JPS5918094B2 - Ozonolysis method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating ozone-containing gas, which is characterized by using a calcined molded product of an activated carbon-zeolide mixture as an ozone decomposer (or catalyst).

More specifically, the present invention relates to a calcined body obtained by drying a molded body made of an activated carbon-zeolide mixture and then calcining it in an inert gas atmosphere. (Patent Application No. 52-113546 (
(See Japanese Patent Publication No. 58-35929)).

The present invention provides a new method for safely and economically treating ozone-containing gas to render the ozone in the gas harmless using the invention (hereinafter referred to as the prior invention).

Now, since ozone has extremely strong oxidizing power,
Taking advantage of its properties, it is widely used in the decolorization process of colored substances and the oxidation removal process of harmful and malodorous components.

Ozone is also currently used for purposes such as sterilization.

Recently, the field of use of ozone has been expanded to include tertiary treatment of wastewater.

However, since ozone is harmful, appropriate detoxification measures are required after its use.

For example, when used ozone-containing waste gas is released into the atmosphere, its photochemical reaction causes the generation of oxidants, resulting in secondary pollution.

Therefore, from the standpoint of pollution prevention, it goes without saying that it is necessary to safely treat ozone-containing waste gas to make it harmless below the regulatory value before releasing it into the atmosphere.

By the way, typical methods for treating ozone-containing gas include (a) a decomposition method using heat or light, (b) a chemical decomposition method using a reducing substance-containing liquid, and (C) a three-force method of decomposition using a catalyst. can give.

Viewed from the above classification, the present invention belongs to method (C), a catalytic decomposition method.

This catalytic decomposition method performs ozone treatment using a dry method, so it has the advantage that related equipment and operation are more economical than (a) one method or (b) one method wet method. be.

Activated carbon has been used as a typical catalyst for ozone decomposition, but this has the disadvantage that it undergoes a chemical reaction with ozone and generates carbon monoxide and carbon dioxide gas, which naturally causes the activated carbon itself to be consumed.

Furthermore, when the above is used, the temperature of the catalyst layer increases due to the heat of reaction between activated carbon and ozone.

If the temperature of the activated carbon catalyst layer rises rapidly during the treatment process, there is a risk of ignition or, in the worst case, an explosion.

In order to improve the drawbacks of activated carbon catalysts, one of the inventors of the present invention previously proposed a new decomposing agent (catalyst) for ozone gas (Japanese Patent Application No. 51-112645).
Please refer to the publication)).

After that, in consideration of the case where the above decomposer is used as a general adsorbent or catalyst in a packed column, improvements in the manufacturing process (see prior invention) were made to increase the mechanical strength of the product and its performance. ) was carried out.

Furthermore, various physicochemical tests and performance evaluation tests were conducted on the improved product obtained.

The present invention proposes a method for safely treating and rendering ozone-containing gas harmless using a molded calcined body of an activated carbon-zeolide mixture obtained by the method described in the prior invention.

The details of the invention are described below.

Powdered or granular activated carbon and zeolite are combined with organic and/or
Alternatively, wet mixing is performed in the presence of an inorganic binder, followed by molding, and the resulting molded product is dried and then calcined in an inert gas atmosphere.

In the present invention, a molded plate of activated carbon-zeolide mixture produced by the method described above is used as an ozone decomposing agent,
This effectively treats ozone-containing gas and renders it harmless.

It is desirable that the activated carbon and zeolite which are the constituent materials of the molded plate are both porous and in the form of fine particles or powder having a large surface area.

The zeolite mentioned here is an aluminosilicate with a three-dimensional structure.
), the composition of which is generally expressed as M2O.Al2O3.XS, 02.YH20.

However, M represents a monovalent or divalent metal ion, n represents its valence, and X and Y represent coefficients of silicic anhydride and crystal water, respectively.

Both natural and synthetic zeolites can be used as zeolites [Examples of natural zeolites (mordenite, clinoptilolite, chabasite), examples of di-synthetic zeolites (commercially available molecular sheets MS-3A, 4A, 5A: MS)
-13X)).

- Preferred examples of activated carbon include coal-based, coconut shell-based, activated carbon produced by petrochemical products, and the like.

These zeolite-activated carbon mixtures are mixed by a wet method in the presence of a binder according to the method described in the prior invention, and then molded into an appropriate shape (pellet, tablet, spherical product, etc.), and the molded product has a mass of 100%. After a drying process at around 350°C, it is finally heated to 350°C in an inert gas atmosphere such as nitrogen or argon gas.
It is calcined in a temperature range of 600°C.

Compared to known ozone decomposition catalysts, the calcined body obtained by the above method has the advantage that it can be used for a long period of time and exhibits high efficiency in processing ozone-containing gas because it has superior mechanical strength. .

Coconut shell activated carbon having large specific surface area and pore volume among activated carbon materials [Coconut shell activated carbon powder (Q: specific surface area>l)
ooom/l pore volume>0.9rnl/I] and zeolite [zeolite powder (Z): specific surface area>=300m/g)
The molded plate-fired product prepared by the above-mentioned method using a mixture of As is clear from the examples, this works extremely effectively in treating low to high concentration ozone-containing gases that are in dry to moist conditions, keeping the ozone concentration in the treated gas below the regulatory value (for example, O1 level). (below) has the following characteristics.

Now, a method for specifically treating ozone-containing gas using the ozone decomposer (catalyst) described above will be described.

When treating ozone-containing gas in a dry state, it is usually sufficient to form a layer using the above-mentioned decomposer (catalyst) and pass the ozone-containing gas through this layer at an appropriate flow rate (first step).
(See the side where the ozone decomposition layer is formed).

For example, using the packed tower shown in Figure 1, the ozone concentration is
When processing gases of 500pIII or less, inches to %
An ozone decomposer layer in the form of inch pellets may be formed and treated at a superficial velocity of 2,000 to 20,000 hr'.

In this case, as will be clear from the examples described below, the contact time is extremely short, on the order of several seconds, and the present catalyst layer acts effectively, easily reducing the initial ozone concentration (800 to 3,000 ozone) in the sample gas to zero. .1 pl)01 or less.

Furthermore, from the examples, it is clear that the activity of the present catalyst is maintained over a long period of time.

Next, the ozone-containing gas is in a hygroscopic state, such as relative humidity (R,
Even when H,) is around roo%, the present catalyst works clearly more effectively than in the Examples described later, and has the advantage that the catalytic activity is maintained over a long period of time.

Therefore, when processing gases with humidity at the above level, a dehumidifier should be installed in particular to reduce the dew point of the gas, P,
There is no particular need for operations such as lowering the value, so it is economical.

The ozone decomposition ability of this catalyst is high and it treats ozone-containing gas in a dry state extremely effectively.
This catalyst exhibits high performance not found in known catalysts for the treatment of ozone-containing gas in a moisture-absorbing state such as 0%.
The catalytic activity is excellent, and a major feature is that it is retained for a long period of time (see Examples).

The above points are suitable for performing ozone treatment during the tertiary treatment of wastewater and treating the wet ozone waste gas released at that time.

- When the object to be treated is a gas-liquid mixed system (containing ozone), for example, when a considerable amount of liquid droplets are entrained in the ozone waste gas, the catalyst layer will gradually become covered with a liquid layer as the usage time increases. Active sites are gradually lost and deteriorated.

Therefore, when ozonating a gas-liquid mixed system, it is necessary to deliquify the gas using a simple gas-liquid separator in advance.
.

It is a good idea to maintain the ozone decomposition agent at around loo% and then treat it with the present catalyst layer, as this will extend the life of the present ozone decomposer.

Next, the present invention will be explained with reference to examples, but the present invention is not limited to these examples unless the gist thereof is exceeded.

Production Example 1 This example relates to a production example of the ozone decomposer (catalyst) used in the present invention.

Since the manufacturing details have already been described in the prior invention, an outline thereof will be described here.

Bentonite was added as an inorganic binder to a powdered (200 to 250 mesn) zeolite and activated carbon mixture and uniformly mixed using a V-mixer.

Next, sugar was added as an organic binder to the mixture, and the mixture was mixed using a kneader in the presence of water.

However, sugar was added as an 8-ounce aqueous solution.

During the above-mentioned wet kneading, the moisture content was maintained between 35 and 45.

The mixture obtained in the above process is molded into inch or inch pellets by a molding machine and then heated to a temperature of 100° to 110°C.
dried in

The dried pellets are then finally dried at 450°-500°C for 2
The ozone decomposer (catalyst) used in the present invention was obtained by calcining in an inert gas atmosphere of nitrogen for ~3 hours.

Table 1 shows production examples of the ozone decomposition catalyst (or decomposition agent) of the present invention.

In this example, the activated carbon is coconut shell activated carbon powder (specific surface area = 1300 m/g, pore volume = 1.1CIIIL/
g), and the zeolide powders used are of the types shown below, all of which have a specific surface area of 350 m/g or more.

ZE505 in the table represents the trade name Zeoherb ZE505 (mordenite-based zeolite) manufactured by Osaka Sanso Kogyo Co., Ltd., and ZEO25 represents the trade name Zeobarb ZEO25 (natural mordenite).

Furthermore, MS-13X represents a commercially available X-type zeolide powder.

All molded products with serial numbers A to E are in an inert atmosphere (N2).
Because it is calcined for several hours inside, the loss of carbon components is extremely small and prevented, despite the calcining process exceeding the flash point of activated carbon, and the strength of the molded product is also excellent. etc. are suitable for ozone decomposition.

Example 1 This example describes a treatment test for ozone-containing gases.

A performance evaluation test of the prototype ozone decomposer was conducted using the test equipment shown in Figure 2.

The raw air is sent from the pipe 1 through the compressor 2 to the constant temperature chamber 4, and after being kept at a constant temperature in this S, it is introduced into the ozone generator 3, where some of the oxygen in the air is converted into ozone. be done.

Next, the ozonized air is supplied in a dry state to the catalyst column 6 at a constant flow rate.

Thermocouples T, C, are attached to the catalyst tower.

When testing using a humidified gas, the ozone-containing air (dry state) from 3 is kept saturated with water using the water saturator 8, and then the air is de-gassed using the drain separator 9.
After the liquid is separated, it is introduced into the catalyst column 6 at a constant flow rate.

The gas released from the catalyst tower is discharged to the outside through 10 flowmeters.

Note that the ozone concentration at the inlet and outlet of the catalyst tower can be determined using an ozone concentration meter (Dasibi-ultraviolet absorption type) of 13 or 11-1.
It is designed to be able to be introduced into the second ozone titration device.

In the figure, P indicates a dew point measuring device.

2400-280 as ozone by the method according to the invention.
Table 2 shows examples of processing gases containing 0 ppm.

The symbols in the table for the ozone decomposers used in this test are the same as the manufacturing numbers in Table 1.

Moreover, the ozone concentration in the table shows the average value during the test.

Test numbers-1, 2, and 5 show the results when using ozone-containing dry air, and test numbers-3 and 4 show the results when using ozone-containing dry air.
The results are shown when ozone-containing air with R, H, ) close to roo% is used.

As is clear from this test example, the ozone decomposer composed of coconut shell activated carbon-zeolide system clearly exhibits excellent performance in treating ozone-containing dry gases, even when looking at the time required to reach the indicated ozone breakthrough point. are doing.

Furthermore, when treating ozone-containing gas in a moist state, the catalyst used in the present invention exhibits even greater activity.

That is, from the comparison of Test Nos. 1 and 3, it is clear that during ozone treatment, there is an advantage that the time required to reach the ozone breakthrough point is significantly longer when the treatment is performed in a moist state than in a dry state.

Next, ratios -1 to -2 show one comparative test example.

It can be seen that the ozone decomposition method according to the present invention gives better results than the comparative example.

Ratio-2 is a comparative test example using a commercially available product.

In this case, the ozone breakthrough point is reached within 15 seconds, so the treatment effect is low.

Next, Table 3 shows 03=800ppm (
The results of an ozone detoxification test conducted using the method of the present invention are shown (test numbers 6 to 8) regarding the average value.

Excellent results can be obtained when using ozone decomposers C and B in the form of 1-inch pellets.

Ratios -3 to 7 are comparative test examples.

The activated carbon catalyst (commercial product - ■, % inch pellet) has clearly inferior performance compared to A (test number - 6) used in the present invention.

Moreover, it is clear from the test results that the comparative example ZC-H and the commercial product -2 are inferior in performance compared to the ozone decomposition catalyst used in the present invention.

Generally speaking, as mentioned above, the catalyst used in the present invention has the advantage that the temperature rise in the catalyst tower during ozone treatment is kept small compared to a catalyst composed only of activated carbon (for example, a commercially available product -■). It is like that.

[Brief explanation of drawings]

FIGS. 1 to 3 illustrate the method of filling the catalyst when treating ozone-containing gas with the method of the present invention. It is possible to use a conventional packed column as shown in FIG. 1, or to use a collapsed apparatus consisting of a catalyst layer and a gas layer as shown in FIG. 2 or 3. In the figure, 1 indicates the catalyst layer and 2 indicates the gas layer. In either case, the ozone-containing gas is introduced into the processing device ζ in the direction of the arrow, and the treated gas rendered harmless is discharged from the top. Figure 4 shows an ozone decomposition test device. Reference numeral 1 indicates a raw material air introduction pipe, 2 indicates a compressor, and 3 indicates an ozone generator (equipped with a dryer). 4 is a constant temperature bath that keeps the raw air at a constant temperature. 5 is a high heat to cold heat generating device for water circulation to the constant temperature bath. Further, 6 is a catalyst tower, 7 is a constant temperature bath for generating a constant humidity gas, and 8 and 9 are a moisture saturator and a drain separator, respectively. 10 is a flow meter (wet type), 11 and 12 are ozone titration systems, and 13 is an ozone concentration meter (DASIBI: ultraviolet absorption type). D, P, and T, C indicate the insertion positions of the dew point detector and thermocouple, respectively.

Claims (1)

[Claims] 1. Powdered or granular activated carbon and zeolite are wet mixed in the presence of an organic and/or inorganic binder, then molded, and the molded product is dried and then heated with an inert gas. A method of treating ozone-containing gas to make ozone harmless using a molded plate of an activated carbon-zeolide mixture obtained by calcining in an atmosphere. 2 The molded plate-grilled product is composed of coconut shell activated carbon (C) and zeolite (Z), and the weight ratio (C/Z) of the coconut shell activated carbon (Q and zeolite (Z)) is 0.3 to 0.3 to zeolite (Z).
9.0.