JPH04349936A - Catalyst for eliminating carbon monooxide and preparation of the same - Google Patents

Abstract

PURPOSE:To eliminate efficiently carbon monooxide at relatively low temperatures by introducing a transition base metal element between layers of a swelling inorganic compound of a layer form, inserting uniformly the transition base metal element between the layers. CONSTITUTION:A swelling inorganic compound of a layer form, after being mixed with water to introduce water between the layers, is added with an aqueous solution of a transition base metal salt of a given concentration, and the mixture is mixed completely. Into the mixed solution, an alkaline solution of sodium hydroxide, etc., of a given concentration is added to neutralize the solution, then the mixture is washed and centrifuged. The obtained swelling inorganic compound of a layer form being swelled, after being dried by means of drying under reduced pressure and ultra-critical drying, etc., is calcinated to obtain a catalyst for eliminating carbon monooxide. The catalyst has a structure forming a layer 1 containing the transition base metal element between layers 2, 2 of the swelling inorganic compound of a layer form. Practical examples of the transition base metal elements are Zn, Ni, Co, etc., and practical examples of the swelling inorganic compounds of a layer form include Na- montmorillonite, synthetic hectolite, synthetic smectite.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a carbon monoxide removal catalyst using an inorganic porous material, and further relates to a method for producing the same.

0002

BACKGROUND OF THE INVENTION Catalysts that remove trace amounts of carbon monoxide (hereinafter sometimes referred to as "CO") present in the air are extremely limited. Such catalysts include noble metals such as palladium, platinum, and ruthenium. These noble metals are used as CO removal catalysts by being supported on a carrier such as alumina or silica.

0003

[Problems to be Solved by the Invention] Since the above-mentioned noble metal catalysts are expensive, a CO removal catalyst made of relatively inexpensive materials is desired. Therefore, the first object of the present invention is to provide a carbon monoxide removal catalyst made of relatively inexpensive materials, and the first object is to provide a manufacturing method by which such a carbon monoxide removal catalyst can be easily obtained. This is the second issue.

0004

[Means for Solving the Problems] In order to solve the first problem, the carbon monoxide removal catalyst of the present invention is formed by introducing a base metal transition element between the layers of a swellable inorganic layered compound. . In order to solve the above second problem, the method for producing a carbon monoxide removal catalyst of the present invention includes adding a swollen swellable inorganic layered compound to a base metal transition element-containing solution, adding an alkali, and then drying the swellable inorganic layered compound. By doing this, a carbon monoxide removal catalyst is obtained.

In the present invention, a base metal transition element is used as a catalyst for removing CO, and the base metal transition element is incorporated between the layers of the swellable inorganic layered compound. Base metal transition elements have been introduced into swellable inorganic layered compounds in the form of compounds such as, but not limited to, hydroxides. Further, there is no particular restriction on the form in which it exists, and for example, as shown in FIG. 1, a layer 1 containing a base metal transition element is formed between layers 2 of the swellable inorganic layered compound. However, this is not limited to the case where the space between layers 2 and 2 of the swellable inorganic layered compound is completely filled, and there are cases where the swelling inorganic layered compound is only deposited on layer 2 but does not completely fill the space between the layers. This also includes cases where it is porous. In addition, in FIG. 1, the layer 1 containing the base metal transition element is depicted as being separated from the layer 2 of the swellable inorganic layered compound, but they may be attached to each other.

[0006] The base metal transition element (hereinafter referred to as "transition metal") used in this invention is a transition element other than a noble metal, and can be incorporated into a swellable inorganic layered compound such as clay as a transition metal hydroxide. , for example, Zn, Ni, Cu, which precipitate poorly soluble hydroxides when hydrolyzed.
, Fe, Co, and the like. From the point of view of precipitating poorly soluble hydroxides, Mg is also possible although it is not a transition element.

As the swellable inorganic layered compound, for example, any of Na-montmorillonite, synthetic hectorite, synthetic smectite (for example, synthetic saponite, Na-hectolite, and Na-teniolite) may be used, You can use one type of each alone,
Two or more types can be used in combination. For example, in the case of a hydroxide of a transition metal, the ratio of the swellable inorganic layered compound to the transition metal is about 3 moles of the hydroxide per 1 mole of the swellable inorganic layered compound. . If the amount of hydroxide is more than this, there is a risk that the hydroxide will be precipitated outside the swellable inorganic layered compound, whereas if it is too small, there is a risk of deterioration in performance.

[0008] In order to insert the transition metal between the layers of the swellable inorganic layered compound, the following method is adopted, for example. In other words, by taking advantage of the fact that the interlayers of a swellable inorganic layered compound such as clay exhibit strong acidity, the swellable inorganic layered compound is dispersed in an aqueous transition metal salt solution, and then neutralized by slowly adding alkali, such as during titration. By doing so, transition metal hydroxides and the like are precipitated between the layers of the swellable inorganic layered compound to form a layer. Formation of this layer can be confirmed by, for example, X-ray powder diffraction method, fluorescent X-ray method, or analysis of peaks when dehydration is performed.

Next, the method for producing an inorganic porous body according to the present invention will be explained in more detail step by step. First, the main material, a swellable inorganic layered compound, is mixed with water to form a state in which water is impregnated between the layers. A transition metal salt aqueous solution (the concentration of the metal salt is, for example, about 0.1 M, but is not limited thereto) is added thereto and thoroughly stirred. An alkaline solution such as an aqueous sodium hydroxide solution (the concentration of the alkali is, for example, about 0.1N, but is not limited thereto) is slowly added to the mixed solution thus obtained, followed by drying and baking. This firing is, for example, 100 to 200
It is best to do this at ℃. When firing at temperatures up to 300°C, nothing comes out outside of the swellable inorganic layered compound;
When the temperature drops to around 0°C, there is a risk that it will turn into oxides and come out. If the alkaline solution is added rapidly, the transition metal hydroxide will precipitate outside the swellable inorganic layered compound, so it is better to add it slowly so that the transition metal hydroxide is precipitated between the layers of the swellable inorganic layered compound. With alkali, e.g.
A transition metal salt aqueous solution is neutralized, and a transition metal hydroxide is precipitated.

Next, the swollen swellable inorganic layered compound is dried. This drying may be carried out by any suitable drying method such as supercritical drying, critical point drying, freeze drying, reduced pressure drying, hot air drying, etc., but supercritical drying is preferred. When drying in a supercritical state, for example, the following procedure is performed. Note that in this specification, a supercritical state may include not only the case where the critical point is exceeded but also the case where the supercritical state is exactly at the critical point. A specific method for drying in a supercritical state is, for example, by directly heating and/or pressurizing the solvent held and contained in the swellable inorganic layered compound, such as water contained between the layers, to a state above its critical point. There is a method of removing the solvent and drying it. However, in this case, if a solvent such as water has an extremely high critical point (critical temperature of water: 374.2°C, critical pressure: 217.6 atm), a container such as a special autoclave must be used. It disappears. In order to avoid this, for example, the solvent contained in the swellable inorganic layered compound is replaced with a solvent having a lower critical point, and then supercritical drying is performed. If the swellable inorganic layered compound contains water, for example, water may be substituted with ethanol and heated and/or pressurized to a temperature and pressure higher than the critical point of ethanol to create a supercritical state, or water may be replaced with ethanol to create a supercritical state. After the substitution, carbon dioxide is further added, and while gradually replacing ethanol with carbon dioxide, the temperature and pressure of the two-component system of carbon dioxide and ethanol are heated and pressurized to a temperature and pressure above the critical point to create a supercritical state. All you have to do is to do something like this. After the ethanol has been extracted and removed, the drying process is completed by returning the temperature to normal pressure. When replacing ethanol with carbon dioxide, it is also possible to send carbon dioxide above the critical point into the system for replacement.

[0011]Fluids that can be used as solvents are not limited to those mentioned above. There are various substances that can be made into supercritical fluids within a practical range, and examples include ethanol, methanol, carbon dioxide, dichlorodifluoromethane, and ethylene. For reference, critical conditions for major fluids are shown in Table 1.

0012

[Table 1]

When the swellable inorganic layered compound is dried by supercritical drying, condensation of the solvent in the swellable inorganic layered compound and aggregation of the swellable inorganic layered compounds with each other are prevented, and the structure before drying is well maintained. At the same time, an inorganic porous material is obtained, which is an aggregate of petal-like or cicada-like feathers gathered together like a house of cards or a sponge. Therefore, when supercritical drying is used, a porous body with a larger pore volume can be obtained than when hot air drying or freeze drying is used.

[0014]

[Operation] By introducing a transition metal between the layers of a swellable inorganic layered compound, an inorganic porous body having a carbon monoxide removal function can be obtained. The transition metal used here is a transition element other than a noble metal and is inexpensive. The layer containing a transition metal is made of, for example, a hydroxide of a transition metal. If this hydroxide is used alone without being included in the swellable inorganic layered compound, it will not have a CO removal function, but if it is included in the swellable inorganic layered compound, it will exhibit the CO removal function.

[0015]

[Examples] Specific examples and comparative examples of the present invention are shown below, but the present invention is not limited to the following examples. -Example 1- Na-montmorillonite (swellable inorganic layered compound)
Kunimine Kogyo Co., Ltd.) was dispersed in water to prepare a dispersion containing 0.8 wt% Na-montmorillonite, and 0.1M-CoCl2.H2O was added to this dispersion and thoroughly mixed. . Furthermore, 0.1N-
NaOH was neutralized by slow titration under N2 atmosphere. After titration (when NaOH was added at a ratio of 6 moles to 3 moles of CoCl2), the procedure of washing with water and centrifugation was repeated several times, quickly dried under reduced pressure, and baked at 100°C for 2 hours. did. As a result, a carbon monoxide removal catalyst was obtained.

[0016] The blending ratio of each component is as follows in molar ratio: montmorillonite:CoCl2.H2O:NaOH=1:
The ratio was 3:6. -Example 2- Monoxide was produced in the same manner as in Example 1, except that synthetic saponite (Smecton SA manufactured by Kunimine Kogyo Co., Ltd.), which is one of the synthetic smectites, was used instead of Na-montmorillonite. A carbon removal catalyst was obtained.

-Example 3- A carbon monoxide removal catalyst was obtained in the same manner as in Example 1 except that Ni(NO3)2 was used instead of CoCl2.H2O. -Example 4- In Example 1, ethanol was used instead of water during washing, and instead of vacuum drying, carbon dioxide (CO2), which has a relatively low critical point, was added while drying at 40°C.
A carbon monoxide removal catalyst was obtained in the same manner as in Example 1, except that supercritical drying was performed at 80 atm for 8 hours.

-Example 5- In Example 4, drying was carried out at the critical point (temperature: 31.1°C,
Pressure: 72.8 atm. A carbon monoxide removal catalyst was obtained in the same manner as in Example 4, except that this was carried out for 8 hours at the critical point of carbon dioxide. -Example 6- A carbon monoxide removal catalyst was obtained in the same manner as in Example 1 except that drying was performed by freeze drying.

Example 7 A carbon monoxide removal catalyst was obtained in the same manner as in Example 1, except that synthetic hectorite was used instead of Na-montmorillonite. - Comparative Example 1 - In Example 1, after dispersing Na-montmorillonite in water, 0.1 M-CoCl2 .H2 O was also dispersed.
An inorganic porous body was obtained in the same manner as in Example 1 except that N-NaOH was not added.

- Comparative Example 2 - 0.1M-CoCl2 .H2 O used in Example 1
and 0.1N-NaOH to precipitate Co(OH)2. - Comparative Example 3 - 0.1M-Ni(NO3)2 and 0 used in Example 3
．． Ni(OH)2 was precipitated using 1N-NaOH.

The specific surface area and pore volume of the carbon monoxide removal catalyst of Examples 1 to 7 and the inorganic porous material of Comparative Example 1 were measured. The specific surface area and pore volume are BE in the nitrogen adsorption method.
This was investigated using the T method. The measurement results are shown in Table 2. The CO removal function of the carbon monoxide removal catalysts of Examples 1 to 7, the inorganic porous body of Comparative Example 1, and the metal hydroxides of Comparative Examples 2 and 3 was investigated as follows. Air containing carbon monoxide (2%) was allowed to flow through the reaction system, and the carbon monoxide removal catalyst of Examples 1 to 7 and the inorganic porous material of Comparative Example 1 were used as a CO removal catalyst in the reaction system. , and the metal hydroxides of Comparative Examples 2 and 3 were left while being heated to 80° C., and the concentration of carbon monoxide in the air coming out of the system was measured using gas chromatography. The carbon monoxide removal rate was calculated from this measured value and the results are shown in Table 2. However, in Example 3 and Comparative Example 3, the catalyst was
The measurement was performed after heating to 0°C.

[0022]

[Table 2]

As shown in Table 2, the carbon monoxide removal catalysts of Examples 1 to 7 exhibited a carbon monoxide removal function, but those of Comparative Examples 1 to 3 did not exhibit a carbon monoxide removal function. In particular, a carbon monoxide removal catalyst with cobalt hydroxide inserted between the layers of montmorillonite can remove CO even at low temperatures below 100°C.
It had the best performance as a removal catalyst. Moreover, when drying was performed in a supercritical state, the catalyst function was more effectively exhibited.

[0024]

[Effect of the invention] According to this invention, C without using precious metals.
A catalyst having the function of removing O is obtained. According to the manufacturing method of the present invention, the base metal transition element serving as the catalyst is more uniformly inserted between the layers than in the catalyst supporting method, and a carbon monoxide removal catalyst that can exhibit sufficient functionality can be obtained.

In the present invention, when the base metal transition element introduced between the layers of the swellable inorganic layered compound is cobalt, the carbon monoxide removal catalyst efficiently removes CO at a relatively low temperature of 70 to 80°C. Can be removed.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged view schematically showing one embodiment of the carbon monoxide removal catalyst of the present invention.

[Explanation of symbols]

1 Layer containing base metal transition elements 2 Layer of swellable inorganic layered compound

Claims (3)

[Claims] 1. A carbon monoxide removal catalyst comprising a base metal transition element introduced between layers of a swellable inorganic layered compound. 2. The carbon monoxide removal catalyst according to claim 1, wherein the base metal transition element is cobalt. 3. A method for producing a carbon monoxide removal catalyst, in which a swollen inorganic layered compound is put into a base metal transition element-containing solution, an alkali is added thereto, and then dried.