JP2579178B2 - Composite iron oxide particle powder and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a composite iron oxide particle powder excellent in powder properties such as excess and workability, and a production method.

The main use of the composite iron oxide particle powder according to the present invention is as an adsorbent for sulfur oxide, hydrogen sulfide and the like, nitrogen oxide and the like in the atmosphere and gas, a deodorant and the like.

[Conventional technology]

Sulfur oxides, hydrogen sulfide, nitrogen oxides, etc. in the atmosphere or gas are the main causes of air pollution. In particular, sulfur oxides, hydrogen sulfides, etc. are not only sources of air pollution, but also structures and bridges using iron. Is directly involved in the atmospheric corrosion of nitrogen, and nitrogen oxides and the like can induce photochemical smog, so efforts are made to suppress the generation of sulfur oxides, hydrogen sulfides, nitrogen oxides, etc., and to remove them from sources. Are taking place day and night.

However, in recent years, a large amount of exhaust gas has been emitted due to the increase in the number of combustion furnaces and the spread of automobiles accompanying the development of industry,
Although various countermeasures have been taken, it is still inadequate, and the development of adsorbents and deodorants with excellent adsorption capacity for sulfur oxides, hydrogen sulfide, nitrogen oxides, etc. in gas has been developed. There is a strong demand.

This fact can be seen, for example, in the Journal of the Chemical Society of Japan (1985), p. 2315, "The concentration of nitrogen oxides in the atmosphere in cities has not only declined but has gradually increased, even if various measures have been taken. And efforts to remove nitrogen oxides are increasingly important. "

Conventionally, activated carbon, silica gel, zeolite and the like are generally well known as adsorbents.

[Problems to be solved by the invention]

Adsorbents with excellent adsorption capacity for sulfur oxides, hydrogen sulfides, nitrogen oxides, etc. are currently the most demanded,
It has been pointed out that the known adsorbents as described above are still insufficient as adsorbents for sulfur oxides, hydrogen sulfides, nitrogen oxides and the like.

The fact is that, for example, "The Journal of the Chemical Society of Japan" (1978), p. 665, published by The Chemical Society of Japan, "In order to adsorb and remove sulfur dioxide, inorganic compounds such as activated carbon and various metal oxides have been studied. However, there is still a problem in the adsorption capacity, selectivity, regeneration method, etc., and the development of a new adsorbent is desired. "And the above-mentioned" Journal of the Chemical Society of Japan "(1985) No. 2315 Activated carbon, silica gel and zeolite, which are common adsorbents, are effective for NO ₂ , but do not have sufficient ability to adsorb NO. Therefore, the development of a substance with high adsorption capacity for NO is desired. . ".

It has been found that iron oxide particles have an excellent ability to adsorb sulfur oxides, hydrogen sulfides, nitrogen oxides, and the like to these adsorbents, and have attracted attention. This fact can be found, for example, in “The Chemical Society of Japan” (1978) No. 665, published by The Chemical Society of Japan.
"Chemisorption amount to treat the hydrated iron oxide by the structure transition temperature (200 to 300 [° C.) is increased. Selectively adsorbing SO ₂ from the gas mixture close to the fuel oil combustion exhaust gas composition." Page becomes description and the visual As described on page 666, "When α-FeOOH is heated, a dehydration reaction of 2α-FeOOH → α-Fe ₂ O ₃ + H ₂ O occurs at around 300 ° C.”.

On the other hand, since the adsorbent adsorbs sulfur oxides, hydrogen sulfide, nitrogen oxides, and the like on the surface of the adsorbent, the adsorbent increases as the specific surface area of the adsorbent increases, so the adsorbent can be formed. Only fineness is required. This fact can be found, for example, in the “Journal of the Chemical Society of Japan” (1980)
Year, page 681, "In the study of adsorption of gas molecules on a solid surface, powders having a large surface area are often used."

Therefore, in order to further improve the adsorption ability of the hydrous iron oxide particles having excellent adsorption ability for sulfur oxides, hydrogen sulfides, nitrogen oxides and the like, it is strongly required to make the particles finer.

However, the long axis of the needle-shaped iron oxide particles
If it is less than about 0.1 μm, it is so fine that it is difficult to handle and has poor workability, which is one of the factors that hinders practical use. That is, the fine needle-shaped iron oxide particles, when used as an adsorbent, have low air permeability in order to generate an aggregate of small particles having a small porosity,
At the time of its production, it is generally obtained by heat-treating the acicular iron oxide fine particles in the air. However, as described in detail below, the acicular iron oxide fine particles themselves have poor transient properties. It was difficult to obtain fine particles. Acicular iron oxide hydroxide is generally prepared by reacting a ferrous salt aqueous solution with an alkaline aqueous solution to obtain a suspension containing iron hydroxide by air oxidation or by heating a ferric salt aqueous solution. Although produced from inside, when the product is separated from the aqueous solution, clogging of the cloth and cloth leakage occur.

Therefore, there is a strong demand for the establishment of technical means for improving the excess and workability without lowering the adsorbability of the acicular iron oxide fine particles.

[Means for solving the problem]

The inventor of the present invention has conducted various studies in order to improve the excess and workability without lowering the adsorbing ability of the acicular iron oxide fine particles, and as a result, the present invention has been achieved.

That is, hematite particles present invention, to have no O-shaped particle shape and presents a C-shaped, and, X-rays grain size in average of the maximum diameter A 0.1 to 1.0 [mu] m D ₁₀₄ surface is 100~800Å The major axis diameter is 0.01 to 0.1 μm and the minor axis diameter is
A suspension having a pH of 2 or more containing a composite iron oxide particle powder composed of composite iron oxide particles to which needle-like iron oxide fine particles of 0.005 to 0.05 μm are adsorbed or fixed and a plate-like δ-FeOOH is heated to 150 to 320 ° C.
By hydrothermal treatment in the temperature range described above, the particle shape is O-shaped or C-shaped, and the average value of the maximum diameter is 0.
X-ray particle diameter of ₁₀₄ surface D a 1~1.0μm is 100 to 800
To form hematite particles, and the O-shaped or C
Suspension containing hematite particles in the shape of a letter and long axis 0.01-
0.1 μm and a suspension containing needle-like hydrous iron oxide fine particles having a minor axis of 0.005 to 0.05 μm by mixing with the suspension.
O-shaped or C-shaped composite iron oxide particles in which the needle-shaped hydrous iron oxide fine particles are adsorbed on the surface of hematite particles exhibiting a letter shape or a letter C, and then heating the particles in air. On the surface of the hematite particles having the shape of a letter, the major axis diameter is 0.01 to 0.1 μm and the minor axis diameter is 0.005 to
This is a method for producing composite iron oxide particle powder comprising composite iron oxide particles to which needle-like iron oxide fine particles of 0.05 μm are adsorbed or fixed.

[Action]

First, the most important point in the present invention is the plate-like δ-FeOO
Hematite particles obtained by hydrothermally treating a suspension having a pH of 2 or more containing H at a temperature in the range of 150 to 320 ° C. have an O-shaped or C-shaped particle shape, and have an average maximum diameter. there is 100～800A X-ray particle diameter in an in D ₁₀₄ side is 0.1 to 1.0 [mu] m, when a mixture of a suspension comprising a suspension and acicular iron oxide particles containing the hematite particles As a result, one end of the short axis surface of the acicular hydrous iron oxide fine particles is adsorbed on the hematite particle surface, so that the surface of the O-shaped or C-shaped hematite particles is covered with the acicular hydrous iron oxide fine particles in a barbed shape. When the particles are further heat-treated in air, the acicular iron oxide fine particles undergo a structural transition to become acicular iron oxide fine particles, and the surface of the O-shaped or C-shaped hematite particles is barbed with the acicular iron oxide fine particles. Oxidation in the form covered Is the fact that particles are obtained.

In the present invention, the needle-shaped hydrous iron oxide fine particles are adsorbed along the O-shaped or C-shaped shape of the hematite particles, so that an aggregate of particles having a large porosity is formed. In the event of a mistake, the transient is good,
No clogging of the cloth and no leakage of the cloth occur, and the needle-like iron oxide fine particles obtained by heat-treating the excess adsorb or adhere along the O-shaped or C-shaped hematite particles. Since the composite iron oxide particles are also an aggregate of particles having a high porosity, when used as an adsorbent, the permeability to air and the like is improved.

In the present invention, only one end of the short axis surface, not the long axis surface of the needle-shaped iron oxide fine particles, is adsorbed or fixed to the surface of the O-shaped or C-shaped hematite particles, and the needle-shaped iron oxide fine particles are Since the specific surface area is large due to the structure that they do not overlap with each other, there are many contact portions with the atmosphere or gas, and therefore, the surface of the acicular iron oxide fine particles can be effectively utilized.

Next, conditions for implementing the present invention will be described.

In the present invention, the O-shaped or C-shaped hematite particles are used to prepare a suspension having a pH of 2 or more containing plate-like δ-FeOOH.
It is obtained by hydrothermal treatment in a temperature range of ~ 320 ° C.

Plate-like δ-FeOOH is obtained by a usual method by rapidly oxidizing an alkaline suspension containing ferrous hydroxide obtained by reacting an aqueous ferrous salt solution and an alkaline aqueous solution with an oxidizing agent or the like. Can be

If the pH is less than 2, no O-shaped or C-shaped hematite particles are formed.

If the temperature is lower than 150 ° C., the O from δ-FeOOH
No formation reaction of hematite particles having a letter shape or a C shape occurs. When the temperature exceeds 320 ° C., O-shaped or C-shaped hematite particles are generated, but the upper limit is 320 ° C. in consideration of safety on the device.

The obtained hematite particles have an O-shaped or C-shaped particle shape, and have an average maximum diameter of 0.1 to 1.0.
A μm X-ray particle diameter of ₁₀₄ surface D is 100～800A.

The needle-shaped iron oxide fine particles in the present invention have a major axis diameter of 0.01 to 0.1.
The diameter is 1 μm and the minor axis diameter is 0.005 to 0.5 μm.

When the major axis exceeds 0.1 μm or when the minor axis exceeds 0.05 μm, the contact area with the atmosphere or gas becomes small due to the small specific surface area, which is not preferable as an adsorbent. As described above, the lower limit of the major axis is about 0.01 μm and the lower limit of the minor axis is 0.00
Since it is about 5 μm, the needle-like iron oxide fine particles obtained by heat-treating the iron oxide-containing fine particles in air also have a lower limit of the major axis of about 0.01 μm and a lower limit of the minor axis of 0.005 μm.
It is about.

The acicular iron oxide fine particles can be obtained by heat-treating the iron oxide-containing fine particles in the air by a conventional method, in particular, by heat-treating in the range of 300 to 550 ° C. In this case, when the needle-like hydrous iron oxide fine particles are acicular α-FeOOH fine particles, they become needle-like hematite fine particles by heat treatment, and when they are needle-like γ-FeOOH fine particles, they become needle-like maghemite fine particles by heat treatment.

As the acicular hydrous iron oxide fine particles, α-FeOOH, β-FeO
OH, γ-FeOOH and the like, α-FeOOH fine particles, for example,
Aqueous ferric sulfate solution in the presence of urea at 100 ° C or lower, especially 90-1
By a method of heating at 00 ° C, β-FeOOH fine particles are, for example, a method of heating an aqueous ferric chloride solution in the presence of urea at 100 ° C or less, particularly 90 to 100 ° C, and γ-FeOOH fine particles are: For example, it can be obtained by a method of subjecting an aqueous ferrous chloride solution to air oxidation at a temperature of 10 ° C. or lower.

In the present invention, the adsorption or fixation of the needle-like iron oxide fine particles on the surface of the O-shaped or C-shaped hematite particles is determined by O
After mixing the suspension containing hematite particles exhibiting the letter shape or C shape and the suspension containing the needle-shaped hydrous iron oxide fine particles,
After that, it may be heat-treated in air.
In this case, the mixed solution is prepared, for example, by separately preparing a suspension containing O-shaped or C-shaped hematite particles and a suspension containing needle-shaped iron oxide-containing fine particles, and then mixing them. Any method of producing needle-like hydrous iron oxide particles in a suspension containing hematite particles having a C-shape may be used. In preparing this mixed solution, the O-shaped or C-shaped hematite particles may be removed. Needle-like hydrous iron oxide fine particles are adsorbed on the surface. The adsorbed needle-shaped hydrous iron oxide fine particles
Some or all of them adhere due to the heat treatment in the air.

〔Example〕

Next, the present invention will be described with reference to Examples and Comparative Examples.

Incidentally, the maximum diameter of the particles in the following Examples and Comparative Examples, the major axis and the minor axis are all shown by the average value of the values measured from the electron micrograph, the specific surface area is BET
It was shown by the value measured by the method.

Example 1 An alkaline suspension of pH 13 consisting of 1 mol of δ-FeOOH particles having a plate surface diameter of 0.3 μm and 0.1 mol of NaOH was placed in an autoclave for 20 minutes.
Heated to 0 ° C. and held at this temperature for 3.0 hours with mechanical stirring to produce a reddish brown precipitate. After cooling to room temperature,
The reddish-brown precipitate was separated, washed thoroughly with water and dried.

The obtained red-brown particle powder is hematite as shown in the X-ray diffraction shown in FIG. 1 and has an average maximum diameter of 0.3 as apparent from the electron micrograph (× 50,000) shown in FIG.
The particles were O-shaped or C-shaped particles having a size of μm.

Further, X Sentsubu径in ₁₀₄ surface D is 380 Å, a specific surface area of 18.0m ² / g.

O-shaped or C-shaped hematite particle powder
5 g of an aqueous ferric sulfate solution containing Fe ³⁺ 0.1 mol / in a water suspension obtained by dispersing 5 g in 0.5
A 1.0 mol / urea aqueous solution 0.2 was added to adjust the total volume to 1, and then heated at 95 ° C. for 5 hours to form a precipitate, followed by separate washing with water and drying.

As a result of X-ray diffraction, a peak of hematite and a peak of α-FeOOH were observed in the obtained dry particle powder, and as a result of observation with an electron microscope, the particle surface of the hematite particle powder having an O-shape or C-shape was observed. The short axis surface of the acicular α-FeOOH is adsorbed, and the surface of the O-shaped or C-shaped hematite particles has a long axis of 0.05 μm and a short axis of 0.01 μm. It was in the form of being covered by a coating.

This dried particle powder was heat-treated in air at 300 ° C. for 1.5 hours.

In the obtained heated particle powder, only a hematite peak was recognized as shown in the X-ray diffraction shown in FIG. In the figure, peak A is hematite. Further, as is clear from the electron micrograph (× 100,000) shown in FIG. 4, the short-axis surface of the acicular hematite particles is adsorbed or fixed to the surface of the O-shaped or C-shaped hematite particles, and the O-shaped or C
This was a composite iron oxide particle powder in which needle-like hematite particles having a major axis of 0.05 μm and a minor axis of 0.01 μm were barbed and coated on the surface of the hematite particles having a letter shape. As is clear from the figure, the hematite particle powder having an O-shape or a C-shape has a larger contact portion with the acicular hematite particles because it has voids compared to the hematite particles having a needle-like or plate-like shape. As a result, it is recognized that a large amount of acicular hematite particles can be adsorbed.

The specific surface area of the composite iron oxide particles was 120 m ² / g.

Example 2 An alkaline suspension having a pH of 14 and comprising 1 mol of δ-FeOOH particles having a plate surface diameter of 0.6 μm and 1 mol of NaOH was placed in an autoclave for 280 minutes.
C. and held at this temperature for 3.0 hours with mechanical stirring to produce a red-brown precipitate. After cooling to room temperature,
The reddish-brown precipitate was separated, washed thoroughly with water and dried.

The resulting reddish-brown particle powder was hematite as a result of X-ray diffraction.
The particles had an O-shape or C-shape of 0.6 μm.

Further, X Sentsubu径in ₁₀₄ surface D is 670A, the specific surface area was 13.0m ² / g.

O-shaped or C-shaped hematite particle powder
5 g of an aqueous ferric chloride solution containing Fe ³⁺ 0.05 mol / in a water suspension obtained by dispersing 5 g in 0.5
0.5 mol / aqueous urea solution 0.2 was added to adjust the total volume to 1, then heated to 90 ° C., and maintained at this temperature for 3.0 hours while mechanically stirring to form a precipitate.
Separately, washed with water and dried.

As a result of X-ray diffraction, a peak of hematite and a peak of β-FeOOH were observed in the obtained dried particle powder, and as a result of observation with an electron microscope, a needle was formed on the surface of the hematite particles having an O-shape or C-shape. The short-axis surface of the β-FeOOH-like fine particles is adsorbed, and the surface of the O-shaped or C-shaped hematite particles is turned into needle-like β-FeOOH fine particles having a long axis of 0.03 μm and a short axis of 0.02 μm. In a covered form.

The dried particle powder was heat-treated in air at 350 ° C. for 0.5 hour.

As a result of X-ray diffraction, only the peak of hematite was observed in the obtained heated particle powder, and the short axis of the acicular hematite particle was observed on the surface of the O-shaped or C-shaped hematite particle as a result of electron microscopic observation. Composite iron oxide in the form of O- or C-shaped hematite particles whose surfaces are adsorbed or fixed to form barbed needle-like hematite particles having a major axis of 0.03 μm and a minor axis of 0.02 μm. It was a fine particle powder. O-shaped or C-shaped hematite particle powder has voids compared to needle-shaped, plate-shaped, etc.-shaped hematite particles, and therefore has a large contact portion with needle-shaped hematite particles. It is recognized that hematite particles can be adsorbed.

The specific surface area of the composite iron oxide particles was 85 m ² / g.

Example 3 A suspension in which 1 mol of δ-FeOOH particles having a plate surface diameter of 0.15 μm was adjusted to pH 4.5 was heated to 200 ° C. in an autoclave, and kept at this temperature for 3.0 hours while mechanically stirring to obtain a reddish brown precipitate. Was generated. After cooling to room temperature, the reddish-brown precipitate was separated, washed sufficiently with water, and dried.

The resulting reddish-brown particle powder was hematite as a result of X-ray diffraction.
The particles were O-shaped or C-shaped particles of 0.2 μm.

Further, X Sentsubu径in ₁₀₄ surface D is 200 Å, a specific surface area of 27.5m ² / g.

O-shaped or C-shaped hematite particle powder
Ferrous chloride aqueous solution containing 5 mol of Fe ²⁺ 0.05mol / in water suspension obtained by dispersing 5g in 0.5 water
After adding 0.3 and a 0.3 solution of NaOH 0.04 mol / at 5 ° C. and further adjusting the total volume to 1.5 by adding water, air oxidation was performed for 2 hours while maintaining the temperature at 7.5 ° C. The solution is then brought to a temperature of 50
The precipitate was formed by performing air oxidation for 7 hours while maintaining the pH at 4.5 ° C. and then separately washed with water and dried.

As a result of X-ray diffraction, a peak of hematite and a peak of γ-FeOOH were observed in the obtained dry powder, and a needle was formed on the surface of the hematite particle powder having an O-shape or C-shape as observed by electron microscopy. The surface of the O-shaped or C-shaped hematite particles having the short-axis surface of the state γ-FeOOH adsorbed thereon has a needle-like γ-phase having a long axis of 0.05 μm and a short axis of 0.02 μm.
FeOOH had a spine-like and broken form.

This dried particle powder was heat-treated in air at 320 ° C. for 1.5 hours.

As a result of X-ray diffraction, a peak of hematite and a peak of γ-Fe ₂ O ₃ were observed in the obtained heated particle powder, and as a result of observation with an electron microscope, O-shaped or C-shaped particles of hematite particles were observed. The minor axis surface of the acicular maghemite particles is adsorbed or fixed on the surface, and the surface of the O-shaped or C-shaped hematite particles has a major axis of 0.05 μm and a minor axis of 0.02 μm.
The composite iron oxide particles were in a form in which the needle-like maghemite particles were barbed and covered. The O-shaped or C-shaped hematite particle powder has voids as compared with the hematite particles having a needle-like or plate-like shape, so that the needle-like γ-
It was confirmed that the contact portion with the FeOOH fine particles was large, and as a result, it was possible to adsorb a large amount of acicular maghemite particles.

The specific surface area of the composite iron oxide particles was 65 m ² / g.

Comparative Example 1 0.5 mol of ferric chloride aqueous solution 1 containing 0.05 mol / Fe ³⁺
The mixed aqueous solution adjusted to a total volume of 3 by further adding water to 1 / urea 1 was heated to 90 ° C., and kept at this temperature for 3.0 hours while mechanically stirring to form a yellow-brown precipitate.

A part of the reaction solution was extracted, and separation was attempted using a No. 5C piece of paper (manufactured by Toyo Paper Co., Ltd.).

Then, a part of the reaction solution was evaporated to dryness to obtain a yellow-brown particle powder.

The obtained yellow-brown particle powder was analyzed by X-ray diffraction,
The particles were needle-shaped particles having a diameter of 0.08 μm and a minor axis diameter of 0.04 μm.

〔The invention's effect〕

The composite iron oxide particle powder according to the present invention has an O-shaped or C-shaped particle shape as shown in the above Examples, and has an average maximum diameter of 0.1 to 1.0 μm and D ₁₀₄
The surface of the hematite particles having an X-ray particle diameter of 100 to 800 ° on the surface has a major axis diameter of 0.01 to 0.1 μm and a minor axis diameter of 0.005 to
Due to the fact that the needle-shaped iron oxide fine particles having a particle diameter of 0.05 μm are adsorbed or fixed, the particles have excellent powder characteristics such as excess and workability. It is suitable as an adsorbent for nitrogen oxides and the like, a deodorant and the like.

[Brief description of the drawings]

FIGS. 1 and 2 are an X-ray diffraction pattern and an electron micrograph (× 50,000) of the O-shaped or C-shaped hetamitic particles obtained in Example 1, respectively. In FIG. 1, peak A is hematite. FIGS. 3 and 4 are X-ray diffraction diagrams of the composite iron oxide particle powder in which the O-shaped or C-shaped hematite particles obtained in Example 1 are coated with barbed needle-like hematite particles. And an electron micrograph (× 100,000). In FIG. 3, peak A is hematite.

Claims (2)

(57) [Claims] (1) The particle shape is O-shaped or C-shaped, and the average value of the maximum diameter is 0.1 to 1.0 μm, and D ₁₀₄
The surface of the hematite particles having an X-ray particle diameter of 100 to 800 ° on the surface has a major axis diameter of 0.01 to 0.1 μm and a minor axis diameter of 0.005 to
Composite iron oxide particle powder comprising composite iron oxide particles having adsorbed or fixed needle-like iron oxide fine particles of 0.05 μm. 2. A suspension containing plate-like δ-FeOOH having a pH of 2 or more is prepared by adding
It is not O-shaped particle shape by hydrothermal treatment in the temperature range of 0 to 320 ° C. and exhibited a C-shaped, and the average value of the maximum diameter of the X-ray particle diameter of ₁₀₄ surface D a 0.1~1.0μm
A suspension containing the O-shaped or C-shaped hematite particles, and a needle-like hydrous solution having a major axis diameter of 0.01 to 0.1 μm and a minor axis diameter of 0.005 to 0.05 μm. By mixing with a suspension containing iron fine particles to form composite iron oxide particles in which the needle-like hydrous iron oxide fine particles are adsorbed on the surface of the O-shaped or C-shaped hematite particles, and then forming the particles. Needle-like iron oxide fine particles having a major axis diameter of 0.01 to 0.1 μm and a minor axis diameter of 0.005 to 0.05 μm are adsorbed or adsorbed on the surface of O-shaped or C-shaped hematite particles characterized by being subjected to heat treatment in air. A method for producing composite iron oxide particle powder comprising composite iron oxide particles adhered.