JP4709954B2 - Direct synthesis of hydrogen peroxide - Google Patents

Description

  The present invention relates to the direct synthesis of hydrogen peroxide, which produces hydrogen peroxide by directly reacting hydrogen and oxygen.

  Hydrogen peroxide has a strong oxidizing power and has a bleaching and sterilizing action, so it is used as a bleaching agent and a sterilizing agent for paper, pulp, fiber, processed fishery products and the like. In addition, hydrogen peroxide is differentiated from water and oxygen even when differentiated, so it is important from the viewpoint of green chemistry, and has attracted attention as an alternative material for chlorine bleach.

  Conventionally, hydrogen peroxide has been produced by an organic method, an anthraquinone method, an electrolytic method, and the like, and an anthraquinone method has been used as an industrial production method. However, the anthraquinone method has many drawbacks such as reduction of the anthraquinone medium, oxidation, extraction of the generated hydrogen peroxide, purification, concentration, etc., and the use of a large amount of energy makes the production cost very high. .

In view of the above problems, a method for synthesizing hydrogen peroxide by directly reacting hydrogen and oxygen has been studied. In this direct synthesis method, hydrogen and oxygen are reacted in the presence of a noble metal catalyst. Methods for using them to advance the reaction are known.
JP 63-156005 A JP-A-4-238802 JP-A-4-285003 JP-A-5-17106 Japanese Patent Laid-Open No. 5-43206 JP-A-9-301705

  In the direct synthesis method of hydrogen peroxide, the production efficiency that is comprehensively determined based on various factors such as the selectivity of the synthesis reaction and the production rate is important. In this regard, according to the conventional method, hydrogen peroxide can be produced to some extent, but the reaction is not allowed to proceed while satisfying the production efficiency to be judged including the reaction rate and the like. Some require high reaction pressure, and the current situation is that they do not reach a level that can be used for industrial production.

  The present inventors have found a method of using a noble metal colloid as a catalyst instead of the conventional method using a noble metal-supported catalyst as a method for directly synthesizing hydrogen peroxide with better production efficiency (Japanese Patent Application). 2004-090821). Here, the noble metal colloid means a dispersion in which a few to several hundred nanometers of noble metal fine particles insoluble in a solvent are dispersed and suspended in the solvent. According to the present inventors, it has been confirmed that the production rate and selectivity of the hydrogen peroxide production reaction can be improved by applying a noble metal colloid.

  In order to put the production method of hydrogen peroxide by direct synthesis into practical use, it is required to increase the production efficiency as much as possible. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an improved hydrogen peroxide production method by the present inventors, which shows higher production efficiency.

  Based on the above-described method using a noble metal colloid as a catalyst, the present inventors added a further noble metal salt to the catalyst solution containing the noble metal colloid to perform a reduction treatment, thereby performing a synthetic reaction with higher efficiency. The inventors have found that a catalyst solution that can be advanced can be obtained, and have arrived at the present invention.

  That is, according to the present invention, in the direct synthesis method of hydrogen peroxide in which hydrogen and oxygen are reacted, the second noble metal salt is added to the solvent in which the first noble metal colloidal particles are dispersed, and then the reduction treatment is performed. This is a direct synthesis method of hydrogen peroxide, characterized in that a solution is produced and hydrogen and oxygen are allowed to react with the catalyst solution.

  In the present invention, when the second noble metal salt is added to the first noble metal colloid solution for reduction treatment, the second noble metal is present as noble metal particles in the catalyst solution. The second noble metal particles are considered to be dispersed alone in the catalyst solution or taken into the first noble metal colloid to form a noble metal alloy colloid. In the present invention, it is not certain what the state of the catalyst solution after the reduction treatment is. However, the additional dispersion of the noble metal particles or the formation of the noble metal alloy colloid described above improves the reaction promoting action of the catalyst solution. An increase in hydrogen oxide production efficiency is expected.

  Hereinafter, the present invention will be described in detail. The significance of the noble metal colloid in the present invention is as described above. The noble metal composing the first noble metal colloidal particles is a noble metal such as platinum, palladium, silver, gold, ruthenium, rhodium, iridium, or osmium, with palladium and platinum being preferred. The particle diameter of the noble metal particles constituting the colloid is preferably 1 to 10 nm. Even if a colloid having a particle size outside these ranges is applied, the synthesis reaction occurs, but the colloid in the region of 1 to 10 nm is particularly high in activity.

  The noble metal colloid generally contains a compound called a protective agent. A protective agent is a compound that binds or adsorbs chemically or physically around colloidal particles in a colloidal solution, and suppresses aggregation of colloidal particles and controls the particle size distribution within an appropriate range to stabilize it. Say. By including the protective agent, the state in which the colloidal particles having a fine particle diameter are suspended can be maintained, and the synthesis reaction of hydrogen peroxide can be made homogeneous. The protective agent is not particularly limited as long as it is an organic compound that can be chemically or physically bound to and adsorbed on colloidal particles, and is not limited, and polyvinylpyrrolidone (hereinafter referred to as PVP), polyethyleneimine (hereinafter referred to as PVP). , PEI), polyacrylic acid (hereinafter referred to as PAA), carboxymethyl cellulose (hereinafter referred to as CMC), polyvinyl alcohol (hereinafter referred to as PVA) citric acid, tartaric acid, alginic acid, polyphosphoric acid, poly (N- Organic compounds such as carboxymethyl) allylamine, poly (N, N-dicarboxymethyl) allylamine, poly (N-carboxymethyl) ethyleneimine are applicable. Particularly preferred protective agents in the invention are PVP, PAA, CMC, PVA, citric acid, tartaric acid, alginic acid and polyphosphoric acid, particularly preferably PVP.

  In the production of the first noble metal colloid solution used in the present invention, first, an organic compound serving as a protective agent and a metal salt solution of the first noble metal serving as colloid particles are mixed, and a reducing agent is added thereto. Can be manufactured. At this time, the metal ions in the metal salt solution are reduced and the protective agent is adsorbed on the cluster particles to form a colloidal solution. When the protective agent itself is an organic compound having a reducing action, it is not necessary to add a reducing agent.

On the other hand, the second noble metal added to the first noble metal colloid solution is a noble metal different from the first noble metal. As a preferable combination, the first noble metal is palladium, and the second noble metal is platinum. It will be. Preferred noble metal salts are noble metal hydrochlorides or chlorides, such as chloroplatinate (H ₂ PtCl ₆ ), chloroaurate (HAuCl ₄ ), rhodium chloride, ruthenium chloride, iridium chloride and the like. It is done.

  The reduction treatment after the addition of the second noble metal salt is usually by addition of a reducing agent, but is preferably by introduction of hydrogen gas. This is to prevent a residue from being generated in the catalyst solution. When hydrochloric acid salt or chloride is applied as the noble metal salt, chlorine ions remain in the catalyst solution after the reduction treatment, but the chlorine ions do not adversely affect the hydrogen peroxide synthesis reaction. It has been confirmed.

  Moreover, it is preferable that the ratio of the first noble metal and the second noble metal in the catalyst solution be 3: 1 to 9: 1 by mass ratio. As described above, the production efficiency of hydrogen peroxide is related not only to the amount of hydrogen peroxide generated, but also to the production rate and selectivity, but the ratio of the first noble metal to the second noble metal is within the above range. This is because each factor is balanced. In addition, it is preferable that the density | concentration of all the noble metals in a catalyst solution shall be 0.0001 to 0.01 weight%.

  Since the synthesis reaction of hydrogen peroxide is a reaction between (hydrogen) gas and (oxygen) gas, in order for the noble metal colloid solution to coexist in the reaction system, the mixed gas of both is put into the noble metal colloid solution in the reaction vessel. A method of bubbling is common.

  In the method according to the present invention, it is preferable to react by adding an inorganic acid to the reaction system. Thereby, the selectivity of a hydrogen peroxide synthesis reaction can be improved and manufacturing efficiency can be ensured. The amount of inorganic acid added is preferably 0.001 to 1% by weight based on the catalyst solution. And as this inorganic acid, application of hydrogen bromide or hydrogen sulfate hydrobromide is preferable, and it is preferable to add either or both of them.

As for the reaction conditions during the synthesis reaction, the reaction temperature is preferably in the range of 0 to 100 ° C, particularly 20 to 70 ° C. The pressure of the reaction is not particularly limited, is preferably from atmospheric pressure to 100 kg / cm ^2, particularly suitably atmospheric pressure to 20 kg / cm ^2. The reaction time (contact time between the raw material gas and the colloidal particles) is usually 0.1 to 100 hours, preferably 0.5 to 10 hours. This reaction can be carried out either batchwise or continuously. The flow rates of the raw material hydrogen gas and oxygen gas are preferably such that the range of explosion is avoided and oxygen is excessive with respect to hydrogen.

  According to the present invention, it is possible to more efficiently produce hydrogen peroxide by a direct synthesis method. The present invention is a relatively simple process, can produce hydrogen peroxide regardless of special conditions, and can be improved in its industrial production process.

Example 1
To a dinitrodiammine palladium solution corresponding to 0.1 g of Pd, 1.0 g of PVP and 100 mL of water were added and heated to reflux, and 50 mL of ethanol was added dropwise as a reducing agent to reduce palladium. Then, the solution was concentrated to obtain a Pd-PVP colloid having a palladium concentration of 4 wt%. The palladium colloid particle diameter was 2 nm, and the solution was a black viscous liquid. And this Pd-PVP colloid was diluted 100 times with ion-exchanged water to prepare 0.04 wt%. At the same time, 1 g of chloroplatinate (hexachloroplatinic acid (IV) hexahydrate) was dissolved in 1 L of water. A 3N HBr solution was also prepared.

  Hydrogen peroxide was directly synthesized using the Pd-PVP colloid solution and the chloroplatinate solution prepared above. For the synthesis, a direct synthesizer shown in FIG. 1 was used. For the synthesis of hydrogen peroxide, first, 10 mL of the HBr solution (final concentration 0.1 N) manufactured in the reactor 100, the noble metal salt solution, and the Pd-PVP colloid solution were added in this order, and finally the total amount was made 300 mL with ion-exchanged water. . The Pd-PVP colloid and the noble metal salt were added while adjusting the ratio so that the total metal amount was 2.5 mg.

  Then, reduction was performed by flowing hydrogen into the reactor 100 from the hydrogen supply port 10 at 25 cc / min for 1 hour. The reaction temperature at this time is 303K, and the stirring speed is 650 rpm. A catalyst solution was produced in the reactor 100 by this reduction treatment. In the reduction, the gas phase portion was replaced by flowing nitrogen from the nitrogen inlet 30 at 50 cc / min for 20 minutes.

  In the hydrogen peroxide synthesis reaction, hydrogen and oxygen as reaction gases and nitrogen as a balance gas were introduced from the respective supply ports 10, 20, and 30. The supply amount of each gas was 7 cc / min for hydrogen, 31 cc / min for oxygen, and 15 cc / min for nitrogen. The reaction conditions were a normal pressure, a reaction temperature of 303K, and a stirring speed of 1200 rpm. Further, during the reaction, sampling was appropriately performed from the reactor 100, and the reaction gas composition was analyzed by the gas chromatography with TCD 102.

Then, 1 ml of the synthesized hydrogen peroxide was sampled with a syringe every 30 minutes and quantified by absorptiometry. Hydrogen peroxide was quantified by an absorptiometric method using absorption of 410 nm of hydrogen peroxide-titanium sulfate complex. As the color developing solution, a solution obtained by adding 14 mL of concentrated sulfuric acid to 16 mL of 30% titanium sulfate and diluting to 100 mL with ion-exchanged water was used. For the analysis, a solution obtained by diluting 4 mL of the color developing solution and 1 mL of the reaction solution to 25 mL was used, and the amount of the reaction solution was measured and determined.

The results of the direct synthesis test were evaluated based on four numerical values: hydrogen peroxide concentration, hydrogen reaction rate (R ₀ ), production selectivity (S ₀ ), and hydrogen peroxide decomposition rate coefficient (k _d ). The results are shown in Table 1. For comparison, the results when a Pd—PVP colloid to which no chloroplatinate was added were used as a catalyst solution were also shown.

In the evaluation of each numerical value, it is preferable that the hydrogen peroxide concentration, R ₀ and S ₀ are high. On the other hand, k _d indicates the degree to which the decomposition reaction of hydrogen peroxide generated in the synthesis reaction occurs, so that a large value indicates that a saturation point is likely to occur in the synthesis reaction. preferable. From this point of view, the results in Table 1 show that the use of a colloid to which chloroplatinate was added improved the hydrogen peroxide concentration and the reaction rate, although the production selectivity S ₀ was reduced. Was confirmed. In particular, it can be seen that when the ratio of palladium to platinum is 3: 1 to 9: 1, efficient synthesis reaction progress can be seen from the balance of each parameter.

Example 2
Here, a catalyst solution in which various noble metal salts were added to the Pd-PVP colloid produced in Example 1 was produced, and a hydrogen peroxide synthesis reaction test was conducted. The precious metal salts used here were gold chloride (III) acid tetrahydrate, rhodium chloride (III) trihydrate, and iridium chloride (III) trihydrate (each 1 g), which was the same as in Example 1. A noble metal salt solution was used.

  Then, a hydrogen peroxide synthesis reaction test was performed and evaluated using the same apparatus and procedure as in Example 1. The ratio of palladium to platinum was 3: 1. The test results at this time are shown in Table 2.

  From Table 2, it can be seen that when a catalyst solution produced by addition / reduction of a noble metal hydrogen chloride salt is used, the production efficiency is improved as compared with the case of a colloid alone from a comprehensive viewpoint.

The figure which shows the structure of the synthetic | combination apparatus used by this embodiment.

Explanation of symbols

10 Hydrogen 20 Oxygen 30 Nitrogen 100 Reactor 101 Colloidal solution 102 Gas chromatography

Claims (8)

In the direct synthesis method of hydrogen peroxide by reacting hydrogen and oxygen,
A catalyst solution is prepared by adding a second noble metal salt to a solvent in which the colloidal particles of the first noble metal are dispersed and then reducing the mixture;
A method for directly synthesizing hydrogen peroxide, wherein hydrogen and oxygen are allowed to react with the catalyst solution. The method for directly synthesizing hydrogen peroxide according to claim 1, wherein the salt of the second noble metal is a hydrochloride or a chloride. The method for directly synthesizing hydrogen peroxide according to claim 1 or 2, wherein the first noble metal is palladium and the second noble metal is platinum. The direct synthesis of hydrogen peroxide according to any one of claims 1 to 3, wherein the abundance ratio of the first noble metal and the second noble metal in the catalyst solution is 3: 1 to 9: 1 by mass ratio. Law. The method for directly synthesizing hydrogen peroxide according to any one of claims 1 to 4, wherein the protective agent for the noble metal colloid is polyvinylpyrrolidone. The method for directly synthesizing hydrogen peroxide according to any one of claims 1 to 5, wherein an inorganic acid is added to the reaction system for reaction. The method for directly synthesizing hydrogen peroxide according to claim 6, wherein the amount of the inorganic acid added is 0.001 to 1% by weight based on the noble metal colloid solution. The method for directly synthesizing hydrogen peroxide according to claim 6 or 7, wherein hydrogen bromide and / or sulfuric acid is added as an inorganic acid.

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