Low-consumption environment-friendly hypophosphite purification process

Abstract

The invention discloses a low-consumption and environment-friendly hypophosphite purification process, and belongs to the technical field of hypophosphite purification. Comprising the following steps: S1, heating and dissolving hypophosphite raw material powder and ultrapure water according to a certain proportion, mixing, and filtering by adopting a microfiltration membrane to remove particulate matters; s2, adding a proper amount of chelating agent into the filtrate of the hypophosphite, conveying the filtrate into a dynamic crystallization kettle, and slowly cooling and crystallizing; s3, separating hypophosphite mother liquor from crystals, and drying the hypophosphite crystals; and S4, purifying the hypophosphite mother liquor by using macroporous adsorption resin so that the hypophosphite mother liquor is used for the crystallization process of a new batch of materials again.

Description

Technical Field

[0001] The invention relates to a purification process of sodium hypophosphite, and specifically the purification of sodium hypophosphite is achieved through the process of ointment chelation, crystallization and resin purification. Background Art

[0002] Hypophosphite has strong reducing properties and is commonly used in meat products as a preservative and antioxidant in place of nitrite. It is also used in the electronics industry as a raw material for capacitor-grade electrolytes. It is also used as a reducing agent and polyamide catalyst in electroless nickel plating processes and is also used in biological research and the pharmaceutical industry. The hypophosphite mentioned in this invention is any of sodium hypophosphite, calcium hypophosphite, and ammonium hypophosphite.

[0003] There is a great deal of environmental pollution in the production process of hypophosphite. Some companies have to stop production or directly withdraw from the market due to non-compliance with environmental standards. On the demand side, due to the backward technology of China's hypophosphite industry and the low enthusiasm of companies for technological development, the quality of hypophosphite products has always been at the mid-to-low end and cannot meet the needs of downstream fields such as food, medicine, and electronics industry.

[0004] At present, the common purification schemes for hypophosphite are crystallization, ion exchange and precipitation. The crystallization method uses the difference in solubility and crystallization characteristics between hypophosphite and phosphite to efficiently separate phosphite impurities. However, it is difficult to separate and remove metal impurities in the form of compounds in hypophosphite, such as iron hypophosphite, barium hypophosphite and other metal impurities by crystallization. The ion exchange method can efficiently remove metal impurities and anionic impurities in hypophosphite, but the cost of using ion resins is high, and most ion exchange resins have weak regeneration capabilities. Hypophosphite will bring in a large amount of SO4 during the production process. 2- ions, SO4 2- For ions, the common removal method is to add Ba salt to form Ba salt precipitation, but this solution will introduce a small amount of Ba 2+ Ionic impurities. Summary of the Invention

[0005] One of the purposes of the present invention is to overcome the defects of the above-mentioned purification scheme and provide a low-consumption and environmentally friendly hypophosphite purification process. The purification process has less pollution, high raw material utilization rate, and is easy to operate on a large scale. The purity of the obtained product can reach electronic grade at most.

[0006] The low-consumption and environmentally friendly hypophosphite purification process of the present invention comprises the following steps: S1. Mixing the hypophosphite raw material powder with ultrapure water, heating and dissolving the mixture, and then filtering out the particulate impurities using a microfiltration membrane; S2, adding an appropriate amount of chelating agent to the filtrate obtained in step S1, stirring evenly, and then transporting it to a dynamic crystallization kettle, and slowly cooling and crystallizing; S3, releasing hypophosphite crystals and mother liquor from the bottom of the crystallization reactor, separating the hypophosphite mother liquor from the crystals, and drying the hypophosphite crystals; S4. The hypophosphite mother liquor is passed through a macroporous adsorption resin to remove the chelate in the mother liquor and is used again in the crystallization process of a new batch of materials.

[0007] Preferably, the hypophosphite includes any one of sodium hypophosphite, calcium hypophosphite and ammonium hypophosphite.

[0008] The raw material is industrial-grade hypophosphite with a purity of 95.5-99.5%, wherein the metal impurities mainly include Fe, Ba, Cu, Mg, Ag, Al, Zn, Pb, Cd, Cr, Co and other metals, and the total content of metal impurities is about 15ppm. These metal impurities mainly come from the precipitation of hypophosphite production equipment and the metal impurities entrained in the raw material yellow phosphorus.

[0009] Preferably, in step S1, the mixing ratio of hypophosphite powder to ultrapure water is 2:0.5-1.5, and after mixing, the mixture is heated and stirred until completely dissolved.

[0010] Preferably, the microfiltration membrane in S1 is made of one of HEPE, PA, PTFE or PS, and has a filtration accuracy of 0.1 μm to 1.0 μm.

[0011] The filtration accuracy of the microfiltration membrane described in step S1 is 0.1 μm, 0.2 μm, 0.5 μm, and 1.0 μm.

[0012] Preferably, the filtration speed of the microfiltration membrane in step S1 is 8-15 m / h.

[0013] Some metal impurities combine with phosphate ions to form hypophosphites, such as barium hypophosphite and zinc hypophosphite. These hypophosphites have low solubility and preferentially form crystals during the cooling crystallization process, eventually mixing with the product and making it difficult to separate. Therefore, a suitable chelating agent is selected and added to the hypophosphite solution before crystallization to form a soluble chelate with the metal impurities. Crystallization then proceeds, allowing the metal impurities to be enriched in the crystallization mother liquor in the form of a chelate. Different chelating agents have varying selectivity for various metal impurities. For example, trisodium ethylenediamine disuccinate, ethylenediamine disuccinic acid, and nitrilotriacetic acid preferentially chelate transition metal ions such as Fe and Cu; polyvinyl alcohol and N,N,N-tris(carboxymethyl)ethylenediamine preferentially form stable complexes with metal ions such as Cu, Zn, and Ni; and ethylenediaminetetraacetic acid chelating agents preferentially combine with metal ions such as Mg and Ba to form stable chelates.

[0014] Preferably, the chelating agent added to the filtrate in step S2 is two or three of trisodium ethylenediamine disuccinate, ethylenediamine disuccinic acid, nitrilotriacetic acid, sodium hexametaphosphate, tri(2-carboxyethyl)phosphine, trisodium methylglycine diacetate, sodium diethyldithiocarbamate, silver diethyldithiocarbamate, polyvinyl alcohol, N,N,N-tris(carboxymethyl)ethylenediamine, disodium ethylenediaminetetraacetic acid, and ethylenediaminetetraacetic acid.

[0015] The added amount of the chelating agent is 0.01-1‰ of the total mass of the sodium hypophosphite solution.

[0016] In the preferred S2, the hypophosphite solution is cooled in the crystallization reactor at a rate of 10-20°C / h.

[0017] In the preferred S2, during the crystallization process of the hypophosphite solution in the crystallization reactor, the rotation speed of the stirring paddle is 70-150 rpm.

[0018] More preferably, the temperature set for heating and drying in the vacuum drying oven is 30-55°C.

[0019] Preferably, the product after the drying treatment in step S3 is vacuum-packed and stored.

[0020] The macroporous adsorption resin is a non-ionic macroporous adsorption resin. The macroporous adsorption resin is a non-ionic macroporous adsorption resin. The non-ionic macroporous adsorption resin includes any two or more of Zhengguang HOSD11, Zhengguang HOSD9, DuPont XAD3, DuPont XAD4, HiSilicon XAD2, HiSilicon HPD400, and HiSilicon HPD700Z.

[0021] The combination refers to a combination obtained by loading a resin column with any one of Zhengguang HOSD11, Zhengguang HOSD9, DuPont XAD4, DuPont AB-8, HiSilicon XAD2, HiSilicon HPD400, and HiSilicon HPD700Z and then connecting them in series.

[0022] The researchers of the present invention conducted screening tests on the resins. In the mother liquor after crystallization, the metal ion impurities combined with the chelating agent to form chelates; some chelates had a large molecular weight, and the adsorption effect of ionic resins on such impurities was poor; the pore size of the gel-type resin was relatively small, and the gel pores were easily clogged, resulting in a serious reduction in the resin life; after screening, it was found that the non-ionic macroporous network structure resin in the present application can effectively adsorb organic impurities in the mother liquor and efficiently remove metal impurities in the mother liquor.

[0023] Preferably, the average pore size of the macroporous adsorption resin is 6.0-25.0 nm.

[0024] Preferably, the regeneration agent used in the regeneration process of the macroporous adsorption resin in step S4 is one or two of sulfuric acid, phosphoric acid, hydrochloric acid, anhydrous ethanol, and sodium hydroxide.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a low-cost and environmentally friendly process for purifying hypophosphite. By utilizing the selectivity of chelating agents for metal ions, a suitable chelating agent is added before crystallization to prevent some metal impurities from participating in the crystallization process of hypophosphite, thereby improving the crystallization purification effect.

[0026] (2) The present invention provides a low-consumption and environmentally friendly process for purifying hypophosphite. Compared with the existing crystallization purification technology, this process can effectively remove metal ions in hypophosphite, and the reuse of the crystallization mother liquor improves the utilization rate of raw materials and saves costs.

[0027] (3) The present invention provides a low-consumption and environmentally friendly process for purifying hypophosphite. Previously, this technology was in a blank state in the chemical industry. The introduction of this process is of great significance to the capacitor industry, electronic chemical industry, biological research and pharmaceutical industry.

[0028] (4) The hypophosphite purification process does not require the use of high-energy-consuming means such as distillation for purification. The technical solution of the present invention performs purification in a conventional pharmaceutical treatment manner, which has a low-energy-consuming technical effect. DETAILED DESCRIPTION

[0029] The technical scheme of the present invention is further described below through examples. The raw materials used in the examples can be purchased from the market or prepared by conventional methods.

[0030] Example 1 (1) Industrial grade sodium hypophosphite (purity ≥ 99.5%, metal ion content see raw material-1 in Table 1) was mixed with ultrapure water in a ratio of 2:1.2, heated and stirred until completely dissolved, and the sodium hypophosphite solution was purified with a 0.2 μm HDPE microporous folded filter to remove large particle impurities in the solution.

[0031] (2) After adding 0.02‰ of sodium hexametaphosphate and 0.1‰ of trisodium ethylenediamine disuccinate as chelating agents to the sodium hypophosphite solution, the material is transported to the crystallization reactor for cooling and crystallization.

[0032] (3) The temperature in the crystallization kettle was lowered at a rate of 10°C / h until it slowly cooled to 0°C and then held there for 1 hour. The sodium hypophosphite crystals and mother liquor were discharged from the bottom of the crystallization reactor and transported to a centrifuge for washing and drying. The crystals were then dried in a vacuum drying oven at a constant temperature of 35°C and vacuum packaged for storage. The dried sodium hypophosphite had an active ingredient content of 99.9 wt%, a crystallization yield of approximately 43%, and the metal ion content was shown in Table 1, Product-1.

[0033] (4) The crystallization mother liquor was purified by passing through a primary resin column filled with Zhengguang HOSD11 and a secondary resin column filled with Zhengguang HOSD9 at a flow rate of 5 BV / h. When the flow rate of the primary resin column reached 200 BV, the resin was replaced. When the flow rate of the secondary resin column reached 350 BV, the resin was replaced. The metal content in the mother liquor after resin purification is shown in Mother Liquor-1 in Table 1.

[0034] (5) After the replaced resin is soaked in 25wt% hydrochloric acid for 24 hours, the old resin column is rinsed with 10wt% hydrochloric acid at a flow rate of 1BV / h, and finally rinsed with ultrapure water to complete the resin regeneration.

[0035] Example 2 (1) The raw materials and specific operation steps are the same as (1) in Example 1, except that the filter element is replaced with a HDPE microporous pleated filter element with a filtration accuracy of 0.1 μm. The metal content in the raw materials is shown in Raw Material-2 in Table 1.

[0036] (2) The specific operation steps are consistent with (2) in Example 1, except that the chelating agent is replaced with 0.2‰ N, N, N-tris(carboxymethyl)ethylenediamine and 0.08‰ sodium diethyldithiocarbamate.

[0037] (3) The specific operation steps are consistent with (3) in Example 1. The crystal metal ion content is shown in Product-2 in Table 1.

[0038] (4) The specific operation steps are consistent with (4) in Example 1, except that the primary resin is replaced with HiSilicon XAD-2 and the secondary resin is replaced with HiSilicon HPD400. The metal content in the mother liquor after resin purification is shown in Mother Liquor-2 in Table 1.

[0039] (5) The specific operation steps are the same as (5) in Example 1.

[0040] Comparative Example 1 (1) The raw materials and specific operation steps are the same as (1) in Example 1.

[0041] (2) The specific operation steps are the same as (2) in Example 1, except that the chelating agent is replaced with 0.2‰ disodium aminotrimethylene phosphate and 0.02‰ sodium ethylenediaminetetramethylenephosphonate.

[0042] (3) The specific operation steps are consistent with (3) in Example 1. The crystal metal ion content is shown in Product-3 in Table 1.

[0043] (4) The specific operation steps are consistent with (4) in Example 1. The metal content in the mother liquor after resin purification is shown in Mother Liquor-3 in Table 1.

[0044] (5) The specific operation steps are the same as (5) in Example 1.

[0045] Comparative Example 2 The specific operation steps of (1), (2), and (3) are consistent with those of (1), (2), and (3) in Example 1. The crystalline metal ion content is shown in Product-4 in Table 1.

[0046] (4) The specific operation steps are the same as (4) in Example 1, except that the primary resin is replaced with DuPont XAD16 and the resin filled in the secondary resin column is DuPont XAD1180.

[0047] The metal content in the mother liquor after resin purification is shown in Mother Liquor-4 in Table 1.

[0048] (5) The specific operation steps are the same as (5) in Example 1.

[0049] Comparative Example 3 (1) Industrial grade sodium hypophosphite (the same batch as in Example (1)) was mixed with sodium hypophosphite mother liquor that had been reused four times in a ratio of 1:1.4, heated and stirred until completely dissolved, and the sodium hypophosphite solution was purified using a 0.2 μm HDPE microporous folded filter to remove large particle impurities from the solution.

[0050] The specific operation steps of (2), (3), (4), and (5) are consistent with those of (2), (3), (4), and (5) in Example 1. The metal ion content of sodium hypophosphite crystals is shown in Product-5 in Table 1. The metal content in the mother liquor after resin purification is shown in Mother Liquor-5 in Table 1.

[0051] Table 1 Metal ion content in raw materials, products and mother liquor

[0052] In Table 1, the total metal content of Products 1 and 2 is less than 50 ppb, while the K, Ag, and Al content of Product 3 are all relatively high. This indicates that the chelating agents disodium aminotrimethylene phosphate and sodium ethylenediamine tetramethylenephosphonate used in Comparative Example 1 have poor selectivity for these three metal impurities, resulting in high content of some metals in the crystalline product. Chelating agents have a certain degree of selectivity when adsorbing metal ions. Therefore, it is important to select appropriate chelating agents and combine them together during use to effectively adsorb metal ions in the solution.

[0053] By comparing the crystallized products of Example 1 and Comparative Example 2, it can be seen that DuPont XAD16 and DuPont XAD1180 have poor adsorption effects on sodium hexametaphosphate and trisodium ethylenediamine disuccinate. This is because the molecular sizes of chelating agents of different molecular weights vary greatly, and the resin has a certain selectivity when adsorbing the chelating agent due to the different molecular sizes of the chelate. During the purification process of the crystallization mother liquor, it is necessary to select a macroporous adsorption resin with an appropriate pore size according to the molecular weight of the chelating agent.

[0054] When the crystallization mother liquor is reused for the fifth time, the crystallization purification effect is poor due to the high enrichment content of some metal impurities. Therefore, the number of times the crystallization mother liquor can be reused in this process is 4.

[0055] Example 3 (1) Industrial grade sodium hypophosphite (purity 95.5%, metal ion content see Table 2 Industrial Raw Materials-2) was mixed with ultrapure water in a ratio of 2:0.6, heated and stirred until completely dissolved, and the sodium hypophosphite solution was purified using a 0.5 μm HDPE microporous folded filter to remove large particle impurities in the solution.

[0056] (2) After adding 0.05‰ of nitrilotriacetic acid and 0.2‰ of disodium ethylenediaminetetraacetate as chelating agents to the sodium hypophosphite solution, the material is transported to the crystallization reactor for cooling and crystallization.

[0057] (3) The temperature in the crystallization kettle was slowly lowered to -5°C at a rate of 20°C / h and then kept at this temperature for 1 hour. The sodium hypophosphite crystals and mother liquor were discharged from the bottom of the crystallization reactor and transported to a centrifuge for washing and drying. The crystals were then dried in a vacuum drying oven at a constant temperature of 55°C and vacuum-packed for storage. The dried sodium hypophosphite had an active ingredient content of 99.9 wt%, a crystallization yield of approximately 60%, and the metal ion content of the crystals is shown in Table 2, Product-6.

[0058] (4) The crystallization mother liquor was purified by passing through a primary resin column filled with DuPont XAD-4 and a secondary resin column filled with DuPont AB-8 at a flow rate of 5 BV / h. When the flow rate of the primary resin column reached 150 BV, the resin was replaced. When the flow rate of the secondary resin column reached 280 BV, the resin was replaced. The metal content in the mother liquor after resin purification is shown in Mother Liquor-6 in Table 2.

[0059] (5) After the replaced resin is soaked in anhydrous ethanol for 24 hours, the old resin column is rinsed with anhydrous ethanol at a flow rate of 1BV / h, and finally rinsed with ultrapure water to complete the resin regeneration.

[0060] Comparative Example 4 (1) The specific operation steps are the same as (1) in Implementation Case 3, except that the filter element is changed to a 3.0 μm HDPE microporous pleated filter element.

[0061] The specific operation steps of (2), (3), (4), and (5) are consistent with those of (2), (3), (4), and (5) in Example 3. The metal ion content of sodium hypophosphite crystals is shown in Product-7 in Table 2. The metal content in the mother liquor after resin purification is shown in Mother Liquor-7 in Table 2.

[0062] Comparative Example 5 (1) The specific operation steps are the same as (1) in Example 3.

[0063] (2) The sodium hypophosphite solution is directly fed into the crystallization reactor.

[0064] (3) The specific operation steps are consistent with (3) in Example 3. The metal ion content of the crystalline product is shown in Product-8 in Table 2, and the metal ion content of the mother liquor is shown in Mother Liquor-8 in Table 2.

[0065] Table 2 Metal ion content in raw materials, products and mother liquor

[0066] After the hypophosphite is completely dissolved, some insoluble or insoluble impurities in the raw material remain suspended in the hypophosphite solution. Selecting an appropriate microfiltration membrane removes these particulate impurities. As shown in Table 2, selecting an appropriate microporous pleated filter element to remove particulate impurities from the solution can effectively reduce the metal content in the crystallized product and mother liquor. Furthermore, adding a chelating agent to the solution before crystallization to form a chelate with the metal ions in the solution prevents some metal impurities from participating in the phosphate crystallization process. This effectively reduces the content of metal ions such as Fe, Cu, Ba, and K in the product and mother liquor, facilitating the reuse of the mother liquor.

[0067] Conclusion: The purification process described in this invention utilizes a chelating agent to selectively complex some metal ions, enhancing the purification efficiency of the crystallized product. The mother liquor is purified by adsorption with a macroporous resin and then reused, improving raw material utilization. After the adsorption resin reaches saturation, desorption and regeneration restore the original adsorption capacity, enabling resin recycling, reducing application costs, resource waste, and environmental pollution. Furthermore, the hypophosphite purification technology described in this invention has a simple process, is easily scalable, and has promising market prospects.

Claims

1. A low-consumption and environmentally friendly hypophosphite purification process, characterized in that: The following steps are included S1. Mixing the hypophosphite raw material powder with ultrapure water, heating and dissolving the mixture, and then filtering out the particulate impurities using a microfiltration membrane; S2, adding an appropriate amount of chelating agent to the filtrate obtained in step S1, stirring evenly, and then transporting it to a dynamic crystallization kettle, and slowly cooling and crystallizing; S3, releasing hypophosphite crystals and mother liquor from the bottom of the crystallization reactor, separating the hypophosphite mother liquor from the crystals, and drying the hypophosphite crystals; S4. The hypophosphite mother liquor is passed through a macroporous adsorption resin to remove the chelate in the mother liquor and is used again in the crystallization process of a new batch of materials.

2. A low-consumption and environmentally friendly hypophosphite purification process according to claim 1, characterized in that: The raw material in S1 is industrial-grade hypophosphite with a purity of 95.5-99.5%; the mixing ratio of hypophosphite powder to ultrapure water is 2:0.5-1.

5.

3. A low-consumption and environmentally friendly hypophosphite purification process according to claim 1, characterized in that: The material of the microfiltration membrane described in S1 includes one of HEPE, PA, PTFE or PS.

4. A low-consumption and environmentally friendly hypophosphite purification process according to claim 1, characterized in that: The filtration accuracy of the microfiltration membrane described in S1 is one of 0.1 μm, 0.2 μm, 0.5 μm or 1.0 μm, and the filtration speed of the microfiltration membrane is 8-15 m / h.

5. A low-consumption and environmentally friendly hypophosphite purification process according to claim 1, characterized in that: The chelating agent added to the filtrate in step S2 includes two or three of trisodium ethylenediamine disuccinate, ethylenediamine disuccinic acid, nitrilotriacetic acid, sodium hexametaphosphate, tri(2-carboxyethyl)phosphine, trisodium methylglycine diacetate, sodium diethyldithiocarbamate, silver diethyldithiocarbamate, polyvinyl alcohol, N,N,N-tris(carboxymethyl)ethylenediamine, and disodium ethylenediaminetetraacetate.

6. A low-consumption and environmentally friendly hypophosphite purification process according to claim 1, characterized in that: In step S2, the hypophosphite solution is cooled in the crystallization reactor at a rate of 10-20°C / h.

7. A low-consumption and environmentally friendly hypophosphite purification process according to claim 1, characterized in that: In S3, during the crystallization process of the hypophosphite solution in the crystallization reactor, the rotation speed of the stirring blade is 70-150 rpm.

8. A low-consumption and environmentally friendly hypophosphite purification process according to claim 1, characterized in that: In said S3, the crystallization termination temperature of the hypophosphite solution in the crystallization reactor is -5-2°C.

9. A low-consumption and environmentally friendly hypophosphite purification process according to claim 1, characterized in that: The macroporous adsorption resin described in step S4 is a non-ionic macroporous adsorption resin, and the non-ionic macroporous adsorption resin includes any two or more of Zhengguang HOSD11, Zhengguang HOSD9, DuPont XAD3, DuPont XAD4, HiSilicon XAD2, HiSilicon HPD400, and HiSilicon HPD700Z.

10. A low-consumption and environmentally friendly hypophosphite purification process according to claim 9, characterized in that: The average pore size of the macroporous adsorption resin in step S4 is 6.0-25.0 nm.

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