JP2007209833A - Catalyst material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, to convert acetaldehyde to acetic acid at ordinary temperature with a catalyst material using cobalt oxide, removal of low-concentration acetaldehyde in a concentration of ≤10 ppm e.g. in smell of tobacco, requires raising of the catalytic temperature because, depending largely upon the concentration of acetaldehyde, the catalyst material exerts only a low or no activity in concentrations of ≤10 ppm, leading to a large scale of removal equipment. <P>SOLUTION: A catalyst material 1 consists of a catalyst 21 containing cobalt oxide and a substrate 22. The catalyst material 1 after being washed with an acidic solution can convert low-concentration acetaldehyde to acetic acid at ordinary temperature and enables making harmless or removing acetaldehyde with a simple device. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a catalyst body that converts harmful acetaldehyde into harmless acetic acid by oxidation.

  Acetaldehyde is a harmful substance with carcinogenic properties, but it is hardly adsorbed on activated carbon and zeolite, which are common adsorbent materials. To remove it, either complete decomposition using a catalyst body or harmless acetic acid A means for converting and adsorbing to the adsorbing material is conceivable.

As a conventional catalyst body of this type, a catalytic material such as a transition metal oxide or a noble metal is applied to, or impregnated on, supported on a substrate such as a honeycomb body, and heated to a temperature at which catalytic activity is exhibited, and contains acetaldehyde. In general, air is used by ventilation (see, for example, Patent Document 1). According to the experiments by the inventors, it has been found that the one using cobalt oxide as the catalyst material has the lowest activation temperature, has activity near normal temperature, and is converted to acetic acid.
JP-A-6-157396

  However, according to experiments by the inventors, it has been found that even in a catalyst body using a cobalt oxide, concentration dependence is large when converting acetaldehyde to acetic acid at room temperature. Specifically, acetaldehyde can be converted to acetic acid with high efficiency at a high concentration of 100 ppm or more, whereas it was revealed that the activity is low or does not develop at a low concentration of 10 ppm or less.

  Therefore, to remove a low concentration of acetaldehyde of 10 ppm or less contained in tobacco odor or the like, it is necessary to raise the catalyst temperature, and when considered as a removal device, the scale becomes large.

  The catalyst body of the present invention solves the above-mentioned conventional problems, and provides a catalyst body that can be rendered harmless or removed by a simple apparatus by converting a low concentration of acetaldehyde to acetic acid at room temperature. For the purpose.

  In order to solve the conventional problems, the catalyst body of the present invention is a catalyst body comprising at least a cobalt oxide-containing catalyst and a base material, and the catalyst body is washed with an acidic solution to obtain a surface state of the catalyst body. As a result, a low concentration of acetaldehyde can be converted into acetic acid at room temperature, so that it can be rendered harmless or removed by a simple apparatus.

  Since the catalyst body of the present invention can convert a low concentration of acetaldehyde to acetic acid at room temperature, it can be rendered harmless or removed by a simple apparatus.

  According to a first aspect of the present invention, in a catalyst body composed of a catalyst containing at least a cobalt oxide and a base material, the surface state of the catalyst body is modified by washing the catalyst body with an acidic solution, and a low concentration of acetaldehyde at room temperature. Can be converted to acetic acid, so that it can be rendered harmless or removed by a simple apparatus.

  In the second invention, particularly in the catalyst body of the first invention, the cobalt oxide contains cobalt tetroxide, so that a low concentration of acetaldehyde can be more reliably converted to acetic acid at room temperature.

  In the third aspect of the invention, in particular, in the catalyst body of the first or second aspect of the invention, the acidic solution is an aqueous solution containing sulfuric acid, and similarly, a low-concentration acetaldehyde can be more reliably converted to acetic acid at room temperature. .

  In the fourth aspect of the invention, in particular, in the aqueous solution containing sulfuric acid of the third aspect of the invention, the concentration of sulfuric acid is in the range of 0.01% to 10%. Can be converted to

  In the fifth invention, in particular, in the catalyst bodies of the first to fourth inventions, acetic acid converted from acetaldehyde can also be removed because the base material contains an adsorbing material.

  In the sixth invention, in particular, in the catalyst body of the fifth invention, the adsorbing material contains any one of zeolite, silica, alumina, and activated carbon, so that acetic acid converted from acetaldehyde can be removed more reliably. Can do.

  In the seventh aspect of the invention, in particular, in the catalyst bodies of the first to sixth aspects of the present invention, the base material has a breathable shape, whereby an acetaldehyde removal apparatus can be configured with simple means.

  In the eighth aspect of the invention, in particular, in the catalyst body of the seventh aspect of the invention, the shape of the base material having air permeability is a honeycomb shape, so that an acetaldehyde removing device with high efficiency and low pressure loss can be configured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a perspective view showing the configuration of the catalyst body in the first embodiment of the present invention. In FIG. 1, a catalyst body 1 is configured by supporting cobalt oxide as a catalyst material on the surface of a honeycomb-shaped base material in which flat portions and corrugated plate portions are alternately laminated.

  FIG. 2 shows an enlarged cross-sectional view of FIG. As shown in FIG. 2, the catalyst body 1 is configured by supporting cobalt oxide 22 as a catalyst material on the surface of a honeycomb-shaped base material 21.

  In the present embodiment, the base material 21 constituting the honeycomb is not specified for the material of the base material 21, but here, a base material made from inorganic fibers using silica and alumina as raw materials is used. Yes.

  The cobalt oxide 22 used here is obtained by pulverizing a precipitate produced by dropping sodium hydroxide into an aqueous solution of cobalt nitrate through suction filtration and washing, and firing at 300 ° C. ing.

  As a result of analyzing this cobalt oxide, 90% or more of cobalt tetroxide was occupied.

  The catalyst body 1 was immersed and washed in a sulfuric acid aqueous solution adjusted to a concentration of 0.5% for 1 hour and then dried at 130 ° C.

  Here, an experiment was conducted to examine the function of the catalyst body in the present embodiment.

  As the evaluation gas, acetaldehyde was used, the acetaldehyde was adjusted to 10 ppm, and the aeration test was conducted at room temperature at a space velocity of 12000 / h. As a control experiment 1, a similar experiment was performed on a catalyst body that was not treated with a sulfuric acid solution. The experimental results are shown in FIG.

  FIG. 3 is an experimental characteristic diagram showing the change with time of the concentration of acetaldehyde and acetic acid at the outlet when acetaldehyde was vented at 10 ppm. The solid line is acetaldehyde and the broken line is acetic acid.

  In FIG. 3, in this embodiment, acetaldehyde is stable at about 6 ppm at the outlet concentration after about 30 minutes, and acetic acid was not confirmed in the initial stage, but is generated after 1 hour from the start of aeration. When 4 hours or more passed, about 6 ppm of acetic acid was produced, and the conversion was stable at about 60%. On the other hand, in Control Experiment 1, the outlet concentration of acetaldehyde almost monotonously decreased, and no acetic acid was generated after 8 hours.

  In this embodiment, acetaldehyde is converted into acetic acid by the catalytic action of cobalt oxide when acetaldehyde is passed in this embodiment. Adsorbed to the material. Thereafter, acetaldehyde is stably converted and removed after adsorption breakthrough. Acetic acid is adsorbed on the base material for a longer time than acetaldehyde, but eventually shows that it breaks through adsorption.

  On the other hand, in Control Experiment 1, the cobalt oxide that was not washed with acid was not modified in surface state and had low catalytic activity, so that acetaldehyde was not converted into acetic acid and could only be removed by adsorption. It is done.

  As described above, in the present embodiment, the sulfuric acid aqueous solution in which the catalyst body 1 supported on the honeycomb base material is adjusted to a concentration of 0.5% using the cobalt oxide containing cobalt trioxide as a main component as the catalyst material. 1 hour soaking and drying at 130 ° C. can convert the low-concentration acetaldehyde into acetic acid and constitute a catalyst body.

  Next, the concentration of sulfuric acid to be immersed was changed from 0.001% to 50% to prepare a catalyst body, and a similar experiment was performed. The experimental results are shown in FIG. In FIG. 4, 24 hours after the start of distribution, the stable conversion rate is plotted against the sulfuric acid concentration.

  As shown in FIG. 4, the conversion rate has a peak with respect to the sulfuric acid concentration, and at a concentration lower than 0.01% or higher than 10%, the conversion rate decreases and the activity is low.

  As described above, acetaldehyde can be reliably converted to acetic acid at room temperature by setting the concentration of sulfuric acid to be washed to a range of 0.01% to 10%.

  Further, in addition to sulfuric acid, an acidic solution was washed with a 0.5% aqueous solution of nitric acid, hydrochloric acid, and acetic acid, and the same experiment was performed. The conversion after 24 hours was 0% untreated, 60% sulfuric acid, 15% nitric acid, 5% hydrochloric acid, and 20% acetic acid.

  As described above, acetaldehyde can be converted to acetic acid with high efficiency by using sulfuric acid as the acidic solution.

Further, an experiment was conducted using a pulverized cobalt oxide fired at 200 ° C. As a result of analyzing this cobalt oxide, cobalt trioxide (Co ₃ O ₄ ) was hardly present, and cobalt oxide (CoO) accounted for 90% or more. The conversion rate to acetic acid after 24 hours was 30%, and the conversion rate was lower than the conversion rate of 60% when the cobalt trioxide was the main catalyst. .

  Thus, by containing tribasic cobalt tetroxide as a cobalt oxide, it becomes possible to more reliably convert a low concentration of acetaldehyde to acetic acid at room temperature.

(Embodiment 2)
FIG. 5 shows an enlarged cross-sectional view of the catalyst body in the second embodiment of the present invention. As shown in FIG. 5, the catalyst body is configured by supporting cobalt oxide 52 as a catalyst material on the surface of a honeycomb-shaped substrate 51.

  In the present embodiment, the base material 51 constituting the honeycomb is obtained by kneading zeolite as an adsorbing material with a binder such as clay, molding by extrusion, and firing.

  Similarly, the cobalt oxide 52 used here is obtained by pulverizing a precipitate formed by dropping sodium hydroxide into an aqueous solution of cobalt nitrate through suction filtration and washing, and firing at 300 ° C. Used.

  Similarly to Embodiment 1, the above catalyst body was immersed and washed in a sulfuric acid aqueous solution adjusted to a concentration of 0.5% for 1 hour and then dried at 130 ° C.

  Here, an experiment was conducted to examine the function of the catalyst body in the present embodiment.

  Similarly, aeration tests were conducted at room temperature by adjusting acetaldehyde to 10 ppm and setting the space velocity to 12000 / h.

  FIG. 6 is an experimental characteristic diagram showing the change over time in the concentration of acetaldehyde and acetic acid at the outlet when acetaldehyde was vented at 10 ppm. The solid line is acetaldehyde and the broken line is acetic acid.

  In FIG. 6, in the present embodiment, acetaldehyde was stable at about 6 ppm when about 2 hours passed, and acetic acid was not generated even after 24 hours from the start of aeration.

  Thus, the acetic acid converted from acetaldehyde can also be removed by containing the adsorption material in the base material.

  Here, zeolite is used as the adsorbing material, but acetic acid converted from acetaldehyde can also be removed by using an adsorbing material such as silica, alumina, activated carbon and the like.

  As described above, since the catalyst body according to the present invention can convert low-concentration acetaldehyde into acetic acid, it can be applied to business use in addition to household deodorizers and air purifiers.

The perspective view which shows the structure of the catalyst body in Embodiment 1 of this invention. The expanded sectional view of the catalyst body in Embodiment 1 of this invention Experimental characteristic diagram showing outlet concentrations of acetaldehyde and acetic acid in Embodiment 1 of the present invention Experimental characteristic diagram showing relationship between sulfuric acid concentration and conversion rate in Embodiment 1 of the present invention The expanded sectional view of the catalyst body in Embodiment 2 of this invention Experimental characteristic diagram showing outlet concentrations of acetaldehyde and acetic acid in Embodiment 2 of the present invention

Explanation of symbols

1 catalyst body 21 base material 22 catalyst (cobalt oxide)
51 Base material (extruded base material of zeolite)
52 Catalyst (Cobalt oxide)

Claims (8)

A catalyst body composed of a catalyst containing at least a cobalt oxide and a base material, the surface of which is modified by washing with an acidic solution. The catalyst body according to claim 1, wherein the cobalt oxide is a cobalt oxide containing tribasic cobalt oxide. The catalyst body according to claim 1 or 2, wherein the acidic solution is an aqueous solution containing sulfuric acid. The catalyst body according to claim 3, wherein the aqueous solution containing sulfuric acid is an aqueous sulfuric acid solution having a concentration in the range of 0.01% to 10%. The catalyst body according to any one of claims 1 to 4, wherein the base material contains an adsorbing material. The catalyst body according to claim 5, wherein the adsorbing material contains any one of zeolite, silica, alumina, and activated carbon. The catalyst body according to any one of claims 1 to 6, wherein the substrate is a substrate having a shape having air permeability. The catalyst body according to claim 7, wherein the shape having air permeability is a honeycomb shape.