RU2376244C1 - Calcium aluminate synthesis method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of producing calcium aluminate involves mixing calcium hydroxide with aluminium metal powder, where water is added in amount of 19 to 40% of its content in the mixture at the mixing step. The obtained mixture is mechanically activated, and the obtained product is thermally treated once at temperature ranging from 700 to 900°C.

EFFECT: increased specific surface area in 1,57-1,67 times, cutting on number of process steps, prevention of formation of waste water.

1 tbl, 4 ex

Description

FIELD OF TECHNOLOGY

The invention relates to the field of chemical technology and can be used to obtain hydroxyaluminates and spinels of metals of group II, used for the preparation of catalysts and carriers.

BACKGROUND

A known method of producing magnesium aluminate for the production of ceramics, based on annealing a mixture of magnesium sulfates and aluminum in the presence of metal fluorides (AS USSR No. 1196333, MKI C01F 7/16, decl. 30.12.83, publ. 07.12.85, bull. No. 45).

A significant disadvantage of the analogue is the allocation of harmful gaseous wastes during heat treatment of the initial mixture

A known method of preparing calcium-aluminate material by mixing lime and an alkaline solution of sodium aluminate, keeping it for 1-5 hours at 15-90 ° C, filtering, washing the precipitate from alkalis and firing. This method is characterized in that in order to obtain highly basic calcium aluminates with astringent properties, firing is carried out at 1000-1100 ° C for 1-3 hours (A.S. No. 854905, С04В 7/32, publ. 15.08.81, B.I. No. 30, 1981).

The disadvantages of the analogue include the complexity and long duration of the process, the need to use a large amount of water for washing, which in the future must be cleaned.

A known method of producing metal aluminate, including mixing the starting components taken in stoichiometric terms, mechanical activation and heat treatment, and when preparing the mixture of the starting components, an aluminate seed corresponding to the obtained one is introduced into it, the prepared mixture is first subjected to preliminary mechanical activation in a centrifugal planetary mill followed by heat treatment at 700-900 ° C, and then re-mechanical activation and heat treatment at 1200-1400 ° C (RF Patent No. 2108292, publ. 04/10/1998, Bulletin No. 10).

The disadvantages of the analogue include the low specific surface area of the obtained aluminate, the need to introduce seeds into the initial mixture, the significant length of the technological process of preparation, and the energy intensity of the process, due to the presence of the stage of high-temperature calcination of samples requiring the use of high-temperature furnaces.

The closest to the proposed invention in technical essence and the achieved result, that is, the prototype is a method for producing calcium hydroaluminate, comprising treating a reagent containing aluminum oxide with lime, followed by separation of the precipitate formed, which is then washed with hot water and subjected to heat treatment at 290-510 ° C within 1-10 hours (AS USSR SU 704019, publ. 12/30/1986, bull. No. 48).

The disadvantages of the prototype include the insufficiently high specific surface area of the resulting product, the multi-stage process, the need to use a large amount of water to wash the precipitation, which must be further cleaned.

SUMMARY OF THE INVENTION

The objective of the invention is to provide a method for producing calcium aluminate, used for the production of catalysts and supports with a higher specific surface area while reducing the number of technological operations and eliminating the formation of wastewater containing impurities.

The problem is solved in the proposed method for producing calcium aluminate, comprising mixing calcium hydroxide with an aluminum-containing component with the addition of water, moreover, aluminum metal powder is used as an aluminum-containing component, water is added in an amount of 19-40% of its content in the mixture, the resulting mixture is subjected to mechanical activation and the resulting product is subjected to heat treatment once at 700-900 ° C

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

Example 1

To prepare the product according to the proposed method, aluminum metal powder, calcium hydroxide and water are used.

Upon receipt of 100 g of calcium aluminate, 34.2 g of aluminum metal, 46.8 g of calcium hydroxide are loaded into the drum of a VM-4 vibration mill, and 19 g (19 wt.%) Of water are added and activated for 60 minutes. Then the resulting product is calcined for 6 hours at a temperature of 900 ° C. Composition of the product

Al ₂ O ₃ · CaO.

Example 2

To obtain 100 g of calcium aluminate, a mixture is prepared consisting of 41.5 g of aluminum metal powder, 28.5 g of calcium hydroxide Ca (OH) ₂ and 32 g (31.3 wt.%) Of water, which is then loaded into a drum of a vibration mill VM-4 and subjected to processing for 60 minutes. Next, the resulting product is calcined for 6 hours at a temperature of 700 ° C. The composition of the product is 2Al ₂ O ₃ · CaO.

Example 3

To obtain 100 g of calcium aluminate, a mixture is prepared consisting of 37.9 g of aluminum metal powder, 37.6 g of calcium hydroxide and 30 g (28.4 wt.%) Of water are added. The resulting mixture was loaded into a drum of a VM-4 vibration mill and activated for 60 minutes. Next, the resulting product is calcined for 6 hours at a temperature of 800 ° C. The composition of the product is Al ₂ O ₃ · CaO, 2Al ₂ O ₃ · CaO.

Example 4

To obtain 100 g of calcium aluminate, a mixture is prepared consisting of 37.9 g of aluminum metal powder, 37.6 g of calcium hydroxide and 50.4 g (40.0 wt.%) Of water are added. The resulting mixture was loaded into a drum of a VM-4 vibration mill and activated for 60 minutes. Next, the resulting product is calcined for 6 hours at a temperature of 900 ° C. The composition of the product is Al ₂ O ₃ · CaO, 2Al ₂ O ₃ · CaO.

The specific surface was measured by the method of low-temperature adsorption (desorption) of argon on a helium-argon mixture with an accuracy of at least 15% on a Tsvet 211 sorbometer according to the method described in the work: Physicochemical use of gas chromatography. / A.V. Kiselev, A.V. Iogansen, K.I. Sakodynsky and others - M .: Chemistry, 1973. - 256 p.

The results of the tests are presented in the table.

Example No. The number of technological operations Specific surface, m ² / g one 3 6.4 2 3 7.0 3 3 6.9 four 3 6.8 Prototype 6 4.2

The table shows that the use of the claimed invention allows to increase the specific surface area of calcium aluminate by 1.53-1.67 times and halve the number of technological operations. In addition, the invention eliminates the formation of wastewater containing harmful impurities.

Claims (1)

A method of producing calcium aluminate, comprising mixing calcium hydroxide with an aluminum-containing component, wherein at the mixing stage water is added, characterized in that aluminum metal powder is used as an aluminum-containing component, water is added in an amount of 19-40% of its content in the mixture, the resulting mixture is subjected mechanical activation and the resulting product is subjected to heat treatment once at 700-900 ° C.