JP3360333B2 - Method for producing photocatalyst and photocatalyst thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a photocatalyst, and more particularly to a photocatalyst. The present invention relates to a method for producing a photocatalyst used for synthesizing hydrogen, deodorizing various spaces such as a refrigerator and a passenger compartment, and a photocatalyst thereof.

[0002]

2. Description of the Related Art Many conventional photocatalysts contain titanium oxide as a main component. Further, a material in which gold is supported on this titanium oxide has also been proposed. (The Chemical Daily 11992
Article on the 5th of October)

[0003]

However, these conventional photocatalysts have a practical light intensity of about several tens W or less (for example,
(A germicidal lamp such as a refrigerator is about 10 W). It is considered that the reason is that electrons and holes generated in titanium oxide excited by absorbing light easily recombine.

[0004] In order to provide a novel photocatalyst free from the above-mentioned problems, the inventor of the present invention carried one or more kinds of catalyst metals on titanium oxide and other metal oxides, and developed the catalyst metal. As a result of carrying out various treatments to test and study the improvement of the photocatalytic activity, the present invention was achieved.

[0005]

Means for Solving the Problems The constitution of the first invention of the present application (the invention of the method for producing a photocatalyst described in claim 1) for solving the above-mentioned problems is to absorb and excite light to absorb electrons and holes To
Gold resulting metal oxide, nickel, chromium, copper, Koba
This is a method for producing a photocatalyst in which at least one fine particle selected from the group consisting of a catalyst and a rare earth element is supported, treated with ammonia, and then fired.

[0006] The structure of the second invention of the present application (the invention of the photocatalyst described in claim 2) for solving the above-mentioned problem is to absorb light.
Metal oxides that generate electrons and holes by excitation and are excited by gold , nickel,
At least one selected from ROM, copper, cobalt and rare earth elements
Is a photocatalyst comprising a fired body with one fine particle.

[0007]

The change that occurs in fine particles such as metal oxides and gold in the reduction or firing process of the first invention of the present application has not always been elucidated, but it is presumed that gold and / or gold carried on the metal oxide by ammonia treatment are presumed. It is thought that the salt of the transition metal and / or the rare earth element changes to an ammonium salt (or hydroxide), and this forms a special complex with the metal oxide.

Although the action of the photocatalyst of the second invention of the present application has not necessarily been elucidated, it is presumed that recombination between electrons generated by a metal oxide excited by absorption of light and holes thereof is caused by metal oxidation. That the gold and / or transition metal and / or rare earth element which formed a complex salt with the substance block the active state of the electrons and thus effectively contribute the light energy to the redox reaction. thinking.

[0009]

The photocatalyst of the present invention is effectively produced by the method for producing a photocatalyst according to the first invention of the present application, and the photocatalyst of the second invention of the present invention thus produced is sufficient even at a practical light intensity of several tens of watts or less. It shows excellent photocatalytic activity.

[0010]

Next, embodiments of the first and second aspects of the present invention will be described.

[0011] Absorbs and excites light to generate electrons and holes.
The typical metal oxide is titanium oxide Ti
O ₂ , but is not limited thereto. Absorb light
Yield and was excited, as a metal oxide generates electrons and holes, for example, tungsten oxide WO _3, iron oxide Fe ₂
O ₃ , bismuth oxide Bi ₂ O ₃ , tin oxide SnO ₂ , uranium oxide U ₃ O ₈ , cadmium oxide CdO, indium oxide InO ₃ , niobium oxide Nb ₂ O ₃ , NbO, zinc oxide ZnO, nickel oxide NiO, copper oxide Cu ₂ O, strontium titanate SrTiO ₃ , barium titanate B
aTiO ₃ , manganese titanate MnTiO ₃ , iron titanate FeTiO ₃ , calcium titanate CaTiO ₃ , strontium niobate SrNb ₂ O ₆ , cadmium stannate CdSnO ₄ , iron tantalate FeTa ₂ O ₆ , FeT
aO ₄ , potassium tantalate KTaO ₃ or the like can be used.

As for the gold, transition metal and rare earth element to be carried on the metal oxide, only one of them may be carried, or two or more kinds may be carried in an appropriate combination. When only one of the above is carried, gold is the best. In the case where two types of the above are combined and supported, there is no particular limitation, but in general, a combination of gold and one of transition metals or rare earth elements is good, and especially gold and nickel. Combinations are desirable.

There is no particular limitation on the amount of gold supported on the metal oxide.
The supported amount is about 0.5% by weight, and the optimal supported amount is about 0.1% by weight.

As the transition metal, for example, nickel, chromium, copper, and cobalt can be used, and nickel is particularly desirable.

As the rare earth element, for example, lanthanum,
Cerium, praseodymium, neodymium, dysprosium, holmium, erbium, lutetium and the like can be used.

There is no particular limitation on the amount of the transition metal or rare earth element carried on the metal oxide.
About% by weight can be supported.

The photocatalyst of the present invention may be used, for example, in the form of powder or granules, or may be used by being supported on a carrier of a predetermined shape (for example, a honeycomb shape) such as cordierite, activated carbon, and silica.

The means for supporting the metal oxide on the carrier and for supporting the metal oxide on gold, transition metal and rare earth elements is not particularly limited. Usually, a metal oxide is first supported on a carrier by a so-called wash coating method using an aqueous solution of a metal oxide to be supported or an aqueous solution of a nitrate of a metal to be supported, and then gold, transition metal,
A rare earth element is supported.

The ammonia treatment is carried out by immersing the carrier after the above-mentioned supporting treatment in aqueous ammonia (NH ₄ OH).
At this time, the processing conditions such as the concentration of the aqueous ammonia and the immersion time are not particularly limited.

When a ceramic carrier such as cordierite is used, the firing temperature is preferably about 400 to 600 ° C. Even if calcined at a temperature lower than 400 ° C., the formation of the complex salt may be insufficiently terminated.
When firing at a temperature higher than C, the crystal form of the metal oxide may be broken or changed. A particularly desirable firing temperature is around 400 to 500 ° C. On the other hand, when activated carbon is used as the carrier, the firing temperature is preferably about 150 to 200 ° C. This is because gold is not easily decomposed even when calcined at a temperature lower than 150 ° C, and activated carbon burns when calcined at a temperature higher than 200 ° C. The firing time is about several hours,
For example, about 2 hours is sufficient, but since the photocatalyst of the present invention has excellent heat resistance, its activity does not decrease so much even if it is fired at a temperature of about 500 ° C. for 8 hours.

In order to obtain the photocatalyst of the present invention supported on a carrier, first, a metal oxide is supported on the carrier, and then calcined once, and further, gold, a transition metal, and a rare earth element are supported on the metal oxide, and then calcined again. You may.

The photocatalyst of the present invention decomposes various target substances by a photochemical reaction, and has a particularly high activity for polar substances. It also shows effective activity against non-polar substances such as toluene.

[0023]

Next, an embodiment of the present invention will be described. In addition,
In each of the following examples, the supporting process was all performed by a wash coat method.

Example 1 After supporting the same amount of titanium oxide on each of the cordierite honeycomb carriers No. 1 to No. 4, the sample bodies No. 1 and No. 2 were treated with rare earth elements. A certain dysprosium was supported on the sample bodies of No. 3 and No. 4 by erbium, which is also a rare earth element, so as to be 0.1% by weight with respect to titanium oxide.
The sample bodies of No. 2 and No. 4 were immersed in 1% aqueous ammonia for 30 minutes. Each sample is placed in an air stream at 500 ° C.
For 2 hours.

Using the sample bodies No. 1 to No. 4 thus obtained, acetaldehyde purification test for 240 minutes under 5 W of condensed light irradiation (using the closed circulation system evaluation apparatus 1 shown in FIG. 8). , Air containing 50 to 200 ppm of aldehyde was sampled at regular intervals through the photocatalyst layer 2 at a rate of 5 l / min, and the residual ratio of acetaldehyde was determined by a gas chromatograph 3). The purification rate was 63.5% for No. 1, 81.4% for No. 2, N
o.3 was 62.3% and No.4 was 74.3%. The same purification test was carried out on a standard sample which had only titanium oxide supported on the honeycomb carrier and was treated with ammonia. The purification rate was 73.5%.

(Evaluation of Example 1) From the above results, when the rare earth element is supported on titanium oxide, the photocatalytic activity is improved when ammonia treatment is involved.

(Example 2) The same amount of titanium oxide was carried on each of the cordierite honeycomb carriers No. 5 to No. 8, and then each of them became 0.1% by weight based on the titanium oxide. Gold was carried as described above. And N
o. 5 is for 1% aqueous ammonia, No. 6 is for 1% aqueous sodium hydroxide solution, No. 7 is for 1% aqueous potassium hydroxide solution, No.
Sample No. 8 was immersed in a 1% aqueous solution of sodium carbonate for 30 minutes and then baked at 500 ° C. for 2 hours.

Using the sample bodies No. 4 to No. 8 thus obtained, the same purification test as in Example 1 was performed, and the results shown in FIG. 1 were obtained.

(Evaluation of Example 2) From the results shown in FIG. 1, it can be seen that the loading of gold on titanium oxide is accompanied by a significant improvement in photocatalytic activity when accompanied by ammonia treatment.

Example 3 The same amount of titanium oxide was supported on each of cordierite honeycomb carriers No. 9 to No. 13, and then 0.1% by weight (No. 9), 0.01% by weight (No. 1)
0), 0.001% by weight (No. 11), 0.005% by weight (No. 12), and 0.2% by weight (No. 13). Next, the same ammonia treatment and calcination as in No. 5 were performed on each sample.

Using the sample bodies No. 9 to No. 13 thus obtained, the same purification test as in Example 1 was performed.
Was obtained.

(Evaluation of Example 3) From the results shown in FIG. 2, it can be seen that, in the photocatalyst in which gold was supported on titanium oxide and subjected to ammonia treatment, the amount of gold supported was 0.1 to 0.1% of titanium oxide.
It was found that the amount is preferably about 005 to 0.2% by weight, and the optimal amount is about 0.1% by weight.

Example 4 The same amount of titanium oxide was carried on each of the cordierite honeycomb carriers No. 14 to No. 18, and each of them became 0.1% by weight based on the titanium oxide. No.
The same ammonia treatment as in No. 5 was performed, and No. 14 was 150 °
C, No. 15 is 300 ° C, No. 16 is 400 ° C, N
o. 17 was fired at 600 ° C. and No. 18 was fired at 500 ° C. for 2 hours, respectively, for 2 hours.

Using the samples Nos. 14 to 18 thus obtained, the same purification test as in Example 1 was performed, and the results shown in FIG. 3 were obtained.

(Evaluation of Example 4) From the results shown in FIG. 3, it is found that the firing temperature of the photocatalyst obtained by supporting gold on titanium oxide and performing the ammonia treatment is 400, 50.
0,600 ° C. is preferable, and a particularly preferable firing temperature is 50 ° C.
It was 0 ° C.

Example 5 The same amount of titanium oxide was carried on each of the cordierite honeycomb carriers of Nos. 19 and 20, and these were then adjusted to 0.1% by weight based on the titanium oxide. The same ammonia treatment as in No. 5 was carried out by supporting gold, and at 500 ° C., N
o. 19 for 2 hours, No. 20 for 8 hours,
The same baking as in Example 5 was performed.

Using the sample bodies No. 19 and No. 20 thus obtained, the same purification test as in Example 1 was performed, and the results shown in FIG. 4 were obtained.

(Evaluation of Example 5) From the results shown in FIG. 4, it can be seen from the results shown in FIG. 4 that the firing time of a photocatalyst fired by carrying gold on titanium oxide and performing an ammonia treatment is 500 ° C. Two hours is sufficient, and on the other hand, the photocatalytic activity does not decrease so much even after firing for eight hours, indicating that the heat resistance of the photocatalyst of this example is excellent.

Example 6 Titanium oxide was supported on a cordierite honeycomb carrier of No. 21, and then 0.1% by weight and 0.1% by weight of titanium oxide were added to titanium oxide. % And carried out the same ammonia treatment as in No. 5;
The same baking was performed.

Using this No. 21 sample, a toluene concentration of 20 pp was obtained in the same manner as in the aldehyde purification test described above.
m, a toluene purification test was performed, and the results in FIG. 5 were obtained.

(Evaluation of Example 6) From the results shown in FIG. 5, it can be seen that the photocatalyst obtained by carrying gold and nickel on titanium oxide and performing the ammonia treatment shows a purification activity, though not as large as that of the aldehyde. I understood that.

Example 7 The same amount of titanium oxide was carried on each of the cordierite honeycomb carriers No. 22 to No. 24, and each of them became 0.1% by weight based on the titanium oxide. No. 22, copper, No. 22
No. 23 carried cobalt and No. 24 carried nickel, respectively, and the same ammonia treatment and calcination as in No. 5 were performed.

The same purification test as in Example 1 was performed using these sample Nos. 22 to 24, and the results shown in FIG. 6 were obtained.

(Evaluation of Example 7) From the results in FIG. 6, it is found that the photocatalyst obtained by carrying a transition metal on titanium oxide and performing an ammonia treatment and firing is not as effective as the case of carrying gold, but has a constant purification. It was found to show activity.

Example 8 The same amount of titanium oxide was carried on each of the cordierite honeycomb carriers No. 25 to No. 27, and each of them became 0.1% by weight based on the titanium oxide. No.
For No. 25, copper was further supported at 0.1% by weight based on titanium oxide, and for No. 26, nickel was further supported at 0.1% by weight based on titanium oxide. The same ammonia treatment and firing as in No. 5 were performed.

The same purification test as in Example 1 was performed using these sample Nos. 25 to 27, and the results shown in FIG. 7 were obtained.

(Evaluation of Example 8) From the results shown in FIG. 7, it was found that gold and nickel were supported in the photocatalyst which was prepared by supporting gold or gold and a transition metal on titanium oxide, and calcination after ammonia treatment. It has been found that the case shows particularly excellent purification activity.

[Brief description of the drawings]

FIG. 1 is a graph showing test results of Example 2.

FIG. 2 is a graph showing test results of Example 3.

FIG. 3 is a graph showing test results of Example 4.

FIG. 4 is a graph showing test results of Example 5.

FIG. 5 is a graph showing test results of Example 6.

FIG. 6 is a graph showing test results of Example 7.

FIG. 7 is a graph showing test results of Example 8.

FIG. 8 is a schematic view of an apparatus used for a purification test of the present invention.

────────────────────────────────────────────────── ─── Continued on front page (51) Int.Cl. ⁷ Identification code FI B01J 23/89 B01J 23/74 311A 35/02 321A

Claims (2)

(57) [Claims] 1. A method for absorbing and exciting light to generate electrons and holes.
Gold that metal oxide, nickel, chromium, copper, cobalt,
A method for producing a photocatalyst, comprising supporting at least one fine particle selected from rare earth elements, subjecting the fine particle to ammonia treatment, and firing. 2. Excitation by absorbing light to generate electrons and holes.
And a metal oxide that, this is carried ammoniated gold, nickel, chromium, copper, cobalt, or a rare earth element
A photocatalyst comprising a fired body with at least one fine particle selected from the group consisting of: