Method for preparing ferrous cyanate by using ferrous oxide as iron source

Abstract

The invention relates to the field of compound preparation, and discloses a method for preparing ferrocyanate by taking ferrous oxide as an iron source, the method comprises the following steps: contacting a raw material A containing ferrous oxide with a solution B of alkali metal cyanide, and reacting at 40-80 DEG C to obtain the ferrocyanate, the alkali metal cyanide comprising sodium cyanide and / or potassium cyanide. According to the method for preparing the ferrocyanate, sulfate containing ferrocyanide is not byproduct, the reaction temperature is mild, the cyanide hydrolysis phenomenon is basically avoided, the yield is high, NH3 and H2 are not released in the reaction process, the process is safe, and the method is a green process which is economical and reasonable in atom, free of byproduct and free of waste gas, waste residues and waste water. Compared with the traditional method, the method provided by the invention has the advantages of almost no three wastes, low production cost, high added value of products and better industrial prospect.

Description

Technical Field

[0001] This application relates to the field of compound preparation, and specifically to a method for preparing ferrocyanate using ferrous oxide as an iron source. Background Technology

[0002] Ferrocyanates, mainly sodium ferrocyanide and potassium ferrocyanide, are widely used in the pharmaceutical, pigment, tanning, metallurgical, and chemical industries as important raw materials. In recent years, they have attracted considerable attention in the industrialization process as precursors for Prussian white (PBA) cathode materials in sodium-ion batteries (SIB) and as positive and negative electrolytes in sodium-ion flow batteries.

[0003] Currently, the industrial methods for preparing these substances are mainly divided into two categories: one is the ferrous sulfate method, and the other is the reduced iron powder method.

[0004] The ferrous sulfate process refers to the production of sodium ferrocyanide using ferrous sulfate as the iron source. This method uses sodium cyanide (potassium) and ferrous sulfate as raw materials to produce sodium ferrocyanide (potassium). Under alkaline catalytic conditions, these materials are complexed to yield ferrocyanide and sodium sulfate. However, this production method suffers from difficulties in post-processing filtration, and the byproduct sodium sulfate contains 5-8% sodium ferrocyanide residue, limiting its use. Furthermore, the sodium ferrocyanide residue is classified as a solid hazardous waste, making its disposal difficult.

[0005] The reduced iron powder method uses sodium cyanide (potassium) and reduced iron powder as raw materials to prepare sodium ferrocyanide (potassium). This method has drawbacks: it requires a high reaction temperature (above 90℃) and a long reaction time; sodium cyanide hydrolyzes to sodium formate; the yield of sodium ferrocyanide (based on sodium cyanide) is 85-90%; the high sodium formate content in the mother liquor affects product quality; and the complexation reaction releases NH3 and H2 gases, impacting production safety.

[0006] To address the shortcomings of the two traditional methods mentioned above, CN115650254A proposes a pre-processed iron-based Prussian blue analogue and its preparation method. This method uses sodium cyanide as the cyanide complexing source, reduced iron powder as the iron source, sodium citrate as the complexing agent, and supplementary sodium source, employing a co-precipitation method to directly synthesize the iron-based Prussian blue analogue. This method can obtain iron-based Prussian blue analogues with particle sizes ranging from 200 nm to 2 μm, with particles having a diameter of 500 nm to 1 μm accounting for >70%. However, this method still suffers from the problem of high cost in controlling the synthesis temperature and solution ratio. Summary of the Invention

[0007] This application addresses the problems of high reaction temperatures and easy hydrolysis of alkali metal cyanides in existing technologies by providing a method for preparing ferrocyanate using ferrous oxide as the iron source. This method features a mild reaction temperature, virtually no cyanide hydrolysis, high yield, and no release of NH3 or H2 during the complexation reaction, making the process safe.

[0008] To achieve the above objective, this application provides a method for preparing ferrocyanate using ferrous oxide as an iron source. The method includes: contacting a raw material A containing ferrous oxide with a solution B of an alkali metal cyanide and reacting at 40-80°C to obtain ferrocyanate, wherein the alkali metal ions include sodium ions and / or potassium ions.

[0009] The method provided by this invention uses ferrous oxide as raw material, with mild reaction conditions, low reaction temperature, virtually no cyanide hydrolysis, high yield, and minimal release of NH3 and H2 during the reaction process. It is a safe and atom-economical green process that produces no byproducts, waste gas, waste residue, or wastewater. Compared with traditional methods, this invention generates almost no waste, has low production costs, and produces high added value, showing promising prospects for industrialization.

[0010] Taking ferrous oxide and sodium cyanide as an example, the reaction equation of this invention is as follows:

[0011] This invention does not have any special requirements regarding the source of ferrous oxide; it can be commercially available or homemade, with homemade being preferred.

[0012] Preferably, the reaction temperature is 40-60°C.

[0013] Preferably, the reaction time is 1-5 hours, more preferably 2-4 hours.

[0014] The reaction temperature of the method provided by the present invention can be any value between any two of the following: 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃. The reaction time can be any value between any two of the following: 1h, 2h, 3h, 4h, 5h.

[0015] To obtain ferrocyanide with high purity, a single alkali metal cyanide is generally used for the reaction.

[0016] Preferably, the iron element (Fe) in the raw material A and the cyanate ion (CN) in the solution B are... - The molar ratio of iron in raw material A to cyanate in solution B is 1:0.5-1.5. The molar ratio of cyanate ions to alkali metal ions in solution B is 1:1. The molar ratio of iron in raw material A to cyanate ions in solution B can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:1, 1:1.3, 1:1.5, or any value between any two of these values.

[0017] Preferably, the mass-to-volume ratio of the raw material A and the solution B is 1g:1.0-2.0mL, such as 1g:1.0mL, 1g:1.2mL, 1g:1.5mL, 1g:1.8mL, 1g:1.9mL, 1g:2.0mL, and any value between any two of these numbers.

[0018] Preferably, based on the total amount of raw material A, the content of ferrous oxide in raw material A is not less than 30 wt.%.

[0019] Preferably, based on the total amount of raw material A, the ferrous oxide content in raw material A is 60 wt.%-80 wt.%. The ferrous oxide content in raw material A can be 30 wt.%, 40 wt.%, 50 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, or any value between any two of these values.

[0020] Preferably, the source of raw material A includes at least one of the following: iron oxide scale (a by-product of steel rolling), oxidation products of elemental iron, thermal decomposition products of ferrous oxalate or ferrous carbonate, and reaction products of elemental iron and iron oxide.

[0021] Preferably, the preparation method of raw material A includes: mixing elemental iron and iron oxide (ferric oxide) at a mass ratio of 1:2-3 and firing under vacuum at 700-900℃ for 20-60 minutes to obtain raw material A. The mass ratio of elemental iron to iron oxide can be 1:2, 1:2.2, 1:2.5, 1:2.7, 1:3, or any value between any two of these ratios; the firing temperature can be 700℃, 800℃, 900℃, or any value between any two of these ratios; and the firing time can be 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, or any value between any two of these ratios.

[0022] The method further includes: after the reaction is completed, filtering to obtain filtrate and filter residue, crystallizing and centrifuging the filtrate to obtain the ferrocyanate.

[0023] The method for preparing sodium / potassium ferrocyanide provided by this invention does not produce sulfates containing ferrocyanide as a byproduct. The reaction is mild, with virtually no cyanide hydrolysis, a high yield, and minimal release of NH3 and H2. The process is safe, atom-economically efficient, and a green process with no byproducts, waste gas, waste residue, or wastewater. Compared to traditional methods, this invention generates almost no waste, has low production costs, and produces high added value, demonstrating promising prospects for industrialization.

[0024] Other features and advantages of the embodiments of this application will be described in detail in the following detailed description section. Attached Figure Description

[0025] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0026] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0027] Furthermore, the term "and / or" in the specification and claims is used to describe the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0028] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0029] The present invention will be described in detail below through examples. Unless otherwise specified, all reagents or instruments used in the following examples are commercially available conventional products. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply.

[0030] Sodium ferrocyanide is sodium ferrocyanide with 10 molecules of crystallization, commonly known as sodium prussiate of Paris. Its molecular formula is Na4Fe[(CN)6]·10H2O, and its molecular weight is 484.

[0031] Preparation Example 1 Preparation of raw material A containing ferrous oxide Fe and ferric oxide powder were ground evenly at a mass ratio of 1:2.8, pressed into tablets at 40 MPa to reduce the interatomic spacing, which facilitates the reaction between Fe and ferric oxide. The tablets were then calcined at 800℃ for 30 min under vacuum, rapidly cooled, and ground to obtain ferrous oxide powder.

[0032] Multiple batches of ferrous oxide powder were prepared using the above method. The FeO content in the powder was 60-80 wt.%, and the elemental iron content was 1-5 wt.%.

[0033] Example 1

[0034] Sodium ferrocyanide was prepared from ferrous oxide as a raw material. The reaction process is as follows: Figure 1 As shown.

[0035] (1) Preparation of micron-sized ferrous oxide powder: A batch of ferrous oxide powder from Preparation Example 1 was pre-ground under nitrogen protection to obtain micron-sized powder for later use. The FeO content was measured to be 60 wt. before feeding.

[0036] (2) Prepare 500 mL of sodium cyanide solution. Based on the total amount of sodium cyanide solution, the concentration of sodium cyanide is 158.50 g / L, that is, the content of NaCN in the solution is 79.25 g.

[0037] (3) Add 242g of micron-sized ferrous oxide powder to the sodium cyanide solution. Under nitrogen protection, with thorough stirring and reflux, heat to 45°C to start the reaction to generate sodium ferrocyanide. Keep the reaction at 55°C for 3 hours. Take samples of the sodium cyanide solution at 1 hour and 2 hours of reaction to analyze the residual NaCN in the solution. The residual NaCN in the solution is 16.0 g / L and 10.11 g / L, respectively (analyze the NaCN content to determine whether further reaction is needed).

[0038] After reacting for 3 hours, stirring was stopped, and the mixture was filtered. The residue was washed three times with 50 mL of aqueous solution. The washings and filtrate were combined to obtain a mixture of 576 mL and 220.5 g of residue. The residual NaCN in the mixture was 4.7 g / L, the sodium ferrous sulfate content (containing ten molecules of water of crystallization) was 216.7 g / L, and the sodium formate content was 0.51 g / L. The ferrous oxide content in the residue was measured to be 57.1 wt.%. Based on the analysis results, the sodium ferrous sulfate content in the mixture was 0.2579 mol, and the yield of sodium ferrous sulfate based on NaCN was 95.7%. The formula for calculating the yield of sodium ferrous sulfate based on NaCN is as follows: Yield = Actual yield of sodium ferrous sulfate / Theoretical yield of sodium ferrous sulfate × 100% = 0.2579 / (79.25 / 49 / 6) × 100% = 95.7%.

[0039] The residue obtained from filtration is dried and ground, and then reacted with sodium cyanide under this method.

[0040] To obtain dried sodium prussiate of potassium sorbate, the mixture can be filtered, cooled and crystallized, and centrifuged. The obtained solid can then be further dried to obtain dried sodium prussiate of potassium sorbate.

[0041] Example 2

[0042] (1) Preparation of micron-sized ferrous oxide powder: A batch of ferrous oxide powder from Preparation Example 1 was pre-ground under nitrogen protection to obtain micron-sized powder for later use. The FeO content was measured to be 70 wt. before feeding.

[0043] (2) Prepare 500 mL of sodium cyanide solution. Based on the total amount of sodium cyanide solution, the concentration of sodium cyanide is 158.50 g / L, that is, the content of NaCN in the solution is 79.25 g.

[0044] (3) Add 210g of micron-sized ferrous oxide powder to the sodium cyanide solution. Under nitrogen protection, with thorough stirring and reflux, heat to 45°C to start the reaction to generate sodium ferrocyanide. Keep the reaction at 55°C for 3 hours. Take samples of the sodium cyanide solution at 1 hour and 2 hours of reaction respectively to analyze the residual NaCN in the solution, which are 14.0 g / L and 9.6 g / L respectively.

[0045] After reacting for 3 hours, stirring was stopped, and the mixture was filtered. The residue was washed three times with 50 mL of aqueous solution. The washing liquid and filtrate were combined to obtain a mixture of 569 mL and 188.3 g of residue. The residual NaCN in the mixture was 4.2 g / L, the sodium ferrous sulfate content (calculated as decahydrate) was 220.2 g / L, and the sodium formate content was 0.50 g / L. The ferrous oxide content in the residue was measured to be 67.1 wt.%. Based on the analysis results, the sodium ferrous sulfate content in the mixture was 0.2589 mol, and the yield of sodium ferrous sulfate based on NaCN was 96.1%.

[0046] The resulting residue was dried and ground, and then reacted with sodium cyanide under this method.

[0047] Example 3

[0048] (1) Preparation of micron-sized ferrous oxide powder: A batch of ferrous oxide powder from Preparation Example 1 was pre-ground under nitrogen protection to obtain micron-sized powder for later use. The FeO content was measured to be 78 wt. before feeding.

[0049] (2) Prepare 500 mL of sodium cyanide solution. Based on the total amount of sodium cyanide solution, the concentration of sodium cyanide is 158.50 g / L, that is, the solution contains 79.25 g of NaCN.

[0050] (3) Add 118.5 g of micron-sized ferrous oxide powder to the sodium cyanide solution. Under nitrogen protection, with thorough stirring and reflux, heat to 45 °C to start the reaction to generate sodium ferrocyanide. Keep the reaction at 55 °C for 3 h. Take samples of the sodium cyanide solution at 1 hour and 2 hours of reaction respectively to analyze the residual NaCN in the solution, which are 14.6 g / L and 9.3 g / L respectively.

[0051] After reacting for 3 hours, stirring was stopped, and the mixture was filtered. The residue was washed three times with 50 mL of aqueous solution. The washing liquid and filtrate were combined to obtain a mixture of 592 mL and 97.8 g of residue. The residual NaCN in the mixture was 3.9 g / L, the sodium ferrous sulfate content (calculated as decahydrate) was 212.6 g / L, and the sodium formate content was 0.47 g / L. The ferrous oxide content in the residue was measured to be 74.5 wt.%. Based on the analysis results, the sodium ferrous sulfate content in the mixture was 0.2600 mol, and the yield of sodium ferrous sulfate based on NaCN was 96.5%.

[0052] The resulting residue was dried and ground, and then reacted with sodium cyanide under this method.

[0053] Comparative Example 1 50 g of reduced iron powder containing 95% elemental Fe and 100 mL of 30% sodium cyanide solution (density 1.13 g / cm³) were added to the reactor. 3 (Containing 33.9 g of NaCN), the reaction started at 45°C with stirring at 150 rpm. The reaction was exothermic and the temperature naturally rose to about 95°C. A large amount of gas was continuously released during the reaction. After 6 hours of reaction, the reaction was stopped, and the unreacted iron powder was filtered and washed to obtain 425 mL of mixed liquid and a certain amount of residue.

[0054] Sampling analysis showed that the sodium cyanide content in the mixture was 3 g / L, the sodium formate content was 14.3 g / L, gas was continuously generated during the reaction, the sodium cyanide content (including ten molecules of water of crystallization) was 107.84 g / L, the sodium cyanide content was 0.095 mol, the total mass of sodium cyanide was 45.83 g, and the yield of sodium cyanide calculated as NaCN was 82.4%.

[0055] It is evident that, compared with traditional methods using elemental iron as raw material, the yield of sodium prussiate of the present invention (calculated as NaCN) is significantly improved.

[0056] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing ferrocyanide using ferrous oxide as a source of iron, characterized by, The method comprises: contacting raw material A containing ferrous oxide and solution B of alkali metal cyanide, and reacting at 40-80 DEG C to obtain ferrocyanide, wherein the alkali metal cyanide comprises sodium cyanide and / or potassium cyanide.

2. The method of claim 1, wherein, The reaction temperature is 40-60 DEG C.

3. The method of claim 1 or 2, wherein, The molar ratio of iron in the raw material A to cyanate in the solution B is 1:0.5-1.

5.

4. The method of claim 3, wherein, The mass-volume ratio of the raw material A to the solution B is 1g:1-2mL.

5. The method of claim 1, 2, or 4, wherein, The content of ferrous oxide in the raw material A is not less than 30wt.% based on the total amount of the raw material A.

6. The method of claim 5, wherein, The content of ferrous oxide in the raw material A is 60wt.%-80wt.% based on the total amount of the raw material A.

7. The method of claim 3, wherein, The source of the raw material A comprises at least one of the following: mill scale, oxidation product of elemental iron, thermal decomposition product of ferrous oxalate or ferrous carbonate, and reaction product of elemental iron and iron oxide.

8. The method of claim 7, wherein, The preparation method of the raw material A comprises: mixing elemental iron and iron oxide at a mass ratio of 1:2-3, and then firing at 700-900 DEG C under vacuum for 20-60min to obtain the raw material A.

9. The method of claim 1, wherein, The method further comprises: after the reaction, filtering to obtain filtrate and residue, and crystallizing and centrifuging the filtrate to obtain the ferrocyanide.

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