Method of preparing chromium oxide by reducing chromate with gaseous reducing agent at low temperature

A reducing agent, chromium oxide technology, applied in the direction of chromium oxide/hydrate, etc., can solve the problems of high reaction temperature, defective crystals, and great environmental harm, and achieve the advantages of simple production process, reduced reaction energy consumption, and reduced production cost. Effect

Inactive Publication Date: 2007-02-07
中蓝义马铬化学有限公司
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  • Abstract
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  • Application Information

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Problems solved by technology

[0009] The purpose of the present invention is to overcome in the existing method for preparing chromium oxide, use chromic anhydride pyrolysis method production cost is very high, and can produce a lot of poisonous gas and acid mist, very harmful to environment; Use sodium chromate alkaline The purity of the product obtained by the liquid sulfur reduction method is low, the crystal has defects, and the color is gray-green, which is not suitable for pigments and abrasives; the cost of the sulfur reduction method using potassium dichromate is too high; when using the thermal decomposition method of sodium dichromate and ammonium sulfate, The resulting chromium oxide has high sulfur content and poor pigment performance; using the hydrogen reduction method disclosed in the previous two patents, the reaction temperature is too high, the energy consumption is large, and the reaction equipment is complicated. A method for preparing chromium oxide by using a gas reducing agent to reduce chromium salts at low temperature to reduce toxic gases and acid mist that pollute the environment, high product purity, low reaction energy consumption, and simple equipment

Method used

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  • Method of preparing chromium oxide by reducing chromate with gaseous reducing agent at low temperature
  • Method of preparing chromium oxide by reducing chromate with gaseous reducing agent at low temperature
  • Method of preparing chromium oxide by reducing chromate with gaseous reducing agent at low temperature

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Effect test

Embodiment 1

[0025] Weigh 15g of potassium dichromate into a material boat, put it into a tube furnace, raise the temperature to 300°C, and feed in hydrogen gas, the amount of hydrogen gas introduced is 60L / h, and react for 2 hours. After cooling down naturally, take out the reaction mixture , washed with water and filtered, dried the filter cake, and calcined in a muffle furnace for 2 hours at 400°C for thermal decomposition to obtain ultrafine chromium oxide powder with a purity of 97.9% and a particle size of about 0.2um. The scanning electron microscope photo is as follows figure 1 shown.

Embodiment 2

[0027] Weigh 15g of sodium chromate in a material boat, put it into a tube furnace, raise the temperature to 850°C, feed natural gas, the amount of natural gas fed is 60L / h, react for 30min, after natural cooling, take out the reaction mixture , washed with water and filtered, dried the filter cake, and calcined in a muffle furnace at 1100°C for 1 hour to obtain a chromium oxide powder with a purity of 99.1% and a particle size of 0.2-0.4um. The scanning electron microscope photo is as follows: figure 2 shown.

Embodiment 3

[0029] Weigh 15g of potassium dichromate in a material boat, put it into a tube furnace, raise the temperature to 400°C, feed gas, the amount of gas fed is 60L / h, react for 3h, after natural cooling, the reaction mixture Take it out, wash and filter with water, dry the filter cake, and then calcinate it in a muffle furnace at 700°C for 3 hours to obtain a chromium oxide powder with a purity of 98.5% and a particle size of 0.5um.

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Abstract

This invention involves a preparation method for chromium oxide with chromium salt as raw materials and reducing gas as a reductant. Said method comprises carrying out reaction of chromium salt with superfluous reducing gas at 300~850DEG C for 0.5-3 h and cooling to obtain a reaction mixture, washing the mixture and drying, and calcining at 400~1100DEG C for 1-3 h to obtain the ultrafine chromium oxide powders, wherein the chromium salt is chromate or dichromate, and the reducing gas is hydrogen, natural gas, gas or their mixtures. Compared with existing technologies, this invention has the advantages of simple production process and being easy for industrialization. The obtained chromium oxide has high purity, uniform particle size distribution and small particle size. The whole process does not produce containing chromium-containing waste, and is environmental friendly. The reaction by-product can be reused, which greatly reduces the cost of production. Low reaction temperature greatly reduces the reaction energy.

Description

technical field [0001] The invention relates to a method for preparing chromium oxide, in particular to a method for preparing chromium oxide by reducing chromium salt with a gas reducing agent at low temperature. Background technique [0002] Chromium oxide is one of the leading products in the chromium salt industry. It is widely used in pigments, abrasives, refractory materials, raw materials for smelting metal chromium, and catalysts in organic synthesis. According to different uses, the requirements for chromium oxide products are also different. For example, when used in pigments, there are high requirements for the color performance and particle size of chromium oxide, but the requirements for its purity are relatively low. Sometimes in order to improve its color performance, some other additives need to be added. When used as a metallurgical raw material, there is a high requirement for the purity of chromium oxide, especially for alkali metal ions and sulfur conten...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01G37/02
Inventor 徐红彬白玉兰张懿李佐虎
Owner 中蓝义马铬化学有限公司
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