JPH02279503A - Production of zirconium oxychloride - Google Patents

Abstract

PURPOSE:To obtain high-purity zirconium oxychloride at a low cost by the ordinary industrial process by treating the product obtained by melting zircon sand and a CaO-contg. raw material with hydrochloric acid in three stages. CONSTITUTION:A mixture contg. zircon sand and a CaO-contg. raw material in >=2.5, or preferably 2.8 to 4, molar ratio of CaO/ZrO2 is heated at 1500 to 2600 deg.C and melted, and then the molten product is quenched by water granulation, etc. The acid-soluble molten product thus obtained is pulverized to the powder having <=150mu grain size, the powder is brought into contact with dil. hydrochloric acid to selectively elute and separate the calcium silicate component, and the concentrated CaZrO3 component as the elution residue is recovered. The residue is catalytically dissolved with concd. hydrochloric acid to recover the Zr decoction. In this case, the residue is advantageously eluted with the hydrochloric acid having <2mol/l acid concn. in the slurry and then eluted with the hydrochloric acid having >=2mol/l concn.. Hydrochloric acid is then added to the Zr decoction to deposit zirconium oxychloride crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing high-purity zirconium oxychloride, which is used as a starting material for producing zirconium compounds.

[Prior art] Zirconia can be used as a sintered raw material for ferroelectric materials, piezoelectric materials, catalyst carriers, solid electrolytes, heat insulating materials, heat resistant materials, wear resistant materials, abrasive materials, etc.
It is also used in a wide range of fields such as optical glass additives, thermal spray materials, and pigments. The zirconia fine powders used for these purposes include those consisting of zirconia as a single component and those consisting of multiple components containing stabilizers such as magnesia, calcia, and ittria.

On the other hand, in recent years, research and development related to fine ceramics has become active, and the excellent physical properties of zirconia ceramics have attracted attention, and their use as high-performance electronic ceramic materials, high strength, high toughness ceramic materials, etc. is expanding. Demand for high-quality zirconia fine powder, which is the raw material for these products, is increasing.

The general method for producing zirconia is to use zirconium salts such as zirconium oxychloride and zirconium sulfate as the starting material, and convert an aqueous solution of these salts into zirconium hydroxide or hydrate through a neutralization reaction or hydrolysis reaction. A method is adopted in which a precipitate of a substance is generated, which is then dehydrated, dried, and calcined. A specific method is to add an alkali such as aqueous ammonia to an aqueous solution of zirconium oxychloride, neutralize it to produce hydroxide, filter it, wash it, dry it, and then sinter it. ing.

However, in this method, Fe, A/, T, which is present as an impurity in zirconium oxychloride when neutralized with alkali to form a precipitate of zirconium hydroxide.
Since zirconium i, Si, etc. are mixed as hydroxides along with the zirconium precipitation, purified raw materials must be used, and zirconium oxychloride from which impurities have been removed by recrystallization is usually used as the starting material. are doing.

Zirconium oxychloride is not only a raw material for manufacturing zirconia powder for fine ceramics, but also an important raw material for manufacturing zirconium compounds for optical glasses, oxygen sensors, piezoelectric elements, chemicals, etc.
Higher purity is required.

Usually, zirconium oxychloride is produced by melting zircon sand in an alkali together with caustic soda, then decomposing sodium zirconate by dissolving and separating sodium silicate from this melt with hydrochloric acid, and then concentrating the solution after removing insoluble matter in layers. It is manufactured by precipitating crystals of zirconium oxychloride.

Other known methods for producing zirconium oxychloride include hydrolyzing zirconium tetrachloride with water and dissolving zirconium carbonate in hydrochloric acid.

[Problems to be Solved by the Invention] In the above manufacturing method, zirconium oxychloride obtained by the caustic soda dissolution method usually contains a large amount of impurities, and unless the impurities are removed by repeated recrystallization, it cannot be used for fine ceramics or It cannot be used as a raw material for producing other high-purity zirconia compounds, and a large amount of cost is required to obtain high-purity zirconia oxychloride.

On the other hand, although the present applicant has developed a method for producing calcium zirconate (Japanese Unexamined Patent Publication No. 83-64917), this publication does not describe a method for producing high-purity zirconium oxychloride.

The present invention overcomes the drawbacks of the prior art as described above, and enables industrially advantageous production of zirconium oxychloride with low impurity content as a raw material for producing fine ceramics and various other zirconium compounds through normal industrial operations. In particular, it is characterized by providing a method for preparing Si, T in zirconium oxychloride, which has been difficult with conventional techniques.
i, A1. The content of impurities such as Fe is 100 p each.
It is an object of the present invention to provide a method for producing high-purity zirconium oxychloride in which the purity is reduced to p+s or less.

[Means and effects for solving the problem] The present inventors
As a result of extensive research to resolve the shortcomings of conventional methods, the zirconium-containing product obtained by mixing zircon sand with a calcium source such as lime and quenching it by electrolysis was subjected to a three-stage hydrochloric acid treatment to produce high-purity oxidized zirconium. They discovered that zirconium chloride can be obtained and completed the present invention.

That is, the present invention comprises b) a melt generation step of heating and melting a raw material mixture of zircon sand and a CaO-containing raw material and then rapidly cooling it to obtain an acid-soluble melted product; a step of concentrating the zirconium component in which the calcium silicate component is selectively eluted and separated by contacting with an aqueous hydrochloric acid solution; (c) a leaching step of contacting and dissolving the zirconium component with concentrated hydrochloric acid to recover a zirconium leachate; and (d) a step of recovering the zirconium leachate. This method of producing zirconium oxychloride is characterized by comprising a crystallization separation step of adding hydrochloric acid to a zirconium leachate to precipitate zirconium oxychloride crystals, and separating and recovering the obtained crystals.

The present invention will be explained in detail below.

In the method for producing zirconium oxychloride according to the present invention, first, in the melt generation step, a raw material mixture of zircon sand as a starting material and a CaO-containing raw material is heated and melted, and then rapidly cooled to obtain an acid-soluble molten product. .

As the raw material zircon sand used in the present invention, a commercially available product can be used as it is, but a pulverization operation may be added if necessary.

In addition, quicklime, slaked lime, various types of calcium carbonate, etc. can be used as CaO-containing raw materials, and if necessary, coarsely crushed or
Alternatively, it can be used after being granulated.

In the present invention, the mixing ratio of zircon sand and CaO-containing raw material is important and must be determined taking into consideration the composition of the acid-soluble melted product.
The raw materials are mixed so that the molar ratio of O becomes a constant value, and then melted and rapidly cooled. The reaction within the molten product in this case is thought to basically follow the reaction shown in formula (1) below.

ZrSiO4+3CaO→CaZr0z+2CaO・5
iOz...(f) As shown in the above formula (1), the ratio of zircon sand and quicklime is 3 moles of CaO to 1 mole of Zr0□, but in the actual reaction, it is contained in the raw materials. Due to impurities and some non-uniformity in the raw material mixture, 2.5% of CaO is added to 1 mole of Zr0□.
It is desirable that the amount is mol or more, preferably 2.8 to 4 mol.

Next, the raw material mixture is heated and melted at 1500 to 2600°C, preferably 1700 to 2400°C, and then the molten product is rapidly cooled by water crushing or the like. This operation usually uses an arc furnace equipped with a tap, through which the molten product flows out and is quenched by water pulverization by being blown with a high-pressure water stream. By quenching by water pulverization, the zirconia component in the molten product can be rendered acid-soluble, and quenched amorphous or acid-soluble calcium zirconate (CaZrfL) can be obtained.

According to the research conducted by the present inventors, zircon sand and quicklime were used to melt a mixture of 2.5 mol or more, for example 3 mol, of CaO per 21 mol of Zr0, and the molten product was pulverized and rapidly cooled. In the case, X-ray diffraction analysis shows CgZrO, (J
Only the X-ray diffraction peak of CPDS card 35-790.1985) appears, and 2CaO.SiO□ is amorphous. On the other hand, when the molten product is gradually cooled, in addition to the X-ray diffraction peak of CaZrO3, 0.85Z
r02-0.1'l; Ca0 (JCPDS card 28
-341.1976) or Z r Oz (JCP
DS Card 17-923.1967) Similar X-ray diffraction peaks appear.

On the other hand, when less than 25 mol of CaO is mixed and melted with respect to 21 mol of Zr0, and the molten product is pulverized and rapidly cooled, in addition to CaZr0z, 0.85ZrOz ・0.15C
A peak similar to aO1 or Z r O2 appears.

Furthermore, when mol of CaO2 is mixed with 1 mol of ZrO2 and melted, the X-ray diffraction peak of CaZrL no longer appears in the quenched product of the molten product, and the peak of 0.852r
02.0.15CaO or Z r O2-like peaks only.

Here, 0.85ZrOz ・O, 15CaO and ZrO,
shows almost similar X-ray diffraction patterns, and it is estimated that the product is actually produced when 0 to 0.15 mol of CaO is dissolved in solid solution with respect to Z r O2.

Furthermore, the present inventors investigated the solubility (elution) of the zirconia component in hydrochloric acid for various molten products. As a result, X-ray diffraction analysis revealed that CaZr0. It was found that almost 100% of the zirconia component was eluted in the molten product in which only 2 mol/l of hydrochloric acid was present. For this, X&! The melted product in which 0.85Zr02・0.15CaO or ZrO was observed in addition to 1L of CaZr by diffraction analysis was 0.85ZrO□・0.15C.
It has been found that as the peak strength of aO or ZrO increases, the elution rate of the zirconia component decreases. And there is no diffraction peak of CaZrO3 in the melted product (,
0.85Zr02・0.15CaO or ZrO2
In the case of only the diffraction peak of , the elution rate of the zirconium component was 50% or less even when dissolved in 2 to 11 mol/l of hydrochloric acid.

Based on the above knowledge, in order to melt a mixture of zircon sand and CaO-containing raw materials and make the zirconia component in the melted product acid-soluble, it is necessary to make the melted product acid-soluble by X-ray diffraction analysis. It is important to create a composition in which only the phase can be obtained, and for that purpose, CaO is added and mixed in an amount of 2.5 mol or more relative to ZrO□, and the molten product is rapidly cooled to obtain 0.85 ZrL.・0.15Ca
It is necessary to prevent the formation of O or Z r O2.

The acid-soluble molten product thus obtained is desirably pulverized into a powder having a particle size of 150 microns or less, preferably 100 microns or less.

If the particle size exceeds 150 μm, colloids of SiOz will aggregate on the particle surface during the next step of elution treatment with dilute hydrochloric acid, resulting in poor elution rate and separation performance.

Next, in the step of concentrating the zirconium component, the calcium zirconate component and the calcium silicate component are selectively eluted and separated from the acid-soluble molten product slurry produced by contacting the acid-soluble molten product with a dilute aqueous hydrochloric acid solution. HC in slurry of acid-soluble molten product dispersed in dilute aqueous hydrochloric acid solution
By performing elution under conditions where the I concentration is less than 2 mol/l, as much calcium and silica as possible in the acid-soluble molten product can be eluted. The reaction formula is as shown in the following formula (ff).

CaZr0j+2CaO・5iOz+4tlCI! −
CaZrO3+ ZCaCtz +5iOz+ 282
0 ... (II) Specifically, an amount of 1.0 to 1.2 times the equivalent of HCl in the reaction formula shown in the above formula (n) is used, and diluted with water to give 2 mol/ Elution is carried out using a hydrochloric acid aqueous solution having a concentration of less than 1 liter, and the calcium zirconate component of the elution residue is separated and recovered.

Next, in a zirconium leaching step, the calcium zirconate obtained in the leaching step is dissolved in contact with concentrated hydrochloric acid to recover a zirconium leaching solution. Calcium zirconate is immersed in concentrated hydrochloric acid solution to remove HC in the slurry.
Leaching is performed under conditions where the I concentration is 2 mol/l or more, and the zirconium content is leached out.

Specifically, the following formula (III) CaZrO3+4HCl was added to the calcium zirconate component of the elution residue in the step.
= Zr0C1z + 2H, o+CtC12...(
1.0 to 1.2 of the equivalent of HCl in the reaction formula shown in 1)
Using twice the amount, leaching is carried out at a hydrochloric acid concentration of 2 mol/l or more.

Moreover, in any of the above-mentioned concentration steps and leaching steps, there is no particular limitation on the degree of slurry in the eluate or leachate, as long as it satisfies a predetermined hydrochloric acid concentration.

Although there is no particular limitation regarding the elution or leaching in this case, it seems that the elution or leaching rate is faster when heated to -a, and 50 to 100°C is preferable.

In addition, when leaching the acid-soluble molten product with hydrochloric acid,
It is also possible to perform leaching in one step with 2 mol/l or more of hydrochloric acid, but in this case, calcium and silica are also leached together with zirconium into the leaching solution, and the silica that has been dissolved in the leaching solution is hydrated. Decomposition leads to insoluble silica precipitates, making subsequent solid-liquid separation extremely difficult.

Therefore, when leaching an acid-soluble molten product with hydrochloric acid,
As in the present invention, leaching is carried out in advance with less than 2 mol/l of hydrochloric acid to elute as much calcium and silica as possible in the molten product, and then the leaching residue is dissolved in 2 mol/l or more of hydrochloric acid to remove zirconium. The two-step leaching method is industrially advantageous and is one of the features of the present invention.

Therefore, such a two-step leaching is necessary to remove most impurities from the zirconium oxychloride eluate.

Next, the crystallization separation step is a step in which hydrochloric acid is added to the zirconium oxychloride leachate thus obtained to precipitate and separate crystals of zirconium oxychloride (ZrOCb.81i, O).

Various embodiments of the crystallization method as described above can be considered, but the method of the present invention is not particularly limited.According to the literature, the solubility of zirconium oxychloride in hydrochloric acid is as shown in the figure. According to Figure 6, the solubility of zirconium oxychloride is at a hydrochloric acid concentration of 8 to 9.
It can be seen that a curve with a minimum value is drawn at mol/l. Therefore, according to this solubility curve, in order to maximize the recovery rate of zirconium, it is advantageous to precipitate crystals of zirconium oxychloride at a hydrochloric acid concentration of 8 to 9 mol/l. The zirconium concentration is 10y/l or less as ZrO2.

On the other hand, according to the results of measurements conducted by the present inventors, it was found that when calcium chloride coexists with zirconium oxychloride, the hydrochloric acid concentration at which the solubility of zirconium oxychloride becomes minimum shifts to the lower concentration side. It was also found that as the calcium chloride concentration increases, the hydrochloric acid concentration at which the solubility of zirconium oxychloride becomes minimum becomes lower. In this way, when attempting to efficiently recover zirconium by adding hydrochloric acid to a zirconium oxychloride solution to precipitate zirconium oxychloride crystals, in a system where calcium chloride coexists in the zirconium oxychloride solution, the zirconium oxychloride Since the hydrochloric acid concentration at which the solubility is minimal shifts to the lower concentration side, the amount of hydrochloric acid added can be reduced, and furthermore, the liquid from which the crystals have been separated is small in volume and has a low acid concentration, making it easy to dispose of the waste liquid. There are advantages such as:

Since the zirconium leachate according to the method of the present invention is obtained by eluting a zirconia concentrate mainly composed of calcium zirconate with hydrochloric acid, it inevitably contains calcium chloride. In precipitating crystals and efficiently recovering zirconium, the amount of hydrochloric acid used can be reduced as described above, and the method of the present invention can be said to be an excellent method for producing zirconium oxychloride.

[Examples] The present invention will be specifically described below with reference to Examples, but the method of the present invention is not limited thereto.

Implementation PAI Z r So that the molar ratio of Oz and CaO is 1:3,
After weighing the zircon sand and quicklime and mixing them uniformly,
Melted in an electric furnace. The heating melting temperature of the molten material at this time is 2
First, the temperature was 300° C., and then the melt was quenched with a water stream, dried and ground to obtain a molten product. As a result of analyzing this melted product, Zr0z34.8%, Ca047.7%,
It has a composition of 5iOz16.9%, and the particle size is 15
It was less than 0 μ ring. In addition, in X-ray diffraction analysis, CaZr
Only the Os diffraction peak was identified.

Next, water 7.51.35% hydrochloric acid 7502 was added to a glass beaker 101, and the molten product was crushed while stirring.
0 g was added and heated and held at 25°C for 2 hours. Next, this slurry was separated from P, and the obtained leaching residue was diluted with water for 2 hours.
The mixture was washed into a beaker, and 1,450 g of 35% salt W was added to bring the total volume to 11. The mixture was heated with stirring and maintained at 90° C. for 2 hours.

Next, this slurry was separated and the filter cake was washed to obtain a zirconium-containing leachate i1Z.6 The leachate contained Fe.
, A1. Contains impurities such as Ti and Si, and the constant J1
As a result, At', 0,
0.60%, Fe2O, 0.07%, 51020.33
%, T i O20, 34%.

Next, 5 soy of 35% hydrochloric acid was added to this leachate 11 to precipitate crystals of zirconium oxychloride. The crystals were separated by filtration to obtain 400 g of zirconium oxychloride. When this crystal was analyzed, the impurity content was found to be SiO
2: 70ppm, TiOz80ppm, A120x:
90 ppm, Fe2O: +: ] Oppm,
It turned out to be highly pure zirconium oxychloride.

[Effects of the Invention] As explained above, the method for producing zirconium oxychloride of the present invention enables industrially and inexpensively producing high-purity zirconium oxychloride from zircon sand, which is a raw material containing impurities, through normal industrial operations. There are excellent effects that can be provided.

The highly purified zirconium oxychloride produced by the method of the present invention can be used for various purposes including as a raw material for producing zirconia, and is extremely advantageous.

[Brief explanation of drawings]

The figure is a graph showing the solubility of zirconium oxychloride in hydrochloric acid.6 Patent applicant: Nihon Kagaku Kogyo Co., Ltd.

Claims (1)

[Claims] 1. (a) A melt generation step of heating and melting a raw material mixture of zircon sand and a CaO-containing raw material and then rapidly cooling it to obtain an acid-soluble melted product; (b) the acid-soluble melted product. (c) a leaching step of contacting and dissolving the zirconium component with concentrated hydrochloric acid and recovering a zirconium leachate; (d) ) A method for producing zirconium oxychloride, comprising a crystallization separation step of adding hydrochloric acid to the zirconium leachate to precipitate zirconium oxychloride crystals, and separating and recovering the obtained crystals. 2. The method for producing zirconium oxychloride according to claim 1, wherein the raw material mixture is a mixture in which the molar ratio CaO/ZrO_2 is in a range of 2.5 or more. 3. The acid-soluble melt product is amorphous or Ca
Claim 1 in which only ZrO_3 crystal phase is recognized.
The method for producing zirconium oxychloride as described. 4. The method for producing zirconium oxychloride according to claim 1 or 3, wherein the acid-soluble molten product is a powder with a particle size of 150 μm or less. 5. The method for producing zirconium oxychloride according to claim 1, wherein the step of concentrating the zirconium component is carried out at a HCl concentration of less than 2 mol/l in the slurry. 6. The method for producing zirconium oxychloride according to claim 1, wherein the zirconium leaching step is performed at a HCl concentration of 2 mol/l or more in the slurry.