Methylene methanedisulfonate and preparation method thereof

Abstract

The invention discloses methylene methanedisulfonate and a preparation method thereof. The preparation method of methylene methanedisulfonate comprises the following steps: dissolving sulfur trioxide in halogenated alkane to form a complexing system, and adding methylene disulfonic acid and paraformaldehyde to obtain a mixed solution; and heating the mixed solution for reaction, and separating to obtain methylene methanedisulfonate. Methylene methanedisulfonate is synthesized by taking methylene disulfonic acid and paraformaldehyde as reactants and taking halogenated alkane as a solvent, the reaction system is a homogeneous reaction, low yield caused by non-uniform mixing is avoided, meanwhile, sulfur trioxide is complexed with halogenated alkane after being dissolved in halogenated alkane, the activity of sulfur trioxide participating in side reaction is reduced, and the yield of methylene methanedisulfonate is increased. The side reaction can be inhibited, and the reaction selectivity is improved.

Description

Technical Field

[0001] The present application belongs to the field of chemical synthesis, and specifically relates to methylene methanedisulfonate and a preparation method thereof. Background Art

[0002] Methylene disulfonate (MMDS) is a new type of electrolyte additive for lithium-ion batteries. Adding methylene disulfonate to the production of lithium battery electrolyte can greatly improve the high-temperature cycle performance of lithium batteries and significantly extend the service life of lithium batteries. Especially in power batteries with lithium manganese oxide as the positive electrode material, the addition of methylene disulfonate can effectively prevent the manganese dissolved at high temperature from being adsorbed on the negative electrode surface, inhibit its impedance increase, effectively improve its cycle characteristics, and thus greatly increase its cycle life. With the increase in the market share of lithium manganese oxide batteries, the market size of MMDS will also gradually expand.

[0003] The currently reported MMDS synthesis method basically uses methylene disulfonic acid and polyoxymethylene as starting materials, and phosphorus pentoxide as a dehydrating agent for condensation. This method is a solvent-free solid phase reaction, the reaction is difficult to control, the reactants are difficult to mix evenly, the local reaction causes the reaction heat to be difficult to transfer in time, resulting in side reactions, and the use of a solid dehydrating agent causes the reaction post-processing to be more troublesome, affecting the yield of the product. In addition, the use of phosphorus pentoxide as a dehydrating agent has high raw material costs, and phosphorus pentoxide is easy to absorb moisture, which is inconvenient to feed; the generated product is dark in color and has high acidity. In summary, the existing preparation method of MMDS has many side reactions and a low yield of methylene disulfonate, resulting in a high impurity content in MMDS. Summary of the invention

[0004] The present application aims to solve one of the related technical problems to a certain extent. In view of this, the first object of the present application is to provide a method for preparing methylene methane disulfonate, which has a high yield of methylene methane disulfonate and few side reactions.

[0005] In the first aspect of the present application, a method for preparing methylene methane disulfonate is proposed, comprising: dissolving sulfur trioxide in a halogenated alkane to form a complex system, adding methylene disulfonic acid and polyformaldehyde to obtain a mixed solution; and heating the mixed solution for reaction to prepare methylene methane disulfonate.

[0006] The preparation method of methylene disulfonate of the present application has the following beneficial effects: with methylene disulfonic acid and polyformaldehyde as reactants, halogenated alkane can not only be used as a solvent to make the reaction system a homogeneous reaction, avoiding low yield caused by uneven mixing, but more importantly, after the dehydrating agent sulfur trioxide is dissolved in the halogenated alkane, it is complexed with the halogenated alkane to form a complex system, which can reduce the activity of sulfur trioxide in side reactions, thereby inhibiting the occurrence of side reactions and improving the selectivity of the reaction. In addition, after sulfur trioxide is complexed with the halogenated alkane, when the temperature is raised for the reaction, the dehydrating agent sulfur trioxide will not volatilize, smoke, and generate pressure, which is convenient for equipment selection.

[0007] In addition, the methylene disulfonate prepared by the preparation method of the present application has a high yield due to the small side reaction of the dehydrating agent sulfur trioxide, and the product has high purity and low chlorine content. When used as an electrolyte additive, it can effectively reduce the increase in chlorine content in the electrolyte caused by the introduction of the additive, thereby reducing the risk of increased chlorine content in the electrolyte leading to corrosion of the positive electrode sheet and dissolution of transition metal ions in the positive electrode sheet. Therefore, the problem of reduced improvement effect of methylene disulfonate on the electrochemical performance of the battery due to the presence of chlorine can be effectively improved, thereby improving the improvement effect of methylene disulfonate on the electrochemical performance of the battery.

[0008] In some embodiments, the halogenated alkane includes at least one of ethylene dichloride and tetrachloroethane.

[0009] In some embodiments, the mass ratio of the sulfur trioxide to the halogenated alkane is 1:(2-20).

[0010] In some embodiments, the molar ratio of the methylene disulfonic acid, the paraformaldehyde and the sulfur trioxide is 1:(1.1-1.5):(1.1-2).

[0011] In some embodiments, the methylene disulfonic acid is prepared by reacting methylene disulfonic acid with sulfur trioxide or chlorosulfonic acid.

[0012] In some embodiments, the mixed solution is heated to 50° C.-130° C. to perform the reaction.

[0013] In some embodiments, the reaction time is 2h-10h.

[0014] In some embodiments, the step of separating is further included after the heating reaction:

[0015] The mixed solution after the reaction was concentrated to a saturated state, and the temperature was lowered to 5°C-10°C for crystallization to obtain a crude product;

[0016] The crude product was added into dichloroethane for washing, filtered and dried to obtain methylene methanedisulfonate.

[0017] In the second aspect of the present application, a methylene disulfonate is provided. The methylene disulfonate is prepared by the method described in the first aspect of the present application.

[0018] The methylene disulfonate proposed in the present application has the following beneficial effects: the methylene disulfonate proposed in the present application has high purity and low chlorine content. When used as an electrolyte additive, it can effectively reduce the increase in free chlorine content in the electrolyte caused by the introduction of the additive, thereby reducing the risk of positive electrode plate corrosion and transition metal ion dissolution in the positive electrode plate caused by the increase in free chlorine content in the electrolyte. Therefore, the problem of reduced improvement effect of methylene disulfonate on battery electrochemical performance caused by the presence of free chlorine can be effectively improved, thereby improving the improvement effect of methylene disulfonate on battery electrochemical performance.

[0019] In some embodiments, the purity of the methylene methanedisulfonate is ≥ 99.7%.

[0020] In some embodiments, based on the total mass of the methylene methanedisulfonate, the mass proportion of chlorine element is ≤1 ppm.

[0021] In some embodiments, based on the total mass of the methylene methanedisulfonate, the mass proportion of free acid is ≤100 ppm.

[0022] In some embodiments, based on the total mass of the methylene methanedisulfonate, the mass proportion of water is ≤100 ppm.

[0023] In some embodiments, based on the total mass of the methylene methanedisulfonate, the mass proportion of any one metal element is ≤1 ppm, and the metal element includes Cu, Fe, Zn, Cr, Na, K, Pb, Co, Ni, Ca, Al and Ag.

[0024] In some embodiments, the methylene methanedisulfonate has a color of ≤50 Hazen.

[0025] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0027] Figure 1 This is the H NMR spectrum of methylene disulfonate prepared according to Example 1 of the present application.

[0028] Figure 2This is the NMR carbon spectrum of methylene disulfonate prepared according to Example 1 of the present application. DETAILED DESCRIPTION

[0029] The embodiments of the present application are described in detail below, which are intended to be used to explain the present application but should not be construed as limiting the present application.

[0030] The existing preparation method of MMDS has many side reactions and low yield of methylene disulfonate, resulting in high impurity content in MMDS. Related technologies also report the use of liquid sulfur trioxide as a dehydrating agent to generate MMDS. This process does not use phosphorus pentoxide as a dehydrating agent, has good fluidity and low cost; however, since sulfur trioxide will volatilize at high temperatures, the reaction pressure is high and the equipment requirements are high. In addition, sulfur trioxide is directly in contact with the reaction raw materials and carbonization occurs. Due to its high reaction activity, it is easy to generate methanetrisulfonic acid and other side reactions, resulting in high impurity content in methylene disulfonate, which affects its application and is difficult to achieve industrial production.

[0031] Based on this, in the first aspect of the present application, a method for preparing methylene methane disulfonate is proposed, the method comprising:

[0032] S1: dissolving sulfur trioxide in halogenated alkane to form a complex system, adding methylene disulfonic acid and paraformaldehyde to obtain a mixed solution;

[0033] In this step, reactants methylene disulfonic acid and paraformaldehyde, dehydrating agent sulfur trioxide and solvent halogenated alkane are mixed to form a homogeneous mixed solution, which creates a homogeneous environment for subsequent reactions, and the reaction conditions are mild, the feeding is convenient, the yield is high, and the dehydrating agent sulfur trioxide is cheap and low in cost, and industrial production can be achieved. More importantly, halogenated alkane can be complexed with dehydrating agent sulfur trioxide, so that the reaction activity of dehydrating agent sulfur trioxide is reduced, thereby improving reaction selectivity and yield. And after complexation, when the temperature is raised, the dehydrating agent sulfur trioxide will not volatilize and smoke and generate pressure, which is convenient for equipment selection.

[0034] In addition, the reactants of the present application do not contain chlorine, and the halogenated alkane used as a solvent has good stability and does not participate in the reaction. Therefore, the subsequently prepared methanedisulfonic acid methylene ester has high purity, low impurity content, and basically does not contain chlorine. When used as an electrolyte additive, it can effectively reduce the increase in the free chlorine content in the electrolyte caused by the introduction of the additive, thereby reducing the risk of corrosion of the positive electrode sheet and dissolution of transition metal ions in the positive electrode sheet caused by the increase in the free chlorine content of the electrolyte. Therefore, the problem of reduced improvement effect of methanedisulfonic acid methylene ester on the electrochemical performance of the battery due to the presence of free chlorine can be effectively improved, thereby improving the improvement effect of methanedisulfonic acid methylene ester on the electrochemical performance of the battery.

[0035] In some specific embodiments of the present application, the halogenated alkane includes at least one of dichloroethane and tetrachloroethane. Using at least one of the above halogenated alkanes as a solvent has good solubility for the dehydrating agent sulfur trioxide, does not participate in the reaction, has good stability, and provides a homogeneous and mild environment. More importantly, the above halogenated alkane has a good complexing effect with the dehydrating agent sulfur trioxide, which reduces the reactivity of the dehydrating agent sulfur trioxide, improves the reaction selectivity, and thus improves the yield. After complexing, when the temperature is raised for reaction, the dehydrating agent sulfur trioxide will not volatilize, smoke, and generate pressure, which is convenient for equipment selection.

[0036] In some specific embodiments of the present application, the mass ratio of the sulfur trioxide to the halogenated alkane is 1:(2-20). For example, the mass ratio of sulfur trioxide to halogenated alkane can be 1:2, 1:4, 1:5, 1:7, 1:10, 1:15, 1:20, etc. By controlling the mass ratio of the dehydrating agent sulfur trioxide to the halogenated alkane within the above range, the two can be fully complexed, and the dehydrating effect of the dehydrating agent sulfur trioxide can be fully exerted, which is conducive to the forward reaction of methylene disulfonic acid and polyformaldehyde to generate methylene disulfonate, and can reduce the incomplete complexation with the solvent caused by excessive sulfur trioxide of the dehydrating agent, and participate in side reactions in the subsequent reaction process, thereby ensuring the purity of the obtained methylene disulfonate; it can also reduce the incomplete water absorption caused by too little sulfur trioxide of the dehydrating agent, so that methylene disulfonic acid and polyformaldehyde react fully, and improve the yield of methylene disulfonate.

[0037] In some specific embodiments of the present application, the molar ratio of the methylene disulfonic acid, the polyformaldehyde and the sulfur trioxide is 1:(1.1-1.5):(1.1-2). For example, the molar ratio of the three can be 1:1.3:1.1, 1:1.3:1.5, 1:1.3:2, 1:1.1:1.5, 1:1.5:1.5, etc. By controlling the molar ratio of the methylene disulfonic acid, the polyformaldehyde and the sulfur trioxide within the above range, methylene disulfonic acid and polyformaldehyde can be fully reacted to generate methylene methane disulfonate with less side reactions, thereby improving the yield and purity of methylene methane disulfonate.

[0038] It can be understood that in the embodiments of the present invention, the amount of the substance of paraformaldehyde refers to the amount of the substance of -CH2O- groups in the paraformaldehyde.

[0039] In some specific embodiments of the present application, the methylene disulfonic acid is prepared by the following method: sulfur trioxide is dissolved in a halogenated alkane and methane sulfonic acid is added for reaction to obtain methylene disulfonic acid. Thus, the yield of methylene disulfonic acid is high, the process is simple and the reaction conditions are mild. Moreover, it can be directly used as a reactant to prepare methylene methane disulfonate without separation.

[0040] S2: heating the mixed solution to react and prepare methylene methane disulfonate.

[0041] In this step, methylene disulfonic acid and paraformaldehyde are reacted by heating to obtain methylene disulfonate. Methylene disulfonic acid and paraformaldehyde react to generate water and methylene disulfonate. The dehydrating agent sulfur trioxide reacts with water to consume the water, thereby promoting further reaction of methylene disulfonic acid and paraformaldehyde. The reaction process is as follows:

[0042]

[0043] In some specific embodiments of the present application, the mixed solution is heated to 50°C-130°C for reaction, for example, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, etc. Controlling the reaction temperature within the above range can promote the full reaction of methylene disulfonic acid and polyformaldehyde, and prevent the temperature from being too high to cause the volatilization and decomposition of the components in the mixed solution, thereby reducing the occurrence of side reactions, thereby further improving the yield and purity of methylene disulfonate.

[0044] In some specific embodiments of the present application, the reaction time is 2h-10h. For example, the heating reaction time can be 2h, 4h, 5h, 7h, 9h, 10h, etc. Specifically, controlling the reaction time within the above range can promote the full reaction of methylene disulfonic acid and polyformaldehyde, reduce the incomplete reaction caused by too short reaction time, improve the yield of methylene disulfonate, and reduce the occurrence of side reactions caused by too long reaction time, while improving the purity of methylene disulfonate.

[0045] In some specific embodiments of the present application, the heating reaction further includes a separation step:

[0046] S21: concentrating the mixed solution after the reaction to a saturated state, cooling to 5°C-10°C for crystallization to obtain a crude product;

[0047] S22: The crude product is added into dichloroethane for washing, filtering and drying to obtain methylene methanedisulfonate.

[0048] Thus, the separation method is simple to operate, has little loss of methylene methanedisulfonate, and has high yield and purity.

[0049] In summary, the preparation method of methylene disulfonate proposed in the present application is that methylene disulfonic acid and polyformaldehyde are reactants, and halogenated alkanes are used as solvents to synthesize methylene disulfonate. The reaction system is a homogeneous reaction, which avoids the low yield caused by uneven mixing. At the same time, after the dehydrating agent sulfur trioxide is dissolved in the halogenated alkanes, it is complexed with the halogenated alkanes to form a complex system, which reduces the activity of the dehydrating agent sulfur trioxide, can inhibit the occurrence of side reactions, improve the selectivity of the reaction, and the post-treatment is simple, which is convenient for large-scale mass production.

[0050] In the second aspect of the present application, a methylene disulfonate is provided. The methylene disulfonate is prepared by the method described in the first aspect of the present application.

[0051] Therefore, the methylene disulfonate proposed in the present application has high purity, low impurity content, and basically does not contain chlorine. When used as an electrolyte additive, it can effectively reduce the increase in the free chlorine content in the electrolyte caused by the introduction of the additive, thereby reducing the risk of corrosion of the positive electrode sheet and dissolution of transition metal ions in the positive electrode sheet caused by the increase in the free chlorine content of the electrolyte. Therefore, the problem of reduced improvement effect of methylene disulfonate on the electrochemical performance of the battery due to the presence of free chlorine can be effectively improved, thereby improving the improvement effect of methylene disulfonate on the electrochemical performance of the battery.

[0052] In some specific embodiments of the present application, the purity of the methylene methanedisulfonate is ≥99.7%. For example, the purity of the methylene methanedisulfonate can be 99.7%, 99.8%, 99.9%, 99.99%, etc. The present application has high purity and low impurity content. When used as an electrolyte additive, it can avoid introducing impurities into the electrolyte and affecting the stability of the electrolyte. It can also perform oxidation and reduction reactions preferentially over the electrolyte to form a stable interface film on the surface of the positive and negative electrodes, which helps prevent decomposition of the electrolyte and protect the electrode materials, thereby improving the cycle stability of the battery.

[0053] It can be understood that the purity of methylene methanedisulfonate refers to the mass proportion of pure methylene methanedisulfonate in the prepared and purified methylene methanedisulfonate.

[0054] In some specific embodiments of the present application, based on the total mass of the methylene methanedisulfonate, the mass proportion of chlorine is ≤1ppm, for example, it can be 1ppm, 0.8ppm, 0.6ppm, 0.5ppm, 0.3ppm, 0.1ppm, 0, etc., and the content of chlorine in methylene methanedisulfonate is limited to the above range, which can effectively reduce the increase in free chlorine content in the electrolyte caused by the introduction of additives, thereby reducing the risk of corrosion of the positive electrode sheet and dissolution of transition metal ions in the positive electrode sheet caused by the increase in the free chlorine content of the electrolyte, thereby effectively improving the problem of decreased improvement effect of methylene methanedisulfonate on the electrochemical performance of the battery due to the presence of free chlorine, thereby improving the improvement effect of methylene methanedisulfonate on the electrochemical performance of the battery.

[0055] In some specific embodiments of the present application, based on the total mass of the methylene disulfonate, the mass proportion of free acid is ≤100ppm, for example, it can be 100ppm, 80ppm, 60ppm, 50ppm, 30ppm, 10ppm, etc. It can be understood that free acid refers to an acidic substance that exists in a free state in the solution and can release H + In the embodiment of the present application, the free acid is mainly HF. The mass proportion of free acid in methylene disulfonate is limited to the above range, and the purity is high. When used as an electrolyte additive, the acid content of methylene disulfonate introduced into the electrolyte can be reduced, thereby reducing the gas production of the battery.

[0056] In some specific embodiments of the present application, based on the total mass of the methylene methanedisulfonate, the mass proportion of water is ≤100ppm, for example, it can be 100ppm, 80ppm, 60ppm, 50ppm, 30ppm, 10ppm, etc. The mass proportion of water in the methylene methanedisulfonate is limited to the above range, the purity is high, and when used as an electrolyte additive, the water content of the methylene methanedisulfonate introduced into the electrolyte can be reduced, the generation of HF in the battery can be reduced, and the gas production of the battery can be reduced.

[0057] In some specific embodiments of the present application, based on the total mass of the methylene methanedisulfonate, the mass proportion of any one metal element is ≤1ppm, and the metal elements include Cu, Fe, Zn, Cr, Na, K, Pb, Co, Ni, Ca, Al and Ag, for example, 1ppm, 0.8ppm, 0.6ppm, 0.5ppm, 0.3ppm, 0.1ppm, etc. The content of the above metal elements in the methylene methanedisulfonate is controlled, so that the purity of the methylene methanedisulfonate is further improved, which is further conducive to reducing the amount of impurities introduced into the electrolyte as an electrolyte additive, thereby improving the improvement effect of the methylene methanedisulfonate on the electrochemical performance of the battery.

[0058] In some specific embodiments of the present application, the chromaticity of the methylene methane disulfonate is ≤50 Hazen, for example, 50 Hazen, 40 Hazen, 30 Hazen, 20 Hazen, 10 Hazen, 5 Hazen, 1 Hazen, etc., thus, the methylene methane disulfonate has high purity and low impurity content.

[0059] The embodiments of the present application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. In addition, unless otherwise explicitly stated, all reagents used in the following embodiments are commercially available or can be synthesized according to this article or known methods, and the reaction conditions not listed are also easily available to those skilled in the art.

[0060] Example 1

[0061] At room temperature, 144.12 g (1.46 mol) of ethylene dichloride was added to a dry reactor, and 48.04 g (0.6 mol) of sulfur trioxide was slowly added dropwise to form a complex system. After stirring for 1 h, 88.08 g (0.5 mol) of methylene disulfonic acid and 18.02 g (0.6 mol) of paraformaldehyde were added. The temperature was raised to 70°C and refluxed for 5 h. At this time, no pressure was displayed on the pressure gauge. After the reaction was completed, the mixture was allowed to stand and stratified, concentrated to saturation, cooled to 10°C for crystallization, and a crude MMDS product was obtained. The crude product was added with ethylene dichloride and pulped and washed at room temperature (solid content 30%), filtered and dried to obtain 84.89 g of the product with a yield of 90.23%.

[0062] The methylene disulfonate obtained in Example 1 was tested by a nuclear magnetic resonance (NMR) spectrometer to obtain Figure 1 and Figure 2 , it can be seen that the product is methylene methanedisulfonate.

[0063] The differences between Examples 2 to 20 and Example 1 are shown in Table 1.

[0064] Table 1

[0065]

[0066]

[0067] Comparative Example 1

[0068] At room temperature, 88.08 g (0.5 mol) of methylene disulfonic acid was added to a dry reactor, 48.04 g (0.6 mol) of sulfur trioxide was slowly added dropwise, and then 18.02 g (0.6 mol) of paraformaldehyde was added. After the addition was completed, the temperature was raised to 70°C and the reaction was carried out for 5 hours. After the reaction was completed, the mixture was allowed to stand for stratification, concentrated to saturation, and cooled to 10°C for crystallization to obtain a crude MMDS product; the crude product was added with dichloroethane for pulping and washing at room temperature (solid content 30%), filtered and dried to obtain 8.1 g of the product with a yield of 8.61%, a free acid content of 42 ppm, and a moisture content of 500 ppm.

[0069] Comparative Example 2

[0070] At room temperature, 46 mol of ethyl acetate was added to a dry reactor, and 48.04 g (0.6 mol) of sulfur trioxide was slowly added dropwise. After stirring for 1 h, 88.08 g (0.5 mol) of methylene disulfonic acid and 18.02 g (0.6 mol) of polyformaldehyde were added. The temperature was raised to 70°C and refluxed for 6 h. After the reaction was completed, the organic layer was allowed to stand and separate into layers. The sulfur trioxide was removed and the concentrated solution was applied to the next batch of reactions. After concentration, the temperature was lowered and crystallization was performed, but no product was obtained.

[0071] Comparative Examples 3-6

[0072] The difference between Comparative Examples 3-6 and Comparative Example 2 is that acetonitrile, toluene, dimethyl carbonate, and ethyl methyl carbonate are used as solvents instead of ethyl acetate. No product is obtained according to the preparation and post-treatment methods of Comparative Example 2.

[0073] The yield, purity, chlorine content, free acid content, water content, metal ion content and chromaticity of methylene disulfonate obtained in Examples 1-20 and Comparative Examples 1-6 were measured, and the test results are shown in Table 2.

[0074] Table 2

[0075]

[0076]

[0077] Results and Conclusions:

[0078] As can be seen from Table 2, in Examples 1-20 of the present application, halogenated alkanes are selected as solvents, and the yield of the prepared methylene disulfonate is high, and the prepared methylene disulfonate has high purity, low chlorine content, and low impurity content. When used as an electrolyte additive, it can effectively reduce the increase in the chlorine content in the electrolyte caused by the introduction of additives. Comparative Example 1 uses sulfur trioxide as both a dehydrating agent and a solvent, and the yield of methylene disulfonate obtained is low. Comparative Examples 2-6 do not use halogenated alkanes as solvents and cannot continue to react at all. It can be seen that the method of the present application can significantly improve the yield of methylene disulfonate and reduce side reactions in the preparation process.

[0079] Compared with Examples 1-14, the mass ratio of the dehydrating agent sulfur trioxide to the halogenated alkane in Examples 15 and 16 is not within the preferred range, and the yield of the prepared methanedisulfonic acid methylene ester is significantly reduced. This may be because the content of the halogenated alkane in Example 15 is too high, which makes the dehydrating agent too dispersed, affecting its dehydration effect and reducing the yield. The content of the halogenated alkane in Example 16 is too low and is not enough to complex with the dehydrating agent sulfur trioxide, causing the dehydrating agent sulfur trioxide to participate in the side reaction and reducing the yield.

[0080] Compared with Examples 1-14, the molar ratio of methylene disulfonic acid, polyformaldehyde and dehydrating agent sulfur trioxide in Examples 17-20 is not within the preferred range, and the yield of the prepared methylene methane disulfonate is significantly reduced. This may be because when it is not within the range, methylene disulfonic acid and polyformaldehyde cannot fully react to form methylene methane disulfonate.

[0081] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0082] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for preparing methylene methanedisulfonate, characterized in that: include: dissolving sulfur trioxide in halogenated alkane to form a complex system, adding methylene disulfonic acid and paraformaldehyde to obtain a mixed solution; The mixed solution is heated to react to prepare methylene methanedisulfonate.

2. The method according to claim 1, characterized in that The halogenated alkane includes at least one of ethylene dichloride and tetrachloroethane.

3. The method according to claim 1 or 2, characterized in that: The mass ratio of the sulfur trioxide to the halogenated alkane is 1:(2-20).

4. The method according to claim 1 or 2, characterized in that: The molar ratio of the methylene disulfonic acid, the paraformaldehyde and the sulfur trioxide is 1:(1.1-1.5):(1.1-2).

5. The method according to claim 1 or 2, characterized in that: The methylene disulfonic acid is prepared by reacting methane sulfonic acid with sulfur trioxide or chlorosulfonic acid.

6. The method according to claim 1 or 2, characterized in that: The mixed solution is heated to 50° C.-130° C. to carry out the reaction; and / or, the reaction time is 2 h-10 h.

7. The method according to claim 1 or 2, characterized in that: After the heating reaction, a separation step is also included: The mixed solution after the reaction was concentrated to a saturated state, and the temperature was lowered to 5°C-10°C for crystallization to obtain a crude product; The crude product was added into dichloroethane for washing, filtered and dried to obtain methylene methanedisulfonate.

8. A methylene methanedisulfonate, characterized in that The methylene methanedisulfonate is prepared by the method according to any one of claims 1 to 7.

9. Methylene methanedisulfonate according to claim 8, characterized in that The purity of the methylene methanedisulfonate is ≥ 99.7%; and / or, Based on the total mass of the methylene methanedisulfonate, the mass proportion of chlorine element is ≤1ppm; and / or, Based on the total mass of the methylene methanedisulfonate, the mass proportion of free acid is ≤100ppm; and / or, Based on the total mass of the methylene methanedisulfonate, the mass proportion of water is ≤100ppm; and / or, Based on the total mass of the methylene methanedisulfonate, the mass proportion of any one metal element is ≤1ppm, and the metal element includes Cu, Fe, Zn, Cr, Na, K, Pb, Co, Ni, Ca, Al and Ag; and / or, The chromaticity of the methylene methanedisulfonate is ≤50 Hazen.

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