A method for comprehensive utilization of components in 13X molecular sieve crystallization mother liquor

Abstract

This invention relates to a method for the comprehensive utilization of components from the crystallization mother liquor of 13X molecular sieve. The method uses these components to replace part of the liquid alkali in the synthesis of ferric phosphate, and utilizes non-commercially applicable micro-particle 13X molecular sieve as seed crystals for ferric phosphate preparation, thus fully utilizing the components of the 13X molecular sieve crystallization mother liquor. This invention rationally utilizes the liquid alkali component and non-commercially applicable micro-particles in the 13X molecular sieve mother liquor, saving on ferric phosphate production costs, improving the utilization rate of by-products, and simultaneously improving the morphology and tap density of the ferric phosphate product. It also achieves zero-waste production of 13X molecular sieve. The preparation method of this invention is simple to operate and can obtain high-quality ferric phosphate.

Description

Technical Field

[0001] This invention relates to a chemical process and method, and more specifically, to a method for the comprehensive utilization of the components of the mother liquor from the crystallization of 13X molecular sieves. Background Technology

[0002] Molecular sieves are typically aluminosilicate compounds with a cubic crystal lattice. They possess a uniform microporous structure with consistent pore diameter, allowing them to adsorb molecules smaller than their diameter into the pores. They generally exhibit preferential adsorption of polar and unsaturated molecules. Due to their excellent adsorption, catalytic, and ion exchange properties, molecular sieves have found wide applications. Furthermore, high demand from the oil and gas industry has further fueled the growth of the global molecular sieve market. Among them, 13X molecular sieve is a novel material whose good catalytic effect and low cost have led to its rapid market expansion in the catalyst industry. However, with increasingly stringent environmental regulations, the crystallization mother liquor of 13X molecular sieve cannot be fully recycled, forcing companies to increase environmental investment while maintaining production quality, thus increasing the production cost of 13X molecular sieves.

[0003] On the other hand, the commercial application of 13X molecular sieves requires large molecular sieve particles to achieve a relatively high packing density (e.g., a packing density greater than 0.65 g / ml, preferably greater than 0.70 g / ml) to meet the needs of industrial applications such as adsorption equipment. This high packing density necessitates the screening of large 13X molecular sieve particles. For example, 13X molecular sieve particles with commercial potential in gas adsorption equipment typically have a D90 particle size greater than 3 micrometers, and preferably, the 13X molecular sieve particle composition should be greater than 4 micrometers to achieve an effective high packing density. This results in the small-crystal-size 13X molecular sieves obtained in the 13X molecular sieve preparation process losing their commercial application value in gas adsorption and other applications. Consequently, the small-crystal-size molecular sieves cannot be effectively utilized in the 13X molecular sieve manufacturing process, reducing the application efficiency of 13X molecular sieves.

[0004] On the other hand, in the rapidly developing new energy field in recent years, lithium-ion batteries have attracted widespread attention due to their advantages such as long cycle life, high output voltage, high energy density, stable discharge, and no memory effect, and have been applied in mobile phones, laptops, electric vehicles, and other fields. The cathode material is a crucial component of lithium-ion batteries. Currently, the mainstream cathode materials for lithium-ion batteries include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium manganese oxide, and lithium iron phosphate. Among them, lithium iron phosphate is considered one of the most promising lithium-ion cathode materials due to its low price, good thermal stability, excellent charge-discharge cycle performance, and environmental friendliness.

[0005] Driven by the high demand for lithium iron phosphate from downstream industries such as new energy vehicles and energy storage, iron phosphate, as a precursor to lithium iron phosphate, has also attracted widespread attention. However, at the beginning of 2023, the domestic iron phosphate market experienced price fluctuations due to factors such as the gradual commissioning of new production capacity and holidays. Therefore, reducing the cost of iron phosphate has become an urgent problem for enterprises. At the same time, it is still difficult to effectively control the particle size, density, and electrical properties of iron phosphate at low cost.

[0006] Therefore, there are shortcomings in the X13 molecular sieve preparation process, as well as issues that need to be addressed regarding the quality and manufacturing cost of iron phosphate products. Summary of the Invention

[0007] This invention improves upon one or more of the above-mentioned needs and deficiencies.

[0008] The first aspect of the present invention provides a method for comprehensive utilization of the components of 13X molecular sieve crystallization mother liquor, the method comprising the following steps:

[0009] Step a): Prepare a mixed gel using sodium silicate solution, sodium aluminate solution, sodium hydroxide solution, and purified water;

[0010] Step b): The mixed gel formed in step a) is matured in a crystallization kettle. The maturity temperature is controlled at 50°C to 80°C and the maturity time is 4-12 hours to obtain matured material.

[0011] Step c): The matured material obtained in step b) is crystallized in a crystallization kettle, with the pressure controlled at 1.0 to 2.0 MPa, the crystallization temperature controlled at 100-150℃, and the crystallization time at 9 to 24 hours, to obtain a crystallized mixture;

[0012] Step d): The crystallization mixture is filtered using a filter screen with a pore size of 1.0-2.0 micrometers. The product on the filter screen is large-particle 13X molecular sieve, and the product below the filter screen is the 13X molecular sieve mother liquor component, which includes sodium hydroxide solution and micro-molecular sieve particles; and wherein,

[0013] The method includes applying a molecular sieve mother liquor component to the synthesis of ferric phosphate, wherein the sodium hydroxide in the molecular sieve mother liquor component is used as a liquid alkali feedstock in the ferric phosphate sintering process, and / or the micro molecular sieve particles are used to prepare ferric phosphate seed particles.

[0014] In the crystallization process of 13X molecular sieve, sodium silicate raw material with a modulus of 2.0-3.0 is preferred. The molar ratio of sodium silicate, sodium aluminate and liquid alkali (NaOH with a mass concentration of 20-30wt%) is selected as (1-3):(1-5):(5-15) to obtain a mixed solution. Pure water accounting for 1-10 times the total mass of the mixed solution can also be added to the mixed solution.

[0015] In an optional embodiment, the synthesis and preparation of iron phosphate includes the following steps: Step 1): Preparation of iron phosphate seed crystals: A 0.5 mol / L to 2.5 mol / L ferrous sulfate solution is mixed with a 40%-75% phosphoric acid solution, and purified water is added to make the Fe ion concentration in the solution 0.2 mol / L to 2 mol / L and the phosphorus element molar concentration 0.2 mol / L to 1.5 mol / L; the solution is stirred in a hot water bath (e.g., 50-70℃) to dissolve the raw materials and obtain a seed crystal solution; 1 to 5 kg of the seed crystal solution is placed in a reaction vessel, and 1-10 g of the aforementioned differential... The sieve particles serve as the seed crystal guide source. Under conditions of a water bath temperature of 50-70℃, 0.5-5 kg ​​of hydrogen peroxide with a mass concentration of 15-35% is added with stirring, allowing the oxidation reaction to continue for 15 to 90 minutes. Subsequently, a sodium hydroxide solution with a mass concentration of 5-20 wt% is added to adjust the pH to 1.0-3.0, and the reaction is carried out at the water bath temperature. After the reaction, the obtained crude seed crystals are washed and filtered. A phosphoric acid solution with a mass concentration of 20%-30% is added at a mass ratio of 1:(0.5-1.5) to the filtered crude seed crystals for aging reaction. The mixture is then filtered to obtain iron phosphate seed crystals.

[0016] Step 2): Weigh 500-2000 ml of the sodium hydroxide solution from step d). Optionally, add 1-10 g of calcium oxide powder, stir and mix to remove impurities from the sodium hydroxide solution, and filter (Ca element is also removed); obtain the filtered mother liquor; take 60-80% phosphoric acid, the filtered mother liquor, and 15-30 wt% sodium hydroxide solution and mix them in a mass ratio of (1-2):(1-5):(1-5) to obtain a mixed solution; add 0.5-1.5 kg of calcium hydroxide powder per kg of mixed solution. Hydrogen peroxide with a concentration of 15%-30% is mixed evenly, and ferric phosphate seed crystals obtained in step 1) are added to the mixture at a mass ratio of 1:(1-2) of the above hydrogen peroxide mixture to 1-2 mol / L ferrous sulfate solution. The mixture is reacted for 1 to 3 hours, and then filtered and washed with water to obtain the raw material to be sintered. The raw material to be sintered is preheated at 100℃-150℃ for 1 to 3 hours and calcined at 500-650℃ for 3 to 12 hours to obtain the ferric phosphate product.

[0017] In an optional technical solution, the iron phosphate product obtained after step 2) is iron phosphate sintered particles. The iron phosphate sintered particles are spherical or near-spherical in shape, and the particle size of the iron phosphate sintered particles is 4-10 μm. Preferably, the particle size of the iron phosphate sintered particles is 5 μm to 8 μm, and more preferably, the particle size of the iron phosphate sintered particles is 4 μm to 6 μm.

[0018] In a preferred embodiment, the iron phosphate seed crystals prepared in step 1) are coated with iron phosphate material to encapsulate the micro molecular sieve particles, wherein the diameter of the micro molecular sieve particles is preferably 1.2 μm to 2.0 μm, more preferably 1.5 μm to 1.8 μm.

[0019] In a preferred embodiment, step d) uses a filter screen with a pore size of 1.2-2.0 μm, more preferably 1.5 μm-1.8 μm.

[0020] The inventors discovered that by screening out the smaller micro-molecular sieve particles in the 13X molecular sieve crystallization process that cannot be used in gas adsorption equipment, and effectively adding them as a small proportion of by-products to the phosphoric acid slurry and sintering process, the performance of the sintered phosphoric acid particles can be effectively improved. At the same time, the by-products of 13X molecular sieves are also effectively utilized, and the highly alkaline molecular sieve filtration mother liquor is also effectively utilized.

[0021] In a second aspect of the invention, from the perspective of new energy material preparation, the invention also provides a method for producing iron phosphate particles using 13X molecular sieve crystallization mother liquor components, the method comprising the following steps:

[0022] Step 1): Preparation of iron phosphate seed crystals: Mix a 0.5 mol / L to 2.5 mol / L ferrous sulfate solution with a 40%-75% phosphoric acid solution, add purified water to achieve a Fe ion concentration of 0.2 mol / L to 2 mol / L and a phosphorus molar concentration of 0.2 mol / L to 1.5 mol / L. Stir in a hot water bath to dissolve the raw materials and obtain a seed crystal solution. Place 1 to 5 kg of the seed crystal solution into a reaction vessel, add 1-10 g of micro-molecular sieve particles from the 13X molecular sieve crystallization mother liquor as a seed crystal guiding source; maintain the water bath temperature at 50°C. At 70℃, 0.5-5 kg ​​of hydrogen peroxide with a mass concentration of 15-35% is added under stirring, allowing the oxidation reaction to continue for 15 to 90 minutes. Afterward, a sodium hydroxide solution with a mass concentration of 5-20 wt% is added to adjust the pH value (typically to 1.0-3.0 or 2.0-4.0), and the reaction is carried out in a water bath at 50-70℃. The resulting crude seed crystals are washed and filtered. A phosphoric acid solution with a mass concentration of 20%-30% is added at a mass ratio of 1:(0.5-1.5) to the filtered crude seed crystals for aging. The mixture is then filtered to obtain iron phosphate seed crystals.

[0023] Step 2): Weigh 500-2000 ml of sodium hydroxide solution from the 13X molecular sieve crystallization mother liquor, filter to remove impurities from the sodium hydroxide solution, and obtain the filtered mother liquor; take 60-80% phosphoric acid, the filtered mother liquor, and 15-30 wt% sodium hydroxide solution and mix them in a mass ratio of (1-2):(1-5):(1-5) to obtain a mixed solution; add 15%-30% hydrogen peroxide solution at a ratio of 0.5-1.5 kg per kg of the mixed solution. Water is mixed evenly, and 1-5 wt% of the ferric phosphate seed crystals obtained in step 1) are added to the mixture to obtain a hydrogen peroxide mixture. Ferrous sulfate solution is added to the hydrogen peroxide mixture at a mass ratio of 1:1 to 1 mol / L to 2 mol / L ferrous sulfate solution. The mixture is reacted for 1 to 3 hours, followed by pressure filtration and water washing to obtain the raw material to be sintered. The raw material to be sintered is pre-sintered at 100℃-150℃ for 1-3 hours and calcined at 500-650℃ for 3 to 12 hours to obtain the ferric phosphate product.

[0024] In an optional technical solution, the 13X molecular sieve crystallization mother liquor is derived from the following steps:

[0025] Step a): Prepare a mixed gel using sodium silicate solution, sodium aluminate solution, sodium hydroxide solution, and purified water;

[0026] Optionally, in the crystallization process of 13X molecular sieve, the preferred sodium silicate raw material is sodium silicate with a modulus of 2.0-3.0. The molar ratio of sodium silicate, sodium aluminate and liquid alkali (NaOH with a mass concentration of 20-30wt%) is selected as (1-3):(1-5):(5-15) to obtain a mixed solution. Pure water accounting for 1-10 times the total mass of the mixed solution can also be added to the mixed solution.

[0027] Step b): The mixed gel formed in step a) is matured in a crystallization kettle. The maturity temperature is controlled at 50°C to 80°C and the maturity time is 4-12 hours to obtain matured material.

[0028] Step c): The matured material obtained in step b) is crystallized in a crystallization kettle, with the pressure controlled at 1.0 MPa to 2.0 MPa, the crystallization temperature controlled at 100-150℃, and the crystallization time at 9 to 24 hours, to obtain a crystallized mixture;

[0029] Step d): The crystallization mixture is filtered, wherein a filter screen with a pore size of 1.0μm-2.0μm is selected. The product on the filter screen is large-particle 13X molecular sieve, and the product below the filter screen is 13X molecular sieve mother liquor. The molecular sieve mother liquor contains the sodium hydroxide solution and the micro molecular sieve particles.

[0030] In the optional technical solutions, the method satisfies one or more of the following:

[0031] In the iron phosphate seed crystals, the iron phosphate material encapsulates the micro molecular sieve particles, the diameter of which is preferably 1.2 to 2.0 micrometers, more preferably 1.5 to 1.8 micrometers;

[0032] The obtained iron phosphate product is iron phosphate sintered particles. The morphology of the iron phosphate sintered particles is spherical or near-spherical. The particle size of the iron phosphate sintered particles is 4μm-10μm. Preferably, the particle size of the iron phosphate sintered particles is 5μm to 8μm. More preferably, the particle size of the iron phosphate sintered particles is 4μm to 6μm.

[0033] In step d), a filter screen with a pore size of 1.2μm-2.0μm is selected, more preferably 1.5μm to 1.8μm.

[0034] It should be noted that the technical features of the technical solutions provided by this invention can be superimposed on each other or implemented independently. Furthermore, each step and process of the technical solutions of this invention may include the stated steps and processes, as well as other auxiliary processes. In optional technical solutions, the process may be performed solely by the stated processes, without including other additional steps and processes.

[0035] According to the technical solution of the present invention, the small particles of residual 13X molecular sieve, which are usually unusable byproducts in the preparation of 13X molecular sieves, are effectively utilized. Due to the porous nature of the small particles themselves, they may form nucleation sites that are conducive to formation, thereby forming uniform iron phosphate seed crystals. When these seed crystals are applied to the sintering and growth of iron phosphate particles, sintering and growth can continue on the basis of uniform seed crystals, thereby obtaining uniform spherical or near-spherical iron phosphate particles with controllable size.

[0036] Meanwhile, in the preparation process of 13X molecular sieve, the inventors further fully utilized the residual filtration mother liquor from the alkaline molecular sieve, directly using the mother liquor after molecular sieve preparation (with an effective sodium hydroxide content of up to 10 wt%) for the alkali requirement in the ferric phosphate preparation process, which can significantly reduce the consumption of liquid alkali in the ferric phosphate process. In small-scale and pilot-scale tests, the consumption of liquid alkali in the ferric phosphate process can be reduced by 12%-15%, effectively recycling the environmentally harmful waste liquid from the molecular sieve manufacturing step, while reducing the raw material cost in the ferric phosphate preparation process. The various processes and advantages of this invention will be further illustrated and explained in the following figures and specific embodiments. Attached Figure Description

[0037] The accompanying drawings are provided to further understand the technical solutions of this disclosure and constitute a part of the specification. They are used together with the specific embodiments of this application to explain the technical solutions of this disclosure and do not constitute a limitation on the technical solutions of this disclosure.

[0038] Figure 1 The X-ray diffraction pattern is that of the 13X molecular sieve prepared in Example 1 of the present invention;

[0039] Figure 2 The X-ray diffraction pattern is the sintered iron phosphate powder particle prepared in Example 2 of this invention.

[0040] Figure 3 These are SEM (scanning electron microscope) images of the sintered iron phosphate particles from Example 2 of this invention.

[0041] Figure 4 This is the SEM (scanning electron microscope) test pattern of the iron phosphate seed crystals prepared in step 1) of Example 2 of the present invention;

[0042] Figure 5 This is a SEM (scanning electron microscope) image of the sintered iron phosphate product prepared in Comparative Example 1 of this invention.

[0043] Figure 6 This is a SEM (scanning electron microscope) image of the sintered iron phosphate product prepared in Comparative Example 2 of this invention. Detailed Implementation

[0044] The invention is described in more detail below to aid in understanding it.

[0045] Before describing the specific implementation scheme, it should be noted that those skilled in the art can select appropriate raw materials based on the teachings and guidance of this disclosure, conduct relevant tests using relevant testing equipment, and obtain corresponding results. For raw materials for which specific manufacturers or methods are not specified, those skilled in the art can select raw materials that meet the corresponding requirements as reaction starting materials based on the disclosure and needs of this specification. The reaction raw materials between compounds or components in the process section are derived from the initial products synthesized in the preceding steps of this invention, which is also understandable based on this disclosure.

[0046] The X-ray diffraction equipment of this invention is the Rigaku D / MAX-25500 X-ray powder diffractometer from Japan.

[0047] The scanning electron microscope tests of this invention were performed using an S-4800 scanning electron microscope from Hitachi.

[0048] Although not the only major test result of this invention, it is noted that the relative crystallinity of the typical molecular sieves of this invention is determined according to the RIPP 146-90 standard method (see "Analytical Methods for Petrochemical Products (RIPP Test Methods)", Science Press, 1990: 412-415), wherein the 13X molecular sieve provided by Shanghai Hushi Pharmaceutical Technology Co., Ltd., with commercially available CAS number 63231-69-6, is assumed to have a crystallinity of 100% for testing and comparison.

[0049] Example 1 (E1)

[0050] This embodiment relates to the preparation of 13X molecular sieve and the components of the prepared molecular sieve mother liquor.

[0051] Step 1): Prepare and mix molecular sieve raw materials, in which sodium silicate (modulus 2.5), sodium aluminate, and liquid alkali (NaOH with a mass concentration of 30wt%) are added to the gelation tank in a molar ratio of 3:1:10, and then pure water is added in an amount of about 3 times the total mass of the three. The temperature in the gelation tank is controlled at 40-45℃, and the mixture is stirred for 60 minutes to form a mixed gel.

[0052] Step 2): Add the mixed gel formed in step 1) into the crystallization kettle for maturation. The maturation temperature is controlled at 70℃ and the maturation time is 5-8 hours to obtain the maturated material.

[0053] Step 3): Crystallize the aging material under the in-situ conditions of Step 2). The temperature inside the crystallization vessel is controlled at 110℃. The crystallization vessel is sealed and pressurized, with the pressure controlled at 1.5-2 MPa. The crystallization time is 12-18 hours to obtain a crystallized mixture.

[0054] Step 4): Filter the crystallization mixture using a 1.5-micron (μm) pore size filter. The product on the filter screen is large-particle 13X molecular sieve, and the product below the filter screen is the 13X molecular sieve mother liquor component. The large-particle 13X molecular sieve is sent to subsequent steps to prepare the finished 13X molecular sieve product, while the 13X molecular sieve mother liquor component becomes a by-product, mainly composed of sodium hydroxide and small-particle (particle size less than 1.5 microns) molecular sieve particles.

[0055] The product prepared according to Example 1 contains large-particle 13X molecular sieve (its X-ray diffraction pattern is shown in [reference]). Figure 1 Due to its particulate properties, the bulk density can reach 0.68-0.70 g / ml, and the relative crystallinity can reach 97%, making it effective for use in gas adsorption equipment or components. Typically, the chemical composition of 13X molecular sieve is considered to be Na2O·Al2O3·(2.5±0.3)SiO2·(5-7)H2O. The remaining mother liquor, sodium hydroxide component, and small-particle (particle size less than 1.5 micrometers) molecular sieve particles are reserved as additives and auxiliary components in the iron phosphate preparation process, which will be described in detail below.

[0056] Example 2 (E2)

[0057] In this embodiment, the preparation process of the ferric phosphate product will be described, wherein the process utilizes the 13X molecular sieve mother liquor component obtained in Example 1 as a by-product, thereby improving the performance of the ferric phosphate product and realizing the comprehensive utilization of the 13X molecular sieve by-product.

[0058] Step 1) Preparation of Ferric Phosphate Seed Crystals: Ferrous sulfate was selected as the iron source for the seed crystals, and phosphoric acid as the phosphorus source. A 2 mol / L ferrous sulfate solution (a small amount of dilute hydrochloric acid can be mixed into the ferrous sulfate solution to prevent premature precipitation of ferrous sulfate) was mixed with a 70% phosphoric acid solution, and purified water was added to make the Fe and P molar concentrations in the solution 1 mol / L each. The mixture was stirred in a hot water bath at approximately 70 degrees Celsius to dissolve the raw materials and obtain a seed crystal solution. 5 kg of the seed crystal solution was placed in a reaction vessel, and 2 g of 13X molecular sieve particles (particle size less than 1.5 micrometers) obtained in Example 1 were added as seed crystal guiding sources. Next, under the condition of maintaining a water bath temperature of 60 degrees Celsius, 1 kg of 25% hydrogen peroxide was added with stirring, allowing the oxidation reaction to continue for 30 minutes. Subsequently, a 15 wt% sodium hydroxide solution was added to adjust the pH value (typically, to 2.0-4.0), and the reaction was continued at the water bath temperature for 1 hour. The obtained crude seed crystal product was then washed and filtered with pure water. A 30% phosphoric acid solution was added to the filtered crude seed crystal product at a mass ratio of 1:1 to phosphoric acid for aging reaction. The aging reaction was carried out at a temperature of 50℃ to 60℃ for 4 to 5 hours. After filtration, iron phosphate seed crystals (the main component of which is iron phosphate dihydrate) were obtained.

[0059] Step 2) Weigh 1000 ml of the 13X molecular sieve mother liquor obtained in Example 1 (the effective sodium hydroxide content was determined to be 12 wt%, hereinafter referred to as "alkali concentration") and add it to a beaker. While stirring, add 5 g of calcium oxide powder and stir at 95°C for 2 hours to remove impurities. After filtration, determine the alkali concentration of the filtrate to obtain a filtered mother liquor with an alkali concentration of 14.5 wt%. Take 80% concentrated phosphoric acid, the above filtered mother liquor, and 30 wt% sodium hydroxide solution and mix them at a mass ratio of 1:2:2 to obtain a mixed solution. While stirring, add 30% hydrogen peroxide at a ratio of 0.8 kg per kg of the mixed solution, mix evenly, and add 2 wt% of the iron phosphate seed crystals obtained in Step 1) to obtain a hydrogen peroxide mixture. The hydrogen peroxide mixture and ferrous sulfate solution (2 mol / L) were added to the ferrous sulfate solution in a 1:1 mass ratio, and the reaction was carried out for 1.5 hours. After that, the mixture was filtered by pressure and washed with water until the conductivity was 200-300 μs / cm. Then, the raw material to be sintered was preheated at 100°C for 2 hours and calcined at 660°C for 5 hours to obtain the ferric phosphate product.

[0060] X-ray diffraction analysis was performed on the iron phosphate product prepared in step 2), and the results are shown in the figure. Figure 2The high-intensity diffraction characteristic peaks observed at approximately 19.0°, 20.5°, 24.5°, and 32.1° at 2θ are consistent with the characteristic peaks of iron phosphate crystals, indicating that the method prepared a highly crystalline iron phosphate crystal product. The morphology of the prepared iron phosphate product was characterized, yielding… Figure 3 The results are shown.

[0061] Meanwhile, in order to test and discover the effect of the use of specific seed crystals in the embodiments of the present invention on the synthesis effect of iron phosphate, the iron phosphate seed crystals obtained in step 1) of Example 1 were subjected to SEM scanning electron microscopy, and the results are as follows. Figure 4 As shown.

[0062] The inventor does not wish to be bound by any theory, but hopes to combine... Figure 3 and Figure 4 The design concept and experimental results of this invention are discussed to some extent. In conjunction with... Figure 3 and Figure 2 The X-ray diffraction results show that the embodiments of the present invention have prepared spherical (or near-spherical) sintered iron phosphate particles with a uniform appearance and structure, and the particles are relatively uniformly maintained in a particle size of 5-8 micrometers. The uniform particles make it possible to obtain iron phosphate products with high tap density, which makes the products potentially applicable to the preparation of ferroelectric materials or new energy electrode active materials.

[0063] One hypothesis of the inventors is that the uniform iron phosphate particles in this experiment may have originated from uniform iron phosphate seed crystals. To this end, the inventors performed SEM analysis on the iron phosphate seed crystals prepared in step 1), and the results are as follows... Figure 4 As shown. From Figure 4 It can be seen that utilizing the small, typically unusable 13X molecular sieve residue particles (typically less than 1.5 micrometers in diameter) from the byproducts of 13X molecular sieve preparation, due to the porous nature of these small particles, can potentially form nucleation sites, thus forming uniform iron phosphate seed crystals. When these seed crystals are applied to the sintering and growth of iron phosphate particles in step 2), they advantageously contribute to the formation of uniform seed crystals (from... Figure 4 It can be seen that the seed crystals continue to grow by sintering on the basis of approximately (the seed crystal size is approximately 0.5), thus obtaining uniform spherical or near-spherical iron phosphate particles with controllable size.

[0064] Meanwhile, in the inventor's embodiment, the proportion of molecular sieve particles added during the iron phosphate seed preparation process is very low, having little impact on the impurities in the final iron phosphate product. Furthermore, the remaining tiny molecular sieve particles are encapsulated by the iron phosphate components grown twice, and are only likely to reside within the iron phosphate particles, thus having no significant negative impact on subsequent iron phosphate lithium battery material products. In the final iron phosphate product impurity test in step 2) of this invention, the actual content of sodium, aluminum, and silicon is less than 0.01 wt%, enabling the iron phosphate material to be further industrially applied according to the process of this invention.

[0065] Meanwhile, the inventors further utilized the residual filtration mother liquor from the alkaline molecular sieve in the preparation process of 13X molecular sieve. The mother liquor after molecular sieve preparation (with an effective sodium hydroxide content of up to 10 wt%) was directly used for the alkali requirement in the ferric phosphate preparation process, significantly reducing the consumption of liquid alkali in the ferric phosphate process. In small-scale and pilot-scale tests, the consumption of liquid alkali in the ferric phosphate process can be reduced by 12%-15%, effectively recycling the environmentally harmful waste liquid from the molecular sieve manufacturing step, while simultaneously reducing the raw material costs in the ferric phosphate preparation process.

[0066] Example 3 (E3)

[0067] This embodiment follows the same process as Example 2, except that some process parameters, raw material ratios, and preparation temperature were adjusted to prepare lithium iron phosphate particles under similar conditions.

[0068] Step 1) Preparation of Ferric Phosphate Seed Crystals: Ferrous sulfate was selected as the iron source for the seed crystals, and phosphoric acid as the phosphorus source. A 1.5 mol / L ferrous sulfate solution was mixed with a 60% phosphoric acid solution, and purified water was added to make the Fe and P molar concentrations in the solution 0.8 mol / L each. The mixture was stirred in a hot water bath at approximately 60°C to dissolve the raw materials and obtain a seed crystal solution. 10 kg of the seed crystal solution was placed in a reaction vessel, and 1.5 g of 13X molecular sieve particles (particle size less than 1.5 μm) obtained in Example 1 were added as seed guiding sources. Next, under the condition of maintaining a water bath temperature of 55°C, 1 kg of 25% hydrogen peroxide was added with stirring, allowing the oxidation reaction to continue for 45 minutes. Subsequently, a 10 wt% sodium hydroxide solution was added to adjust the pH value to 1.0-3.0, and the reaction was carried out at the water bath temperature for 1 hour. After the reaction, the obtained crude seed crystal product was washed with pure water and filtered. A 25% phosphoric acid solution was added to the filtered crude seed crystal product and phosphoric acid at a mass ratio of 1:1 for aging reaction. The aging reaction was carried out at a temperature of 50℃ to 60℃ for 5 to 7 hours. After filtration, iron phosphate seed crystals (the main component is iron phosphate dihydrate) were obtained.

[0069] Step 2) Weigh 1000 ml of the 13X molecular sieve mother liquor obtained in Example 1 (the effective sodium hydroxide content was determined to be 5.5 wt%, hereinafter referred to as "alkali concentration") and add it to a beaker. While stirring, add 2 g of calcium oxide powder and stir at 95°C for 2 hours to remove impurities. After filtration, determine the alkali concentration of the filtrate to obtain a filtered mother liquor with an alkali concentration of 6.0 wt%. Take 70% concentrated phosphoric acid, the above filtered mother liquor, and 20 wt% sodium hydroxide solution and mix them at a mass ratio of 1:5:5 to obtain a mixed solution. Add 30% hydrogen peroxide at a ratio of 0.7 kg per kg of the mixed solution, mix evenly, and add 1.5 wt% of the iron phosphate seed crystals obtained in Step 1) to obtain a hydrogen peroxide mixture. The hydrogen peroxide mixture and ferrous sulfate solution (2 mol / L) were added in a 1:1 mass ratio and reacted for 1.5 hours. After that, the mixture was filtered and washed with water until the conductivity was 200-300 μs / cm. The raw material to be sintered was then preheated at 120°C for 2 hours and calcined at 600°C for 6 hours to obtain the ferric phosphate product.

[0070] Comparative Example 1 (C1)

[0071] Comparative Example 1 performed the same step 2 (iron phosphate product) as in Example 2 (E2), except that the molecular sieve particles in the 13X molecular sieve mother liquor component of Example 1 were not used as seed particles in Comparative Example 1.

[0072] Specifically, in step 1) of Comparative Example 1 tested by the inventors, ferrous sulfate was selected as the iron source for the seed crystals, and phosphoric acid was selected as the phosphorus source. A 2 mol / L ferrous sulfate solution was mixed with a 70% phosphoric acid solution, and purified water was added to make the Fe and P molar concentrations in the solution 1 mol / L each. The mixture was stirred in a hot water bath at approximately 70 degrees Celsius to dissolve the raw materials and obtain a seed crystal solution. 5 kg of the seed crystal solution was placed in a reaction vessel, and under the condition of maintaining a water bath temperature of 60 degrees Celsius, 1 kg of 25% hydrogen peroxide was added with stirring, allowing the oxidation reaction to continue for 30 minutes. Subsequently, a 15 wt% sodium hydroxide solution was added to adjust the pH value to 1.0-3.0, and the reaction was carried out at a water bath temperature for 1 hour. After the reaction, the obtained crude seed crystal product was washed with pure water and filtered. A 30% phosphoric acid solution was added to the filtered crude seed crystal product at a mass ratio of 1:1 to phosphoric acid for aging reaction. The aging reaction was carried out at a temperature of 50℃ to 60℃ for 4 to 5 hours. After filtration, iron phosphate seed crystals (the main component is iron phosphate dihydrate) were obtained.

[0073] Following step 1) of Comparative Example 1), the same ferric phosphate sintering steps as in step 2) of Example 2 were performed, resulting in a sintered ferric phosphate product. The inventors also performed SEM testing on the product from Comparative Example 1, and the results are as follows: Figure 5 As shown. From Figure 5 The test results show that the iron phosphate particles tend to adhere to each other and grow further, with the particle shape becoming irregular. The largest dimension exceeds 10 micrometers, and the boundaries between particles are not clearly defined. The inventors believe this may be related to the irregularity of iron phosphate seed formation. Without a porous micro-molecular sieve structure as a strong growth site for iron phosphate seeds, the formation of the seeds may be affected. The irregularity or inconsistent size of the seeds leads to inconsistent final iron phosphate particle formation, with particles tending to grow further and agglomerate.

[0074] The inventors tested the tap density of the iron phosphate particles prepared in Example 2 and Comparative Example 1. The results showed that the tap density of the iron phosphate particles in Example 2 reached 1.25 g / cm³. 3 The tap density of the iron phosphate particles prepared in Comparative Example 1 was 0.99 g / cm³. 3 .

[0075] Comparative Example 2 (C2)

[0076] Comparative Example 2, compared to Examples 2 and 1, did not employ the preparation and addition of seed crystals, nor did it utilize the remaining mother liquor from the molecular sieve. However, it employed a similar method to Example 2 for preparing sintered iron phosphate material. Specifically, 80% concentrated phosphoric acid and 30wt% sodium hydroxide solution were directly mixed at a mass ratio of 1:3 to obtain a mixture. 30% hydrogen peroxide was added at a ratio of 0.8 kg per kg of the mixture, and the mixture was thoroughly mixed to obtain a hydrogen peroxide mixture. Ferrous sulfate solution (2 mol / L) was added to the hydrogen peroxide mixture at a mass ratio of 1:1, and the reaction was allowed to proceed for 1.5 hours. Afterward, the mixture was pressure filtered, washed with water until the conductivity reached 200-300 μS / cm, and then the resulting raw material to be sintered was preheated at 100°C for 2 hours and calcined at 660°C for 5 hours to obtain the iron phosphate product.

[0077] The inventors performed SEM tests on the iron phosphate particles of Comparative Example 2 (e.g., Figure 6 As shown in the figure, the test results indicate that in the sintered iron phosphate material without seed crystals, the particles exhibit irregular shapes, some appearing as flakes, others as granules or elongated strips. The boundaries between individual particles are not clearly defined, and the effective size of a single calculable particle is much larger than 10 micrometers. Furthermore, in the tap density test of iron phosphate, Comparative Example 2 only obtained 0.7 g / cm³. 3Or even lower density, which is not conducive to the subsequent application of iron phosphate materials in new energy materials and other fields.

[0078] The method for comprehensive utilization of the 13X molecular sieve crystallization mother liquor components according to the present invention fully utilizes the microparticles of 13X molecular sieve that cannot be used in industrial applications, achieving efficient reuse in the ferric phosphate production process, and improving the control over the surface morphology and density of ferric phosphate particles. Simultaneously, considering the large amount of alkaline wastewater generated in the industrial application of 13X molecular sieve, the method effectively utilizes the effective sodium hydroxide concentration in the alkaline wastewater, combined with the microparticles of 13X molecular sieve, effectively improving the production efficiency of ferric phosphate sintered granular materials and reducing raw material application costs.

[0079] While this disclosure includes specific embodiments, it will be apparent to those skilled in the art that various substitutions or changes in form and detail can be made to these embodiments without departing from the inventive spirit and scope of the claims and their equivalents. The embodiments described herein should be considered illustrative only and not for limiting purposes. The description of features and aspects in each embodiment is considered applicable to similar features and aspects in other embodiments. Therefore, the scope of this disclosure should not be limited by the specific descriptions but by the claims, and all variations within the scope of the claims and their equivalents are to be interpreted as included within the scope of this disclosure.

Claims

1. A method for the comprehensive utilization of components in the mother liquor of 13X molecular sieve crystallization, characterized in that the method... Includes the following steps: Step a): Prepare a mixture using sodium silicate solution, sodium aluminate solution, sodium hydroxide solution, and purified water. Gel; Step b): The mixed gel formed in step a) is matured in a crystallization vessel at a specific temperature. The temperature is controlled between 50℃ and 80℃, and the maturation time is 4-12 hours to obtain the maturated material; Step c): The matured material obtained in step b) is crystallized in a crystallization kettle, with the pressure controlled at... A pressure of 1.0 to 2.0 MPa is applied, the crystallization temperature is controlled at 100-150℃, and the crystallization time is 9 to 24 hours to obtain crystals. Mixture; Step d): Filter the crystallization mixture using a filter mesh with a pore size of 1.0-1.5 micrometers. A micron-sized filter screen produces a product with large 13X molecular sieve particles on the screen and a product with 13X molecular sieve particles underneath. The molecular sieve mother liquor component comprises a sodium hydroxide solution and particles with a diameter of 1.2 to 1.5 mm. 13X micro molecular sieve particles between micrometers in size; The method includes applying a molecular sieve mother liquor component to the synthesis of ferric phosphate, wherein the ferric phosphate... The synthesis preparation includes the following steps: Step 1): Preparation of iron phosphate seed crystals: Use a 0.5 mol / L to 2.5 mol / L ferrous sulfate solution. Mix with a 40%-75% phosphoric acid solution, add purified water, and the concentration of Fe ions in the solution will increase. The concentration of phosphorus in hot water ranges from 0.2 mol / L to 2 mol / L. Stirring is performed in a bath environment to dissolve the raw materials and obtain a seed crystal solution; 1 to 5 kg of the seed crystal solution is placed into the reaction vessel. Add 1-10 grams of the micro molecular sieve particles as a seed source; maintain a water bath temperature of 50-70℃. Under certain conditions, 0.5-5 kg ​​of hydrogen peroxide with a mass concentration of 15-35% is added under stirring to facilitate the reaction. Continue for 15 to 90 minutes; thereafter, add a 5-20 wt% sodium hydroxide solution. Adjust the pH value and carry out the reaction at a water bath temperature; after the reaction, wash and filter the obtained crude seed crystals, and then... Add phosphoric acid at a mass ratio of 1:(0.5-1.5) to the filtered crude seed crystal product and phosphoric acid, using a phosphoric acid concentration of 20%-30%. The acid solution was subjected to a aging reaction, and then filtered to obtain iron phosphate seed crystals. Step 2): Weigh 500-2000 ml of the sodium hydroxide solution from step d), and add 1-10 g of... Calcium oxide powder is stirred and mixed to remove impurities from the sodium hydroxide solution, then filtered to obtain the filtered mother liquor. Liquid; take phosphoric acid with a mass concentration of 60-80%, the filtered mother liquor, and a solution with a mass concentration of 15-30 wt%. Sodium hydroxide solution was mixed and stirred at a mass ratio of (1-2):(1-5):(1-5) to obtain a mixed solution; according to per kg Add 0.5-1.5 kg of the mixture to hydrogen peroxide with a mass concentration of 15%-30%, mix thoroughly, and then add... The iron phosphate seed crystals obtained in step 1) are added in a mixture of 1-5 wt% to obtain a hydrogen peroxide mixture; according to... Add ferrous sulfate according to the mass ratio of hydrogen peroxide mixture to 1-2 mol / L ferrous sulfate solution of 1:

1. The solution is reacted for 1 to 3 hours, followed by pressure filtration and water washing to obtain the raw material to be sintered; the obtained raw material to be sintered is then... The raw materials are preheated at 100℃-150℃ for 1-3 hours and calcined at 500-650℃ for 3 to 12 hours. Obtain ferric phosphate product; Furthermore, the sodium hydroxide in the molecular sieve mother liquor component is used in the liquid phase of the ferric phosphate sintering process. Alkali raw materials are used, and the micro molecular sieve particles are used to prepare ferric phosphate seed particles, thereby improving the particle size distribution of ferric phosphate. The ability to control the surface morphology of particles and the density of iron phosphate particles.

2. The method according to claim 1, characterized in that, The preparation obtained after step 2) is The ferric phosphate product is sintered ferric phosphate particles, wherein the sintered ferric phosphate particles are spherical or near-spherical in shape. The particle size of the sintered iron phosphate particles is 4-10 μm.

3. A method for producing ferric phosphate particles using components of 13X molecular sieve crystallization mother liquor, characterized in that, The method includes the following steps: Step 1): Preparation of iron phosphate seed crystals: Use a 0.5 mol / L to 2.5 mol / L ferrous sulfate solution. Mix with a 40%-75% phosphoric acid solution, add purified water, and the concentration of Fe ions in the solution will increase. The concentration of the active ingredient was 0.2 mol / L to 2 mol / L, and the molar concentration of phosphorus was 0.2 mol / L to 1.5 mol / L. Stirring in a hot water bath dissolves the raw materials to obtain a seed crystal solution; take 1 to 5 kg of the seed crystal solution and place it in a reaction vessel. Add 1-10 grams of a powder with a particle diameter of 1.2 to 1.5 micrometers from the 13X molecular sieve crystallization mother liquor to the reactor. 13X micro molecular sieve particles, spaced between meters apart, were used as seed crystals; under the condition of maintaining a water bath temperature of 50-70℃, Add 0.5-5 kg ​​of hydrogen peroxide with a mass concentration of 15-35% under stirring conditions to allow the oxidation reaction to continue. Run for 15 to 90 minutes; thereafter, add a 5-20 wt% sodium hydroxide solution to adjust the pH. The reaction was carried out at a water bath temperature of 50-70℃; after the reaction, the obtained crude seed crystals were washed and filtered, and then... Add phosphoric acid at a mass ratio of 1:(0.5-1.5) to the filtered crude seed crystal product and phosphoric acid, using a phosphoric acid concentration of 20%-30%. The acid solution was subjected to a aging reaction, and then filtered to obtain iron phosphate seed crystals. Step 2): Weigh 500-2000 ml of sodium hydroxide solution from the 13X molecular sieve crystallization mother liquor. The sodium hydroxide solution is filtered to remove impurities, yielding a filtered mother liquor with a mass concentration of 60-80%. Phosphoric acid, the filtered mother liquor, and a sodium hydroxide solution with a mass concentration of 15-30 wt% were added in the following mass ratio: (1-2):(1-5):(1-5) Mix and stir to obtain a mixture; add at a ratio of 0.5-1.5 kg per kg of mixture. Add hydrogen peroxide with a mass concentration of 15%-30%, mix thoroughly, and then add 1-5 wt% of the aforementioned [unspecified ingredient] to the mixture. The iron phosphate seed crystals obtained in step 1) are used to obtain a hydrogen peroxide mixture; the above hydrogen peroxide mixture is then reacted with 1 mol / L... Add ferrous sulfate solution to a 2 mol / L solution at a mass ratio of 1:1, and react for 1 to 3 days. After 2 hours, the material is filtered and washed with water to obtain the raw material to be sintered; the raw material to be sintered is then heated at 100℃-150℃. Pre-sintering for 1-3 hours, followed by calcination at 500-650℃ for 3 to 12 hours, yields ferric phosphate product; The 13X molecular sieve crystallization mother liquor comes from the following steps: Step a): Prepare a mixture using sodium silicate solution, sodium aluminate solution, sodium hydroxide solution, and purified water. Gel; Step b): The mixed gel formed in step a) is matured in a crystallization vessel at a specific temperature. The temperature is controlled between 50℃ and 80℃, and the maturation time is 4-12 hours to obtain the maturated material; Step c): The matured material obtained in step b) is crystallized in a crystallization kettle, with the pressure controlled at... The pressure is 1.0 MPa to 2.0 MPa, the crystallization temperature is controlled at 100-150℃, and the crystallization time is 9 to 24 hours to obtain the crystal. Crystalline mixture; Step d): Filter the crystallization mixture, using a filter with a pore size of 1.0 μm-1.5 μm. The filter screen produces a product consisting of large-particle 13X molecular sieves on top and a 13X molecular sieve mother liquor below the screen. The molecular sieve mother liquor comprises the sodium hydroxide solution and the particles with a diameter between 1.2 and 1.5 micrometers. 13X micro molecular sieve particles; The method for producing iron phosphate particles using the crystallization mother liquor components of 13X molecular sieve improves phosphorus content. The ability to control the surface morphology of ferric phosphate particles and the density of ferric phosphate particles.

4. The method according to claim 3, wherein in the method, The prepared ferric phosphate product is sintered ferric phosphate particles, and the morphology of the sintered ferric phosphate particles is as follows: The sintered iron phosphate particles are spherical or near-spherical, with a particle size of 4 μm-10 μm.

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