JPH0555184B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a deodorizing catalyst used in a method of decomposing and deodorizing malodorous components in gas using ultraviolet rays and a catalyst. <Prior art and its problems> In recent years, odor pollution has been widely taken up as a social problem, and new odor control technologies have been developed and implemented. Conventionally, deodorization has been carried out by a chemical cleaning method, an adsorption method, a direct combustion method, a catalytic combustion method, an oxidation method using ozone, etc., but each has its advantages and disadvantages, and there are many practical problems. The chemical cleaning method generates a large amount of wastewater, resulting in high wastewater treatment costs, and the adsorption method often uses activated carbon as an adsorbent, but there is a risk of ignition and the deodorizing effect fades in a short period of time, so recycled or activated carbon is used. The drawback is that it is difficult to maintain the equipment, such as replacing it. The direct combustion method requires fuel, which increases running costs, and also requires safety considerations, which has disadvantages such as large-scale equipment. Although the equipment of the catalytic combustion method is relatively easy to maintain, it is necessary to maintain the catalyst layer temperature between 300°C and 450°C. has the disadvantage of high running costs. The ozone oxidation method uses the strong oxidizing effect of ozone to treat malodorous components, and can be treated at temperatures as low as room temperature, but depending on the method of use, safety issues may arise. It's coming. On the other hand, the ultraviolet oxidation deodorization method that uses ultraviolet light and a photoexcited catalyst is an inexpensive and safe method with excellent low-temperature activity, but the current situation is that a catalyst with higher activity is required. <Object of the Invention> Therefore, the object of the present invention is to provide an inexpensive and highly active photodeodorizing catalyst that can be used in an ultraviolet oxidation decomposition deodorization method. <Structure of the Invention> As a result of intensive research in line with the above objectives, the present inventors have developed a binary composite oxidation system consisting of titanium and silicon having a surface area of at least 100 m ² /g as a catalyst used in an ultraviolet oxidation decomposition deodorization method. It has been found that a binary composite oxide consisting of titanium, titanium, and zirconium or a ternary composite oxide consisting of titanium, silicon, and zirconium exhibits excellent deodorizing performance. Furthermore, it has been found that the above-mentioned binary composite oxide or ternary oxide in which part of it is replaced with activated carbon also exhibits excellent deodorizing performance. Furthermore, the present invention was completed by discovering that it is practically useful to form the above-mentioned catalyst into a honeycomb shape having an appropriate size. That is, the present invention contains a binary composite oxide consisting of titanium and silicon, a binary composite oxide consisting of titanium and zirconium, and/or a ternary composite oxide consisting of titanium, silicon, and zirconium. A catalyst for deodorizing by ultraviolet irradiation, characterized in that the composite oxide has a specific surface area of at least 100 m ² /g. <Function> The catalyst according to the present invention is characterized by a binary composite oxide (hereinafter referred to as TiO ₂ -
SiO ₂ ), binary composite oxide consisting of titanium and zirconium (hereinafter referred to as TiO ₂ -ZrO ₂ ), ternary composite oxide consisting of titanium, silicon and zirconium (hereinafter referred to as TiO ₂ -SiO _{2 ) −ZrO2}
) is used as a catalyst component. In general, binary composite oxides consisting of titanium and silicon are described, for example, by Kozo Tabe (Catalysts, Vol. 17, No.
3, p. 72 (1975)),
Known as a solid acid, it exhibits remarkable acidity that is not found in individual oxides, and has a high surface area. In other words, TiO ₂ -SiO ₂ is not simply a mixture of titanium oxide and silicon oxide, but it can be recognized that titanium and silicon form a so-called binary oxide, resulting in its unique properties. It is. In addition, binary composite oxides consisting of titanium and zirconium, and titanium,
A ternary composite oxide consisting of zirconium and silicon is also specified as a composite oxide having properties similar to TiO ₂ -SiO ₂ . Further, as a result of analysis by X-ray diffraction, the above-mentioned composite oxide has an amorphous or almost amorphous microstructure. Although the mechanism by which the catalyst of the present invention exhibits excellent malodorous component decomposition activity, especially at low temperatures, is not certain, it is believed that the various properties of the above composite oxide have a favorable influence on malodorous component decomposition activity. It will be done. TiO ₂ −SiO ₂ , TiO ₂ − constituting the present invention
It is preferable that both ZrO ₂ and TiO ₂ -SiO ₂ -ZrO ₂ have a surface area of 100 m ² /g or more. This is because, in this photodeodorizing reaction, malodorous components are adsorbed onto a catalyst and are then subjected to ultraviolet oxidative decomposition, and it is believed that the quality of adsorption of malodorous components greatly influences the deodorizing efficiency. The larger the surface area, the better the adsorption ability, and less than 100 m ² /g is insufficient. The composition of catalyst A component is TiO ₂ in terms of oxide.
20-95 mol% with _SiO2 or _ZrO2 or _SiO2
The sum of ZrO ₂ is 5 to 80 mol% (both TiO ₂ + ZrO ₂
+SiO ₂ =100 mol %) gives preferable results. To prepare TiO ₂ -SiO ₂ used in the present invention, first select a titanium source from inorganic titanium compounds such as titanium chlorides and titanium sulfate, and organic titanium compounds such as titanium oxalate and tetraisopropyl titanate. The silicon source can be selected from inorganic silicon compounds such as colloidal silica, water glass, silicon tetrachloride, and organic silicon compounds such as tetraethyl silicate. And among these raw materials,
Some contain trace amounts of impurities and contaminants, but they do not pose a problem as long as they do not significantly affect the physical properties of the TiO ₂ -SiO ₂ obtained. A preferred method for preparing TiO ₂ -SiO ₂ includes the following method. A method in which titanium tetrachloride is mixed with silica sol, ammonia is added to form a precipitate, the precipitate is washed, dried, and then calcined at 300 to 650°C. A method in which a sodium silicate aqueous solution is added to titanium tetrachloride and reacted to form a precipitate, which is then washed, dried, and then calcined at 300 to 650°C. A method in which ethyl silicate [(C ₂ H ₅ O) ₄ Si] is added to a water-alcohol solution of titanium tetrachloride to cause a hydrolysis reaction to form a precipitate, which is washed, dried, and then calcined at 300 to 650°C. Ammonia was added to a water-alcohol solution of titanium oxide chloride (TiOCl ₂ ) and ethyl silicate to form a precipitate, which was washed and dried for 300 min.
A method of firing at ~650℃. Among the above preferred methods, this method is particularly preferred, and this method is specifically carried out as follows. That is, the above-mentioned titanium source and silicon source compounds are taken so that the molar ratio of TiO ₂ and SiO ₂ is a predetermined amount, and titanium and silicon are converted into oxides in an acidic aqueous solution state or sol state to 1 to 1.
Make the concentration 100g/keep at 10-100℃. Aqueous ammonia was added dropwise as a neutralizing agent into the solution while stirring, and a coprecipitated compound consisting of titanium and silicon was formed at pH 2 to 10 for 10 minutes to 3 hours. After being filtered and thoroughly washed, Dry for ~10 hours, ~300
TiO ₂ -SiO ₂ can be obtained by firing at 650°C for 1 to 10 hours. Furthermore, for TiO ₂ −ZrO ₂ −SiO ₂ , TiO ₂ −
It is prepared by a method similar to SiO ₂ , and the zirconium source can be selected from inorganic zirconium compounds such as zirconium chloride and zirconium sulfate, and organic zirconium compounds such as zirconium oxalate. That is, _TiO2 - _ZrO2 - _SiO2 can be easily prepared by treating a zirconium compound together with a titanium compound in the same manner as described above. The amount of zirconium present is preferably within a range of up to 30% by weight in terms of ZrO ₂ based on the total amount of TiO ₂ +ZrO ₂ +SiO ₂ . The method for preparing TiO ₂ -ZrO ₂ can be performed in the same manner. TiO ₂ −SiO ₂ , TiO ₂ − prepared by the above method
Using _ZrO2 and _TiO2 - _SiO2 - _ZrO2 , a finished catalyst is obtained by the method shown below. For example, TiO ₂ --SiO ₂ powder can be added together with a molding aid, mixed while adding an appropriate amount of water, kneaded, and molded into a pellet or honeycomb shape using an extrusion molding machine, although a honeycomb shape is preferred. In particular, a honeycomb having a shape in which the equivalent diameter of the through holes is in the range of 0.7 to 3 mm, the cell wall thickness is in the range of 0.2 to 0.5 mm, and the aperture ratio is in the range of 50% or more is preferable. If the equivalent diameter of the through-holes of the catalyst exceeds 3 mm, the geometric surface area of the catalyst decreases, resulting in a decrease in deodorizing efficiency, which is undesirable. Moreover, if it is less than 0.7 mm, the pressure loss increases significantly, and at the same time, clogging by dust contained in the processing gas tends to occur, and the efficiency of ultraviolet ray irradiation deteriorates, which is not preferable. After drying the molded product at 50-200°C, dry at 300-700°C, preferably 350-600°C for 1-10 hours, preferably 2-6 hours.
The catalyst can be obtained by calcination under air flow for a period of time. It is also possible to use additional carriers. Examples of carriers that can be used include alumina, silica, silica-alumina, bentonite, diatomaceous earth, silicon carbide, titania, zirconia, magnesia, cordierite, mullite, pumice, activated carbon, and inorganic fibers. It can be prepared by making a slurry of TiO ₂ -SiO ₂ and other catalyst components on a cutting tool and supporting the slurry by an impregnation method. Of course, the catalyst preparation method is not limited to these methods. Furthermore, activated carbon and TiO ₂ −SiO ₂ , TiO ₂ −ZrO ₂
and/or _TiO2 - _SiO2 - _ZrO2 to obtain a finished catalyst by the method shown below. For example, if TiO ₂ −SiO ₂ powder and activated carbon powder are mixed well,
If necessary, a forming aid is added, and an appropriate amount of water is added while mixing and kneading to form the desired shape. Next, the molded product is dried and, if necessary, fired. Activated carbon is generally in the form of a powder, but some forms of rectangular fibers can also be used. As a forming means,
Various known methods including pressure molding and extrusion molding can be employed. The molded product is dried at a temperature of 50 to 200°C, and since the molded product contains flammable activated carbon, it is preferable to carry out the firing in a non-oxidizing atmosphere, but it can also be carried out in air if the amount of combustible material is small. The firing temperature is 200 to 600°C for 1 to 10 hours, and if it is not necessary, it is preferable to just dry. The catalyst according to the invention can be used to treat gases emitted from food storages, garbage storage facilities, human waste treatment plants, sewage treatment plants, garbage incineration plants, cleaning printing factories, paint factories, general chemical factories, and the like. The deodorizing method using a catalyst of the present invention is a method in which a deodorizing catalyst is installed in a gas flow path containing malodorous components, and the catalyst is irradiated with ultraviolet rays to oxidize and remove the malodorous components. The wavelength of ultraviolet rays is suitably 200 to 400 nm, and can be generated by using a mercury lamp or a xenon lamp alone or in combination. The catalyst of the present invention has an excellent ability to oxidize and decompose malodorous components under ultraviolet irradiation, and also has an excellent ability to adsorb malodorous components. In particular, the adsorption capacity is increased by adding activated carbon. It is very useful to use the catalyst of the present invention, which combines the above two abilities, as follows. That is, the malodorous components are first adsorbed onto the catalyst without irradiation with ultraviolet rays, and then the malodorous components are oxidized and decomposed by irradiation with ultraviolet rays. This is a method of deodorizing by repeating the above steps. This method can save power consumption and extend the life of the UV lamp. The present invention will be explained in more detail below using Examples, but the present invention is not limited to these Examples. Example 1 A composite oxide consisting of titanium and silicon was prepared by the method described below. A sulfuric acid aqueous solution of titanyl sulfate having the following composition was used as a titanium source. TiOSO ₄ (TiO ₂ conversion) 250g / Total H ₂ SO ₄ 1100g / Separately 400% water and ammonia water (NH ₃ , 25%)
Add 280 and add Snowtex-NCS- to this.
30 (silica sol manufactured by Nissan Chemical, containing approximately 30% by weight as SiO ₂ ) 24 kg was added. A titanium-containing aqueous sulfuric acid solution diluted by adding 153 ml of the titanyl sulfate aqueous sulfuric acid solution to 300 ml of water was gradually dropped into the obtained solution with stirring to produce a coprecipitated gel. 15 more as is
It was left to stand still for some time. The TiO ₂ thus obtained
-The SiO ₂ gel was filtered, washed with water, and then dried at 200°C for 10 hours. Then, it was fired at 550°C for 6 hours in an air atmosphere.
The composition of the obtained powder was TiO ₂ :SiO ₂ =4:1 (mole ratio), and the BET surface area was 185 m ² /g. The powder thus obtained was hereinafter referred to as TS-1, and using this powder, a lattice-shaped honeycomb deodorizing catalyst was prepared by the method described below. Add an appropriate amount of water to 10 kg of the above TS-1 powder, mix well with a kneader, thoroughly knead with a kneader,
The homogeneous mixture is extruded into molding machines with external dimensions of 50 mm in length and width.
50mm, length 100mm lattice honeycomb (wall thickness 0.3mm,
It was molded into a mesh size of 1.4 mm, dried at 150°C for 5 hours, and then calcined at 300°C for 2 hours in an air atmosphere to obtain a deodorizing catalyst named TS-1H. Example 2 _TiO2 - _ZrO2 was prepared by the method described below. Zirconium oxychloride [ZrOCl ² _.
8H ₂ O] was dissolved and mixed well while adding 78 g of a sulfuric acid aqueous solution of titanyl sulfate having the same composition as used in Example 1. While maintaining the temperature at about 30°C and stirring well, ammonia water was gradually added dropwise to the mixture until the pH reached 7, and the mixture was left to stand still for 15 hours. The thus obtained TiO ₂ −ZrO ₂ gel was filtered,
After washing with water, it was dried at 200°C for 10 hours. It was then dried at 550° C. for 6 hours in an air atmosphere. The composition of the obtained powder was TiO ₂ :ZrO ₂ =4:1 (molar ratio),
The BET surface area was 140 m ² /g. The powder obtained here is hereinafter referred to as TZ-1. A catalyst named TZ-1H was prepared using TZ-1 according to the method described in Example 1. Example 3 TiO ₂ −SiO ₂ − according to the method of Examples 1 and 2
_ZrO2 was prepared. The composition of the obtained powder is _TiO2 :
SiO ₂ :ZrO ₂ =80:16:4 (molar ratio), and the BET surface area was 180 m ² /g. The powder obtained here is hereinafter referred to as TSZ-1. A catalyst named TSZ-1H was prepared using TSZ-1 according to the method described in Example 1. Example 4 After mixing 7.5 kg of TS-1 powder obtained in Example 1 and 2.5 kg of commercially available activated carbon, an appropriate amount of water was added and the mixture was thoroughly mixed in a kneader and thoroughly kneaded in a kneader to form a uniform mixture. Extrude the mixture into a molding machine with an external size of 50mm
mm, width 50mm, length 100mm lattice honeycomb (wall thickness 0.3
mm, opening 1.4 mm) and dried at 150° C. for 2 hours to obtain a finished catalyst with a BET surface area of 380 m ² /g. Example 5 After installing 50 ml of the catalyst prepared in Examples 1 to 4 into a deodorizing device consisting of a fan, an ultraviolet lamp, and a catalyst installation part shown in Fig. 1, the deodorizing device was
After introducing methyl sulfide so that the concentration inside the container was 20 ppm, the deodorizer fan was turned on, the ultraviolet lamp was turned on, and the methyl sulfide concentration was measured after 1 hour. Table 1 shows the results.
Shown below. Comparative Example 1 The test described in Example 5 was carried out without catalyst.
The results are shown in Table-1. Comparative Example 2 TS-1 obtained in Example 1 was fired at 800°C for 6 hours in an air atmosphere. The composition of this powder is _TiO2 :
At SiO ₂ = 4:1 (molar ratio), the BET surface area is 70
m ² /g. A finished catalyst was obtained from this powder in the same manner as in the examples. This was tested in the same manner as in Example 5, and the results are shown in Table 1. 【table】

[Brief explanation of the drawing]

Figure 1 shows one of the deodorizing devices used in the present invention.
FIG. 2 is a schematic diagram illustrating an example. 1: Ultraviolet lamp, 2: Deodorizing catalyst, 3: Fan.

Claims (1)

[Scope of Claims] 1 Contains a binary composite oxide consisting of titanium and silicon, a binary composite oxide consisting of titanium and zirconium, and/or a ternary composite oxide consisting of titanium, silicon, and zirconium. A catalyst for deodorizing by ultraviolet irradiation, characterized in that the composite oxide has a specific surface area of at least 100 m ² /g. 2. The catalyst according to claim 1, wherein 5 to 90% by weight of the catalyst is substituted with activated carbon. 3 The shape of the catalyst is such that the equivalent diameter of the through hole is 0.7 to 3 mm.
3. The catalyst according to claim 1, wherein the catalyst has a honeycomb shape with a cell wall thickness of 0.2 to 0.5 mm and an aperture ratio of 50% or more.