JPH0712414B2 - Deodorization method in the freezer / refrigerator - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for removing odorous components in a freezer / refrigerator by a catalytic oxidation method on a catalyst. The freezer / refrigerator of the present invention includes an independent freezer or a refrigerator and a freezer / refrigerator having both functions. In the latter case, the freezer compartment and the refrigerator compartment are not independent. Type and two independent each
Although all of the above door types are included, the term "refrigerator" will be used as a representative in the following description for convenience.

[Prior Art and its Problems] Removing foul odors in refrigerators has long been a problem, but refrigerators in general households tend to grow in size with changes in dietary habits, and the increase in items to be stored and the longer storage period It is remarkable. Along with this, the demand for refrigerators has become widespread, and the desire to eliminate the extremely complicated foul odors in refrigerators has become even stronger.

Various items such as fish, meat, vegetables, fruits, and dairy products are stored in the refrigerator, but many of them have a unique odor. For example, amines and hydrogen sulfide are generated from fish, aldehydes, hydrogen sulfide, and ammonia are generated from meat, and methyl mercaptan and hydrogen sulfide are generated from vegetables. The mixed odor of these is unpleasant. .
Then, this unpleasant odor causes a problem that it is transferred to other food or melts into the ice in the ice making room.

As a method of removing the odor of a refrigerator, there are (1) a method of using an adsorbent that has been used for a long time, and (2) an ozone deodorizing method that has recently been put into practical use. In the case of using the adsorbent, the adsorption life is short and the duration of the deodorizing effect is very short, so there is the annoyance that it has to be converted frequently, and due to insufficient management in the warehouse, it is necessary to replace it. If it is lost, there is a problem that the deodorizing effect is instantly lost. On the other hand, in the ozone deodorizing method, although the deodorizing effect is excellent, there are new problems that the running cost is increased by constantly driving the ozone generator and that the excess ozone itself is treated.

[Problems to be Solved by the Invention] An object of the present invention is to remove odor in a refrigerator.
An object of the present invention is to provide a deodorizing method in a refrigerator that exhibits a stable and efficient deodorizing effect for a long period of time and is inexpensive in terms of equipment cost and material cost.

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies in accordance with the above-mentioned object, and as a result, T
catalyst A component containing at least one element selected from the group consisting of i, Si, Al, Zr and Mg, and Mn, Fe, Co, Ni, Ag, A
After the odor component is adsorbed on the catalyst composed of the catalyst B component containing at least one element selected from the group consisting of u, Pt, Pd and Rh, the catalyst is heated and the adsorbed odor component is catalytically oxidized on the catalyst. It has been found that a deodorizing method in a refrigerator in which a removing operation is repeated is an inexpensive deodorizing method in a refrigerator that provides a stable and efficient deodorizing effect for a long period of time.

[Operation] As an important technical element of the present invention, adsorption and catalytic oxidation reaction can be mentioned. Therefore, a catalyst having excellent adsorption ability and catalytic oxidation ability is required.

From the viewpoint of adsorption capacity, Ti, Si, Al, Zr and inorganic compounds containing at least one element selected from the group consisting of Mg are excellent, but among them, binary compound oxides consisting of Ti and Si, Ti Binary complex oxides of Ti and Zr and Ti, Si
Particularly preferred is at least one complex oxide selected from the group consisting of ternary complex oxides consisting of and Zr. In the present invention, these are referred to as catalyst A components.

Next, from the viewpoint of catalytic oxidation ability, Mn, Fe, Co, Ni,
At least one element selected from the group consisting of Ag, Au, Pt, Pd and Rh is excellent, but considering that it is used in a refrigerator, it is required to exhibit high activity even at low temperatures, so Pt And / or Pd are particularly preferred. In the present invention, these are referred to as catalyst B components.

In the present invention, the catalyst A component and the catalyst B component are used in combination,
It is placed in a suitable place in the refrigerator, for example, in the circulation path of cold air.
It is desired that this position be near the defrosting heater for the reason described below. When the catalyst of the present invention is arranged in this way, the odorous components in the air stream passing through the position are sequentially adsorbed on the catalyst A component and prevent the odorous components from accumulating in the circulating air stream.

When the catalyst of the present invention is heated at an appropriate time before the breakthrough of the adsorption of the odorous component on the catalyst A component, the odorous component on the catalyst A component undergoes catalytic oxidation by the action of the catalyst B component,
CO ₂ and H ₂ O are decomposed to recover the adsorption activity of the catalyst A component.

As the heating means, it is possible to install a heater specially for the catalytic oxidation reaction for removing the odorous component, but it is possible to effectively use the existing heater in the refrigerator due to economical and space problems. preferable. Since the defrosting heater operates intermittently (for example, once or twice a day) after a certain period of time for the purpose of defrosting the inside of the refrigerator,
Use of this seems to be most preferable in terms of heating cycle and heat capacity. Moreover, an existing defrosting heater which is generally used generally requires the catalyst of the present invention placed in the vicinity thereof in a suitable temperature range (usually 200 to 250 ° C.) for catalytic oxidation in the calorific value and the operating time. Good time (usually 20
It was found to be convenient for heating (about 40 minutes).

The shape of the catalyst of the present invention is subject to restrictions depending on the installation location and the like, but it is not particularly limited. Considering the adsorption capacity, it is preferable to use a honeycomb shape in which the geometric surface area is relatively large even if the occupied space is the same.

Hereinafter, the present invention will be described in more detail with reference to Examples.
The invention is not limited to this embodiment only.

[Example] FIG. 1 is a conceptual side view showing an example of an embodiment of the present invention, FIG. 2 is a conceptual diagram showing a cross section taken along line II-II of FIG. 1, and the figure is a freezing compartment 6 and a refrigerating compartment 7. Indicates the type divided into. The cool air generated by the cooler 4 is sent into the freezer compartment 6 by the fan 5 and circulated through the freezer compartment return duct 8, a part of which is supplied to the refrigerator compartment 7 through a path (not shown), and the refrigerator compartment 7 After being cooled, it is returned to the cooler 4 via the refrigerating compartment return duct 9. Reference numeral 1 denotes an existing defrosting heater, which regularly heats and melts the frost attached and grown on the cooler 4. A water drop prevention plate 3 prevents water drops melted and dropped from the cooler 4 from being applied to the defrosting heater 1, and also functions as a hood that guides cool air into the catalyst 2.

The shape of the catalyst used in the present invention is not particularly specified, but a catalyst having through holes formed along the gas flow direction is particularly recommended. Various embodiments of such a catalyst form will be described in detail later, but in the following description, the term “honeycomb-like” is used as a representative. The honeycomb-shaped catalyst 2 is provided directly above the defrosting heater 1 and utilizes the heat generated by the heater 1. However, the performance of the catalyst 2 is different from the case where it is provided along the entire length of the heater 1 as shown in FIG. Depending on the length of the heater 1, it may be a fraction of the total length, and it may be provided at one location or at two or more locations along the length direction of the heater 1. In any case, the through holes of the catalyst 2 are arranged so as to be horizontal, and cool air that moves from the front side to the rear side (from the right side to the left side in FIG. 1) of the refrigerator through the permeation holes is transferred to the honeycomb type catalyst. It shall be in contact with the through passage and its surface. Although FIGS. 1 and 2 show the case where the honeycomb-shaped catalyst 2 having a large number of through holes is used in both the conventional row and the horizontal row, the shape of the catalyst 2 is not limited to that shown in FIG. Through hole
It may have a shape in which 10 are arranged in a horizontal row or a shape in which the outer surface of the catalyst 2 is corrugated to increase the surface area as shown in FIG. In addition, as shown in FIGS. 3 and 4, it goes without saying that a plurality of sheets may be stacked and installed. Although the size, shape, and arrangement pitch of the through holes 10 are constant in each of FIGS. 3 and 4, they can be arbitrarily changed in consideration of the flow resistance in the left-right direction.

The catalyst used in the examples was prepared as follows.

First, a composite oxide composed of Ti and Si was prepared by the method described below. As a Ti source, a sulfuric acid aqueous solution of titanyl sulfate having the following composition was used.

TiOSO ₄ (converted to TiO ₂ ) 250 g / l Total H ₂ SO ₄ 1100 g / l Add 280 l of 25% ammonia water to 400 l of water separately, and add Snowtex-NCS-30 (Nissan Chemical's silica sol, about 30 as SiO ₂ 24 wt.%) Was added. A titanium-containing sulfuric acid aqueous solution prepared by adding 153 l of the above titanyl sulfate aqueous sulfuric acid solution to 300 l of water was gradually added dropwise to the obtained solution under stirring to form a coprecipitated gel. Further, it was left as it was for 15 hours. The TiO ₂ -SiO ₂ gel thus obtained was filtered, washed with water and
It was dried at 0 ° 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 (molar ratio), and the BET surface area was 185 m ² / g. The powder obtained here will be referred to as TS-
This powder was referred to as No. 1 and a lattice-shaped honeycomb deodorizing catalyst was prepared by the method described below.

A suitable amount of water was added to 10 kg of the above TS-1 powder, mixed well with a kneader, thoroughly kneaded with a kneader, and a uniform mixture was formed into a lattice honeycomb with an extruder (inner thickness 0.3 mm, opening 1.4 mm).
Then, it was dried at 150 ° C. for 5 hours and then fired at 300 ° C. for 2 hours in an air atmosphere to obtain a honeycomb molded body. Subsequently, an aqueous platinum nitrate solution was impregnated, dried and calcined to obtain a catalyst having a Pt supported amount of 2 g per catalyst 1.

Deodorization in the refrigerator is performed in the following order. As shown in FIG. 1, the return air from the refrigerating chamber 7 and the freezing chamber 6 comes into contact with the catalyst 2 before coming into contact with the cooler 4, and the odorous components contained in the return air are adsorbed and removed. . Since the catalyst 2 is heated by the defrosting heater during defrosting, the adsorbed odorous components are catalytically oxidized and removed on the catalyst 2. After the completion of defrosting, the odorous components adsorbed on the catalyst have been decomposed and removed, so that the adsorption capacity has returned to the original state and the adsorption of the odorous components is started again. The above operation is repeated.

[Advantages of the Invention] A long-term deodorizing effect can be expected by repeating the operation of adsorption of an odorous component by a catalyst and subsequent catalytic oxidation reaction of the odorous component.

Since it uses a catalyst with a good ability to absorb odorous components,
Great deodorizing effect.

When the honeycomb-shaped catalyst is used, the geometrical surface area is increased and the adsorption capacity is increased in proportion thereto, so that the deodorizing effect is increased.

When a defrosting heater is used, the heater installation cost is unnecessary, so the deodorizing method is inexpensive.

[Brief description of drawings]

FIG. 1 is a side view conceptual diagram showing an example of an embodiment of the present invention, FIG. 2 is a conceptual diagram showing a cross section taken along line II-II of FIG. 1, and FIGS. 3 and 4 are catalyst shapes used in the present invention. It is a perspective view which shows an example. 1 ... Defrosting heater, 2 ... Catalyst 3 ... Water drop prevention plate, 4 ... Cooler 10 ... Through hole

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location B01D 53/81 B01J 23/34 ZAB A 8017-4G 23/38 ZAB A 8017-4G 23/74 ZAB A 8017-4G F25D 23/00 302 M 7380-3L B01D 53/34 ZAB (72) Inventor Kayoshi Nishikawa 1 992 Nishikioki, Kamahama-ku, Aboshi-ku, Himeji-shi, Hyogo Pref. (72) Invention Akira Inoue 1 992 Nishi-oki, Okihama, Aboshi-ku, Himeji-shi, Hyogo Prefecture 1 Catalysis Laboratory, Nippon Catalysis Chemical Co., Ltd.

Claims (4)

[Claims] 1. A catalyst A component containing at least one element selected from the group consisting of Ti, Si, Al, Zr and Mg, and M
After the odorous component is adsorbed on the catalyst composed of the catalyst B component containing at least one element selected from the group consisting of n, Fe, Co, Ni, Ag, Au, Pt, Pd and Rn, the catalyst is heated and adsorbed. A deodorizing method in a freezer / refrigerator, which is characterized in that an operation of catalytically oxidizing and removing the odor components thus produced is repeatedly carried out. 2. A group in which the catalyst A component comprises a binary complex oxide composed of Ti and Si, a binary complex oxide composed of Ti and Zr, and a ternary complex oxide composed of Ti, Si and Zr. The method for deodorizing in a freezer / refrigerator according to claim 1, which is at least one kind of complex oxide selected from the group consisting of: 3. The deodorizing method in a freezer / refrigerator according to claim 1, wherein a heater for defrosting is used as a heating source for the catalyst. 4. The deodorizing method in a freezer / refrigerator according to claim 1, wherein the catalyst has a shape in which through holes are formed along the gas flow direction.