JPH09301705A - Production of hydrogen peroxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce H2 O2 high in conc. under low pressure with high hydrogen selectivity by using a specified catalyst when H2 O2 is produced by catalytically reacting O2 with H2 in a reaction medium. SOLUTION: The catalyst used is prepared by depositing titania and platinum group metal (e.g. Pd) on a carrier preferably comprising silica or alumina, or by depositing titania on a carrier and further depositing platinum group metal. Titania is preferably obtd. by hydrolyzing titanium alkoxide (e.g. ortho ethylitanate) as the source material to obtain titanium hydroxide, depositing the obtd. titanium hydroxide on the carrier surface, and calcining preferably at 300 to 1,000 deg.C. H2 O2 is produced by catelytically reacting H2 with O2 in a reaction medium which is a soln. containing acid (e.g. phosphoric acid) and halide (NaBr) in the presence of the catalyst at the pressure of 0.1 to 2MPa.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an improved process for catalytically reacting oxygen and hydrogen in a reaction medium to produce hydrogen peroxide. More specifically, the present invention relates to a method for producing a high concentration of hydrogen peroxide under low pressure by reacting oxygen and hydrogen on a platinum group catalyst composed of a carrier having titania supported on its surface.

[0002]

2. Description of the Related Art Currently, the main method of industrially producing hydrogen peroxide is an autoxidation method using alkylanthraquinone as a medium. The problem with this method is that it requires many steps such as reduction of alkylanthraquinone, oxidation, extraction and separation of the produced hydrogen peroxide, purification and concentration, which complicates the process, resulting in equipment costs and operating costs. Is large. Further, there are problems such as loss due to deterioration of alkyl anthraquinone and deterioration of activity of the reduction catalyst.

In order to solve these problems, a manufacturing method other than the above-mentioned manufacturing method has been tried, one of which is as follows.
There is a method of producing hydrogen peroxide directly from oxygen and hydrogen using a catalyst in a reaction medium. For example, a method of producing hydrogen peroxide from oxygen and hydrogen using a platinum group metal as a catalyst has been proposed, and it is known that hydrogen peroxide is produced at a considerable concentration (for example, Japanese Patent Publication No. 56- 471
21, Japanese Patent Publication No. 55-18646, Japanese Patent Publication No. 1-234
01, JP-A-63-156005). In these,
In both cases, the reaction pressure is 2 MPa or more, and an aqueous solution in which an acid or an inorganic salt is dissolved is used as a reaction medium. In order to suppress the decrease in selectivity during the reaction, the activity of the catalyst is suppressed by adding halogen ions to the reaction medium, and the selectivity of the hydrogen peroxide generation reaction is greatly improved. Has been shown to be high.

Japanese Patent Laid-Open No. 63-156005 discloses a method for producing hydrogen peroxide from oxygen and hydrogen under pressure in a sulfuric acid acidic aqueous solution using a platinum group catalyst. It is shown that high concentration hydrogen peroxide can be selectively produced by coexisting with ions. That is, in the conventional technique, in order to obtain hydrogen peroxide with a high selectivity in the method of producing high-concentration hydrogen peroxide by catalytically reacting oxygen and hydrogen in a reaction medium, 2 MPa or more is required. It was necessary to carry out the reaction under high pressure.
Further, it has been shown that a high-concentration hydrogen peroxide can be obtained under a low pressure without significantly lowering the selectivity in a production method using a platinum group metal catalyst using titania as a carrier (see, for example, Japanese Patent Application Laid-Open No. H10 (1999) -242242). 8-2904). However, it is difficult to put titania into practical use as an industrial catalyst because many titania particles have a small particle size and the particle shape is easily crushed.

[0005]

DISCLOSURE OF THE INVENTION In a method for producing hydrogen peroxide by catalytically reacting oxygen and hydrogen in a reaction medium, the conventional known technique is to obtain a practical concentration of hydrogen peroxide. It was necessary to react under high pressure. When the reaction is carried out under high pressure as described above, an expensive reaction vessel having excellent pressure resistance is required as an apparatus that can be used for handling, and an economical problem such as pressure increase of the reaction gas to be supplied is required. there were. Further, in the presence of a high concentration of hydrogen peroxide, the generated hydrogen peroxide is decomposed, and there is a big problem that the selectivity is significantly lowered. Also,
Although the titania catalyst can be reacted under a low pressure, it is difficult to put it into practical use as an industrial catalyst because it is easily crushed.

[0006]

Means for Solving the Problems The present inventors have proposed a method for producing hydrogen peroxide by catalytically reacting oxygen and hydrogen in a reaction medium using a platinum group catalyst. The above problems have been solved by supporting titania and a platinum group catalyst on a suitable other oxide carrier such as. That is, the present invention is a catalyst that supports titania and a platinum group metal on a carrier that is difficult to crush, and by catalytically reacting oxygen and hydrogen using an aqueous solution as a reaction medium, a high concentration of hydrogen peroxide is obtained under low pressure. It is intended to provide a method for producing hydrogen peroxide, which makes it possible to obtain the hydrogen peroxide. According to the present invention, the problem of the reactor and the problem of the decrease in the selectivity with respect to the hydrogen peroxide concentration have been significantly improved.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a catalyst in which an active component mainly containing a platinum group element is supported on a carrier is used. Specifically, palladium, platinum, etc. can be used alone or as a mixture or alloy. Furthermore, it is also possible to use a mixture or alloy containing ruthenium, osmium, rhodium, iridium or gold, which is the main component of these. Particularly, a catalyst containing palladium as a main component is preferably used. The amount of the active ingredient supported is 0.
1 to 10% by weight is common.

As the carrier used in the present invention, titanium alkoxide is hydrolyzed to support titanium hydroxide on the surface of an oxide carrier such as alumina or silica which is excellent in handling and mechanical strength. This is a carrier which is calcined to give titania on the above-mentioned oxide carrier.
Specifically, spherical silica having an average particle size of 50 microns is dispersed in ethanol, ethyl orthotitanate is added and sufficiently stirred, and then water is added to hydrolyze the ethyl orthotitanate to obtain silica particles. Titanium hydroxide is deposited on. Probably because titanium alkoxide such as ethyl orthotitanate is well dispersed in the pores of silica, titanium hydroxide can be uniformly dispersed on the silica carrier.

The silica-supported titanium hydroxide carrier thus obtained is
After removing ethanol by washing with water, the silica-supported titania carrier is dried and calcined. Further, a carrier using spherical alumina or the like instead of spherical silica, a carrier prepared by using tetraisopropyl orthotitanate or tetrabutyl orthotitanate instead of ethyl orthotitanate, and the like can be mentioned. Alternatively, it is also possible to use a method in which spherical silica is suspended in a titanium sulfate solution and titanium hydroxide is supported on the silica by adding an alkali such as aqueous ammonia. Carrier firing temperature is 300 to 1000
C., preferably 400 to 700.degree. When the firing temperature is low, crystallization of titania is insufficient and titanium elutes during the reaction. Further, if the calcination temperature is too high, the specific surface area of the carrier is remarkably reduced, which causes a problem that the catalytic activity is lowered.

The amount of the catalyst of the present invention used in the production of hydrogen peroxide is usually 1 gram or more per liter of the reaction medium, and it may be used in the form of slurry. As the reaction medium of the present invention, an aqueous solution prepared by adding an inorganic acid such as sulfuric acid, nitric acid or phosphoric acid and a halogen compound such as sodium bromide or sodium bromate is preferably used. The reaction conditions for hydrogen peroxide production using the platinum group catalyst of the present invention are usually a reaction pressure of 0.1 to 2 MPa and a reaction temperature of 0.
It is carried out under the condition of -50 ° C.

[0011]

The present invention will be described below in more detail with reference to Examples and Comparative Examples. The measurement of hydrogen peroxide concentration in the solution is
It was performed by a titration method using a sulfuric acid-potassium permanganate solution. The hydrogen selectivity was calculated by the following formula. Hydrogen selectivity (%) = [(amount of hydrogen peroxide produced by the reaction mol) / (theoretical amount of hydrogen peroxide calculated from the amount of hydrogen consumed)] × 100

Example 1 A catalyst was prepared by the following method. That is, 100 g of commercially available silica (manufactured by Fuji Silysia Chemical Ltd., CARiACT, average particle size: 50 microns) was suspended in 200 ml of ethanol, and the solution was suspended in a commercially available ethyl orthotitanate (Tokyo Chemical Industry Co., Ltd. 57.1 g was added and the mixture was stirred for 1 hour, then 40 ml of pure water was gradually added dropwise to precipitate titanium hydroxide by hydrolysis. By further heating with stirring and evaporation / drying, a silica-supported titanium hydroxide carrier supporting titanium hydroxide was obtained. The obtained carrier was calcined in an air stream at 700 ° C. for 3 hours to obtain a silica-supported titania carrier.

Next, the obtained silica-supported titania carrier 9
To a suspension obtained by suspending 5 g in 200 ml of water, 50 ml of hydrochloric acid in which 8.39 g of commercially available palladium chloride (manufactured by Ishifuku Metal Industry Co., Ltd.) was dissolved was added dropwise. After the addition of the palladium chloride solution was completed, 20 ml of 30% aqueous ammonia was gradually added dropwise to neutralize the suspension and adsorb palladium on the carrier. The catalyst obtained is filtered off, washed and dried in a drier 1
It was dried overnight at 10 ° C. After that, 40 in the air flow
It was calcined at 0 ° C. for 2 hours and then reduced in a hydrogen stream at 200 ° C. for 1 hour to obtain a catalyst. The following operation was performed as a reaction method for directly producing hydrogen peroxide from oxygen and hydrogen.

0.5 ml of sodium bromide was added to an autoclave with a cooling jacket made of SUS316 having an internal volume of 6 liters.
The suspension was suspended by adding 3 liters of an aqueous solution containing mmol / liter and 0.1 mol / liter of phosphoric acid and 120 g of the supported palladium catalyst prepared by the above-mentioned method. The autoclave was closed, air was introduced into the autoclave at 480 Nl / hr, and the pressure in the autoclave was increased by a pressure adjusting valve until it reached 0.9 MPa. While continuing the aeration of air, the reaction pressure was 0.9 MPa and the reaction temperature was 10 ° C.
The stirring was started at a speed of 1500 rpm. After the conditions were stabilized, 40 Nl / hr of hydrogen gas was aerated to start the reaction. The reaction solution was sampled every 30 minutes through a 10 micron sintered metal filter. The liquid was drained smoothly for each sampling, and the broken catalyst did not come out. After completion of the reaction for 6 hours, the hydrogen peroxide concentration was 5.0% by weight and the hydrogen selectivity was 59.2%.

Example 2 A catalyst was prepared in the same manner as in Example 1 except that a commercially available aluminum oxide (Neobead, manufactured by Mizusawa Chemical Co., Ltd.) was used in place of the commercially available silica at the time of preparing the catalyst, and the catalyst was prepared under the same conditions. The reaction was carried out. After completion of the reaction for 6 hours, the hydrogen peroxide concentration was 4.8% by weight and the hydrogen selectivity was 57.9%. The liquid was drained smoothly for each sampling, and the broken catalyst did not come out.

Example 3 A catalyst was prepared in the same manner as in Example 1 except that tetraisopropyl orthotitanate (manufactured by Tokyo Chemical Industry Co., Ltd.) was used in place of ethyl orthotitanate when preparing the catalyst. The reaction was carried out under the conditions. After the reaction for 6 hours, the hydrogen peroxide concentration was 5.0% by weight and the hydrogen selectivity was 5
It was 8.9%. The liquid was drained smoothly for each sampling, and the broken catalyst did not come out.

Example 4 A catalyst was prepared by the following method. That is, commercially available 2
To a solution prepared by adding 100 ml of pure water to 250 ml of 4% titanium sulfate solution (manufactured by Kanto Chemical Co., Inc.), commercially available silica (manufactured by Fuji Silysia Chemical Co., Ltd., CARiACT, average particle size 50)
Micron) 100 g was suspended. Commercially available 30% ammonia water (manufactured by Kanto Chemical Co., Inc.) was gradually added dropwise to this suspension to deposit titanium hydroxide on silica. The obtained carrier was separated by filtration, washed with pure water, and then calcined in an air stream at 700 ° C. for 3 hours to obtain a silica-supported titania carrier. Or later,
The same operation as in Example 1 was carried out to prepare a catalyst supporting palladium, and the reaction was carried out under the same conditions. After completion of the reaction for 6 hours, the hydrogen peroxide concentration was 4.6% by weight and the hydrogen selectivity was 55.9%. Although the fine powder of the catalyst was found to be mixed in the sampled drainage liquid, the drainage rate was not affected. Analysis by XRF revealed that the fines were titania.

Comparative Example 1 The reaction was performed in the same manner as in Example 1 except that 40 g of 5% Pd / titania powder (produced by NE Chemcat Co., Ltd., average particle size: 11 μm) was used as a catalyst. .
After completion of the reaction for 6 hours, the hydrogen peroxide concentration was 5.4% by weight and the hydrogen selectivity was 67.9%. Further, it was confirmed that the catalyst fine powder was mixed in the sampled drainage liquid. The filter was clogged and the drainage rate decreased.

Comparative Example 2 The reaction was carried out in the same manner as in Example 1 except that 80 g of 5% Pd / titania powder (produced by NE Chemcat Co., Ltd., average particle size 20 μm) was used as the catalyst. .
After completion of the reaction for 6 hours, the hydrogen peroxide concentration was 5.3% by weight and the hydrogen selectivity was 63.3%. Immediately after the start of the reaction, fine catalyst powder was found to be mixed in the sampled drainage liquid, and the filter was severely clogged just before the completion of the reaction and draining was difficult.

Comparative Example 3 The reaction was performed in the same manner as in Example 1 except that 120 g of 5% Pd / alumina powder (produced by NE Chemcat Co., Ltd., average particle size: 20 microns) was used as a catalyst. . After the reaction for 6 hours, the hydrogen peroxide concentration was 3.
It was 8% by weight and the hydrogen selectivity was 45.9%. The liquid was drained smoothly for each sampling, and the broken catalyst did not come out.

[0021]

By using the catalyst of the present invention in which titania and a platinum group metal are supported on an oxide carrier, a catalyst of a practical size can be prepared and a reaction medium under a low pressure is obtained. It was revealed that a high concentration of hydrogen peroxide can be selectively produced in an aqueous solution. Therefore, the present invention solves the problems of the conventional method and enables the production of hydrogen peroxide on an industrial scale.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naofumi Takagi 6-1, 1-1 Shinjuku, Katsushika-ku, Tokyo Mitsubishi Gas Chemical Co., Ltd. Tokyo Research Laboratory

Claims (9)

[Claims] 1. A method for producing hydrogen peroxide by catalytically reacting oxygen and hydrogen in a reaction medium, wherein a catalyst having titania and a platinum group metal supported on a carrier is used. Production method. 2. A method for producing hydrogen peroxide by catalytically reacting oxygen and hydrogen in a reaction medium, characterized in that a catalyst in which titania is supported on a carrier and a platinum group metal is further supported is used. Method for producing hydrogen peroxide. 3. The method for producing hydrogen peroxide according to claim 1 or 2, wherein titanium hydroxide obtained by hydrolyzing titanium alkoxide as a raw material is supported on the surface of the carrier, and then this is fired to form titania. 4. The method for producing hydrogen peroxide according to claim 3, wherein the firing temperature is 300 to 1000 ° C. 5. The method for producing hydrogen peroxide according to claim 1, wherein hydrogen and oxygen are catalytically reacted with a catalyst in a reaction medium at a reaction pressure of 0.1 to 2 MPa. 6. The platinum group metal is palladium.
Or the method for producing hydrogen peroxide described in 2. 7. The method for producing hydrogen peroxide according to claim 1, wherein the carrier is silica or alumina. 8. The method for producing hydrogen peroxide according to claim 1, wherein the reaction medium is an aqueous solution containing an acid and a halogen compound. 9. A catalyst for producing hydrogen peroxide by catalytically reacting oxygen and hydrogen in a reaction medium, wherein the carrier carries titania and a platinum group metal.