuous phase solution.

[0062] Step 6: Heat polydimethylsiloxane to 40°C and stir at 300 r / min for 10 min. After stirring evenly, use a dropper to add polydimethylsiloxane to the functionalized continuous phase solution in step 5 at a rate of 1 mL / min, while stirring at 1500 r / min for 30 min to obtain a conventional emulsion solution.

[0063] Step 7: Transfer the conventional emulsion solution from Step 6 to a homogenizer and homogenize it at 17500 r / min for 20 min. Then, treat it under vacuum at -0.08 MPa for 10 min to remove trapped air and obtain the nano-emulsion composite solution.

[0064] Step 8: Transfer the nanoemulsion composite liquid to a sealed reactor, and then inject CO2 gas into the reactor at a flow rate of 1L / min for 120min to obtain CO2 nanoemulsion composite liquid.

[0065] Step 9: Analyze the thermal conductivity and CO2 fixation rate of the CO2 nanoemulsion composite liquid obtained in Step 8.

[0066] Example 3

[0067] Step 1: Transfer choline chloride and ethylene glycol to a glass reactor with a mass ratio of choline chloride to ethylene glycol of 1:1.5. Heat to 60°C and stir at 550 r / min for 1.5 h until a transparent and homogeneous liquid is formed, thus obtaining a eutectic solvent stock solution.

[0068] Step 2: Mix graphene oxide and deionized water at a mass ratio of 0.5:10, and stir the mixture at 200 r / min for 1–10 min. Use an ultrasonic disperser with a pulse mode of 3 s on / 3 s off to ultrasonically treat the resulting mixture for a cumulative ultrasonic time of 40 min. During ultrasonic treatment, the water in the ultrasonic disperser is replaced every 5 min to control the water temperature below 35 ℃, ensuring sufficient dispersion of graphene oxide and avoiding the influence of excessively high temperatures on the properties of graphene oxide. The ultrasonically treated mixture yields a graphene oxide suspension.

[0069] Step 3: Add methanol to deionized water at a mass ratio of 25:100 and mix thoroughly to obtain a first mixture. Add nano-silica to the first mixture at a mass ratio of 0.1:10 and then treat it using the ultrasonic dispersion method described in Step 2 to obtain a nano-silica suspension.

[0070] Step 4: Add methanol to deionized water at a mass ratio of 25:100. Mix and stir at 500 r / min for 10 min until homogeneous to obtain a second mixture. Add the eutectic solvent stock solution from step S1 to the second mixture at a mass ratio of 15:100. Mix and stir at 700 r / min for 20 min to obtain a continuous phase solution.

[0071] Step 5: Add the graphene oxide suspension from Step 2 to the continuous phase solution from Step 4, mix and stir at 800 r / min for 15 min, and after stirring evenly, add the nano silica suspension from Step 3, mix and stir at 1000 r / min for 30 min to obtain the functionalized continuous phase solution.

[0072] Step 6: Heat polydimethylsiloxane to 40°C and stir at 300 r / min for 10 min. After stirring evenly, use a dropper to add polydimethylsiloxane to the functionalized continuous phase solution in step 5 at a rate of 1 mL / min, while stirring at 1500 r / min for 30 min to obtain a conventional emulsion solution.

[0073] Step 7: Transfer the conventional emulsion solution from Step 6 to a homogenizer and homogenize it at 17500 r / min for 20 min. Then, treat it under vacuum at -0.08 MPa for 10 min to remove trapped air and obtain the nano-emulsion composite solution.

[0074] Step 8: Transfer the nanoemulsion composite liquid to a sealed reactor, and then inject CO2 gas into the reactor at a flow rate of 1L / min for 120min to obtain CO2 nanoemulsion composite liquid.

[0075] Step 9: Analyze the thermal conductivity and CO2 fixation rate of the CO2 nanoemulsion composite liquid obtained in Step 8.

[0076] Example 4

[0077] Step 1: Transfer choline chloride and ethylene glycol to a glass reactor with a mass ratio of choline chloride to ethylene glycol of 1:1.5. Heat to 60°C and stir at 550 r / min for 1.5 h until a transparent and homogeneous liquid is formed, thus obtaining a eutectic solvent stock solution.

[0078] Step 2: Mix graphene oxide and deionized water at a mass ratio of 0.5:10, and stir the mixture at 200 r / min for 1–10 min. Use an ultrasonic disperser with a pulse mode of 3 s on / 3 s off to ultrasonically treat the resulting mixture for a cumulative ultrasonic time of 40 min. During ultrasonic treatment, the water in the ultrasonic disperser is replaced every 5 min to control the water temperature below 35 ℃, ensuring sufficient dispersion of graphene oxide and avoiding the influence of excessively high temperatures on the properties of graphene oxide. The ultrasonically treated mixture yields a graphene oxide suspension.

[0079] Step 3: Add methanol to deionized water at a mass ratio of 25:100 and mix thoroughly to obtain a first mixture. Add nano-silica to the first mixture at a mass ratio of 0.3:10 and then treat it using the ultrasonic dispersion method described in Step 2 to obtain a nano-silica suspension.

[0080] Step 4: Add methanol to deionized water at a mass ratio of 25:100. Mix and stir at 500 r / min for 10 min until homogeneous to obtain a second mixture. Add the eutectic solvent stock solution from step S1 to the second mixture at a mass ratio of 15:100. Mix and stir at 700 r / min for 20 min to obtain a continuous phase solution.

[0081] Step 5: Add the graphene oxide suspension from Step 2 to the continuous phase solution from Step 4, mix and stir at 800 r / min for 15 min, and after stirring evenly, add the nano silica suspension from Step 3, mix and stir at 1000 r / min for 30 min to obtain the functionalized continuous phase solution.

[0082] Step 6: Heat polydimethylsiloxane to 40°C and stir at 300 r / min for 10 min. After stirring evenly, use a dropper to add polydimethylsiloxane to the functionalized continuous phase solution in step 5 at a rate of 1 mL / min, while stirring at 1500 r / min for 30 min to obtain a conventional emulsion solution.

[0083] Step 7: Transfer the conventional emulsion solution from Step 6 to a homogenizer and homogenize it at 17500 r / min for 20 min. Then, treat it under vacuum at -0.08 MPa for 10 min to remove trapped air and obtain the nano-emulsion composite solution.

[0084] Step 8: Transfer the nanoemulsion composite liquid to a sealed reactor, and then inject CO2 gas into the reactor at a flow rate of 1L / min for 120min to obtain CO2 nanoemulsion composite liquid.

[0085] Step 9: Analyze the thermal conductivity and CO2 fixation rate of the CO2 nanoemulsion composite liquid obtained in Step 8.

[0086] Example 5

[0087] Step 1: Transfer choline chloride and ethylene glycol to a glass reactor with a mass ratio of choline chloride to ethylene glycol of 1:1.5. Heat to 60°C and stir at 550 r / min for 1.5 h until a transparent and homogeneous liquid is formed, thus obtaining a eutectic solvent stock solution.

[0088] Step 2: Mix graphene oxide and deionized water at a mass ratio of 0.5:10, and stir the mixture at 200 r / min for 1–10 min. Use an ultrasonic disperser with a pulse mode of 3 s on / 3 s off to ultrasonically treat the resulting mixture for a cumulative ultrasonic time of 40 min. During ultrasonic treatment, the water in the ultrasonic disperser is replaced every 5 min to control the water temperature below 35 ℃, ensuring sufficient dispersion of graphene oxide and avoiding the influence of excessively high temperatures on the properties of graphene oxide. The ultrasonically treated mixture yields a graphene oxide suspension.

[0089] Step 3: Add methanol to deionized water at a mass ratio of 25:100 and mix thoroughly to obtain a first mixture. Add nano-silica to the first mixture at a mass ratio of 0.6:10 and then treat it using the ultrasonic dispersion method described in Step 2 to obtain a nano-silica suspension.

[0090] Step 4: Add methanol to deionized water at a mass ratio of 25:100. Mix and stir at 500 r / min for 10 min until homogeneous to obtain a second mixture. Add the eutectic solvent stock solution from step S1 to the second mixture at a mass ratio of 15:100. Mix and stir at 700 r / min for 20 min to obtain a continuous phase solution.

[0091] Step 5: Add the graphene oxide suspension from Step 2 to the continuous phase solution from Step 4, mix and stir at 800 r / min for 15 min, and after stirring evenly, add the nano silica suspension from Step 3, mix and stir at 1000 r / min for 30 min to obtain the functionalized continuous phase solution.

[0092] Step 6: Heat polydimethylsiloxane to 40°C and stir at 300 r / min for 10 min. After stirring evenly, use a dropper to add polydimethylsiloxane to the functionalized continuous phase solution in step 5 at a rate of 1 mL / min, while stirring at 1500 r / min for 30 min to obtain a conventional emulsion solution.

[0093] Step 7: Transfer the conventional emulsion solution from Step 6 to a homogenizer and homogenize it at 17500 r / min for 20 min. Then, treat it under vacuum at -0.08 MPa for 10 min to remove trapped air and obtain the nano-emulsion composite solution.

[0094] Step 8: Transfer the nanoemulsion composite liquid to a sealed reactor, and then inject CO2 gas into the reactor at a flow rate of 1L / min for 120min to obtain CO2 nanoemulsion composite liquid.

[0095] Step 9: Analyze the thermal conductivity and CO2 fixation rate of the CO2 nanoemulsion composite liquid obtained in Step 8.

[0096] The CO2 nanoemulsion composite liquids prepared in Examples 1-5 using the above preparation method were compared in performance. The comparative proportions in the table below are prepared according to the ratios of the examples, but without emulsification treatment:

[0097] Table 1. Thermal conductivity and CO2 fixation rate of CO2 nanoemulsion composite liquid with added graphene oxide and nano-silica at 25°C, 35°C, 45°C, and 55°C.

[0098]

[0099] Table 1 presents the test results of thermal conductivity and CO2 fixation rate for Examples 1-5 and the comparative example within the temperature range of 25-55℃. As shown in the table, the thermal conductivity of all examples increases with increasing temperature, while the CO2 fixation rate decreases with increasing temperature, consistent with the temperature dependence of liquid-phase thermal conductivity and gas dissolution. With the increase of the amount of graphene oxide and nano-silica, both performance indicators of the composite liquid improve simultaneously. Example 5 achieves a thermal conductivity of 0.63 W / m·K and a CO2 fixation rate of 2.10 mol / L at 25℃, the best among all examples. Particularly noteworthy is that the comparative example, although using the same formulation as the examples but without emulsification, has a thermal conductivity of only 0.41 W / m·K and a CO2 fixation rate of only 1.20 mol / L at 25℃, significantly lower than all examples, indicating that the nano-emulsion structure is the key to endowing the composite liquid with high thermal conductivity and high carbon fixation performance. All data in Table 1 fall within the scope of protection of the claims of this invention, fully verifying the reliability and advancement of the technical solution of this invention.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A thermally conductive and carbon-fixing dual-effect nanoemulsion composite liquid, characterized in that, By weight, the components include: 30-75 parts deionized water, 5-25 parts methanol, 2.5-10 parts choline chloride, 5-30 parts ethylene glycol, 5-20 parts polydimethylsiloxane, 0.01-5 parts graphene oxide, and 0.1-10 parts nano-silica. The composite liquid is a CO2-loaded nanoemulsion system.

2. The thermally conductive-carbon-fixing dual-effect nanoemulsion composite liquid according to claim 1, characterized in that, Choline chloride and ethylene glycol are mixed at a mass ratio of 1:(1.2~2.5) to form a eutectic solvent, which serves as a component of the continuous phase of the composite liquid.

3. The thermally conductive-carbon-fixing dual-effect nanoemulsion composite liquid according to claim 1, characterized in that, The nano-silica has a particle size of 10nm~500nm and a specific surface area of ​​25m² / g~400m² / g.

4. The thermally conductive-carbon-fixing dual-effect nanoemulsion composite liquid according to claim 1, characterized in that, The emulsion droplet size of the composite liquid is 50nm~300nm, and the contact angle of the nano-silica is maintained at 60°~90°.

5. The CO2 nanoemulsion composite liquid according to claim 1, characterized in that, The composite liquid has a thermal conductivity of 0.4 W / m·K to 0.85 W / m·K and a CO2 fixation rate of 1.1 mol / L to 2.9 mol / L.

6. A method for preparing a thermally conductive-carbon-fixing dual-effect nanoemulsion composite liquid as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Preparation of eutectic solvent stock solution: Mix choline chloride and ethylene glycol at a mass ratio of 1:(1.2~2.5), heat to 55~85℃, and stir at 300~750r / min for 1~2h until a transparent homogeneous liquid is formed, thus obtaining the eutectic solvent stock solution; Step 2: Preparation of graphene oxide suspension: Mix graphene oxide and deionized water at a mass ratio of (0.01~5):10, stir at 200 r / min for 1~10 min, and then treat with ultrasonic dispersion to obtain graphene oxide suspension; Step 3: Preparation of nano-silica suspension: Methanol and deionized water are mixed evenly at a mass ratio of (15~30):100 to obtain a first mixture. Nano-silica is mixed with the first mixture at a mass ratio of (0.1~3):10 and treated with the ultrasonic dispersion method described in Step 2 to obtain nano-silica suspension. Step 4: Preparation of continuous phase solution: Mix methanol and deionized water at a mass ratio of (15~30):100, stir at 500 r / min for 5~15 min to obtain a second mixture, add the eutectic solvent stock solution from step 1 to the second mixture, the mass ratio of the eutectic solvent stock solution to the second mixture is (10~25):100, stir at 700 r / min for 10~25 min to obtain a continuous phase solution; Step 5: Preparation of functionalized continuous phase solution: Add the graphene oxide suspension from step 2 to the continuous phase solution from step 4, stir at 800 r / min for 10-25 min, then add the nano silica suspension from step 3, stir at 1000 r / min for 20-40 min to obtain the functionalized continuous phase solution. Step 6: Preparation of conventional emulsion solution: Heat polydimethylsiloxane to 30~45℃ and stir at 300r / min for 10min. Then, add it dropwise to the functionalized continuous phase solution of step 5 at a flow rate of 1~2mL / min using a dropper. Stir at 1500r / min for 20~40min during the dropwise addition to obtain a conventional emulsion solution. Step 7: Preparation of nanoemulsion composite liquid: Transfer the conventional emulsion solution from step 6 to a homogenizer and homogenize it at a high speed of 7500~20000 r / min for 5~30 min. Then, treat it under vacuum conditions of -0.08MPa for 5~20 min to remove the trapped air and obtain the nanoemulsion composite liquid. Step 8, CO2 loading: Transfer the nanoemulsion composite liquid from step 7 to a sealed reactor, and introduce CO2 gas into the reactor at a flow rate of 0.1~1.5L / min for 20~200min to obtain CO2 nanoemulsion composite liquid.

7. The preparation method according to claim 6, characterized in that, In steps 2 and 3, the ultrasonic dispersion method is as follows: an ultrasonic disperser is used with a pulse mode of 3s on and 3s off, the ultrasonic frequency is 20kHz~60kHz, the ultrasonic power is 150W~500W, and the ultrasonic time is accumulated for 30~60 minutes; during the ultrasonic treatment, the water in the ultrasonic disperser is replaced every 2 minutes to 5 minutes to control the water temperature in the ultrasonic disperser to be below 35℃.

8. The preparation method according to claim 6, characterized in that, In step 6, the viscosity of the polydimethylsiloxane after heating to 30~45℃ is 0.5~10mPa·s.

9. The preparation method according to claim 6, characterized in that, In step 7, after vacuum treatment at -0.08MPa, the volume of the obtained CO2 nanoemulsion composite liquid is maintained at 95%~99% of the volume before vacuum treatment.

10. The preparation method according to claim 6, characterized in that, In step 1, the mass ratio of choline chloride to ethylene glycol is 1:1.5, the heating temperature is 60℃, the stirring speed is 550 r / min, and the stirring time is 1.5 h. In step 7, the homogenization and emulsification speed is 17500 r / min, the homogenization time is 20 min, and the vacuum treatment time is 10 min; In step 8, the CO2 gas flow rate is 1 L / min, and the gas flow time is 120 min.

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