RU2135406C1 - Method of preparing alkali metal, calcium and ammonium bromides - Google Patents

Abstract

FIELD: chemical technology for preparing inorganic salts of bromine, more particularly ammonium, lithium, sodium, potassium and calcium. SUBSTANCE: process comprises preparing bromides by counterflow extraction of bromide from iron (3+) bromide solutions with amine salt solutions in organic solvent, and reextraction is carried out with solutions of corresponding metals in counter flow mode. In addition to bromides, iron (3+) chloride solution is prepared. Method makes it possible to use accessible, cheap and operationally safe iron (3+) bromide and chlorides of corresponding metals and ammonium. EFFECT: more efficient preparation method. 1 dwg, 3 ex, 3 tbl

Description

 The invention relates to the field of chemical technology for the production of inorganic salts of bromine, in particular ammonium, lithium, sodium, potassium, calcium.

 A known method of producing bromides by the interaction of metal hydroxides with hydrobromic acid / Chem. lnd. 1984. N 11, p. 724-728 /. The method is relatively simple, but requires the use of expensive reagents.

 A number of methods are based on the reactions of bromine with hydroxides, oxides and carbonates of metals in the presence of reducing agents. The absorption of bromine and the gas phase by metal hydroxides is proposed / Italian Patent 393348, 1941 /. In the USSR, a method for the absorption of bromine by milk of lime was developed / Ksenzenko V.I. et al. Technology of bromine and iodine. 1960, Moscow: Goskomizdat. According to this method, as an intermediate product receive a solution containing bromide and calcium bromate in a ratio of 5: 1. If it is necessary to obtain a product without bromate impurities, ammonia or urea / A.c. is added to the milk of lime. USSR 138232, MKI C 01 B 9/04 /. The excess ammonia is removed by boiling and evaporation, the excess urea is destroyed by the addition of bromine water and heating / A.c. USSR 100162, MKI C 01 9/04 /. To obtain bromides of a given quality, a process based on the interaction of hydroxides with liquid bromine and ammonia by a known method for producing calcium bromide / A has been developed. with. USSR 1279965, MKI C 01 F 11/34 /. According to this method, to obtain calcium bromide of a high degree of purity, lime milk is used with a content of active calcium oxide of not more than 6.5%. The disadvantages of the latter method are the use of expensive hydroxides (upon receipt of alkali metal bromides) and work with aggressive and toxic liquid bromine.

 Known methods for producing bromine salts are based on reactions of the reaction of starting bromine-containing products: hydrobromic acid and elemental bromine with metal-containing reagents. At the same time, enterprises producing bromine produce another cheap and safe product - iron bromide (3+). However, currently unknown processes for producing metal bromides using this available reagent as a starting material. In principle, bromides can be obtained by precipitation of iron hydroxide in the interaction of iron with hydroxides or metal carbonates, but the practical implementation of this process is very difficult due to problems of filtering pulps with iron hydroxides, product loss with cakes, formation of iron oxybromides along with hydroxides (3 +). The most acceptable method, close to the present invention, is a method for producing calcium bromide from hydroxide, reducing agent and liquid bromine, described above (A.S. USSR 1279965), in combination with thermal decomposition of bromine iron into elemental bromine and iron bromide (II). For this process, in addition to the listed disadvantages (the use of expensive hydroxides in the production of alkali metal bromides and work with aggressive and toxic liquid bromine), the incompleteness of the use of bromine iron and, as a consequence, the need to return it to the redistribution of bromine extraction from natural raw materials are added.

 The invention proposed for consideration is directed to the development of a process for producing metal bromides using, as starting reagents, affordable, cheap and safe - iron bromide and chlorides of the corresponding metals.

The problem is achieved in that between the initial aqueous solutions of iron bromide (3+), alkali metal chloride of ammonium, calcium, an interphase anion exchange is carried out by means of an organic liquid anion-exchange extractant circulating between two aqueous solutions. The process, when implemented in continuous mode, is described by the equations of extraction and re-extraction (1, 2):
FeBr _{3 (B1)} + [R ₄ N] FeCl _{4 (o)} ---> FeCl _{3 (B1)} + [R ₄ N] FeBr _{4 (o)} ; (1)
MCl _{x (2B)} + [R ₄ N] FeBr _{4 (o)} ---> MBr _{x (B2)} + [R ₄ N] FeCl _{4 (o)} , (2)
where the subscripts (B1), (B2) and (o) denote the belonging of the reaction component to the aqueous iron and metal phases or the organic phase, respectively.

The process is based on the fact that the equilibria of reactions (1) and (2) are shifted to the right, towards the formation of FeCl ₃ and MBr ₃ , due to the formation of stronger iron complex compounds (3+) with chlorides compared to bromides in the almost complete absence of complex formation used metals (alkaline, calcium, and also ammonium) with halide ions. To achieve the required depth of conversion of halides, the extraction and re-extraction process is carried out in countercurrent modes of the aqueous and organic phases according to the scheme (see drawing).

As an extractant, salts of tertiary amines or quaternary ammonium bases are used, which, when contacted with iron-containing solutions of halides, transform into stable (in a wide concentration range of halides) salts of [R ₄ N] FeBr ₄ and [R ₄ N] FeCl ₄ .

Example 1. Bromides and chlorides are extracted with a solution of a trialkylmethylammonium salt in a non-polar organic solvent with a salt concentration of 11 m / L. The extraction / stripping processes are carried out from solutions of mixtures of FeBr ₃ - FeCl ₃ and CaCl ₂ - CaBr ₂ at various ratios Br ^- / Cl ^- in aqueous solutions. The data obtained are shown in tables 1 and 2.

 The average bromide / chloride separation coefficient at the extraction stage (Table 1) is 1.27, and at the bromine re-extraction stage it is approximately 0.62 (Table 2). The total enrichment factor for bromine during the transition of bromide ions from iron-containing solutions to a calcium-containing solution is 1.27 / 0.62 = 2.0.

 Example 2. According to the table. 1 and 2, an extraction countercurrent cascade is calculated for the production of calcium bromide from low-quality iron bromide from the Nebid-Dag iodine plant using an aqueous solution of calcium chloride as a re-extraction solution. The enlarged laboratory tests of the technological scheme have been carried out.

 The scheme included: 10 steps of bromine extraction, 3 steps of washing the organic phase, 11 steps of re-extraction.

 The extraction was carried out in laboratory extractors of the mixer-settler type (productivity by the sum of phase flows 1-3 l / h).

 The composition of the initial solutions, see table. 3.

 As a result, we obtained a solution of calcium bromide with a content of calcium bromide of 70% (mol) (the content of chloride ion corresponds to its concentration in the initial product - bromine iron) and a solution of iron chloride.

 Under the conditions of the process, the bromine extraction depth of 85% was achieved.

 After evaporation, a solution of calcium bromide with a density of 1.76 g / cm 53 0 was obtained, which meets the technical specifications for calcium bromide used as a "heavy drilling fluid".

 Example 3

 An anion exchange was carried out between aqueous solutions of iron bromide (3+) and lithium, sodium, potassium, and ammonium chlorides by extraction and reextraction with solutions of tetraoctylammonium salts in a non-polar hydrocarbon solvent. The bromine enrichment coefficients were determined (the ratio of the bromide / chloride separation coefficients at the stages of extraction from bromine iron solutions and reextraction with chlorides of the corresponding metals). The data are given in table. 4.

Thus, the proposed method for the production of bromides allows you to use as starting products available, cheap and safe in the work of iron bromide (3+), chlorides of the corresponding metals, ammonium. Product quality is determined by the quality of the components and the number of stages of extraction and stripping. The amine salts proposed as extractants in this case have an increased capacity due to the formation of stable complex anions FeBr ₄ ^- and FeCl ₄ ^- in the organic phase. So, at a concentration of salts of Quaternary ammonium bases of 0.1 m / L, the concentration of bromide in the organic phase at the extraction stage reaches 32 g / L, and for the chloride ion - 14 g / L.

Claims (1)

 A method of producing alkali metal, calcium and ammonium bromides from bromine-containing raw materials, characterized in that the bromides are obtained by countercurrent extraction of bromide from solutions of iron bromide (3+) with solutions of amine salts in an organic solvent, and reextraction is carried out by solutions of the corresponding metals in countercurrent mode.

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