Process for producing iron chloride from iron phosphate compounds

Abstract

i) A step of reacting a material containing at least one iron phosphate compound with at least one alkali metal chloride and / or at least one alkaline earth metal chloride at a temperature of 200°C to 1100°C in an inert gas atmosphere, and ii) Step of extracting and isolating the iron chloride formed in the exhaust gas stream. A process for producing iron chloride, characterized by including the following:

Description

Technical Field

[0001] The present invention relates to a process for producing iron chloride from an iron phosphate compound-containing material.

Background Art

[0002] Iron chlorides such as Fe(II)Cl2 and Fe(III)Cl3 are typically produced from metallic iron. However, iron-containing compounds, which have not been considered as alternative raw materials for producing iron chloride until now, are becoming increasingly available in large quantities. Examples include lithium iron phosphate (LFP) and lithium manganese iron phosphate (LFMP), which are employed as cathode materials for batteries (also known as cathode active materials (CAM)), and their modifications doped with further elements, especially metals. For these, there is a need for recycling after their life cycle, and thus they are suitable as attractive sources of iron raw materials.

[0003] Synthetic iron phosphate compounds such as LFP and LFMP thus have in common that they contain iron phosphate compounds that can be used as further means for producing iron chloride.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, an object of the present invention is to provide a suitable process using an iron phosphate compound as a starting material.

Means for Solving the Problems

[0005] Surprisingly, the inventors i) reacting a material containing at least one iron phosphate compound with at least one alkali metal chloride and / or at least one alkaline earth metal chloride in an inert gas atmosphere containing oxygen at a temperature of 200°C to 1100°C, preferably less than 200 ppm, particularly less than 100 ppm, and ii) Step of extracting and isolating the iron chloride formed in the exhaust gas stream. We have discovered a process for producing iron chloride that is characterized by containing [a specific ingredient]. [Modes for carrying out the invention]

[0006] Iron phosphate compounds Suitable iron phosphate compounds include, for example, iron phosphate, particularly iron(II) phosphate, iron(III) phosphate, and iron(III) pyrophosphatase, triphyline, and other lithium iron phosphates (LFP) or lithium manganese iron phosphates (LFMP), which are collectively referred to by the general formula LiFe (1-x) Mn x This can be expressed as PO4 (where 0 ≤ x < 0.9).

[0007] Iron phosphate can exist in anhydrous form or as hydrated iron phosphate, where the latter includes, for example, vivianite, which can generally be represented by the formula Fe3(PO4)2·8H2O; metavianite, which can generally be represented by the formula Fe2(PO4)2(OH)2·6H2O; strengite, which can generally be represented by the formula Fe(PO4)·2H2O; kryzhanovskite, which can generally be represented by the formula Fe3(OH)3(PO4)2; and phosphoferrite, which can generally be represented by the formula Fe3(H2O)3(PO4)2.

[0008] It will be recognized that these iron phosphate compounds may be employed in any desired mixture.

[0009] Preferred iron phosphate compounds are those with the common general formula LiFe (1-x) Mn x It is an LFP and / or LFMP having PO4 (wherein 0≦x<0.9, in particular 0≦x<0.6).

[0010] material A material containing at least one iron phosphate compound may consist of 100% iron phosphate compounds, but typically contains only a portion of them. It is preferable that the material used contains a total of 1% to 40% by weight of iron phosphate compounds, preferably 1% to 15% by weight.

[0011] The materials used are iron phosphate, especially iron(II) phosphate, iron(III) phosphate and iron(III) pyrophosphate, lithium iron phosphate (LFP), lithium manganese iron phosphate (LFMP), and especially those with the common general formula LiFe (1-x) Mn x It contains at least one iron phosphate compound selected from the group consisting of LFP and / or LFMP having PO4 (wherein 0 ≤ x < 0.9, especially 0 ≤ x < 0.6), or mixtures thereof.

[0012] Materials containing LFP and / or LFMP are preferred. Thus, the process according to the present invention particularly employs materials containing LFP and / or LFMP in a proportion of 5% to 100% by weight, preferably 40% to 99% by weight, especially 50% to 99% by weight, and especially preferably 70% to 99% by weight.

[0013] Preferably, the composition of the material used can also be expressed by determining the mass fraction of certain elements in the preferably used LFP and / or LFMP-containing material (based on the amount of material in each case), where the material used is preferably: 1% to 36% by weight of Fe (preferably 2% to 100% by weight of which is an iron phosphate compound), 1% to 20% by weight of P, Mn in a weight of 0% to 35% 1-8% by weight of Li and 1% to 55% by weight, preferably 1% to 40% by weight, and especially 1% to 30% by weight of carbon It contains.

[0014] The amounts of these reported elements may originate not only from LFP or LFMP, but also from other components of the material used, such as residues of metal components. Elemental content is preferably determined by conventional elemental analysis methods. The type and amount of iron phosphate compounds present are Cu-K α It is preferable to determine the phase by X-ray scattering (XRD) of the powder using radiation reflection. The obtained reflections are compared with data from, for example, ICDD (International Centre for Diffraction Data) and assigned to the obtained iron phosphate-containing phase. For lithium iron phosphate, the reflections from JCPDS (International Centre for Powder Diffraction Data Sample) Card #83-2092 are used here for comparison.

[0015] The material used preferably contains 1% to 55% by weight of carbon, more preferably 1% to 40% by weight, and especially 1% to 30% by weight of carbon, particularly graphite and / or carbon black.

[0016] Preferably, the total amount of LFP and / or LFMP and carbon in the LFP and / or LFMP-containing material used is more than 70% by weight, preferably more than 80% by weight, and particularly preferably more than 90% by weight.

[0017] LFP and / or LFMP-containing battery cells are typically mechanically crushed as much as possible, and the remainder containing the positive and negative electrode materials, optionally binders and further components, is finely ground into a mass that appears black due to the dark-colored LFP / LFMP and graphite-containing negative electrode material, and is therefore known as "black mass." As a result of technically incomplete separation, the black mass may also contain residues of other battery components, such as metal.

[0018] The material may therefore be so-called black mass having an iron phosphate compound in a proportion of 5% to 90% by weight.

[0019] The material employed may also preferably contain from 0 wt% to 15 wt%, preferably from 0 wt% to 5 wt% of metals, particularly Al, Cu, Co, and Ni.

[0020] The aluminum content determined as elemental aluminum in the material employed is preferably less than 10 wt%, particularly preferably less than 5 wt%.

[0021] The material employed preferably contains polymer particles such as polyethylene and / or polypropylene, particularly plastics, of preferably less than 10 wt%, particularly less than 1 wt%, and particularly preferably less than 0.1 wt%.

[0022] It is also preferable that the material used contains less than 5 wt% of PVDF (polyvinylidene fluoride) and / or other binders, such as carboxymethyl cellulose and / or alginates. The content of all binders is preferably less than 5 wt%.

[0023] The VOC content of the material used is preferably less than 1 wt%, particularly less than 0.1 wt%, and particularly preferably less than 0.01 wt%. VOC (volatile organic compounds) is preferably understood to mean organic compounds having a boiling point within the range of 50 to 260 °C at a standard pressure of 101.3 kPa.

[0024] The LFP and / or LFMP-containing material employed is preferably black mass derived from battery micronization.

[0025] The material employed preferably has an average particle size of 0.1 μm to 10 mm. Depending on the dimensions, the particle size can be determined simply by sieving or, for smaller particles, by laser diffraction or laser scattering methods. The best method to be used in each case is known to those skilled in the art.

[0026] Preferably employed LFP and / or LFMP-containing materials may also be coated materials. Preferred coating materials include carbon, particularly graphite, and metal oxides.

[0027] Alkali metal chlorides Suitable alkali metal chlorides include, preferably, NaCl, KCl, LiCl, and mixtures thereof. NaCl or KCl, or mixtures of NaCl and KCl, are preferred. When NaCl is used in admixtures with other alkali metal chlorides, particularly KCl, the mixing weight ratio is preferably 10:1 to 0.1:1, and particularly 5:1 to 0.5:1.

[0028] In elemental analysis, alkali metal chlorides are preferably used in amounts of 1 to 5 moles per mole of iron present in each case.

[0029] Alkaline earth metal chlorides Suitable alkaline earth metal chlorides include, in particular, MgCl2, CaCl2, or mixtures thereof. MgCl2 is preferred.

[0030] A mixture of alkaline earth metal chlorides and alkali metal chlorides in a weight ratio of 4:1 to 0.25:1, particularly 2:1 to 1:2, is preferred, especially a mixture of MgCl2 and NaCl and / or KCl. A mixture of KCl, NaCl and MgCl2 is particularly preferred.

[0031] Similarly, it is particularly preferable to use a mixture of MgCl2 and KCl in a weight ratio of 3:1 to 0.5:1.

[0032] others A molar ratio of chlorine derived from alkali metal chlorides and alkaline earth metal chlorides to phosphate bases present in the material is particularly preferred, within the range of 1:1 to 4:1, preferably 2.3:1 to 3.5:1 mol / mol.

[0033] process The materials used, as well as input materials such as alkali metal chlorides and / or alkaline earth metal chlorides, are preferably mixed in a dry form in the mixer. Preferably, the mixer used is a paddle mixer or other mill, such as a ball mill. The latter has the advantage that good homogenization of the reactants used can also be achieved by fine grinding.

[0034] To protect any potentially hygroscopic components from water absorption, which could adversely affect the process yield, it is advantageous to have already performed the reactant mixing step in a preferably anhydrous inert gas atmosphere.

[0035] The reaction itself is preferably carried out in the absence of air and water. Preferred inert gases include nitrogen, argon, or carbon dioxide. The inert gas atmosphere preferably contains less than 200 ppm of oxygen, and more preferably less than 100 ppm.

[0036] The reaction of iron phosphate compounds can be carried out in a fluidized bed, dumped bed, or moving bed reactor, in a shaft furnace, or preferably in an atmosphere furnace, most simply in an indirectly heated tubular furnace or rotary furnace. Optionally, the material may be formed before introducing it into the furnace, for example by brining, extrusion, or pelletizing, with optional subsequent heat pretreatment at 100°C to 199°C.

[0037] Phyllosilicates, particularly bentonite, and auxiliary agents such as lignosulfonates, methylcellulose, water glass, and starch can be used for this purpose. Products formed by reactions that are volatile at the reaction temperature (here particularly iron chloride, as well as aluminum chloride, and optionally further heavy metal chlorides) are preferably redimetered and recovered together at a cold spot at a temperature below 150°C, or redimetered and recovered separately at different cold spots.

[0038] For FeCl2, the preferred separation temperature is 700°C or lower, preferably 600°C or lower. In the case of iron(III) chloride, the resublimation temperature may be less than 307°C.

[0039] Iron(III) chloride, and AlCl3 in the case of aluminum in the material used, can preferably be separated from the exhaust gas stream by resublimation on cooled surfaces having different temperatures, and can also be separated from each other. When iron(III) chloride is present in the exhaust gas stream together with AlCl3, each chloride can be separated and resublimated on different surfaces having different temperatures because their boiling points are sufficiently different, and therefore can be separated with very high purity.

[0040] For FeCl2, the preferred precipitation temperature is less than 700°C, particularly between 699°C and 307°C; for FeCl3, it is less than 307°C, particularly between 150°C and 300°C; and for AlCl3, it is less than 150°C, particularly between 110°C and 149°C.

[0041] The iron recovered in the form of iron(III) chloride and / or iron(II) chloride according to the present invention is already of very high purity and can be converted into a desired raw material form of iron for the novel production of LFP and / or LFMP, for example. Here, examples include a wide variety of different forms of iron sulfate, iron nitrate, iron phosphate, or iron oxide.

[0042] Alternatively, iron chloride can be directly introduced as a gaseous stream into an aqueous medium containing sulfuric acid, nitric acid, or phosphoric acid, even without precipitation by resublimation, thereby forming the corresponding iron(III) sulfate, iron(III) nitrate, or iron(III) phosphate. Iron(II) sulfate, iron(II) nitrate, or iron(II) phosphate can also be obtained by using a suitable reducing agent in combination during the reaction.

[0043] However, it is preferable to separate iron chloride from the exhaust gas flow by resublimation.

[0044] The exhaust gas flow contains not only gaseous iron chloride such as iron(III) chloride or iron(II) chloride, and optionally AlCl3 (if aluminum is present in the materials used), but also optionally NaCl, and optionally further volatile chlorides of metals (if these metals are present in the black mass).

[0045] The residue after the reaction preferably contains phosphates of the alkali metal and / or alkaline earth metal groups used.

[0046] Lithium ions present in the residue can be extracted by shaking the dried residue with a suitable non-aqueous solvent. Suitable solvents include alcohols, esters or ethers, ketones or nitriles, or mixtures thereof, optionally with water.

[0047] The residue obtained after extraction, preferably from poor lithium to lithium-free, is preferably treated by adding 0.1 to 5 moles of phosphoric acid / 1 mole of phosphate, preferably 0.2 to 1 mole of phosphoric acid / 1 mole of phosphate. The reaction residue can therefore be converted directly into a soluble form suitable for agricultural use.

[0048] The remaining insoluble residue is preferably carbon, if carbon was present in the material used. The remaining water-soluble components can then be optionally confirmed to be present by a conventional H2S separation process, and then separated from each other and isolated in the form of sulfides, chlorides, phosphates, fluorides, or other precipitated compounds.

[0049] temperature The reaction is preferably carried out at a temperature of 400°C to 900°C. The reaction typically takes 5 minutes to 10 hours, preferably 2 to 5 hours.

[0050] If the material to be used has a binder content of more than 1% by weight based on the material, it is preferable to reduce the content to less than 0.1% by weight by leaching using an organic solvent such as acetone, ethyl acetate, methyl ethyl ketone, tetrahydrofuran (THF), ethyl acetoethyl, acetylacetone, dioxane and / or acetic anhydride, or mixtures thereof.

[0051] If the material contains polymers, particularly plastics, in a content exceeding 1% by weight, it is advantageous to first heat-treat the material at a temperature of 300°C to 600°C, preferably under an inert gas atmosphere, to reduce the polymer content to less than 0.1% by weight. In addition to leaching with organic solvents, binder content that may exceed 1% may be reduced to less than 0.1% by weight by heat treatment at a temperature of 300°C to 700°C, preferably under an inert gas atmosphere, instead or additionally.

[0052] reactor The material used in the process according to the present invention is preferably introduced into a reactor provided with a layer that is resistant under the set reaction conditions. Preferred reactor materials are nickel-coated or graphite-coated reactors. Possible reactors used include rotary tubular reactors or other tubular reactors. Reactors that allow the material to move around during the reaction are particularly preferred. Reactions in fluidized bed apparatuses and rotary tubular reactors, or in screw-type extruders are preferred.

[0053] In the case of a tubular reactor, the length of the reactor is preferably 0.2 to 40 m. The residence time in the reactor during the reaction generally depends on the temperature. The residence time in the reactor can be extended, for example, from 1 minute to 5 hours. The process according to the present invention can be carried out in batches or continuously.

[0054] Preferably, there is an outlet for the exhaust gas flow in the reactor. The exhaust gas flow contains gaseous reaction products and volatile components of the materials that can be removed together from the reaction space. Possible separation of solid components, such as fine dust, from the gaseous components of the exhaust gas flow can be carried out by a device such as a cyclone.

[0055] The reaction is preferably terminated when the proportion of iron in the residue reaches less than 0.05% by weight.

[0056] The preferred precipitation temperature for FeCl2 is less than 700°C, for FeCl3 it is 307°C or less, particularly 150°C to 300°C, and for AlCl3 it is 150°C or less, particularly 110°C to 149°C.

[0057] The sparingly soluble manganese sulfide remaining after the H2S separation process can be recovered by reacting with air to yield manganese sulfate, which can optionally be reused for the production of LFMP. [Examples]

[0058] analysis After dissolving the LFF sample, LFP, or sublimation with a suitable acid, the instrument was calibrated for each element using standard solutions, and then analyzed using an ICP-OES instrument.

[0059] X-ray diffractograms (XRDs) were recorded on powder (mounted flat) at a wavelength of 0.154 nm and a 2θ angle from 0° to 60°.

[0060] Example 1: LFP NaCl / MgCl2 The following analytical data (weight %): 5.02 g of lithium iron phosphate (31.7 mmol phosphate) (structure confirmed by XRD; no further reflections other than those from lithium iron phosphate were detected) had the following composition: Fe 34.6%, phosphate 60.9%, Li 4.6%, and C 1.8%, with an average particle size distribution of d10 0.35 μm, d50 0.62 μm, and d100 6.7 μm. This mixture was thoroughly mixed and homogenized with 1.83 g of NaCl (31.3 mmol chloride) and 2.24 g of anhydrous MgCl2 (47 mmol chloride), and then placed in a quartz glass tube (diameter: 120 mm) in a tubular furnace.

[0061] A stream of dry nitrogen (0.3 liters / minute; oxygen content <100 ppm v / v) is passed through the reactor and heated to 750°C, where it is maintained for 6 hours. A brown precipitate (1.17 g) is precipitated at approximately 160°C using a cooler quartz tube protruding from the furnace. The precipitate contains a mixture of 82 wt% iron(II) and iron(III) chloride and 15 wt% NaCl. The proportion of NaCl can be reduced by lowering the reaction temperature.

[0062] The sample weight loss is 34% by weight. The residue contains significantly less iron than the reactants and is therefore lighter in color.

[0063] The residue is added to 50 ml of anhydrous ethanol and then filtered. This process is repeated twice. The filtrates are combined and the ethanol is evaporated. The residue contains lithium compounds.

[0064] The residue remaining after ethanol extraction was first dried and then mixed with concentrated phosphoric acid. The resulting soluble phosphate has a very low iron content and can therefore be used as a plant fertilizer.

[0065] Example 2: LFP KCl / MgCl2 The following analytical data (weight %): 5 g of lithium iron phosphate (31.7 mmol phosphate) (structure confirmed by XRD, no further reflections other than those from lithium iron phosphate were detected) had the following composition: Fe 34.6%, phosphate 60.9%, Li 4.6%, and C 1.8%, with an average particle size distribution of d10 0.35 μm, d50 0.62 μm, and d100 6.7 μm. This mixture was thoroughly mixed and homogenized with 3 g of KCl (40 mmol chloride) and 2 g of anhydrous MgCl2 (42 mmol chloride), and then placed in a quartz glass tube (diameter: 120 mm) in a tubular furnace.

[0066] A stream of dry nitrogen (0.3 liters / minute; oxygen content <100 ppm v / v) is passed through the reactor and heated to 750°C, where it is maintained for 12 hours. The brown precipitate (3.4 g) is precipitated at approximately 160°C in a cooler quartz tube protruding from the furnace. The precipitate contains a mixture of iron(II) and iron(III) chloride.

[0067] The sample weight loss was 45% by weight, and the residue was considerably lighter in color than the reactants.

[0068] The residue is added to 200 ml of anhydrous ethanol and then filtered. This process is repeated twice. The filtrates are combined and the ethanol is evaporated. The residue contains lithium compounds.

[0069] The residue remaining after ethanol extraction was first dried and then mixed with concentrated phosphoric acid. The resulting soluble phosphate has a very low iron content and can therefore be used as a plant fertilizer.

Claims

1. i) A step of reacting a material containing at least one iron phosphate compound with at least one alkali metal chloride and / or at least one alkaline earth metal chloride at a temperature of 200°C to 1100°C in an inert gas atmosphere, and ii) Step of extracting and isolating the iron chloride formed in the exhaust gas stream. A process for producing iron chloride, characterized by including the following:

2. The process according to claim 1, characterized in that the iron chloride is precipitated from the exhaust gas flow by resublimation in step ii).

3. The aforementioned iron chloride is FeCl ２ Regarding this, the temperature should be less than 700°C, preferably between 699°C and less than 307°C, and FeCl ３ The process according to claim 1 or 2, characterized in that the precipitate is formed at a temperature of less than 307°C, particularly between 150°C and 300°C.

4. The materials used are iron phosphate, in particular iron(II) phosphate, iron(III) phosphate and iron(III) pyrophosphate, lithium iron phosphate (LFP), and lithium iron manganese phosphate (LFMP), in particular the common general formula LiFe （１－ｘ） Mn ｘ PO ４ The process according to any one of claims 1 to 3, characterized by containing at least one iron phosphate compound selected from the group consisting of LFP and / or LFMP having (wherein 0 ≤ x < 0.9, particularly 0 ≤ x < 0.6) in the formula, or mixtures thereof.

5. The process according to any one of claims 1 to 4, characterized in that the reaction is carried out with at least one alkali metal chloride and at least one alkaline earth metal chloride.

6. The process according to any one of claims 1 to 5, characterized in that the reaction is carried out with sodium chloride and magnesium chloride or potassium chloride and magnesium chloride.

7. The process according to any one of claims 1 to 6, characterized by employing a mixture of alkaline earth metal chlorides and alkali metal chlorides in a weight ratio of 4:1 to 0.25:1, particularly 2:1 to 1:

2.

8. The materials used are 1% to 36% by weight of Fe (preferably 2% to 100% by weight of which is an iron phosphate compound), 1% to 20% by weight of P, 0% to 35% by weight of Mn, 1 to 8% by weight of Li and 1% to 55% by weight of carbon The process according to any one of claims 1 to 7, characterized by containing

9. The process according to any one of claims 1 to 8, characterized in that the material used contains 5% to 100% by weight, preferably 40% to 99% by weight, particularly 50% to 99% by weight, and most preferably 70% to 99% by weight of an iron phosphate compound.

10. The process according to any one of claims 1 to 9, characterized in that the molar ratio of chlorine derived from the alkali metal chloride and alkaline earth metal chloride used to phosphate base present in the material is in the range of 1:1 to 4:1, preferably 2.3:1 to 3.5:1 mol / mol.

11. The process according to any one of claims 1 to 10, characterized in that the reaction is carried out at a temperature of 400°C to 1000°C.

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