JP2008260686A - Basic cerium carbonate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide basic cerium carbonate having excellent flow property and to provide a method for producing the same. <P>SOLUTION: The basic cerium carbonate having ≤50° of repose angle and ≤20° of collapse angle is obtained by dissolving a cerium salt which is a starting raw material in water to be 0.05-0.2 mol/L concentration, then by heating the solution at 90-100°C and adding the urea solution for 2-8 hours under agitation while maintaining the temperature, by filtering the precipitate of basic cerium carbonate obtained in above, by washing it with water, and by drying it at 100°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to basic cerium carbonate excellent in fluidity.

Basic cerium carbonate is widely used as a raw material for the production of cerium (III) compounds. Usually, an aqueous ammonium carbonate solution is added to an aqueous cerium (III) salt solution to form a precipitate, which is filtered, washed, Manufactured by drying.
However, the cerium carbonate produced by this method is in the form of a fine powder having a particle size of 1 μm or less or a plate having a large particle size, so that the fluidity is extremely poor and cannot be easily taken out from the storage container.

  Accordingly, the present invention is intended to solve such problems and to provide basic cerium carbonate excellent in fluidity.

In order to solve the above-mentioned problems, the present inventors have produced a basic cerium carbonate having a large particle size and a sharp particle size distribution by the urea method, thereby improving the flowability of the basic cerium carbonate. As a result of finding out that it can be obtained and variously examining its production method, the present invention has been completed.
That is, the present invention is a basic cerium carbonate characterized by an angle of repose of 50 degrees or less and / or a collapse angle of 20 degrees or less.

  According to the present invention, basic cerium carbonate excellent in fluidity can be easily obtained, and its utility value is extremely high in industry.

  In the method for producing basic cerium carbonate of the present invention, first, a cerium (III) salt aqueous solution having a concentration of 0.05 to 0.2 mol / L is prepared. The cerium (III) salt used as a starting material is not particularly limited as long as the solubility is about 0.2 mol / L. And this cerium (III) salt is melt | dissolved in water, and it is set as the density | concentration of 0.05-0.2 mol / L. When this concentration exceeds 0.2 mol / L, the particle size of the basic cerium carbonate obtained becomes small and the fluidity deteriorates. When the amount is less than 0.05 mol / L, the particle size is not particularly affected, but the productivity is lowered.

Next, the aqueous solution is heated to 90 to 100 ° C., and the urea aqueous solution is added for 2 to 8 hours under stirring while maintaining the temperature. Here, when the reaction temperature is lower than 90 ° C., the decomposition rate of urea is slowed, and the yield per reaction time is lowered. Moreover, when it exceeds 100 degreeC, although the decomposition | disassembly rate of urea will improve, since it will be necessary to use a pressure vessel, it becomes disadvantageous in cost.
The amount of urea used is preferably a urea / cerium molar ratio of 10 or more, and if it is less than 10, the yield of basic cerium carbonate decreases.
The concentration of the aqueous urea solution is not particularly limited, but if the concentration is too low, the amount of the aqueous urea solution increases and the productivity is impaired. Therefore, it is preferable to set the concentration to 5 mol / L or more and the saturation concentration or less.
Moreover, when the addition time of the urea aqueous solution is set to less than 2 hours, the particle diameter of the basic cerium carbonate obtained is reduced. On the other hand, if the addition time exceeds 8 hours, the particle size is not affected, but the productivity is lowered, which is not preferable.
The basic cerium carbonate precipitate thus obtained is filtered and washed with water, and then dried at about 100 ° C., so that the repose angle is 50 degrees or less and / or the collapse angle is 20 degrees or less. Excellent basic cerium carbonate is obtained.

  Hereinafter, embodiments of the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1
300 L of 0.1 mol / L cerium nitrate aqueous solution was put into a 500 L reaction kettle and heated to 95 ° C. Separately, 50 L of urea aqueous solution in which 273 kg of urea was dissolved in water was prepared. At this time, the concentration of the urea aqueous solution was 7.8 mol / L, and the urea / cerium molar ratio was 13.
Next, while maintaining the reaction temperature at 95 ° C., an aqueous urea solution was added to the stirring aqueous cerium nitrate solution over 3 hours to form a basic cerium carbonate precipitate (slurry). After completion of the addition of the urea aqueous solution, the mixture was further agitated and aged at 95 ° C. for 2 hours, and then the slurry was cooled, solid-liquid separated with a centrifuge, and the solid part was washed with water. Then, this solid part was dried at 100 ° C. for 16 hours to obtain 67.8 kg of dry powder 1 of basic cerium carbonate (Table 1).
The particle size distribution of the dry powder 1 was measured with a laser diffraction particle size distribution measuring device (Microtrac FRA). Moreover, the angle of repose and the collapse angle of the dry powder 1 were measured with a powder tester (trade name, manufactured by Hosokawa Micron Corporation). These measurement results are shown in Table 1.

(Example 2)
300 L of 0.2 mol / L cerium nitrate aqueous solution was put into a 500 L reaction kettle and heated to 95 ° C. Separately, 100 L of an aqueous urea solution prepared by dissolving 546 kg of urea in water was prepared. At this time, the concentration of the urea aqueous solution was 7.8 mol / L, and the urea / cerium molar ratio was 13.
Next, while maintaining the reaction temperature at 95 ° C., an aqueous urea solution was added to the stirring aqueous cerium nitrate solution over 3 hours to form a basic cerium carbonate precipitate (slurry). After completion of the addition of the urea aqueous solution, the mixture was further agitated and aged at 95 ° C. for 2 hours, and then the slurry was cooled, solid-liquid separated with a centrifuge, and the solid part was washed with water. Then, this solid part was dried at 100 ° C. for 16 hours to obtain 134.0 kg of dry powder 2 (Table 1) of basic cerium carbonate.
The particle size distribution of the dry powder 2 was measured with a laser diffraction particle size distribution measuring device (Microtrac FRA). Moreover, the angle of repose and the collapse angle of the dry powder 2 were measured with a powder tester (same as above). These measurement results are shown in Table 1.

(Comparative Example 1)
300 L of a 0.3 mol / L cerium nitrate aqueous solution was placed in a 500 L reaction kettle and heated to 95 ° C. Separately, 50 L of an aqueous urea solution prepared by dissolving 819 kg of urea in water was prepared. At this time, the concentration of the urea aqueous solution was 7.8 mol / L, and the urea / cerium molar ratio was 13.
Next, while maintaining the reaction temperature at 95 ° C., an aqueous urea solution was added to the stirring aqueous cerium nitrate solution over 3 hours to form a basic cerium carbonate precipitate (slurry). After completion of the addition of the urea aqueous solution, the mixture was further agitated and aged at 95 ° C. for 2 hours, and then the slurry was cooled, solid-liquid separated with a centrifuge, and the solid part was washed with water. Then, this solid part was dried at 100 ° C. for 16 hours to obtain 216.2 kg of dry powder 3 of basic cerium carbonate (Table 1).
The particle size distribution of the dry powder 3 was measured with a laser diffraction particle size distribution measuring device (Microtrac FRA). Moreover, the angle of repose and the collapse angle of the dry powder 3 were measured with a powder tester (same as above). These measurement results are shown in Table 1.

(Comparative Example 2)
A basic cerium carbonate dry powder 4 (Table 1) was obtained under the same conditions as in Example 1 except that the urea aqueous solution was added to the cerium nitrate aqueous solution over 1 hour.
The particle size distribution of the dry powder 4 was measured with a laser diffraction particle size distribution measuring device (Microtrac FRA). Moreover, the angle of repose and the collapse angle of the dry powder 4 were measured with a powder tester (same as above). These measurement results are shown in Table 1.

(Evaluation)
As can be seen from Table 1, according to the method of the present invention, basic cerium carbonate excellent in fluidity having an angle of repose of 50 ° or less and a collapse angle of 20 ° or less was obtained.

Claims (3)

Basic cerium carbonate characterized by an angle of repose of 50 degrees or less. A basic cerium carbonate having a decay angle of 20 degrees or less. A basic cerium carbonate having an angle of repose of 50 degrees or less and a collapse angle of 20 degrees or less.