JPH0373336B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention selectively oxidizes carbon monoxide (hereinafter referred to as CO) in gas and converts it into non-toxic carbon dioxide (hereinafter referred to as CO ₂ ).
The present invention relates to a method for producing an oxidation catalyst for converting into. [Prior Art] CO, which is produced by the incomplete combustion of carbon compounds such as carbon and hydrocarbons, is one of the most toxic air polluting gases. CO has a strong binding force with hemoglobin in the blood, which plays a role in absorbing and transporting oxygen (hereinafter referred to as O ₂ ) (200-300% of the binding force of O ₂ ).
For this reason, when the human body is exposed to high concentrations of CO, it causes acute poisoning due to lack of oxygen in the central tissues, and even death. Also, low concentration
Long-term exposure to CO is said to cause heart disease. For this reason, we are developing methods to prevent air pollution from automobile exhaust gas, indoor pollution from heating equipment exhaust gas and smoking, and CO2 contained in environmental gases for safety in the event of explosions or fires at mines.
There is a strong desire to establish a method to reduce the concentration. The CO removal methods proposed so far are (1)
Adsorb to adsorbent, (2) Absorb to absorbent, (3)
It can be roughly divided into three methods: converting it into non-toxic CO ₂ using an oxidizing agent or an oxidizing catalyst. As method (1), a method using a porphyrin metal complex as an adsorbent (Japanese Patent Publication No. 54-22951)
There are methods that use a combination of activated carbon and molecular sieves (U.S. Pat. No. 3,658,069), but the former has the disadvantage that the CO adsorption rate is relatively slow, and the latter has the disadvantage that CO adsorption and desorption occur quickly at the same time. The disadvantage is that it cannot be removed sufficiently. An example of method (2) is the Kosorb method (West German Patent No. 1944405), in which CO is absorbed into a toluene solution of cuprous chloride and aluminum chloride complex;
No. 2414801) and a copper solution cleaning method using a copper ammine complex ion solution are known, but the former loses CO absorption activity due to trace amounts of water.
The latter has the disadvantage that the copper() ions are easily oxidized and lose CO absorption activity.
For this reason, both require large-scale devices and are subject to many restrictions in use. As an example of (3), the oxidation catalyst hobcalite, which mainly consists of manganese dioxide and cupric oxide, has been known for a long time, and this catalyst has high CO oxidation activity even at room temperature or lower. Since it easily loses its activity due to trace amounts of moisture, it is inconvenient that it must be stored in a sealed container and that the gas to be treated must be completely dried before use. On the other hand, many metals or metal compounds are known as catalysts for oxidizing CO to CO ₂ .
Most of them lose their activity in a temperature range considerably higher than room temperature, and are easily deactivated by moisture in the gas. Although a small portion of precious metals such as platinum and palladium have CO oxidation activity at room temperature and remain relatively stable in the presence of moisture, the activity itself is extremely low. [Problems to be Solved by the Invention] In view of the above circumstances, an object of the present invention is to develop a new highly active material that effectively exhibits CO oxidation activity even at room temperature, and which is cheaper and easier to manufacture than platinum, palladium, etc. An object of the present invention is to provide a method for producing a CO oxidation catalyst. [Means for Solving the Problems] As a result of intensive research to solve the above problems, the present inventor impregnated manganese dioxide powder with an aqueous solution of an inorganic acid or an organic acid salt of cobalt, ruthenium, or nickel, and obtained carbon dioxide. They discovered that a catalyst produced by adsorbing the metal salt on the surface of manganese, drying it, and then treating it with an aqueous solution of potassium permanganate (hereinafter referred to as KMnO ₄ ) was well suited for the purpose, and led to the completion of the present invention. Ivy. Hereinafter, the method for producing the carbon monoxide oxidation catalyst of the present invention will be explained in detail. Manganese dioxide that can be used in the present invention can be prepared by the electrolytic oxidation method of divalent manganese salt, or by the method of preparing it from divalent manganese salt and KMnO ₄ under alkaline conditions (J. Atztenbrough et al. J. Chem. Soc. 1094).
(1952)), the method prepared under nitric acid acidity (J. Tolman British Patent No. 1315374) and the method prepared from a neutral solution (S. Ball Biochem. J.42, 516).
(1948)). Moreover, it is preferable to crush and classify the prepared manganese dioxide and use one having a particle size of 20 to 60 mesh. This powdered manganese dioxide, cobalt,
It is impregnated with an aqueous solution of an inorganic or organic acid salt of ruthenium or nickel, preferably an aqueous solution of hydrochloride, nitrate, sulfate, or acetate. These metal salts may be used as a single aqueous solution or as a mixed solution of two or more types. The water from this manganese dioxide impregnated solution is distilled off under reduced pressure, and the metal salt is adsorbed onto the surface of the manganese dioxide.
Dry at 110°C overnight. The adsorption amount of this metal salt is 0.1 to 20 in terms of metal.
% range, and a metal salt corresponding to this amount is dissolved in advance in the aqueous solution. The metal salt-supported manganese dioxide obtained in this way is impregnated with an aqueous KMnO ₄ solution, preferably saturated KMnO ₄ , and oxidized for 5 to 30 minutes, preferably 10 minutes. After filtering, permanganate ions are removed with distilled water. Wash until pink color is no longer recognized. Thereafter, the carbon monoxide oxidation catalyst of the present invention can be obtained by drying at 110° C. overnight. This oxidation catalyst can be used in a suitable shape by further adding a suitable binder such as CMC or compression molding. [Examples] Hereinafter, the present invention will be explained in more detail based on Examples. However, the description of these examples is not intended to limit the scope of the invention. Example 1 50 g of manganese nitrate hexahydrate was dissolved in 300 ml of distilled water, and 50 g of concentrated nitric acid was added thereto. 50g separately
of KMnO ₄ was dissolved in 21 parts of distilled water, and while stirring this solution, the previously prepared aqueous solution of nitric acid and manganese nitrate was gradually added. The mixture was left to stand for 10 minutes with stirring, and the produced manganese dioxide was washed by a decanting method, and further washed with distilled water while filtering with suction until the filtrate became almost colorless. then 110
After drying at ℃ overnight, 25 g of the obtained lump-like manganese dioxide was crushed, and 20 to 60 pieces were separated. This manganese dioxide was immersed in 8 ml of an aqueous solution containing 5 mg of cobalt chloride hexahydrate/ml, water was distilled off under reduced pressure, and the mixture was dried at 110° C. overnight. The thus obtained cobalt chloride-supported manganese dioxide is further saturated.
It was immersed in 10 ml of KMnO ₄ aqueous solution, left for 10 minutes, filtered, and washed with distilled water until the pink color of permanganate ions was no longer observed. Next, it was dried at 110° C. overnight to obtain a catalyst supporting 1.0 wt % of cobalt in terms of metal. Using the same procedure as this, as metal cobalt, 0.02, 0.2, 2.0, 4.0, 6.0, 8.0, 10.0,
Catalysts supporting 12.0, 14.0, and 14.0 wt% of cobalt were prepared. Using 200 mg of each of these catalysts, the CO removal rate was measured according to the following procedure. Fill a glass tube with the catalyst and press both ends of the packing with glass wool. While flowing helium as a carrier gas through this glass tube, reactant gases (CO5%, O ₂ 4%,
CH4 ₄ %, He87%) pulses for 10 minutes at room temperature (22°C)
Give ml. The gas that has passed through the glass tube is led directly to a gas chromatograph to analyze the gas components. The results are shown in Figure 1, and the average CO reduction rate of each catalyst is shown in Figure 2. Oxidizers with cobalt additions ranging from 2.0 to 8.0 wt% are CO highly active, and they have an average of 90
% CO removed. Example 2 4 g of commercially available manganese dioxide produced by electrolytic oxidation method was immersed in 25 ml of an aqueous solution containing 100 mg of cobalt chloride hexahydrate, and water was distilled off under reduced pressure. Following the same procedure as in Example 1, KMnO ₄
After treatment, washing and drying, 200 mg of the obtained catalyst
was subjected to a pulse test. As seen in Table 1, the obtained catalyst showed high CO oxidation activity.

[Table] Example 3 The manganese dioxide obtained in Example 1 was impregnated with 45.5 ml of an aqueous solution containing 5 mg ruthenium chloride/ml, and water was distilled off under reduced pressure. Next, a catalyst was prepared in the same manner as in Example 1 to obtain a catalyst supporting 1.0 wt% of ruthenium. In addition, several types of catalysts supporting ruthenium in a range of 0.02 to 25.0 wt% were prepared in the same manner. A pulse test was conducted on 200 mg of each of the catalysts obtained, and the results were as shown in FIGS. 3 and 4. The optimal ruthenium addition rate for CO oxidation is 12.0~
The CO removal rate was 14.0wt%, and the CO removal rate was about 40%. Example 4 By the same method except that nickel chloride was used instead of cobalt chloride hexahydrate in Example 1,
Ten types of catalysts with nickel supported ranging from 0.02 to 14.0 wt% were prepared. 200 mg of each of these catalysts was subjected to a pulse test, and the results shown in FIGS. 5 and 6 were obtained.
Nickel addition rate suitable for CO oxidation is 4.0 to 8.0wt%
The CO removal rate of the 6.0wt% catalyst was 35%. Example 5 20 g of anhydrous manganese sulfate was dissolved in 100 ml of water, and while stirring, 300 ml of distilled water in which 10 g of KMnO ₄ and 5 g of sodium hydroxide had been dissolved was gradually added. The resulting blackish brown precipitate was filtered by suction filtration, and further washed with distilled water until the filtrate became almost colorless. Next, this was dried at 110°C overnight to obtain manganese dioxide powder. Take 1 g of this, impregnate it with 16 ml of an aqueous solution containing 5 mg cobalt chloride hexahydrate/ml, and proceed in the same manner as in the example.
After KMnO ₄ treatment, washing, and drying, a catalyst containing 2.0 wt% cobalt was obtained. Table 2 shows the results of a pulse test performed on 200 mg of this catalyst.

[Table] Example 6 Various catalysts were produced in the same manner except that cobalt nitrate hexahydrate, ruthenium sulfate, and nickel acetate tetrahydrate were used in place of the cobalt chloride hexahydrate used in Example 1. did. 200mg of each catalyst
was subjected to a pulse test, and the results shown in Table 3 were obtained.
It can be seen that inorganic or organic acid salts other than hydrochloride have similar high CO oxidation activity.

[Table] [Effects of the Invention] The carbon monoxide oxidation catalyst produced by the production method of the present invention has high catalytic activity even at room temperature, has very little deactivation due to the presence of moisture, and has stable catalytic activity. This makes it possible to oxidize carbon monoxide to harmless carbon dioxide more effectively than conventional catalysts.

[Brief explanation of drawings]

Figure 1 is a graph of pulse test results for a cobalt-manganese dioxide catalyst, Figure 2 is a graph of the average CO reduction rate for a cobalt-manganese dioxide catalyst, and Figure 3 is a graph of the average CO reduction rate for a ruthenium-manganese dioxide catalyst. This is a graph of the pulse test results, and Figure 4 shows the average CO of the ruthenium-manganese dioxide catalyst.
Figure 5 is a graph of the reduction rate; Figure 5 is the pulse test result of the nickel-manganese dioxide catalyst; Figure 6 is the graph of the reduction rate;
The figure is a graph of the average CO reduction rate of nickel-manganese dioxide.

Claims (1)

[Claims] 1. A method characterized in that manganese dioxide is impregnated with an aqueous solution of an inorganic or organic acid salt of a metal selected from the group consisting of cobalt, ruthenium, and nickel, and then oxidized with potassium permanganate. A method for producing a carbon oxide oxidation catalyst. 2. The inorganic or organic acid salt of a metal selected from the group consisting of cobalt, ruthenium, and nickel is a salt of an acid selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, and acetic acid. A method for producing a carbon monoxide oxidation catalyst.