JPS62132731A - Production of rare earth metal oxide - Google Patents

Abstract

PURPOSE:To obtain a rare earth metal oxide easily in a short time in high efficiency, by heating an calcining a rare earth metal hydroxide with microwave. CONSTITUTION:A rare earth metal oxide (e.g. serium oxide) is produced by producing a water-containing rare earth metal hydroxide (e.g. serium hydroxide) obtained from an aqueous solution in the state of precipitate and heating and calcining the hydroxide at >=700 deg.C by irradiating with microwave radiation of 300MHz-300GHz (e.g. microwave of 5kW output and 2,450MHz frequency) for e.g. several tens min.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for easily obtaining rare earth oxide from rare earth hydroxide in a short time.

Rare earth elements have traditionally been used in many industrial fields, such as as modifiers for metals and ceramics, and in the glass industry, but recently they have been rapidly used in cutting-edge technology fields such as electronic materials, magnetic materials, and optical materials. Demand is increasing.

Rare earth elements have very strong activity, so they are used as metals.
＋／、? - Shi is Tasutode 1 → Sha Hotaru Carp 1. Because rice is stable, hydroxide,
It is commonly treated as a variety of intermediate compounds such as oxides, chlorides, and carbonates. Among these, oxides are the most common compounds because they can be obtained with a certain composition and high purity.

(Prior Art) Conventionally, rare earth oxides have been produced by heating and baking rare earth oxalates, carbonates, and hydroxides in an electric heating furnace or a gas heating furnace such as a rotary kiln. Among these, oxalic acid rare earth has a high firing temperature of 900° C. or higher, but highly purified rare earth oxide can be obtained, so it is often used as a raw material for high purity rare earth oxide. On the other hand, when rare earth hydroxide is used as a raw material, it has the disadvantage that impurities easily enter, but because it can be fired at a relatively low temperature, it is advantageously used as a rare earth intermediate compound at various stages of production.

However, no matter which raw material is used, in order to obtain rare earth oxides, electric heating or gas heating is required. Particularly when firing is performed by patch operation, it takes time to raise the temperature and heat in an electric furnace, and gas heating is required. In this case, although the time is somewhat shortened, the operation is laborious and the energy efficiency is poor, so it cannot be said to be an industrially advantageous method.

(Problems to be Solved by the Invention) The present invention relates to a method for easily and efficiently obtaining oxidation deposition in a short time.

The present inventors have made various studies to achieve the above objective, but in particular, when using hydroxide soil as a raw material,
The present invention was achieved by discovering that the raw material absorbs microwaves in both dry and hydrated states, reaches a high temperature in a short period of time, and can be fired easily and efficiently until oxidation deposition occurs.

(Means for Solving the Problems) The gist of the present invention is a method of obtaining rare earth oxides by heating rare earth hydroxides, particularly hydroxides in a water-containing state, to a red-hot state by irradiating them with microwaves.

The frequency of the microwave to irradiate is 300MHz to 30MHz.
Although it can be carried out in the range of 0 GHz, it is advantageous and preferred to use microwaves with a frequency of 2,450 MHz, which is generally allowed for industrial use.

When the raw material hydroxide is irradiated with microwaves, it is heated to 700°C or higher, locally to i,ooo°C or higher.

Although the irradiation time varies somewhat depending on the water content of the raw materials, oxides can be easily obtained if the irradiation time is kept for several tens of minutes.

Since the raw material hydroxide pile is usually obtained in the form of a precipitate from an aqueous solution, it is often treated in a water-containing state, and in this case the method of the present invention can be carried out particularly advantageously.

The rare earths to which the method of the present invention can be applied may be hydroxide piles of individual rare earth elements, or mixtures thereof can be treated in the same manner. In addition, in the smelting process, hydroxides of other metals may be mixed into the hydroxides of rare earth elements, but even in this case, the method of the present invention can be advantageously implemented in the same way as in the above case. It can be treated as an intermediate raw material for the next process.

The present invention can be carried out either batchwise or continuously, but the batchwise method is more advantageous because a simpler heating device can be used. Next, in order to more clearly illustrate the embodiments of the present invention, examples will be given and explained.

(Example 1) Mixed diluted hydroxide ±2.1 kg (1.8 K9 as oxidation deposition) was placed in an alumina container, which was covered with a heat insulating material and set in a microwave heating device. Irradiate microwaves with an output of 5KW and a frequency of 2,450MHz for 50 minutes.
After cooling the obtained oxide, the weight was measured and it was found to be 1,8
K, and oxidation deposition was obtained almost quantitatively.

(Example 2) Mixed hydroxide diluted in a water-containing state in an alumina container ±2,0 K
Example 1
Similarly, output 5Kll/, frequency 4450MHz
Microwave irradiation was performed for 70 minutes, and the resulting oxide was cooled and then weighed to find that the weight was 1.1 kg, indicating that oxidation deposition was almost quantitative.

(Example 3) Hydrated cerium hydroxide 2.1 K in an alumina container
t (Added 1.2 KF as cerium oxide, 5 KW as in Example 1, frequency 2,450 MHz)
-r Microwave was irradiated for 60 minutes. After cooling the obtained oxide, the weight was measured, and the weight was 1.2 K9, and cerium oxide was obtained almost quantitatively.

(Effects of the Invention) The method of the present invention uses microwaves for heating, and can raise the temperature and heat in a shorter time than conventionally used electric heating furnaces, gas heating furnaces, etc., so it is efficient. Rare earth oxides can be obtained in a short time.

In addition, the conventionally used heating device described above has a large volume and requires a large installation area, but the device according to the method of the present invention is small and compact, so it is very easy to implement industrially. Therefore, since oxidation deposition can be provided efficiently and inexpensively, it can greatly contribute to various advances in the use of rare earths.

Claims (2)

[Claims] (1) A method for producing rare earth oxide by heating and firing rare earth hydroxide, the method comprising performing microwave heating. (2) The method according to claim (1), wherein the raw rare earth hydroxide is in a hydrated state.