A method for preparing lithium iron phosphate by using waste lithium hydroxide octanoate catalyst

Abstract

The application provides a method for preparing lithium iron phosphate by using waste lithium isooctanoate catalyst, and comprises the following steps: grinding and sieving the waste lithium isooctanoate catalyst to obtain lithium isooctanoate powder; mixing the lithium isooctanoate powder with water, adding concentrated hydrochloric acid to perform leaching reaction to obtain leaching slurry; filtering the leaching slurry to obtain filtrate and residue; adding activated carbon to the filtrate to perform adsorption and filtration, then adding HCl and FeCl3·6H2O to stir, and controlling the pH of the solution to be 1.0-1.5 to obtain an aqueous phase; uniformly mixing tributyl phosphate and sulfonated kerosene to obtain an organic phase; mixing, oscillating, standing and separating the aqueous phase and the organic phase to obtain an extraction phase and a raffinate phase; washing the extraction phase by using dilute hydrochloric acid to remove impurities, adjusting the molar ratio of P, Fe and Li in the extraction phase after impurity removal, adding a carbon source to obtain mixed slurry; performing spray drying on the mixed slurry, and performing high-temperature sintering, crushing and screening on the powder obtained by spray drying to remove iron, so as to obtain lithium iron phosphate. The application scheme realizes resource recycling and utilization, and the prepared product has high quality and low cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium iron phosphate preparation, and particularly relates to a method for preparing lithium iron phosphate by using waste lithium isooctanoate catalyst. BACKGROUND

[0002] Lithium iron phosphate (LiFePO4) has become one of the positive materials of lithium batteries due to its high specific capacity, environmental friendliness, structural stability, high safety performance, good cycle performance and the like, and plays a huge role in the field of lithium ion battery materials. At present, there are many methods for preparing lithium iron phosphate on the market, mainly including traditional iron red, carbon thermal reduction method of iron phosphate, and liquid phase synthesis method of self-heating evaporation. However, with the gradual increase of the prices of iron phosphate raw materials and lithium carbonate, the profit space of lithium iron phosphate is becoming smaller and smaller. Therefore, it has become the main trend in the market to prepare low-cost lithium iron phosphate, and it is more and more urgent to develop a low-cost lithium iron phosphate preparation process. SUMMARY

[0003] In view of this, the application provides a method for preparing lithium iron phosphate by using waste lithium isooctanoate catalyst.

[0004] To achieve the above-mentioned purpose, the application adopts the following technical scheme:

[0005] A method for preparing lithium iron phosphate by using waste lithium isooctanoate catalyst, comprising the following steps:

[0006] Grinding and sieving the waste lithium isooctanoate catalyst to obtain lithium isooctanoate powder;

[0007] Mixing the lithium isooctanoate powder with water, adding concentrated hydrochloric acid to carry out leaching reaction, and obtaining leaching slurry;

[0008] Filtering the leaching slurry to obtain filtrate and residue;

[0009] Adding an adsorbent to the filtrate for adsorption and filtration, then adding HCl and FeCl3·6H2O for stirring, and controlling the pH of the solution to be 1.0-1.5 to obtain an aqueous phase;

[0010] Mixing and uniformly mixing tributyl phosphate and sulfonated kerosene to obtain an organic phase;

[0011] Mixing, oscillating, standing and separating the aqueous phase and the organic phase to obtain an extraction phase and a raffinate phase;

[0012] Washing and removing impurities from the extraction phase by using dilute hydrochloric acid, adjusting the P, Fe and Li molar ratio in the extraction phase after removal of impurities, and adding a carbon source to obtain a mixed slurry;

[0013] Spray drying the mixed slurry, high-temperature sintering the powder obtained by spray drying, crushing and sieving to remove iron, and obtaining lithium iron phosphate.

[0014] Further, the raffinate phase is concentrated to a Li content of 6-10 g / L, then HCl and FeCl3·6H2O are added, and the solution pH is adjusted to 1.0-1.5 to obtain an aqueous phase, which is recycled.

[0015] The gas phase generated during spray drying is condensed, and the obtained tributyl phosphate is recycled.

[0016] Further, the sieve screen is 80-150 mesh.

[0017] Further, the leaching reaction conditions are: temperature 5-20°C, time 60-120 min, and total mass of water and concentrated hydrochloric acid: mass of lithium iso-octanoate powder = (4-7):1.

[0018] The lithium concentration in the leaching slurry is 6-10 g / L, H + and Li + The molar ratio is = (1.03-1.2):1, and the pH is 1.7-2.5.

[0019] Further, the adsorbent is activated carbon, and the activated carbon is added in an amount of 0.5wt%-2wt% of the mass of the filtrate.

[0020] Further, the amount-of-substance ratio of iron to lithium in the aqueous phase is (1.2-1.7):1, and the stirring time is 10-30 min.

[0021] Further, the volume ratio of tributyl phosphate to sulfonated kerosene in the organic phase is 1:(1-2.5).

[0022] Further, the organic phase and the aqueous phase are mixed and shaken for extraction at a volume ratio of (1-3):1, and the shaking time is 5-20 min.

[0023] Further, the pH of the dilute hydrochloric acid used for the impurity removal is 1.2-2.0, and the amount of dilute hydrochloric acid used is 25-50% of the mass of the extraction phase.

[0024] Further, the molar ratio of P, Fe, and Li in the organic extraction phase after the impurity removal is (1.02-1.05):(1.02-1.05):(1.02-1.05).

[0025] The substance for adjusting the phosphorus content is any one of monammonium phosphate and diammonium phosphate, the substance for adjusting the lithium content is any one of lithium hydroxide and lithium chloride, the substance for adjusting the iron content is any one of ferric chloride and iron hydroxide, and the carbon source is any one of glucose and sucrose.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] (1) The application utilizes waste lithium isooctanoate catalyst to prepare lithium iron phosphate, develops a brand-new preparation process, realizes recycling of resources, and makes the prepared lithium iron phosphate product low in cost and more competitive.

[0028] (2) In the scheme, the raffinate phase of the intermediate step is concentrated and reused, and the phosphoric acid tributyl ester obtained by condensing the gas phase generated by spray drying is recycled, thereby improving product yield and reducing the use of raw materials.

[0029] (3) The lithium iron phosphate product prepared in the scheme has excellent performance and meets the standard YS / T1027-2015 Lithium Iron Phosphate. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The process flow diagram of the scheme is shown in the figure. DETAILED DESCRIPTION

[0031] The application will be further described in detail below in combination with specific examples, so that those skilled in the art can more clearly understand the application.

[0032] Key test material sources and physicochemical parameters:

[0033] The waste lithium isooctanoate catalyst comes from scrap and contaminated materials generated in the production process of lithium isooctanoate manufacturers, and the main components are as shown in the following table:

[0034] Table 1 Composition of waste lithium isooctanoate catalyst

[0035]

[0036] Example 1

[0037] The example provides a method for preparing lithium iron phosphate by using waste lithium isooctanoate catalyst, comprising the following steps:

[0038] S1, the waste lithium isooctanoate catalyst is put into a grinder and ground for 10 min, and then passed through a 100-mesh sieve to obtain lithium isooctanoate powder.

[0039] S2, the lithium isooctanoate powder is mixed with water and then added with concentrated hydrochloric acid for leaching reaction to obtain leaching slurry, wherein the reaction temperature is 10℃, the reaction time is 100 min, the total mass of water and concentrated hydrochloric acid: lithium isooctanoate powder mass = 5:1, the lithium concentration in the leaching slurry is controlled to be 8g / L, the H + + molar ratio is = 1.1:1, and the pH at the end of leaching is 2.0.

[0040] ​S3. Filter the leachate to obtain filtrate and filter residue. At this time, the filtrate mainly contains lithium chloride and a small amount of organic matter, and the filter residue mainly contains isooctanoic acid (isooctanoic acid is slightly soluble in cold water, with a water solubility of 2 g / L at 20℃). Analyze the lithium content of the filtrate, and the lithium leaching rate is 92.24%. Add 1 wt% of activated carbon to the filtrate for adsorption and then filter. Then add HCl and FeCl3·6H2O and stir for 20 min to obtain an aqueous phase. The pH of the aqueous phase is controlled at 1.2, and the molar ratio of iron to lithium is 1.5:1.

[0041] In this step, activated carbon is mainly used to adsorb organic matter contained in the filtrate; while the added HCl and FeCl3·6H2O undergo the following reaction: FeCl3+Cl-=FeCl4-.

[0042] S4. Mix tributyl phosphate (TBP) and sulfonated kerosene at a volume ratio of 1:2 to obtain an organic phase.

[0043] S5. Mix the above organic phase and aqueous phase at a volume ratio of 2:1, shake and extract for 10 min, let stand, and separate to obtain the extract phase and the raffinate phase. The raffinate phase is then concentrated to a Li content of 8 g / L and returned to step S3 to prepare the aqueous phase for recycling.

[0044] During this step of the shake extraction, the following reaction occurs: 2TBP + Li + +FeCl4-=LiFeCl4·2TBP, at which point the lithium extraction rate is 88.66%.

[0045] S6. After washing the extract phase with dilute hydrochloric acid (pH=1.5, 40% of the extract phase mass) to remove impurities, add monoammonium phosphate, lithium hydroxide, and ferric chloride to adjust the molar ratio of P, Fe, and Li in the extracted phase after impurity removal. Add glucose as a carbon source to obtain a mixed slurry. Control the molar ratio of P, Fe, and Li in the mixed slurry to be 1.03:1:1.03, and the carbon content in the finished lithium iron phosphate product to be 1.5 wt%.

[0046] S7. The mixed slurry is spray-dried at 310°C. The powder obtained by spray drying is sintered at high temperature, crushed, and screened to remove iron in a roller furnace to obtain lithium iron phosphate. In addition, the gas phase generated during spray drying is condensed. The tributyl phosphate obtained by condensation is returned to step S4 to be re-formulated into an oil phase to achieve the purpose of recycling.

[0047] Example 2

[0048] This embodiment provides a method for preparing lithium iron phosphate using spent lithium isooctanoate catalyst, including the following steps:

[0049] S1. Place the waste lithium isooctanoate catalyst into a grinder and grind for 15 minutes. Then pass it through a 150-mesh sieve to obtain lithium isooctanoate powder.

[0050] S2. Lithium isooctanoate powder is mixed with water and then leached with concentrated hydrochloric acid to obtain a leaching slurry. The reaction temperature is 5℃, the reaction time is 120 min, and the total mass ratio of water and concentrated hydrochloric acid to lithium isooctanoate powder is 4:1. The lithium concentration in the leaching slurry is controlled at 10 g / L. + Li + The molar ratio was 1.2:1, and the pH at the leaching endpoint was 1.7.

[0051] S3. Filter the leachate to obtain filtrate and filter residue. At this time, the filtrate mainly contains lithium chloride and a small amount of organic matter, and the filter residue mainly contains isooctanoic acid (isooctanoic acid is slightly soluble in cold water, with a water solubility of 2 g / L at 20℃). Analyze the lithium content of the filtrate, and the lithium leaching rate is 94.35%. Add 0.5 wt% of activated carbon to the filtrate for adsorption and then filter. Then add HCl and FeCl3·6H2O and stir for 10 min to obtain an aqueous phase. The pH of the aqueous phase is controlled at 1.0, and the molar ratio of iron to lithium is 1.2:1.

[0052] S4. Mix tributyl phosphate and sulfonated kerosene at a volume ratio of 1:1 to obtain an organic phase.

[0053] S5. Mix the above organic phase and aqueous phase at a volume ratio of 1:1, shake and extract for 5 min, let stand, and separate to obtain the extract phase and the raffinate phase. At this time, the lithium recovery rate in the extract phase is 79.71%. The obtained raffinate phase is further concentrated to a Li content of 10 g / L and then returned to step S3 to prepare the aqueous phase, so as to achieve the purpose of recycling.

[0054] S6. After washing the extract phase with dilute hydrochloric acid at pH 1.2 (25% of the extract phase mass) to remove impurities, add monoammonium phosphate, lithium chloride, and ferric chloride to adjust the molar ratio of P, Fe, and Li in the purified extract phase. Add glucose as a carbon source to obtain a mixed slurry. Control the molar ratio of P, Fe, and Li in the mixed slurry to be 1.02:1:1.02, and the carbon content in the finished lithium iron phosphate product to be 1.2 wt%.

[0055] S7. The mixed slurry is spray-dried at 300°C. The powder obtained by spray drying is sintered at high temperature, crushed, and screened to remove iron in a roller furnace to obtain lithium iron phosphate. In addition, the gas phase generated during spray drying is condensed. The tributyl phosphate obtained by condensation is returned to step S4 to be re-formulated into an oil phase to achieve the purpose of recycling.

[0056] Example 3

[0057] This embodiment provides a method for preparing lithium iron phosphate using spent lithium isooctanoate catalyst, including the following steps:

[0058] S1. Place the waste lithium isooctanoate catalyst into a grinder and grind for 5 minutes. Then pass it through an 80-mesh sieve to obtain lithium isooctanoate powder.

[0059] S2. Lithium isooctanoate powder is mixed with water and then leached with concentrated hydrochloric acid to obtain a leaching slurry. The reaction temperature is 20℃, the reaction time is 60 min, and the total mass ratio of water and concentrated hydrochloric acid to lithium isooctanoate powder is 7:1. The lithium concentration in the leaching slurry is controlled at 6 g / L. + Li + The molar ratio was 1.03:1, and the pH at the leaching endpoint was 2.5.

[0060] S3. Filter the leachate to obtain filtrate and filter residue. At this time, the filtrate mainly contains lithium chloride and a small amount of organic matter, and the filter residue mainly contains isooctanoic acid (isooctanoic acid is slightly soluble in cold water, with a water solubility of 2 g / L at 20℃). Analyze the lithium content of the filtrate, and the lithium leaching rate is 90.68%. Add 2 wt% of activated carbon to the filtrate for adsorption and then filter. Then add HCl and FeCl3·6H2O and stir for 30 min to obtain an aqueous phase. The pH of the aqueous phase is controlled at 1.5, and the molar ratio of iron to lithium is 1.7:1.

[0061] S4. Mix tributyl phosphate and sulfonated kerosene at a volume ratio of 1:2.5 to obtain an organic phase.

[0062] S5. Mix the above organic phase and aqueous phase at a volume ratio of 3:1, shake and extract for 20 min, let stand, and separate to obtain the extract phase and the raffinate phase. The lithium recovery rate in the extract phase is 93.45%. The obtained raffinate phase is further concentrated to a Li content of 6 g / L and then returned to step S3 to prepare the aqueous phase, so as to achieve the purpose of recycling.

[0063] S6. After washing the extract phase with dilute hydrochloric acid (pH=2.0, 50% of the extract phase mass) to remove impurities, diammonium phosphate, lithium hydroxide, and iron hydroxide are added to adjust the molar ratio of P, Fe, and Li in the extracted phase after impurity removal. Glucose is added as a carbon source to obtain a mixed slurry. The molar ratio of P, Fe, and Li in the mixed slurry is controlled to be 1.05:1:1.05, and the carbon content in the finished lithium iron phosphate product is 1.8 wt%.

[0064] S7. The mixed slurry is spray-dried at 320°C. The powder obtained by spray drying is sintered, crushed, and screened to remove iron in a roller furnace to obtain lithium iron phosphate. The gas phase generated during spray drying is condensed, and the tributyl phosphate obtained by condensation is returned to step S4 to be re-formulated into an oil phase to achieve the purpose of recycling.

[0065] Comparative Example 1

[0066] This comparative example provides a method for preparing lithium iron phosphate using waste lithium isooctanoate catalyst. The raw materials and methods are basically the same as those in Example 1, except that in step S2, the total mass of water and concentrated hydrochloric acid is 2:1 compared to the mass of lithium isooctanoate powder.

[0067] The final lithium leaching rate in the spent lithium isooctanoate catalyst was 61.24%.

[0068] Comparative Example 2

[0069] This comparative example provides a method for preparing lithium iron phosphate using waste lithium isooctanoate catalyst. The raw materials and methods are basically the same as those in Example 1, except that in step S5, the organic phase and the aqueous phase are mixed at a volume ratio of 0.5:1.

[0070] The final extraction process yielded a lithium extraction rate of 49.68%.

[0071] Comparative Example 3

[0072] This comparative example provides a method for preparing lithium iron phosphate using waste lithium isooctanoate catalyst. The raw materials and methods are basically the same as those in Example 1, except that the extract phase is washed with water to remove impurities in step S6.

[0073] The lithium iron phosphate samples prepared in Examples 1-3 and Comparative Examples 1-3 were tested according to the standard GB / T33822-2017 Nano Lithium Iron Phosphate. The results are shown in the table below:

[0074] Table 2 Chemical composition of lithium iron phosphate

[0075]

[0076]

[0077] Unless otherwise specified, all raw materials used in this invention are existing substances that can be purchased directly from the market.

[0078] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing lithium iron phosphate using spent lithium isooctanoate catalyst, characterized in that, Includes the following steps: The waste lithium isooctanoate catalyst was ground and sieved to obtain lithium isooctanoate powder; Lithium isooctanoate powder was mixed with water and then concentrated hydrochloric acid was added to carry out a leaching reaction to obtain a leaching slurry. The leachate is filtered to obtain filtrate and filter residue; Add an adsorbent to the filtrate for adsorption, then filter. Add HCl and FeCl3·6H2O and stir, controlling the pH to 1.0–1.5 to obtain the aqueous phase. Tributyl phosphate and sulfonated kerosene were mixed evenly to obtain an organic phase; The aqueous phase and the organic phase are mixed, shaken, allowed to stand, and separated to obtain the extract phase and the raffinate phase. After washing the extract phase with dilute hydrochloric acid to remove impurities, and adjusting the molar ratio of P, Fe and Li in the extracted phase, a carbon source is added to obtain a mixed slurry. The mixed slurry is spray-dried, and the powder obtained by spray drying is sintered at high temperature, crushed, and screened to remove iron, thus obtaining lithium iron phosphate.

2. The method according to claim 1, characterized in that, It also includes concentrating the raffinate to a Li content of 6-10 g / L, then adding HCl and FeCl3·6H2O to adjust the pH of the solution to 1.0-1.5 to obtain an aqueous phase for recycling; It also includes condensing the gas phase generated during spray drying, and recycling the tributyl phosphate obtained from the condensation.

3. The method according to claim 1 or 2, characterized in that, The sieve mesh is 80-150 mesh.

4. The method according to claim 1 or 2, characterized in that, The leaching reaction conditions are: temperature 5-20℃, time 60-120min, and the total mass of water and concentrated hydrochloric acid to the mass of lithium isooctanoate powder = (4-7):

1. The lithium concentration in the leaching slurry is 6–10 g / L, H + and Li + The molar ratio is (1.03~1.2):1, and the pH is 1.7~2.

5.

5. The method according to claim 1 or 2, characterized in that, The adsorbent is activated carbon, and the amount of activated carbon added is 0.5wt% to 2wt% of the filtrate mass.

6. The method according to claim 1 or 2, characterized in that, The molar ratio of iron to lithium in the aqueous phase is (1.2-1.7):1, and the stirring time is 10-30 min.

7. The method according to claim 1 or 2, characterized in that, The volume ratio of tributyl phosphate to sulfonated kerosene in the organic phase is 1:(1-2.5).

8. The method according to claim 1 or 2, characterized in that, The organic phase and aqueous phase are mixed and shaken at a volume ratio of (1-3):1 for 5-20 min.

9. The method according to claim 1 or 2, characterized in that, The pH of the dilute hydrochloric acid used in the washing and impurity removal process is 1.2 to 2.0, and the amount of dilute hydrochloric acid used is 25% to 50% of the mass of the extract phase.

10. The method according to claim 1 or 2, characterized in that, The molar ratio of P, Fe, and Li in the purified organic extract phase is (1.02–1.05):1:(1.02–1.05); The substance for adjusting phosphorus content is either monoammonium phosphate or diammonium phosphate; the substance for adjusting lithium content is either lithium hydroxide or lithium chloride; the substance for adjusting iron content is either ferric chloride or ferric hydroxide; and the carbon source is either glucose or sucrose.

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