Method for preparing nickel oxide

Abstract

The invention relates to a process for preparing NiO particles, comprising the step a0) of contacting a Ni (CO) 4 gas stream at a temperature below 100 DEG C with an oxidizing gas stream to directly produce NiO particles in the product stream of the reactor.

Description

[0001] The present invention relates to a method for preparing NiO particles.

[0002] Nickel oxide (NiO) particles can be used in many technological applications, including as cathode active material (CAM).

[0003] The conventional manufacturing route for cathode active materials (CAM) is by precipitating sulfates of Ni, Co and Mn as mixed metal hydroxides with NaOH. During this precipitation, large amounts of Na2SO4 are produced (more than 1 kg / kg final CAM). In order to convert the mixed metal hydroxides into oxide materials, water must be removed in an energy-intensive pre-calcination step. In addition, metal sulfates are expensive starting materials because they are produced late in the base metal refining value chain.

[0004] Alternatively, the preparation of nickel oxide nanoparticles starts from Ni metal. A relatively pure source of nickel metal is the decomposition of nickel tetracarbonyl (Handbook of non-ferrous metal powders, Elsevier Ltd. 2009, Chapter 17). However, this multi-step process leads to further costs.

[0005] Therefore, there is a need for an improved preparation method that avoids the above-mentioned disadvantages and is cost-effective, has a good environmental balance, avoids high salt load and can produce pure CAM.

[0006] Therefore, an object of the present invention is to provide such a method for preparing nickel oxide.

[0007] This object is achieved by a method for preparing NiO particles, the method comprising the following steps:

[0008] a0) contacting a Ni(CO)4 gas stream at a temperature below 100°C with an oxidizing gas stream to produce NiO particles directly in the product stream of the reactor.

[0009] The inventors have found that nickel oxide can be obtained directly from nickel carbonyl without the intermediate step of decomposing the Ni carbonyl into Ni metal, resulting in the above-mentioned features of the process. In particular, the main economic potential comes from the fact that a suitable Ni source can be obtained early in the metal value chain and fewer process steps may be required to produce CAM. In addition, expensive disposal of salts, especially sodium sulfate by-products, can be avoided. The process of the present invention can be used to produce materials that can be further converted into CAM. Particularly high-purity materials can be produced.

[0010] The method of the present invention comprises the step of contacting a Ni(CO)4 gas stream having a temperature below 100°C with an oxidizing gas stream to directly produce NiO particles in the product stream of the reactor.

[0011] To prepare a Ni(CO)4 gas stream, metallic Ni may be treated with carbon monoxide at high pressure (e.g., above 1 bar) and high temperature (e.g., 30°C-200°C), which results in the formation of Ni(CO)4 according to the following reaction equation:

[0012] Ni+4CO→Ni(CO)4

[0013] Therefore, in a preferred embodiment, the method of the present invention comprises the following steps:

[0014] a -1 ) Treating metallic Ni with carbon monoxide at high pressure and temperature to produce a Ni(CO)4 gas stream which optionally contains unreacted carbon monoxide.

[0015] Reaction step a -1 ) can be carried out in a first reactor, wherein step a0) can be carried out in a second reactor.

[0016] Preferably, the high pressure is above atmospheric pressure and below 30 MPa. More preferably, the high pressure is between 0.5 MPa and 20 MPa.

[0017] Preferably, the elevated temperature is in the range of 30°C to 200°C. More preferably, the temperature is in the range of 50°C to 180°C.

[0018] Unreacted CO can be recycled by separation from the product stream. In addition, some other metals (such as Fe and Co) that are part of some feed materials may be carbonylated, resulting in impure products. In this case, distillation can be performed to purify nickel tetracarbonyl. In particular, the carbonyl hydride of cobalt - CoH (CO) 4 - can be a valuable by-product, which can be used similarly to Ni (CO) 4. It is formed in the presence of both carbon monoxide and hydrogen.

[0019] Therefore, in a preferred embodiment, unreacted carbon monoxide is separated and the separated carbon monoxide is optionally used in step a. -1 ).

[0020] Preferably, the Ni(CO) 4 gas stream is purified before being used in step a0), more preferably by distillation.

[0021] In a preferred embodiment, the method of the present invention starts with a suitable Ni feed, such as Ni metal, Ni matte, mixed hydroxide precipitate (MHP), mixed sulfide precipitate containing NiS or black mass. In the case where the starting material is not Ni metal, it can be pretreated in a hydrogen atmosphere to reduce Ni to its metallic state.

[0022] Therefore, in a preferred embodiment of the present invention, the method of the present invention comprises the following steps:

[0023] a -2 ) is a process for reducing Ni matte, a mixed hydroxide precipitate containing Ni(OH)2, a mixed sulfide precipitate containing NiS, a black material containing NiO or a mixture thereof in a hydrogen gas stream to produce metallic Ni.

[0024] In particular, Ni matte, MHP and black matter offer attractive feed materials as they are either extracted early in the Ni value chain (Ni matte and MHP) or come from the recycling process of batteries and accumulators (black matter).

[0025] The optionally purified stream is introduced into a reactor where it is contacted, for example by mixing, with a preferably preheated oxidizing gas such as air or oxygen, preferably at a high turbulence level. This will result in the decomposition of nickel tetracarbonyl into nickel oxide, which will be finely dispersed due to the high reaction rate and low vapor pressure of NiO with carbon monoxide or carbon dioxide, respectively, which allows high supersaturation.

[0026] The reaction is highly exothermic, so that the reaction temperature is high enough to directly oxidize Ni tetracarbonyl to NiO without previously decomposing Ni tetracarbonyl to metallic Ni. To prevent the decomposition, the Ni tetracarbonyl gas stream has a temperature below 100°C, preferably 30°C to 90°C, more preferably in the range of 40°C to 80°C, even more preferably in the range of 45°C to 70°C, even more preferably in the range of 50°C to 60°C.

[0027] Preferably, the oxidizing gas stream is preheated, which is another option for reaction temperature regulation.

[0028] Therefore, in a preferred embodiment, the oxidation gas stream in step a0) is preheated. Preferably, the temperature is in the range of 50°C to 750°C. More preferably, the temperature is between 150°C and 500°C.

[0029] Preferably, the oxidizing gas is oxygen or a gas containing oxygen, such as air or a mixture of air and oxygen.

[0030] Preferably, step a0) can be carried out in an ejector in which high flow rates allow flameless oxidation, or in a two-component nozzle in which a spray flame can be established. In both cases, an adiabatic tubular reactor is connected to the mixing point, allowing a certain residence time at high temperature to ensure complete conversion of nickel tetracarbonyl and to allow the formation of a defined nickel oxide particle morphology.

[0031] The reactor offgas containing nickel oxide particles can be continuously cooled by mixing with cold air and heat exchangers and then enter a suitable filter unit for product separation, such as a bag filter or an electrostatic precipitator. The obtained nickel oxide nanoparticles can be further processed into CAM materials by mixing with metal oxides of cobalt and manganese and continuous thermal or mechanical treatment.

[0032] Therefore, in a preferred embodiment, step a0) is carried out in an ejector, in which preferably high fluidity allows flameless oxidation. The preferred velocity depends on the temperature of the oxidizing gas and its mass ratio to Ni(CO)4. The preferred requirement is a Reynolds number in a turbulent state in the ejector (thus, Re>4000).

[0033] In a further preferred embodiment, step a0) is carried out in a two-component nozzle in which a spray flame can be established.

[0034] Preferably, the reactor in step a0) is at least partly an adiabatic tubular reactor, more preferably an adiabatic reactor.

[0035] Preferably, the product stream is cooled, preferably using air having a lower temperature than that of the product stream and one or more heat exchangers. After cooling, the temperature of the product stream is suitably below 250° C. A heat exchanger may be coupled to the oxidation gas stream in order to transfer heat and produce a preheated oxidation gas stream for step a0).

[0036] Preferably, NiO particles are separated from the product stream, preferably in a filter unit for product separation such as a bag filter or an electrostatic precipitator, to produce NiO particles.

[0037] As mentioned above, NiO particles are preferably further processed into cathode active materials by mixing with other metal oxides (such as cobalt and / or manganese) and continuous heat treatment and / or mechanical treatment. The NiO particles obtained by the method of the present invention typically show a particle size of less than 1 μm, i.e. nanoparticles as can be shown by electron microscopy.

[0038] Preferably, step a0) is performed at a temperature ranging from 150°C to 1200°C. More preferably, step a0) is performed at a temperature ranging from 200°C to 1000°C.

[0039] The Ni(CO)4 gas stream in step a0) may further contain carbon monoxide. Preferably, in the case where the product stream contains carbon monoxide, the CO is separated and returned to step a -1 )middle.

[0040] The resulting NiO product is suitable for preparing cathode active material (CAM). CAM is the active ingredient of the cathode. The preparation of CAM is well known and described in, for example, WO 2021 / 156124 A1, WO 2022 / 101103 A1, and WO 2022 / 263226 A1.

[0041] Therefore, another aspect of the present invention is a method for preparing a cathode active material containing NiO particles, the method comprising the steps of:

[0042] b1) preparing NiO particles according to the method for preparing NiO particles according to the present invention;

[0043] b2) mixing the NiO particles with one or more other metal oxides and optionally with one or more other components of the cathode active material; and

[0044] b3) calcining the mixture of step b2) to obtain a cathode active material.

[0045] Typical metal oxides for mixing with NiO particles are cobalt oxide, nickel oxide, or both Co oxide and Ni oxide, preferably both Co oxide and Ni oxide. Other components of the CAM that may be added are, for example, a lithium source, a sodium source, or both, a Li source and a Na source.

[0046] Typical Li sources are LiOH, L2CO3, Li2O, Li2O2 or mixtures thereof. Typical Na sources are NaOH, Na2CO3, Na2O, Na2O2 or mixtures thereof.

[0047] The calcination temperature used in step b3) depends on the specific CAM and typically ranges from 600 to 1200°C, preferably from 800 to 1000°C.

[0048] Figure 1 It shows that from step a -1 ) is the preferred method of the present invention.

[0049] exist Figure 1 In the process, the reduction pretreatment (step a) -2), not shown), the metallic Ni feed (1) obtained is introduced into a carbonylation reactor (3) together with a carbon monoxide feed (2), and the resulting product is transferred to a distillation column (4). The tetracarbonyl Ni feed is transferred to a storage tank (5). Liquid tetracarbonyl Ni is pumped to a pyrolysis reactor (8) via an evaporator (7) by a liquid pump (6), where an air feed (10) is added to the reactor (8) after passing through a pre-filter (11), a compressor (12) and a heat exchanger (9). The product stream in the reactor (8) is filtered in a filter (13) (e.g., a bag or electrostatic precipitator) to separate the NiO particles (14) passing through the heat exchanger (9) from the exhaust gas (18) passing through another heat exchanger (15), a HEPA filter (16) and a vacuum pump (17).

[0050] Examples

[0051] In one example of the method, Ni powder is pretreated with hydrogen at a temperature of 280°C for 6 hours to remove any NiO passivation layer. Next, the Ni powder is treated with carbon monoxide at a temperature of 100°C and a pressure of 0.1 MPa. The mixture of carbon monoxide and Ni(CO)4 obtained by the treatment is transferred to an oxidation reactor and contacted with an air stream preheated to 200°C and having an average flow rate of about 340 m / s. The NiO nanoparticles formed in the oxidation of Ni(CO)4 are collected by thermophoresis for analysis.

[0052] Reference numerals list

[0053] 1…Ni feed

[0054] 2…Carbon monoxide

[0055] 3…Carbonylation reactor

[0056] 4…Distillation tower

[0057] 5…Storage tank

[0058] 6…Liquid pump

[0059] 7…Evaporator

[0060] 8…Pyrolysis reactor

[0061] 9…Heat exchanger

[0062] 10…Air

[0063] 11…Pre-filter

[0064] 12…Compressor

[0065] 13…Filter

[0066] 14…NiO particles

[0067] 15…Heat exchanger

[0068] 16…HEPA filter

[0069] 17…Vacuum pump

[0070] 18…Exhaust

Claims

1. A method for preparing NiO particles, the method comprising the following steps: a0) contacting a Ni(CO)4 gas stream at a temperature below 100°C with an oxidizing gas stream to produce NiO particles directly in the product stream of the reactor.

2. The method of claim 1, wherein: The Ni(CO)4 gas stream is prepared by a step prior to step a0), wherein the step is a -1 ) treating metallic Ni with carbon monoxide at high pressure and temperature to produce the Ni(CO)4 gas stream, which optionally contains unreacted carbon monoxide.

3. The method of claim 2, wherein: The high pressure is higher than atmospheric pressure and lower than 30 MPa.

4. The method according to claim 2 or 3, wherein: The high temperature is in the range of 30°C to 200°C.

5. The method according to any one of claims 2 to 4, wherein: The metal Ni is obtained by step a -1 ) before the step, wherein the step is a -2 ) is a process for reducing Ni matte, a mixed hydroxide precipitate containing Ni(OH)2, a mixed sulfide precipitate containing NiS, a black material containing NiO or a mixture thereof in a hydrogen gas stream to produce metallic Ni.

6. The method according to any one of claims 2 to 5, wherein: The unreacted carbon monoxide is separated and the separated carbon monoxide is optionally used in step a -1 ).

7. The method according to any one of claims 1 to 6, wherein: The Ni(CO) 4 gas stream is purified before being used in step a0).

8. The method of claim 7, wherein: The Ni(CO)4 gas stream is purified by distillation.

9. The method according to any one of claims 1 to 8, wherein: The oxidizing gas in step a0) is preheated.

10. The method of claim 9, wherein: The oxidizing gas is preheated to a temperature in the range of 50°C to 750°C.

11. The method according to any one of claims 1 to 10, wherein: The oxidizing gas is oxygen or a gas containing oxygen, such as air or a mixture of air and oxygen.

12. The method according to any one of claims 1 to 11, wherein: The contacting in step a0) comprises a mixing step.

13. The method according to any one of claims 1 to 12, wherein: Step a0) is carried out in an ejector in which preferably high flow rates allow flameless oxidation.

14. The method according to any one of claims 1 to 12, wherein: Step a0) is carried out in a two-component nozzle in which a spray flame can be established.

15. The method according to any one of claims 1 to 14, wherein: The reactor in step a0) is at least partly an adiabatic tubular reactor.

16. The method according to any one of claims 1 to 15, wherein: The product stream is cooled, preferably using air having a lower temperature than that of the product stream and one or more heat exchangers.

17. The method according to any one of claims 1 to 16, wherein: The NiO particles are separated from the product stream, preferably in a filter unit for product separation such as a bag filter or an electrostatic precipitator, to produce the NiO particles.

18. The method according to any one of claims 1 to 17, wherein: The NiO particles are further processed into cathode active materials by mixing with other metal oxides such as cobalt and / or manganese and by successive thermal and / or mechanical treatments.

19. The method according to any one of claims 1 to 18, wherein: The contacting in step a0) is carried out at a temperature in the range of 150°C to 1200°C.

20. The method of any one of claims 1 to 19, wherein: The Ni(CO) 4 gas stream in step a0) further contains carbon monoxide.

21. The method according to any one of claims 1 to 20, wherein: The product stream contains carbon monoxide which is separated and returned to step a -1 )middle.

22. The method of any one of claims 1 to 21, wherein: In step a0), the Ni(CO)4 gas stream has a temperature in the range of 30°C to 90°C.

23. The method of claim 22, wherein: The temperature is in the range of 40°C to 80°C.

24. The method of claim 23, wherein: The temperature is in the range of 45°C to 70°C.

25. The method of claim 24, wherein: The temperature is in the range of 50°C to 60°C.

26. A method for preparing a cathode active material containing NiO particles, the method comprising the following steps: b1) preparing NiO particles according to the method for preparing NiO particles according to any one of claims 1 to 25; b2) mixing the NiO particles with one or more other metal oxides and optionally with one or more other components of the cathode active material; as well as b3) calcining the mixture of step b2) to obtain the cathode active material.

27. The method of claim 26, wherein: The one or more other metal oxides are cobalt oxide, nickel oxide, or both Co oxide and Ni oxide.

28. The method of claim 26 or 27, wherein: In step b2), NiO particles are mixed with one or more other metal oxides and with one or more other components of the cathode active material, wherein the one or more other components are preferably a lithium source.

29. The method of any one of claims 26 to 28, wherein: In step b2), NiO particles are mixed with one or more other metal oxides and with one or more other components of the cathode active material, wherein the one or more other components are preferably a sodium source.

Images