SU149224A1 - The method of producing carbonyls of metals chromium, molybdenum and tungsten and the production of powders of these metals - Google Patents

Description

Methods are known for the preparation of carbonyls of chromium, molybdenum and tungsten metals and the production of powders of these metals by thermal decomposition of carbonyls.

In order to simplify the technological process of obtaining carbopyls of metals of chromium, molybdenum and tungsten, a method is proposed which consists in the fact that the initial chlorides of these metals in dry form are treated with carbon monoxide at 100-300 ° and a pressure of 250 atm and above in the presence of an aluminum chloride catalyst. and (or) benzene vapor or without them and metal reducing agents - iron, copper, Dewar alloy, aluminum, magnesium, zinc and others, and the carbonyls of metals obtained as a result of such a process are subjected to a thermal process. zheniyu. For example, molybdenum carbopyl is decomposed at 300-1200 °, tungsten carbonyl at 300-1200 ° in the presence of carbonic acid or another inert gas.

For the preparation of chromium, molybdenum or wolfam carbonyls, trichloric chromium, molybdenum trichloride or tungsten hexahloride, possibly not contaminated with oxychlorides, are used as the starting material.

The production of higher chlorides of chromium, molybdenum or tungsten not contaminated with oxychlorides can be carried out by treating the starting material with elemental chlorine or carbon tetrachloride vapors at elevated temperatures. The process can be carried out in a shaft furnace, in a melt or in a fluidized bed furnace.

Ores, conditioned or substandard ore concentrates, ore dressing products, etc. are used as starting material. Molybdenum ores and concentrates (middling products) are used to prepare molybdenum chloride; for production

No. 149224- 2 of tungsten tetrachloride - hubnerite and ferberite ores, middlings and concentrates mixed with charcoal; for the preparation of chromium chlorides - chromium iron, also with the addition of charcoal.

The preparation of the starting material for chlorination consists of briquetting or pelletizing. In both cases, the preparation of the material is completed by calcining. The preferred size of briquettes or pelletized material is 20-30 mm. The duration of calcination at 800 ° (without air access) is 10-12 hours.

The chlorination temperature of tungsten-containing materials is 800 °, molybdenum-containing 500-600 °, and the chromium iron is 600 °. The duration of the chlorination operation for tungsten molybdenum-containing materials is 20-24 hours, for chromic iron - 36 hours.

In the process of chlorinating tungsten and molybdenum containing material, volatile tungsten hexahloride and molybdenum chloride are formed are distilled from the source material, condensed in collectors having a temperature of 200-250 ° and thus separated from ferric chloride and sulfur chloride (when molybdenite is chlorinated)

Chlorination of a chromium iron at a temperature of 600 ° C makes it possible to obtain three-chlorine chromium in a nonvolatile residue, separating it from iron and aluminum, which form volatile chlorides. Chromium chloride, for separation from unreacted ore, is sublimated at a temperature of 000-1-1200 °.

Synthesis of chromium, molybdenum and tungsten carbonyls is carried out by acting on the resulting chlorides with carbon monoxide at temperatures of 100-300 ° and a pressure of 250 atm. Higher in the presence of a reducing agent. Iron, copper, Dyuar alloy, aluminum, magnesium, zinc, etc. in the form of fine sawdust or chips are used as reducing agents. Restarting the reactor to achieve a more complete contact and even distribution of the chlorides are carefully moved with a reducing agent or briquetted.

During the synthesis, the reaction gas (carbon monoxide) is forced to circulate up to 7 exchanges per hour. The carbonyl formed is condensed in cooled collections. Direct extraction of chromium, Lolybden or tungsten from chloride to carbonyl is 70-8CVo. Residues after carbonyl synthesis are nanorubbed for re-chlorination and carbonylation. Considering the revolutions, the recovery of metal from the feedstock to carbonyl is 97.5%.

Purification of the raw carbonyls is carried out in three stages. First, the raw carbonyl is distilled with water vapor to separate the bulk of the impurities, then the distilled carbonyl is moved in a 5-20Vo caustic mill with a solution of caustic soda for 2-3 hours to hydrolyze the volatile foreign metal compounds and then again distilled from water ny steam.

The purified carbonyl is sucked off and dried in a vacuum oven at room temperature over calcium chloride. Product loss in the cleaning operation does not exceed 0 ,. The content of impurities in the purified carbonyls by spectral analysis does not exceed 0 in total.

The thermal decomposition of chromium, molybdenum and tungsten carbonyls is carried out in one of the following four ways, differing in particular in the options for supplying carbonyl to the heated space of the decomposer. In the first embodiment, solid carbonyl is served in

a decomposer above, for example, an Archimedes screw; in the second, a finely ground, solid carbonmel is fed by spraying through a nozzle; thirdly, the carbonyl solution is fed through a KaKoii-jni5o nozzle with a suitable inert liquid; on the fourth - carbonyl vapors are served with heated inert gas.

The thermal decomposition of the carbonyls is carried out at a temperature of 400-1200 ° in the heated zone of the decomposer. Depending on the decomposition temperature, the resulting metallic chromium, molybdenum and tungsten powders have a different carbon content. The smallest carbon content is obtained in the powder, selected by the thermal decomposition of carbopyl at temperatures above 900 °. The creation of a weakly oxidizing agent: osfera in the decomposer also has a positive effect on the reduction of the carbon content in the powder.

Thermal decomposition results in the complete release of metal from carbonyl. Mechanical losses do not exceed 0.5 / o.

To remove carbon, the resulting carbonyl powders of chromium, molybdenum and tungsten are treated in a hydrogen atmosphere or in vacuum at a temperature of 800-1100 °.

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The method of producing carbonyls of chromium metals, molybdenum to tungsten and the production of powders of these metals by thermal decomposition of carbonyls, characterized in that, in order to simplify the technological process of obtaining carbonyls of chromium, molybdenum and tungsten metals, the initial chromium, molybdenum and tungsten metal chlorides process the oxide carbon at 100-300 ° and a pressure of 250 atm and Wipe in the presence of a catalyst of aluminum chloride and (or) benzene vapors or without them and metals of reducing agents, copper, Dewar alloy, al mini, magnesium, zinc and others, and the carbonyls of metals obtained as a result of such a process after their purification are subjected to thermal decomposition, for example, molybdenum carbonyl is decomposed at 300-1200 °, tungsten carbonyl at 300-1000 ° in the presence of carbon dioxide or other inert gas.

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