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CN1418821A - Method for prodn. of chromium oxides and alkali metals bichromate by using ammonium alkali metals chromates as raw materials - Google Patents

Method for prodn. of chromium oxides and alkali metals bichromate by using ammonium alkali metals chromates as raw materials Download PDF

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CN1418821A
CN1418821A CN 02153522 CN02153522A CN1418821A CN 1418821 A CN1418821 A CN 1418821A CN 02153522 CN02153522 CN 02153522 CN 02153522 A CN02153522 A CN 02153522A CN 1418821 A CN1418821 A CN 1418821A
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alkali metal
chromate
dichromate
alkali
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CN1150131C (en
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刘昌见
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Abstract

The method for producing dichlorimium trioxide and alkali dichromate includes the following steps: calcining ammonium chromate alkali metal double salt at 650-1200 deg.C for 0.5-3 hr., then dissolving the calcined product in water and making solid-liquid separation, collecting precipitate dichromium trioxide product; then evaporating and concentrating mother liquor according to conventional method, cooling and crystallizing, and making solid-liquid separation to separate the alkali dichromate as product from alkali chromate as by-product. Said alkali chromate can be returned, and can be utilized circularly. Said dichronium trioxide contains no sulfur, can be used as high-grade raw material for smelting metal chromium, also can be used as pigment and grinding material.

Description

Production of Cr from ammonium chromate alkali metal double salts2O3And alkali metal dichromate
Technical Field
The present invention relates to a process for producing chromium salts in the field of inorganic salt industry, and more particularly to a process for producing chromium sesquioxide and alkali dichromateand chromium sesquioxide from ammonium chromate alkali double salts.
Background
Alkali metal dichromates (sodium or potassium dichromate) are basic products in the chromium salt industry, chromium oxide green (Cr)2O3) Has wide application in the aspects of pigment, abrasive material, smelting metal chromium, and the like. The process for producing alkali metal dichromate which is commonly used in industry at present is to mix chromite and alkali metal carbonate with auxiliary materials such as limestone, dolomite and the like, and then to carry out high temperature treatmentOxidizing roasting, cooling, water soaking to obtain alkali metal chromate solution, acidifying with sulfuric acid, evaporating, crystallizing and eliminating alkali metal sulfate to convert alkali metal chromate into alkali metal dichromate product. The three wastes produced by the process are seriously polluted, except that a large amount of chromium slag and Cr-containing chromium are produced6+In addition to the waste water produced, a large amount of valuable Cr-containing substances is produced6+Alkali metal sulfate of (1).
There are three current methods for producing chromium sesquioxide, the first method is by reacting chromic anhydride (CrO)3) High-temperature calcination for directly preparing Cr2O3The chemical principle is as follows: . The method can produce pigment-grade chromium oxide green, but adopts chromic anhydride as raw material, and calcinates under the high temperature condition of 1100-1300 ℃, so that the raw material price is high, and the cost is overhigh. And as chromic anhydride is generally produced by adopting a concentrated sulfuric acid acidification method, a sodium bisulfate byproduct which is difficult to treat is inevitably generated. The second method is to reduce the dichromate of alkali metals with sulfur or sodium sulfide to produce Cr2O3The chemical principle is as follows: wherein M represents an alkali metal. The method has lower production cost than the first method, but the product has dark color and coarse particles, and is not suitable forThe use as pigments and abrasives as metallurgical raw materials also has the problem of too high sulfur impurities. The third method is to reduce the dichromate of alkali metals by ammonium sulfate or ammonium chloride to prepare Cr2O3The chemical principle is as follows:
or
Wherein M represents an alkali metal. This method is described, for example, in CN1086494 and US 4040860. The method has relatively low production cost and can produce pigment-grade chromium oxide green, but the use amount of ammonium sulfate or ammonium chloride is large, and a large amount of toxic Cr which is difficult to treat is generated6+Alkali metal sulfate ofOr alkali metal chlorides. The use of ammonium sulphate as a reducing agent also leads to a too high content of sulphur impurities in the product.
Disclosure of Invention
The invention aims to research and develop a cleaning process capable of simultaneously producing alkali metal dichromate and chromium oxide green products aiming at the problems of high cost, serious pollution and the like in the current chromium salt production process.
As a result of intensive studies, the present inventors have found that Cr can be simultaneously produced by using an ammonium chromate alkali metal double salt (for example, an ammonium chromate sodium double salt and an ammonium chromate potassium double salt) as a raw material and directly heating and reacting the raw material at 650 to 1200 ℃2O3And alkali metal dichromate. The ammonium chromate alkali metal double salt can be prepared from the corresponding chromate and ammonium salt, and also from ammonium chromate or ammonium dichromate and salts containing alkali metal ions. The present invention has been accomplished on the basis of this finding.
The technical scheme of the invention is as follows:
(1) a process for the production of dichromium trichloride and alkali dichromate salts from ammonium chromate alkali metal double salts,
calcining ammonium chromate alkali metal double salt at the temperature of 650-1200 ℃ for 0.5-3 hours, then dissolving the calcined product with water, carrying out solid-liquid separation, and collecting chromium oxide precipitate serving as a product;
the obtained mother liquor is subjected to evaporative concentration and cooling crystallization by a conventional method, and the alkali metal dichromate as a product is separated from the alkali metal chromate as a by-product by solid-liquid separation.
(2) The method according to claim 1, wherein the alkali metal is sodium or potassium.
The present invention will be described in detail below by taking an ammonium chromate double salt as an example.
When the ammonium chromate sodium is calcined at the temperature of 650-1200 ℃, the following chemical reactions occur:
……(1)
……(2)
……(3)
as can be seen from the above reactions (1) and (2), sodium ammonium chromate is decomposed by heat to simultaneously form Na2Cr2O7And Cr2O3Two kinds of products. As can be seen from reaction (3), Na is produced as a product2Cr2O7Can further react with NH3Reacting to produce Cr as a product2O3And Na as a by-product2CrO4. However, since in the chromium salt industry, Cr is present2O3Is greater than Na2Cr2O7More importantly, the reaction formula (3) is advantageous.
The alkali metal in the above technical means (1) includes sodium and potassium. The behaviors of the ammonium chromate double salt of sodium and potassium in the calcining process are very similar, the thermal decomposition reaction can be finished only by 0.5-3 hours when the ammonium chromate double salt of sodium and potassium is calcined at 650-1200 ℃, and the more the materials are, the longer the required reaction time is. When the thermal decomposition reaction is finished, the calcined product is dissolved by hot water at 50-90 ℃ preferably, and then solid-liquid separation is carried out. The obtained precipitate is chromium oxide, preferably washed with 40-80 deg.C hot water, dried at 50-120 deg.C, and pulverized to obtain chromium oxide green (Cr)2O3) And (5) producing the product. The obtained filtrate contains the alkali metal dichromate as a product and the alkali metal chromate as a by-product, and since the alkali metal dichromate and the alkali metal chromate have different solubilities in water, the separation of the alkali metal dichromate and thealkali metal chromate can be achieved by subjecting the obtained solution to evaporative concentration and cooling crystallization in a conventional manner. It should be noted that the solubility of sodium dichromate is greater than that of sodium chromate, and the solubility of potassium dichromate is less than that of potassium chromate. Therefore, for sodium system using ammonium chromate sodium double salt as raw material, Cr is separated by filtration2O3The solution obtained after precipitation was evaporated to 145. + -. 5 ℃ at which timeAnd after sodium chromate crystals are separated out by filtration, cooling the obtained mother liquor, wherein the separated sodium dichromate crystals are collected as a product by filtration, and the sodium chromate is returned as a raw material of the sodium ammonium chromate for recycling. In addition, for potassium system using ammonium chromate potassium double salt as raw material, filtering to separate Cr2O3The solution obtained after precipitation is concentrated by evaporation, when the soluble solids content of the solution is highAnd when the mass percent of the solution reaches 35-38%, cooling the solution to 5-15 ℃, at the moment, basically separating out all potassium dichromate crystals, and filtering and collecting a potassium dichromate product, wherein the potassium dichromate crystals are still in the solution. The obtained mother liquor contains unreacted potassium chromate, and can be returned to be used as a raw material of potassium ammonium chromate for recycling.
Compared with the prior art in the field, the invention has the following beneficial effects:
1. the alkali metal double salt of ammonium chromate is used as raw material, and only one-step calcination and subsequent dissolution and separation are required, so that two products of alkali metal dichromate and chromium oxide green can be simultaneously produced, and raw materials such as sulfuric acid, dichromate, chromic anhydride, sulfur, ammonium sulfate, ammonium chloride and the like are not used in the process. Simple process and low cost.
2. The method has no by-products such as sulfate and the like, and no waste water and waste gas discharge, and is a clean process.
3. The product has low impurity content and high quality. The dichromate product has no sulfate radical and other impurities, and may be used as high grade material in chromium salt industry. The chromium sesquioxide contains no sulfur, so the chromium sesquioxide can be used as a raw material for smelting high-grade metallic chromium, and can also be used as a pigment and an abrasive.
Drawings
FIG. 1 is a diagram for producing Cr from an ammonium chromate alkali metal double salt2O3And alkali metal dichromate cleaning process flow diagrams.
In fig. 1, after the drying process of the chromium oxide, a pulverizing process (not shown) is preferably added to achieve the desired particle size of the product.
Detailed Description
The present invention will be further described with reference to the following examples, but the present invention is not limited to these examples.
Example 1
Mixing ammonium chromate sodium double salt (NaNH)4CrO4·2H2O)200g, calcining at 850 ℃ for 1 hour, adding 350ml of hot water at 90 ℃ into the reaction product for dissolving, filtering, washing the precipitate with 200ml of hot water, and returning the washing water for recycling. Drying the precipitate to obtain chromium oxide green (Cr)2O3) 18.0g of product. Evaporating the filtrate to concentrate the filtrate to 140 deg.C under normal pressure, separating the precipitated sodium chromate crystals (at which time substantially all of the sodium chromate has been precipitated), and cooling the obtained mother liquor with tap waterHowever, a sodium dichromate crystal (sodium bichromate) product is precipitated at this time, and the sodium bichromate is filtered to be high, so that 14.2g of sodium bichromate is obtained.
Example 2
Mixing ammonium chromate potassium double salt (KNH)4CrO4)173g, calcining at 1000 ℃ for 0.5 hour, adding 350ml of hot water at 90 ℃ for dissolution, filtering, washing the precipitate with 250ml of hot water, and returning the washing water for recycling. Drying the precipitate to obtain chromium oxide green (Cr)2O3) 22.8g of product. The filtrate was concentrated by evaporation, and when the soluble solid content in the solution reached 37 mass%, the solution was cooled to 10 ℃ and separated by filtration to obtain 18.0g of a potassium dichromate product. The obtained mother liquor contains potassium chromate and can be recycled.

Claims (2)

1. A process for the production of dichromium trichloride and alkali dichromate salts from ammonium chromate alkali metal double salts,
calcining ammonium chromate alkali metal double salt at the temperature of 650-1200 ℃ for 0.5-3 hours, then dissolving the calcined product with water, carrying out solid-liquid separation, and collecting chromium oxide precipitate serving as a product;
the obtained mother liquor is subjected to evaporative concentration and cooling crystallization by a conventional method, and the alkali metal dichromate as a product is separated from the alkali metal chromate as a by-product by solid-liquid separation.
2. The method of claim 1, wherein the alkali metal is sodium or potassium.
CNB021535221A 2002-12-02 2002-12-02 Method for prodn. of chromium oxides and alkali metals bichromate by using ammonium alkali metals chromates as raw materials Expired - Fee Related CN1150131C (en)

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011076573A1 (en) 2009-12-22 2011-06-30 Lanxess Deutschland Gmbh Method for producing chromium (iii) oxide
WO2011076574A1 (en) 2009-12-22 2011-06-30 Lanxess Deutschland Gmbh Method for producing ammonium dichromate
WO2011117274A1 (en) 2010-03-23 2011-09-29 Lanxess Deutschland Gmbh Method for producing chromium(iii) oxide
WO2012076564A1 (en) 2010-12-08 2012-06-14 Lanxess Deutschland Gmbh Process for preparing chromium(iii) oxide
EP2468683A1 (en) 2010-12-21 2012-06-27 LANXESS Deutschland GmbH Method for producing alkali metal-ammonium chromate double salts
EP2565162A1 (en) 2011-09-05 2013-03-06 LANXESS Deutschland GmbH Method for producing chromium (III) oxide
CN107176605A (en) * 2017-05-02 2017-09-19 马鞍山华之智信息科技有限公司 A kind of nanometer Cr3C2The preparation method of powder and its application in multi-element alloy coat

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102725231B (en) * 2009-12-22 2014-12-03 朗盛德国有限责任公司 Method for producing chromium (III) oxide
WO2011076574A1 (en) 2009-12-22 2011-06-30 Lanxess Deutschland Gmbh Method for producing ammonium dichromate
WO2011076573A1 (en) 2009-12-22 2011-06-30 Lanxess Deutschland Gmbh Method for producing chromium (iii) oxide
CN104341005A (en) * 2009-12-22 2015-02-11 朗盛德国有限责任公司 Method for producing chromium (iii) oxide
CN102712498A (en) * 2009-12-22 2012-10-03 朗盛德国有限责任公司 Method for producing ammonium dichromate
CN102725231A (en) * 2009-12-22 2012-10-10 朗盛德国有限责任公司 Method for producing chromium (III) oxide
EP2530054A1 (en) 2009-12-22 2012-12-05 LANXESS Deutschland GmbH Method for producing alkali-ammonium chromate double salt
WO2011117274A1 (en) 2010-03-23 2011-09-29 Lanxess Deutschland Gmbh Method for producing chromium(iii) oxide
US9663383B2 (en) 2010-03-23 2017-05-30 Lanxess Deutschland Gmbh Process for preparing chromium(III) oxide
WO2012076564A1 (en) 2010-12-08 2012-06-14 Lanxess Deutschland Gmbh Process for preparing chromium(iii) oxide
US9580333B2 (en) 2010-12-08 2017-02-28 Lanxess Deutschland Gmbh Process for preparing chromium(III) oxide
WO2012085129A1 (en) 2010-12-21 2012-06-28 Lanxess Deutschland Gmbh Method for producing alkali metal ammonium chromate double salts
EP2468683A1 (en) 2010-12-21 2012-06-27 LANXESS Deutschland GmbH Method for producing alkali metal-ammonium chromate double salts
EP2565162A1 (en) 2011-09-05 2013-03-06 LANXESS Deutschland GmbH Method for producing chromium (III) oxide
CN107176605A (en) * 2017-05-02 2017-09-19 马鞍山华之智信息科技有限公司 A kind of nanometer Cr3C2The preparation method of powder and its application in multi-element alloy coat

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