JPS6251135B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a catalyst for purifying harmful gases. To explain more specifically, carbon monoxide (CO), hydrocarbons (HC), sulfur dioxide (SO ₂ ), nitrogen oxides ( _NO The object of the present invention is to provide an economical and highly practical catalyst consisting of manganese slag alone or a binder together with manganese slag, which is produced as a by-product during the production of potassium permanganate and has the activity of purifying gases containing harmful substances. It is something. Typical catalysts that have been proposed to purify gases containing harmful substances such as carbon monoxide, hydrocarbons, carbon dioxide, sulfur dioxide, and nitrogen monoxide contained in exhaust gas from internal combustion engines, combustion gas from heating equipment, etc. Examples of such things include the following: First, electrolytic manganese dioxide (γ-
MnO ₂ ), iron oxyhydroxide (FeOOH), and those whose main components are basic copper carbonate, such as manganese oxide,
Products prepared by mixing iron oxide, copper oxide, etc. in combination with alumina cement, curing in water and steam, and then heat treating at 350 to 600°C for about 5 hours (Japanese Patent Application Laid-open No. 54-26984), and the above-mentioned products. There is a method of using a catalyst whose surface is coated with a platinum group metal such as platinum, palladium, ruthenium, or rhodium (Japanese Unexamined Patent Publication No. 142993/1983). However, the above method requires the use of expensive platinum group metal oxides, water and steam curing, high-temperature heat treatment, etc., resulting in a complicated process and high cost. Furthermore, the usage temperature range (250 to 650℃) of the obtained catalyst is limited;
When the temperature exceeds ℃, the purifying effect is rapidly lost. Furthermore, although the above-mentioned method can oxidize carbon monoxide and hydrocarbons by using a noble metal catalyst such as platinum or palladium, it is expensive and susceptible to catalyst poisoning. As a result of intensive research to eliminate the drawbacks of conventional catalysts, the present invention has developed an economical catalyst that maintains high activity in a wide temperature range from low to high temperatures, has excellent mechanical strength and wear resistance. The present invention was completed based on the discovery that manganese slag, which is a by-product during the production of potassium permanganate, is suitable as a catalyst for purifying harmful gases. That is, the present invention is a catalyst for purifying harmful gases made by molding manganese slag alone or the manganese slag and a binder, which are produced as a by-product during the production of potassium permanganate. The manganese slag used in the present invention is produced by adding caustic potassium to manganese ore, oxidizing and roasting it while passing air to create potassium manganate, which is extracted with water and electrolytically oxidized to produce potassium permanganate. It is produced as a by-product as an extraction residue. The composition of this manganese slag is shown in Table 1 of the main body.

[Table] However, % indicates weight %, and composition is indicated as oxide. Harmful gases purified by manganese slag with this composition include carbon monoxide, hydrocarbons,
These harmful gases include sulfur dioxide and nitrogen oxides, and the manganese slag of the present invention acts as an oxidation catalyst to render these harmful gases harmless.The mechanism of action is as follows. The reason for the significant reduction in carbon monoxide (CO) contained in harmful gases is that it is contained in manganese slag.
MnO ₂ , Fe ₂ O ₃ , Al ₂ O ₃ , SiO _{2 ,} etc. are oxidized and roasted in the presence of caustic potassium in the highly oxidizing atmosphere of the potassium permanganate production process, and then moderately hydrolyzed, so each This is thought to be because it becomes an active oxyhydroxide, which exerts a catalytic action together with slaked lime and part of the caustic potassium added during the production of potassium permanganate, thereby oxidizing carbon monoxide to carbon dioxide gas (CO ₂ ). Hydrocarbons such as ethylene contained in harmful gases can be considered in the same way as carbon monoxide. Sulfur dioxide (SO ₂ ) contained in harmful gases reacts with slaked lime [Ca(OH) ₂ ] in manganese slag, calcium carbonate (CaCO ₃ ), and oxygen (O ₂ ) in the air to form calcium sulfate (CaSO ₄ ). becomes. Ca(OH) ₂ ＋SO ₂ ＋1/2O ₂ ＝CaSO ₄ ＋H ₂ O CaCO ₃ ＋SO ₂ ＋1/2O ₂ ＝CaSO ₄ ＋ _CO 2Nitric oxide (NO) contained in harmful gases is manganese dioxide ( It is thought that it reacts with MnO ₂ ) and oxygen (O ₂ ) in the air to form manganese nitrate [Mn(NO ₃ ) ₂ ]. 2NO + MnO ₂ + O ₂ = Mn (NO ₃ ) ₂ Each component in the above composition of manganese slag acts as an oxidation catalyst for carbon monoxide and hydrocarbons, and acts to fix sulfur dioxide and nitrogen monoxide through chemical reactions. The present invention is characterized by quantitatively rendering the harmful gas harmless, and in order for this effect to be carried out effectively, it is necessary that the composition of the manganese slag falls within the range shown in Table 1, If it deviates from this range, the effects of the present invention cannot be expected. The manganese slag used in the present invention originally has a particle size of
Since it is a colloid with a size of 0.1 to 0.001μ, it is fine and has a large specific surface area, making it advantageous as a catalyst. Therefore, it can be used as a raw material as it is, or it can also be used as a raw material after drying and pulverizing. In this case, it is necessary to pulverize it to eliminate the influence of secondary solidification, and it is preferable to use it after pulverizing it to 60 meshes or less. However, depending on the purpose of use, fine powdered manganese slag has low mechanical strength, so a binder is added to give it strength, and by molding and drying it, it can be shaped into spheres, pellets, rods, or honeycombs. By processing it into various shapes, it is possible to produce catalysts with excellent catalytic performance, longevity, and mechanical strength. Binder used in the present invention includes naturally produced bentonite, acid clay, kaolinite,
Clay minerals such as various clays, cements such as alumina cement, blast furnace cement, and Portland cement, silicic acid, silica sand, tobermorite, belmolite,
One or a mixture of two or more selected from zeolite, silicic acid or its salt such as allofene, slaked lime, alkaline earth metals such as magnesium hydroxide, gypsum, diatomaceous earth, and alumina is used. Among the above-mentioned various binders, clayey ones such as bentonite and acid clay are particularly effective in improving the formability and mechanical strength of the catalyst, extending the life of the catalyst, and increasing the surface area. Therefore, alumina cement is preferable because its action is as good as that of clay, and it also has a large thermal strength. The catalyst of the present invention is produced by mixing fine manganese slag, which is produced as a by-product during the production of potassium permanganate, with a binder, and kneading the mixture with water. It can be easily obtained by molding into a desired shape such as a honeycomb shape and drying. The catalyst of the present invention is made from 50 to 100% by weight of manganese slag.
It is preferable to use a compound in which the balance is made up of a binder, and if the amount of manganese slag is less than 50% by weight, the purification performance of the harmful gas tends to deteriorate, which is not preferable. The thus obtained catalyst for purifying harmful gases of the present invention has excellent temperature characteristics and can maintain high catalytic activity over a wide range of temperatures. in carbon
150 to 1000℃ or more, 150 to 1000℃ for hydrocarbons
As mentioned above, the removal rate is good at room temperature to 1000°C or higher for sulfur dioxide and 70 to 100% for nitrogen oxide (NO _x ) at 70 to 480°C in both cases. The effects of the present invention will be listed below. (1) Conventional harmful gas purification catalysts (oxidation catalysts) had to use expensive metal oxides and precious metals, but the present invention eliminates the by-product manganese produced during the production of potassium permanganate. It is extremely economical and highly practical because slag can be used effectively. (2) Production of catalyst After molding, there is no need for special curing or heat treatment, and it can be easily produced and does not require advanced technology. (3) In terms of catalytic performance, the removal effect of carbon monoxide, hydrocarbons, sulfur dioxide, nitrogen monoxide, etc. contained in harmful gases is effective over a wide range from low temperatures to high temperatures, and the applicable temperature range is wide. (4) Even when used at high temperatures, no collapse or deterioration of the catalyst itself is observed, and there is almost no concern about contamination of reactants. (5) There is little deterioration in catalyst performance even after reuse, and it can be used repeatedly. (6) Contact purification of harmful components such as carbon monoxide, hydrocarbons, sulfur dioxide gas, and nitrogen oxide ( _NO can be converted into a harmless gas. EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto. Example 1 250g of by-product manganese slag dried and crushed to 60 mesh or less, naturally produced bentonite 28
g and 140 ml of water were collected, mixed well, and granulated into a size of 3 mm in diameter x 10 to 20 mm in length using a push-pull molding machine, and then dried and adjusted at 120° C. for about 10 hours. The strength of each cylindrical granule is 5.5
Kg/particle. The above catalyst granules were placed in the catalyst filling part 2 of the combustion tube 1 of the catalyst testing apparatus shown in FIG.
ml, fix both ends with glass wool 3,
A combustion tube filled with a catalyst is installed in a horizontal heating furnace 4, and while being heated to a constant temperature, sample gas is diluted with atmospheric gas from an air pump 6 from a standard gas cylinder 5 and supplied at a constant flow rate via a flow meter 7. It was brought into contact with a heated catalyst body, converted, and discharged from the system. A portion of the gas was introduced into an analyzer (not shown) through a silicone rubber tube through a gas inlet 8 and a gas outlet 9, and the concentration of each gas was analyzed using a switch 10 to measure the removal rate. In this case, the space velocity Sv (Hr ^-1 ) of the processing gas was kept constant, and the reaction temperature was selected from room temperature to 1000°C to find the relationship between temperature and removal rate. Figure 2 shows the removal rate at various temperatures when air containing carbon monoxide at an inlet concentration of 750 ppm was used as the supply gas. Figure 3 shows the removal rate at various temperatures when air containing ethylene at an inlet concentration of 100 ppm was used as the supply gas. Figure 4 shows the removal rate at various temperatures when air containing sulfur dioxide at an inlet concentration of 100 ppm was used as the supply gas. Figure 5 shows the removal rate at various temperatures when air containing nitrogen monoxide at an inlet concentration of 50 ppm was used as the supply gas. In FIGS. 1 to 5, curve A represents Example 1.
This is the result. Comparative Example 1 A cylindrical granule was prepared in the same manner as in Example 1 using only naturally produced bentonite as a raw material without using the by-product manganese slag as an active component of the catalyst, and the same catalyst test equipment as in Example 1 was used. The relationship between temperature and removal rate is shown in curve B of FIGS. 2 and 4. Note that the inlet concentration of the supply gas was the same as in Example 1. As a result, it was found that using manganese slag was more effective in removing harmful substances. Example 2 After kneading only the by-product manganese slag with water, cylindrical granules were prepared in the same manner as in Example 1 to prepare a catalyst. Using this catalyst, a purification test was carried out on a feed gas containing carbon monoxide as a harmful gas component and having the same inlet concentration as in Example 1. The relationship between temperature and removal rate is shown in curve C in FIG. Example 3 A mixture of secondary manganese slag, which is the same raw material used in Example 1, and naturally produced bentonite as a binder, in a weight ratio of 5:5, was kneaded with water and then cylindrically granulated. I made a catalyst by adjusting things. Using this catalyst, a purification test was carried out on a feed gas containing carbon monoxide as a harmful gas component and having the same inlet concentration as in Example 1. The relationship between temperature and removal rate is shown in curve D in Figure 2. Example 4 Alumina cement was used instead of the naturally produced bentonite used in Example 1, and a mixture of by-product manganese slag and alumina cement at a weight ratio of 2:1 was kneaded with water and then formed into a cylindrical shape. The catalyst was made by creating particles. The strength of each cylindrical granule is
It was 1.2Kg/particle. Using the same apparatus as in Example 1, the columnar granules were brought into contact with a supply gas containing carbon monoxide as a harmful component and having the same inlet concentration as in Example 1, to determine the relationship between temperature and removal rate. The results are shown in curve E in Figure 2. Example 5 A spherical catalyst with a diameter of 5 mm was prepared using the same catalyst components and raw materials in the same mixing ratio as in Example 4. This was brought into contact with a supply gas containing carbon monoxide as a harmful component and having the same inlet concentration as in Example 1 in the same manner as in Example 1, and the relationship between temperature and removal rate was determined.
Results similar to curve E in FIG. 2 were obtained. Example 6 A honeycomb-shaped catalyst was prepared using the same catalyst components and blending ratio as in Example 4. This was brought into contact with a supply gas containing carbon monoxide as a harmful component and having the same inlet concentration as in Example 1 in the same manner as in Example 1, and the relationship between temperature and removal rate was determined. Similar good results were obtained. After cooling, the temperature was raised again and the oxidation rate was determined, but the catalyst performance showed almost no deterioration and the reproducibility was good.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the catalyst test device for purifying harmful gases of the present invention, FIG. 2 is a graph showing the catalytic effect of the catalyst of the present invention showing the relationship between temperature and removal rate for carbon monoxide, and FIG. Figure 4 is a graph showing the catalytic effect showing the relationship between temperature and removal rate for ethylene, Figure 4 is a graph showing the catalytic effect showing the relationship between temperature and removal rate for sulfur dioxide, and Figure 5 is a graph showing the relationship between temperature and removal rate for nitrogen monoxide. It is a graph showing the catalytic effect showing the relationship between the removal rate. 1...Magnetic combustion tube, 2...Catalyst filling section, 3...
Glass wool for fixing catalyst, 4...Horizontal heating furnace, 5
...Standard gas cylinder, 6...Air pump, 7...
Flowmeter, 8...Gas inlet to the combustion tube, 9...Gas outlet from the combustion tube, 10...Switching switch for measuring inlet and outlet gas concentration.

Claims (1)

[Scope of Claims] 1. A catalyst for purifying harmful gases made by molding manganese slag alone or a binder with the manganese slag, which is produced as a by-product during the production of potassium permanganate. 2. Harmful gas purification according to claim 1, wherein the binder is one or more selected from clay minerals, cement, silicic acid or its salts, slaked lime, gypsum, diatomaceous earth, and alumina. catalyst. 3. The catalyst for purifying harmful gases according to claim 1 or 2, wherein the harmful gas is one or more selected from carbon monoxide, hydrocarbons, sulfur dioxide, and nitrogen oxides.