JPS61186208A - Decomposition of hydrogen perioxide - Google Patents

Abstract

PURPOSE:A substance which is capable of decomposing hydrogen peroxide and of binding oxygen with hydrogen is used as a catalyst and hydrogen is fed and brought into contact with hydrogen peroxide in the presence of the substance to effect continuous decomposition of hydrogen peroxide with a high level of catalyst activity constantly maintained. CONSTITUTION:In the process where hydrogen peroxide is decomposed by bringing a hydrogen perioxide aqueous solution into contact with a catalyst, a substance which is capable of decomposing hydrogen peroxide and of binding oxygen with hydrogen is used as a catalyst and hydrogen is fed to the catalyst. Hydrogen may be fed, only when the catalyst lowers its activity, however, the feed may be constantly continued, while the decomposition is effected. The selection appropriately depends on reaction conditions. Hydrogen is brought into contact with the catalyst as such or in a diluted mixture with an inert gas.

Description

DETAILED DESCRIPTION OF THE INVENTION (Objects of the Invention) The present invention relates to a method for decomposing hydrogen peroxide, and more particularly to a method for continuously decomposing hydrogen peroxide by using a catalyst and always maintaining a high level of catalytic activity.

(Prior art) After hydrogen peroxide decomposes, it produces harmless oxygen and water.
Its oxidizing power is widely used in chemistry, medicine, paper manufacturing, food, etc.

This decomposition of hydrogen peroxide usually uses catalysts, which include metals such as platinum and palladium, manganese,
Oxides of cobalt, copper, silver, etc. are widely known.

When hydrogen peroxide is decomposed using these catalysts,
The activity of the catalyst gradually decreases over time. Therefore, when the activity decreases to a certain value, the decomposition reaction is stopped and the catalyst is replaced with a new one, and the catalyst whose activity has decreased is reactivated by appropriate means and reused. In the case of actual operation, this results in a decrease in the operating rate and further requires steps such as activation of the catalyst.

(Problems to be Solved by the Invention) The present inventor has developed a method that does not require replacing the catalyst over a long period of time, and furthermore, continues the hydrogen peroxide decomposition reaction continuously without reducing the hydrogen peroxide decomposition ability of the catalyst. As a result of extensive research, we have completed the present invention.

(Means and effects for solving the problems) That is, the present invention provides a method for decomposing hydrogen peroxide by contacting a hydrogen peroxide solution with a catalyst, which has hydrogen peroxide decomposition ability as a catalyst and an oxygen-hydrogen bond. The present invention relates to a method for decomposing hydrogen peroxide, which includes a method for supplying hydrogen to the catalyst using a substance having the above-mentioned ability. Hydrogen can be supplied to the catalyst by, for example, bringing hydrogen gas or its diluted gas into contact with the catalyst at an appropriate flow rate, or using a catalyst that has the properties of a good electrical conductor in addition to the above-mentioned properties. There are methods of electrolyzing hydrogen peroxide using the catalyst as a cathode to generate hydrogen at the cathode (catalyst), and supplying hydrogen to the catalyst.

Catalysts to which the present invention can be applied include catalysts that have hydrogen peroxide decomposition ability and oxygen-hydrogen bonding ability, such as platinum and baradium, and catalysts that have properties as good electrical conductors, such as those plated with platinum and baradium, These include catalysts in which these metals are supported on porous metal pellets and activated carbon.

In the decomposition of hydrogen peroxide, the reaction shown by H2O2→H20-1-702 progresses, and oxygen is generated. When the activity of the catalyst decreases, supplying hydrogen gas to the catalyst restores the activity of the catalyst. In the case of a catalyst having a substantially high oxygen-hydrogen bonding ability, the catalytic activity is barely restored even if hydrogen gas is supplied to the catalyst.

Based on the above phenomenon, the present inventor believes that the decrease in the activity of the hydrogen peroxide decomposition catalyst is due to the fact that oxygen generated by the decomposition of hydrogen peroxide adheres to the surface of the catalyst and covers the catalyst surface. In the restoration, it was confirmed that oxygen was removed from the catalyst surface because hydrogen reacts with the oxygen covering the catalyst surface due to the hydrogen-oxygen bonding ability of the catalyst.

Next, implementation of the method of the present invention will be specifically explained. In the present invention, it is sufficient to simply supply hydrogen to the catalyst, but in its implementation, for example, hydrogen may be continuously or intermittently supplied to a container filled with a catalyst and flowing hydrogen peroxide solution. do it.

Specifically, hydrogen gas alone or diluted with inert gas,
Hydrogen gas 1~100 volumes of hydrogen peroxide solution
The objective can be achieved by supplying 1000 volumes to the catalyst. Practically preferred volume is 10 volumes or more.

The inert gas is industrially preferably nitrogen gas, but other inert gases may be used.

Furthermore, there is also a method of using a catalyst that has conductivity in addition to hydrogen peroxide decomposition ability and oxygen-hydrogen bonding ability, electrolyzing hydrogen peroxide water to generate hydrogen, and bringing this hydrogen into contact with the catalyst.

In this case, the catalyst itself should be used as a cathode, an anode should be provided outside the catalytic converter container, and the cathode chamber and anode should be separated by a porous material that is electrically insulating and allows only liquid to pass through, but not gas. is necessary. It is preferable that the porous material is dense, and specifically ceramics such as alumina and cordierite, and various polymer membranes are preferable, and they may be combined. Since the anode material comes into contact with the hydrogen peroxide solution, metals plated with noble metals, nickel, etc. are desirable.

Hydrogen may be supplied to the catalyst only when the catalyst activity decreases, but it may also be supplied constantly during the decomposition of hydrogen peroxide. In this case, the catalytic activity is always kept constant. Whether hydrogen is supplied continuously or only when the catalyst activity decreases may be appropriately determined depending on the reaction conditions and the like.

The catalyst may be used alone, or may be plated on a commercially available gold filler such as Dexon or McMahon.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

Example 1 −7= The present invention was carried out using the apparatus shown in FIG.

In the figure, / is hydrogen peroxide tank, C is pump, 3 is inert gas cylinder, G is hydrogen gas cylinder, '+ + '
t is a gas flow regulator for both gas cylinders, 6 is a silicon plug,
7 is glass wool, g is length 3 for decomposing hydrogen peroxide
001m5 glass tube with inner diameter of 20mm, 9 is a 5mm SUS plated with platinum which is the catalyst filled in the glass tube g
This is Dexon packing.

The hydrogen peroxide solution is stored in a hydrogen peroxide solution tank/inside the hydrogen peroxide solution tank. After that, it is sent into a glass tube. On the other hand, remove the hydrogen cylinder, adjust the flow rate with regulator 2 on the left, and pump hydrogen into pipe 1. of hydrogen peroxide and mix. Hydrogen is sent into the glass tube g together with the hydrogen peroxide solution and comes into contact with the catalyst 9. The hydrogen peroxide solution passes through the catalyst t, the hydrogen peroxide contained therein is decomposed, and the decomposed liquid is discharged from the top of the glass tube through the pipe t2.

In this example, the hydrogen peroxide concentration in the trench was 6. 106 ml of opp hydrogen peroxide solution was passed through the glass tube for 1 minute to degrade the hydrogen peroxide decomposition ability of the catalyst. In this case, the residence time of the hydrogen peroxide solution in the glass tube is about 50 seconds. Next, by operating the flow rate regulator of the hydrogen gas cylinder, hydrogen gas was caused to flow into the hydrogen peroxide solution in 304 minutes, flowed into the glass tube in parallel flow, and then flowed out of the tube. One hour after the start of the inflow, the hydrogen peroxide decomposition rate was determined. Furthermore, the hydrogen flow rate is 10M/min, 200 min.
300 m//9, and the hydrogen peroxide decomposition rate at each flow rate was similarly determined. The relationship between the hydrogen flow rate and the decomposition rate is shown by the line C/C in FIG. In the figure, the horizontal axis is the amount of hydrogen,
The vertical axis shows the decomposition rate of hydrogen peroxide.

Example 2 This example was carried out by filling the apparatus shown in FIG. 1 with a catalyst. First, a hydrogen peroxide solution with a hydrogen peroxide concentration of 6.5 pIn is passed through the glass tube at a rate of 106 m/min, and then the nitrogen gas is passed through the glass tube at a rate of 207.5 d/min by operating the nitrogen gas flow regulator. It was mixed into hydrogen peroxide solution at the same ratio. Degraded layer of the catalyst Operate the gas flow regulator for hydrogen gas to flow hydrogen gas into the hydrogen peroxide stream at a rate of 7.24 minutes, form a mixed gas with nitrogen gas, and mix it with the hydrogen peroxide gas in parallel flow with the glass. It was allowed to flow into and out of the pipe. Let's start the influx shi1
After 1 hour, the hydrogen peroxide decomposition rate was determined. Next, the nitrogen flow was left unchanged, and the hydrogen flow rate was increased to 26.3 m/7 min, 55.1
+++//9, and the hydrogen peroxide decomposition rate was similarly determined at each flow rate. The relationship between the volume of hydrogen gas in the mixed gas and the decomposition rate is shown by line 3/ in FIG.

Example 3 The nitrogen gas flow rate was 517.2 m/%, and the hydrogen flow rate was 16.3 ml for 7 minutes, then 31.8 m/7 minutes.
The process was carried out in the same manner as in Example 2 except that the hydrogen peroxide decomposition rate was determined at each hydrogen flow rate. Similarly to Example 2, the relationship between the volume of hydrogen gas in the mixed gas and the decomposition rate is shown by line 32 in FIG.

Embodiment 4 FIG. 4 shows an apparatus in which this embodiment was carried out. In the figure, /
, λ, 6, 6', 7, g are respectively as in Fig. 2,
A tank containing hydrogen peroxide, a pump for feeding hydrogen peroxide to the catalyst layer, a silicone stopper, glass wool, and a glass tube are shown. In addition, R/ is a DC power supply, Dako is a variable resistor, and G3 is a variable resistor. Ammeter, voltmeter on the rim, porous alumina pipe 5, nickel plate as the anode, 7 as the cathode and PT-plated Dexon packing, which is also the catalyst.
g is hydrogen peroxide solution.

As in FIG. 2, the hydrogen peroxide solution in the tank is pumped into the alumina tube II7 through the Ponbuco inlet tube t1, and passes through the palladium-plated Dexon packing catalyst in Hiro7. The hydrogen peroxide is decomposed and the decomposed liquid is discharged through the upper drain pipe.

In this example, hydrogen peroxide 24. Flow out the hydrogen peroxide solution containing apHn at 160 dlo, analyze the outlet liquid from the discharge pipe, and when the decomposition rate decreases, energize the cathode and anode (decomposition voltage 5 to 4° 4V), and confirm that the decomposition rate has improved. did. After applying electricity for 45 minutes, electricity was stopped, and after the decomposition rate had decreased, electricity was applied again. This operation was repeated. The results are shown in FIG. In the figure, the horizontal axis shows time and the vertical axis shows hydrogen peroxide decomposition rate.

In the figure, the decomposition rate of 80% at the start of the flow of hydrogen peroxide solution decreased over time as shown by the line S/.

When the decomposition rate became 60% or less, the decomposition rate rose rapidly as shown by the line octopus, and then stabilized as shown by line S3. When energization was stopped after 45 minutes, the decomposition rate decreased to 3/', so energization was continued as before, and thereafter, energization and discontinuation were repeated in the same manner. Through the above operations, the υ decomposition rate was always maintained above a certain value. That is, it was not necessary to particularly replace or take out the same catalyst to activate it for a long period of time, and decomposition of hydrogen peroxide could be continued.

Example 5 The same equipment as in Example 4 was used, and all the treatments were carried out in the same manner as in Example 4, except that electricity was applied continuously. The change in the decomposition rate of hydrogen peroxide water is shown by line 6/ in FIG.

As shown in the figure, in this example, the decomposition rate changed completely.
l-186208 (4) It was possible to continuously maintain a high decomposition rate without any decomposition.

Comparative Example 8 A φ glass tube was filled with platinum-plated Dexon packing and manganese dioxide pellets (particle size 2 to 4 mm), and water containing 17.0 ppm of hydrogen peroxide was pumped from one direction at 205 ml/rum. The hydrogen peroxide was decomposed by flowing at a rate of 100 ml, and the hydrogen peroxide decomposition rate was examined by sampling and analyzing at the outlet side.

The results are shown in FIG. In the figure, line 7/ shows the change in the decomposition rate of hydrogen peroxide when filled with platinum-plated Dexon packing, and line 7.2 shows the change in the decomposition rate of hydrogen peroxide when filled with manganese dioxide pellets.

In both the platinized Dexon packing catalyst and the manganese dioxide catalyst, the hydrogen peroxide decomposition rate decreased with time, and this was due to a decrease in catalyst activity.

(Effect of the invention) In the examples and comparative examples, conventionally, when decomposing hydrogen peroxide,
The activity of the catalyst used decreased over time, and it was necessary to renew the catalyst at regular intervals. However, with the present invention, the activity of the catalyst can always be maintained above a certain value, making it possible to renew the catalyst for a long time. This clearly shows that hydrogen peroxide can be decomposed without any decomposition, and the present invention is extremely useful in practical terms.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of an apparatus that can carry out Example 1.2.3, Figure 2 is a diagram showing the relationship between hydrogen flow rate and hydrogen peroxide decomposition rate in Example 1, and Figure 3 is Example 2. .6 is a diagram showing the relationship between hydrogen gas volume and decomposition rate, Figure 4 is a schematic diagram of the apparatus that can carry out Example 4, and Figure 5 is the change over time in the decomposition rate of hydrogen peroxide according to Example 4. Figure 6 is a diagram showing the change in hydrogen peroxide decomposition rate over time according to Example 5, Figure 7 is a diagram showing changes over time in hydrogen peroxide decomposition rate according to Example 5.
The figure shows the decomposition rate of hydrogen peroxide in a comparative example. /...Hydrogen peroxide tank, co...pump, 6...
- Silicon plug, 7...Glass wool, g...Glass tube, 9.17...Catalyst, ttS...Porous alumina pipe, G6...Anode nickel.

Claims (3)

[Claims] (1) In a method of decomposing hydrogen peroxide by contacting a hydrogen peroxide solution with a catalyst, a substance having hydrogen peroxide decomposition ability and oxygen-hydrogen bonding ability is used as a catalyst, and hydrogen is supplied to the catalyst. A method for decomposing hydrogen peroxide, characterized by: (2) The method for decomposing hydrogen peroxide according to claim 1, wherein the method for supplying hydrogen to the catalyst is to bring hydrogen alone or hydrogen diluted with an inert gas into contact with the catalyst surface. (3) The method of supplying hydrogen to the catalyst is a method of electrolyzing hydrogen peroxide using a catalyst that further has properties as a good electrical conductor and using the catalyst as a cathode. How to decompose hydrogen oxide.