Preparation method of hydrogen oxalate and hydrogen oxalate

Abstract

The invention provides a preparation method of hydrogen oxalate. The preparation method of the hydrogen oxalate comprises the step of reacting oxalic acid with alkali metal hydroxide to prepare the hydrogen oxalate. According to the preparation method, impurity ions cannot be introduced into a reaction system, a byproduct is only water, and high-purity and low-water-content hydrooxalate can be obtained.

Description

Technical Field

[0001] The invention relates to a preparation method of hydrogen oxalate and hydrogen oxalate, belonging to the technical field of energy. Background Art

[0002] The rapidly growing energy market demand has driven ion batteries to develop in the direction of high energy density and long life. Studies have found that the introduction of electrolyte additives to stabilize the electrode-electrolyte interface can improve the energy density of ion batteries and extend the service life of ion batteries. Fluorine-containing oxalates such as lithium difluorooxalatoborate (LiODFB) and lithium bis(oxalatoborate) (LiBOB) have been widely used as representatives of electrolyte additives.

[0003] Bioxalate is one of the raw materials for preparing fluorine-containing oxalates such as LiODFB. The prior art often uses chloride to react with oxalic acid to prepare bioxalate. However, this reaction not only produces acidic tail gas hydrogen chloride, but also chloride as a raw material will introduce chloride ions into the reaction system, increasing the difficulty of purifying the product; and in the preparation method disclosed in the prior art, bioxalate only appears in the form of an intermediate, and a high-purity lithium hydrogen oxalate product is not prepared, which is not conducive to the practical application of lithium hydrogen oxalate. Summary of the invention

[0004] The invention provides a method for preparing hydrogen oxalate. The method not only does not introduce impurity ions into a reaction system, but also has only water as a byproduct, thereby obtaining hydrogen oxalate with high purity and low water content.

[0005] The hydrogen oxalate of the present invention is prepared by the above-mentioned preparation method, has a simple preparation process and high purity, and is suitable for wide promotion and application.

[0006] The invention provides a method for preparing hydrogen oxalate, wherein oxalic acid and alkali metal hydroxide are reacted to prepare the hydrogen oxalate.

[0007] In the preparation method as described above, the alkali metal hydroxide is selected from at least one of lithium hydroxide, sodium hydroxide and potassium hydroxide.

[0008] In the preparation method as described above, the molar ratio of the alkali metal hydroxide to the oxalic acid is 1:(0.9-1.2).

[0009] The preparation method as described above, wherein the reaction temperature is 20-80°C; and / or,

[0010] The pH at the end point of the reaction is 1-5.

[0011] The preparation method as described above, wherein the reaction further includes post-treatment, and the post-treatment includes:

[0012] Dissolving a mixed system including hydrogen oxalate obtained by reacting an alkali metal hydroxide with oxalic acid to dissolve the hydrogen oxalate in the mixed system to obtain a first system;

[0013] performing a cooling and crystallization treatment on the first system to precipitate hydrogen oxalate crystals in the first system to obtain a second system;

[0014] filtering the second system to obtain hydrogen oxalate crystals;

[0015] The hydrogen oxalate crystals are dried to obtain the hydrogen oxalate.

[0016] The preparation method as described above, wherein the temperature during the dissolution treatment is 60-100° C.; and / or,

[0017] In the cooling and crystallization treatment, the temperature is 0-25°C, the rotation speed is 10-50rpm, and the time is 0.5-4h; and / or,

[0018] During the drying process, the temperature is 100-130° C. and the time is 4-10 hours.

[0019] The preparation method as described above, wherein the step of using oxalic acid and an alkali metal hydroxide to react to prepare hydrogen oxalate comprises:

[0020] Oxalic acid is added to a stirred alkali metal hydroxide solution to react and prepare hydrogen oxalate.

[0021] In the preparation method as described above, the molar concentration of alkali metal ions in the alkali metal hydroxide solution is (1-2) mol / L.

[0022] The present invention provides a hydrogen oxalate, wherein the hydrogen oxalate is prepared by the above-mentioned preparation method.

[0023] The hydrogen oxalate as described above, wherein the hydrogen oxalate has a purity of ≥99.5%, a moisture content of <50ppm, a chloride ion content of <20ppm, and a particle size of 10-100μm.

[0024] The method for preparing hydrogen oxalate of the present invention uses oxalic acid and alkali metal hydroxide to react to prepare hydrogen oxalate, and no impurity ions are introduced into the reaction system, which is helpful for obtaining high-purity hydrogen oxalate, and the byproduct is only water, which can be recycled as a solvent, which is helpful for saving costs.

[0025] The hydrogen oxalate of the present invention is prepared by the above-mentioned preparation method, has high purity and is simple in preparation method, and is suitable for wide promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present invention or related technologies. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 is the XRD pattern of lithium hydrogen oxalate in Example 1 of the present invention;

[0028] Figure 2 This is a morphology diagram of lithium hydrogen oxalate in Example 1 of the present invention;

[0029] Figure 3 This is a morphology diagram of lithium hydrogen oxalate in Example 6 of the present invention;

[0030] Figure 4 This is a morphology diagram of lithium hydrogen oxalate in Example 8 of the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] A first aspect of the present invention provides a method for preparing hydrogen oxalate, wherein the hydrogen oxalate is prepared by reacting oxalic acid with an alkali metal hydroxide.

[0033] The present invention does not particularly limit oxalic acid, and oxalic acid may be oxalic acid commonly used in the art, for example, oxalic acid dihydrate. The present invention does not particularly limit alkali metal hydroxide, and alkali metal hydroxide may be alkali metal hydroxide commonly used in the art, for example, lithium hydroxide monohydrate, sodium hydroxide or potassium hydroxide. The hydrogen oxalate of the present invention may be lithium hydrogen oxalate, sodium hydrogen oxalate or potassium hydrogen oxalate.

[0034] As shown in Formula 1, in the preparation method of the present invention, oxalic acid reacts with an alkali metal hydroxide to obtain hydrogen oxalate and water;

[0035] H 2 C 2 O 4 +XOH → XHC 2 O 4 +H 2 O Formula 1

[0036] In Formula 1, X may be Na, K, or Li.

[0037] The present invention uses oxalic acid and alkali metal hydroxide to react to prepare hydrogen oxalate, and no impurity ions are introduced into the reaction system, which is helpful to obtain high-purity hydrogen oxalate, and its byproduct is only water, which can be reused as a solvent, which is helpful to save costs.

[0038] In some embodiments of the present invention, when the molar ratio of alkali metal hydroxide to oxalic acid is 1:(0.9-1.2), the alkali metal hydroxide and oxalic acid can be fully reacted while saving raw materials, thereby improving the purity and yield of hydrogen oxalate.

[0039] In the present invention, the temperature of the reaction process can be specifically selected to more efficiently generate hydrogen oxalate while saving energy consumption and improving safety performance. The exemplary reaction temperature is 20-80°C.

[0040] Furthermore, when the pH at the end point of the reaction is 1-5, high-quality hydrogen oxalate can be obtained.

[0041] In some embodiments of the present invention, a post-treatment is further included after the reaction, and the post-treatment includes:

[0042] Dissolving a mixed system including hydrogen oxalate obtained by reacting an alkali metal hydroxide with oxalic acid to dissolve the hydrogen oxalate in the mixed system to obtain a first system;

[0043] Performing a cooling and crystallization treatment on the first system to precipitate hydrogen oxalate crystals in the first system to obtain a second system;

[0044] filtering the second system to obtain hydrogen oxalate crystals;

[0045] The hydrogen oxalate crystals are dried to obtain hydrogen oxalate.

[0046] Specifically, the preparation method of hydrogen oxalate of the present invention comprises: using alkali metal hydroxide to react with oxalic acid to obtain a mixed system including hydrogen oxalate, dissolving the mixed system to dissolve the hydrogen oxalate in the mixed system to obtain a first system including hydrogen oxalate, cooling and crystallizing the first system to precipitate hydrogen oxalate crystals in the first system to obtain a second system, filtering the second system to obtain hydrogen oxalate crystals and a filtrate, and drying the hydrogen oxalate crystals to obtain hydrogen oxalate.

[0047] The present invention can obtain hydrogen oxalate with better purity and increase the yield of hydrogen oxalate by post-treating the mixed system including hydrogen oxalate after the reaction.

[0048] The invention can obtain hydrogen oxalate with different particle sizes (10-100 microns) by post-treating the mixed system including hydrogen oxalate after the reaction and controlling different dissolving temperatures, cooling temperatures and cooling stirring rates.

[0049] The present invention can further select the temperature of the dissolution treatment, the cooling crystallization treatment and the drying treatment to improve the effect of the post-treatment and increase the purity and yield of the hydrogen oxalate. In some embodiments of the present invention, when the temperature of the dissolution treatment is 60-100°C, the hydrogen oxalate in the mixed system including the hydrogen oxalate obtained by the reaction of the alkali metal hydroxide and oxalic acid can be fully dissolved while saving energy, thereby improving the purity and yield of the hydrogen oxalate.

[0050] In some embodiments of the present invention, the temperature of the cooling crystallization treatment is 0-25°C, the rotation speed is 10-50 rpm, and the time is 0.5-4h.

[0051] The inventors found in their research that the higher the rotation speed in the cooling and crystallization process, the smaller the particle size of the obtained hydrogen oxalate. The present invention can obtain hydrogen oxalate with a particle size of 10-100 microns by selecting the rotation speed, time and temperature in the cooling and crystallization process. The obtained hydrogen oxalate has a moderate particle size and can be widely used in lithium ion battery electrolytes.

[0052] Furthermore, when the temperature during the drying process is 100-130° C. and the time is 4-10 h, the water in the obtained hydrogen oxalate can be fully evaporated while saving energy, thereby obtaining hydrogen oxalate with excellent quality.

[0053] In some embodiments of the present invention, the method of preparing hydrogen oxalate by reacting oxalic acid with an alkali metal hydroxide comprises:

[0054] Oxalic acid is added to a stirred alkali metal hydroxide solution to react and prepare hydrogen oxalate.

[0055] Specifically, the alkali metal hydroxide solution is stirred, and oxalic acid is added to the stirred alkali metal hydroxide solution to allow the oxalic acid and the alkali metal hydroxide to react sufficiently to obtain hydrogen oxalate.

[0056] In some embodiments, oxalic acid may be added to the stirred alkali metal hydroxide solution in multiple portions.

[0057] The present invention adds oxalic acid to a stirred alkali metal hydroxide solution, thereby reducing local overheating, lowering the risk of reaction, and enabling oxalic acid to react more fully with the alkali metal hydroxide, thereby improving the yield of hydrogen oxalate.

[0058] In the present invention, the alkali metal hydroxide solution can be an alkali metal hydroxide aqueous solution. Further, when the molar concentration of the alkali metal ions in the alkali metal hydroxide solution is (1-2) mol / L, it helps to further improve the yield and purity of hydrogen oxalate.

[0059] In some embodiments, alkali metal hydroxide and water may be added to the filtrate after the filtration treatment to prepare an alkali metal hydroxide solution, which is then reacted with oxalic acid to prepare hydrogen oxalate.

[0060] The second aspect of the present invention provides a hydrogen oxalate, which is prepared by the above-mentioned preparation method.

[0061] The hydrogen oxalate of the present invention is prepared by the above-mentioned preparation method, has a simple preparation process and high purity, and is suitable for wide promotion and application.

[0062] In some embodiments of the present invention, when the purity of hydrogen oxalate is ≥99.5%, the moisture content is <50ppm, the chloride ion content is <20ppm, and the particle size is 10-100μm, the obtained hydrogen oxalate can be more widely used in lithium-ion battery electrolytes.

[0063] Specifically, when the particle size of hydrogen oxalate is 10-100 μm, the dissolution rate and reaction rate of the hydrogen oxalate are excellent, and the application range is wide; and during the application of hydrogen oxalate, the hydrogen oxalate will be filtered. The particle size of hydrogen oxalate will not only affect the selection of filtering equipment, but also affect the filtration rate. When the particle size of hydrogen oxalate is 10-100 μm, lithium hydrogen oxalate can be filtered more efficiently, broadening the application of hydrogen oxalate.

[0064] When the water content of hydrogen oxalate is less than 50 ppm and the chloride ion content is less than 20 ppm, side reactions are not likely to occur when applied to batteries.

[0065] The following describes the solution of the present invention in detail through specific embodiments.

[0066] Example 1

[0067] The preparation method of lithium hydrogen oxalate in this embodiment comprises:

[0068] At room temperature, add 320mL of deionized water to a 500mL three-necked flask, add 18.64g of lithium hydroxide monohydrate (the molar concentration of alkali metal ions is 1.39mol / L) under stirring, add oxalic acid dihydrate every 10min, add about 10g each time, add 56g of oxalic acid dihydrate in total, the molar ratio of oxalic acid dihydrate to lithium hydroxide monohydrate is 1:1, heat to 60℃ and stir until the pH is stable (2.3±0.3), and the reaction is over. Dissolve at 80℃, then stir at 30rmp, cool the reaction solution to 0℃, and keep it for 0.5h for cooling and crystallization, filter while cold, the filtrate can be used to continue to prepare lithium hydroxide solution for application, filter the solid obtained by vacuum drying at 130℃ for 4h to obtain LiHC 2 O 4 solid.

[0069] Example 2

[0070] The preparation method of lithium hydrogen oxalate in this embodiment comprises:

[0071] At room temperature, add 320mL of deionized water to a 500mL three-necked flask, add 18.64g of lithium hydroxide monohydrate (the molar concentration of alkali metal ions is 1.39mol / L) under stirring, add oxalic acid dihydrate once every 10min, add about 10g each time, add 66.65g of oxalic acid dihydrate in total, the molar ratio of oxalic acid dihydrate to lithium hydroxide monohydrate is 1.2:1, stir at room temperature (20℃) until the pH is stable (1.3±0.3), and the reaction is completed. Dissolve at 100℃, then stir at 20rmp, cool the reaction solution to 5℃, and keep it for 0.5h for cooling and crystallization, filter while cold, the filtrate can be used to continue to prepare lithium hydroxide solution for application, filter the solid obtained by vacuum drying at 120℃ for 6h to obtain LiHC 2 O 4 solid.

[0072] Example 3

[0073] The preparation method of lithium hydrogen oxalate in this embodiment comprises:

[0074] At room temperature, add 350mL of deionized water to a 500mL three-necked flask, add 22.37g of lithium hydroxide monohydrate (the molar concentration of alkali metal ions is 1.53mol / L) under stirring, add oxalic acid dihydrate once every 10min, add about 10g each time, add 66.25g of oxalic acid dihydrate in total, the molar ratio of oxalic acid dihydrate to lithium hydroxide monohydrate is 0.9:1, heat to 40℃ and stir until the pH is stable (4±0.3), and the reaction is over. Dissolve at 100℃, then stir at 25rmp, cool the reaction solution to 5℃, and keep it for 0.5h for cooling and crystallization, filter while cold, the filtrate can be used to continue to prepare lithium hydroxide solution for application, filter the solid obtained by vacuum drying at 120℃ for 6h to obtain LiHC 2 O 4 solid.

[0075] Example 4

[0076] The preparation method of sodium hydrogen oxalate of the present embodiment comprises:

[0077] At room temperature, add 300mL of deionized water to a 500mL three-necked flask, add 17.78g of sodium hydroxide (the molar concentration of alkali metal ions is 1.48mol / L) under stirring, add oxalic acid dihydrate once every 10min, add about 10g each time, add 61.1g of oxalic acid dihydrate in total, the molar ratio of oxalic acid dihydrate to sodium hydroxide is 1:1, heat to 80℃ and stir until the pH is stable (3.0±0.3), and the reaction is over. Dissolve at 100℃, then stir at 30rmp, cool the reaction solution to 5℃, and keep it for 0.5h for cooling and crystallization, filter while cold, the filtrate can be used to continue to prepare sodium hydroxide solution for application, filter the solid obtained by vacuum drying at 100℃ for 10h to obtain NaHC 2 O 4 solid.

[0078] Example 5

[0079] The preparation method of potassium hydrogen oxalate of the present embodiment comprises:

[0080] At room temperature, add 250mL of deionized water to a 500mL three-necked flask, add 24.92g of potassium hydroxide (the molar concentration of alkali metal ions is 1.78mol / L) under stirring, add oxalic acid dihydrate once every 10min, add about 10g each time, add 61.1g of oxalic acid dihydrate in total, the molar ratio of oxalic acid dihydrate to potassium hydroxide is 1:1, heat to 60℃ and stir until the pH is stable (4.7±0.3), and the reaction is over. Dissolve at 100℃, then stir at 30rmp, cool the reaction solution to 25℃, and keep it for 0.5h for cooling and crystallization, filter while cold, the filtrate can be used to continue to prepare potassium hydroxide solution for application, filter the solid obtained by vacuum drying at 120℃ for 6h to obtain KHC 2 O 4 solid.

[0081] Example 6

[0082] The preparation method of lithium hydrogen oxalate in this embodiment is basically the same as that in Example 1, except that: during the cooling crystallization process, the rotation speed is 50 rpm.

[0083] Example 7

[0084] The preparation method of lithium hydrogen oxalate in this embodiment is basically the same as that in Example 1, except that: during the cooling crystallization process, the rotation speed is 10 rpm.

[0085] Example 8

[0086] The preparation method of lithium hydrogen oxalate in this embodiment is basically the same as that in Example 1, except that: during the cooling crystallization process, no stirring process is performed and the rotation speed is 0 rpm.

[0087] Example 9

[0088] The preparation method of lithium hydrogen oxalate in this embodiment is basically the same as that in Example 1, except that: the mixed system including lithium hydrogen oxalate obtained by the reaction is not subjected to temperature rise for dissolution, and is directly subjected to temperature drop for crystallization after the reaction is completed, and is filtered while cold, and the solid obtained by filtration is dried under reduced pressure at 130° C. for 4 h to obtain LiHC 2 O 4 solid.

[0089] Example 10

[0090] The preparation method of lithium hydrogen oxalate in this embodiment is basically the same as that in Example 1, except that the reaction temperature is 20°C.

[0091] Embodiment 11

[0092] The preparation method of lithium hydrogen oxalate in this embodiment is basically the same as that in Example 1, except that: during the dissolution treatment, the temperature is 60°C.

[0093] Example 12

[0094] The preparation method of lithium hydrogen oxalate in this embodiment is basically the same as that in Example 1, except that the molar concentration of the alkali metal ions is 1 mol / L.

[0095] Example 13

[0096] The preparation method of lithium hydrogen oxalate in this embodiment is basically the same as that in Example 1, except that the molar concentration of the alkali metal ions is 2 mol / L.

[0097] Embodiment 14

[0098] The preparation method of lithium hydrogen oxalate in this embodiment is basically the same as that in Example 1, except that the molar concentration of the alkali metal ions is 2.5 mol / L.

[0099] Embodiment 15

[0100] The preparation method of lithium hydrogen oxalate in this embodiment is basically the same as that in Example 1, except that the molar ratio of oxalic acid dihydrate to lithium hydroxide monohydrate is 1.3:1.

[0101] Example 16

[0102] The preparation method of lithium hydrogen oxalate in this embodiment is basically the same as that in Example 1, except that the molar ratio of oxalic acid dihydrate to lithium hydroxide monohydrate is 0.8:1.

[0103] Comparative Example 1

[0104] The preparation method of lithium hydrogen oxalate in this comparative example comprises:

[0105] At room temperature, add 320 mL of deionized water to a 500 mL three-necked flask, add 18.83 g of lithium chloride (the molar concentration of alkali metal ions is 1.39 mol / L) under stirring, add oxalic acid dihydrate every 10 min, add about 10 g each time, add 56 g of oxalic acid dihydrate in total, the molar ratio of oxalic acid dihydrate to lithium chloride is 1:1, heat to 80 ° C and stir, react for 4 hours, and the reaction is completed. Dissolve at 80 ° C, then stir at 30 rmp, cool the reaction solution to 0 ° C, and keep it for 0.5 hours for cooling and crystallization, filter while cold, and dry the solid obtained by filtration at 130 ° C under reduced pressure for 4 hours to obtain LiHC 2 O 4 solid.

[0106] Performance Testing

[0107] The following performance tests were performed on the hydrogen oxalate in the examples and comparative examples. The test results are shown in Figure 1 and Table 1;

[0108] 1. XRD test

[0109] The lithium hydrogen oxalate in Example 1 was subjected to XRD test. Figure 1 This is the XRD diagram of lithium hydrogen oxalate in Example 1 of the present invention. Figure 1 The spectrum in the XRD results of C 2 HkDJ 4 ·H 2 O standard card was used to calculate the FOM value. The calculated FOM value was 0.32, and it could be determined that the product was lithium hydrogen oxalate.

[0110] 2. Purity

[0111] According to the raw material analysis, the impurities that may be contained in hydrogen oxalate are oxalic acid, alkali metal hydroxide, and by-product oxalate. Therefore, potassium permanganate is used to titrate the oxalate ions in hydrogen oxalate, and sodium hydroxide is used to titrate the hydrogen ions in hydrogen oxalate to calculate the content (purity) of hydrogen oxalate, which specifically includes:

[0112] Take mg of product and titrate with potassium permanganate, the result is the amount of oxalate ions (x mol), titrate with sodium hydroxide, the result is the amount of hydrogen ions (y mol), if x>y, the purity of hydrogen oxalate is:

[0113] y*95.968 / m*100% Formula 2 If y>x, the purity of hydrogen oxalate is:

[0114] x*95.968 / m*100% Formula 3.

[0115] 3. Yield

[0116] According to the hydrogen oxalate preparation reaction equation (Formula 1), the theoretical amount of hydrogen oxalate produced ng and the actual amount of pure hydrogen oxalate product collected mg were calculated, and the hydrogen oxalate reaction yield was calculated:

[0117] m / n*100% Formula 4

[0118] 4. Particle size

[0119] The particle sizes of the hydrogen oxalate obtained in the embodiment and the comparative example were measured using a particle size analyzer. The results are shown in Table 1. Figure 2 This is a morphology diagram of lithium hydrogen oxalate in Example 1 of the present invention; Figure 3 This is a morphology diagram of lithium hydrogen oxalate in Example 6 of the present invention; Figure 4 This is a morphology diagram of lithium hydrogen oxalate in Example 8 of the present invention. Figure 2-4 It can be seen that the lower the rotation speed during the cooling crystallization process, the larger the particle size of the obtained lithium hydrogen oxalate.

[0120] 5. Moisture

[0121] Use a cardboard furnace to test moisture.

[0122] 6. Chloride ion content (Cl - )

[0123] The chloride ion content was determined by potentiometric titration (AgNO 3 ) detection.

[0124] Table 1

[0125]

[0126] It can be seen from Table 1 that the purity and yield of the hydrogen oxalate obtained in the embodiment of the present invention are much better than those of the hydrogen oxalate obtained in the comparative example, and the chloride ion content of the hydrogen oxalate in the embodiment of the present invention is much less than that of the hydrogen oxalate in the comparative example. Therefore, the hydrogen oxalate obtained by the preparation method of the present invention is more suitable for use in batteries;

[0127] Furthermore, it can be seen from Examples 1 and 9 that the present invention can effectively improve the purity of the product hydrogen oxalate through a specific post-treatment process;

[0128] It can be seen from Examples 1, 12, 13 and 14 that by further selecting the molar concentration of the alkali metal ions in the alkali metal hydroxide solution, the purity of the hydrogen oxalate can be improved while ensuring the yield of the hydrogen oxalate;

[0129] It can be seen from Example 1 and Examples 15-16 that by further selecting the molar ratio of the alkali metal hydroxide to oxalic acid, the purity of the hydrogen oxalate can be improved while ensuring the yield of the hydrogen oxalate.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing hydrogen oxalate, It is characterized in that Hydrogen oxalate is prepared by reacting oxalic acid with an alkali metal hydroxide.

2. The preparation method according to claim 1, It is characterized in that The alkali metal hydroxide is selected from at least one of lithium hydroxide, sodium hydroxide and potassium hydroxide.

3. The preparation method according to claim 1 or 2, It is characterized in that The molar ratio of the alkali metal hydroxide to the oxalic acid is 1:(0.9-1.2).

4. The preparation method according to any one of claims 1 to 3, It is characterized in that The reaction temperature is 20-80°C; and / or, The pH at the end point of the reaction is 1-5.

5. The preparation method according to any one of claims 1 to 4, It is characterized in that The reaction is followed by post-treatment, which includes: Dissolving a mixed system including hydrogen oxalate obtained by reacting an alkali metal hydroxide with oxalic acid to dissolve the hydrogen oxalate in the mixed system to obtain a first system; performing a cooling and crystallization treatment on the first system to precipitate hydrogen oxalate crystals in the first system to obtain a second system; filtering the second system to obtain hydrogen oxalate crystals; The hydrogen oxalate crystals are dried to obtain the hydrogen oxalate.

6. The preparation method according to claim 5, It is characterized in that During the dissolution treatment, the temperature is 60-100°C; and / or, In the cooling and crystallization treatment, the temperature is 0-25°C, the rotation speed is 10-50rpm, and the time is 0.5-4h; and / or, During the drying process, the temperature is 100-130° C. and the time is 4-10 hours.

7. The preparation method according to any one of claims 1 to 5, It is characterized in that The method of using oxalic acid and alkali metal hydroxide to react to prepare hydrogen oxalate comprises: Oxalic acid is added to a stirred alkali metal hydroxide solution to react and prepare hydrogen oxalate.

8. The preparation method according to claim 6, It is characterized in that In the alkali metal hydroxide solution, the molar concentration of alkali metal ions is (1-2) mol / L.

9. A salt of hydrogen oxalate, It is characterized in that It is prepared by the preparation method according to any one of claims 1 to 7.

10. The hydrogen oxalate according to claim 9, It is characterized in that The hydrogen oxalate has a purity of ≥99.5%, a moisture content of <50ppm, a chloride ion content of <20ppm, and a particle size of 10-100μm.

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