JP2823070B2 - Method for producing high-purity zirconium oxychloride crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for producing high-purity zirconium oxychloride crystals, and more particularly to a process for producing calcium zirconate (CaZrO ₃ ) by an exothermic reaction between zircon ore and calcium carbonate; Is dissolved in hydrochloric acid, sulfuric acid and an alkali solution are sequentially added thereto to precipitate basic zirconium sulfate; a step of converting the precipitated basic zirconium sulfate to zirconium hydroxide using ammonia; Dissolving in hydrochloric acid to produce an aqueous solution of zirconium oxychloride; evaporating the aqueous solution of zirconium oxychloride and adding concentrated hydrochloric acid thereto; and cooling the solution to room temperature to crystallize only once. high purity zirconium oxychloride that is improved by the crystallization step (ZrOCl ₂ · 8H ₂ O) A method of manufacturing a crystal.

[0002]

2. Description of the Related Art Zirconium oxychloride is widely used as a raw material for mordants and coating agents, and high-purity zirconium oxychloride is used particularly as an essential component of zirconia ceramics. The industrial process for the production of zirconium oxychloride from zircon consists of two crystallizations. In the first crystallization, zircon is decomposed at high temperature using an alkaline decomposing agent containing sodium ions such as sodium hydroxide or sodium carbonate, and by-products such as sodium silicate and sodium oxide generated during the reaction are formed. Removed by washing with water, sodium zirconate (Na ₂ ZrO ₃ )
Dissolving the sodium zirconate in a large amount of hydrochloric acid, removing undissolved components such as silica (SiO ₂ ) and unreacted ore (zircon) by filtration, and removing the solution of zirconium oxychloride and sodium chloride. Making; then evaporating the solution, cooling and filtering to isolate the zirconium oxychloride crystals. However, the zirconium oxychloride crystal produced in the first crystallization step contains impurities such as silica or sodium chloride. Thus, to obtain pure zirconium oxychloride crystals, dissolving the crystals obtained from the first crystallization step in water; adding hydrochloric acid to the solution; heating and concentrating it; A second crystallization must be performed, including cooling and isolating the crystals. However, since the zirconium oxychloride crystal produced by the above-mentioned conventional method still contains a large amount of impurities such as sodium chloride, multi-stage crystallization is employed to reduce the amount of impurities. Therefore, the yield of zirconium oxychloride crystals is very low. Therefore, according to the conventional method, not only zirconium oxychloride but also sodium chloride having low solubility in hydrochloric acid coexists in the sodium zirconate solution,
As a result, high purity zirconium oxychloride crystals cannot be obtained depending on the crystallization method for separating zirconium oxychloride in concentrated hydrochloric acid. Therefore, in order to reduce the content of sodium chloride in the crystals, dissolve the zirconium oxychloride crystals obtained from the first crystallization in water and add hydrochloric acid,
The solution is evaporated, cooled and recrystallized to produce zirconium oxychloride crystals in two crystallization steps. As a result, the yield of zirconium oxychloride by multi-stage crystallization is less than 70%, and the zirconium oxychloride crystals contain 0.7 to 2% sodium chloride as an impurity. Furthermore, this method has disadvantages associated with the large consumption of hydrochloric acid and the large energy supply.

In order to solve the problem relating to impurities in zirconium oxychloride crystals, Japanese Patent Application Laid-Open No. 61-215,217 discloses
A step of producing sodium zirconate by an exothermic decomposition reaction between zircon and sodium hydroxide and a silica removal treatment; dissolving the sodium zirconate in hydrochloric acid;
Producing a solution of sodium chloride and zirconium oxychloride; adding pyridine or ammonia water to precipitate only the zirconium component; dissolving the zirconium precipitate in a large amount of hydrochloric acid while heating, and then cooling Discloses a method for producing zirconium oxychloride crystals. Although this method does not have a recrystallization step, it is very complicated and has problems such as a high content of impurities in the product and a low yield of the product.
In addition, this method uses a large amount of hydrochloric acid and is not economically feasible. Further, JP-A-63-21222 discloses a process for producing sodium zirconate by an exothermic decomposition reaction of zircon and sodium hydroxide and a silica removing treatment; the sodium zirconate is prepared in an equivalent amount to sodium in sodium hydroxide. Dissolving in hydrochloric acid, removing the generated sodium chloride, and converting the zirconium component to zirconium hydroxide; including dissolving the zirconium hydroxide in concentrated hydrochloric acid to produce a solution of zirconium oxychloride, and cooling. A method for producing zirconium oxychloride crystals is disclosed. However, this method also has a high impurity level in the generated zirconium oxychloride crystal and a low yield of the zirconium oxychloride crystal. In this regard, the inventor of the present application has studied a further improved method for producing high-purity zirconium oxychloride crystals, and obtained needle-like crystals of high-purity zirconium oxychloride in high yield in only one crystallization step. Having completed the invention, which can be manufactured, this is made possible by two facts. One is to convert zircon into calcium zirconate instead of sodium zirconate and form calcium chloride that is relatively more soluble in hydrochloric acid than sodium chloride, thereby avoiding contamination of the zirconium oxychloride crystals. That is what you can do. Another is that the method comprises the steps of precipitating basic zirconium sulfate and converting it to zirconium hydroxide.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an intermediate such as calcium zirconate, basic zirconium sulfate precipitation and zirconium hydroxide, which allows high purity oxychloride in a single crystallization step. An object of the present invention is to provide a method for producing a zirconium crystal.

[0005]

The present invention comprises: (a) a step of extracting calcium zirconate (CaZrO ₃ ) formed by an exothermic decomposition reaction between calcium carbonate and zircon powder with dilute hydrochloric acid; (b) sulfuric acid and alkali Filtering the basic zirconium sulfate precipitate formed by adding the solution to the calcium zirconate hydrochloric acid solution; (c) dispersing the basic zirconium sulfate in water and adding ammonia to produce the zirconium hydroxide precipitate. And (d) evaporating an aqueous solution of zirconium oxychloride prepared by dissolving the zirconium hydroxide in hydrochloric acid, adding concentrated hydrochloric acid, cooling to room temperature, and filtering to form an oxychloride formed by a series of steps. Characterized by the step of recovering zirconium crystals,
The present invention relates to a method for producing zirconium oxychloride crystals using zircon (ZrSiO ₄ ) as a raw material.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high purity zirconium oxychloride crystals by only one crystallization. This will be described in detail below. Zirconia zircon containing (ZrO ₂₎ and silica (SiO _2), the molar ratio of 2 or more, preferably mixed with calcium carbonate in a molar ratio 2-3, the mixture about 1250 ° C., was preferably reacted at 1350 to 1450 ° C. hand,
Produces zircon and converts it to several zircon degradation products such as calcium zirconate and calcium silicate.
When the amount of calcium carbonate used is less than 2 in a molar ratio of 1 mole of zircon, no calcium zirconate is formed. Therefore, when the zircon hydrolyzate is extracted with dilute hydrochloric acid, calcium silicate is dissolved and removed by filtration, and only calcium zirconate can be produced. After dissolving calcium zirconate powdered by drying in concentrated hydrochloric acid, a precipitant such as sulfuric acid is added,
While heating to 90 ° C, ammonia, sodium hydroxide,
One or more alkaline solutions selected from the group consisting of potassium hydroxide and organic amines are added to the solution and its pH is adjusted.
Is controlled between 1.4 and 2.0 and then any zirconium present in the solution is precipitated as basic zirconium sulfate. The amount of sulfuric acid used as precipitant is preferably a molar ratio of 2 to 5 mol of zirconium. If the amount is less than 2 mol, the yield of basic zirconium sulfate will be low,
When the amount exceeds 2 mol, the p
H is reduced, resulting in a reduced yield of basic zirconium sulfate. PH of the solution to which the alkaline solution was added was 1.4
If it is less than 2, the zirconium compound present in the solution cannot completely precipitate and remains as an ion in the solution, while if it exceeds 2.0, all the zirconium compounds will precipitate. , Along with silica,
Compounds such as titanium and iron precipitate and coexist in the basic zirconium sulfate precipitate. After filtering the basic zirconium sulfate precipitate, it is suspended in water to prepare a dispersion. When the pH of this solution is adjusted to 8 to 10 by adding ammonia water or ammonia gas, the basic zirconium sulfate precipitate is converted into zirconium hydroxide [ZrO (OH) ₂ .xH ₂ O] precipitate. At this time, if the pH of the liquid is less than 8,
Basic zirconium sulfate cannot be completely converted, and the solubility of zirconium hydroxide deteriorates due to residual sulfate groups in the precipitate. Also, exceeding 10 is not desirable from the viewpoint of excessive use of ammonia. The zirconium hydroxide precipitate is filtered and dissolved in concentrated hydrochloric acid equivalent to zirconium to prepare a zirconium oxychloride solution free of calcium compounds. Then, the obtained solution is evaporated at 90 ° C. or higher, and hydrochloric acid is added until the concentrations of zirconium ions and hydrochloric acid in the solution are adjusted to 85 to 150 g / l and 150 to 300 g / l, respectively. I do. Upon cooling to room temperature, crystallization occurs and the crystals separate from the solution. This is centrifugally filtered to recover high-purity zirconium oxychloride crystals. However, in the process of concentrating the aqueous solution of zirconium oxychloride and adding hydrochloric acid, if the concentrations of zirconium ions and hydrochloric acid are lower than the above ranges, the yield of crystals is extremely reduced. In addition, the higher the concentration, the higher the yield, but the point of energy consumption for evaporating a larger amount of the solution and the fact that crystallization occurs even at a high temperature simultaneously with the addition of hydrochloric acid cause more impurities in the crystal. Is undesirable from the viewpoint of containing.

As described above, the method for producing a high-purity zirconium oxychloride crystal of the present invention comprises the steps of (a) using calcium carbonate as a decomposing agent instead of sodium hydroxide or sodium carbonate to completely decompose the product; By the preparation, impurities such as sodium compound (sodium chloride) which can easily coexist in the oxychloride crystal by mixing are eliminated from the beginning; (b) precipitation of basic zirconium sulfate;
Most of the calcium-containing impurities are separated and removed by an intermediate production step consisting of converting this to zirconium hydroxide; and (c) a high-purity zirconium oxychloride crystal is obtained by a single crystallization step. Can be produced in a high yield. The present invention will be described with reference to the following examples, but the present invention is not limited to the following examples.

[0008]

EXAMPLES Example 1 Zircon (ZrSiO ₄ ) powder was mixed with calcium carbonate at a molar ratio of 1:
3 and formed into spherical pellets having a diameter of about 1 cm.
The decomposition reaction was performed for minutes. The particles were pulverized and extracted with a 3.5% hydrochloric acid solution to remove calcium silicate to prepare a calcium zirconate powder. The calcium zirconate (200 g) powder was dissolved in a 25% hydrochloric acid solution (600 ml), diluted with distilled water, and undissolved components were removed by filtration. Maintain the temperature at 90 ° C. for 1 hour, adjust the pH to 1.4 with aqueous ammonia and add 95%
Of sulfuric acid (46 g) was added to precipitate all zirconium ions as basic zirconium sulfate. The precipitate thus prepared was filtered and dispersed in distilled water (1 liter). The pH of the dispersed precipitate slurry was adjusted to 8.5 by adding 25% aqueous ammonia to convert the basic zirconium sulfate precipitate to a zirconium hydroxide precipitate. The zirconium hydroxide precipitate was filtered, washed with water, dissolved in 25% hydrochloric acid (300 ml) to prepare an aqueous zirconium oxychloride solution, and concentrated by heating until the volume reached 450 ml. Then, 35% hydrochloric acid (500
(Milliliter) so that the zirconium ion concentration becomes 115 g / l and the hydrochloric acid concentration becomes 225 g / l. The solution was cooled to room temperature, filtered by centrifugation, and crystallized with zirconium oxychloride (320 g, yield 89%).
%) Was recovered. Example 2 An acidic solution (200 g) of calcium zirconate was prepared in the same manner as in Example 1 described above, and the pH of the solution was adjusted using a 5 M potassium hydroxide solution in a precipitation step of basic zirconium sulfate. A zirconium oxychloride crystal (315 g) was recovered in the same manner as in Example 1 except that the pH was adjusted to 2.0. Example 3 An acidic solution (200 g) of calcium zirconate was prepared in the same manner as in Example 1 above, and the pH was adjusted to 1 using a 5M potassium hydroxide solution in a precipitation step of basic zirconium sulfate. And the concentration of zirconium ion was adjusted to 95 g / l and the concentration of hydrochloric acid was adjusted to 255 g / l. Subsequent steps were performed in the same manner as in Example 1 above. As a result, zirconium oxychloride crystals (290 g) were recovered. Example 4 An acidic solution (200 g) of calcium zirconate was prepared in the same manner as in Example 1 above, and the pH was adjusted to 2 using a 5M potassium hydroxide solution in a precipitation step of basic zirconium sulfate. The pH was adjusted to be 2.0, so that the zirconium ion concentration was 135 g / l and the hydrochloric acid concentration was 195 g / l. Subsequent steps were performed in the same manner as in Example 1 above. As a result, zirconium oxychloride crystals (300 g) were recovered.

Comparative Example 1 (by the method of Comparative Example 1 in JP-A-61-215,217) A mixture of zircon and sodium hydroxide (molar ratio 1:
After the decomposition reaction of 4), sodium silicate (Na) extracted with distilled water
SiO ₃ ) was removed by filtration. The remaining sodium zirconate powder (100 g) was dissolved in 35% hydrochloric acid (200 ml), and the undissolved components were removed by filtration to prepare a solution of zirconium oxychloride and sodium chloride. The solution thus prepared was concentrated and cooled to room temperature to form zirconium oxychloride crystals. After dissolving the isolated crystals in water (200 milliliters), 35% hydrochloric acid was added at room temperature until a precipitate formed in the solution. After completely dissolving the precipitate while heating,
Cool to room temperature until crystals form. The crystals were centrifugally filtered to recover zirconium oxychloride crystals (116.7 g, yield 67%). Comparative Example 2 (according to the method of Comparative Example 2 in JP-A-61-215,217) Sodium zirconate (100 g) with baddelite (ZrO ₂ , 96%) was dissolved in hydrochloric acid (200 ml) and filtered. Undissolved components were removed to prepare a solution of zirconium oxychloride and sodium chloride. The solution thus prepared was treated in the same manner as in Comparative Example 1, and then zirconium oxychloride crystals (111.5 g, yield 64%) were recovered. Experimental Example Impurities in zirconium oxychloride crystals prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were analyzed by an ICP method. The results are shown in Table 1 below.

[0010]

[Table 1] Table 1 Category ZrO ₂ impurity content Content Si Ti Fe Al Ca Na Example 1 37.4 0.0025 0.0015 0.0001 0.0004 0.0006 0.0005 Example 2 37.3 0.0040 0.0030 0.0015 0.0010 0.0012 0.0010 Example 3 37.2 0.0015 0.0022 0.0002 0.0006 0.0006 0.0012 Example 4 37.6 0.0034 0.0029 0.0016 0.0009 0.0011 0.0006 Comparative Example 1 37.5 0.0550 0.0135 0.0044 0.0078 0.0012 0.75 Comparative Example 2 37.2 0.009 0.008 0.004 0.002 0.001 0.36

As shown in Table 1, the product produced by the simple method of the present invention has an impurity concentration of 5 to 10 times (1000 times in the case of Na) as compared with the product produced by the conventional method. ) Indicates the purity.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Ishii Nihon Hanwool Apartment 106-903 (56, Reference) Shinseong-dong, Yuseong-gu, Daejeon, Republic of Korea (56) References JP-A-4-92819 (JP, A) JP-A-2-279503 (JP, A) JP-A-2-279504 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C01G 25/00

Claims (6)

(57) [Claims] 1. A zircon (ZrSiO ₄₎ from zirconium oxychloride (ZrOCl ₂ · 8H ₂ O) a method for producing a crystalline, zirconium acid formed by exothermic decomposition reaction with (a) calcium carbonate and zircon powder (B) extracting calcium (CaZrO ₃ ) with dilute hydrochloric acid; (b) filtering a basic zirconium sulfate precipitate formed by adding sulfuric acid and an alkaline solution to the calcium zirconate solution; (c) filtering the basic zirconium sulfate. Dispersing in water and filtering the zirconium hydroxide precipitate produced by adding ammonia; and (d) evaporating an aqueous solution of zirconium oxychloride produced by dissolving the zirconium hydroxide in hydrochloric acid, adding concentrated hydrochloric acid. Recovering the zirconium oxychloride crystals formed by the steps of cooling to room temperature and filtering. 2. In the step (a), calcium carbonate is used in a molar ratio of 2 to 3 with respect to 1 mol of zircon,
A method for producing a zirconium oxychloride crystal according to claim 1. 3. The method for producing a zirconium oxychloride crystal according to claim 1, wherein in the step (b), sulfuric acid is used in a molar ratio of 2 to zirconium ions in a 5 mol solution. 4. In the step (b), one or more compounds selected from the group consisting of ammonia, sodium hydroxide and potassium hydroxide are added to adjust the pH of the alkaline solution to 1.4 to 2.0. The method for producing a zirconium oxychloride crystal according to claim 1, wherein 5. The method for producing a zirconium oxychloride crystal according to claim 1, wherein in step (c), the pH of the solution is controlled to 8 to 10 by adding ammonia. 6. In the step (d), the concentrations of zirconium ion and hydrochloric acid in the aqueous solution of zirconium oxychloride mixed with concentrated hydrochloric acid are adjusted to 85 to 150 g / liter, respectively.
The method for producing zirconium oxychloride crystals according to claim 1, wherein the amount is adjusted to a range of 150 to 300 g / liter.