Chromium oxide and preparation method thereof

Abstract

The invention provides chromium oxide and a preparation method thereof. The method includes adding a hexavalent chromium salt solution into a reaction device, injecting a protective gas, sealing the reaction device, increasing the temperature, and after a target temperature is reached, injecting a reducing gas continuously for reaction to obtain mixed paste; subjecting the obtained mixed paste tosolid-liquid separation to obtain chromium oxyhydroxide powder; calcinating the chromium oxyhydroxide powder to obtain the chromium oxide. The chromium oxide and the preparation method thereof have the advantages that a hydrothermal reduction method is applied to prepare the chromium oxide from hexavalent chromium salt, the controllability of the reaction process is enhanced through regulation ofthe reducing gas and the reaction conditions, and the reduction rate can reach more than 99%; obtained reduction products have uniform phases and narrow particle size distribution; the obtained chromium oxide products have high quality and can reach the standards of pigment-grade chromium oxide; the method has a short process, low energy consumption, a low cost and no pollutant emission, thereby being a clean production process with remarkable economic benefits.

Description

technical field [0001] The invention belongs to the technical field of material preparation, and relates to a chromium oxide and a preparation method thereof, in particular to a method for preparing pigment grade chromium oxide by hydrothermal reduction. Background technique [0002] Chromium oxide (Cr 2 o 3 ) is an important industrial raw material, which is widely used in the fields of metallurgy, pigments, ceramics, coatings, green polishing, and organic catalytic synthesis. Currently, the industrial production of Cr 2 o 3 The methods mainly include chromic anhydride thermal decomposition method and hexavalent chromium salt reduction method. The thermal decomposition method of chromic anhydride uses chromic anhydride as raw material and calcines at high temperature to prepare Cr 2 o 3 , this method is expensive and pollutes seriously. The hexavalent chromium salt reduction method uses sulfur or sulfide as a reducing agent to prepare Cr through wet or dry reduction ...

AI Technical Summary

Problems solved by technology

The thermal decomposition method of chromic anhydride uses chromic anhydride as raw material and calcines at high temperature to prepare Cr 2 o 3 , this method is expensive and pollutes seriously

The hexavalent chromium salt reduction method uses sulfur or sulfide as a reducing agent to prepare Cr through wet or dry reduction of hexavalent chromium salt. 2 o 3 , mainly include sodium chromate alkaline liquid sulfur or sodium sulfide reduction method, potassium dichromate sulfur roasting reduction method, sodium dichromate ammonium sulfate reduction method, etc. The above methods have a long process and the introduction of impurity sulfur makes it difficult to obtain high-quality products and other issues, and will produce low value-added by-products in the production process

In this method, the reducing gas is introduced in advance, and then the reaction is heated. The reaction process is difficult to control, resulting in uneven composition of the product, poor performance, and the problem of high reaction temperature and pressure.

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