Method of producing chromium (iii) oxide

FIELD: chemistry.

SUBSTANCE: invention relates to chemistry and can be used for production of pigment for construction materials, plastic, paint and lacquer, glass and ceramics. Sodium monochromate reacts with ammonia gas at temperature of 200-800 C. Hydrolysis of reaction product is carried out. Water pH is reduced before hydrolysis or pH of alkaline mother liquor is reduced during or after hydrolysis to 4-11 by adding carbon dioxide. Precipitated hydrolysis product is separated at pH = 4-11. Hydrolysis product is calcined at 700-1,400 C.

EFFECT: invention enables production of chromium (III) oxide, containing very small amount of sulphur and alkali metals and by-products.

12 cl, 3 ex

 



 

Same patents:

FIELD: chemistry.

SUBSTANCE: chromium phosphate is obtained in a reactor by dissolving chromium trioxide in water. Orthophosphoric acid and a stabilising additive - ethanol - are then added. A strong reducing agent - aqueous hydrazine-hydrate solution - is slowly added to the obtained mixture of chromic acid, orthophosphoric acid and ethanol in an amount which enables formation and maturation of chromium phosphate particles, suspension pH of 4-7 and concentration of chromium phosphate of 50-100 g/cm. The end product is then filtered and dried. The filtrate is returned to preparation of the mixture of chromium trioxide, orthophosphoric acid and ethanol.

EFFECT: invention simplifies the technique and completely prevents formation of waste water.

1 tbl, 6 ex

FIELD: chemistry.

SUBSTANCE: described is a method of making chromate anticorrosive pigment involving suspension of spent chrome-aluminium catalyst in aqueous solution of calcium nitrate and barium nitrate, taken in amount of 10-30% and 5-25% of the mass of catalyst respectively, in mass ratio of catalyst to the said nitrates equal to 65-70:30-35 respectively, dehydration of the obtained mixture with subsequent calcination at 800-900C for 3-6 hours and grinding. The obtained pigment has anticorrosive effectiveness which surpasses that of the closest analogue by 6-40% and has lower cost.

EFFECT: use of pigment in ground coating improves anticorrosive properties of the coating and increases environmental friendliness.

1 cl, 1 tbl, 15 ex

FIELD: chemistry.

SUBSTANCE: method of producing emerald chrome pigment involves calcination of a mixture containing chromic anhydride, boric acid and urea, subsequent washing and drying the pigment. The mixture is calcined at temperature 750-800C for 0.5-1.0 hours to obtain a melt which is boiled with addition of boric acid in mass ratio of melt to solution equal to 1:6. The mixture has the following weight ratio of ingredients: chromic anhydride - 20 pts. wt, boric acid - 60-80 pts. wt, urea - 3-4 pts. wt.

EFFECT: obtaining green pigment with a tinge of emerald green.

1 ex

FIELD: paint and varnish industry.

SUBSTANCE: anticorrosive pigment comprises , in mass per cents, 3.0-4.7 of calcium chromate and waterless dicalciumphosphate as the balance.

EFFECT: improved anticorrosion capabilities.

1 tbl

The invention relates to the technology for anti-corrosive pigments, for example, in the paint industry

The invention relates to methods for pigments containing chromium phosphate, used in the paint industry

The invention relates to the technology for anti-corrosive pigments used in the paint industry

The invention relates to the technology of production of pigments containing

The invention relates to the production of chromium oxide (III) used in the paint industry and for polishing

FIELD: chemistry.

SUBSTANCE: invention relates to production of chromic anhydride and can be used in the chemical industry. The method of producing chromic anhydride from a highly concentrated solution of sodium bichromate involves reacting sodium bichromate with sulphuric acid in a reactor with direct contact of the reaction mass with flue gas, obtained from burning natural gas, accompanied by melting the formed chromic anhydride and sodium bisulphate, and subsequent separation of chromic anhydride and sodium bisulphate by settling. Highly concentrated solution of sodium bichromate is treated with flue gas from burning natural gas with direct contact of flue gas with the solution, with formation of a solid phase consisting of anhydrous crystals of sodium bichromate.

EFFECT: cutting on contact time of reaction mass with flue gas in the reactor, smaller size of the reactor, increased intensity of the process and output of the product, improved corrosion conditions for operation of the reactor.

7 cl, 2 dwg

FIELD: chemistry.

SUBSTANCE: present invention can be used in making chromium anhydride, used in chemical, paint and coating, textile, metallurgical and other industries. The method of producing chromium anhydride involves leaching a chromite concentrate at 140-160 °C with a mixture of 60-62% sulphuric acid and a catalyst - chromium anhydride. The suspension undergoes centrifugal separation. Chromium sulphate, obtained from leaching, is oxidised to chromic acid through electrolysis. The electrolyte solution is evaporated at 140-150 °C temperature until 950-1100 g/l concentration of sulphuric acid in the evaporated solution is achieved. Crystals of chromium anhydride are separated from the mother solution through centrifugal separation and the end product is dried. Before sulphuric acid leaching, the chromite concentrate is concentrated through gravitation. The amount of catalyst when leaching is 70-100% of content of iron (II) oxide in the chromite concentrate. After separation from the mother solution, chromium anhydride crystals are further washed in sulphuric acid with 60-62% concentration at 140-150 °C.

EFFECT: invention allows for obtaining chromium anhydride from poor ore mixtures with high product output and low content of impurities.

4 tbl, 10 ex

FIELD: isomerization and disproportionation catalysts.

SUBSTANCE: invention relates to crystalline α-chromium oxide, chromium-containing catalytic compositions, method for preparation thereof, and to a process of fluorine distribution in hydrocarbon and/or halogenated hydrocarbon in presence of indicated catalytic compositions. In claimed α-chromium oxide, about 0.05 to about 2 atomic % chromium in the lattice of α-chromium oxide is substituted by nickel atoms and, optionally, further chromium atoms in the lattice are substituted by trivalent cobalt atoms, the total amount of nickel and trivalent cobalt atoms in the α-chromium oxide lattice not exceeding 6 atomic %. Claimed α-chromium oxide is prepared via coprecipitation of solid substance by introducing ammonium hydroxide, this method being supplemented by introducing an excess of ammonium nitrate into precipitated mixture before dehydration step and calcination step at 375 to 1000°C in presence of oxygen. Chromium-containing catalytic compositions containing crystalline nickel-substituted α-chromium oxide as chromium-containing component optionally treated with fluorination agent are also claimed. Composition preparation procedure comprises: (a) coprecipitation of solid substance by introducing ammonium hydroxide into aqueous solution of soluble bivalent nickel salt, soluble trivalent chromium salt, and optionally soluble bi- or trivalent cobalt salt, wherein solution contains at least three moles nitrate per mole chromium and has concentration of nickel from about 0.05 to about 2 mol % based on total content of nickel, chromium, and cobalt (if present) in solution and total concentration of nickel and cobalt (if present) not higher than 6 mol % on the same basis; (b) collecting coprecipitated solid substance obtained in step (a); (c) drying collected solid substance; and (d) calcination of dried solid substance at 375 to 1000°C in presence of oxygen.

EFFECT: increased activity of catalytic composition in above-indicated processes.

15 cl, 8 dwg, 13 ex

FIELD: isomerization and disproportionation catalysts.

SUBSTANCE: invention relates to crystalline α-chromium oxide, chromium-containing catalytic compositions, methods for preparation thereof, and to a process of fluorine distribution in hydrocarbon and/or halogenated hydrocarbon in presence of indicated catalytic compositions. Claimed crystalline α-chromium oxide, wherein about 0.05 to about 6 atomic % chromium in the lattice of α-chromium oxide is substituted by trivalent cobalt (Co+3) atoms is via coprecipitation of solid substance by introducing ammonium hydroxide, this method being supplemented by introducing an excess of ammonium nitrate into precipitated mixture before dehydration step and calcination step at 375 to 1000°C in presence of oxygen. Chromium-containing catalytic compositions containing crystalline cobalt-substituted α-chromium oxide as chromium-containing component optionally treated with fluorination agent are also claimed. Composition preparation procedure comprises: (a) coprecipitation of solid substance by introducing ammonium hydroxide into aqueous solution of soluble cobalt salt and soluble trivalent chromium salt, wherein solution contains at least three moles nitrate per mole chromium and has concentration of cobalt from about 0.05 to about 6 mol % based on total content of cobalt and chromium in solution, followed by introducing into solution at least three moles ammonium per mole chromium; (b) collecting coprecipitated solid substance obtained in step (a); (c) drying collected solid substance; and (d) calcination of dried solid substance at 375 to 1000°C in presence of oxygen.

EFFECT: increased activity of catalytic composition in above-indicated processes.

15 cl, 8 dwg, 13 ex

FIELD: chemistry.

SUBSTANCE: invention can be used in production of cutting instrument, in wear-resistant overlaying welding, for obtaining composite electrochemical coatings and contact material, possessing higher resistance to erosive impact of electric arc. Method of obtaining chrome carbide includes heating charge from mixture of chrome (III) oxide and carbon to temperature 1100-1350C. Chrome oxide (III) and carbon are taken in weight ratio 74.5:25.5. The process is carried out in crucible from glassy carbon under atmospheric pressure.

EFFECT: invention makes it possible to simplify the process and prevent partial oxidation of charge carbon.

2 cl

FIELD: physics.

SUBSTANCE: magnetic semiconductor material is a compound of chromium, gallium and copper selenide having chemical formula CuGaCr2Se5 and characterised by Curie point of 318K.

EFFECT: invention enables to obtain material with Curie point higher than room temperature, having ferromagnetic and semiconductor properties.

1 dwg, 2 ex

FIELD: chemistry.

SUBSTANCE: chromium (VI) ions are extracted from acidic aqueous solutions with the protonated form of N',N'-dipentylhydrazide 2-ethylhexanoic acid in form of its salt with sulphuric acid or hydrochloric acid in kerosene. Concentration of sulphuric acid is greater than 3.5 mol/l and concentration of hydrochloric acid is greater than 4 mol/l. A modifier - 0.04% solution of 2-ethylhexanol is used to prevent formation of a third phase.

EFFECT: more efficient extraction of chromium in strongly acidic media, simple process and wide range of extraction reagents.

5 tbl, 4 ex

FIELD: chemistry.

SUBSTANCE: freshly deposited and washed chromium hydroxide in mass ratio Cr6+/Cr3+=1.9-2.1 is added to a solution of chromic anhydride with concentration CrO3 350-450 g/l and temperature ranging from 70 to 90C. The mixture is boiled for 1.5 to 2 hours until attaining pH of not less than 1.3. The suspension is filtered from the insoluble residue. The obtained solution is boiled for 20 minutes to 1 hour and cooled to room temperature. The obtained basic bichromate of trivalent chrome and silica sol are used in the composition for chrome treatment of metal surfaces. Concentration of Cr6+ in the mixture ranges from 45 to 55 g/dm3, concentration of Cr3+ - 21.8 to 26.8 g/dm3, concentration of silica sol ranges from 16 to 130 g/dm3 in terms of SiO2, and the size of the particles of the silica sol ranges from 5 to 300 nm.

EFFECT: obtaining a strong and uniform film on metal surfaces, which has polymer properties, not prone to cracking and is suitable for depositing polyethylene coating.

3 cl, 1 ex

FIELD: chemistry.

SUBSTANCE: scope of invention is development of new sulphide compounds with specific magnetic and electric properties for use in microelectronics. Magnetic vanadium disulphide of chromium-copper with gigantic magnetic resistance includes sulphur, vanadium, chrome and copper with the following component ratio, atomic %: vanadium 0.1-3.4, chrome 13.6-16.9, copper 16-17, and sulphur 66-67.

EFFECT: obtained substance possesses high intensity of magnetism and gigantic negative magnetic resistance.

2 tbl, 2 dwg

The invention relates to electroplating and can be used in the processing of chromiferous solutions resulting from the electrochemical and chemical treatment of metals using chemical methods

The invention relates to methods of producing chromium compounds
The invention relates to inorganic chemistry
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