RU2293605C1 - Method of production of nickel ferrite-chromite (ii) - Google Patents

Abstract

FIELD: methods of production of spinels in chemical industry for production of catalysts.

SUBSTANCE: proposed method of production of nickel ferrite-chromite (II) having structure of spinel includes homogenization of initial material mixture containing nickel (II) oxide, chromium (IV) oxide and dihydrate ferrous oxalate (II). Mixture thus obtained is briquetted and is subjected to heat treatment at temperature of 800-1000°C.

EFFECT: reduction of temperature and duration of process.

1 dwg, 1 tbl, 1 ex

Description

The invention relates to a method for producing spinel and may find application in the chemical industry for the production of catalysts based on nickel (II) chromite ferrites.

A known method of producing ferrite-chromite nickel (II) with a spinel structure [Catalyst Technology / Ed. I.P. Mukhlenova, L .: Chemistry, 1989. - 272 p.], According to which nitrates of nickel (II), iron (III), and chromium (III) are used as starting materials. Each salt is taken in the required amount, dissolved in a certain amount of water and gradually heated to a boil. After water evaporation, the resulting material is calcined at 935 ° C until gas evolution ceases (2-3 hours). The cooled mixture is ground, briquetted and fired at a temperature of 1000-1100 ° C.

The disadvantage of this method of producing nickel (II) chromite ferrites with a spinel structure is environmental pollution by decomposition products of salts, high energy costs for heating and evaporating water.

Closest to the claimed is a method of producing spinel from a mixture of oxides [Cooperative Jan-Teller effect in solid solutions NiFe _2-x Cr _x O ₄ / Ivanov V.V., Kirsanova A.I., Talanov V.M., Shabelskaya N. P. // Izv. Universities. North Caucasus. Region. Natural Sciences. - 1995. - No. 2. - S.34-38], according to which the starting oxides of nickel (II), iron (III), chromium (III) are weighed with an error of 0.0005 g, homogenized for one hour with alcohol in air. Then the oxide mixture is briquetted under pressure P = 15 MPa into tablets with a diameter of 20 mm and calcined at a temperature of 1200-1300 ° C for 90 hours.

The disadvantage of this method is the high heat treatment temperature and the duration of the synthesis, which entails high energy costs.

The authors were faced with the task of developing a method for producing spinels based on transition elements at lower temperatures with a shorter duration, which can significantly reduce energy consumption and, thereby, reduce the cost of their production.

The problem is solved by obtaining ferrite-chromite nickel (II) with a spinel structure by homogenizing the starting oxides of nickel (II), chromium (VI), iron (II) oxalate 2-water and heat treatment of the resulting mixture of substances at a temperature of 800-1000 ° C.

The effect of a change in composition is a decrease in temperature by 300 ° C, a synthesis time of 13 times and is ensured by the formation of a redox reaction

2CrO ₃ + 2FeC ₂ O ₄ · 2H ₂ O = Cr ₂ O ₃ + Fe ₂ O ₃ + 4CO ₂ + 4H ₂ O

oxides of iron (III) and chromium (III) with increased defectiveness and, therefore, high reactivity.

The method consists in producing ferrite-chromite nickel (II) with a spinel structure by dosing the initial oxides of nickel (II), chromium (VI), iron (II) 2-aqueous oxalate. Next, the starting materials are homogenized in an agate mortar for 25 minutes and briquetted into tablets with a diameter of 20 mm under pressure P = 15 MPa. Heat treatment of the samples is carried out for 5-7 hours at a temperature of 800-1000 ° C.

Example (general production procedure). 0.0005 g of the amount of nickel (II) oxide (1.6199 g), iron (II) oxalate of 2-aqueous (3.9019 g), chromium (VI) oxide (2.1688 g) was weighed out with an error. The mixture was homogenized for 25 minutes in an agate mortar. The resulting mixture was briquetted into tablets with a diameter of 20 mm under a pressure of 15 MPa, placed in a muffle furnace and subjected to heat treatment at a temperature of 900 ° C for 7 hours.

The end of the process of forming the structure of the spinel of the composition NiFeCrO _{4 was} determined using x-ray phase analysis: the spinel synthesis was 100% (the x-ray of the sample (drawing) contains only lines characterizing the spinel). The chemical composition of the synthesized spinel is shown in table 1.

As can be seen from the above example, the method of producing spinel based on transition elements with the participation of the redox process allows to obtain spinel at a lower temperature and in less time compared to the process using traditional technology. This can significantly reduce energy consumption and, thereby, reduce the cost of production of spinels based on transition elements.

Table 1.
The chemical composition of the spinel NiFeCrO ₄ Oxide Nio Fe ₂ O ₃ Cr ₂ O ₃ Content, wt.% 32,40 34.64 32.96

Claims (1)

A method of producing nickel (II) ferrite chromite with a spinel structure, comprising homogenizing a mixture of starting materials containing nickel (II) oxide, briquetting and heat treatment, characterized in that chromium (VI) oxide and iron (II) oxalate are introduced into the starting material mixture 2-water, and heat treatment is carried out at 800-1000 ° C.