Process for preparing chromic oxide by hydrothermal reducing sodium chromate or sodium acid chromate

A technology of sodium dichromate and sodium chromate, applied in the field of inorganic salt industrial production, can solve the problems of high price and high toxicity of low-molecular organic matter, and achieve the effects of low cost, easy filtration and washing, and mild reaction conditions

Inactive Publication Date: 2009-06-17
CENT SOUTH UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

In addition, the price of low-molecular organic substa

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0037] In autoclave, add 3000g sodium chromate, 7000g of mother liquor of crystallization, cornstarch 412.5g (according to stoichiometric molar ratio, be 110% of sodium chromate), be heated to 200 ℃, reaction time 2 hours, stirring speed 200rpm, obtain The slurry is easy to filter and separate. The separated chromium hydroxide wet filter cake does not need to be washed or dried, and is directly roasted in a roasting furnace or a rotary kiln at 800-900°C for 2 hours. The cooled chromium oxide is dispersed with a mechanical mill, and the dispersed chromium oxide is turned into a slurry with deionized water at 80°C. The slurry is statically reverse washed 6 times on a mobile disc filter, and the filter cake is at 150-160 °C for 4 hours to obtain the finished chromium oxide. The mother liquor after slurry separation is evaporated and crystallized to obtain solid mixed alkali; the solid mixed alkali is returned to the chromite ore intensified roasting process to realize the recycl...

Embodiment 2

[0039] In the autoclave, add 2000g sodium chromate, crystallization mother liquor 4153g, oxidized starch 300g (according to stoichiometric molar ratio, be 120% of sodium chromate), be heated to 180 ℃, reaction time 3 hours, stirring speed 500rpm, obtain Slurry is easy to filter and separate. The separated chromium hydroxide wet filter cake does not need to be washed or dried, and is directly roasted in a roasting furnace or a rotary kiln at 800-900°C for 2 hours. The cooled chromium oxide is dispersed with a jet mill, and the dispersed chromium oxide is turned into a slurry with deionized water at 85°C. The slurry is statically reverse washed 5 times on a mobile disc filter, and the filter cake is at 150-160 °C for 4 hours to obtain the finished chromium oxide. After the slurry separation, the mother liquor is evaporated, crystallized and separated to obtain a solid mixed alkali; the solid mixed alkali is returned to the chromite ore intensified roasting process to realize th...

Embodiment 3

[0041] Add 1000g sodium dichromate, crystallization mother liquor 1667g, yellow dextrin 200.9g (according to stoichiometric molar ratio, be 130% of sodium dichromate) in autoclave, be heated to 150 ℃, reaction time 3 hours, stirring speed 1200rpm, the resulting slurry is easy to filter and separate. The separated chromium hydroxide wet filter cake does not need to be washed or dried, and is directly roasted in a roasting furnace or a rotary kiln at 800-900°C for 2 hours. The cooled chromium oxide is dispersed with a mechanical mill, and the dispersed chromium oxide is turned into a slurry with deionized water at 90°C. The slurry is statically reverse washed 4 times on a fixed-chamber belt filter, and the filter cake is at 150-160 °C for 4 hours to obtain the finished chromium oxide. After the slurry separation, the mother liquor is evaporated, crystallized and separated to obtain a solid mixed alkali; the solid mixed alkali is returned to the chromite ore intensified roasting...

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Abstract

The invention relates to technology for preparing chromium oxide through hydrothermal reduction of sodium chromate or sodium dichromate, which comprises: preparing the sodium chromate or the sodium dichromate into an aqueous solution, placing the aqueous solution and starch or starch derivatives into a high-pressure reaction kettle for hydrothermal reduction, and obtaining chromic hydroxide slurry; filtering and separating the chromic hydroxide slurry to obtain chromic hydroxide filter cakes and a chromic hydroxide mother solution; and performing high-temperature roasting on the filter cakes to obtain chromium oxide products. The technology has short technological flow, simple operation, low cost and mild reaction conditions, and does not have overhigh requirements on equipment; not only the product quality is better than that of the prior method but also the reduction and conversion rate of sexavalent chromium reaches more than 98 percent; and the whole technology forms a closed cycle, realizes recycling of mixed alkali, the mother solution and a washing liquid, does not discharge pollutant in any form during the whole process, and fundamentally avoids pollution.

Description

technical field [0001] The invention relates to a process for preparing chromium oxide by hydrothermally reducing sodium chromate or sodium dichromate by using starch or its derivatives as a reducing agent, which belongs to the field of industrial production of inorganic salts. Background technique [0002] Chromium oxide, sodium dichromate, chromic anhydride, and basic chromium sulfate are the four major products of chromium salt, and the production of commercial chromium oxide accounts for about 20% of the consumption of sodium dichromate. The main uses of chromium oxide are divided into five categories: metallurgy, pigments, abrasives, refractory materials and newly developed melt-blown coatings. In addition, chromium oxide is also used as a catalyst and its carrier, for the production of composite oxides, and as a raw material for the production of carbon, nitrogen, boron, and silicide of chromium. [0003] At present, there are two methods for preparing chromium oxide ...

Claims

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Application Information

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IPC IPC(8): C01G37/02
Inventor 徐文彬周秋生彭志宏刘桂华齐天贵李小斌
Owner CENT SOUTH UNIV
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