RU2573522C1 - Method of producing cobalt or cobalt-chromium thiospinel - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: cobalt or cobalt-chromium thiospinel is obtained in a self-propagating high-temperature synthesis mode in an air atmosphere. The raw material used is a powdered mixture of cobalt sulphide CoS with the addition of cobalt metal powder for the synthesis of Co₃S₄, chromium for the synthesis of CoCr₂S₄ and crystalline sulphur, taken to the corresponding stoichiometric composition with a 5% sulphur excess.

EFFECT: invention simplifies the process, improves the efficiency, rate and environmental friendliness of the process.

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Description

The invention relates to the field of inorganic chemistry, and in particular to the technology of self-propagating high-temperature synthesis (SHS), and can be used to obtain cobalt Co ₃ S ₄ and cobalt-chrome thiospinel CoCr ₂ S ₄ .

A known method of producing thiospinels [RJ Bouchard, PA Russo, A. Wold. Preparation and electrical properties of some thiospinels. - Inorganic Chemistry, 1965, Vol, 4, No. 5, pp. 685-688] by a high-temperature combination of metals (99.99% pure) with sulfur. The reaction is carried out in a vacuum quartz tube. Several firing with grinding in a dry nitrogen atmosphere (about 1 hour in a mechanical mortar) between firing is required to achieve uniformity. For the synthesis of Co ₃ S ₄ is carried out two successive firing: 24 hours at 600 ° C and 70 hours at 700 ° C, respectively, for CoCr ₂ S ₄ three firing: 48 hours at 600 ° C, 24 hours at 900 ° C and 48 hours at 900 ° C. The authors found that some of the thiochromites can also be obtained by the reaction of the corresponding oxide spinels with H ₂ S at elevated temperatures in accordance with the general reaction: AB ₂ O ₄ + 4H ₂ S → AB ₂ S ₄ + 4H ₂ O.

A known method of producing cadmium thiochromate [SU, USSR Patent, 432095, C01B 17/20, Method for producing chalcogenide spinel. / EAT. Shumilkina, N.N. Parfenova] synthesis from powders of the starting compounds in vacuum. To reduce the synthesis time and simplify the technology for producing chalcogenide spinel, it is proposed that sulfides be synthesized at 600-650 ° C for 0.5-1 h and a pressure in the reaction chamber of 10 ^-4 -5 · 10 ^-5 mm Hg.

A method is also known [US, US Pat. No. 4,041,140, C01B 17/20, C04B 35/70, Method of making a sulphide ceramic body. / Tsuneharu Nitta, Shigeru Hayakawa, Yukio Kasahara, Ziro Terada. Appl. No: 489.048, 1974] for the preparation of polycrystalline sulfide by sulfonation of an oxide material in a carbon disulfide atmosphere at a temperature in the range of 400-1000 ° C.

The disadvantages of the known methods is the duration and multi-stage process, as well as significant energy costs for heating mixtures and prolonged homogenization, the use of toxic gaseous hydrogen sulfide.

The closest technical solution - the prototype is a method for the synthesis of sulfochromites [F.K. Lottering. About ferrimagnetism of some sulfides and oxides. - Advances in Physical Sciences, 1958, T. 66, no. 10, p. 247-300]. The process is carried out by heating a mixture of two metal powders and sulfur in an evacuated quartz tube at a temperature of 600 ° C, 900 ° C for a long time. Since metal grains are usually quite coarse, the preparation after the first calcination is not uniform. Therefore, the material is calcined again almost twice as long at a temperature of 500 ° C, 900 ° C, and then grinded and pressed into a ball shape. The manufacturing methods and the phases obtained (identified by x-ray) are shown in table 1.

The disadvantages of this method are the complexity, multi-stage synthesis, significant energy costs for heating mixtures to 600 ° C, 900 ° C and homogenization of the product for a long time.

In the inventive method, the disadvantages are eliminated by the fact that the synthesis of cobalt and cobalt-chrome thio spinels is carried out by the SHS method, which makes it possible to drastically reduce the cost of obtaining refractory materials. Such a process, based on the use of the internal chemical energy of the system, allows synthesis at high temperatures, short synthesis times, and low energy costs. The simplicity of equipment, high technological productivity, high speed and environmental friendliness of the process also indicate the appropriateness of using this method.

The initial reagents for obtaining polycrystalline samples are simple substances with a purity of 99.99% of the mass. To determine favorable conditions, a comparative synthesis of thiospinels obtained from the starting metals and sulfur, as well as from metal sulfides with the addition of metals and sulfur, to the corresponding stoichiometric composition was carried out (Table 2).

SUMMARY OF THE INVENTION

In the claimed method for producing a cobalt or cobalt chrome tioshpineli comprising rubbing, pressing the starting materials, ignition, combustion and synthesis tioshpineley in CBC mode in the air atmosphere, as starting substances used powder mixture of metal sulfide (CoS) with added cobalt metal powder for the synthesis of Co ₃ S ₄ , chromium for the synthesis of CoCr ₂ S ₄ and crystalline sulfur, taken to the corresponding stoichiometric composition with a 5% excess of sulfur due to its partial sublimation at high temperatures.

The claimed technical solution has the following set of essential distinguishing features in relation to the selected prototype:

- the synthesis of cobalt and cobalt-chromium thiospinels is carried out by the method of self-propagating high temperature synthesis (SHS);

- powdered metal sulfide (CoS) with the addition of cobalt metal powder for the synthesis of Co ₃ S ₄ , chromium for the synthesis of CoCr ₂ S ₄ and crystalline sulfur taken to the corresponding stoichiometric composition with a 5% excess of sulfur due to its sublimation when using high temperatures;

- synthesis of thiospinels in the combustion mode is carried out in an atmosphere of air, because the transience of the process does not allow the synthesis products to actively interact with the environment.

The implementation of the invention is achieved by performing technological operations in the following sequence.

For the synthesis of thiospinels Co ₃ S ₄ take the required amount of powdered cobalt sulfide, cobalt and elemental sulfur with a 5% excess. For the synthesis of CoCr ₂ S ₄ take the required amount of powdered cobalt sulfide, chromium and elemental sulfur with a 5% excess.

Weighed portions of the reagents are ground in an agate mortar, then the powders are thoroughly mixed in a mechanical ball mill for 6 hours. The resulting mixture was tabletted. The tablets are burned in SHS mode. The setup scheme for synthesis in SHS mode is presented in Fig. 1. The installation platform (1) is equipped with a gas outlet channel (2) and electrical terminals (3). Tablets (4) are placed on a refractory substrate (5) under a nichrome spiral (6), to which a voltage is applied to initiate a reaction. Between the bell (7) and the platform is a rubber gasket (8). As a result of initiation in a heated surface layer of the sample, a chemical reaction is excited and a synthesis wave is formed, which propagates along the axis of the sample at a certain speed. The propagation of the synthesis wave is accompanied by a bright glow. The tablet burns out in a few seconds.

As a result of combustion, a solid product is formed, which, when subjected to mechanical action, easily turns into powder.

The proposed method is implemented in laboratory conditions, illustrated by the following examples.

Example 1

Take 1.49 g of powdered cobalt sulfide CoS, mix with 1.93 g of powdered cobalt TPM grade and 1.66 g of crystalline sulfur qualification "os. H" taking into account a 5% excess. Weighed portions of the reagents are ground in an agate mortar, then the powders in a ball mill are thoroughly mixed for 6 hours until smooth. The resulting mixture was tabletted in the form of a cylinder with a diameter of 10 mm.

The tablet is placed on a refractory substrate under a nichrome spiral. By short-term supply of an electrical impulse to a nichrome spiral, the combustion and synthesis of cobalt thiospinels are initiated. In this case, in the heated surface layer of the sample, a chemical reaction is excited and a synthesis wave is formed, which propagates along the axis of the sample at a certain speed. The propagation of the synthesis wave is accompanied by a bright glow. The tablet burns out in a few seconds. As a result of combustion, a solid product is formed, which, when subjected to mechanical action, easily turns into powder.

.According to x-ray phase analysis (XRD), the combustion product is a phase of cobalt thio spinel having a cubic cell with the structure of a normal spinel, with a lattice parameter a = 9.40

.

Example 2

.Take 1.56 g of powdered cobalt sulfide CoS, mix with 1.79 g of powdered chromium and 1.73 g of crystalline sulfur, taking into account a 5% excess, triturate and extrude under the same conditions as in example 1. According to XRD data the product is a phase of cobalt-chrome thiospinel having a cubic cell (type MgAl ₂ O ₄ ) with a lattice parameter a = 9.91

.

Example 3

, с примесью фаз сульфидов металлов.3.44 g of powdered chromium sulfide Cr ₂ S _{3 are} taken, mixed with 1.01 g of powdered cobalt and 0.58 g of crystalline sulfur, taking into account a 5% excess, triturated and pressed under the same conditions as in example 1. By According to XRD the product obtained is a cobalt chrome tioshpineli phase having a cubic cell (type MgAl ₂ O ₄₎ with the lattice parameter a = 9.91

mixed with metal sulfide phases.

Example 4

For comparison, the synthesis of thiospinels from the starting metals and sulfur was carried out in the SHS mode.

For the synthesis of CoCr ₂ S _4, 1.01 g of powdered cobalt is taken, mixed with 1.79 g of powdered chromium and 2.31 g of crystalline sulfur, taking into account a 5% excess; for the synthesis of Co ₃ S _4, 2.90 g of powdered cobalt is taken mixed with 2.11 g of crystalline sulfur, taking into account a 5% excess, triturated and pressed under the same conditions as in example 1.

According to XRD data, synthesis from starting metals and sulfur leads to the formation of metal sulfides with an insignificant amount of thiospinel (~ 30%), a high exothermic effect leads to decomposition of the resulting spinel.

Powders obtained by burning mixtures were studied by X-ray diffraction (Dructometer D8-GADDS by Bruker, powder method, CoKα radiation).

The claimed technical solution is to simplify the method and the possibility of obtaining cobalt and cobalt-chromium thio spinels with minimal energy and time costs due to the speed of the process.

Claims (1)

A method for producing cobalt or cobalt chrome thio spinel, comprising synthesis from a mixture of metal and sulfur powders, characterized in that the synthesis of cobalt and cobalt chrome thio spinel is carried out in the SHS mode in air, and CoS metal powder is added as reagents with the addition of cobalt metal powder for Co synthesis ₃ S ₄ , chromium for the synthesis of CoCr ₂ S ₄ and crystalline sulfur, taken to the corresponding stoichiometric composition with 5% excess sulfur due to partial sublimation at high temperatures.

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