JPH0512981B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a method for producing a manganese dioxide-based carbon monoxide oxidation catalyst, and more particularly, to a method for producing a manganese dioxide-based carbon monoxide oxidation catalyst, and more particularly, to a method for producing a manganese dioxide-based carbon monoxide oxidation catalyst, and more particularly, to a method for producing a manganese dioxide-based carbon monoxide oxidation catalyst. This invention relates to a method for producing a manganese-based carbon monoxide oxidation catalyst. <Prior Art> Conventionally, a copper-supported manganese dioxide-based carbon monoxide oxidation catalyst has been well-known as a hopcalite catalyst. Such a catalyst is typically produced by mixing manganese dioxide and copper oxide and then firing the mixture;
There is a method of manufacturing by neutralizing a metal nitrate mixed solution containing at least manganese and copper to co-precipitate a metal hydroxide, and then performing an oxidation treatment. (Unexamined Japanese Patent Publication No. 1973-
(Japanese Patent Publication No. 116290) However, the catalyst produced by the former method has a heterogeneous system when viewed microscopically, and its catalytic performance is not satisfactory. On the other hand, the latter is an improvement over the former by obtaining a homogeneous system, but the life of the catalyst is not necessarily long. This is probably due to the fact that even if divalent manganese hydroxide is oxidized, it is difficult to substantially oxidize it to manganese dioxide. Furthermore, manganese dioxide produced by oxidizing manganese hydroxide has a very large bulk, so it has the disadvantage of low catalytic activity per unit volume. Furthermore, a method for producing a manganese dioxide-based oxidation catalyst has recently been proposed, which is produced by adding an alkaline solution containing an oxidizing agent and permanganate to a mixed solution of soluble salts of manganese and copper. (Japanese Unexamined Patent Application Publication No. 60-7940) In this method, the oxidation rate of manganese is higher than that of the method of oxidizing manganese hydroxide, and the oxidation rate of manganese is close to that of manganese dioxide. This seems to be an improved method in that it is supported by <Problems to be Solved by the Invention> Generally, a catalyst in which a copper compound is supported during the production of manganese dioxide is superior to a catalyst in which manganese dioxide and copper oxide are physically mixed. However, the catalytic performance varies greatly depending on the conditions for producing manganese dioxide and the conditions for supporting the copper compound, and conventional methods each have their own merits and demerits and are not satisfactory in terms of industrially reliable quality. isn't it. In particular, specific surface area is used to evaluate this kind of catalytic ability, but it varies greatly despite subtle differences in manufacturing conditions, and the catalytic ability of the same specific surface area differs. On the other hand, even if the initial catalytic ability is high, its life may be short, and conversely, even if its initial catalytic ability is relatively low, its life may be maintained for a long time up to a certain level. Therefore, the present invention provides an improved hopcalite catalyst with a long life and stable quality by a method completely different from the conventional method. <Means and effects for solving the problems> That is, the present invention provides a first step in which a mixed salt aqueous solution of manganese and copper is acidified with mineral acid to precipitate mixed salt crystals of manganese and copper, which is obtained from the previous step. The second step is to add potassium permanganate to the strongly oxidized slurry system and perform oxidation treatment to produce manganese dioxide.The third step is to separate the precipitate from the previous step from the mother liquor, and to neutralize the obtained precipitate with an alkaline agent. The present invention relates to a method for producing a manganese dioxide-based carbon monoxide oxidation catalyst (hereinafter abbreviated as a manganese dioxide-based oxidation catalyst), which is characterized by comprising a fourth step of performing a sum treatment. First Step As mentioned above, this step is a step of precipitating mixed salt crystals of manganese and copper. Manganese and copper salts, which are the starting materials, may be any soluble salts, typically sulfates or nitrates, and of course, these salts may be anhydrous or hydrated. good. In general, nitrates are more preferred than sulfates because the sulfur content remaining in the catalyst tends to poison the catalyst; however, in the present invention, sulfates can also be satisfactorily used. Further, as mineral acids which are other raw materials, sulfuric acid and nitric acid are typically used. Therefore, in this process, in consideration of the circulation use of the mother liquor as described later, in many cases the process is carried out using a sulfate-sulfuric acid or nitrate-nitric acid system, but from the viewpoint of catalytic performance, there is no reason to limit it to this system. do not have. It is known that nickel, cobalt, zinc, or silver is supported in addition to copper depending on the purpose of use of the catalyst or to further improve the catalytic ability. Depending on the situation, soluble salts thereof can be used in conjunction with copper salts to support copper. Such a mixed salt aqueous solution of manganese and copper acts with a mineral acid to make it acidic, so that the solubility of the manganese and copper salts decreases according to the acid concentration, and the mixed salts precipitate. When making mineral acid acidic,
The mineral acid may be added to the metal mixed salt aqueous solution or vice versa. For example, in the sulfate-sulfuric acid system, the solubility of manganese sulfate is
Metal-organic compounds, Seidell, Linke
This is clearly stated in Fourth Edition, Volume P.563. Thus, in this process, it is important to crystallize the mixed salt from the solution with mineral acid, and although it is preferable to precipitate a substantial amount of the metal salt in the raw material aqueous solution, it is not always necessary to precipitate the entire amount. There isn't. Here, the mixed salt that crystallizes is not necessarily defined strictly chemically, but broadly defined as crystals that precipitate from a mixed solution of manganese and copper salts due to the action of mineral acids. However, it does not matter whether the crystal is a double salt of manganese and copper or a mixed crystal as a solid solution. For example, A Comprehensive Treatise On
Inorganic And Theoretical chemistry Vol.12,
P.421-422; According to Mellor, in the case of sulfuric acid type, CuSO ₄・MnSO ₄・nH ₂ O (n=1 or 2)
When viewed as a double salt of (Cu・Mn)SO ₄・nH ₂ O
There is a report that a solid solution such as (n=5 or 7) is precipitated. Therefore, the mixed salt crystals in this process are probably
It is presumed that at least a portion of the salts are mutually solid-dissolved double salts, but such crystals are fine, and the present invention involves reacting with potassium permanganate in the next step in this crystalline state to produce manganese dioxide. It has the characteristics of That is, although the details of the reaction mechanism are unknown,
Catalytic ability can be stably improved by allowing potassium permanganate to act on mixed crystal particles of manganese and copper. Therefore, the blending ratio in the starting materials is related to the amount of copper to be supported on manganese dioxide and affects the catalytic ability, but in the present invention, the molar ratio Mn/
Cu is in the range of 1.4 to 14.0, particularly preferably in the range of 2 to 10. In addition, nickel, cobalt, zinc or silver salts are also available.
As mentioned above, a small amount can be mixed if necessary. Second Step This step is a step in which potassium permanganate is added to the strongly acidic slurry system obtained from the previous step to generate manganese dioxide. That is, in the first step, a strongly acidic slurry in which mixed crystals of manganese and copper are finely dispersed in a strongly acidic liquid is obtained. , manganese salts are converted to black-brown manganese dioxide to form a precipitate. The oxidation reaction in this step may be carried out at room temperature or with heating, but considering the reaction rate,
Heating at 60°C is preferred. Further, in order to carry out the oxidation reaction sufficiently, after the addition of potassium permanganate, the mixture is aged while stirring for a while. Although the details of the reaction system are unknown, it is likely that some copper ions are solidly dissolved in the manganese dioxide produced, and most of the other copper salts are adsorbed to the active manganese dioxide in the form of fine copper salt crystals. It is thought that they will co-precipitate. The amount of potassium permanganate to be added is around the theoretical amount at which manganese salt reacts with potassium permanganate to produce manganese dioxide, and preferably a slight excess. Either is fine. Third Step This step is a step in which the manganese dioxide-containing precipitate produced in the previous step is separated from the mother liquor. When separating, if it has been heated in the previous step, it is preferable to cool it and perform it at room temperature. The reason for this is to reduce the solubility of the copper salt, avoid copper ions from entering the mother liquor as much as possible, increase the yield of copper, and recycle the recovered mother liquor to the first step as a mineral acid source if necessary. It is. In this way, the separated mother liquor is a strongly acidic solution composed mainly of mineral acids, but also of potassium salts produced as by-products in the previous step and copper salts corresponding to the solubility. Therefore, it is industrially advantageous to recycle this mother liquor as a mineral acid source for dissolving or precipitating metal salts, but in this case, the temperature during separation and the mother liquor may be concentrated or diluted as necessary. By controlling its specific gravity, etc., it is possible to control its composition to a substantially constant composition and to recycle it. Furthermore, if the salt concentration increases due to the circulation of the mother liquor, it goes without saying that the potassium salt may be crystallized and separated as necessary. On the other hand, the precipitate is mainly composed of active manganese dioxide to which copper salts have been adsorbed, but it also has a high water content in which a considerable amount of mother liquor is also adsorbed. The separation operation may be carried out by any conventional means, such as centrifugation, filtration or decantation, as appropriate. Fourth Step This step is a step in which the separated and collected precipitate is neutralized with an alkaline agent. That is, the precipitate is dispersed in water and neutralized with caustic alkali or aqueous ammonia under stirring at room temperature or heating. This treatment not only neutralizes the acid content of the adhesion, but also converts the copper salt into a hydrous oxide and ensures that the copper is supported on the active manganese dioxide. PH is 9~
It is best to do this until you reach the 10 range. After the neutralization treatment, copper-supported manganese dioxide is obtained by separating and washing by a conventional method. The manganese dioxide-based oxidation catalyst thus produced can be used for desired purposes as an oxidation catalyst by drying if necessary, then kneading with a desired binder, molding, and drying. The manganese dioxide-based oxidation catalyst according to the present invention is
Analysis based on X-ray diffraction shows that it is substantially amorphous, porous with a specific surface area of at least 150 m ² /g or more, and highly oxidizing active, although this varies depending on the final form of the catalyst. Furthermore, the molar ratio (Mn/Cu) of copper supported on manganese dioxide is 0.9 to 9.0, preferably 1.5 to 9.0.
It's in the 7.5 range. Example 1 315 g of manganese sulfate (MnSO ₄ . H ₂ O) and 286 g of copper sulfate (CuSO ₄ .5H ₂ O) were added to 1930 g of 50% sulfuric acid.
to prepare a mixed metal salt aqueous solution. This aqueous solution was then added with concentrated sulfuric acid (98% H ₂ SO ₄ ).
Add 208 ml and continue stirring for 1 hour at a temperature of 50-60°C to precipitate fine mixed sulfate crystals of manganese and copper. Next, 225 g of potassium permanganate powder was gradually added to the stirred slurry and maintained for about 2 hours to complete the oxidation reaction. Next, a small amount of water is added to the oxidized slurry to facilitate the separation operation, and then separated to separate the mother liquor and the precipitate. After redispersing the precipitate in water, it was neutralized with a caustic soda solution (48% NaOH) under stirring until the pH reached 9 to 10, and then by a conventional method.
The product was separated, washed with water, and dried to obtain a copper-supported manganese dioxide-based oxidation catalyst. Example 2 Crystals of 315 g of manganese sulfate (MuSO ₄ .H ₂ O) and 286 g of copper sulfate (CuSO ₄ .5H ₂ O) were prepared in Example 1.
Mother liquor separated and collected (H ₂ SO ₄ : 50%, Mu: 0.17
%, Cu: 0.22%, K: 0.66%, specific gravity: 1.397)
After dissolving in 1387ml, concentrated sulfuric acid (H ₂ SO ₄ : 98%)
Add 208 ml and continue stirring for about 1 hour to crystallize fine mixed crystals of manganese sulfate and copper sulfate. Then, 225 g of potassium permanganate crystals are gradually added to the sulfuric acid acidic slurry at a temperature of 50-60° C. to cause an oxidation reaction, and stirring is continued for about 2 hours. Next, 358 ml of water is added and solid-liquid separation is performed at room temperature to collect the precipitate and mother liquor, respectively. Next, the obtained precipitate was redispersed in water, neutralized with 28% ammonia water until the pH reached 9.3, and then separated, washed with water, and dried to obtain copper-supported manganese dioxide. A system oxidation catalyst was obtained. Example 3 Manganese sulfate (MnSO ₄ H ₂ O) 119 ml in 120 ml of water
A metal salt mixed aqueous solution prepared by adding 108 g of copper sulfate (CuSO ₄ .5H ₂ O) and 108 g of copper sulfate (CuSO 4 .5H 2 O) is heated to 45°C. To this was added the mother liquor collected and prepared in Example 2 (H ₂ SO ₄ :
55%, Mn: 0.16%, Cu: 0.20%, K: 0.65%,
Add 1340 ml of specific gravity: 1.455, and then add concentrated sulfuric acid (98
%H ₂ SO ₄ ) and stirred for about 1 hour to precipitate mixed crystals of the metal salt. Next, 85 g of crystalline powder of potassium permanganate is gradually added to the obtained slurry at a temperature of 55° C. After the addition, an oxidation reaction is caused and the slurry is aged for about 2 hours under stirring. After aging, the precipitate and liquid are filtered and separated. Below, Example 1
The same operation as above was carried out to obtain a copper-supported manganese dioxide-based oxidation catalyst. Example 4 Mother liquor recovered in Example 3 (H ₂ SO ₄ :55%,
Mn: 0.16%, Cu: 1.20%, K: 0.65%, Specific gravity:
1.455) Manganese sulfate 315g, copper sulfate 214 in 1340ml
g and 250 g of nickel sulfate (NiSO ₄ .6H ₂ O) were added thereto and the temperature was raised to 40 to 50° C. to prepare a metal salt mixture. To this, 229 ml of concentrated sulfuric acid (98% H ₂ SO ₄ ) is added and aged at a temperature of 50 to 60° C. for about 1 hour to precipitate a mixed crystal of metal salt. Next, 225% potassium permanganate crystal powder was added to the resulting strongly acidic slurry.
g is gradually added, and stirring is continued for about 2 hours after the addition to complete the oxidation reaction. Next, 358 ml of water is added to this slurry, and the slurry is filtered to separate the precipitate and the liquid. Thereafter, the same operation as in Example 1 was carried out to obtain a copper-supported manganese dioxide-based oxidation catalyst. Comparative example 1 315 g of manganese sulfate (MnSO ₄ H ₂ O) and 560 g of water
ml of the aqueous solution dissolved in concentrated sulfuric acid at a temperature of 45℃.
After adding 319 ml, aging was continued for about 1 hour to precipitate crystals of manganese sulfate. Next, 225 g of potassium permanganate crystal powder was added to this slurry.
was gradually added to carry out the reaction, and stirring was continued for about 2 hours to complete the oxidation treatment. Next, this is diluted with water, washed until the pH of the solution reaches 5 or more, and then subjected to excessive separation to obtain a hydrated manganese dioxide. On the other hand, add 286 g of copper sulfate (CuSO _{4.5H 2} O) to water.
A caustic soda solution was added to a 1430ml aqueous solution of copper sulfate at a temperature of 65°C to a pH of 9 to 10 to form a precipitate. After cooling, the solution was washed until the pH reached 7.5 or less, and then over-separated. to obtain hydrated copper oxide. Water was added to each of the resulting cakes, and the mixture was thoroughly mixed and stirred, followed by filtering and drying in a conventional manner to obtain a manganese dioxide-based oxidation catalyst supporting copper. Comparative Example 2 A metal salt mixed aqueous solution is prepared by dissolving 315 g of manganese sulfate (MnSO ₄ .H ₂ O) and 214 g of copper sulfate (CuSO ₄ .5H ₂ O) in 500 ml of water. Next, 225 g of crystalline powder of potassium permanganate was added, and after the oxidation treatment, the pH was neutralized to 9 to 10 with NaOH solution.
The precipitate was separated by a conventional method, washed with water, and dried to obtain a copper-supported manganese dioxide-based oxidation catalyst. Comparative Example 3 After preparing a mixed solution in which 315 g of manganese sulfate (MuSO ₄ .H ₂ O) and 214 g of copper sulfate (CuSO ₄ .5H ₂ O) were dissolved in 500 ml of water, 225 g of crystalline powder of potassium permanganate was added to this. After adding an alkaline potassium permanganate solution prepared by dissolving MnO _x and CuO in 700 ml of 10% KOH solution to coprecipitate MnO Obtained. Evaluation of catalytic ability 1 Sample preparation 10 g of each sample produced in Examples 1 to 4 and Comparative Examples 1 to 3 (120°C, 4 hours dry basis)
After kneading 0.5 g of bentonite as a binder with an appropriate amount of water, the mixture is molded using a pelleter. Next, the catalyst sample is dried at about 200°C. 2 CO gas removal method CO gas concentration 5000ppm, humidity 50%, temperature 20℃
The contaminated air ^at
The CO gas concentration and the time until the concentration reached 50 ppm were measured. The CO gas concentration was measured using a carbon monoxide meter using a constant potential electrolysis method. 3 Measurement Results The results of the CO removal measurement described above are shown in Table 1 along with the physical properties of the catalyst.

【table】

[Table] <Effects of the invention> The manganese dioxide-based oxidation catalyst according to the present invention is
In particular, it has excellent catalytic performance, with excellent performance in oxidizing and removing carbon monoxide, less deterioration in performance due to humidity, and a longer service life than conventional hopcalite catalysts. On the other hand, from the perspective of the manufacturing method, the amount of alkali used is small, the amount of waste water is also reduced compared to the conventional method, and the amount of sulfuric acid used can also be reduced by recovering and recycling the sulfuric acid. There are advantages. Further, according to the method of the present invention, a highly reliable catalyst with stable quality can be industrially advantageously produced.

Claims (1)

[Claims] 1. A first step in which an aqueous solution of a mixed salt of manganese and copper is acidified with a mineral acid to precipitate mixed salt crystals of manganese and copper. Potassium permanganate is added to the strongly acidic slurry system obtained from the previous step. A second step in which manganese dioxide is produced by addition and oxidation treatment, a third step in which the precipitate from the previous step is separated from the mother liquor, and a fourth step in which the obtained precipitate is neutralized with an alkali agent. A method for producing a manganese dioxide-based carbon monoxide oxidation catalyst. 2. The method for producing a manganese dioxide-based carbon monoxide oxidation catalyst according to claim 1, wherein the aqueous mixed salt solution of manganese and copper has a molar ratio (Mn/Cu) in the range of 1.4 to 14.0. 3. The method for producing a manganese dioxide-based carbon monoxide oxidation catalyst according to claim 1, wherein the strongly acidic slurry system is a metal sulfate-sulfuric acid slurry. 4. The method for producing a manganese dioxide-based carbon monoxide oxidation catalyst according to claim 1 or 3, wherein the mother liquor from which the precipitate is separated is recycled as a mineral acid source for dissolving or precipitating manganese and copper salts. .