JP2005330174A - Method for manufacturing tetragonal zirconia sol - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple method for manufacturing tetragonal zirconia sol. <P>SOLUTION: The method is characterized in that sulfuric acid is added to a solution containing zirconia sol. Preferably, the concentration of ZrO<SB>2</SB>in the zirconia sol-containing solution is 1-30% and the quantity of the sulfuric acid to be added in terms of 100% sulfuric acid is set at the H<SB>2</SB>SO<SB>4</SB>/ZrO<SB>2</SB>weight ratio of 0.01-0.5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a tetragonal zirconia sol.

Zirconia sol has been used as a binder (binder) in the production of various refractory materials, casting molds and the like. Recently, attempts have been made to impregnate a paper honeycomb or the like with zirconia sol and use it as a catalyst or catalyst carrier for an exhaust gas purification catalyst. In this case, the zirconia (ZrO ₂ ) obtained by firing the zirconia sol is a tetragonal crystal that is a metastable phase of zirconia during heat treatment at 500 ° C. in order to ensure heat stability when the thermal cycle is repeated Has come to be required.

  In Patent Document 1, “(1) a step of providing an aqueous solution containing a polyether acid zirconium salt; and (2) a solution at a temperature and pressure sufficient to convert the polyether acid zirconium salt into crystalline zirconia particles. A method of producing a zirconia sol comprising the step of hydrolyzing an aqueous solution of a polyether acid zirconium salt by heating ”is disclosed, wherein“ the average primary particle size is about 20 nm or less and the dispersion index is 1 to 3 ”. In a zirconia sol comprising an aqueous phase having a plurality of substantially unassociated single crystal zirconia particles within range dispersed therein, the zirconia particles have a crystallinity of about 0.65 or higher and a combination of about 70% or higher Zirconia sols having type cubic and tetragonal crystal lattice structures in the absence of effective amounts of crystalline phase stabilizers.

Patent Document 2 states that “a base is added to an aqueous zirconium salt solution to form a precipitate, and most of the soluble portion is washed away with water, and then an alkaline earth metal hydroxide or an aqueous solution thereof is added, and the resulting mixture is obtained. A method of producing a sol in which tetragonal or cubic ZrO ₂ -based single crystal ultrafine particles are dispersed by heating and aging a suspension or paste at a temperature of 90 ° C. to 200 ° C. is disclosed. A sol in which isolated ZrO ₂ —CaO-based solid solution single crystal ultrafine particles having a type crystal lattice and having a substantially uniform particle size of 200 mm or less are dispersed ”is described.

  Further, in Patent Document 3, “in the method of producing a zirconium precursor sol by hydrolyzing zirconium alkoxide, zirconium hydroxide is hydrolyzed by adding hydrogen peroxide water containing an acid to the zirconium alkoxide or a solution thereof. “Precursor sol production method” is disclosed, and it describes that “tetragonal zirconia can be obtained by firing at 500 ° C.”.

  However, in the method described in Patent Document 1, “special zirconium salt”, in the method described in Patent Document 2, “alkaline earth metal hydroxide or an aqueous solution thereof”, and further described in Patent Document 3. The method needs to use “zirconium alkoxide and hydrogen peroxide”, and there is no method that can produce “tetragonal zirconia sol” by a relatively simple method.

      Japanese translation of PCT publication No. 2003-512287       Japanese Examined Patent Publication No. 4-72768       Japanese Patent Publication No. 7-29772

The present invention has been made in view of the above problems, and an object thereof is to provide a method capable of producing a tetragonal zirconia sol by a simple method.
In the present invention, “tetragonal zirconia sol” refers to a material in which zirconia (ZrO ₂ ) produced when heat-treating zirconia sol exhibits an X-ray diffraction pattern of tetragonal zirconia.

As a result of intensive studies to achieve the above object, the present inventors have unexpectedly found that a tetragonal zirconia sol can be obtained by adding sulfuric acid to a zirconia sol-containing solution.
Based on this finding, the present invention
(1) A method for producing a tetragonal zirconia sol, characterized by adding sulfuric acid to a zirconia sol-containing solution,
(2) The method for producing a tetragonal zirconia sol according to (1), wherein the ZrO ₂ concentration in the zirconia sol-containing solution is 1 to 30%,
(3) the addition amount of 100% sulfuric acid in terms of sulfuric _acid, said, characterized in that the H ₂ SO 4 / ZrO ₂ (weight ratio) 0.01-0.5 (1) or (2) according A method for producing a tetragonal zirconia sol is provided.

  According to the present invention, a tetragonal zirconia sol can be produced by a simple method, and therefore can be suitably used in this field.

Hereinafter, the method for producing the tetragonal zirconia sol of the present invention will be described in detail.
First, the zirconia sol-containing solution used in the present invention is not particularly limited, and may be prepared by any manufacturing method.
Examples of the method for producing zirconia sol include the following.
(1) A method of obtaining a zirconia hydrosol by heating an aqueous zirconium salt solution at 120 to 300 ° C. under hydrothermal pressure, as described in US Pat. No. 2,984,628.
(2) A method for obtaining a zirconia sol by boiling a zirconium salt aqueous solution for a long period of time as described in “A. Clearfield; Inorganic Chemistry, Vol. 3, page 146, 1964”.
(3) A hydrated zirconium sol is produced by decomposition of urea using at least one selected from the group of zirconium oxychloride and zirconium nitrate described in JP-A-4-104910 as a zirconium source. A method for producing a hydrated zirconium sol, wherein at least one ammonium salt selected from the group consisting of ammonium nitrate, ammonium chloride, and ammonium sulfate is added during the decomposition of urea.
In the present invention, zirconia sol-containing solutions prepared by other known methods are also targeted.

The ZrO ₂ concentration in the zirconia sol-containing solution is preferably 1 to 30%. If it is less than 1 g / L, too much water will cause hydrolysis during the heat treatment, and if it exceeds 30%, the zirconia sol will cause thickening or gelation, which is not preferable.
The pH of the zirconia sol-containing solution is not particularly limited, but is preferably 1 to 4.
The zirconia sol in such a zirconia sol-containing solution usually exhibits a monoclinic crystal even when calcined at an amorphous or high temperature. In the present invention, by adding sulfuric acid to these zirconia sol-containing solutions. Can be converted to tetragonal zirconia sol.
The reason for this is not clear at present, but it is presumed that it is partially stabilized by containing SO ₄ so as to be stabilized by Y or Sc.
The concentration of sulfuric acid added to the zirconia sol-containing solution is not particularly limited, but is preferably 90% or more.
Further, the addition amount of sulfuric acid is preferably H ₂ SO ₄ / ZrO ₂ (weight ratio) 0.01 to 0.5 in terms of 100% sulfuric acid. If it is less than 0.01, it is almost monoclinic, and if it exceeds 0.5, the zirconium oxide colloidal particles are dissolved, which is not preferable.
In addition, after adding and mixing sulfuric acid, it is preferable to let it stand for one day or more.

  Examples are given below to further clarify the features of the present invention. In addition, this invention is not limited to the aspect of this Example.

〔Example〕
A zirconia sol-containing solution was prepared in accordance with Example 3 of US Pat. No. 2,984,628, except that 28% zirconyl nitrate (ZrO (NO ₃ ) ₂ ) solution was used and concentration was performed by ultrafiltration. This zirconia sol-containing solution contained 10% as ZrO ₂ , pH = 3, and the average particle diameter of the zirconia sol was about 10 nm.
Then, 100 ml each of the obtained zirconia sol-containing solution, (1) ammonium sulfate, ( ₂ ) ammonium persulfate and (3) sulfuric acid (concentration: 90%), SO ₄ / ZrO ₂ (weight ratio) becomes 0.1 When added and mixed as described above, the one to which ammonium sulfate was added gelled. The remaining two samples did not gel and were left as they were overnight.
Three kinds of samples obtained by adding a stock zirconia sol-containing solution to these two samples were dried at 60 ° C. for 24 hours, and then heat-treated at 400, 500, 700, 900, and 1000 ° C. for 1 hour.
About what performed this heat processing, it evaluated by X-ray diffraction and a result is shown in FIGS.
As is apparent from the figure, the sulfuric acid-added product that was heat-treated at 400 ° C. showed a peak of only tetragonal crystals, and that the monoclinic crystal peak gradually increased as the heat treatment temperature was increased, and the stock solution itself and It was found that the ammonium persulfate added did not show a tetragonal peak at any heat treatment temperature.
In addition, about the sample which added the sulfuric acid and heat-processed at 1000 degreeC, the weight ratio of a tetragonal crystal / monoclinic crystal is about 0.5.

It is a graph which shows the peak position and intensity | strength by X-ray diffraction at the time of heat-processing the stock solution in an Example. It is a graph which shows the peak position and intensity | strength by X-ray diffraction at the time of heat-processing the ammonium persulfate addition product in an Example. It is a graph which shows the peak position and intensity | strength by X-ray diffraction at the time of heat-processing the sulfuric acid addition goods in an Example.

Claims (3)

A method for producing a tetragonal zirconia sol, comprising adding sulfuric acid to a zirconia sol-containing solution. The method for producing a tetragonal zirconia sol according to claim 1, wherein the ZrO ₂ concentration in the zirconia sol-containing solution is 1 to 30%. 3. The tetragonal zirconia sol according to claim 1, wherein the amount of sulfuric acid added is H ₂ SO ₄ / ZrO ₂ (weight ratio) 0.01 to 0.5 in terms of 100% sulfuric acid. Production method.

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