Method for large-dose synthesis of porous magnesium oxide under mild conditions

Abstract

The invention discloses a method for large-dose synthesis of porous magnesium oxide under mild conditions, and belongs to the technical field of preparation of inorganic functional materials. The preparation method comprises the following steps: firstly, taking Na2CO3 and a magnesium source as raw materials to generate a magnesium carbonate trihydrate precursor, then adding NaOH, carrying out hydroxylation conversion reaction in a water bath to obtain a basic magnesium carbonate precursor, and finally calcining the basic magnesium carbonate precursor to prepare the porous magnesium oxide. According to the synthetic method, the whole reaction process is completed under mild conditions, high temperature and additive dependence in the prior art is broken through, large-dose synthesis of the porous magnesium oxide can be realized by accurately controlling reaction concentration, alkalinity and time parameters, hectogram-level mass production is supported, and the method is suitable for industrial production. In addition, according to the synthesis method, the morphology of the porous magnesium oxide can be controlled while the concentration is accurately regulated and controlled, the porous nanosheet or microflower-shaped magnesium oxide is selectively prepared, and the synthesis method has remarkable industrialization potential in the fields of catalyst carriers, gas adsorption, lithium battery additives and the like.

Description

Technical Field

[0001] This invention belongs to the field of inorganic functional material preparation technology, specifically relating to a method for synthesizing porous magnesium oxide in large doses under mild conditions. Background Technology

[0002] Magnesium oxide (MgO) is an important inorganic material with a high melting point, good chemical stability, and thermal conductivity, and is widely used in refractory materials, catalyst supports, adsorbents, pharmaceuticals, and environmental protection. In refractory materials, MgO is used in steelmaking furnace linings due to its high-temperature stability; in environmental protection, it can be used as an adsorbent for acidic gases; in catalysis, MgO supports can improve the dispersibility and activity of metal catalysts; in addition, nano-magnesium oxide is also used in antibacterial materials and lithium battery electrolyte additives.

[0003] Porous magnesium oxide (MgO) exhibits superior performance in adsorption and catalysis due to its high specific surface area and abundant pore structure. Current methods for synthesizing porous MgO mainly include: 1) Template method: using polymers or mesoporous silica as templates, the template is removed via a sol-gel method combined with calcination to form a porous structure; 2) Precipitation method: generating a precursor through the reaction of magnesium salts with alkali, followed by high-temperature decomposition to obtain porous MgO; porosity can be controlled by adjusting precipitation conditions; 3) Hydrothermal / solvothermal method: high-temperature reaction in a closed system to form a porous material with high crystallinity; 4) Biotemplate method: utilizing the porous structure of plants or biomass as a template to prepare eco-friendly porous MgO.

[0004] The preparation of porous magnesium oxide using basic magnesium carbonate (Mg5(CO3)4(OH)2·4H2O) precursor is an effective method. Its advantages lie in the ability to synthesize basic magnesium carbonate of various morphologies and sizes using a liquid-phase method. Furthermore, the morphology of the resulting magnesium oxide largely depends on the precursor, and the carbon dioxide and water vapor generated during calcination can promote the formation of macroporous and mesoporous pore structures, increasing the specific surface area of ​​the material. For example, in 2023, Kim YH et al. at Ajou University in South Korea synthesized ultra-high porosity urchin-like magnesium oxide particles using basic magnesium carbonate, and then constructed a hydration / dehydration thermal regeneration system of MgO / Mg(OH)2. Because the porous regions are filled and emptied during the reaction, structural collapse caused by volume changes during the reaction is effectively avoided, thus ensuring cycle stability and thermal efficiency.

[0005] Since the morphology, size, and pore structure of porous magnesium oxide depend on the effective synthesis of the precursor, basic magnesium carbonate, the large-scale synthesis of basic magnesium carbonate and the corresponding porous magnesium oxide under mild conditions is crucial for the commercial application of this type of material. Currently, the synthesis of porous magnesium oxide using the basic magnesium carbonate precursor method requires high-temperature hydrothermal or surfactant-mediated processes. For example, in 2022, Kang Ning et al. from Shenyang Jianzhu University prepared highly active porous magnesium oxide using high-temperature hydrothermal (100-180℃) and subsequent high-temperature sintering. However, this technique relies on a 100℃ hydrothermal reaction to generate the precursor, and the reaction must be carried out in a high-pressure closed reactor, resulting in high equipment costs and a heating / cooling cycle of 10-12 hours. Zhang Lichun et al. from Sichuan University used anhydrous sodium carbonate and magnesium chloride hexahydrate as raw materials to obtain flower-shaped MgO microspheres from the basic magnesium carbonate precursor through filtration, washing, drying, and calcination. However, this method still requires a reaction temperature exceeding 70℃ and necessitates the introduction of surfactants as morphology modifiers. The presence of surfactant residues may lead to a decrease in product purity.

[0006] Current research on the preparation of porous magnesium oxide attempts to lower the reaction temperature, but it still requires temperatures above 60°C or the addition of other additives. There is still a gap in the technology for mass production of porous magnesium oxide under mild conditions, especially lacking a synthesis method that simultaneously meets the requirements of a reaction temperature ≤50°C, no surfactant use throughout the process, high batch yield, and the ability to directionally prepare nanosheets or micro-flowers. Therefore, designing a technical route for the large-scale synthesis of porous magnesium oxide under mild conditions could provide a breakthrough solution for the low-cost, high-precision manufacturing of porous magnesium oxide. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention discloses a method for synthesizing porous magnesium oxide in large quantities under mild conditions. The synthesis method is carried out entirely under mild conditions, overcoming the limitations of high temperature and additive dependence in the prior art. By precisely controlling the reaction concentration, alkalinity, and time parameters, large-quantity synthesis of porous magnesium oxide can be achieved.

[0008] The technical solution of the present invention is as follows:

[0009] The purpose of this invention is to provide a method for synthesizing porous magnesium oxide in large quantities under mild conditions, comprising the following steps:

[0010] S1. Using any one of MgSO4·7H2O, Mg(NO3)2·6H2O or MgCl2·6H2O as the magnesium source, mix with Na2CO3 solution and stir the reaction at room temperature to 50℃ without surfactant to generate magnesium carbonate trihydrate precursor MgCO3·3H2O.

[0011] S2. Add solid NaOH to the mixture of S1 and carry out hydroxylation conversion reaction in a water bath at 30-50℃ to obtain the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O.

[0012] S3, calcined basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O, to obtain the porous magnesium oxide.

[0013] Furthermore, the concentrations of both the magnesium source and Na2CO3 in S1 are 0.5-2 mol / L.

[0014] Furthermore, the volume ratio of the magnesium source to the Na2CO3 solution in S1 is 1:1.

[0015] Furthermore, the amount of NaOH solid added in S2 is 0.6-0.8g of NaOH solid per 100mL of Na2CO3 solution.

[0016] Furthermore, when the solution reaction concentration is 0.5 mol / L, a fluffy basic magnesium carbonate precursor is obtained, which, after calcination, yields micron-sized flower-like porous magnesium oxide.

[0017] Furthermore, the specific surface area of ​​the micron-shaped porous magnesium oxide is ≥130 m². 2 / g, with a pore size distribution of 3-9nm.

[0018] Furthermore, when the solution reaction concentration is 2 mol / L and the amount of NaOH added is 0.8 g / 100 mL, a sheet-like basic magnesium carbonate precursor is obtained, which is then calcined to obtain nanosheet-like porous magnesium oxide.

[0019] Furthermore, the specific surface area of ​​the nanosheet-like porous magnesium oxide is 40-50 m². 2 / g.

[0020] Furthermore, the hydroxylation conversion reaction time in S2 is 5-7 hours.

[0021] Furthermore, the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O in S3 is calcined at 400-600℃.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. This invention innovatively presents a method for synthesizing porous magnesium oxide in large quantities under mild conditions. Under additive-free conditions ranging from room temperature to 50°C, the morphology of the basic magnesium carbonate precursor is directly controlled by adjusting concentration and time parameters. Simultaneously, precise alkalinity control facilitates the conversion of magnesium carbonate trihydrate to basic magnesium carbonate. Finally, calcination decomposes the precursor, releasing CO2 / H2O, naturally forming magnesium oxide with a macroporous-mesoporous hierarchical structure. The parameter combination design disclosed in this invention is the first to simultaneously solve the problems of morphology control and pore structure optimization under mild conditions, overcoming the dependence of existing porous magnesium oxide preparation processes on high temperatures and additives.

[0024] 2. The synthesis method designed in this invention achieves precise control of the morphology of porous magnesium oxide by adjusting the concentration under ambient temperature (25-50℃) and additive-free conditions, and the synthesized porous magnesium oxide possesses high specific surface area and controllable pore structure. When the raw material solution concentration is controlled to 0.5 mol / L, a fluffy precursor is generated, which, after calcination, yields micron-sized flower-like magnesium oxide with a specific surface area ≥130 m² / L. 2 / g, with a pore size distribution of 3-9nm; when the raw material solution concentration is 2mol / L and 0.8g / 100mL NaOH is used, a sheet-like precursor is generated, and the specific surface area of ​​the nanosheet magnesium oxide obtained after calcination can reach 40-50m². 2 / g. Furthermore, the additive-free process of this invention avoids circumventing the limitations of traditional methods, thus improving the pore cleanliness of the synthesized porous magnesium oxide, making it suitable for future applications in environmental adsorption or energy materials and other technical fields.

[0025] 3. The synthesis method provided by this invention has significant advantages in production and application. This method operates entirely at room temperature, significantly reducing energy consumption and equipment investment compared to traditional processes. Furthermore, this invention does not involve the use of additives; the CO2 / H2O gas generated from precursor decomposition naturally creates pores during calcination, improving material cycle stability while reducing raw material costs. It also eliminates the generation of high-COD wastewater, reducing post-processing steps and environmental pollution. Based on the above, the synthesis method of this invention supports the mass production of porous magnesium oxide at the 100-gram scale, overcoming the limitations of existing technologies in large-scale synthesis of nanosheets / microflowers under mild conditions, thus meeting the demands of large-scale production. Attached Figure Description

[0026] Figure 1 This is a SEM image of the micron-shaped porous magnesium oxide obtained in Example 4 of the present invention;

[0027] Figure 2 This is a SEM image of the nanosheet-like porous magnesium oxide prepared in Example 5 of the present invention;

[0028] Figure 3 This is a SEM image of the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O prepared in Example 4 of the present invention.

[0029] Figure 4 The XRD patterns of the products obtained from Na2CO3 solution and MgCl2·6H2O solution of different concentrations in the performance test of this invention are shown.

[0030] Figure 5 These are SEM images of the products obtained under different raw material solution concentrations during the performance testing of this invention.

[0031] Figure 6 These are X-ray diffraction patterns of products obtained at different conversion temperatures during the performance testing of this invention.

[0032] Figure 7 These are SEM images of products obtained at different conversion temperatures during the performance testing of this invention.

[0033] Figure 8 The XRD patterns of the products obtained with different conversion solution alkalinities in the performance test of this invention are shown below.

[0034] Figure 9 The XRD diffraction peaks of the product obtained when the alkalinity of the conversion solution was 0.4 g / 100 mL during the performance test of this invention are shown.

[0035] Figure 10 These are SEM images of products obtained with different conversion solution alkalinities during the performance testing of this invention.

[0036] Figure 11 These are the XRD patterns of products obtained at different conversion times during the performance testing of this invention;

[0037] Figure 12 These are SEM images of products obtained at different conversion times during the performance testing of this invention.

[0038] Figure 13 The XRD pattern of the finished product prepared by calcination of MgO is shown in the performance test of this invention.

[0039] Figure 14 These are SEM images of the finished product prepared by calcination of MgO during the performance testing of this invention.

[0040] Figure 15 N2 adsorption-desorption isotherms and pore size distribution diagrams of porous magnesium oxide microspheres prepared by the method described in this invention;

[0041] Figure 16 The N2 adsorption-desorption isotherm and pore size distribution of porous magnesium oxide nanosheets prepared by the method described in this invention are shown. Detailed Implementation

[0042] The present invention will be further described below with reference to preferred embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0043] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0044] In the quantitative experiments in the following examples, three independent replicate experiments were set up, and the average value of the results was taken.

[0045] Unless otherwise specified, the experimental methods in the following examples are conventional methods;

[0046] Example 1

[0047] This embodiment provides a method for synthesizing micron-sized flower-like porous magnesium oxide under mild conditions and in large doses. The specific steps are as follows:

[0048] (1) Mix 0.5 mol / L MgCl2·6H2O and 0.5 mol / L Na2CO3 solution at a volume ratio of 1:1, and stir the reaction at 25℃ without surfactant to generate magnesium carbonate trihydrate precursor MgCO3·3H2O.

[0049] (2) Add 0.6 g / 100 mL of NaOH solid to the mixed system of S1 according to the Na2CO3 solution, and carry out the hydroxylation conversion reaction in a 30℃ water bath for 7 h to obtain the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O.

[0050] (3) The micron-shaped porous magnesium oxide was prepared by calcining the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O at 400℃.

[0051] Example 2

[0052] This embodiment provides a method for synthesizing nanosheet-like porous magnesium oxide under mild conditions and in large doses. The specific steps are as follows:

[0053] (1) Mix 2 mol / L MgSO4·7H2O with 2 mol / L Na2CO3 solution at a volume ratio of 1:1, and stir the reaction at 50℃ without surfactant to generate magnesium carbonate trihydrate precursor MgCO3·3H2O.

[0054] (2) Add 0.8 g / 100 mL of NaOH solid to the mixed system of S1 according to the Na2CO3 solution, and carry out the hydroxylation conversion reaction in a 50℃ water bath for 5 h to obtain the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O.

[0055] (3) The nanosheet porous magnesium oxide was prepared by calcining the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O at 500℃.

[0056] Example 3

[0057] This embodiment provides a method for synthesizing porous magnesium oxide in large quantities under mild conditions. The specific steps are as follows:

[0058] (1) Mix 1.7 mol / L Mg(NO3)2·6H2O with 1.7 mol / L Na2CO3 solution at a volume ratio of 1:1, and stir the mixture at 38℃ without surfactant to generate magnesium carbonate trihydrate precursor MgCO3·3H2O.

[0059] (2) Add 0.7 g / 100 mL of NaOH solid to the mixed system of S1 according to the Na2CO3 solution, and carry out the hydroxylation conversion reaction in a 40℃ water bath for 6 h to obtain the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O.

[0060] (3) The porous magnesium oxide is prepared by calcining the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O at 600℃.

[0061] Example 4

[0062] This embodiment provides a 100-gram-scale test of micron-sized flower-shaped porous magnesium oxide:

[0063] First, prepare 1 L of 2 mol / L magnesium sulfate (magnesium nitrate or magnesium chloride) solution, then add 1 L of a mixed solution of 1.6 mol / L sodium carbonate and 0.8 mol / L sodium hydroxide, and allow the mixture to react at 50°C for 7 hours. After filtration and washing, the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O is obtained. Figure 3 As shown, the obtained precursor was finally sintered at 450℃ for 4 hours to obtain the target micron-sized flower-like porous magnesium oxide, as shown. Figure 1 As shown.

[0064] Example 5

[0065] This embodiment provides a 100-gram-scale test of nanosheet-shaped porous magnesium oxide:

[0066] First, prepare 1 L of 2 mol / L magnesium sulfate (magnesium nitrate or magnesium chloride) solution, then add 1 L of a mixed solution of 1.6 mol / L sodium carbonate and 1.2 mol / L sodium hydroxide, and allow the mixture to react at 50 °C for 7 h. After filtration and washing, obtain the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O. Finally, sinter the obtained precursor at 450 °C for 4 h to obtain the target nanosheet porous magnesium oxide. Figure 2 As shown.

[0067] Performance testing

[0068] 1. Concentration of different raw material solutions

[0069] Three different concentrations of Na2CO3 solutions (0.5M, 1M, 2M) were poured into 100mL of MgCl2·6H2O solution of the same concentration. After magnetic stirring for 10min, the magnesium carbonate trihydrate precursor MgCO3·3H2O was obtained. Then, it was converted in a water bath at 40℃ for 7h to prepare the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O.

[0070] like Figure 4 As shown, the XRD diffraction peaks of the obtained product are consistent with the diffraction peaks of the PDF standard card (025-0513). Therefore, it can be determined that MgCO3·3H2O can be converted into the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O at these three concentrations, and the conversion is basically complete.

[0071] Depend on Figure 5 SEM images of the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O prepared at different concentrations show that at low concentrations, the resulting product has a morphological structure similar to uniformly sized fluffy balls, which are formed by the accumulation of many plates. As the concentration of the reaction solution increases, the fluffy ball structure gradually disperses and transforms into plates.

[0072] 2. Different water bath conversion temperatures

[0073] A solution of 100 mL of 2 mol / L Na₂CO₃ and 2 g of NaOH solid was poured into 100 mL of 2 mol / L MgCl₂·6H₂O solution and magnetically stirred for 10 min to prepare the magnesium carbonate trihydrate precursor MgCO₃·3H₂O. Then, the precursor Mg₅(CO₃)₄(OH)₂·4H₂O was prepared by conversion in a water bath at 30, 40, and 50 °C for 7 h. The diffraction patterns of the products obtained at different temperatures were analyzed by XRD, and the morphological characteristics of the products obtained at different temperatures were observed by scanning electron microscopy (SEM).

[0074] like Figure 6 As shown, the XRD diffraction peaks of the products obtained in water baths at 30, 40, and 50°C are consistent with the diffraction peaks of the PDF standard card (025-0513). Therefore, it can be determined that the products obtained after conversion are all basic magnesium carbonate precursors Mg5(CO3)4(OH)2·4H2O.

[0075] Depend on Figure 7 It can be seen that, under the same conditions, the sheet-like structure of the products obtained at 30℃ and 40℃ is more obvious than that obtained at 50℃. The sheet-like structure of the sample at 50℃ is significantly thicker, while the product obtained at 40℃ is more aggregated than that at 30℃.

[0076] 3. Alkalinity of different conversion solutions

[0077] Using a controlled variable method, 100 mL of a solution containing 0.4 g, 0.6 g, and 0.8 g of solid NaOH mixed with 2 mol / L Na₂CO₃ was added to 100 mL of a solution containing 2 mol / L MgCl₂·6H₂O. The mixture was magnetically stirred for 10 min to prepare the magnesium carbonate trihydrate precursor MgCO₃·3H₂O. The product was then prepared by conversion in a 40℃ water bath for 7 h. The effects of different solid NaOH on the conversion of MgCO₃·3H₂O were determined by comparing the spectra using X-ray diffraction (XRD) and the effects of different solid NaOH on the morphology were observed by scanning electron microscopy (SEM).

[0078] like Figure 8 As shown, when 0.6 g and 0.8 g of NaOH solid were added, the XRD diffraction peaks of the resulting products matched the diffraction peaks of the PDF standard card (025-0513). Therefore, the product obtained under these conditions is the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O. However, when 0.4 g of NaOH was added, the XRD diffraction peaks of the resulting product did not match the diffraction peaks of the PDF standard card (025-0513) significantly. Figure 9 It can be seen that the XRD diffraction peaks of the product obtained by 0.4g NaOH are basically consistent with the diffraction peaks of the PDF standard card (020-0669). Therefore, it can be concluded that the majority of the product is the magnesium carbonate trihydrate precursor MgCO3·3H2O, and it contains a small amount of the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O. This indicates that the alkali can promote the conversion of the magnesium carbonate trihydrate precursor MgCO3·3H2O into the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O.

[0079] like Figure 10 As shown, the products obtained by adding 0.4g (a,b), 0.6g (c,d), and 0.8g (e,f) of NaOH solid were clearly prismatic, and their size was much larger than the other plate-like structures. It can be determined that the plate-like structures were formed by the aggregation of dispersed NaOH, and the size of the plate-like structures was affected by the size of the prismatic structures. The products obtained by adding 0.6g (c,d) and 0.8g (e,f) of NaOH solid had similar morphologies, but the morphology was significantly more regular and the distribution more uniform under the condition of 0.8g NaOH.

[0080] 4. Different conversion times

[0081] Using a controlled variable method, 100 mL of a solution containing 2 mol / L Na₂CO₃ and 0.8 g of solid NaOH was added to 100 mL of a 2 mol / L MgCl₂·6H₂O solution and magnetically stirred for 10 min to prepare the magnesium carbonate trihydrate precursor MgCO₃·3H₂O. The product was then prepared by conversion in a water bath at 40 °C for 30 min, 5 h, and 7 h. The effect of different water bath times on the conversion of MgCO₃·3H₂O was determined by comparing X-ray diffraction (XRD) patterns, and the effect of different NaOH solids on the morphology was observed by scanning electron microscopy (SEM).

[0082] like Figure 11 As shown, the main transformation of the magnesium carbonate trihydrate precursor MgCO3·3H2O to the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O occurs after the 5th hour, and is completed by the 7th hour. Based on the staged X-ray diffraction (XRD) pattern comparison, it can be determined that the pattern is basically consistent with the diffraction peaks of the PDF standard card (020-0669). Therefore, before the water bath heating transformation, the main crystallization in the solution is MgCO3·3H2O. Starting from the 5th hour of water bath heating, the X-ray diffraction (XRD) pattern of the transformation in the solution basically matches the diffraction peaks of the PDF standard card (020-0669). However, compared with the patterns from previous time periods, the transformation has already begun, and the solution... The crystals in the solution were still mainly composed of MgCO3·3H2O, with Mg5(CO3)4(OH)2·4H2O beginning to appear. After heating in the water bath for 7 hours, the X-ray diffraction (XRD) pattern of the crystals in the solution basically matched the diffraction peaks of the PDF standard card (025-0513), indicating that the transformation in the solution was basically completed. At this point, the crystals in the solution had basically transformed from MgCO3·3H2O to Mg5(CO3)4(OH)2·4H2O.

[0083] like Figure 12 As shown, the initial morphology of MgCO3·3H2O is as follows: Figure 9 (a,b) Whisker-like structure; after 5 hours of transformation in a 40℃ water bath, some MgCO3·3H2O crystals had begun to transform into plate-like Mg5(CO3)4(OH)2·4H2O, and... Figure 9 The XRD patterns correspond to those in the image; after 7 hours of conversion in a 40℃ water bath, the conversion is essentially complete, as shown in the image. Figure 12 As shown in (e,f), its crystal structure no longer contains prismatic or whisker-like structures, but has been completely transformed into a plate-like structure.

[0084] 5. Firing test

[0085] Samples of the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O obtained at raw material solution concentrations of 0.5M and 2M were selected and calcined in a muffle furnace to convert the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O into MgO, thereby obtaining micron-shaped flower-like porous magnesium oxide and nanosheet-like porous magnesium oxide, respectively.

[0086] Figure 13 As shown Figure 5 The XRD patterns of the calcined products of the two samples (a,b) and (e,f) are basically consistent with the diffraction peaks of the PDF standard card (45-0946), indicating that the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O has been completely converted into MgO.

[0087] Depend on Figure 14 It can be seen that, Figure 5 The MgO produced by calcining samples (a,b) and (e,f) showed slight differences in morphology, which may be due to deformation caused by calcination temperature or heating rate. However, their overall structure remained similar. Therefore, the corresponding MgO can be prepared by controlling the morphological characteristics of the precursor Mg5(CO3)4(OH)2·4H2O.

[0088] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for synthesizing porous magnesium oxide in large quantities under mild conditions, characterized in that, Includes the following steps: S1. Using any one of MgSO4·7H2O, Mg(NO3)2·6H2O or MgCl2·6H2O as the magnesium source, mix with Na2CO3 solution and stir the reaction at room temperature to 50℃ without surfactant to generate magnesium carbonate trihydrate precursor MgCO3·3H2O. S2. Add solid NaOH to the mixture of S1 and carry out hydroxylation conversion reaction in a water bath at 30-50℃ to obtain the basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O. S3, calcined basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O, to obtain the porous magnesium oxide.

2. The method for synthesizing porous magnesium oxide in large quantities under mild conditions according to claim 1, characterized in that, The concentrations of both the magnesium source and Na2CO3 in S1 are 0.5-2 mol / L.

3. The method for synthesizing porous magnesium oxide in large quantities under mild conditions according to claim 2, characterized in that, The volume ratio of magnesium source to Na2CO3 solution in S1 is 1:

1.

4. The method for synthesizing porous magnesium oxide in large quantities under mild conditions according to claim 1, characterized in that, The amount of NaOH solid added in S2 is 0.6-0.8g of NaOH solid per 100mL of Na2CO3 solution.

5. The method for synthesizing porous magnesium oxide in large quantities under mild conditions according to claim 2, characterized in that, When the solution reaction concentration is 0.5 mol / L, a fluffy basic magnesium carbonate precursor is obtained, which is then calcined to obtain micron-sized flower-like porous magnesium oxide.

6. The method for synthesizing porous magnesium oxide in large quantities under mild conditions according to claim 2 or 4, characterized in that, When the solution reaction concentration is 2 mol / L and the amount of NaOH added is 0.8 g / 100 mL, a sheet-like basic magnesium carbonate precursor is obtained, which is then calcined to obtain nanosheet-like porous magnesium oxide.

7. The method for synthesizing porous magnesium oxide in large quantities under mild conditions according to claim 5, characterized in that, The specific surface area of ​​the micron-sized flower-like porous magnesium oxide is ≥130 m². 2 / g, with a pore size distribution of 3-9nm.

8. The method for synthesizing porous magnesium oxide in large quantities under mild conditions according to claim 6, characterized in that, The specific surface area of ​​the nanosheet porous magnesium oxide is 40-50 m². 2 / g.

9. The method for synthesizing porous magnesium oxide in large quantities under mild conditions according to claim 1, characterized in that, The hydroxylation conversion reaction time in S2 is 5-7 hours.

10. The method for synthesizing porous magnesium oxide in large quantities under mild conditions according to claim 1, characterized in that, The basic magnesium carbonate precursor Mg5(CO3)4(OH)2·4H2O in S3 is calcined at 400-600℃.

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