JPH0576761A - Production of iron oxide catalyst for treatment of gaseous material - Google Patents

Abstract

PURPOSE:To secure excellent catalytic performances and the like by impregnating a monolithic carrier with an aq. soln. of iron (II) salt, immersing the monolithic carrier in an aq. soln. of alkali hydroxide and introducing an oxygen-contg. gas thereinto in order to deposit a large amt. of iron oxide particles and the like firmly on the monolithic carrier. CONSTITUTION:The iron oxide-base catalyst for treatment of gaseous material is produced by the following process. First, a monolithic carrier made of ceramics or metal is immersed in an aq. soln. of iron (II) salt to impregnate the carrier with this soln. Then, the monolithic carrier impregnated with the iron (II) salt aq. soln. is immersed in an aq. soln. of alkali hydroxide or alkali carbonate soln. while an oxygen-contg. gas is introduced to the soln. Thus, magnetite particles or magnetite-contg. iron (III) hydroxide particles are precipitated and deposited on the monolithic carrier. Then the monolithic carrier obtd. by precipatation of particles is washed with water, dried, and heat treated at 200-700 deg.C. The obtd. catalyst contains a large amt. of particles firmly deposited on the monolithic carrier and has excellent catalytic performances and high strength.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an iron oxide-based catalyst for treating a gas body, which has excellent catalytic performance and great strength by supporting a large amount and firmly of iron oxide particles on a ceramic or metal monolith carrier. The purpose is to provide.

[0002]

2. Description of the Related Art As is well known, exhaust gas discharged from combustion furnaces, internal combustion engines, etc. contains a large amount of harmful components such as nitrogen oxides and sulfur oxides, which causes so-called pollution problems such as air pollution. It is causing it. Recently, as environmental issues have become more important, regulations are becoming stricter, and there is a strong demand for measures to deal with them.

Magnetite particles ( FeO x · Fe ₂ O ₃ 0 <are used as catalysts for modifying or decomposing and removing harmful components such as nitrogen oxides and sulfur oxides present in exhaust gas.
x ≦ 1), ferric oxide hydroxide particles (α, β, γ-FeOO
It is widely known that various iron oxides having different crystal structures such as H), hematite particles (α-Fe ₂ O ₃ ) and maghemite particles (γ-Fe ₂ O ₃ ) are effective. Since various ferric oxides having different crystal structures have different catalytic performances depending on the use, different types of iron oxides are used depending on the use. In use, it can be used as a powder as it is, used as a granulated product by adding a binder or the like, or loaded on a carrier substance such as silica, alumina, titania, magnesia, diatomaceous earth for practical use. It is used after being formed into a shape that is easy to use.

The iron oxide type catalyst, once used, is 450-
Although it can be used repeatedly by heating it at a high temperature of 850 ° C. and regenerating it, the above-mentioned powdery and granulated products can remarkably disintegrate in the regenerating process and can withstand long-term use. However, problems with strength have been pointed out. On the other hand, silica, alumina, titania, magnesia,
A catalyst formed by supporting iron oxide on a carrier substance such as diatomaceous earth is advantageous in terms of strength, but molded articles such as spherical, columnar, and cylindrical shapes are particularly useful when packed in a fixed bed reactor. Was a cause of clogging due to dust, which was a cause of reducing the efficiency of removing harmful components in the exhaust gas.

Therefore, in order to prevent clogging by dust, a catalyst in which iron oxide particles are supported on a ceramic or metal monolith carrier has been proposed and put into practical use. The monolith (Monolith) carrier means a parallel through circular type, a rectangular type, a triangular type, a hexagonal type, which is represented by a honeycomb structure.
It is a structure in which a large number of sine-shaped holes are arranged, and there are various types depending on the shape and arrangement of the holes, the difference in the shape of the structure, and the like.

Conventionally, as a method for supporting iron oxide on a carrier, the porous carrier is immersed in an aqueous solution of iron salt to impregnate the aqueous solution of iron salt into the porous carrier and then heated to form the aqueous solution of iron salt. A method of thermally decomposing to produce iron oxide particles (Japanese Patent Laid-Open No. 63-294939), and a previously prepared honeycomb structure is immersed in a slurry solution containing iron oxide particles and an adhesive such as colloidal silica. Method for supporting iron oxide particles through an adhesive (Japanese Patent Application Laid-Open No. 6-58242)
3-42735), the sheet-shaped carrier is preliminarily loaded with the iron oxide particles via the adhesive by immersing the sheet-shaped carrier in a slurry solution containing iron oxide particles and an adhesive such as colloidal silica, After that, a method of forming the honeycomb structure into a honeycomb structure using an adhesive (Japanese Patent Laid-Open No. SHO 6-96
No. 3-232847) is known.

As described above, a catalyst in which iron oxide particles are supported on a monolith carrier is advantageous in that it can prevent clogging due to dust. Therefore, in recent years, a monolith carrier has been used to withstand longer-term use. Research and development of catalysts are active. In order for the catalyst to withstand long-term use, it is necessary to improve the catalyst performance and strength, and for that purpose, it is strongly required to support the iron oxide particles in a large amount and firmly on the monolith carrier.

[0008]

At present, an iron oxide catalyst in which a large amount of iron oxide particles are strongly supported on a ceramic or metal monolithic carrier is the most demanded at the present time, but these properties are sufficiently satisfied. Things have not been obtained yet.

That is, in the case of the method described above,
The supported iron oxide particles are ultrafine particles because they are generated by thermally decomposing a ferrous salt aqueous solution,
When high temperature heat treatment is repeated for regeneration, sintering gradually occurs between the ultrafine particles to form large particles, and the specific surface area becomes small, so that the catalyst performance deteriorates. In any of the methods described above and described, since iron oxide particles are supported on a carrier through an adhesive, it is difficult to support a large amount of iron oxide, and the adhesion does not contribute to the catalytic performance. Due to the presence of the agent, sufficient catalytic performance cannot be obtained.

Therefore, it is a technical object of the present invention to produce an iron oxide catalyst in which a large amount and iron oxide particles are strongly supported on a ceramic or metal monolith carrier.

[0011]

The above technical problems can be achieved by the present invention as follows. That is, in the present invention, a ceramic or metal monolith carrier is immersed in a ferrous salt aqueous solution to impregnate the monolith carrier with a ferrous salt aqueous solution, and then the ferrous salt aqueous solution is impregnated. The monolithic carrier is immersed in an aqueous solution of alkali hydroxide or an aqueous solution of alkali carbonate to aerate an oxygen-containing gas to deposit and support magnetite particles or ferric oxide hydroxide particles on the monolithic carrier, or, if necessary, magnetite particles. Alternatively, the method is a method for producing an iron oxide-based catalyst for treating a gas body, which comprises washing a monolith carrier having precipitated ferric oxide hydroxide particles carried thereon with water, drying and further heat-treating it in a temperature range of 200 to 700 ° C.

Next, various conditions for carrying out the present invention will be described. As the ceramic or metal monolithic carrier in the present invention, cordierite, alumina, or an iron plate molded using a ceramic material such as mullite,
Stainless steel (Fe-Cr-Al system, Fe-Cr-Al
A metal material such as (La-based) can be used. In order to support a large amount of iron oxide particles,
It is preferable that the material forming the monolith carrier has a large number of pores or irregularities.

The ferrous salt aqueous solution in the present invention includes:
An aqueous ferrous nitrate solution, an aqueous ferrous sulfate solution, an aqueous ferrous chloride solution or the like can be used. The concentration of the ferrous salt aqueous solution is preferably in the range of 0.001 to 2.0M. 0.00
If it is less than 1 M, a large amount of magnetite particles or ferric oxide hydroxide particles cannot be deposited and supported on the carrier. If it exceeds 2.0 M, the precipitated and supported magnetite particles or ferric hydrous oxide particles will be aggregated particles, resulting in a small specific surface area and poor catalyst performance.

As the alkaline aqueous solution in the present invention,
An aqueous solution of an alkali hydroxide such as a sodium hydroxide solution or a potassium hydroxide solution, an aqueous solution of sodium carbonate, an aqueous solution of potassium carbonate, an aqueous solution of an alkali carbonate such as ammonium carbonate, sodium hydrogencarbonate or potassium hydrogencarbonate can be used.

The oxidizing means in the present invention is carried out by aerating an oxygen-containing gas (for example, air) in the liquid, and may be accompanied by stirring by a mechanical operation or the like as necessary.

The temperature in the liquid when the oxygen-containing gas is aerated in the present invention is 100 ° C. or lower. The type of iron oxide deposited and supported on the monolithic carrier varies depending on the temperature in the liquid, and ferric oxide hydroxide particles are deposited at a temperature of less than 50 ° C, and magnetite particles are deposited at a temperature range of 50 to 100 ° C.

In the present invention, the crystal structure of the iron oxide can be changed by heat-treating the monolith carrier on which the magnetite particles or the ferric oxide-containing particles are deposited and supported.
When the heating temperature is 200 to 500 ° C., the magnetite particles deposited and supported on the carrier are maghemite (γ-
Fe ₂ O ₃ ) and becomes hematite (α-Fe ₂ O ₃ ) when the temperature is 500 ° C. or higher. Further, the ferric oxide hydroxide particles become hematite (α-Fe ₂ O ₃ ) at 200 ° C or higher.

[0018]

First, the most important point in the present invention is to immerse a ceramic or metal monolith carrier in a ferrous salt aqueous solution to impregnate the monolith carrier with the ferrous salt aqueous solution.
Then, the monolith carrier impregnated with the ferrous salt aqueous solution is immersed in an alkali hydroxide aqueous solution or an alkali carbonate aqueous solution, and an oxygen-containing gas is passed through the magnetite particles or ferric hydroxide-containing particles to the monolith carrier. It is a fact that when iron oxide is deposited and supported, it is possible to obtain an iron oxide-based catalyst for treating a gas body, in which a large amount of iron oxide particles are strongly supported.

In the present invention, the reason why the iron oxide particles can be supported in a large amount and strongly is that the present inventor impregnates the iron raw material in the form of ions into the monolith carrier, so that it is necessary to use an adhesive. Moreover, not only the surface of the sharp edges and shaded portions of the monolith carrier and the finely-shaped complex portion of the monolith carrier, but also the pores and irregularities of the material itself constituting the monolith carrier can be easily impregnated in a large amount. The ferrous salt can be supported, and the magnetite particles and ferric oxide-containing ferric oxide particles are directly deposited and grown strongly on the monolithic carrier, so that they are strongly supported. It is considered that the material carried and used is more strongly carried by the anchor effect.

In the present invention, iron oxide particles having different crystal structures can be obtained by heat-treating the monolith carrier carrying magnetite particles or ferric oxide-containing particles.

[0021]

The present invention will be described below with reference to Examples and Comparative Examples. The adhesion of iron oxide to the carrier in the following examples and comparative examples is shown by the value obtained by the following method. The iron oxide-supported monolith carrier was fixed in a graduated cylinder, and subjected to a vertical shock vibration of 10,000 times. Then, the monolith carrier was taken out from the measuring cylinder, and the residual iron oxide was quantitatively analyzed. The value obtained by dividing the weight (Bg) of the iron oxide remaining after the vertical shock vibration by the weight (Ag) of the iron oxide initially supported was expressed as a percentage. The larger this value, the better the adhesion. The catalyst performance in Examples 1 to 14 described later is based on "Catalyst Experiment Handbook" published by Kodansha Scientific.
The value was measured according to the evaluation method described on page 44 of the above. That is, the monolith carrier was packed in a column and set in a flow-type adsorption capacity evaluation device, and then a test gas was passed through the column at a constant flow rate for a certain period of time, after which the concentration of harmful components at the outlet of the column was measured by a gas chromatography method. It was shown by the value.

<Production of Iron Oxide Catalyst> Examples 1 to 7 Comparative Examples 1 to 4 Example 1 A cylindrical shape (diameter 23 mm) made of cordierite material.
φ, cylinder height 50 mm, 400 cells / inch ² ) monolith carrier (manufactured by Nippon Insulators Co., Ltd.) (hereinafter referred to as carrier A).
Was immersed in acetone to degrease it. The degreased monolith carrier was immersed in a 1.0 M FeSO ₄ aqueous solution at room temperature for 30 minutes and then taken out into the air to remove an excessive FeSO ₄ aqueous solution. Then, 1-N Na ₂ C at a temperature of 40 ° C.
After immersing in 150 ml of O ₃ solution, air was blown into the Na ₂ CO ₃ solution at a rate of 1 l / min for 1 hour to deposit and support yellowish brown goethite particles (α-FeOOH). The obtained monolithic carrier carrying the goethite particles was thoroughly washed with water and then dried at 80 ° C. The amount of goethite supported on this monolith carrier was 2.8% by weight based on the monolith carrier. The adhesion of the goethite particles to the carrier was 99.9%.

Example 2 A cylindrical monolithic carrier (diameter 23 mmφ, cylinder height 50 mm) made of a mixed fiber of silica fiber, aluminosilicate fiber, and zirconia fiber (manufactured by Nichias Co., Ltd .: trade name hanicle) (hereinafter, carrier B) was immersed in acetone for degreasing. Degreased monolith carrier with 1.2M F
Goethite particles were deposited and supported on the monolith carrier in the same manner as in Example 1 except that the solution was immersed in an eSO ₄ aqueous solution at room temperature for 30 minutes. The amount of goethite supported on the monolith carrier was 4.4% by weight based on the monolith carrier. The adhesion of the goethite particles to the carrier was 99.8%.

Example 3 A monolith carrier carrying goethite particles was obtained in the same manner as in Example 1 except that the concentration of the FeSO ₄ aqueous solution was changed to 1.5M. This was heated in air at 600 ° C. for 2 hours to obtain a monolithic carrier supporting hematite particles. The amount of hematite particles carried on the monolith carrier was 3.7 wt% based on the monolith carrier. Also,
The adhesion of the hematite particles to the carrier was 99.6%.

Example 4 A monolithic carrier carrying hematite particles was obtained in the same manner as in Example 3 except that the carrier B was used and the concentration of the FeSO ₄ aqueous solution was 0.2M. The amount of hematite particles carried on the monolith carrier was 0.6% by weight based on the monolith carrier. The adhesion of the hematite particles to the carrier was 99.8%.

Example 5 A monolith carrier carrying magnetite particles was obtained in the same manner as in Example 1 except that the concentration of the FeSO ₄ aqueous solution was 0.8 M and the reaction temperature in the alkaline solution was 90 ° C. The amount of magnetite particles carried on the monolith carrier was 2.3 wt% with respect to the monolith carrier. The adhesion of magnetite particles to the carrier was 99.4%.

Example 6 A monolithic carrier carrying magnetite particles was obtained in the same manner as in Example 5 except that the carrier B was used and the concentration of the FeSO ₄ aqueous solution was changed to 0.1M. The amount of magnetite particles carried on the monolith carrier is 0.
It was 3 wt%. The adhesion of magnetite particles to the carrier was 99.6%.

Example 7 Stainless steel (Fe 75 wt% -Cr 20 wt%-
A cylindrical shape (diameter 25) made of Al 5 wt% -La)
mmφ, cylinder height 50 mm) (hereinafter, carrier C)
And ) In 1.2M FeSO ₄ aqueous solution at room temperature
After soaking for 0 minute, it was taken out into the air to remove the excess FeSO ₄ aqueous solution. Then, it was immersed in a 1.0 M Na ₂ CO ₃ solution, and air was blown through it for 3 hours at a temperature of 40 ° C. to deposit and support yellowish brown goethite particles, which was then washed with water and dried to carry the goethite particles. We obtained a honeycomb catalyst.
The amount of goethite supported on this honeycomb carrier was 1.2% by weight based on the monolith carrier. The adhesion of the goethite particles to the carrier was 99.0%.

COMPARATIVE EXAMPLE 1 1.0 M F was added to 1 L of a 50 M Na ₂ CO ₃ aqueous solution.
3 l of an eSO ₄ aqueous solution was added and mixed to obtain FeCO ₃ at a temperature of 40 ° C. A 10 l / min air was passed through this for 3 hours to carry out an oxidation reaction to produce yellowish brown precipitate particles. Generated particles are filtered at room temperature, washed with water,
It was dried to obtain goethite particles. Water was added to the obtained goethite particles and stirred with a homomixer to obtain a 1 wt% slurry liquid. Add NaOH to this slurry to adjust the pH to 1
The carrier A was added to the slurry liquid whose temperature was adjusted to 60 ° C.
Was soaked. After adjusting the pH to 5 and cooling to room temperature, washing with water,
It was dried to obtain a monolith carrier supporting goethite particles. The amount of goethite particles carried on the monolith carrier was 0.5% by weight. The adhesion of the goethite particles to the carrier was 96.7%.

Comparative Example 2 Ferrous sulfate aqueous solution 20 containing 1.5 mol / l of Fe ²⁺
1 was prepared beforehand in the reactor 3.45-
In addition to the NaOH aqueous solution 20 l of N (Fe ²⁺ to 1.
This corresponds to 15 equivalents. ) PH 12.8, Fe (OH) ₂
An aqueous solution containing was produced. Magnetite particles were produced by bubbling 100 l of air per minute for 220 minutes at a temperature of 90 ° C. into the aqueous solution containing Fe (OH) ₂ . The produced particles were separated by filtration, washed with water and dried to obtain magnetite particle powder. The obtained magnetite particle powder was heated in air at 450 ° C. to obtain hematite particles. Water was added to the hematite particles and stirred with a homomixer to obtain a slurry containing 1% by weight of the hematite particles. A monolith carrier carrying hematite particles was obtained in the same manner as in Comparative Example 1. The amount of hematite particles carried on the monolith carrier was 0.3% by weight. The adhesion of the hematite particles to the carrier was 96.0%.

Comparative Example 3 Using the magnetite particle powder obtained in the same manner as in Comparative Example 2, a slurry containing 1% by weight of magnetite particles was obtained. A monolith carrier carrying magnetite particles was obtained in the same manner as in Comparative Example 1 except that the final pH was changed to 7. The amount of magnetite particles carried on the monolith carrier was 0.3% by weight. The adhesion of magnetite particles to the carrier was 95.8%.

Comparative Example 4 A honeycomb carrier carrying goethite particles was obtained in the same manner as in Comparative Example 1 except that the carrier C was used. The amount of goethite particles carried on the honeycomb carrier was 0.2% by weight. The adhesion of goethite particles to the carrier is 95.1.
%Met.

<Use of Iron Oxide Catalyst> Use Examples 1 to 14; Use Example 1 Five sample monolith carriers obtained in Example 1 are connected and packed in a column to prepare a sample column, which is a flow-through type. It was set in the adsorption capacity evaluation device. A test gas containing hydrogen sulfide with a concentration of 10 ppm (10% humidity) was then bubbled through the test column at a flow rate of 0.5 l / min. The hydrogen sulfide content concentration at the outlet of the column after 120 minutes of aeration was 0.42 ppm.

Use Examples 2 to 5 Tests were performed in the same manner as in Use Example 1 except that the type of catalyst was changed. The results are shown in Table 1.

Use Example 6 A test was conducted in the same manner as in Use Example 1 except that the test gas was changed to 10 ppm of trimethylamine. The trimethylamine content concentration at the outlet of the column was 1.3 ppm.

Use Examples 7 to 8 Tests were performed in the same manner as in Use Example 6 except that the type of catalyst was changed. The results are shown in Table 1.

USE EXAMPLE 9 Five monolithic carriers obtained in Example 3 were connected and set in a reaction tube. A test gas containing 1000 ppm of H ₂ S gas was passed through this at 500 ° C. and 3 atm at a flow rate of 1 Nl / min. H ₂ S adsorption breakthrough, that is, the amount of H ₂ S gas at the outlet of the reaction tube gradually increases from the minimum value
₂ The time required to reach 50% of the amount of S gas is 203
It was time.

Use Examples 10 to 11 Tests were performed in the same manner as Use Example 9 except that the type of monolith carrier and the number of connected monolith carriers were changed. The results are shown in Table 1.

USE EXAMPLE 12 Five monolithic carriers obtained in Example 5 were connected and packed in a column, placed, and heated to 800 ° C. 5000 ppm of carbon monoxide was bubbled through the column at 1 Nl / min. The concentration of carbon monoxide at the column outlet 10 minutes after aeration was 1.2 ppm.

Use Examples 13 to 14 Tests were performed in the same manner as in Use Example 12 except that the type of catalyst was changed. The results are shown in Table 1.

[0041]

[Table 1]

[0042]

EFFECTS OF THE INVENTION According to the method for producing an iron oxide-based catalyst for treating a gas body according to the present invention, as shown in the above-mentioned Examples, a large amount of iron oxide particles and a strong strength are provided on a ceramic or metal monolith carrier. Since it can be supported on, it has excellent catalytic performance and great strength, and is therefore suitable as an iron oxide-based catalyst for gas body treatment.

Continuation of the front page (72) Inventor Nansei Horiishi 4-1-2 Funairinami Naka-ku, Hiroshima City, Hiroshima Prefecture Toda Kogyo Co., Ltd. Creation Center

Claims (2)

[Claims] 1. A monolith in which a ceramic or metal monolith carrier is immersed in a ferrous salt aqueous solution to impregnate the monolith carrier with the ferrous salt aqueous solution, and then the ferrous salt aqueous solution is impregnated. Iron for gas body treatment, characterized in that magnetite particles or ferric hydroxide-containing particles are deposited and carried on the monolith carrier by immersing the carrier in an aqueous alkali hydroxide solution or an aqueous alkali carbonate solution and aerating an oxygen-containing gas. Method for producing oxide-based catalyst. 2. A gas body characterized in that the monolith carrier carrying the magnetite particles or ferric oxide-containing hydroxide particles according to claim 1 is washed with water, dried, and then heat-treated in a temperature range of 200 to 700 ° C. Process for producing iron oxide catalyst for treatment.