FI107445B - Process for the preparation of metal hydroxides - Google Patents

Abstract

The present invention relates to a process for preparing sparingly soluble metal hyroxides of the general formula M<(x))<OH)x, where M = Co, Zn, Ni and/or Cu and x is the valency of the metal. <IMAGE>

Description

107445

Process for the preparation of metal hydroxides

The invention relates to a process for the continuous preparation of poorly soluble metal hydroxides of the general formula M 'OH *, wherein M = Co, Zn, Ni or Cu and x is the valence of the metal.

Metal hydroxides of cobalt, zinc, nickel, and copper are valuable intermediates for the preparation of inorganic or organic salts of these metals, for the preparation of the corresponding oxides, or for the pure metals themselves. Cobalt hydroxide can be made by calcining cobalt oxide of a defined composition, for use, for example, in electronics for the manufacture of varistors or batteries, or by reduction to a cobalt metal powder having a defined particle size distribution. Nickel hydroxides act as pigments or are used with various dopants and particle structures in batteries. Zinc hydroxides can serve as precursors for pigments, and copper compounds can be converted to catalytically active materials.

In the production of hydroxides for various applications, the foremost goal is to make the most compact and fluid material possible; 25 for woodworking. Cobalt metal powder made from cobalt hydroxide, after particle size distribution and particle structure, after sintering with tungsten carbide, results in, for example, special wheelchair tools.

30 Newly developed foam anodes, especially used in nickel-hybrid cells, require • · nickel hydroxide, which has been optimized for both its intended use and the processing technology used. While the use of high power batteries requires a high packing density of the active material, the method of making a paste for foam anodes uses a material of high flowability, compact particle shape, narrow particle size distribution, and standard quality. In addition, the product must be well miscible with commonly used additives such as cobalt metal powder and cobalt oxide.

One such material and the main features of the manufacturing process are described in JP Hi 4-80513. The nickel hydroxide particles having a diameter of 10 to 1 µm are crystallized, whereupon the nickel salt solution and the alkali hydroxide in solid or liquid form are continuously stirred at constant pH and constant temperature. PH 11 and 48 ° C are reported as favorable experimental conditions. It is further known that sufficiently dense nickel hydroxide can be prepared by precipitation in the presence of ammonia or an ammonium salt. Thus, nickel nitrate and an aqueous ammonia solution are prepared from Trans. Faraday Soc. 51 (1955) 961 A nickel amine complex solution obtained by boiling or steam treatment with nickel hydroxide under normal or reduced pressure and having a substantially smaller specific surface area compared to nickel hydroxides doped in the absence of ammonia: ). The preparation of dense nickel hydroxides in the presence of ammonia or an ammonium salt is also disclosed in JP patent applications Sho 53-6119 and Sho 61-18107. The former patent application describes the precipitation of nickel hydroxide by adding alkali hydroxide to a corresponding solution having a pH of at least 3.0. Electrochemical studies on material prepared in this way resulted in particularly high specific charge capacities compared to commercial nickel hydroxides.

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However, such products do not yet meet the above requirements for particle shape, particle size distribution and castability.

EP-A 353 837 discloses essential features of a process for the preparation of dense nickel-5 hydroxide and its use in alkaline batteries. Prepare a solution of nickel (II) -tetra-amine salt by extraction of nickel nitrate or nickel sulphate in dilute ammonia solution and disperse in a controlled manner with the addition of sodium hydroxide according to the following reaction:

Ni (NH 3) 4 SO 4 + 2 NaOH => Ni (OH) 2 + Na 2 SO 4 + 4 NH 3

The reaction is carried out at temperatures between 40 and 50 ° C and at a basic pH of 11 and 13. The pore volume decreases as the pH drops. It is expressly shown that the pore-free product can only be crystallized at sufficiently low reaction rates. In addition, the nickel hydroxide produced by this process has a high crystallinity, a low specific surface area, a low pore volume and therefore a high physical density. The drawbacks of this product, which can be attributed to the high density, are also described. The low specific surface area results in low proton conductivity and higher current density, which promotes the formation of undesired γ-NiOOH, resulting in electrode swelling. At low pHs, crystallized nickel hydroxide, although having a high density, has a stronger tendency to form γ-ΝίΟΟΗ: η. A compromise can be found between the required high density and the porosity required to a certain extent by selecting a medium pH. This method produces nickel hydroxide containing 3 to 10% zinc or 1 to 3% magnesium in a solid solution. These additives act against γ-NiOOH formation-35.

107445 4 JP-A-4-68249 discloses a continuous working method for crystallizing nickel hydroxide having a spherical 'particulate form. The heated cylindrical reactor 5 with an overflow tube is then pumped continuously with a metering pump under vigorous stirring of nickel saline (0.5 to 3.5 mol / l), dilute sodium hydroxide (1.25 to 10 mol / l) and ammonia and / or ammonium amyacia can also be introduced in gaseous form-10. The ammonia concentration is stated to be 10 to 28% by weight and the ammonium salt concentration to be 3 to 7.5 mol / l. Between 0.1 and 1.5 moles of ammonia are introduced per mole of the nickel salt solution to complex the nickel. After about 10-30 hours, the system reaches equilibrium-15, after which a constant quality product can be withdrawn continuously. The residence time in the reactor is between 0.5 and 5 hours.

An essential feature of this process is the performance of the reaction at a defined pH which is kept constant at 20 ± 0.1 pH intervals between 9 and 12 L by adjusting the pH and at a constant temperature between 20 and 80 ° C, with temperature variations should not exceed ± 2 K. Under these conditions, dense spherical particles with a particle size between 2 and 50 μπι are obtained. Particle size can be adjusted, in particular, by changing NH3 inflow, residence time, and agitation speed. As the mixing rate decreases or the NH3 input increases, the particle size increases. As the residence time increases in the reactor, the product becomes coarser, with a particle size and a narrower range of 30. Next, the crystalline product is filtered off, washed with water and dried. The product produced by this method already has the aforementioned properties and therefore does not need to be ground.

EP A 462 889 discloses a process for the preparation of 35 nickel hydroxide. The crystallization temperature range is above 80 ° C. The method is used with 107445 5 nitrate and / or sulphate solutions containing cobalt, cadmium and / or zinc as an additive. The cobalt content is between 1 and 8% by weight, and the cadmium and / or zinc content is between 3 and 10% by weight.

The complexation is effected by means of the ammonium salt with a NHa / Ni molar ratio between 0.3 and 0.6. This method maintains a pH of 9.2 ± 0.1. In addition, a three-blade stirrer with half the diameter of the reactor and a rotation speed of 10 between 300 and 1000 min-1 is used.

As with the method already described, the product is filtered, washed and dried.

The disadvantages of this process, on the other hand, are the large amounts of neural salts that are forced, which are at least twice the stoichiometric amount compared to nickel hydroxide and which are waste water. On the other hand, this wastewater, in addition to the small amount of complex dissolved nickel, still contains large amounts of ammonia which must be treated as waste.

It is an object of the present invention to provide a process which does not have the disadvantages of the methods described.

The present invention relates to a process for the continuous preparation of sparingly soluble metal hydroxides of the general formula M (x) OHx, where M = Co, Zn, Ni or 25 Cu, and x is the valence of the metal. The process is characterized in that the first step is reacting the reactive metal hydroxide with the complexing agent L in the presence of the alkali salts AY to form the metal complexed salt of the general formula MLnYm and the alkali and the complexing agent and the alkali metal salt, wherein the complexing agent L and the alkali salt AY are recycled to the first step and the alkali metal hydroxide formed in the first step is carried out.

In the process of the invention, ammonia and / or organic mono- and / or diamines having a chain length of 1 to 6 are preferably used as complexing agents.

The process according to the invention permits the avoidance of the waste disposal problem by using reactive hydroxides of said metals as starting materials, which can be converted into soluble form. Thus, for example, nickel hydroxide can be reacted in the presence of neutral salts with ammonia almost completely to the hexa-amine complex according to the following equation.

15 Ni (OH) 2 + 6 NH 3 + 2 NaCl => [Ni (NH 3) 6] Cl 2 + 2 NaOH.

The solid can be easily separated by filtration or decantation.

Particularly good results are obtained when the process according to the invention is carried out at temperatures in the range of 30 to 85 ° C, preferably 45 to 80 ° C.

An essential feature of the process according to the invention is that the metal hydroxide used is in a reactive form, because only then does it completely dissolve in the formation of complexes. A particularly suitable reactive metal hydroxide is the freshly precipitated metal hydroxide. Likewise, it is preferable to use reactive metal hydroxide obtained by anode oxidation of the metal.

One method for preparing the corresponding reactive nickel hydroxide is disclosed in DE patent application *: P 4 239 295.0. This is a process for the preparation of pure nickel hydroxide by the anode oxidation of metallic nickel in an aqueous electrolyte solution in the presence of sulfate ions and separation of the nickel hydroxide formed to prepare -la after processing.

In the event that the reactive metal hydroxide is to contain additives as required, for example, in nickel hydroxide, for example for the manufacture of batteries, the process of the invention may be carried out in the presence of cadmium, cobalt, magnesium, calcium and / or zinc salts. preferably in the form of the sulfate and / or chloride salts.

It is also preferably possible to carry out the preparation of the reactive metal hydroxide in the case of anodic oxidation in the presence of cadmium, cobalt, magnesium and / or zinc, whereby these elements are coupled to metal anodes.

In a preferred embodiment of the process according to the invention, the metal hydroxides contain one or more elements Co, Zn, Mg, Ca and Cd in a total amount of up to 10% by weight.

The mother liquor formed in the process of the invention contains exactly the stoichiometric amount of sodium hydroxide required for the preparation of the dense spherical metal hydroxide. Thus, the process of the invention is carried out continuously, wherein the complexing agent and the alkali salt are recycled to the first step. The decomposition of the metal complex salt is carried out with the alkali hydroxide formed in the first step.

The precursor reaction then occurs at a high yield of zero and at a rate where the intensity of the components may occur; wing blending.

Particularly preferred is the decomposition of the metal complex salts in a strongly turbulent flow which can be achieved by vigorous mixing, passive or active mixing elements and flow nozzle. The decomposition in the reactor is carried out at a defined residence time of 0.5 to 20 hours, preferably 1 to 4 hours.

Especially preferred is the tubular reactor which has proven to be a reactor. The products formed in the reaction leading to the formation of the metal hydroxide are recycled to the first stage, ammonia and sodium chloride, and used there again for the preparation of the metal amine complex so that the whole process can be effected without wastewater.

The tubular reactor is described in its general embodiment in Ullmann, Vol. B4, pp. 172-179. It is schematically shown in Fig. 1. In this, A represents the inflow of reactants, B represents the outflow of product. In the operation of the reactor in the tube, continuous operation is possible which can be adjusted for the reaction of the solid amine complexes with the alkaline mother liquor by selecting the rotation speed for the various metals so that the required physical properties of the products can be adjusted. On the other hand, a predetermined volume of 20 mixing vessels with a predetermined mixing device cannot be so flexible that different metal hydroxides of different morphologies can be prepared in one reactor. The choice of rotation speed in the tubular reactor and the incorporation of various mixers such as static mixers, active "in-line" mixers or nozzles ensures that the required mixing of the reactants with the reaction medium takes place in the shortest possible time, which is not possible .

*: The nickel hydroxide obtained by the process of the invention is particularly suitable for use in foam anodes. It has the following characteristics: 35 - tap density (ASTM B 212):> 2.0 g / cm 3 107445 9 - specific BET surface area (DIN 66232) 10 - 20 m2 / g - average particle size D50: 10 '- 20 pm - porosity: 47 - 53% - swelling in 3 M KOH: <10% 5 - specific charge capacity at the foam anode (AA cell):> 250 mAh / g - water content: <1%

The invention will now be described by way of example without limiting the invention.

Example 1. Preparation of Reactive Nickel Hydroxide a) Electrolysis

An electrolysis reactor consisting of an electrolysis cell (70 L) was charged with 200 L of sodium chloride solution 15 (50 g NaCl / L), and the electrolyte solution was circulated between both tanks with a centrifugal pump. Two tantalum baskets were hung inside the electrolysis cell, the sides of which were meshed and filled with Ni briquettes. The tantalum baskets were connected to the anodes and, against the side surfaces, pure nickel plates connected to the cathode were arranged so that the total electrode area was 0.5 m2. Electrolyzed at 4.2V and 500A at a current density of 1000 A / m2. During the electrolysis, 200 ml of a solution containing nickel sulfate and cobalt sulfate (250 g / L NiSO0-7H 2 O; 250 g / L CoSO 4 · 7H 2 O) were continuously fed to the cell during the electrolysis.

After 5 hours, 40 L / hour of suspension formed was removed from the circulation vessel and fresh 30 ml of sodium chloride solution was simultaneously pumped into the electrolysis cell so that the volume of the liquid in the electrolysis reactor remained constant. Subsequently, the suspension was filtered in batches, and as the electrolysis continued, this filtrate was transported back to the electrolysis cell instead of fresh sodium chloride solution. Thus, an additional sodium chloride solution-35 was only needed at the beginning of continuous operation, after which a closed loop 107445 10 to settle in equilibrium operation of the reactor. The suspension was well filtered and a primary gel product with an average water content of 90% was obtained. The water thus discharged was again recycled to the system as a washing gel-like primary product. Chemical analysis resulted in a mean dried sulfate content of 1.8% and an average chloride content of 2%. The total duration of the test was 105 hours. During continuous operation, a total of 870 kg of the gel-like primary product was recovered.

B) Conditioning in NaOH 200 kg of the gel-like primary product from the electrolysis reactor were dispersed in a heated double jacketed reactor with 200 L of water with vigorous stirring. Next, NaOH was adjusted to a basic pH of 13.7, 15 and the suspension was heated to 80 ° C with stirring and held at this temperature for 6 hours.

It was then filtered through a suction filter, and the product was washed from the suction filter with water. After drying in a drying oven, 19.7 kg of nickel hydroxide with a Co content of 1% were obtained. The anionisic impurities were below 500 ppm. The bulk density was 1.3 g / cm 3 and the tap density was 1.8 g / cm 3. The specific BET surface area (as measured by the N2 single point method) was very high at 88 m2 / g. The reflection had a half width (101) of 2.0.

2. Preparation of Nickel Hexammonium Chloride a) Non-continuous NH3 (25%) with 1 L of a suspension of 100 g / l of the highly active nickel hydroxide gel obtained according to Example 1 and 280 g / l of sodium hydroxide was stirred for 1 hour. kg of ammonia (25%) and stirred for one hour with stirring. The reaction mixture was filtered through a? - *: Laboratory filter and then washed in portions with a small amount of concentrated NH3. 226 g of [Ni (NH 3) 6] Cl were obtained in a yield of 90.5%.

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The batch liquor contained 9.5 g of complexively bound nickel hydroxide as well as 78 g of NaOH and excess ammonia.

Excess ammonia was distilled off with a short column of 5 pads in 25% aqueous solution.

9.5 g of complexed nickel hydroxide precipitated as a highly sedimentable and filterable product. After filtration and washing, 1.5 L of filtrate containing 280 g of NaCl 10 (3.2 M) and 78 g of NaOH (1.3 M) were obtained.

b) from continuous NH3 (25%) in a 2 L beaker with an overflow tube was pumped with stirring and cooling, 0.5 L / hr suspension containing 100 g / L of highly activated nickel hydroxide gel and 280 g / L NaCl as well as 0.5 l ammonia (25%). The overflow was led, via a downer, to a rising current classifier where the nickelhexammonium chloride formed was deposited. The filtrate exiting the upstream classifier contained 2 g / l of complex-20 nickel hydroxide and 40 g / l of sodium hydroxide, as well as 140 g / l of NaCl and excess ammonia. This corresponds to an average residence time of 4 hours with a degree of reaction of the highly active nickel hydroxide gel with nickel-hexamine ammonium chloride at 92%. 1 L of 25 filtrates containing 190 g / L NaCl, 40 g / L NH3 were purified as in Abs. al) with a short filler neck. As a condensation product, 25% ammonia was obtained as well as, after separation of the precipitated nickel hydroxide, 700 ml of a process liquor containing 140 g of NaCl 30 (3.4 M) and 40 g of NaOH (1.4 M).

c) continuously with NHs (50%) as wet S · · vapor

The reaction of the highly active nickel hydroxide gel and sodium chloride with ammonia was carried out in a continuous-35 cooled 10 µm "moving jet" reactor.

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Ammonia was recovered from the diluted process solutions by evaporation on a packing column and passed directly to the "moving shower" reactor without prior condensation as a 50% NH3 / H2O vapor mixture.

A suspension of 100 g / l of highly active nickel hydroxide gel and 280 g / sodium chloride, as well as 600 g / h of NH3 and 600 g / h of HaO was continuously introduced into the "mobile shower" reactor at a rate of 3 l / h. as a moist vapor mixture. The over-10 run of the "moving jet" reactor was connected via an overflow line to a riser classifier where the nickel hexammonium chloride formed was deposited. The clear filtrate exiting (4 L / hr) contained 3 g / L of complexively bound nickel hydroxide, 210 g of NaCl, 49 g of NaOH and 70 g / L of NH 3. This 15 corresponded to a degree of change of 96%.

3. Preparation of Dense Nickel Hydroxide (a) Continuously in a 5 L "Moving Shower" Reactor

A heavy-duty suspension of 20 nickel-hexamine ammonium chloride (400 g in 600 g of 7% NH 3) was kept pumpable by stirring in a storage vessel. This suspension was pumped continuously into a 5 L "moving jet" reactor heated to 70 ° C. As a second component, about 1.2 L / h of pH-adjusted process liquor containing • 60 g / L NaOH and 140 g / L NaCl was dispensed at a rate of 25.

The average residence time in the reactor was about 3 hours. After 2 hours, after filtration and washing with H 2 O, 30 dense, highly filterable nickel hydroxide having a packing density of 1.6 g / cm 3 were recovered.

b) continuously in a 100 L "jet shower" reactor

The mobile jet reactor was used for the reaction of nickel hexammonium chloride and sodium hydroxide 35 into a dense nickel hydroxide, which provided optimum mixing of the reaction partners and high shear forces with mixing nozzles 13 107445 and a high-speed rotary pump. A suspension of 400 g of nickel hexammonium chloride in 600 g of 7% NH3 in a storage tank was maintained at pump-5 by pausing with stirring. This suspension was transferred at a rate of 20 kg / h into a jet pump jet operated at 73 ° C. The reaction components were continuously transported about 43 L / hr of process liquor containing 65 g / L NaOH and 10,200 g / L NaCl. The process liquor was dosed in a pH-controlled manner keeping the basic pH between 11.4 and 11.6. The average residence time was approximately 1.6 hours.

After 16 hours of overflow of the mobile jet reactor, a very rapidly deposited dense nickel-15 chelated hydroxide was obtained which was highly filterable and could be washed with about 7 L / kg of warm water to a concentration of <500 ppm. Nickel hydroxide had an average packing density of 1.9 g / cm 3 and a tapping density of 2.1 g / cm 3. The spherical particles had an average particle size of 12 µm.

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Claims (9)

1. Method for continuous production of soluble solvents. metal hydroxides tried the general formula 5 M (xlOHx, where M = Co, Zn, Ni or Cu and x is the valence of the metal, characterized in that in a first step reactive metal hydroxide is reacted with a complexing agent L in the presence of alkali salts AY to a metal number complex complex salt of the general formula MLnYm and an alkali hydroxide, and the metal complex salt is decomposed in another step by reaction with an alkali hydroxide at a pH> 7 to highly soluble metal hydroxides and complexing agent and alkali salt, wherein the complexing agent is back to the first step 15 and the decomposition of the metal complex salt is carried out with the alkali hydroxide formed in the first step. 2. A process according to claim 1, characterized in that ammonia or organic mono- and / or diamines having a chain length of 1-6 are used as complexing agents. Process according to claim 1 or 2, characterized in that the metal hydroxides are mixed with one or more elements from the group Co, Zn, Mg, Ca and Cd in a total amount of not more than 10% by weight. ** 25 Method according to any of claims 1-3, characterized in that it is carried out at temperatures in the range 30 - 85 ° C, preferably 45 - 80 ° C. Process according to any of claims 1-4, characterized in that just as precipitated metal hydroxide is used as precipitated metal hydroxide. Process according to any of claims 1-4, characterized in that as the reactive metal hydroxide is used by anodic oxidation of the metal, metal hydroxide is obtained. 35 Process according to any of claims 1-6, characterized in that the decomposition of the metal complex salts is carried out in one. vigorous turbulent flow, which is accomplished by intense stirring, with passive or active stirring elements or flow nozzles. 5 Process according to any of claims 1-7, characterized in that the decomposition is carried out in a reactor with a defined holding time for 0.5 to 10 hours, preferably 1-4 hours. 9. A process according to any one of claims 1-8, characterized in that the production takes place in a pipe reactor. «« · ·