Preparation method and application of organic molecule intercalated MgAlZr-LDHs type heat preservation agent

Abstract

The invention discloses a preparation method and application of an organic molecule intercalated MgAlZr-LDHs type heat preservation agent, and belongs to the field of geothermal well cementing admixtures. The method comprises the following steps: adding soluble magnesium salt, aluminum salt and zircon salt into deionized water, uniformly stirring to prepare a salt solution, and mixing a sodium hydroxide solution and a sodium carbonate solution to prepare an alkali solution; dropwise adding a salt solution and an alkali solution into the three-necked flask at the same time, and carrying out a nucleation reaction on the mixed solution at a certain temperature for a certain time; repeatedly washing, separating and drying the crystallized product to obtain a powder sample; calcining the powder sample in a muffle furnace, and treating with an organic solution; and repeatedly washing the reaction product with deionized water, drying, and grinding to obtain the product. The LDHs type heat preservation agent is prepared through a coprecipitation method, organic molecules are intercalated through an ion exchange method, the infrared absorption performance of the LDHs type heat preservation agent is improved, the heat conductivity of well cementation cement stone can be reduced through the heat preservation agent, and effective utilization of geothermal resources is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of geothermal well cementing admixtures, and relates to a preparation method of a high-temperature resistant thermal insulation agent for geothermal well cementing, and in particular to a preparation method and application of an organic molecule intercalated MgAlZr-LDHs type thermal insulation agent. Background Art

[0002] Geothermal energy is a huge "green energy treasure trove" hidden inside the earth. It is the second largest clean energy after solar energy. It not only has large reserves and wide distribution, but also has the advantages of being green, environmentally friendly, and renewable. At the same time, geothermal energy is one of the five non-carbon-based energy sources, which plays a vital role in the transformation of my country's energy system and the realization of the "dual carbon" goal. The development and utilization of geothermal energy has good social and environmental benefits, huge market potential, and broad development prospects. Therefore, geothermal energy is increasingly valued by people.

[0003] Due to the late start of geothermal development in China and the lack of experience in the effective utilization of geothermal energy, huge heat losses are usually caused during the exploitation of geothermal wells. According to estimates, if the heat loss of the exploitation well is reduced by 1~2℃, geothermal resources can be utilized to the maximum extent, which is equivalent to saving 82,368 tons of raw coal and reducing carbon dioxide emissions by 302,290.56 tons, which will achieve good economic and social benefits. Therefore, developing a heat preservation agent suitable for geothermal well cementing to reduce heat loss during geothermal well exploitation can greatly promote the full development and effective utilization of geothermal resources.

[0004] The anionic layered two-dimensional nanomaterial is a dihydroxy composite metal oxide, referred to as LDHs, which is an important new type of inorganic functional material. Its special chemical composition determines its significant absorption effect on infrared. Infrared absorption materials play an important role in improving thermal insulation. In daily life, they are often used in agricultural films to keep crops warm and increase yield. In order to improve the infrared absorption capacity of LDHs, the exchangeability of anions between LDHs layers can be used to insert other organic molecules with strong infrared absorption properties and intercalation between LDHs layers, which can greatly improve the thermal insulation effect.

[0005] The present invention proposes for the first time to prepare an organic molecule intercalated MgAlZr-LDHs type heat preservation agent and use it in geothermal well cementing engineering, which is of great significance for the effective utilization of geothermal resources. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing an organic molecule intercalated MgAlZr-LDHs type thermal insulation agent. The method has reliable principle and is easy to operate. The LDHs type high temperature resistant thermal insulation agent is prepared by a coprecipitation method using soluble magnesium salt, aluminum salt and zirconium salt, and the infrared absorption capacity of the thermal insulation agent is improved by intercalating organic molecules by an ion exchange method, so as to prepare a thermal insulation agent with good infrared absorption performance. The method not only solves the deficiency that the existing thermal insulation materials cannot be applied to geothermal well cementing, but also reduces the loss of geothermal energy, thereby realizing the effective utilization of geothermal resources.

[0007] Another object of the present invention is to provide the use of the organic molecule intercalated MgAlZr-LDHs type thermal insulation agent in geothermal well cementing.

[0008] In order to achieve the above technical objectives, the present invention adopts the following technical solutions.

[0009] A method for preparing an organic molecule intercalated MgAlZr-LDHs type thermal insulation agent comprises the following steps in sequence: S1. Add soluble magnesium salt, soluble aluminum salt and soluble zirconium salt to deionized water in a certain proportion and stir evenly to prepare a salt solution, and mix sodium hydroxide solution and sodium carbonate solution in a certain proportion to prepare an alkaline solution; S2, adding the salt solution and the alkaline solution to the three-necked flask at an appropriate speed at the same time, stirring vigorously until the pH of the mixed solution reaches a specified value, and then stopping the addition of the alkaline solution; S3, continuing to stir the mixed solution under certain temperature and time conditions to perform a nucleation reaction to allow the crystal nuclei to grow; S4, repeatedly washing the crystallized solid precipitate product obtained in step S3 with deionized water until it becomes neutral, centrifuging, and drying at a certain temperature to obtain a MgAlZr-LDHs powder sample; S5, placing the MgAlZr-LDHs powder sample in a muffle furnace, calcining it at a certain temperature for a period of time, and then treating the calcined MgAlZr-LDHs powder sample with an organic solution to cause an ion exchange reaction; S6. The reaction product obtained in step S5 is repeatedly washed with deionized water, dried, and ground to obtain an organic molecule intercalated MgAlZr-LDHs type thermal insulation agent.

[0010] In step S1, the soluble magnesium salt is one or a mixture of magnesium chloride (MgCl2), magnesium hydroxide (Mg(OH)2), magnesium carbonate (MgCO3), magnesium nitrate hexahydrate (Mg(NO3)2·6H2O), the soluble aluminum salt is one or a mixture of aluminum hydroxide (Al(OH)3), aluminum nitrate nonahydrate (Al(NO3)3·9H2O), aluminum chloride hexahydrate (AlCl3·6H2O), the soluble zirconium salt is one or a mixture of zirconium sulfate Zr(SO4)2, zirconium nitrate Zr(NO3)4, with Mg 2+ 、Al 3+ 、Zr 4+ The above-mentioned soluble magnesium salt, soluble aluminum salt and soluble zirconium salt are mixed in a molar ratio of 2~4:0.5~1:0.1~0.5; the concentration of the sodium hydroxide solution is 0.5~2mol / L, the concentration of the sodium carbonate solution is 0.1~2mol / L, and the mixing volume ratio of the sodium hydroxide solution and the sodium carbonate solution is 0.5~4:1.

[0011] In the step S2, when the pH of the mixed solution is 9-11, the addition of the alkaline solution is stopped.

[0012] In the step S3, the crystallization temperature is 60-120° C., and the crystallization time is 5-9 hours.

[0013] In the step S4, the drying condition is to dry at 50° C. under normal pressure for 24 to 48 hours to obtain a MgAlZr-LDHs powder sample.

[0014] In the step S5, the calcination temperature of the MgAlZr-LDHs powder sample in the muffle furnace is 200-500° C., and the calcination time is 3-6 hours.

[0015] In step S5, the organic solution is an ethanol solution of organic molecules, and the organic molecules are acridine (C 13 H9N), benzothiophene (C8H6S), porphyrin (CHN8OS4), aniline (C6H5NH2) or a mixture thereof, the MgAlZr-LDHs powder sample and the organic molecule are weighed at a mass ratio of 0.5-3.5:1, the reaction temperature is 70-120°C, and the reaction time is 0.5-6 hours.

[0016] In step S6, the drying process is performed by using a vacuum freeze dryer at -60°C for 36 to 72 hours.

[0017] An organic molecule intercalated MgAlZr-LDHs type heat preservation agent is applied to geothermal well cementing, and the process is as follows: According to a certain formula, the heat preservation agent is added to cement to make cement slurry. As the cementing process in the cementing operation proceeds, the cement slurry mixed with the heat preservation agent enters the formation and forms cement stone for cementing. The heat preservation agent reduces the thermal conductivity of the cement stone for cementing, effectively reduces the heat loss rate of geothermal energy, improves the heat preservation effect of the cement stone for cementing, and thus realizes the effective utilization of geothermal energy. In addition, the heat preservation agent can also enhance the protection of the well wall, not only reducing the impact of thermal stress on the wellbore, but also ensuring the integrity of the wellbore and extending the service life of the wellbore.

[0018] The thermal insulation performance of the organic molecule intercalated MgAlZr-LDHs type thermal insulation agent in the cementing process is achieved through the following ways: (1) Energy storage of interlayer water: Due to the special interlayer structure of LDHs materials, there is a large amount of interlayer water and adsorbed water between the layers. During the cementing process of geothermal wells, the thermal insulation added to the cement can store the heat dissipated in the geothermal energy, thereby effectively reducing the energy loss of geothermal energy. (2) Magnesium, aluminum, and zirconium metal hydroxides are common thermal insulation materials (the thermal conductivity of zirconium metal oxide is only 2-3 W / (m·K)). LDHs prepared using these elements have good thermal insulation properties. When used, they can not only effectively reduce heat loss, but also improve the stability of the material. Thermal insulation materials containing zirconium can not only withstand higher temperatures, but also provide longer protection effects. (3) Absorption: The special interlayer structure of LDHs enables them to have anion exchange capacity, and the insertion of organic molecules with excellent infrared absorption effect (acridine, benzothiophene, porphyrin, aniline, etc.) between the layers can significantly improve the thermal insulation performance of LDHs. Among them, the C=C (1600-1650cm⁻¹), NH (3200-3400cm⁻¹) and C=N (1500-1600cm⁻¹) bonds contained in acridine, benzothiophene, porphyrin and aniline respectively have strong absorption characteristics for infrared rays in multiple infrared bands; in addition, the above molecules are all macrocyclic or heterocyclic compounds, in which the highly conjugated π electron system has a strong absorption capacity for infrared rays, which is conducive to absorbing and storing the energy radiated by geothermal energy, so that the cementing cement stone produces a micro "greenhouse effect", preventing heat loss, thereby achieving a better thermal insulation effect.

[0019] Therefore, the thermal insulation performance of the organic molecule intercalated MgAlZr-LDHs type thermal insulation agent during geothermal well cementing operations is the result of the mutual promotion of multiple effects.

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention adopts a co-precipitation method and an ion exchange method, and uses soluble aluminum salt, magnesium salt, zirconium salt, sodium hydroxide, sodium carbonate and organic molecules with excellent infrared absorption effect as main raw materials to prepare an organic molecule intercalated MgAlZr-LDHs type high temperature resistant admixture for cementing, which has the advantages of uniform components, controllable precipitation particle size, good dispersibility, etc. (2) The MgAlZr-LDHs type thermal insulation agent using organic molecular intercalation can reduce the thermal conductivity of cementing stone, prevent the loss of geothermal energy, and effectively reduce the heat loss rate of geothermal energy, which not only improves its application value and scope, but also provides new ideas for the development, design and application of LDHs materials; (3) The present invention is reasonable, easy to implement, low-cost, and highly reproducible. The obtained organic molecule intercalated MgAlZr-LDHs type thermal insulation agent meets the requirements of green chemistry, has good thermal insulation performance, is suitable for cement-based materials, and has potential application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The XRD test results of different embodiments are shown in FIG.

[0022] Figure 2 , Figure 3 , Figure 4 The scanning electron microscope images are respectively of the thermal insulation agents prepared in the comparative example, example 1 and example 2. DETAILED DESCRIPTION

[0023] The present invention is further described below with reference to the accompanying drawings and examples, so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments, and for those skilled in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, they are all protected.

[0024] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0025] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0026] Comparative Example According to n(Mg 2+ ): n(Al 3+ ):n(Zr 4+)=2:1:0.5 molar ratio, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and Zr(SO4)2 were weighed respectively and dissolved in 200mL deionized water to obtain salt solution A, and 2mol / L NaOH solution and 0.5mol / L Na2CO3 solution were mixed in a volume ratio of 1:1 to form alkaline solution B, and the salt solution A and the alkaline solution B were added dropwise to a three-necked flask containing 20ml deionized water at an appropriate speed under stirring conditions, and the pH value of the mixed solution was kept at about 10. After the addition was completed, stirring was continued at 90°C for 6h to form a crystallized solution; the crystallized solid precipitate product was repeatedly washed with deionized water until neutral, centrifuged, and then the filter cake was freeze-dried at -60°C for 48h to obtain a MgAlZr-LDHs powder sample.

[0027] Example 1 According to n(Mg 2+ ): n(Al 3+ ): n(Zr 4+ )=3:0.8:0.1 in molar ratio, Mg(NO3)2·6H2O, Al(NO3)3·9H2O, and Zr(SO4)2 were weighed respectively and dissolved in about 200mL deionized water to obtain salt solution A, and 2mol / L NaOH solution and 0.5mol / L Na2CO3 solution were mixed in a volume ratio of 1:1 to form alkaline solution B, and the salt solution A and the alkaline solution B were added dropwise to a three-necked flask containing 20ml deionized water at an appropriate speed under stirring conditions, and the pH value of the mixed solution was kept at about 10. After the addition was completed, stirring was continued at 90°C for 6h to form a crystallized solution; after the reaction was completed, the crystallized solid precipitate product was repeatedly washed with deionized water until neutral, centrifuged, and the filter cake was dried in an oven at 50°C for 24h to obtain a MgAlZr-LDHs powder sample. The MgAlZr-LDHs powder sample was placed in a muffle furnace and calcined at 500°C for 4 hours. The calcined MgAlZr-LDHs powder sample, benzothiophene and porphyrin were weighed in a mass ratio of 1.5:1:0.2, and the benzothiophene and porphyrin were dissolved in 200 ml of ethanol at 60°C to prepare a mixed organic solution. After they were completely dissolved, the calcined MgAlZr-LDHs powder sample was added, and stirring was continued for 0.5h to mix them evenly. The solution was then transferred into a hydrothermal reactor and continued to react at 120°C for 4h. After the reaction was completed, the precipitated product was centrifuged and washed to neutrality, and vacuum freeze-dried to obtain BB@MgAlZr-LDHs.

[0028] Example 2 According to n(Mg 2+ ): n(Al 3+ ):n(Zr 4+)=4:0.5:0.3 molar ratio, MgCl2, AlCl3·6H2O, Zr(NO3)4 were weighed respectively and dissolved in about 200mL deionized water to obtain salt solution A, and 2mol / L NaOH solution and 0.5mol / L Na2CO3 solution were mixed in a volume ratio of 1:1 to prepare alkaline solution B, and the salt solution A and the alkaline solution B were added dropwise to a three-necked flask containing 20ml deionized water at an appropriate speed under stirring conditions, and the pH of the mixed solution was kept at about 10. After the addition was completed, stirring was continued at 90°C for 6h to form a crystallized solution; after the reaction was completed, the crystallized solid precipitate product was repeatedly washed with deionized water until neutral, centrifuged, and the filter cake was dried in an oven at 50°C for 24h After that, a MgAlZr-LDHs powder sample was obtained, and then the MgAlZr-LDHs powder sample was placed in a muffle furnace. After calcining at 500°C for 4 hours, the calcined MgAlZr-LDHs powder sample, aniline and acridine were weighed respectively in a mass ratio of 1:0.5:0.5, and aniline and acridine were dissolved in 200 ml of ethanol at 60°C to prepare a mixed organic solution. After they were completely dissolved, the calcined MgAlZr-LDHs powder sample was added, and stirring was continued for 0.5h to mix them evenly. Then the solution was transferred into a hydrothermal reactor and the reaction was continued at 90°C for 6h. After the reaction was completed, the precipitated product was centrifuged and washed to neutrality, and vacuum freeze-dried to obtain BA@MgAlZr-LDHs. Note: d(0.1), d(0.5), and d(0.9) represent the diameters corresponding to 10%, 50%, and 90% of the cumulative distribution of particle size, respectively. As can be seen from Table 1, before the organic molecule intercalation, the specific surface area of ​​the comparative MgAlZr-LDHs powder sample is small, and its surface area average particle size and volume average particle size are large; after the organic intercalation by ion exchange method, the particle size of Example 1 (BB@MgAlZr-LDHs) and Example 2 (BA@MgAlZr-LDHs) is effectively improved, and its specific surface area is significantly increased, while the surface area average particle size and volume average particle size are significantly reduced. In addition, the cumulative distribution of its particle size is consistent with the change of the surface area average particle size.

[0029] The thermal conductivity test of the organic molecule intercalated MgAlZr-LDHs type thermal insulation agent is as follows: The heat preservation agents prepared in the comparative example, Example 1 and Example 2 were added to the cementing cement at a mass ratio of 1:100, and the cement paste was prepared according to the GB / T 19139-2012 standard, poured into a 50mm×50mm×10mm mold, cured at room temperature for 24 hours, and transferred to a curing box at 90°C and 95% humidity after demoulding for curing to 28 days. Then, the surface of the cement thermal conductivity test block was polished and flattened using sandpaper of different meshes (180 mesh, 400 mesh, 800 mesh, 1500 mesh, 2000 mesh), and the thermal conductivity test was carried out at 30°C, 60°C, 90°C, 120°C and 150°C using a thermal conductivity tester, and finally the thermal conductivity was calculated according to the sample thickness, temperature difference and thermal conduction time.

[0030] The test results of thermal conductivity of the comparative example and different embodiments are shown in Table 2. As can be seen from Table 2, the thermal conductivity of Example 1 is the lowest, indicating that the BB@MgAlZr-LDHs thermal insulation agent prepared in Example 1 has the best thermal insulation performance. Note: The thermal conductivity of conventional density cement is about 0.8-1.2 W / (m·K), and the reduction rate = (0.8-thermal conductivity of the test group) / 0.8*100 Figure 1 The X-ray diffraction patterns of the comparative examples and different embodiments show that MgAlZr-LDHs and BB@MgAlZr-LDHs and BA@MgAlZr-LDHs after organic molecule intercalation all have characteristic diffraction peaks of hydrotalcite materials, among which the (003), (006), and (009) crystal plane diffraction peaks of Example 1 (BB@MgAlZr-LDHs) are all shifted to the direction of small angles, indicating that the organic molecules benzothiophene and porphyrin are successfully inserted into the interlayer structure of MgAlZr-LDHs, resulting in an increase in the interlayer spacing and a shift in the diffraction peaks to small angles, so that the interlayers can accommodate more water molecules, increasing the water content of MgAlZr-LDHs, which is conducive to storing more heat energy. Unlike Example 1, there are fewer intercalated molecules in Example 2, so the interlayer spacing changes less and the crystal plane diffraction peaks change less, which is consistent with the less reduction in its thermal conductivity.

[0031] Figure 2 , Figure 3 , Figure 4 The microscopic morphologies of the comparative example (MgAlZr-LDHs), Example 1 (BB@MgAlZr-LDHs), and Example 2 (BA@MgAlZr-LDHs) are shown. It can be seen that the microscopic morphologies of all materials are lamellar stacking structures. Among them, the lamellar structure in the comparative example is relatively loose, and in Example 1, the intercalation structure is complete and the interlayer spacing is larger than that in the comparative example and Example 2 due to the influence of the intercalation molecules.

Claims

1. A method for preparing an organic molecule intercalated MgAlZr-LDHs type thermal insulation agent, comprising the following steps in sequence: S1. Add soluble magnesium salt, soluble aluminum salt and soluble zirconium salt to deionized water in a certain proportion and stir evenly to prepare a salt solution, and mix sodium hydroxide solution and sodium carbonate solution to prepare an alkaline solution; S2, adding the salt solution and the alkaline solution to the three-necked flask simultaneously, stirring vigorously until the pH of the mixed solution reaches a specified value, and then stopping the addition of the alkaline solution; S3, continuing to stir the mixed solution under certain temperature and time conditions to perform a nucleation reaction to allow the crystal nuclei to grow; S4, repeatedly washing the crystallized solid precipitate product obtained in step S3 with deionized water until it becomes neutral, centrifuging, and drying at a certain temperature to obtain a MgAlZr-LDHs powder sample; S5, calcining the MgAlZr-LDHs powder sample in a muffle furnace, and treating the calcined MgAlZr-LDHs powder sample with an organic solution to cause an ion exchange reaction; S6. The reaction product obtained in step S5 is repeatedly washed with deionized water, dried, and ground to obtain an organic molecule intercalated MgAlZr-LDHs type thermal insulation agent.

2. The method for preparing an organic molecule intercalated MgAlZr-LDHs type thermal insulation agent according to claim 1, characterized in that: In step S1, the soluble magnesium salt is one or a mixture of magnesium chloride, magnesium hydroxide, magnesium carbonate, and magnesium nitrate hexahydrate; the soluble aluminum salt is one or a mixture of aluminum hydroxide, aluminum nitrate nonahydrate, and aluminum trichloride hexahydrate; the soluble zirconium salt is one or a mixture of zirconium sulfate and zirconium nitrate, with Mg 2+ 、Al 3+ 、Zr 4+ The above-mentioned soluble magnesium salt, soluble aluminum salt and soluble zirconium salt are mixed in a molar ratio of 2~4:0.5~1:0.1~0.5; the concentration of the sodium hydroxide solution is 0.5~2mol / L, the concentration of the sodium carbonate solution is 0.1~2mol / L, and the mixing volume ratio of the sodium hydroxide solution and the sodium carbonate solution is 0.5~4:

1.

3. The method for preparing an organic molecule intercalated MgAlZr-LDHs type thermal insulation agent according to claim 1, characterized in that: In the step S2, when the pH of the mixed solution is 9-11, the addition of the alkaline solution is stopped.

4. The method for preparing an organic molecule intercalated MgAlZr-LDHs type thermal insulation agent according to claim 1, characterized in that: In the step S3, the crystallization temperature is 60-120° C., and the crystallization time is 5-9 hours.

5. The method for preparing an organic molecule intercalated MgAlZr-LDHs type thermal insulation agent according to claim 1, characterized in that: In step S4, the drying condition is 50° C. and normal pressure drying for 24 to 48 hours.

6. The method for preparing an organic molecule intercalated MgAlZr-LDHs type thermal insulation agent according to claim 1, characterized in that: In the step S5, the calcination temperature of the MgAlZr-LDHs powder sample in the muffle furnace is 200-500° C., and the calcination time is 3-6 hours.

7. The method for preparing an organic molecule intercalated MgAlZr-LDHs type thermal insulation agent according to claim 1, characterized in that: In step S5, the organic solution is an ethanol solution of organic molecules, the organic molecules are one or a mixture of acridine, benzothiophene, porphyrin, and aniline, the mass ratio of the MgAlZr-LDHs powder sample to the organic molecules is 0.5-3.5:1, the reaction temperature is 70-120°C, and the reaction time is 0.5-6 hours.

8. The method for preparing an organic molecule intercalated MgAlZr-LDHs type thermal insulation agent according to claim 1, characterized in that: In step S6, the drying process is performed by using a vacuum freeze dryer at -60°C for 36 to 72 hours.

9. The MgAlZr-LDHs type heat preservation agent with organic molecule intercalation prepared by the method of claim 1, 2, 3, 4, 5, 6, 7 or 8, characterized in that: The thermal insulation agent is applied to geothermal well cementing, and the process is as follows: the thermal insulation agent is added to cement to make cement slurry. As the cementing operation proceeds, the cement slurry mixed with the thermal insulation agent enters the formation and forms cement stone for cementing. The thermal insulation agent reduces the thermal conductivity of the cement stone for cementing, thereby improving the thermal insulation effect of the cement stone, thereby achieving effective utilization of geothermal energy.

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