Method for producing lioh

Abstract

The invention relates to a method for producing LiOH, having the following steps: (1) providing a mixture A containing Li2CO3; (2) treating the mixture A provided in (1) with carbonic acid, thereby at least partly converting the Li2CO3 contained therein into LiHCO3 and obtaining a mixture B containing LiHCO3; (3) thermally converting at least part of the mixture B obtained in (2) and obtaining a mixture C containing Li2CO3; and (4) reacting the mixture C obtained in (3) with M(OH)2 , thereby at least partly reacting the Li2CO3 contained therein in order to form LiOH and obtaining a mixture D containing LiOH, wherein M represents an alkaline earth metal.

Description

[0001] Process for the production of LIOH

[0002] TECHNICAL FIELD

[0003] The present invention relates to a process for the extraction of lithium hydroxide from lithium-containing minerals.

[0004] INTRODUCTION

[0005] WO 2019 / 220004 A1 relates to a process for obtaining lithium hydroxide from a lithium-containing mineral by mixing the mineral with water and an alkali metal carbonate, leaching the resulting mixture at elevated temperature and then leaching it a second time in an aqueous solution containing an alkaline earth metal hydroxide.

[0006] WO 2018 / 234614 A1 relates to a process for producing lithium carbonate from lithium-containing minerals. The process comprises a leaching step in which the lithium-containing mineral is leached in an aqueous solution containing alkali metal carbonate, a carbonation step in which the leaching slurry is reacted with an alkaline earth metal compound in the presence of CO2, and a solid-liquid separation step in which the carbonated mixture is subjected to solid-liquid separation.

[0007] EP 2749535 A1 relates to a process for producing high-purity lithium carbonate. The process comprises reacting a first aqueous solution containing lithium carbonate and CO2 to form a second aqueous solution containing dissolved LiHCO3, which is further separated using a gas-liquid-solid separator to obtain a third aqueous solution. The third aqueous solution is contacted with an ion-selective medium to produce a fourth aqueous solution from which high-purity lithium carbonate is precipitated.

[0008] CN 101948124 B relates to a process for the extraction of lithium carbonate from spodumene, in which, in a first step, alpha-spodumene is converted to beta-spodumene, which is further leached with an alkaline salt and water to yield lithium carbonate. The lithium carbonate is further reacted with CO2 and converted to lithium bicarbonate, which is further thermally treated to yield lithium carbonate.

[0009] WO 2011 / 148040 A1 relates to a process for the thermal processing of alpha-spodumene to beta-spodumene. The process comprises processing concentrate or ore in a fluidized-bed reactor at temperatures of 800 to 100 °C using an oxygen-containing gas. CN 103183366 A relates to a process for obtaining lithium salts from spodumene by caustic soda leaching and subsequent acid conversion of the resulting lithium carbonates into soluble lithium salts.

[0010] CN 113428882 A relates to a process for producing battery-grade lithium carbonate from spodumene.

[0011] WO 2023 / 081961 A1 relates to a process for extracting metals from a metal-containing material, wherein the process comprises a step in which the metal is dissolved in the process stream as carbonate or bicarbonate using carbon dioxide. The metal is preferably lithium, and the metal-containing material can be spodumene. Before contacting with CO2, the metal-containing material can be calcined. Furthermore, the process can be leached with a carbonate-containing reagent. The process preferably comprises a carbonation step in which carbon dioxide is contacted with an aqueous Li2COs solution to obtain a LiHCOs-containing solution. The LiHCOs-containing solution can be separated from the residue via filtration. The LiHCOs-containing solution is then subjected to a decarbonization step by heating the LiHCOs-containing solution, whereby purified Li2COs is produced.Optionally, the purified Li2COs is preferably treated with hydrated lime to obtain a LiOH solution and CaCOs.

[0012] CN 107265483 A relates to a process for producing LiOH monohydrate. In step S120 of the document, an aqueous Li2COs solution is contacted with carbon dioxide and converted to LiHCOs. Subsequently, the resulting LiHCOs is pyrolyzed to Li2COs in step S140, and the Li2COs is preferably contacted with an aqueous calcareous solution in step S100 to obtain a LiOH solution.

[0013] WO 2024 / 089394 A2 describes a process for producing LiOH monohydrate or anhydrous LiOH from lithium mica. In step ix) of the document, a carbonate source is added to a lithium-containing solution to obtain a Li2CO3-containing suspension, which is filtered to obtain a first waste solution and Ü2CO3. In step x), the Li2CO3 in water is converted to LiOH by adding Ca(OH)2. This step x) preferably comprises dissolving Li2CO3 in water by introducing CO2 into this solution to produce LiHCO3, and subsequently adding Ca(OH)2 to obtain a LiOH-containing suspension. This suspension is then filtered to obtain a CaCO3-containing filter cake and a LiOH-containing solution.

[0014] Habashi Fathi, Handbook of Extractive Metallurgy, 1997, page 2045, and Wietelmann Ulrich et al., UHmann's Encyclopedia of Industrial Chemistry, 2000, page 354, each describe a process for the production of LiOH starting from Li2COs. In this process, Li2COs is reacted with CO2 in water to form LiHCOs, and the aqueous LiHCOs solution is then heated to obtain Li2COs and CO2. A further reaction of Li2COs with Ca(OH)2 to form LiOH is also described. CN 111635999 A describes a process for the extraction of lithium from lithium-containing brines. In a first step, lithium ions are extracted from the lithium-containing brine using an extractant, and the upper extraction phase is separated. Preferred extractants include alkyl phosphates, cyclohexanone, and n-butanol. In a second step, the upper extraction phase is mixed with water and CO2 to obtain an aqueous LiHCOs solution.Finally, Ca(OH)2 is added to obtain LiOH.

[0015] Although numerous processes for producing lithium hydroxide from spodumene already exist, there is still a need for further optimization of the process. To meet the increasing demand for high-purity lithium hydroxide for battery production, the following points in particular must be considered:

[0016] Production of lithium hydroxide with consistently high purity, which allows the production of powerful and long-lasting batteries

[0017] Optimization of manufacturing processes with regard to the use of energy and raw materials

[0018] DETAILED DESCRIPTION

[0019] Therefore, it was an object of the present invention to provide a new, more efficient and environmentally friendly process for treating lithium-containing minerals to obtain lithium hydroxide of high purity.

[0020] It was found that the introduction of carbon dioxide into a lithium carbonate-containing suspension lowers the pH of the liquid phase from 10-11 to approximately 7.5. This results in a pH change from basic to neutral without the need for the use of extraneous substances. This results in the formation of more soluble lithium bicarbonate, which remains in the aqueous phase. Impurities that are soluble in alkaline solutions can be precipitated under these conditions and separated with the suspended analcime. Furthermore, it is not expected that heavy metals, which can be dissolved in acidic media, will be dissolved from the solid under these conditions. Therefore, contamination of the lithium-containing solution by such compounds does not occur.

[0021] Furthermore, it was surprisingly found that, independently of each other, the pH value of the lithium carbonate-containing suspension before the introduction of carbon dioxide, as well as the temperature during the subsequent treatment of the mixture with carbonic acid, allow a considerable additional optimization of the process according to the invention.

[0022] Furthermore, this reaction procedure allows the analcime to be separated from the reaction mixture before the alkaline earth hydroxide is added. Therefore, the analcime solid is separated under gentle conditions before the reaction conditions become strongly basic. This avoids undesirable side reactions that occur when analcime reacts with the alkaline earth hydroxide.

[0023] By introducing carbon dioxide, the resulting change in pH, and the transfer of lithium species into the aqueous phase, impurities can be separated more efficiently, or their formation is prevented from the outset. Therefore, the described invention makes a significant contribution to improving the purity of the final product, lithium hydroxide. Furthermore, the range of raw materials (i.e., lithium ores of different origins) is expanded, as accompanying substances can be separated more efficiently in alternating weight proportions.

[0024] Surprisingly, it was discovered that the early separation of analcime can prevent undesirable side reactions between analcime and the alkaline earth metal. Furthermore, it was discovered that the separation of analcime in the neutral pH range can remove impurities that are soluble in alkaline solutions. Furthermore, it was unexpectedly discovered that the temperature at which the subsequent treatment with an alkaline earth metal hydroxide takes place has a significant influence on the amount of impurities in the resulting LiOH solution. In particular, it is an object of the present invention to provide a process for obtaining lithium hydroxide with high yield and high purity.

[0025] The present invention relates to a process for the production of LiOH comprising

[0026] (1 ) Providing a mixture A containing Li2COs;

[0027] (2) treating the mixture A provided in (1) with carbonic acid with at least partial conversion of the Li2COs contained therein to LiHCOs and obtaining a mixture B containing LiHCOs;

[0028] (3) thermal conversion of at least part of the mixture B obtained in (2) and obtaining a mixture C containing Li2COs;

[0029] (4) Reaction of the mixture C obtained in (3) with M(OH)2 with at least partial conversion of the Li2CO contained therein to LiOH and obtaining a mixture D containing LiOH, where M stands for an alkaline earth metal.

[0030] It is preferred that the Li2CO3 content of the mixture in A in (1) is in the range from 0.1 to 16.0 wt.%, preferably in the range from 5 to 12 wt.%, alternatively and particularly preferably in the range from 1 to 5 wt.%. It is further preferred that the Li2CO3 content of the mixture A in (1), based on the solids content of the mixture A, is in the range from 0.1 to 16.0 wt.%, particularly preferably in the range from 5 to 12 wt.%.

[0031] It is preferred that the Li content of the mixture in A in (1), calculated as elemental lithium, is in the range from 0.10 to 3.00 wt.%, preferably in the range from 0.80 to 2.25 wt.%, alternatively and particularly preferably in the range from 0.30 to 2.25 wt.%. It is further preferred that the Li content of the mixture A in (1), calculated as elemental lithium and based on the solids content of the mixture A, is in the range from 0.10 to 3.00 wt.%, particularly preferably in the range from 0.80 to 2.25 wt.%.

[0032] Alternatively, it is preferred that the mixture A further comprises water, and the water content of the mixture A in (1) is in the range of 50 to 90 wt.%, preferably in the range of 60 to 70 wt.%. Furthermore, it is preferred that the Li2CO3 content of the mixture A in (1) is in the range of 0.01 to 8.0 wt.%, preferably in the range of 1 to 5 wt.%.

[0033] It is preferred that the provision of the mixture A according to (1) comprises

[0034] (1 .a) providing a mixture MO containing one or more lithium-containing minerals;

[0035] (1 .b) calcining the mixture MO to obtain a mixture M1 containing one or more calcined lithium-containing minerals;

[0036] (1 .c) reacting the mixture M1 obtained in (b) with an alkali metal carbonate, with at least partial conversion of the one or more calcined lithium-containing minerals to U2CO3 and obtaining a mixture A containing U2CO3.

[0037] In case the process comprises steps (1.a) to (1.c), it is preferred that the mixture MO contains one or more lithium-containing minerals in the range of 50 to 100 wt.%, preferably in the range of 60 to 95 wt.%.

[0038] Furthermore, it is preferred that the one or more lithium-containing minerals are selected from the group consisting of spodumene, petalite, lepidolite or mixtures thereof, wherein the one or more lithium-containing minerals are preferably spodumene, wherein the one or more lithium-containing minerals are particularly preferably alpha-spodumene.

[0039] Furthermore, it is preferred that during the calcination in (1.b) the temperature is in the range of 800 to 1500 °C, preferably in the range of 950 to 1100 °C.

[0040] Furthermore, it is preferred that the calcination in (1.b) is carried out for a period of time in the range of 0.1 to 16 h, preferably in the range of 0.5 to 5 h.

[0041] Furthermore, it is preferred that the one or more calcined lithium-containing minerals are selected from the group consisting of spodumene, petalite, lepidolite, or mixtures thereof, wherein the one or more calcined lithium-containing minerals are preferably spodumene, with the one or more calcined lithium-containing minerals particularly preferably being beta-spodumene. Furthermore, it is preferred that the alkali metal carbonate is selected from the group consisting of sodium carbonate, potassium carbonate, or mixtures thereof, with the alkali metal carbonate preferably being sodium carbonate.

[0042] Furthermore, it is preferred that the weight ratio of the one or more calcined lithium-containing minerals to alkali metal carbonate in (1.c) is in the range of 1:0.1 to 1:2, preferably in the range of 1:0.1 to 1:0.4.

[0043] Furthermore, it is preferred that the molar ratio of lithium to sodium, calculated as elemental lithium and sodium, in (1.c) is in the range from 1:0.4 to 1:8, preferably in the range from 1:0.9 to 1:1.6.

[0044] Furthermore, it is preferred that during the reaction in (1.c) the temperature is in the range of 150 to 350°C, preferably in the range of 200 to 250°C.

[0045] Furthermore, it is preferred that during the reaction in (1.c) the pressure is in the range from 10 to 200 bar (absolute), preferably in the range from 14 to 50 bar (absolute), more preferably in the range from 20 to 50 bar (absolute).

[0046] Furthermore, it is preferred that the reaction in (1.c) is carried out for a period of time in the range of 0.1 to 8 h, preferably in the range of 0.5 to 1.5 h.

[0047] Furthermore, it is preferred that the reaction in (1.c) comprises water, preferably aqueous alkali carbonate solution.

[0048] Furthermore, it is preferred that the method comprises

[0049] (1 .d) separating at least a portion of the unreacted alkali metal carbonate from the mixture A obtained in (1 .c) and obtaining a mixture M2 containing unreacted alkali metal carbonate;

[0050] (1 .e) Providing the mixture M2 for the reaction in (1 .c) as a source of alkali metal carbonate.

[0051] Alternatively, it is preferred that the provision of the mixture A according to (1) comprises (1.a') providing a mixture M0' containing one or more lithium-containing minerals; (1,b') reacting the mixture M0' with an alkali metal carbonate to at least partially convert the one or more lithium-containing minerals to Li2CO3 and obtain a mixture A containing Li2CO3. In the case where the process comprises steps (1,a') and (1,b'), it is preferred that the mixture M0' contains the one or more lithium-containing minerals in the range of 50 to 100 wt.%, preferably in the range of 60 to 95 wt.%.

[0052] Furthermore, it is preferred that the Li content of the mixture M0', calculated as elemental lithium, is in the range of 0.03 to 4.0 wt.%, preferably in the range of 2.00 to 3.75 wt.%.

[0053] Furthermore, it is preferred that the one or more lithium-containing minerals are selected from the group consisting of spodumene, petalite, lepidolite or mixtures thereof, wherein the one or more lithium-containing minerals are preferably spodumene, wherein the one or more lithium-containing minerals are particularly preferably alpha-spodumene.

[0054] Furthermore, it is preferred that the alkali metal carbonate is selected from the group consisting of sodium carbonate, potassium carbonate or mixtures thereof, wherein the alkali metal carbonate is preferably sodium carbonate.

[0055] Furthermore, it is preferred that in (1,b') the weight ratio of the one or more lithium-containing minerals to alkali metal carbonate is in the range from 1:0.1 to 1:2, preferably in the range from 1:0.2 to 1:0.4.

[0056] Furthermore, it is preferred that the molar ratio of lithium to sodium, calculated as elemental lithium and sodium, in (1.b') is in the range from 1:0.4 to 1:8, preferably in the range from 1:0.9 to 1:1.4.

[0057] Furthermore, it is preferred that the reaction in (1.b') is carried out for a period of time in the range of 0.1 to 10 h, preferably in the range of 1 to 4 h.

[0058] Furthermore, it is preferred that the reaction in (1,b') comprises water, preferably steam. If the reaction in (1,b') comprises water, it is preferred that the pressure during the reaction in (1,b') is in the range from 10 to 200 bar (absolute), preferably in the range from 14 to 180 bar (absolute), further preferably in the range from 14 to 50 bar (absolute), particularly preferably in the range from 20 to 50 bar (absolute).

[0059] In case the process comprises steps (1,a') and (1,b'), it is preferred that the reaction in (1.b') comprises

[0060] (1.b'.1) Calcining the mixture M0' and an alkali metal carbonate, and obtaining a mixture M1'; (1,b'.2) Reacting the mixture MT obtained in (1,b'.1), and obtaining a mixture A containing U2CO3.

[0061] If the process comprises steps (1.b'.1) and (1.b'.2), it is preferred that during the calcination in (1.b'.1) the temperature is in the range from 900 to 1500 °C, preferably in the range from 1000 to 1200 °C. Furthermore, it is preferred that the reaction in (1.b'.2) comprises water, preferably steam. If the reaction in (1.b') comprises water, it is preferred that during the reaction in (1.b'.2) the pressure is in the range from 10 to 200 bar (absolute), preferably in the range from 14 to 180 bar (absolute), further preferably in the range from 14 to 50 bar (absolute), particularly preferably in the range from 20 to 50 bar (absolute).

[0062] In case the method comprises steps (1.a') and (1.b'), it is preferred that the method comprises

[0063] (1.c') Separating unreacted alkali metal carbonate from the mixture A contained in (1.b') and obtaining a mixture M2' containing unreacted alkali metal carbonate; (1.d') Providing the mixture M2' for the reaction in (1.b') as a source of alkali metal carbonate.

[0064] It is preferred that during the treatment in (2) the temperature is in the range of 0 to 150 °C, more preferably in the range of 15 to 100 °C, more preferably in the range of 20 to 80 °C, more preferably in the range of 25 to 70 °C, more preferably in the range of 30 to 60 °C, more preferably in the range of 35 to 50 °C, particularly preferably in the range of 40 to 45 °C.

[0065] It is preferred that the treatment in (2) takes place in aqueous solution and CO2 is introduced into the aqueous solution.

[0066] In case that the treatment in (2) takes place in aqueous solution and CO2 is introduced into the aqueous solution, it is preferred that the aqueous solution before the introduction of CO2 has a pH in the range from 9 to 13, more preferably from 10 to 12.5, more preferably from 10.5 to 12, particularly preferably from 11 to 11.5.

[0067] Furthermore, it is preferred that the pH of the aqueous solution is adjusted prior to the introduction of CO2 by adding acid and / or base. In this case, it is preferred that the base contains one or more hydroxide salts, wherein the base preferably contains one or more alkali metal hydroxide salts, wherein the base preferably contains NaOH. In particular, it is preferred that the base consists of one or more hydroxide salts, wherein the base preferably consists of one or more alkali metal hydroxide salts, wherein the base is preferably NaOH. Irrespective of this, when adjusting the pH by adding acid, it is preferred that the acid contains one or more Bronsted acids, wherein the acid preferably contains one or more mineral acids, wherein the acid preferably contains H2SO4 and / or HCl, wherein the acid preferably contains H2SO4.In particular, it is preferred that the acid consists of one or more Bronsted acids, wherein the acid preferably consists of one or more mineral acids, wherein the acid preferably consists of H2SO4 and / or HCl, wherein the acid preferably consists of H2SO4.

[0068] Furthermore, it is alternatively preferred that the pH of the aqueous solution is not adjusted by adding acid and / or base before the introduction of CO2, wherein the pH of the aqueous solution is not adjusted before the introduction of CO2.

[0069] Furthermore, it is preferred that the aqueous solution has a pH value in the range of

[0070] 9 to 13 and during the treatment in (2) the temperature is in the range from 25 to 70 °C, wherein more preferably the aqueous solution has a pH in the range from 10 to 12.5 before the introduction of CO2 and the temperature is in the range from 30 to 60 °C during the treatment in (2), wherein more preferably the aqueous solution has a pH in the range from 10.5 to 12 before the introduction of CO2 and the temperature is in the range from 35 to 50 °C during the treatment in (2), wherein particularly preferably the aqueous solution has a pH in the range from 11 to 11.5 before the introduction of CO2 and the temperature is in the range from 40 to 45 °C during the treatment in (2).

[0071] Furthermore, it is preferred that CO2 be introduced into the aqueous solution at a pressure of 1 to 15 bar (absolute), more preferably 1 to 10 bar (absolute), more preferably 3 to 8 bar (absolute), particularly preferably 5 to 6 bar (absolute). According to the present invention, the pressure of the CO2 indicates the partial pressure at which CO2 is introduced into the aqueous solution, wherein the partial pressure corresponds to the total pressure of the gas stream when CO2 is introduced into the aqueous solution in pure form.

[0072] It is preferred that the treatment in (2) comprises

[0073] (2.1) Treatment of the mixture A provided in (1) with carbonic acid with at least partial conversion of the Ü2CO3 contained therein to LiHCOs;

[0074] (2.2) Solid-liquid separation step of the mixture obtained in (2.1), and obtaining a solid mixture M4 containing unreacted U2CO3 and a liquid mixture B containing UHCO3. In case the process comprises steps (2.1) and (2.2), it is preferred that the treatment in (2) further comprises

[0075] (2.3) Provision of the mixture M4 for the treatment in (2) as a source of Li2CO3.

[0076] It is preferred that the treatment in (2.3) comprises

[0077] (2.3.1) Washing the solid mixture M4 obtained in (2.2) with water and obtaining wash water containing Li2CO3;

[0078] (2.3.2) Providing at least part of the wash water containing U2CO3 obtained in (2.3.1) for thermal conversion in (3).

[0079] Regardless, it is preferred that the treatment in (2.3) includes

[0080] (2.3.1) Washing the solid mixture M4 obtained in (2.2) with water and obtaining wash water containing IJ2CO3;

[0081] (2.3.2) Providing at least part of the wash water containing U2CO3 obtained in (2.3.1) for the treatment with carbonic acid in (2).

[0082] It is preferred that the pH of the mixture B obtained in (2) is in the range from 5 to 9, preferably from 5 to 8.5, more preferably in the range from 6 to 8.5, more preferably in the range from 7 to 8.5, more preferably in the range from 7 to 8, particularly preferably in the range from 7.5 to 8.

[0083] It is preferred that the mixture B obtained in (2) contains less than 30.0 wt.% alkaline earth metals, preferably less than 20.0 wt.% alkaline earth metals, more preferably less than 10.0 wt.% alkaline earth metals, more preferably less than 5.0 wt.% alkaline earth metals, more preferably less than 3.0 wt.% alkaline earth metals, more preferably less than 1.0 wt.% alkaline earth metals, wherein the mixture B obtained in (2) is particularly preferably free of alkaline earth metals.

[0084] It is preferred that the mixture B obtained in (2) contains less than 5.0 wt.% calcium, calculated as elemental calcium, preferably less than 3.0 wt.% calcium, particularly preferably less than 1.0 wt.% calcium, wherein the mixture B obtained in (2) is particularly preferably free of calcium.

[0085] It is preferred that during the thermal conversion in (3) the temperature is in the range of 50 to 200 °C, preferably in the range of 70 to 150 °C, particularly preferably in the range of 70 to 110 °C.

[0086] It is preferred that during the thermal conversion in (3) the pressure is in the range from 0.1 to 10 bar (absolute), preferably in the range from 0.2 to 6 bar (absolute), particularly preferably in the range from 0.3 to 1 bar (absolute). It is preferred that the reaction in (3) further comprises

[0087] (3.1) Reaction of a part of the mixture B obtained in (2) with M(OH)2 with at least partial conversion of the LiHCO contained therein to LiOH and obtaining a mixture D' containing LiOH, where M is an alkaline earth metal.

[0088] It is preferred that the reaction in (4) comprises

[0089] (4.1 ) Solid-liquid separation step of the mixture C obtained in (4) and obtaining a suspension containing solid Li2COs and a solution containing Li2COs;

[0090] (4.2) providing at least a portion of the solution containing Li2COs obtained in (4.1) for the treatment with carbonic acid in (2);

[0091] (4.3) Reaction of the suspension obtained in (4.1) containing solid Li2COs with M(OH)2 with at least partial conversion of the Li2COs contained therein to LiOH and obtaining a mixture D containing LiOH, where M stands for an alkaline earth metal.

[0092] In case the process comprises step (4.1), it is preferred that the solids content of the suspension obtained in (4.1) containing solid Ü2CO3 is in the range of 1 to 10 wt.%, more preferably in the range of 3 to 9 wt.%, particularly preferably in the range of 4 to 8 wt.%.

[0093] In case the process comprises step (4.1), it is preferred that the solid-liquid separation step in (4.1) is carried out by cross-flow filtration of the mixture C obtained in (3).

[0094] It is preferred that, independently of one another, during the reaction in (4) and / or (3.1), the temperature is in the range from 10 to 100°C, more preferably in the range from 15 to 80°C, more preferably in the range from 20 to 60°C, more preferably in the range from 20 to 50°C, more preferably in the range from 25 to 45°C, more preferably in the range from 30 to 45°C, more preferably in the range from 35 to 45°C, particularly preferably in the range from 38 to 42°C.

[0095] °C. Furthermore, it is preferred that, independently of one another, during the reaction in (4) and / or (3.1), the pressure is in the range from 0.5 to 1.5 bar (absolute), preferably in the range from 0.8 to 1.2 bar (absolute).

[0096] It is preferred that during the thermal conversion in (3) the temperature is in the range of 50 to 200 °C, preferably in the range of 70 to 150 °C, particularly preferably in the range of 70 to 110 °C.

[0097] It is preferred that during the thermal conversion in (3) the pressure is in the range of 0.1 to 10 bar (absolute), preferably in the range of 0.2 to 6 bar (absolute), particularly preferably in the range of 0.3 to 1 bar (absolute).

[0098] It is preferred that, independently of one another, the alkaline earth metal hydroxide M(OH)2 used in (4) and / or in (3.1) is dissolved or suspended in water before the reaction. If the alkaline earth metal hydroxide M(OH)2 used in (4) and / or (3.1) is dissolved or suspended in water before the reaction, it is preferred that, independently of one another, the weight fraction of alkaline earth metal hydroxide M(OH)2 in the aqueous solution or the aqueous suspension is in the range of 1 to 50 wt. %, preferably in the range of 10 to 30 wt. %.

[0099] It is preferred that, independently of one another, the alkaline earth metal M in (4) and / or in (3.1) is selected from the group consisting of barium, calcium and magnesium, wherein the alkaline earth metal M is preferably calcium.

[0100] It is preferred that the method further comprises

[0101] (5) Separation of MCO3 from the mixture D obtained in (4) and / or the mixture D' obtained in (3.1) to obtain a mixture E containing LiOH.

[0102] It is preferred that the separation in (5) comprises

[0103] (5.1) Solid-liquid separation step of the mixture D obtained in (4) and / or the mixture D' obtained in (3.1) and obtaining a solid mixture M5 containing CaCOs and a liquid mixture E containing LiOH;

[0104] (5.2) Washing the solid mixture M5 obtained in (5.1) with water and obtaining wash water containing LiOH,

[0105] (5.3) Providing at least a portion of the wash water containing LiOH obtained in (5.2) for the reaction in (4), wherein at least a portion of the wash water containing LiOH is preferably admixed with alkaline earth metal hydroxide M(OH)2 before being recycled to (4). The wash water containing LiOH obtained in (5.2) thus serves to prepare the aqueous suspension of the alkaline earth metal hydroxide M(OH)2 that is used for the reaction in (4) and is thus recycled to (4).

[0106] In case the process comprises steps (5.1) to (5.3), it is preferred that the separation in (5) further comprises an ion exchange, preferably a cationic ion exchange.

[0107] The present invention is further explained by the following embodiments and combinations of embodiments, which result from the specified dependencies and references. In particular, it is pointed out that in each case in which a range of embodiments is mentioned, e.g., in connection with a term such as "The method of any of embodiments 1 to 4," each embodiment in this range is intended to be explicitly disclosed to the person skilled in the art, i.e., the wording of this term is to be understood by the person skilled in the art as a synonym for "The method of any of embodiments 1, 2, 3, and 4." Furthermore, it is expressly pointed out that the following series of embodiments is not the set of claims determining the scope of protection, but represents a suitably structured part of the description directed to general and preferred aspects of the present invention. 1. A process for producing LIOH comprising

[0108] (1) Providing a mixture A containing Ü2CO3;

[0109] (2) treating the mixture A provided in (1) with carbonic acid to at least partially convert the Li2COs contained therein to LiHCOs and obtaining a mixture B containing LiHCOs;

[0110] (3) thermal conversion of at least part of the mixture B obtained in (2) and obtaining a mixture C containing LisCOs;

[0111] (4) Reaction of the mixture C obtained in (3) with M(OH)2 with at least partial conversion of the LisCO contained therein to LiOH and obtaining a mixture D containing LiOH, where M stands for an alkaline earth metal.

[0112] 2. The process according to embodiment 1, wherein the LisCOs content of the mixture in A in (1) is in the range of 0.1 to 16.0 wt.%, preferably in the range of 5 to 12 wt.%, alternatively and particularly preferably in the range of 1 to 5 wt.%.

[0113] 3. The process according to embodiment 2, wherein the Li2CO3 content of the mixture A in (1), based on the solids content of the mixture A, is in the range from 0.1 to 16.0 wt.%, particularly preferably in the range from 5 to 12 wt.%.

[0114] 4. The process according to embodiment 1 or 2, wherein the Li content of the mixture in A in (1), calculated as elemental lithium, is in the range of 0.10 to 3.00 wt.%, preferably in the range of 0.80 to 2.25 wt.%, alternatively and particularly preferably in the range of 0.30 to 2.25 wt.%.

[0115] 5. The process according to embodiment 4, wherein the Li content of the mixture A in (1), calculated as elemental lithium and based on the solids content of the mixture A, is in the range from 0.10 to 3.00 wt.%, particularly preferably in the range from 0.80 to 2.25 wt.%.

[0116] 6. The process according to embodiment 1, wherein the mixture A further comprises water, and the water content of the mixture A in (1) is in the range of 50 to 90 wt.%, preferably in the range of 60 to 70 wt.%.

[0117] 7. The process according to embodiment 6, wherein the Li2CC>3 content of the mixture A in (1) is in the range of 0.01 to 8.0 wt.%, preferably in the range of 1 to 5 wt.%.

[0118] 8. The process according to any one of embodiments 1 to 7, wherein the provision of the mixture A according to (1) comprises

[0119] (1.a) Providing a mixture of MO containing one or more lithium-bearing minerals;

[0120] (1.b) Calcining the mixture MO to obtain a mixture M1 containing one or more calcined lithium-containing minerals; (1.c) reacting the mixture M1 obtained in (b) with an alkali metal carbonate, at least partially converting the one or more calcined lithium-containing minerals to U2CO3 and obtaining a mixture A containing U2CO3.

[0121] 9. The process according to embodiment 8, wherein the mixture MO contains one or more lithium-containing minerals in the range of 50 to 100 wt.%, preferably in the range of 60 to 95 wt.%.

[0122] 10. The process according to embodiment 8 or 9, wherein the one or more lithium-containing minerals are selected from the group consisting of spodumene, petalite, lepidolite, or mixtures thereof, wherein the one or more lithium-containing minerals are preferably spodumene, wherein the one or more lithium-containing minerals are more preferably alpha-spodumene.

[0123] 11. The process according to any one of embodiments 8 to 10, wherein during the calcination in (1.b) the temperature is in the range from 800 to 1500 °C, preferably in the range from 950 to 1100 °C.

[0124] 12. The process according to any one of embodiments 8 to 11, wherein the calcination in (1.b) is carried out for a period of time in the range of 0.1 to 16 h, preferably in the range of 0.5 to 5 h.

[0125] 13. The process according to any one of embodiments 8 to 12, wherein the one or more calcined lithium-containing minerals are selected from the group consisting of spodumene, petalite, lepidolite, or mixtures thereof, wherein the one or more calcined lithium-containing minerals are preferably spodumene, wherein the one or more calcined lithium-containing minerals are particularly preferably beta-spodumene.

[0126] 14. The process according to any one of embodiments 8 to 13, wherein the alkali metal carbonate is selected from the group consisting of sodium carbonate, potassium carbonate or mixtures thereof, wherein the alkali metal carbonate is preferably sodium carbonate.

[0127] 15. The process according to any one of embodiments 8 to 14, wherein the weight ratio of the one or more calcined lithium-containing minerals to alkali metal carbonate in (1.c) is in the range of 1:0.1 to 1:2, preferably in the range of 1:0.1 to 1:0.4.

[0128] 16. The process according to any one of embodiments 8 to 15, wherein the molar ratio of lithium to sodium, calculated as elemental lithium and sodium, in (1.c) is in the range from 1:0.4 to 1:8, preferably in the range from 1:0.9 to 1:1.6. 17. The process according to any one of embodiments 8 to 16, wherein during the reaction in (1.c) the temperature is in the range from 150 to 350°C, preferably in the range from 200 to 250°C.

[0129] 18. The process according to any one of embodiments 8 to 17, wherein during the reaction in (1.c) the pressure is in the range from 10 to 200 bar (absolute), more preferably in the range from 20 to 50 bar (absolute), preferably in the range from 14 to 50 bar (absolute).

[0130] 19. The process according to any one of embodiments 8 to 18, wherein the reaction in (1.c) is carried out for a period of time in the range from 0.1 to 8 h, preferably in the range from 0.5 to 1.5 h.

[0131] 20. The process according to any one of embodiments 8 to 19, wherein the reaction in (1.c) comprises water, preferably aqueous alkali carbonate solution.

[0132] 21 . The method according to any one of embodiments 8 to 20, comprising

[0133] (1 .d) separating at least a portion of the unreacted alkali metal carbonate from the mixture A obtained in (1 .c) and obtaining a mixture M2 containing unreacted alkali metal carbonate;

[0134] (1 .e) Providing the mixture M2 for the reaction in (1 .c) as a source of alkali metal carbonate.

[0135] 22. The process according to any one of embodiments 1 to 7, wherein the provision of the mixture A according to (1) comprises

[0136] (1.a') providing a mixture M0' containing one or more lithium-containing minerals;

[0137] (1,b') reacting the mixture M0' with an alkali metal carbonate with at least partial conversion of the one or more lithium-containing minerals to I^COs and obtaining a mixture A containing Li2CO3.

[0138] 23. The process according to embodiment 22, wherein the mixture M0' contains the one or more lithium-containing minerals in the range of 50 to 100 wt.%, preferably in the range of 60 to 95 wt.%.

[0139] 24. The process according to embodiment 22 or 23, wherein the Li content of the mixture M0', calculated as elemental lithium, is in the range of 0.03 to 4.0 wt.%, preferably in the range of 2.00 to 3.75 wt.%.

[0140] 25. The process according to any one of embodiments 22 to 24, wherein the one or more lithium-containing minerals are selected from the group consisting of spodumene, petalite, lepidolite, or mixtures thereof, wherein the one or more lithium-containing minerals are preferably spodumene, wherein the one or more lithium-containing minerals are more preferably alpha-spodumene.

[0141] 26. The process according to any one of embodiments 22 to 25, wherein the alkali metal carbonate is selected from the group consisting of sodium carbonate, potassium carbonate or mixtures thereof, wherein the alkali metal carbonate is preferably sodium carbonate.

[0142] 27. The process according to any one of embodiments 22 to 26, wherein in (1,b') the weight ratio of the one or more lithium-containing minerals to alkali metal carbonate is in the range from 1:0.1 to 1:2, preferably in the range from 1:0.2 to 1:0.4.

[0143] 28. The process according to any one of embodiments 22 to 27, wherein the molar ratio of lithium to sodium, calculated as elemental lithium and sodium, in (1.b') is in the range from 1:0.4 to 1:8, preferably in the range from 1:0.9 to 1:1.4.

[0144] 29. The process according to any one of embodiments 22 to 28, wherein the reaction in

[0145] (1,b') is carried out for a period of time in the range of 0.1 to 10 h, preferably in the range of 1 to 4 h.

[0146] 30. The process according to any one of embodiments 22 to 29, wherein the reaction in (1.b') comprises water, preferably steam.

[0147] 31. The process according to embodiment 30, wherein during the reaction in (1,b') the pressure is in the range from 10 to 200 bar (absolute), preferably in the range from 14 to 180 bar (absolute), further preferably in the range from 14 to 50 bar (absolute), particularly preferably in the range from 20 to 50 bar (absolute).

[0148] 32. The process according to any one of embodiments 22 to 29, wherein the reaction in (1,b') comprises

[0149] (1.b'.1) Calcining the mixture M0' and an alkali metal carbonate, and obtaining a mixture M1 ';

[0150] (1 ,b'.2) Conversion of the mixture M1 ' obtained in (1 ,b'.1 ) and obtaining a mixture A containing Li2COs.

[0151] 33. The process according to embodiment 32, wherein during the calcination in (1 . b' .1 ) the temperature is in the range from 900 to 1500 °C, preferably in the range from 1000 to 1200 °C.

[0152] 34. The process according to embodiment 32 or 33, wherein the reaction in (1,b'.2) comprises water, preferably steam. The process according to embodiment 34, wherein during the reaction in (1,b'.2) the pressure is in the range from 10 to 200 bar (absolute), preferably in the range from 14 to 180 bar (absolute), further preferably in the range from 14 to 50 bar (absolute), particularly preferably in the range from 20 to 50 bar (absolute). The process according to any one of embodiments 22 to 35, comprising

[0153] (1,c') separating unreacted alkali metal carbonate from the mixture A contained in (1,b') and obtaining a mixture M2' containing unreacted alkali metal carbonate;

[0154] (1,d') Providing the mixture M2' for the reaction in (1,b') as a source of alkali metal carbonate. The process according to any one of embodiments 1 to 36, wherein during the treatment in (2) the temperature is in the range from 0 to 150 °C, preferably in the range from 15 to 100 °C, more preferably in the range from 20 to 80 °C, more preferably in the range from 25 to 70 °C, more preferably in the range from 30 to 60 °C, more preferably in the range from 35 to 50 °C, particularly preferably in the range from 40 to 45 °C. The process according to any one of embodiments 1 to 37, wherein the treatment in (2) takes place in aqueous solution and CO2 is introduced into the aqueous solution. The process according to embodiment 38, wherein the aqueous solution before the introduction of CO2 has a pH in the range from 9 to 13, preferably from 10 to 12.5, more preferably from 10.5 to 12, particularly preferably from 11 to 11.5.The process according to embodiment 39, wherein the pH of the aqueous solution is adjusted by adding acid and / or base before introducing CO2. The process according to embodiment 40, wherein the base contains one or more hydroxide salts, wherein the base preferably contains one or more alkali metal hydroxide salts, wherein the base preferably contains NaOH. The process according to embodiment 41, wherein the base consists of one or more hydroxide salts, wherein the base preferably consists of one or more alkali metal hydroxide salts, wherein the base is preferably NaOH. The process according to any one of embodiments 40 to 42, wherein the acid contains one or more Bronsted acids, wherein the acid preferably contains one or more mineral acids, wherein the acid preferably contains H2SO4 and / or HCl, wherein the acid preferably contains H2SO4.The process according to embodiment 43, wherein the acid consists of one or more Bronsted acids, wherein the acid preferably consists of one or more mineral acids, wherein the acid preferably consists of H2SO4 and / or HCl, wherein the acid preferably consists of H2SO4. The process according to embodiment 39, wherein the pH of the aqueous solution is not adjusted by adding acid and / or base before introducing CO2, wherein the pH of the aqueous solution is not adjusted before introducing CO2. The process according to any one of embodiments 39 to 45, wherein the aqueous solution has a pH in the range of before introducing CO2.

[0155] 9 to 13 and during the treatment in (2) the temperature in the range of

[0156] 25 to 70 °C, wherein preferably the aqueous solution has a pH in the range from 10 to 12.5 before the introduction of CO2 and the temperature during the treatment in (2) is in the range from 30 to 60 °C, wherein more preferably the aqueous solution has a pH in the range from 10.5 to 12 before the introduction of CO2 and the temperature during the treatment in (2) is in the range from 35 to 50 °C, wherein particularly preferably the aqueous solution has a pH in the range from 11 to 11.5 before the introduction of CO2 and the temperature during the treatment in (2) is in the range from 40 to 45 °C. The process according to any one of embodiments 38 to 46, wherein CO2 is introduced into the aqueous solution at a pressure of 1 to 15 bar (absolute), preferably 1 to 10 bar (absolute), more preferably 3 to 8 bar (absolute), particularly preferably 5 to 6 bar (absolute). The process according to any one of embodiments 1 to 47, wherein the treatment in (2) comprises

[0157] (2.1) Treatment of the mixture A provided in (1 ) with carbonic acid with at least partial conversion of the Li2COs contained therein to LiHCOs;

[0158] (2.2) Solid-liquid separation step of the mixture obtained in (2.1), and obtaining a solid mixture M4 containing unreacted Ü2CO3 and a liquid mixture B containing LiHCO3. The process according to embodiment 48, wherein the treatment in (2) further comprises

[0159] (2.3) Providing the mixture M4 for the treatment in (2) as a source of O2CO3. The process according to embodiment 49, wherein the treatment in (2.3) comprises

[0160] (2.3.1 ) Washing the solid mixture M4 obtained in (2.2) with water and obtaining wash water containing Ü2CO3;

[0161] (2.3.2) Providing at least a portion of the wash water containing Li2CO3 obtained in (2.3.1) for the reaction in (3). The process according to embodiment 49 or 50, wherein the treatment in (2.3) comprises

[0162] (2.3.1) Washing the solid mixture M4 obtained in (2.2) with water and obtaining wash water containing Li2CO3;

[0163] (2.3.2) Providing at least a portion of the wash water containing U2CO3 obtained in (2.3.1) for the treatment with carbonic acid in (2). The process according to any one of embodiments 1 to 51, wherein the pH of the mixture B obtained in (2) is in the range from 5 to 9, preferably from 5 to 8, preferably in the range from 6 to 8.5, further preferably in the range from 7 to 8.5, further preferably in the range from 7 to 8, particularly preferably in the range from 7.5 to 8. The process according to any one of embodiments 1 to 52, wherein the mixture B obtained in (2) contains less than 30.0 wt.% alkaline earth metals, preferably less than 20.0 wt.% alkaline earth metals, more preferably less than 10.0 wt.% alkaline earth metals, more preferably less than 5.0 wt.% alkaline earth metals, more preferably less than 3.0 wt.% alkaline earth metals, more preferably less than 1.0 wt.% alkaline earth metals, wherein the mixture B obtained in (2) is particularly preferably free of alkaline earth metals.The process according to any one of embodiments 1 to 53, wherein the mixture B obtained in (2) contains less than 5.0 wt.% calcium, calculated as elemental calcium, preferably less than 3.0 wt.% calcium, particularly preferably less than 0.1.0 wt.% calcium, wherein the mixture B obtained in (2) is particularly preferably free of calcium. The process according to any one of embodiments 1 to 54, wherein during the thermal conversion in (3) the temperature is in the range from 50 to 200 °C, preferably in the range from 70 to 150 °C, particularly preferably in the range from 70 to 110 °C. The process according to any of embodiments 1 to 55, wherein during the thermal conversion in (3), the pressure is in the range from 0.1 to 10 bar (absolute), preferably in the range from 0.2 to 6 bar (absolute), particularly preferably in the range from 0.3 to 1 bar (absolute). The process according to any of embodiments 1 to 56, wherein the reaction in (3) further comprises.

[0164] (3.1) Reacting a portion of the mixture B obtained in (2) with M(OH)2 with at least partial conversion of the UHCO3 contained therein to LiOH, and obtaining a mixture D' containing LiOH, where M is an alkaline earth metal. The process according to any one of embodiments 1 to 57, wherein the reaction in (4) comprises (4.1) a solid-liquid separation step of the mixture C obtained in (4) and obtaining a suspension containing solid U2CO3 and a solution containing Li2CO3;

[0165] (4.2) providing at least a portion of the solution containing Li2CC>3 obtained in (4.1) for the treatment with carbonic acid in (2);

[0166] (4.3) Reaction of the suspension obtained in (4.1) containing solid Li2CC>3 with M(OH)2 with at least partial conversion of the Li2CC>3 contained therein to LiOH and obtaining a mixture D containing LiOH, where M is an alkaline earth metal.

[0167] 59. The process according to embodiment 58, wherein the solids content of the suspension obtained in (4.1) containing solid Li2COs is in the range from 1 to 10 wt.%, preferably in the range from 3 to 9 wt.%, particularly preferably in the range from 4 to 8 wt.%.

[0168] 60. The process according to embodiment 58 or 59, wherein the solid-liquid separation step in (4.1) is carried out by cross-flow filtration of the mixture C obtained in (3).

[0169] 61 . The process according to any one of embodiments 1 to 60, wherein, independently of one another, during the reaction in (4) and / or (3.1), the temperature is in the range from 10 to 100 °C, preferably in the range from 15 to 80 °C, further preferably in the range from 20 to 60 °C, further preferably in the range from 20 to 50 °C, further preferably in the range from 25 to 45 °C, further preferably in the range from 30 to 45 °C, further preferably in the range from 35 to 45 °C, particularly preferably in the range from 38 to 42 °C.

[0170] 62. The process according to any one of embodiments 1 to 61, wherein, independently of one another, during the reaction in (4) and / or (3.1), the pressure is in the range from 0.5 to 1.5 bar (absolute), preferably in the range from 0.8 to 1.2 bar (absolute).

[0171] 63. The process according to any one of embodiments 1 to 62, wherein during the thermal conversion in (3) the temperature is in the range from 50 to 200 °C, preferably in the range from 70 to 150 °C, particularly preferably in the range from 70 to 110 °C.

[0172] 64. The process according to any one of embodiments 1 to 63, wherein during the thermal conversion in (3) the pressure is in the range from 0.1 to 10 bar (absolute), preferably in the range from 0.2 to 6 bar (absolute), particularly preferably in the range from 0.3 to 1 bar (absolute).

[0173] 65. The process according to any of embodiments 1 to 64, wherein, independently of one another, the alkaline earth metal hydroxide M(OH)2 used in (4) and / or in (3.1) is dissolved or suspended in water (4) and / or (3.1) before the reaction. 66. The process according to embodiment 65, wherein, independently of one another, the weight fraction of alkaline earth metal hydroxide M(OH)2 in the aqueous solution or the aqueous suspension is in the range from 1 to 50 wt. %, preferably in the range from 10 to 30 wt. %.

[0174] 67. The process according to any one of embodiments 1 to 66, wherein, independently of one another, the alkaline earth metal M in (4) and / or in (3.1) is selected from the group consisting of barium, calcium and magnesium, wherein the alkaline earth metal M is preferably calcium.

[0175] 68. The method according to any one of embodiments 1 to 67, the method further comprising

[0176] (5) Separation of MCO3 from the mixture D obtained in (4) and / or the mixture D' obtained in (3.1) to obtain a mixture E containing LiOH.

[0177] 69. The method of embodiment 68, wherein the separation in (5) comprises

[0178] (5.1) Solid-liquid separation step of the mixture D obtained in (4) and / or the mixture D' obtained in (3.1) and obtaining a solid mixture M5 containing CaCOs and a liquid mixture E containing LiOH;

[0179] (5.2) Washing the solid mixture M5 obtained in (5.1) with water and obtaining wash water containing LiOH,

[0180] (5.3) Providing at least a portion of the wash water containing LiOH obtained in (5.2) for the reaction in (4), wherein at least a portion of the wash water containing LiOH is preferably admixed with alkaline earth metal hydroxide M(OH)2 before being recycled to (4).

[0181] 70. The process of embodiment 69, wherein the separation in (5) further comprises an ion exchange, preferably a cationic ion exchange.

[0182] EXPERIMENTAL PART

[0183] As described in the introductory part of the detailed description, it was unexpectedly found that the temperature at which the treatment of the Ü2CO3 with an alkaline earth metal hydroxide takes place has a significant influence on the amount of impurities in the LiOH solution obtained in this step of the inventive process. This effect is demonstrated by the following series of experiments. The reaction of lithium carbonate (Li2CO3) to lithium hydroxide (LiOH) using calcium hydroxide (Ca(OH)2) was investigated at different temperatures. In particular, temperatures of 50 °C, 60 °C, and 95 °C were tested in the series of experiments.

[0184] As further described in the introductory part of the detailed description, it was unexpectedly found that, independently of one another, the pH value of the starting mixture containing U2CO3 and the temperature during the subsequent treatment of the mixture with carbonic acid allowed for considerable additional optimization of the inventive process. These further effects of the inventive process are demonstrated by the following series of experiments. The reaction of lithium carbonate (Li2CO3) to lithium hydrogen carbonate (LiHCOs) was carried out using H2CO3, which was generated in situ by CO2. The CO2 was continuously added during the reaction at a maximum pressure of approximately 5 bar. The series of experiments encompassed various pH values, which were adjusted prior to the addition of CO2. For pH values ​​of 4 and 10.5, 96% sulfuric acid (H2SO4) was used. For pH 13, 50% sodium hydroxide solution (NaOH) was used.For the pH 11 experiment, neither acid nor base had to be added.

[0185] Experimental series for the production of LiOH from Li2CO3

[0186] Example 1 : Reaction of a mixture containing Ü2CO3 with Ca(OH)2 at 40 °C

[0187] In a batch reaction, a Li2CO3 suspension obtained from the thermal decomposition of a LiHCO3 solution from the pressure leach of beta-spodumene according to the present invention was reacted with a suspension of Ca(OH)2 in water at 40 °C under stirring. The procedure was as follows:

[0188] A Li2CO3 suspension (723.6 g; 23 g / L Li2CO3; 16 g O2CO3; 222 mmol Li2CO3) was initially introduced and rendered inert in a nitrogen atmosphere. While stirring, the suspension was heated to the target temperature of 40 °C. In parallel, the previously mixed Ca(OH)2 suspension (97.9 g; 206 g / L Ca(OH)2; 17.2 g Ca(OH)2; 233 mmol Ca(OH)2) was prepared by resuspending it under a nitrogen atmosphere at room temperature. After 14 min, the target temperature of 40 °C was reached, and the addition of Ca(OH)2 was started. The 97.9 g of suspension was added over a period of 30 min. The mixture was then stirred at 40 °C for a further 180 min. The suspension was then removed from the reactor and filtered through a Buchner funnel. The filter cake was washed with 100 g of deionized water.

[0189] Example 2: Reaction of a mixture containing Ü2CO3 with Ca(OH)2 at 95 °C. In a batch reaction, a Li2CC>3 suspension, obtained from the thermal decomposition of a LiHCO3 solution from the pressure leach of beta-spodumene as in Example 1, was reacted with a suspension of Ca(OH)2 in water at 95 °C while stirring. The procedure was as follows:

[0190] A Li2CO3 suspension (704.2 g; 24 g / L Li2CO3; 17 g O2CO3; 224 mmol Li2CO3) was initially introduced and rendered inert in a nitrogen atmosphere. While stirring, the suspension was heated to the target temperature of 95 °C. In parallel, the previously mixed Ca(OH)2 suspension (96.5 g; 206 g / L Ca(OH)2; 17.3 g Ca(OH)2; 234 mmol Ca(OH)2) was prepared by resuspending it under a nitrogen atmosphere at room temperature. After 27 min, the target temperature of 95 °C was reached, and the addition of Ca(OH)2 was started. The 96.5 g of suspension was added over a period of 30 min. The mixture was then stirred at 95 °C for a further 180 min. The suspension was then removed from the reactor and filtered through a Buchner funnel. The filter cake was washed with 100 g of deionized water.

[0191] Example 3: Reaction of a mixture containing Li2COs with Ca(OH)2 at 50 °C

[0192] In a batch reaction, a Li2CO3 suspension obtained from the thermal decomposition of a LiHCO3 solution from the pressure leach of beta-spodumene as in Example 1 was reacted with a suspension of Ca(OH)2 in water at 50 °C under stirring. The procedure was as follows:

[0193] A Li2CO3 suspension (708.6 g; 24 g / L Li2CO3; 17 g O2CO3; 225 mmol Li2CO3) was initially introduced and rendered inert under a nitrogen atmosphere. While stirring, the suspension was heated to the target temperature of 50 °C. In parallel, the previously mixed Ca(OH)2 suspension (93.9 g; 206 g / L Ca(OH)2; 17.5 g Ca(OH)2; 236 mmol Ca(OH)2) was prepared by resuspending it under a nitrogen atmosphere at room temperature. After 11 min, the target temperature of 50 °C was reached, and the addition of Ca(OH)2 was started. The 93.9 g of suspension was added over a period of 30 min. The mixture was then stirred at 50 °C for a further 180 min. The suspension was then removed from the reactor and filtered through a Buchner funnel. The filter cake was washed with 100 g of deionized water.

[0194] Example 4: Reaction of a mixture containing Li2COs with Ca(OH)2 at 60 °C

[0195] In a batch reaction, a Li2CC>3 suspension obtained from the thermal decomposition of a LiHCO3 solution from the pressure leach of beta-spodumene as in Example 1 was reacted with a suspension of Ca(OH)2 in water at 60 °C under stirring. The procedure was as follows:

[0196] A Li2CO3 suspension (706.7 g; 24 g / L Li2CO3; 17 g O2CO3; 225 mmol Li2CO3) was initially introduced and rendered inert in a nitrogen atmosphere. While stirring, the suspension was heated to the target temperature of 60 °C. In parallel, the previously mixed Ca(OH)2 suspension (89.2 g; 206 g / L Ca(OH)2; 17.4 g Ca(OH)2; 235 mmol Ca(OH)2) was prepared by resuspending it under a nitrogen atmosphere at room temperature. After 17 min, the target temperature of 60 °C was reached, and the addition of Ca(OH)2 was started. The 89.2 g of suspension was added over a period of 30 min. The mixture was then stirred at 60 °C for a further 180 min. The suspension was then removed from the reactor and filtered through a Buchner funnel. The filter cake was washed with 100 g of deionized water.

[0197] Discussion of the results of the experimental series on the production of LiOH from Li2CC>3

[0198] Table / / Yield of lithium determined by ICP-MS of Li in filtrate and wash filtrate.

[0199] As can be seen from the results in Table 1, Example 1 showed the highest yield at a reaction temperature of 40 °C. Unexpectedly, the results in Table 1 show that the effect of temperature is not uniform. Starting at the 40 °C result, the yield decreases with increasing temperature, then rises again, and then falls again. This particularly unusual behavior demonstrates a complexity of the process that could not have been foreseen under any circumstances.

[0200] The precise composition of the filtrate was analyzed using ICP-MS. The following table shows the elemental composition of the filtrate for the relevant elements.

[0201] Table 2: ICP measurement of the filtrates from the test series for the reaction of a mixture containing U2CO3 with Ca(OH)2.

[0202] As can be seen from the results in Table 2, the results for Example 1 show not only the highest yield but surprisingly also the lowest amounts of Na, Al and K impurities at a reaction temperature of 40 °C. This is particularly true for Na and K, where the values ​​almost doubled and tripled respectively when the reaction temperature was increased from 40 °C to 50 °C. With regard to these impurities, higher amounts of impurities were recorded as the reaction temperature increased. Surprisingly, however, this does not necessarily apply to the Si and Ca impurities. For Si as an impurity, the amounts increased with increasing temperature, whereby this increased suddenly several times at 60 °C and then fell to the lowest value in the series at 95 °C.For Ca as an impurity, the amounts initially increased at 50 °C, then fell to the lowest value at 60 °C, and then subsequently rose to the highest value at 95 °C. The example with a reaction at 95 °C thus achieved by far the lowest silicon values, but (also by far) the highest calcium values. Conversely, the example at 60 °C achieved by far the highest amounts of Si impurities, but (again by far) the lowest values ​​of Ca impurities.

[0203] Thus, the series of experiments surprisingly revealed, based on the temperature parameter, a complexity of factors that play a role in the reaction of Li2CO3, which was obtained from the thermal decomposition of a LiHCOs solution from the pressure leach of beta-spodumene according to the present invention, with a suspension of Ca(OH)2, in particular with regard to the efficiency of the process and the purity of the resulting LiOH solution.

[0204] Series of experiments for the production of LiHCOs

[0205] Example 5: Generation of LiHCOs at pH 11 and 40 °C

[0206] In a batch approach, Li2CC>3-containing filter cake obtained from a pressure leach of beta-spodumene was resuspended in water with stirring and gassed with CO2 at 40 °C. For this purpose, the filter cake (500.6 g; 33.2% residual moisture;

[0207] 19.9 mg / g O2CO3; 35 g Li2CO3; 480 mmol O2CO3) was added and resuspended with 1204 mL H2O. While stirring, the suspension was heated to the target temperature of 40 °C. After 8 min, the target temperature of 40 °C was reached, and the addition of 5.5 bar CO2 was started. After a reaction time of 10 min, the pressure was released, the suspension was removed, and filtered through a Buchner funnel. The filter cake was washed with 500 g of deionized water.

[0208] Example 6: Generation of LiHCOs at pH 4 and 40 °C

[0209] In a batch reaction, a filter cake containing Li2CC>3, which was obtained from a pressure leach of beta-spodumene as in Example 5, was resuspended in water with stirring and gassed with CO2 at 40 °C. For this purpose, the filter cake (450.0 g; 36.0% residual moisture; 17.1 mg / g Li2COs; 26 g Li2COs; 355 mmol Li2COs) was initially introduced and resuspended with 849 mL H2O. The starting pH of the suspension was 11.1. The target pH of 4.0 was achieved by adding 17 g of 96% H2SO4. The suspension was then heated to the target temperature of 40 °C with stirring. After 16 min, the target temperature of 40 °C was reached and the addition of 5.2 bar CO2 was started. After a reaction time of 10 minutes, the pressure was released, the suspension was removed, and filtered through a Buchner funnel. The filter cake was washed with 450 g of deionized water.

[0210] Example 7: Generation of LiHCOs at pH 13 and 40 °C

[0211] In a batch reaction, a filter cake containing Li2CC>3, which was obtained from a pressure leach of beta-spodumene as in Example 5, was resuspended in water with stirring and gassed with CO2 at 40 °C. For this purpose, the filter cake (450.7 g; 36.0% residual moisture; 17.1 mg / g O2CO3; 26 g Li2CO3; 355 mmol Li2CO3) was initially introduced and resuspended with 849 mL H2O. The starting pH of the suspension was 11.1. The target pH of 13.0 was achieved by adding 27 g of 50% NaOH. The suspension was then heated to the target temperature of 40 °C with stirring. After 15 min, the target temperature of 40 °C was reached and the addition of 5.5 bar CO2 was started. After a reaction time of 10 minutes, the pressure was released, the suspension was removed, and filtered through a Buchner funnel. The filter cake was washed with 450 g of deionized water.

[0212] Example 8: Production of UHCO3 at pH 11 and room temperature

[0213] In a batch reaction, filter cake containing U2CO3, obtained from a pressure leach of beta-spodumene as in Example 5, was resuspended in water with stirring and gassed with CO2 at room temperature. For this purpose, the filter cake (450.1 g; 36.0% residual moisture; 17.1 mg / g U2CO3; 26 g Li2CO3; 355 mmol U2CO3) was initially introduced and resuspended with 849 mL H2O. At a temperature of 27 °C, 5.2 bar of CO2 was added. After a reaction time of 14 minutes, the pressure was released, the suspension was removed, and filtered through a Buchner funnel. The filter cake was washed with 450 g of deionized water.

[0214] Example 9: Generation of LiHCOs at pH 10.5 and 100 °C

[0215] In a batch reaction, a filter cake containing Li2CC>3, which was obtained from a pressure leach of beta-spodumene as in Example 5, was resuspended in water with stirring and gassed with CO2 at 100 °C. For this purpose, the filter cake (450.1 g; 36.0% residual moisture; 17.1 mg / g O2CO3; 26 g Li2COs; 355 mmol Li2COs) was initially introduced and resuspended with 849 mL H2O. The starting pH of the suspension was 11.0. The target pH of 10.5 was achieved by adding 0.8 g of 96% H2SO4. The suspension was then heated to the target temperature of 100 °C with stirring. After 21 min, the target temperature of 100 °C was reached and the addition of 5.3 bar CO2 was started. After a reaction time of 10 minutes, the pressure was released, the suspension was removed, and filtered through a Buchner funnel. The filter cake was washed with 450 g of deionized water.

[0216] Discussion of the results of the test series for the production of LiHCOs

[0217] Table 3: Lithium yield determined by ICP-MS of Li in filtrate and wash filtrate.

[0218] As can be seen from the results in Table 3, Example 5 at pH 11 and 40 °C showed the highest yield. The yield of Example 6 at pH 4 is also relatively high. This is due to the fact that the sulfuric acid partially destroys the analcime, thereby extracting more lithium than the alkaline experiments. However, the disadvantage here is that lithium sulfate is formed, thus introducing a new anion into the process, which must then be separated. The yield in the experiment according to Example 9 at pH 10.5 and 100 °C is comparatively lower.

[0219] Regarding the pH value during the CO2 introduction step, it can be noted that, as a comparison of the results from Examples 5, 6, and 7, which were conducted at the same temperature, shows that the highest yield was achieved at pH 11. Both higher and lower pH values ​​of the starting mixture resulted in lower yields. Thus, it was surprisingly found that a significant optimization of the lithium yield can be achieved by adjusting the pH value of the starting mixture.

[0220] Furthermore, it was unexpectedly discovered that optimization can also be achieved by adjusting the temperature at which the CO2 is introduced. A comparison of the results for Examples 5, 8, and 9, which were conducted at pH 10.5 and 11, respectively, shows that Example 5 achieved the highest yield. In particular, the results of Example 8, which was conducted at a lower temperature, and Example 9, which was conducted at a higher temperature, demonstrate that a significant optimization of the lithium yield can also be achieved by adjusting the temperature at which the CO2 is introduced.

[0221] The precise composition of the filtrate was analyzed using ICP-MS. The following table shows the elemental composition of the filtrate based on the relevant elements.

[0222] Table 4: ICP measurement of the filtrates from the LiHCO production series.

[0223] As can be seen from the results in Table 4, the results for Example 5 show, in addition to the highest yields of Li (here in the filtrate) already evident in Table 3, also - with the exception of Al - the lowest amounts of impurities such as Na, Si, Ca, and K. This optimization can again be clearly seen both with regard to the pH value (by comparing the respective results for Examples 5 to 7) and with regard to the temperature (by comparing the respective results for Examples 5, 8, and 9).

[0224] Although the results for Example 5 show the highest level of Al contamination, this impurity still constitutes by far the smallest amount of impurities compared to the Na, Si, Ca, and K impurities in all examples. Furthermore, lower levels of Si contamination are preferable to higher levels of Al contamination, as silicon is difficult to separate.

[0225] CITED LITERATURE

[0226] - WO 2019 / 220004 A1

[0227] - WO 2018 / 234614 A1

[0228] - EP 2749535 A1

[0229] - CN 101948124 B

[0230] - WO 2011 / 148040 A1

[0231] - CN 103183366 A

[0232] - CN 113428882 A

[0233] - WO 2023 / 081961 A1

[0234] - CN 107265483 A

[0235] - WO 2024 / 089394 A2

[0236] Habashi Fathi, Handbook of Extractive Metallurgy, 1997, page 2045

[0237] - Wietelmann Ulrich et al., UHmann's Encyclopedia of Industrial Chemistry, 2000, page 354

[0238] - CN 111635999 A

Claims

1. Process for producing LiOH, comprising(1) providing a mixture A containing Li2CO3;(2) treating the mixture A provided in (1) with carbonic acid, with at least partial conversion of the Li2CO3 contained therein into LiHCO3, and obtaining a mixture B containing LiHCO3;(3) thermally converting at least a portion of the mixture B obtained in (2) and obtaining a mixture C containing Li2CO3;(4) reacting the mixture C obtained in (3) with M(OH)2, with at least partial conversion of the Li2CO3 contained therein into LiOH, and obtaining a mixture D containing LiOH, wherein M is an alkaline earth metal.

2. The process according to claim 1, wherein the Li2CO3 content of the mixture A in (1), based on the solids content of the mixture A, is in the range of from 0.1 to 16.0 wt.-%.

3. The process according to claim 1 or 2, wherein providing of the mixture A according to (1) comprises(1.a) providing a mixture M0 containing one or more lithium-containing minerals;(1.b) calcining the mixture M0 to obtain a mixture M1 containing one or more calcined lithium-containing minerals;(1.c) reacting the mixture M1 obtained in (b) with an alkali metal carbonate, with at least partial conversion of the one or more calcined lithium-containing minerals into Li2CO3, and obtaining a mixture A containing Li2CO3;(1.d) separating off at least a portion of the unconverted alkali metal carbonate from the mixture A obtained in (1.c) and obtaining a mixture M2 containing unconverted alkali metal carbonate;(1.e) providing the mixture M2 for reacting in (1.c) as a source of alkali metal carbonate.

4. The process according to claim 1 or 2, wherein providing of the mixture A according to (1) comprises(1.a‘) providing a mixture M0‘ containing one or more lithium-containing minerals;(1.b‘) reacting the mixture M0‘ with an alkali metal carbonate, with at least partial conversion of the one or more lithium-containing minerals into Li2CO3, and obtaining a mixture A containing Li2CO3;(1.c‘) separating off unconverted alkali metal carbonate from the mixture A obtained in (1.b‘) and obtaining a mixture M2‘ containing unconverted alkali metal carbonate;(1.d‘) providing the mixture M2‘ for reacting in (1.b‘) as a source of alkali metal carbonate.

5. The process according to any one of claims 1 to 4, wherein during treating in (2) the temperature is in the range of from 0 to 150 °C.

6. The process according to any one of claims 1 to 5, wherein treating in (2) takes place in aqueous solution and CO2 is introduced into the aqueous solution.

7. The process according to claim 6, wherein, prior to the introduction of CO2, the aqueous solution has a pH in the range of from 9 to 13.

8. The process according to claim 7, wherein during treating in (2) the temperature is in the range of from 25 to 70 °C.

9. The process according to any one of claims 6 to 8, wherein CO2 is introduced into the aqueous solution at a pressure of from 1 to 15 bar (absolute) bar (absolute).

10. The process according to any one of claims 1 to 9, wherein treating in (2) comprises (2.1) treating the mixture A provided in (1) with carbonic acid, with at least partial conversion of the Li2CO3 contained therein into LiHCO3;(2.2) subjecting the mixture obtained in (2.1) to a solid-liquid separation step, and obtaining a solid mixture M4 containing unconverted Li2CO3 and a liquid mixture B containing LiHCO3.

11. The process according to any one of claims 1 to 10, wherein the pH of the mixture B obtained in (2) is in the range of from 5 to 9.

12. The process according to any one of claims 1 to 11, wherein the mixture B obtained in (2) contains less than 30.0 wt.-% of alkaline earth metals.

13. The process according to any one of claims 1 to 12, wherein reacting in (3) further comprises(3.1) reacting a portion of the mixture B obtained in (2) with M(OH)2, with at least partial conversion of the LiHCO3 contained therein into LiOH, and obtaining a mixture D‘ containing LiOH, wherein M is an alkaline earth metal.

14. The process according to any one of claims 1 to 13, wherein, independently of one another, during reacting in (4) and / or (3.1) the temperature is in the range of from 10 to 100 °C.

15. The process according to claim 14, wherein during reacting in (4) the temperature is in the range of from 10 to 50 °C.

16. The process according to any one of embodiments 1 to 15, the process further comprising(5) separating off MCO3 from the mixture D obtained in (4) and / or from the mixture D‘ obtained in (3.1) to obtain a mixture E containing LiOH.

17. The process according to claim 16, wherein separating off in (5) comprises(5.1) subjecting the mixture D obtained in (4) and / or the mixture D‘ obtained in (3.1)to a solid-liquid separation step and obtaining a solid mixture M5 containing CaCO3 and a liquid mixture E containing LiOH;(5.2) washing the solid mixture M5 obtained in (5.1) with water and obtaining wash water containing LiOH,5         (5.3) providing at least a portion of the wash water containing LiOH obtained in (5.2)for reacting in (4), wherein at least a portion of the wash water containing LiOH is preferably admixed with alkaline earth metal hydroxide M(OH)2 prior to being recycled into (4).10   18. The process according to claim 17, wherein separating off in (5) further comprises anion exchange, preferably a cationic ion exchange.