RU2450972C1 - Method of producing zinc oxide powder - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of producing zinc oxide powder by oxidising zinc with oxygen while heating, where zinc metal first undergoes distillation at temperature lower than boiling point in a stream of an inert gas; the obtained powder is oxidised in a revolving reactor with a controlled atmosphere at temperature lower than the boiling point of zinc.

EFFECT: invention enables to obtain zinc oxide powder containing less impurities than the starting metal using commercial-grade zinc metal and industrial oxygen as starting materials.

3 cl

Description

The invention relates to the field of synthesis of inorganic compounds, and in particular to a method for the synthesis of zinc compounds and, in particular, to a method for the synthesis of zinc oxide.

Known methods for the synthesis of zinc oxide by decomposition of zinc compounds, in particular by oxidative thermal decomposition of oxalate (RU 2206508 C1) or by thermal decomposition of nitrate (RU 2047556 C1). However, these methods require the use of additional starting compounds, and the resulting oxide may contain products of incomplete decomposition of the precursor.

The electrochemical oxidation of metallic zinc (RU 2221748 C1) is multistage and also requires the use of additional starting compounds, which greatly complicates the process of obtaining a high-purity zinc oxide powder.

The closest adopted for the prototype is a method for the synthesis of zinc oxide during oxidation by oxygen of air of zinc metal vapor in a cyclone furnace at a temperature above 1300 ° C (RU 2077158 C1). The main disadvantage of this method is the use of high temperatures, which, due to the high reactivity of the zinc metal vapor, inevitably leads to contamination of the resulting powder by the products of interaction with the material of the equipment used.

The objective of the invention is to develop a method that, when used as starting commodity metallic zinc and industrial oxygen, to obtain a powder of zinc oxide, the content of impurities in which is lower than in the original metal.

The technical result of the invention is to obtain a high-purity powder of zinc oxide, the content of impurities in which is lower than in the starting metal.

The technical result is achieved by the fact that metal zinc is subjected to distillation at a temperature below the boiling point in an inert gas stream, the obtained powder is subjected to oxidation in a rotary reactor with a controlled atmosphere at a temperature below the boiling point of zinc, and the fact that the inert gas stream is carried out in a closed loop and using a quartz glass reactor.

Distinctive features of the method are: a preliminary stage of purification and production of zinc powder by distillation, oxidation in a rotating reactor with a controlled atmosphere, an inert gas flow in a closed loop, the use of a quartz glass reactor.

Oxidation of the zinc melt by oxygen is complicated by the formation of a dense surface oxide film, however, the oxidation of the metal powder in a rotating reactor allows ZnO powder to be obtained. It is advisable to combine the stage of obtaining the metal powder with the purification of zinc by distillation.

In commercial grade CV 0 grade zinc, from element impurities determined using laser-induced mass spectrometry (the method allows determining the content of at least 60 element impurities), iron has the highest content. Its concentration is several times higher than the content of any other of the determined element impurities. Distillation at an evaporator temperature above the boiling point of zinc (907 ° C) seems to be the simplest technological solution, however, purification from iron, which is mainly contaminated with the starting zinc, is not effective enough.

When the evaporator temperature drops to 850 ° C, the iron removal efficiency increases by more than an order of magnitude. The dispersion of the resulting powder is determined by the inert gas flow rate supplied to the evaporator. To reduce the cost of the required amount of inert gas supplied to the evaporator, it is advisable to use a compressor to provide a gas flow in a closed loop.

By treating the obtained zinc powder with oxygen in a rotating reactor, oxide powder is obtained. The rotation of the reactor, leading to the mixing of the reaction mixture, is a simple and effective technique, facilitating the complete oxidation of the metal. During the oxidation of zinc by oxygen, a large amount of heat is generated, which leads to the heating of the reaction mixture up to the destruction of the walls of the reactor. Controlling the rate of oxygen supply to the reaction mixture makes it possible to limit the rate of heat release of the zinc oxide synthesis reaction, which reduces the possibility of local overheating of the reaction mixture. The controlled oxygen supply to the reactor and the constant mixing of the reaction mixture due to the rotation of the reactor significantly reduce the likelihood of local overheating and, as a consequence, the probability of destruction of the walls of the reactor.

The use of oxygen is due to its greater oxidizing ability and the ability to exclude contamination of the product with nitrogen compounds, which is especially important in the synthesis of high-purity zinc oxide.

A typical example: during the preliminary stage of purification and obtaining fine zinc powder, 400 g of zinc of qualification CV 0 are loaded into the evaporator, pure argon is supplied at a speed of 100 l / h. Turn on the heating of the evaporator. During the process, the temperature in the evaporator is kept at 850 ° C. The gas leaving the evaporator is cooled and filtered. All vaporized metal is deposited on the filter in the form of a powder. Using a compressor, argon is again fed to the evaporator after filtration. The process is conducted within 12 hours. In this case, ~ 300 g of metal evaporates. Then, after cooling to room temperature, the evaporator is unloaded, zinc powder is collected from the filter. The resulting zinc powder is further oxidized in a rotary atmosphere controlled reactor.

The synthesis of zinc oxide powder is carried out in a tubular reactor with a working volume of ~ 0.5 l. 0.3 kg of zinc powder is charged into the reactor; heating and rotation are included. The synthesis of oxide is carried out at 650 ° C and an oxygen supply rate of 10 l / h.

To determine the degree of zinc purification during the behavior of the stage of zinc powder production, the method of laser-induced mass spectrometry was used (the method allows determining the content of at least 60 element impurities). A decrease in the concentration of iron by more than 100 times was established (in the initial zinc the iron content was 1 · 10 ^-3 wt.%, In the obtained powder - below the detection limit - 1 · 10 ^-5 wt.%), A decrease in the concentration of manganese by more than 20 times (in the initial zinc, the manganese content is 2 · 10 ^-4 wt.%, in the obtained powder - below the detection limit - 1 · 10 ^-5 wt.%).

Claims (3)

1. A method of producing zinc oxide powder by oxidizing zinc with oxygen by heating, characterized in that the zinc metal is preliminarily distilled at a temperature below the boiling point in an inert gas stream, the obtained powder is subjected to oxidation in a rotary reactor with a controlled atmosphere at a temperature below the boiling point of zinc. 2. The method according to claim 1, characterized in that the inert gas stream is carried out in a closed loop. 3. The method according to any one of claims 1 and 2, characterized in that a quartz glass reactor is used.