JPH082904A - Production of hydrogen peroxide - Google Patents

Abstract

PURPOSE:To provide an industrially advantageous method for production of hydrogen peroxide, capable of producing high-concentration hydrogen peroxide at low cost by reducing the amount of used pure oxygen which is relatively expensive. CONSTITUTION:This is a method for producing hydrogen peroxide by catalytically reacting hydrogen with oxygen in the presence of a catalyst in an aqueous medium. In this method, the reaction is carried out while controlling the concentration of oxygen in feed gas to 10 to 30vol.%, 20 to 50vol.% and 30 to 95vol.% in the case the concentration of hydrogen peroxide in the reactor is respectively <5wt.%, <10wt.% and >=10wt.%. These conditions enable reduction of the amount of used pure oxygen while keeping the selectivity of hydrogen high.

Description

Detailed Description of the Invention

[0001]

This invention relates to an improved process for producing hydrogen peroxide by catalytically reacting oxygen and hydrogen with a catalyst in a reaction medium. More specifically, it relates to a method for economically and efficiently producing hydrogen peroxide by controlling the oxygen concentration in the feed gas in accordance with the concentration of hydrogen peroxide existing in the reactor.

[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. As a problem of this method, reduction,
Since many processes such as oxidation, water extraction / separation, purification, concentration, etc. are required and the process is complicated, the equipment cost and the operating cost are high. Further, there are problems such as loss due to deterioration of alkyl anthraquinone and deterioration of the reduction catalyst.

In order to solve these problems, production methods other than the above-mentioned production methods have been tried. One of them is to use a catalyst in the reaction medium to directly peroxidize oxygen and hydrogen. There is a method of producing hydrogen. A method for producing hydrogen peroxide from oxygen and hydrogen using a platinum group metal as a catalyst has already been proposed, and it has been shown that hydrogen peroxide of a certain high concentration is produced. (Japanese Patent Publication No. 56-47
No. 121, Japanese Patent Publication No. 55-18646, Japanese Patent Fair 1-23
401, JP-A-63-156005, US51942.
42, US Pat. No. 4,336,239).

These patents disclose a method for producing an aqueous solution of hydrogen peroxide by carrying out a reaction by using hydrogen as a reaction gas, which is a gas composed of a mixture of oxygen and nitrogen such as pure oxygen or air. In addition, Japanese Examined Japanese Patent Sho 56-4
Japanese Patent No. 7121 defines the ratio of hydrogen and oxygen,
According to this, the hydrogen partial pressure in the reaction gas phase is kept at 0.5 atm or more, the oxygen partial pressure is kept at 1.0 atm or more, and the ratio of the oxygen partial pressure to the hydrogen partial pressure is kept at 1.5 to 20. Disclosed is a method for producing hydrogen peroxide with high efficiency.

However, in the method of simply using a mixed gas having a high oxygen partial pressure, the yield of hydrogen peroxide does not increase in spite of using pure oxygen in a large amount in order to increase the oxygen partial pressure. In general, pure oxygen is relatively expensive, and there has been a need for a method of solving the economic problems caused by the cost burden of pure oxygen used for increasing the oxygen concentration in the feed gas.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing hydrogen peroxide, which makes it possible to obtain a high concentration of hydrogen peroxide economically. In particular, it is an object of the invention to provide an industrially advantageous method for producing hydrogen peroxide, which can reduce the amount of relatively expensive pure oxygen used.

[0007]

[Means for Solving the Problems] In the method for catalytically producing hydrogen peroxide from oxygen and hydrogen using a catalyst, the present inventors have made it possible to inexpensively produce a highly concentrated hydrogen peroxide solution with higher hydrogen selectivity. As a result of continuing the examination of the production method obtained in, the relationship between the concentration of hydrogen peroxide existing in the reactor and the oxygen concentration in the feed gas was found to have a close correlation with the hydrogen selectivity. The inventors have found that the object can be achieved by controlling the oxygen concentration according to the hydrogen peroxide concentration in the reactor, and have completed the present invention.

That is, according to the present invention, in a method for producing hydrogen peroxide by catalytically reacting oxygen and hydrogen in an aqueous medium, the oxygen concentration in the feed gas is adjusted according to the hydrogen peroxide concentration in the reactor. Controlling, that is, when the concentration of hydrogen peroxide existing in the reactor is high, the oxygen concentration in the feed gas is controlled to be high, and when the hydrogen peroxide concentration is low, the oxygen concentration in the feed gas is controlled to be low. By doing so, it relates to a method for economically producing hydrogen peroxide.

In the method for producing hydrogen peroxide by catalytically reacting oxygen and hydrogen in a reaction medium, the hydrogen selectivity is represented by the formula (1).

Formula (1): Hydrogen selectivity (%) = [(molar amount of hydrogen peroxide produced by reaction) / (theoretical molar amount of hydrogen peroxide calculated from the amount of hydrogen consumed)] × The present inventors have found that the hydrogen selectivity obtained by the equation (1) is greatly influenced by the oxygen concentration in the supply gas, and that the higher the oxygen concentration, the higher the hydrogen selectivity tends to be. That is, by increasing the oxygen concentration in the supply gas, the hydrogen selectivity is improved and the hydrogen peroxide acquisition amount is increased.

The present inventors further studied, and the effect of oxygen concentration on hydrogen selectivity was relatively small when the hydrogen peroxide concentration was low, but as the hydrogen peroxide concentration increased,
The present invention has been completed by finding a tendency that the influence of oxygen concentration on hydrogen selectivity increases.

According to the method of the present invention, the oxygen concentration in the feed gas is controlled to be low in the low concentration region of hydrogen peroxide, which is relatively less affected by the oxygen concentration, and the high concentration of hydrogen peroxide, which is greatly affected by the oxygen concentration, is increased. In the region, by controlling the oxygen concentration in the supply gas to be high, it becomes possible to reduce the amount of pure oxygen used and to carry out the reaction with a high hydrogen selectivity.

In the present invention, the oxygen concentration in the feed gas is 10 to 30% by volume, preferably 10 to 30% by volume in the region where the hydrogen peroxide concentration in the reactor is 0 to less than 5% by weight. 15 to 25% by volume, and in the region where the hydrogen peroxide concentration is 5% by weight or more and less than 10% by weight, the oxygen concentration in the supply gas is controlled to 20 to 50% by volume, preferably 25 to 35% by volume. , And the hydrogen peroxide concentration is 1
In the range of 0% by weight or more, the oxygen concentration in the supply gas is controlled to 30 to 95% by volume, preferably 35 to 60% by volume.

In order to control the oxygen concentration in the feed gas within the above range, an appropriate amount of an inert gas that does not hinder the reaction between oxygen and hydrogen is present in the feed gas. . Examples of the inert gas include nitrogen and argon. Pure oxygen, air, oxygen-enriched air, or the like is used as the oxygen source. It is a preferred method to mix pure oxygen or oxygen-enriched air with the air in order to control the oxygen concentration in the feed gas within the above range.

As described above, in the method for producing hydrogen peroxide by catalytically reacting oxygen and hydrogen in the reaction medium, the hydrogen selectivity is improved by using a feed gas containing a higher concentration of oxygen. Therefore, it is needless to say that it is not impossible to use the feed gas containing a high concentration of oxygen gas even in the region where the concentration of hydrogen peroxide existing in the reactor is low.

However, according to the present invention, it is possible to select an efficient oxygen concentration according to the concentration of hydrogen peroxide existing in the reactor without using an unnecessarily high concentration of oxygen. The benefits provided are extremely large in terms of efficiency and economy. Selecting an oxygen concentration outside the range specified in the present invention is disadvantageous in terms of efficiency and economy. The production of hydrogen peroxide according to the present invention is usually carried out at a reaction pressure of 3 kg / cm ² ·
G to 150 kg / cm ² · G, and the reaction temperature is 0 ° C to 50 ° C. The hydrogen concentration is 1 to 20% by volume.

The catalyst used in the present invention is preferably a platinum group metal, particularly preferably palladium or platinum. The shape of the catalyst is not particularly limited, and it may be in the form of pellet or powder. In addition, a general catalyst carrier,
For example, silica, titania, alumina, magnesia, zirconia, ceria, zeolite, activated carbon, or the like may be used, and a platinum group metal such as palladium or platinum may be supported on these carriers.

The amount of catalyst used is usually 1 per liter.
More than a gram is used. It is also possible to add a large amount of a catalyst to the reaction medium and carry out the reaction in a slurry state. In the present invention, since a high concentration of hydrogen peroxide water is generated, it is possible to add a stabilizer of hydrogen peroxide to water as a reaction medium for the purpose of suppressing decomposition. As the stabilizer for hydrogen peroxide, a known water-soluble stabilizer can be used.

Specific examples of the stabilizer include aminotri (methylenephosphonic acid), 1-hydroxyethylidene-1,
Examples thereof include 1-diphosphonic acid, ethylenediaminetetra (methylenephosphonic acid), sodium salts thereof, phosphoric acid, sulfuric acid, nitric acid and sodium pyrophosphate. The amount of the stabilizer used varies depending on the kind of the stabilizer and the concentration of hydrogen peroxide solution, but normally, the concentration in water is 0.1 wt% or less, preferably 0.1 ppm or more 10
It is 0 ppm or less.

An embodiment of the present invention will be described. For example,
In the case of a batch reactor, the oxygen concentration in the feed gas is adjusted according to the hydrogen peroxide concentration in the reactor, which increases with the passage of reaction time. That is, in the low concentration region where the hydrogen peroxide concentration in the initial stage of the reaction is less than 5% by weight, air is used as an oxygen source, and the oxygen content in the supply gas is changed with time as the hydrogen peroxide concentration increases with the progress of the reaction. The oxygen concentration is increased to gradually raise the oxygen concentration to the above-mentioned concentration.

Further, in the case of a flow apparatus having two or more reactors and allowing the reaction medium to sequentially pass through each reactor, the residence time of the reaction medium in each reactor should be adjusted. The concentration of hydrogen peroxide in each reactor is
From the reactor, adjust the concentration so that it becomes higher while maintaining an appropriate concentration. On the other hand, the oxygen concentration in the gas supplied to each reactor is gradually increased from the first reactor.

A preferred method therefor is to supply hydrogen to each reactor, simultaneously in parallel to supply a feed gas having a high oxygen concentration to the final reactor, and to supply off-gas from the final reactor to the reactor of the preceding stage. The off-gas from each reactor is sequentially supplied to the reactor at the preceding stage, so that the off-gas sequentially passes through each reactor toward the first reactor in the opposite direction to the flow of the reaction medium. To introduce.

In this case, the oxygen gas in the feed gas is consumed when passing through each reactor, and the oxygen concentration in the gas gradually decreases toward the first reactor. That is, by making the flow of the reaction medium and the supply gas countercurrent, the reaction by the gas with high oxygen concentration in the region where the hydrogen peroxide concentration is high in the reactor,
Further, in the region where the hydrogen peroxide concentration is low, the reaction with the gas having a low oxygen concentration is performed, and the method according to the present invention can be carried out.

In addition to the above method, there is no limitation on the form and shape as long as it is a reaction type in which the oxygen concentration in the supply gas can be controlled according to the hydrogen peroxide concentration in the reactor. As the type of the reaction apparatus for carrying out the present invention, a stirred reactor is generally adopted, but if a power for sufficiently dispersing the aqueous medium and the catalyst can be given, a bubble column or a fluidized bed reactor can be used. A reactor or the like can be used without limitation.

[0024]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. In the Examples and Comparative Examples, the hydrogen reaction amount and the oxygen concentration in the supply gas were determined by analyzing the reactor outlet gas composition and the reactor inlet gas composition by a gas chromatograph. The hydrogen peroxide concentration in the reaction medium was measured by a titration method using a sulfuric acid-acidic potassium permanganate solution.

Example 1 An autoclave with a cooling jacket made of SUS316 and having an internal volume of 6 liters was charged with 0.5 mmol / mol of sodium bromate.
Liter, 3000 ml of an aqueous solution containing 0.1 mol / liter of sulfuric acid, and N.V. as a catalyst. 10 g of a 5 wt% Pd / TiO ₂ catalyst manufactured by E Chemcat Corporation was added and suspended. Close the autoclave and let air 720Nl
The pressure of the autoclave was increased to 9 Kg / cm ² · G by the pressure control valve. While continuing the ventilation of air, the reaction pressure is 9K
g / cm ² · G, keep reaction temperature at 25 ° C, 1500r
Stirring was started at a speed of pm.

After the conditions are stabilized, hydrogen gas 60 Nl / h
r and a mixed gas of air and pure oxygen (720 Nl / hr) were simultaneously aerated to start the reaction. The ratio of both in the mixed gas of air and pure oxygen is 720: until 2.5 hours after the start of the reaction.
0 (oxygen concentration in supply gas 19.4% by volume), 2.5-
4.5 hours 663: 57 (25.2% by volume), 4.
5 to 6.5 hours 615: 105 (30.0% by volume)
The oxygen concentration in the supply gas was gradually increased.

The concentration of hydrogen peroxide in each reaction time is 0 to 4.52% by weight up to 2.5 hours after the start of the reaction, and 4.52 to 7.20% by weight for 2.5 to 4.5 hours. At the end of the reaction for 6.5 hours, the hydrogen peroxide concentration was 9.57% by weight, and the hydrogen reaction amount was 14.8 mol in total. The amount of pure oxygen added to the air by the end of the reaction to increase the oxygen concentration in the feed gas was 324 Nl, and the pure oxygen used to produce 1 g of hydrogen peroxide was 1.13 Nl / gH _{2 in} total. It was O ₂ . The hydrogen selectivity over the entire reaction time (6.5 hours) was 57%.

Comparative Example 1 Hydrogen flow rate is 60 Nl / hr, and air flow rate is 615 Nl / h.
r, the pure oxygen flow rate was 105 Nl / hr, the same reaction as in Example 1 was performed except that the oxygen concentration in the supply gas was fixed at 30% by volume and the reaction was performed for 6.5 hours without changing the oxygen concentration. went. After completion of the reaction for 6.5 hours, the hydrogen peroxide concentration was 9.95% by weight, and the total hydrogen reaction amount was 14.6 mol. The amount of pure oxygen added to the air by the end of the reaction is 683 Nl.
The pure oxygen used to generate 1 g of hydrogen peroxide was 2.29 Nl / g H ₂ O ₂ in total. The hydrogen selectivity was 60% over the entire reaction time (6.5 hours).

As is clear from the above, as compared with Example 1 in which the reaction is carried out by changing the oxygen concentration in the feed gas according to the hydrogen peroxide concentration, hydrogen is produced when the reaction is carried out with the oxygen concentration fixed. Although the selectivities were almost the same, the amount of pure oxygen used was more than doubled.

Comparative Example 2 Pure air was not used but only air was used as an oxygen source. The hydrogen flow rate was 60 Nl / hr and the air flow rate was 720 Nl / hr.
The reaction was carried out at 6.5 with the oxygen concentration in the feed gas fixed at 19% by volume.
The same reaction as in Comparative Example 1 was carried out except that the reaction was carried out for a time. 6.
After completion of the reaction for 5 hours, the hydrogen reaction amount was 14.7 mol in total, but the hydrogen peroxide concentration was only 7.88% by weight. The hydrogen selectivity over the entire reaction time (6.5 hours) was 47%.

Comparative Example 3 Only pure air was used as the oxygen source without using pure oxygen, the hydrogen flow rate was 60 Nl / hr, and the air flow rate was 720 Nl / hr.
The same reaction as in Comparative Example 1 was carried out except that the oxygen concentration in the feed gas was fixed at 19% by volume and the reaction was carried out for 9 hours. After the completion of the reaction for 9 hours, the hydrogen peroxide concentration in water increased to 9.57% by weight, but the total hydrogen reaction amount was 20.2 mol, and the hydrogen selectivity over the entire reaction time decreased to 42%. .

Example 2 Using an autoclave 3 units equipped with a stirrer made of SUS316 having an internal volume of 6 liters and a cooling jacket, the reaction medium and the reaction gas were connected so as to sequentially pass in the respective reactors in countercurrent. did. 0.5 mmol / l sodium bromate and 0.1 mol / sulfuric acid were added to each reactor.
3000 ml of an aqueous solution containing liter and N. 10 g of a 5 wt% Pd-supporting titania catalyst manufactured by E-Chem Cat Co., Ltd. was added and suspended. Close the autoclave, air 615 Nl / hr and pure oxygen 105 Nl / h
r was introduced into the bottom of the third reactor, the gas discharged from the third reactor was introduced into the bottom of the second reactor, and the gas discharged from the second reactor was introduced into the bottom of the first reactor. The pressure in the first reactor was increased to 9.0 Kg / cm ² · G by the pressure control valve installed in the gas line at the outlet of the first reactor. Correspondingly, the pressure in the second and third reactors is 9.1K each.
It was g / cm ² · G and 9.2 Kg / cm ² · G.

An aqueous solution containing 0.5 mmol / liter of sodium bromate and 0.1 mol / liter of sulfuric acid was used.
Introduced into the first reactor at 350 ml / hr,
The reaction liquid was extracted through a filter so that the liquid amount in the reactor was maintained at 3000 ml, and the extracted reaction liquid was introduced into the second reactor using a pump. Similarly, in the second reactor, the reaction liquid was extracted through a filter so that the liquid amount became 3000 ml, and the reaction liquid was introduced into the third reactor. The third reactor also has a liquid volume of 3000.
The reaction solution was withdrawn so that the volume became milliliter.

While continuing the aeration of air and pure oxygen and the introduction of the aqueous solution, the pressure in the first reactor was adjusted to 9 Kg / cm ² · G.
The temperature of each reactor was kept at 25 ° C., the liquid volume of each reactor was kept at 3000 ml, and stirring was started at 1500 rpm. After the conditions were stabilized, hydrogen gas was added to each reactor at 60 Nl.
The reaction was initiated by aeration at / hr. 18 hours after the start of the reaction, the hydrogen peroxide concentration in each reactor reached a steady state.

In the steady state, the hydrogen peroxide concentration in the reaction liquid flowing out from the outlet of the first reactor is 3.94% by weight,
The oxygen concentration in the mixed gas introduced into the reactor was 21.5% by volume, and in the second reactor was 7.00% by weight, respectively.
26.1% by volume, 9.2 in each third reactor
It was 4% by weight and 30.0% by volume. The amount of pure oxygen used during the entire reaction time was 105 Nl / hr, and the total amount of pure oxygen used to generate 1 g of hydrogen peroxide was 0.84.
Was Nl / gH ₂ O _2. The hydrogen selectivity of the entire three reactors was 49%.

Comparative Example 4 The same reaction as in Example 2 was carried out except that the reaction gas was individually introduced into each reactor and the gas discharged from each reactor was directly discharged to the outside of the system without reuse. The ventilation volume of each gas is
Air 615 Nl / hr, pure oxygen 105 Nl / hr, and hydrogen 60 Nl / hr were used for each container. 16 hours after the start of the reaction, the hydrogen peroxide concentration in each reactor reached a steady state. In the steady state, the hydrogen peroxide concentration in the reaction liquid flowing out from the outlet of the first reactor was 4.01% by weight, the oxygen concentration in the mixed gas introduced into the first reactor was 30.0% by volume, and the second reaction In the container, 7.02% by weight, 3
0.0% by volume, 9.24 each in the third reactor
% By weight, 30.0% by volume.

The amount of pure oxygen used throughout the reaction is 315 N
1 / hr and the total amount of pure oxygen used to produce 1 g of hydrogen peroxide was 2.45 Nl / g H ₂ O ₂ . The total hydrogen selectivity of all three reactors was 54%. As is clear from the above, the amount of pure oxygen used was nearly three times that of Example 2 in which the reaction gas was passed countercurrently to the reaction medium in each reactor.

[0038]

According to the present invention, in a method for producing hydrogen peroxide by catalytically reacting oxygen and hydrogen with a catalyst in an aqueous medium, in a supply gas depending on the hydrogen peroxide concentration in the reactor. By controlling the oxygen concentration of, the use amount of pure oxygen can be reduced without causing a significant decrease in hydrogen selectivity. As a result, it becomes possible to economically produce a high concentration of hydrogen peroxide. Particularly, since relatively expensive pure oxygen is efficiently used, an industrially advantageous method for producing hydrogen peroxide is provided.

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[Procedure amendment]

[Submission date] September 29, 1994

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[Name of item to be corrected] Claim 1

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The amount of catalyst used is usually 1 per liter.
More than a gram is used. It is also possible to add a large amount of a catalyst to the reaction medium and carry out the reaction in a slurry state. In order to increase the selectivity of the hydrogen peroxide generating reaction, it is preferable to use an aqueous solution containing halogen ions and / or an acid as the aqueous medium. In the present invention, since a high-concentration hydrogen peroxide solution is produced, it is possible to add a stabilizer for hydrogen peroxide to water as a reaction medium for the purpose of suppressing decomposition of hydrogen peroxide. As the stabilizer for hydrogen peroxide, a known water-soluble stabilizer can be used.

Front page continued (72) Inventor Ken Tomita 6-1-1 Shinjuku, Katsushika-ku, Tokyo Mitsubishi Gas Chemical Co., Ltd. Tokyo Research Laboratory

Claims (5)

[Claims] 1. A method for producing hydrogen peroxide by reacting oxygen and hydrogen with a catalyst in an aqueous medium in a catalytic manner, wherein the hydrogen peroxide concentration in the reactor is less than 5% by weight. When the oxygen concentration is 10 to 30% by volume and the hydrogen peroxide concentration is 5% by weight or more and less than 10% by weight, the oxygen concentration in the supply gas is 2
The method for producing hydrogen peroxide according to claim 1, wherein the oxygen concentration in the supply gas is 0 to 50% by volume and the oxygen concentration in the supply gas is 30 to 95% by volume when the hydrogen peroxide concentration is 10% by weight or more. 2. The method for producing hydrogen peroxide according to claim 1, wherein the catalyst is a platinum group catalyst. 3. The method for producing hydrogen peroxide according to claim 1, wherein the aqueous medium is an aqueous solution containing halogen ions and / or acids. 4. The method for producing hydrogen peroxide according to claim 1, wherein the aqueous medium is an aqueous solution containing a stabilizer for hydrogen peroxide. 5. Oxygen and hydrogen in the presence or absence of an inert gas in an aqueous medium in the presence of a catalyst at a reaction temperature of 0 ° C. to 5 ° C.
0 ° C, reaction pressure 3 kg / cm ² · G to 150 kg / cm ²
The method for producing hydrogen peroxide according to claim 1, wherein the reaction is carried out with G.