CS200006B1 - Process for preparing polydispersion powdered tungsten carbide by thermal decomposition of vapour of tungsten hexacarbonyle - Google Patents

Description

(54) Method for the preparation of polydisperse powdered tungsten carbide by thermal decomposition of tungsten hexacarbonyl feathers

The invention provides a direct preparation of high dispersion tungsten carbide powder by thermal decomposition of tungsten hexacyrbonyl.

At present, tungsten carbide aa is prepared in several ways: a) by direct synthesis of carbon and tungsten in electric furnaces, b / in the auxiliary metal bath, o / synthesis of tungsten powder and carbon monoxide, whereby the physicochemical chemistry of the carbide obtained depends on powder preparation. tungsten; fine tungsten carbide powder suitable for catalysis of chemical processes is prepared by:

1. of tungsten powder, obtained from white, respectively. yellow tungstic acid modification,

2. from carbonyl tungsten obtained by thermal decomposition of tungsten hexacarbonyl. The advantages of preparing tungsten carbide by methods a / and b) are mainly that tungsten carbide powder with an exact stoichiometric composition and a well-developed crystalline structure is prepared.

The advantages of method c1 and d2 are that a fine polydisperse powdered carbide with a non-stoichiometric composition and a defective crystalline structure is prepared.

The disadvantage of all the above preparations is that they are time-consuming and temperature-consuming.

The above drawbacks have no method of preparing polydisperse powdered tungsten carbide py200 006 by curing tungsten hexacarbonyl vapors in the range of 750 ° C to 1050 ° C, which is based on the fact that tungsten hexacarbonyl vapors va decompose in a carbon monoxide atmosphere.

The advantages of the invention are, in particular, the elimination of the hasty and demanding temperature regime, and thus the tungsten carbide preparation time is reduced to 30 times.

The preparation of tungsten carbide by thermal decomposition of tungsten hexacarbonyl in CO atmosphere takes place in a temperature range of 750 to 1050 ° C. At a linear carrier gas flow rate of CO of 0.75 to 1.5 m / s, the decomposition zone length must be selected such that the reaction mixture, i.e., the reaction mixture, e.g. for W / CO / g and CO decomposition products were maintained at a given temperature for an average of 3-5 s.

The use of carbon monoxide as the carrier gas epoleptically guarantees the production of powdered polydisperse tungsten carbide having a defective structure and non-stoichiometric composition, a carbon content in the range of 5.9 to 6.12%, no free carbon and trace impurities below 0.001%.

Example

Tungsten e hexa-carbonyl vapors decompose thermally at 750 ° C in a carbon monoxide atmosphere and with a flow rate of 0.75 m / s, in a decomposition reaction zone of 2.25 m with a reaction time of 3 s. A polydispersed powdered tungsten carbide with a defective structure with a non-stoichiometric composition is formed; carbon content 5.9 no free carbon and trace impurities below 0.001% ·

Other advantages of the invention are:

By changing the reaction conditions it is possible to rapidly and significantly influence the physico-chemical hair of the product.

The whole process of preparation of the RO can be fully automated.

The prepared tungsten carbide can be used in powder metallurgy or as a catalyst in chemical and electrochemical processes and in electrical engineering.

Claims (1)

OBJECT OF THE INVENTION A process for the production of polydisperse powdered tungsten carbide by thermal decomposition of tungsten hexacarbonyl vapors in the range of 750 to 1050 ° C, characterized in that decomposition aa is carried out in a carbon monoxide atmosphere.