JPH07232072A - Hydrogen peroxide decomposition catalyst and its preparation - Google Patents

Abstract

PURPOSE:To obtain a catalyst with excellent durability for use and without falling down and eluation of the catalyst metal during decompsn. of hydrogen peroxide by providing a porous carrier and a catalyst active ingredient layer adhered into a thin film-like shape only on the surface part of this carrier and consisting of a reduction product of an Ir compd. CONSTITUTION:A porous carrier 1 and a catalyst active ingredient layer 2 adhered into a thin film-like shape only on the surface part of this carrier and consisting of a reduction product of an Ir compd. are provided. In addition, the carrier 1 is a particulate alumina and the Ir compd. is a compd. expressed by a chem. formula: HnIrXm is a halogen atom and n is an integer of 0, 1 or 2 and m is an integer of 3-6). In addition, the thickness W of a thin film-like catalyst active ingredient layer 2 is 100-300mum. In a method for preparing this hydrogen peroxide decompsn. catalyst, the porous particulate carrier is impregnated with an org. solvent soln. of an Ir compd. and this carrier impregnated with the metal compd. org. solvent soln. is dried and burned and then, reduction treatment is performed thereon.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a catalyst for decomposing hydrogen peroxide and a method for producing the same. More specifically, the present invention relates to a granular catalyst for decomposing hydrogen peroxide for disinfecting soft contact lenses and a method for producing the same.

[0002]

2. Description of the Related Art Heretofore, as a hydrogen peroxide decomposition catalyst, a catalyst in which palladium, platinum or the like is supported on various carriers has been known. However, the conventional catalyst for decomposing hydrogen peroxide supporting palladium has poor durability, and the palladium metal component is removed from the carrier during the decomposition reaction of hydrogen peroxide. It was unsuitable for use on articles that come into direct contact with.

[0003]

DISCLOSURE OF THE INVENTION The present invention is intended to provide a catalyst which is excellent in use durability and does not drop off or elute catalytic metal components during decomposition of hydrogen peroxide, and a method for producing the same.

[0004]

Means for Solving the Problems
As a result of repeated intensive studies to resolve
A catalyst that uses iridium as the active component of the catalyst is suitable
And when using iridium, its adsorption form
Paying attention to H, which is inexpensive as an iridium source ₂ IrC
l₆ Or IrCl_3,4 Iridium compound such as
And support a porous material such as granular alumina.
Manufactured by the impregnation method using an organic solvent
The produced catalyst has the iridium-containing active ingredient as a carrier surface.
It adheres to the surface only in a thin film, and hydrogen peroxide
Unexpectedly high activity in decomposition reactions, and
It has high durability and therefore, during the decomposition reaction of hydrogen peroxide,
No loss of active ingredients containing iridium metal
The present invention has been completed and the present invention has been completed.

That is, the hydrogen peroxide decomposition catalyst of the present invention is
It is characterized in that it has a porous carrier and a catalytically active component layer which is attached in a thin film form only on the surface of the carrier and which is composed of a reduction product of an iridium compound.

Further, in the method for producing a hydrogen peroxide decomposition catalyst of the present invention, a porous granular carrier is impregnated with an organic solvent solution of an iridium compound, the metal compound-organic solvent solution impregnated carrier is dried, and then subjected to a reduction treatment. It is characterized by applying.

In the catalyst produced by the method of the present invention as described above, the catalytically active component adheres to the surface of the porous carrier only in a thin film form, preferably in a thin film form of 100 to 300 μm, and is excellent. It exhibits catalytic activity and very excellent durability.

[0008]

[Function] The hydrogen peroxide decomposition catalyst of the present invention has a diameter of 2 to 6 mm.
Of the above-mentioned porous granular carrier, for example, a granular alumina carrier, and a catalytically active component composed of a reduction product of an iridium compound supported in a thin film form only on the surface portion thereof.

To describe one embodiment of the method of the present invention,
As a method of supporting a catalytically active component on a carrier made of porous granular alumina, a method of impregnating this granular carrier with an organic solvent solution containing an iridium compound, drying and firing, and reducing it. The iridium compound and the organic solvent may be any compound as long as the iridium compound is soluble in the organic solvent. From the viewpoint of price and handling, the iridium compound has the chemical formula: H _n IrX _m (where X represents a halogen atom). , N
Represents 0 or an integer of 1 to 2 and m represents an integer of 3 to 6), for example, H ₂ IrCl ₆ or IrCl.
It is preferable to use _3,4 (a mixture of IrCl ₃ and IrCl ₄ ), and as the organic solvent, an aliphatic alcohol having 1 to 4 carbon atoms and a cycloaliphatic alcohol having 3 to 4 carbon atoms, for example, methanol Alternatively, the use of ethanol is preferred.

The loading amount of the iridium-containing catalytically active component is
It is preferably 0.1 to 10% based on the weight of the carrier. If it is less than 0.1%, the catalytic activity may be insufficient, and even if it is supported by more than 10%, no improvement in performance may be seen and it may be economically disadvantageous.

In the catalyst of the present invention, for example, H ₂ IrCl ₆ or IrCl _3,4 is used as the iridium compound, and the metal contained in the hydrogen peroxide-decomposable metal-containing granular catalyst obtained by an impregnation method using an organic solvent. The contained catalytically active component is in the form of a thin film and firmly adhered and supported only on the surface portion of the carrier particles, and has excellent hydrogen peroxide decomposition activity and durability. This catalytically active component is impregnated into a thin film only on the surface of the porous carrier and has a thickness of 1
It is preferably from 00 to 300 μm. This thickness is 1
If it is less than 00, the activity of the obtained catalyst may be insufficient, and if it is more than 300 μm, the efficiency of the catalytically active component may decrease, which may be disadvantageous in practical use.

On the other hand, as an iridium compound,
For example, even if an iridium compound such as H ₂ IrCl ₆ or IrCl _3,4 is used and water is used as a solvent,
The iridium-containing catalytically active component in the iridium-alumina granular catalyst obtained by the impregnation method penetrates evenly into the inside of the alumina carrier and is evenly distributed, and the catalyst as a whole has a very high hydrogen peroxide decomposition activity. It is recognized that it is very low.

The reason why there is a large difference in the decomposition activity of hydrogen peroxide due to the difference in the distribution form of the catalytically active component containing iridium is that the decomposition reaction of hydrogen peroxide is mainly carried out on the surface of the catalyst particles. It is possible that
That is, it is considered that the catalytically active components distributed inside the carrier are not effectively used.

When a catalyst is produced by an impregnation method using an iridium compound such as H ₂ IrCl ₆ or IrCl _3,4 , the reason why the distribution state of the catalytically active component is changed by using an organic solvent as the impregnation medium. Is
Although not fully clarified yet, it is considered as follows. That is, when water is used as a medium, the ligand of the iridium compound is substituted with a hydroxyl group to form a stable aco-complex surrounded by hydrated shells, and therefore this complex is a carrier, for example, oxygen on the surface of alumina particles. Therefore, it is considered that the catalyst permeates into the inside of the carrier, for example, alumina without being ligand-exchanged, and is uniformly adsorbed and distributed in the carrier, resulting in a catalyst having low activity.

On the other hand, when an organic solvent is used, the ligand of the iridium compound is replaced by a solvent molecule, but this ligand is easily replaced by another ligand, for example, an atom or group of the carrier. Will be replaced. Therefore, this complex is ligand-exchanged and fixed by oxygen on the surface of the carrier, for example, alumina, and cannot penetrate into the interior, so that the iridium compound is distributed only on the outer surface of the carrier so as to form a thin film. It is assumed that it takes a form and becomes a catalyst showing high activity on the surface of the carrier.

The carrier used in the present invention can be selected from alumina, silica, titania, zirconia, and activated carbon porous particles. The particle size of such a carrier is not limited, but generally 0.1 to 1
It is preferably 0 mm, more preferably 2 to 6 mm. In the method of the present invention, it is preferable to use granular alumina having a particle size of 2 to 6 mm as a carrier. The porous granules preferably have a pore volume of 0.2 to 1.0 cm ³ / g.

The iridium compound used in the present invention is
There is no particular limitation as long as the reduction product has a catalytic action for decomposing hydrogen peroxide. For example, the following formula: H _n IrX _m [wherein X is a halogen atom, that is, F, C
represents any one of l, Br and I, n is 0 or 1-2.
Of the iridium compound, and m represents an integer of 3 to 6].

The organic solvent used in the method of the present invention is an aliphatic alcohol having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, propyl alcohol and butyl alcohol, or a cycloaliphatic having 3 to 4 carbon atoms. It is preferably selected from alcohols such as cyclopropanol and cyclobutanol. The aliphatic alcohol may be either a straight chain alcohol or a branched chain alcohol.

In the method of the present invention, the iridium compound is preferably dissolved in an organic solvent at a concentration of 0.01 to 10% by weight. The granular carrier is immersed in the iridium compound solution, taken out, and dried. Then, the dried product is preferably in air, for example, at 110 to 900 ° C., more preferably at 300 to 500 ° C., further preferably at 350 ° C.
It is preferable to perform firing at a temperature of ℃ to 450 ℃ for 10 minutes to 24 hours. Next, this fired body is subjected to a reduction treatment. As the reduction method, for example, in hydrogen gas, preferably room temperature to 900 ° C., more preferably 300 to 500 ° C.,
More preferably, at a temperature of 350 to 450 ° C. for 10 minutes to 2
It is preferable to perform hydrogen reduction for 4 hours. As another reduction method, SBH, hydrazine, formaldehyde, formic acid, or the like can be used.

[0020]

EXAMPLES The present invention will be described in more detail with reference to the following examples and comparative examples. The hydrogen peroxide decomposition activity of the catalyst of the present invention is
It was measured by the following ABTS hydrogen peroxide concentration quantitative method. ABTS method First, sodium phosphate dihydrate (special grade reagent): 1
0.92 g and disodium phosphate dodecahydrate (reagent special grade): 46.00 g were dissolved in purified water to obtain a pH of 7.0 ± 0.
After adjusting to 1, the total amount is adjusted to 1 liter to obtain a phosphate buffer solution. Then, 2,2'-azinobis (3-ethyl benzo thiazoline-6-sulfonic acid) 2NH ₄ salt (AB
TS reagent special grade: 0.113 g and peroxidase (Sigma Type 1): 100 units are dissolved in the above phosphate buffer to make 100 ml, and an ABTS reagent is prepared (prepared before use). Next, this reagent solution (hydrogen peroxide solution)
Was diluted to 70 ppm or less, 0.1 ml of which was collected, added to 4.9 ml of the ABTS reagent and stirred, and then 420
The absorbance at nm is measured (a blank test is used as a control), and at the same time, a calibration curve is prepared to calculate the concentration.

[0021]Example 1 Granular alumina (trademark: activated
Lumina granular product (spherical) KHS-46 or KHA-2
(4, Sumitomo Chemical Co., Ltd.) 10g, IrCl _3,4 D
Tanol solution (iridium concentration = 0.50% by weight) 20
g and add 2 while stirring with a rotary evaporator.
Ethanol was distilled off under reduced pressure at 5 ° C. 1 for the obtained impregnated product
Dry at 10 ° C for 2 hours and bake at 400 ° C for 1 hour.
The catalyst is prepared by subjecting it to hydrogen reduction treatment at 400 ° C for 3 hours.
Made

Example 2 A catalyst was prepared in the same manner as in Example 1 except that a methanol solution of IrCl _3,4 (iridium concentration = 0.50%) was used as the impregnating liquid to obtain catalyst 2. .

Example 3 Example 1 was repeated, except that an ethanol solution of H ₂ IrCl ₆ (iridium concentration = 0.50%) was used as the impregnating liquid.
A catalyst was prepared in the same manner as in, to obtain catalyst 3.

Example 4 Example 1 was repeated except that a methanol solution of H ₂ IrCl ₆ (iridium concentration = 0.50%) was used as the impregnating liquid.
A catalyst was prepared in the same manner as in, to obtain catalyst 4.

Comparative Example 1 A catalyst was prepared in the same manner as in Example 1 except that an aqueous solution of H ₂ IrCl ₆ (iridium concentration = 0.50%) was used as the impregnating liquid.

Comparative Example 2 Using the iridium-alumina granular catalyst produced by the conventional impregnation method as catalyst B, it was subjected to a decomposition activity test.

Hydrogen Peroxide Decomposition Activity Test Table 1 and FIG. 1 show the method for producing the hydrogen peroxide decomposition catalysts of Examples 1 to 4 and Comparative Examples 1 and 2, the conditions for the hydrogen peroxide decomposition activity test, and the results. In addition, in the hydrogen peroxide decomposition activity test method, the catalyst 0.25 was added to the vial.
After adding 2 ml of 3% aqueous hydrogen peroxide per gram and allowing it to stand at room temperature for 4 hours, the concentration of residual hydrogen peroxide was measured. The above operation was repeated to evaluate the durability performance of the catalyst. The number on the vertical axis of FIG. 1 indicates the concentration of residual hydrogen peroxide (unit: ppm) (thus, the smaller the number, the higher the decomposition activity of the catalyst used). The horizontal axis indicates the number of times the test was repeated.

[0028]

[Table 1]

Example 5 A catalyst was prepared in the same manner as in Example 1 except that 20 g of an ethanol solution of H ₂ IrCl ₆ (iridium concentration 0.75%) was used as an impregnating solution to obtain a catalyst 5.

Comparative Example 3 A catalyst was prepared in the same manner as in Example 1 except that 20 g of an ethanol solution of H ₂ PtCl ₆ (platinum concentration: 0.75%) was used as an impregnating solution to obtain a catalyst C.

Comparative Example 4 H ₂ PtCl ₆ aqueous solution (platinum concentration 0.7
A catalyst was prepared in the same manner as in Example 1 except that 20 g of 5%) was used to obtain a catalyst D.

Comparative Example 5 20 g of an ethanol solution (palladium concentration 0.75%) of PdCl ₂ dissolved in a small amount of concentrated hydrochloric acid as an impregnating liquid.
A catalyst was obtained in the same manner as in Example 1 except that the catalyst was used.

Hydrogen Peroxide Decomposition Activity Test Table 2 and FIG. 2 show the conditions for producing the catalysts of Example 5 and Comparative Examples 3 to 5, and the reaction conditions and results of the hydrogen peroxide decomposition tests of the catalysts 5, C and D. . However, in the hydrogen peroxide decomposition test of Comparative Example 5 (catalyst E), its resolution was low,
The residual hydrogen peroxide concentration was too high to measure.

[0034]

[Table 2]

Metal elution test during decomposition of hydrogen peroxide In a 300 ml beaker, 7. of each of catalysts 5, C, and D.
Take 5g, add 100ml of 3% hydrogen peroxide solution to it,
After standing at 20 ° C. for 4 hours, filtration was performed and the amount of metal eluted was measured using ICP. The results are shown in Table 3. The catalyst E (Comparative Example 5) was not quantified by ICP because coloration due to metal elution was visually observed during the reaction.

[0036]

[Table 3]

Catalyst Cross Sections The catalyst particles of Examples 1 to 5 and Comparative Examples 1 to 5 were cut with scissors, and the cross sections were observed with a microscope (Video Microscope VMS-110A, manufactured by Scalar, magnification 50 times). In the catalysts of Examples 1 to 5 and Comparative Example 3, as shown in FIG.
Was formed in a thin annular shape on the surface of the carrier 1, and its thickness W was 100 to 300 μm. In the catalysts A, B and E of Comparative Examples 1, 2 and 5, the catalytically active component was permeated and distributed almost uniformly from the surface to the center of the carrier particles. In the cross section of the catalyst D of Comparative Example 4, as shown in FIG. 4, the catalytically active component 2 was distributed in the form of a thick ring with a thickness of 500 to 800 μm from the surface of the carrier particles 1.

From the test results shown in Tables 1 to 3 and FIGS. 1 to 4, the iridium catalyst produced by the method of the present invention has not only excellent hydrogen peroxide decomposition activity performance superior to the catalyst produced by the conventional method, It was confirmed that it showed excellent durability and that the metal did not fall off during the reaction, which was one of the problems of the conventional method.

[0039]

INDUSTRIAL APPLICABILITY The catalyst of the present invention exhibits not only excellent hydrogen peroxide decomposing activity but also unexpectedly excellent durability, and such a catalyst can be efficiently produced by the method of the present invention. became.

[Brief description of drawings]

FIG. 1 is a graph showing hydrogen peroxide decomposition performance and durability of a catalyst of the present invention (Examples 1 to 4) and a comparative catalyst (Comparative Examples 3 to 4).

FIG. 2 is a graph showing hydrogen peroxide decomposition performance and durability of the catalyst of the present invention (Example 5) and the comparative catalyst (Comparative Examples 3 to 4).

FIG. 3 shows an example of the catalyst of the present invention (Examples 1 to 5), and
FIG. 6 is a cross-sectional explanatory view showing a distribution state of catalytically active component layers in a cross section of the catalyst of Comparative Example 3.

FIG. 4 is a cross-sectional explanatory view showing a distribution state of catalytically active component layers in a cross section of a comparative catalyst (Comparative Example 4).

[Explanation of symbols]

 1 ... Carrier particles 2 ... Catalytic active ingredient layer W ... Thickness

Claims (7)

[Claims] 1. A method for decomposing hydrogen peroxide, comprising a porous carrier and a catalytically active component layer which is adhered in a thin film form only on the surface of the carrier and which is composed of a reduction product of an iridium compound. Solid catalyst. 2. The solid catalyst according to claim 1, wherein the support is granular alumina. 3. The iridium compound has the chemical formula: H _n
IrX _m [wherein X represents a halogen atom and n is 0].
Or an integer of 1 to 2 and m is an integer of 3 to 6]. The solid catalyst according to claim 1. 4. The thickness of the thin film catalytically active component layer is 10
The solid catalyst according to claim 1, which is 0 to 300 μm. 5. The method according to claim 1, wherein the porous granular carrier is impregnated with an organic solvent solution of an iridium compound, the carrier impregnated with the organic solvent of the metal compound is dried and calcined, and the carrier is subjected to a reduction treatment. 4. The method for producing a hydrogen peroxide decomposition catalyst according to any one of 4 above. 6. The production according to claim 5, wherein the organic solvent comprises at least one selected from an aliphatic alcohol having 1 to 4 carbon atoms and a cycloaliphatic alcohol having 3 to 4 carbon atoms. Method. 7. The reduction treatment is hydrogen reduction treatment,
The manufacturing method according to claim 5 or 6.