SU426968A1 - METHOD OF OBTAINING SPINELS BASED ON ALUMINUM OXIDE - Google Patents

Description

one

The invention relates to the field of synthesis of compounds of oxides of the type Me, as well as the spinels being synthesized. These compounds possess high heat resistance, chemical resistance, mechanical strength and are widely used in industry (in the technology of abrasives, refractory materials, mineral paints and ceramic products). Some of them are catalytically active and serve as catalysts, others are used as carriers. In the latter case, they must have a sufficient specific surface area and a certain porous structure. These requirements are not always enough to satisfy a sufficiently polio, since the crystal structures, which also include spinels, have a low surface area. In this connection, it is of interest to change the method of spinels obtained in the form of fine powder without additional grinding, which made it possible to increase the specific surface due to dispersion. The so-called “ceramic method, which involves the synthesis of spinels from a mixture of oxides at high temperature, is known. However, Op requires significant energy expenditures to achieve a high product yield due to the specific mechanism of the solid phase reaction. It can be achieved by creating a more intimate contact between each other, their components, for example, the joint dissolution of metal salts and the subsequent crystallization of this mixture with it or coprecipitation from it

hydroxides. In this Cviy4ae, a homomolecular state is obtained, which, when subjected to heat treatment, gives a 100% yield of spinel. However, the advantage of this method, which provides for the interaction between the components, is also its disadvantage, since it requires dissolution — crystallization 1 before calcining. These two operations complicate the technology, are technologically inconvenient, increase energy costs and significantly increase the cost of the product.

The purpose of the invention is to increase the fine dispersion of the powder and ensure the complete yield of the final product.

This is achieved by thermal decomposition at a mixture of stoichiometric amounts of hydroxide of the corresponding divalent metal with

alumoammonium alum. The resulting product is a homogeneous, highly dispersed powder with a particle size of 1 micron. Instead of a hydroxide, a salt of the same metal can be used, decomposing with an oxide at a temperature of 900 ° C.

If, when using hydroxide, the spinel yield is 100%, then in the second case, the yield is reduced by 5-7%. No change in dispersion is observed. Thus, the high dispersion and yield of the product are caused by the use of aluminum-alumina alum for the synthesis of aluminum-containing raw material. The process can be carried out in a rotary or muffle furnace. The proposed method for producing spinels on an alumina-based PA in a highly dispersed state was tested in laboratory conditions.

Example 1. A mixture of 906.7 g A12 (5O4) xX X- (NH4) 2SO4 24H20 and 99.4 g 2p (OD) 2 is calcined in a muffle at 900 ° C for 6 hours. Phase chemical analysis of the product shows a 100% yield of chips 7 pA12O4.

Example 2. A mixture of 906.7 g A12 (504) xX X (IP4) 2504-24П2О and 219.5 g 7p (СНзСОО) 2 is subjected to calcination in a muffle prn 900 ° C for 6 hours. The output of spinel 95%.

Example 3. A mixture of 906.7 g of A12. (8O4) xX (NH4) 2S04 24H20 and 58.3 g of Mg (OH) 2 is heat treated in a muffle at 900 ° C for 6 hours. On the radiograph

product no peaks of free MgO

and aloz.

Example 4. A mixture of 906.7 g A12- (5:04) zX

X (: NH4) 2SO4 24П20 and 93 g of Co (OH) 2 and the irocalyst in a muffle at 900 ° C for 6 hours. X-ray phase analysis did not determine free CoO and ABOz.

Example 5. A mixture of 906.7 g A12 (ZO4) sX

X (NH4) 2S04-24H20 and 92.7 g of Ni (OH) 2 are calcined in a muffle at 900 ° C for 6 hours.

X-ray phage analysis not detected

free NiO and A12Oz.

Subject invention

The method of producing alumina-based spinels by thermal decomposition of mixtures of stoichiometric amounts of aluminum-containing compounds and divalent metal compounds, characterized in that, in order to increase the fine dispersion of the powder and ensure the complete yield of the final product, aluminum-alumina alum is used as the aluminum-containing compound, metals use their hydroxide or salts.