Magnesium formate and preparation method thereof

Abstract

The invention relates to magnesium formate and a preparation method thereof, and the preparation method of the magnesium formate comprises the following steps: by taking bischofite and ammonium formate as raw materials, carrying out liquid phase reaction in a water phase medium to generate a mixture containing the magnesium formate and ammonium chloride; and solid magnesium formate is separated from the mixture. According to the invention, bischofite (MgCl2. 6H2O) is innovatively selected as a magnesium source, and the substance is a cheap by-product in industrial processes of extracting lithium from a salt lake, preparing salt from seawater and the like and is wide in source, so that the cost of raw materials is greatly reduced. Meanwhile, ammonium formate (NH4HCOO) is adopted to replace traditional formic acid or organic amine and is stable in property, safe and easy to decompose, use of strong corrosive acid or toxic solvent is avoided from the source, and the development trend of green chemistry is met.

Description

Technical Field

[0001] This invention relates to the field of inorganic salt synthesis technology, specifically to magnesium formate and its preparation method. Background Technology

[0002] Magnesium formate, as an important magnesium-based functional material, has broad application prospects in cutting-edge fields such as hydrogen storage, gas adsorption, and capacitive deionization due to its unique structural properties. However, existing methods for synthesizing magnesium formate have many shortcomings, which restrict its large-scale production and practical application.

[0003] Currently, the main synthesis methods include: 1. Solvothermal Method: For example, existing technologies (such as the method used by Zhang Qingfu's team) typically involve reacting magnesium chloride with N,N-dimethylformamide in organic solvents such as toluene. This method not only requires harsh reaction conditions (high temperatures) but also uses large quantities of toxic and difficult-to-recover organic solvents (such as toluene and DMF), posing serious environmental and safety concerns. Furthermore, amine byproducts that may be generated during the reaction can easily remain in the final product, resulting in low product purity and affecting its performance in precision applications.

[0004] 2. Solvent-free method: Another existing technology (such as the method used by Mueller U's team) involves the direct reaction of metallic magnesium with formic acid. Although this method avoids organic solvents, the raw material metallic magnesium is expensive, and the reaction process requires precise control of the amount of formic acid to avoid over-acidification. The process has low error tolerance and is difficult to adapt to the needs of large-scale production.

[0005] In summary, existing technologies generally face technical bottlenecks such as high raw material costs, severe environmental pollution, harsh reaction conditions, and insufficient product purity. Summary of the Invention

[0006] Therefore, it is necessary to provide magnesium formate and its preparation method to solve the problems existing in the prior art.

[0007] To achieve the above objectives, the present invention provides a technical solution: A method for preparing magnesium formate, comprising the following steps: Using magnesium chloride and ammonium formate as raw materials, a liquid-phase reaction is carried out in an aqueous medium to produce a mixture containing magnesium formate and ammonium chloride. Solid magnesium formate was separated from the mixture.

[0008] Preferably, the reaction temperature of the liquid phase reaction is 50℃-60℃.

[0009] Preferably, the liquid-phase reaction is carried out at atmospheric pressure.

[0010] Preferably, after separating solid magnesium formate from the mixture, a purification step is further included: The separated solid magnesium formate was recrystallized using an alcohol-water mixed solvent.

[0011] Preferably, the alcohol-water mixed solvent is a mixture of ethanol and water, wherein the volume ratio of ethanol to water is 1:(1-3).

[0012] Preferably, the recrystallization process includes the following steps: The solid magnesium formate is mixed with the alcohol-water mixed solvent and heated to 80°C-100°C to dissolve the byproduct ammonium chloride. Then, it is hot filtered to collect the insoluble solid magnesium formate.

[0013] Preferably, after the purification step, a drying step is also included: The separated or purified solid magnesium formate was vacuum dried at a temperature of 150℃-200℃ to obtain anhydrous magnesium formate.

[0014] Preferably, the drying time is 60 min to 180 min.

[0015] The present invention also provides a method for preparing magnesium formate as described above.

[0016] Preferably, the purity of the magnesium formate is ≥99%.

[0017] The beneficial effects of this invention are: 1. Low-cost and environmentally friendly raw materials: This invention innovatively selects magnesium chloride hydrate (MgCl2·6H2O) as the magnesium source. This substance is an inexpensive byproduct of industrial processes such as lithium extraction from salt lakes and seawater salt production, and its wide availability greatly reduces raw material costs. Simultaneously, ammonium formate (NH4HCOO) is used instead of traditional formic acid or organic amines. Its stable, safe, and easily decomposed properties prevent the use of highly corrosive acids or toxic solvents from the outset, aligning with the trend of green chemistry.

[0018] 2. Mild reaction conditions and simple and easy process: The core reaction of this invention is completed in an aqueous system. The reaction conditions are mild and can usually be carried out at atmospheric pressure and 60-80℃. No high pressure or special equipment is required, which reduces equipment investment and operating energy consumption. The process has a high fault tolerance rate and is easier to achieve large-scale production.

[0019] 3. High Product Purity: This invention utilizes a metathesis reaction pathway, with ammonium chloride (NH4Cl) as a byproduct of the main reaction. Taking advantage of the significant difference in solubility between magnesium formate and ammonium chloride in specific solvents (such as an ethanol-water mixture), purification steps including gradient crystallization and hot filtration can efficiently and thoroughly remove ammonium chloride and other impurities. Examples show that the purified product purity can reach over 99.3%, meeting the requirements of high-end applications.

[0020] 4. Resource recycling and environmental friendliness: Ammonium chloride, a byproduct separated during the purification process, is a high-quality nitrogen fertilizer raw material that can be recycled and reused, realizing the recycling of resources and basically achieving the reduction of "three wastes" in the production process, resulting in significant environmental benefits. Attached Figure Description

[0021] Figure 1 The apparatus for preparing magnesium formate includes (a) a reaction apparatus and (b) a filtration apparatus. Figure 2 A schematic diagram of the apparatus for the continuous preparation of magnesium formate; Figure 3 This is a diagram of a continuous flow reactor, where... Figure 3 (a) ACR-100 device diagram. Figure 3 (b) ACR-100 reaction plate; Figure 4 The XRD patterns of magnesium formate dihydrate obtained before and after drying are shown. Figure 5 Infrared spectra of magnesium formate dihydrate and magnesium formate anhydrous; Figure 6 The images are SEM images, where ac is the SEM image of magnesium formate dihydrate obtained in Example 2 at different magnifications, and (de is the SEM image of commercially available magnesium formate dihydrate at different magnifications). Figure 7 Figures showing the yields of magnesium formate at different reaction temperatures; Figure 8 Figure showing the yield of magnesium formate at different reaction liquid flow rates; Figure 9 The graph shows the yield of magnesium formate under different raw material concentrations. Detailed Implementation

[0022] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0023] In the embodiments, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0024] A method for preparing magnesium formate, comprising the following steps: like Figure 1 As shown, magnesium chloride and ammonium formate are used as raw materials to carry out a liquid-phase reaction in an aqueous medium, and the reaction produces a mixture containing magnesium formate and ammonium chloride. Solid magnesium formate was separated from the mixture.

[0025] in, Figure 1(a) The reaction apparatus for the preparation of magnesium formate; Figure 1 (b) A filtration device prepared for magnesium formate; This invention proposes an innovative process for the direct synthesis of magnesium formate via an aqueous phase reaction using magnesium chloride hydrate (MgCl2·6H2O) and ammonium formate (NH4HCOO) as raw materials. Specific improvements are as follows: 1. Raw material optimization: Magnesium chloride is a cheap byproduct of industries such as lithium extraction from salt lakes and seawater salt production (e.g., resources from Qinghai Salt Lake), and it is widely available and inexpensive. Ammonium formate, as a safe and easily decomposed weak acidic ammonium salt, can avoid the use of traditional formic acid or organic amines, reducing side reactions and environmental pollution.

[0026] 2. Reaction Pathway Innovation: In the aqueous reaction system, magnesium chloride hydrate and ammonium formate undergo a metathesis reaction: MgCl2·6H2O + 2NH4HCOO → Mg(HCOO)2+2NH4Cl+6H2OMgCl2 ·6H2O+2NH4HCOO→ Mg(HCOO)₂ + 2NH₄Cl + 6H₂O; The reaction conditions are mild (atmospheric pressure, reaction at 50-60℃, purification at 80-100℃), no high-pressure equipment is required, and the byproduct ammonium chloride (NH4Cl) can be efficiently removed by washing with water, significantly improving the purity of the product.

[0027] In some of these embodiments, the reaction temperature of the liquid phase reaction is 50°C-60°C.

[0028] In some of these embodiments, the liquid-phase reaction is carried out at atmospheric pressure.

[0029] In some embodiments, after separating solid magnesium formate from the mixture, a purification step is further included: The separated solid magnesium formate was recrystallized using an alcohol-water mixed solvent.

[0030] In some embodiments, the alcohol-water mixed solvent is a mixture of ethanol and water, wherein the volume ratio of ethanol to water is 1:(1-3).

[0031] In some embodiments, the recrystallization process includes the steps of: The solid magnesium formate is mixed with the alcohol-water mixed solvent and heated to 80°C-100°C to dissolve the byproduct ammonium chloride. Then, it is hot filtered to collect the insoluble solid magnesium formate.

[0032] The redissolution step of the crude product after the first filtration is crucial. Dissolving residual ammonium chloride in deionized water, combined with a second filtration, efficiently removes impurities. The optimized purification scheme requires only a single redissolution-filtration operation to increase the purity of magnesium formate to over 99%, while simultaneously maintaining a stable yield of over 95%, balancing efficiency and product quality and avoiding yield losses caused by multiple purification steps. In some embodiments, a drying step is also included after the purification step. The separated or purified solid magnesium formate was vacuum dried at a temperature of 150℃-200℃ to obtain anhydrous magnesium formate.

[0033] In some of these embodiments, the drying time is 60 min to 180 min.

[0034] Magnesium formate and ammonium chloride were separated by recrystallization, and low-temperature drying technology was used to avoid dehydration of magnesium formate, resulting in a high-purity (>99%) anhydrous magnesium formate product. The ammonium chloride produced during the purification process of this invention can be recycled as a nitrogen fertilizer raw material, realizing resource recycling.

[0035] The present invention also provides a method for preparing magnesium formate as described above.

[0036] In some of these embodiments, the magnesium formate has a purity of ≥99%.

[0037] Example 1: Synthesis of magnesium formate. A schematic diagram of the continuous flow magnesium formate preparation route is shown below. Figure 2 As shown.

[0038] Step 1: Raw material preparation: Weigh 100 g (0.5 mol) of magnesium chloride hydrate (MgCl2 ·6H2O) and 77.5 g (1.0 mol) of ammonium formate into a reaction vessel, add 500 mL of methanol solvent, and stir until completely dissolved to form a homogeneous mixture.

[0039] Step 2: Continuous flow reaction The mixture is pumped into the ACR-100 continuous flow reactor, such as... Figure 3 As shown, the reaction temperature was set to 55℃, and the reaction liquid flow rate was set to 0.5 mL·min. -1 -1.0 mL·min -1 The raw material concentration C was set to 0.05 mol·L⁻¹. -1 -0.20 mol·L -1 Stir and react for 2 hours.

[0040] Step 3: Initial separation After the reaction was completed, the precipitate was separated by vacuum filtration. The filter cake was washed three times with hot ethanol, and the solid was collected to obtain crude magnesium formate dihydrate (Mg(HCOO)2·2H2O).

[0041] Example 2: Purification of magnesium formate: Step 1: Redissolution of the crude product The crude magnesium formate dihydrate obtained in Example 1 (100 g, 1e) was added to a 1:2 ethanol-water mixed solvent (1.2e) and heated to 100°C to completely dissolve the byproduct ammonium chloride while keeping the magnesium formate insoluble.

[0042] Step 2: Secondary filtration and drying: The suspension was filtered while hot, and the filter cake was leached with a 1:2 ethanol-water mixed solvent. The solid magnesium formate dihydrate was collected and transferred to a vacuum drying oven to dry and dehydrate at 180°C for 2 hours to obtain anhydrous magnesium formate with a mass of 94.8 g and a purity of 99.3% (the magnesium content determined by ICP-OMS was 99.1% of the theoretical value), and a yield of 95.5%.

[0043] The purified product, anhydrous magnesium formate, was characterized, and the characterization results are as follows: Figure 4-8 As shown, by Figure 6 The SEM images show that the anhydrous magnesium formate particles are in the form of regular flakes with an average particle size D50 = 50 μm.

[0044] The present invention also optimized the key factors of magnesium formate synthesis in Example 1. Other steps are the same as in Example 1, and the differences are shown in Table 1. Reactions 1, 2, 3, 4 and 5 are crude magnesium formate dihydrate that has not been purified by the steps in Example 2, and reactions 6*, 7*, 8*, 9* and 10* are anhydrous magnesium formate purified by the steps in Example 2.

[0045] Table 1. Optimization of reaction parameters and corresponding sample data.

[0046] Note: Data marked with * indicates the purity and yield of the purified sample; the equivalence ratio is the equivalence ratio of magnesium chloride water to ammonium formate.

[0047] 1) Optimization of reaction temperature: As shown in Table 2, comparing the data of reactions 1, 2, 3, 4, and 5, it can be seen that when the temperature is below 50℃ (reactions 1 and 2), the reaction yield is low and the product purity is insufficient. Comparing the data for reactions 6*, 7*, 8*, 9*, and 10*, it can be seen that the optimal temperature is 50-55℃.

[0048] Therefore, 50~60℃ is the ideal reaction range, and at 55℃, the yield and purity of magnesium formate both reach over 95%. Further increases in temperature will lead to a surge in costs and a decrease in purity, so 55℃ was selected as the optimal temperature.

[0049] 2) Optimization of reaction time: Comparing reactions 1 and 2 in Table 1, it can be seen that the yield and purity of reaction 1, which has a reaction time of 1 hour, are lower than those of reaction 2, which has a reaction time of 2 hours. This is because when the reaction time is less than 2 hours, the reaction is not completed and the yield is insufficient. Exceeding 2 hours results in wasted resources and an increased risk of side reactions.

[0050] 3) Control of reactant ratio The molar ratio of magnesium chloride to ammonium formate is crucial to the sufficiency of the reaction and the quality of the product. The initial ratio resulted in limited reaction efficiency; after experimental optimization, a molar ratio of 1:2 was determined to be the optimal one.

[0051] 3. Key factors affecting the purification of magnesium formate 1) Screening of the purification and washing solvent system. The results are shown in Table 2. Parameters and steps not mentioned in the table are the same as in Examples 1 and 2. The differences are shown in Table 2.

[0052] Table 2 Selection of washing solvent and sample data

[0053] Note: Data marked with * indicates the purity and yield of the purified sample.

[0054] As shown in Table 2, compared with reaction 1* and reaction 2*, and reaction 3* and reaction 4*, the purity of reaction 1* and reaction 3* separated by ethanol filtration is lower. This is because magnesium formate and ammonium chloride have low solubility in ethanol, resulting in residual impurities in the crude product.

[0055] A mixed solvent of deionized water, ethanol, and water was introduced for redissolution followed by secondary filtration. By selectively dissolving ammonium chloride, the purity of magnesium formate was significantly improved. This strategy effectively solved the purity bottleneck of single-pass ethanol filtration, and the results are shown in Table 3.

[0056] Table 3. Optimization of purification process and corresponding sample data

[0057] 4. Key factors affecting the continuous flow preparation of magnesium formate 1) Precise control of reaction temperature Reaction temperature is a core parameter in continuous flow processes, directly affecting product purity and yield. The results are shown in Table 4 and... Figure 7 As shown.

[0058] From Table 4 and Figure 7 It is known that excessively high temperatures (≥60℃) can trigger side reactions (such as the decomposition of ammonium formate or the dehydration of magnesium formate), leading to the formation of impurities; while excessively low temperatures (≤40℃) limit reaction kinetics and result in incomplete conversion of raw materials. Experiments show that 50~55℃ is the optimal range, at which the yield of magnesium formate is ≥95%.

[0059] In addition, temperature uniformity must be maintained in continuous flow reactors to avoid the risk of reactor blockage caused by local overheating or low temperature.

[0060] Table 4. Data on reaction temperature control

[0061] 2) Optimization of reaction liquid flow rate The flow rate of the reaction liquid determines the residence time and mixing efficiency of the material in the reactor, as shown in Table 5. Figure 8 As shown.

[0062] From Table 5 and Figure 8 It is known that excessively high flow rates (e.g., >10 mL / min) will lead to insufficient reaction time, incomplete crystallization of the product, and a decrease in yield; while excessively low flow rates may cause reactor blockage due to material retention, affecting the stability of continuous operation. Experimental verification shows that controlling the flow rate at 0.5~0.7 mL / min can achieve a balance between reaction sufficiency and equipment stability, while avoiding solid deposition.

[0063] Table 5. Data on the control of reaction liquid flow rate

[0064] 3) Design for adaptability of raw material concentration The feedstock concentrations (initial concentrations of magnesium chloride and ammonium formate) need to be matched with the mass transfer efficiency of the continuous flow process, as shown in Table 6. Figure 9 As shown in the figure.

[0065] From Table 6 and Figure 9 It is evident that when the concentration is too high (e.g., >0.15 mol / L), the viscosity of the reaction solution increases, leading to uneven mixing, excessively rapid local crystallization, and an increased risk of reactor blockage. Conversely, when the concentration is too low (<0.8 mol / L), production efficiency decreases, and the product particles become too fine, hindering subsequent filtration and separation. The optimized concentration was set at 0.1~0.12 mol / L to ensure both reaction efficiency and product operability.

[0066] Table 6. Data on the control of raw material concentration

[0067] It should be noted that the specific parameters or reagents in the above embodiments are specific or preferred embodiments under the concept of the present invention, and not limitations thereof; those skilled in the art can make adaptive adjustments within the concept and protection scope of the present invention.

Claims

1. A method for preparing magnesium formate, characterized in that, Including the following steps: Using magnesium chloride and ammonium formate as raw materials, a liquid-phase reaction is carried out in an aqueous medium to produce a mixture containing magnesium formate and ammonium chloride. Solid magnesium formate was separated from the mixture.

2. The method for preparing magnesium formate according to claim 1, characterized in that, The reaction temperature for the liquid phase reaction is 50℃-60℃.

3. The method for preparing magnesium formate according to claim 1, characterized in that, The liquid-phase reaction is carried out at atmospheric pressure.

4. The method for preparing magnesium formate according to claim 1, characterized in that, After separating solid magnesium formate from the mixture, a purification step is also included: The separated solid magnesium formate was recrystallized using an alcohol-water mixed solvent.

5. The method for preparing magnesium formate according to claim 4, characterized in that, The alcohol-water mixed solvent is a mixture of ethanol and water, and the volume ratio of ethanol to water is 1:(1-3).

6. The method for preparing magnesium formate according to claim 4, characterized in that, The recrystallization process includes the following steps: The solid magnesium formate is mixed with the alcohol-water mixed solvent and heated to 80°C-100°C to dissolve the byproduct ammonium chloride. Then, it is hot filtered to collect the insoluble solid magnesium formate.

7. The method for preparing magnesium formate according to claim 4, characterized in that, After the purification step, a drying step is also included: The separated or purified solid magnesium formate was vacuum dried at a temperature of 150℃-200℃ to obtain anhydrous magnesium formate.

8. The method for preparing magnesium formate according to claim 7, characterized in that, The drying time is 60-180 minutes.

9. A magnesium formate, characterized in that, Prepared by the method according to any one of claims 1 to 8.

10. The magnesium formate according to claim 9, characterized in that, The purity of the magnesium formate is ≥99%.

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