JPH0632673A - Alumina-based porous body - Google Patents

Abstract

PURPOSE:To provide an alumina porous body utilizable as a carrier for a heterogeneous catalyst for cleaning waste gases used in catalyst combustors, internal combustion engines, treating petroleum fractions, organic synthesis, etc. CONSTITUTION:The objective alumina-based porous body has >=2.0ml/g total pore volume, 50-500m<2>/g specific surface area and 0.1-6.0ml/g pare volume of pores having <=100nm pore radius, >=30% pore volume having 10-100nm pore radius and one or more peaks of the pore radius above 0.01mum pore radius and is excellent in heat resistance.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an alumina porous material which can be suitably used for purification of exhaust gas of an internal combustion engine, treatment of petroleum fractions which are reacted under high pressure, carrier for heterogeneous catalysts for organic synthesis and the like. Regarding the body

[0002]

2. Description of the Related Art Heterogeneous catalyst carriers used for such applications have a high specific surface area in order to obtain a wide reaction active area and a high specific surface area even by various treatments, and in purification of exhaust gas of an internal combustion engine. Is about 850 ° C, 200 ~ in petrochemical processes, organic synthesis, etc.
It must have heat resistance to withstand high temperatures such as 600 ° C.

The need for heat resistance in this heterogeneous catalyst carrier is becoming more severe. For example, as an exhaust gas purifying catalyst, with the tightening of NOx regulations, it is progressing from the conventional one-step oxidation catalyst treatment to a two-step oxidation-reduction catalyst. Therefore, the catalyst layer has a higher temperature in the engine. Need to be close to the
Stable heat resistance before and after has come to be required.

On the other hand, in recent years, a catalytic combustion method, which uses a catalyst to promote the reaction between fuel and oxygen, has been receiving attention. This catalytic combustion method has advantages such as complete combustion at a low temperature, complete combustion in a wide range of fuel / air ratio, and less generation of thermal knox. In order to establish this technology, it is necessary to develop a catalyst carrier that has stable heat resistance at 1000 ° C or higher.

As the alumina porous body conventionally used for such applications, for example, Catalyst Course 5, Catalyst Design, p.
128-133 (1985) has a specific surface area of 100-300 m ² / g and a pore volume of 0.5-1.5.
ml / g, a boehmite having a controllable pore radius peak position is known.

[0006] Further, a transition alumina having a γ phase as a main component, which is obtained by heat-treating a hydrolysis product of an aluminum alkoxide, is also known, but has a specific surface area of 100 to 300 m ² /
g, the pore volume is 0.4 to 0.6 ml / g, the pore radius peak and most of the pores are 10 nm or less.

Further, transition alumina containing a δ phase as a main component is also known, which has a specific surface area of 50 to 100 m ² /
g, the pore volume is 0.4 ml / g or less, the pore radius peak and most of the pores are 10 nm or less.

Further, high-strength alumina containing an α phase as a main component is also known, and its specific surface area is 10 m ² /
Below g, the pore volume is extremely small.

As a catalyst carrier having such heat resistance, it has been attempted to use porous alumina capable of retaining a high specific surface area even after heat treatment.

As such alumina, it has been known to use γ-alumina having a high specific surface area which is synthesized by neutralization or exchange decomposition of aluminum salt or aluminate, or hydrolysis of aluminum amalgam or aluminum alkoxide.

However, γ-alumina is 1000
Transition to α-alumina at ˜1100 ° C. Therefore, the specific surface area is drastically reduced, the reaction active area is reduced, and it cannot be used in a high temperature range of 1000 ° C or higher, and the applicable temperature is 6
The limit is 00 ° C.

Further, Japanese Patent Publication No. 58-53569 discloses an α-alumina carrier having a knitting structure, and the γ → α transition of alumina in the process of production thereof causes a sudden increase in specific surface area and strength. Is reduced. In particular, the specific surface area of the obtained carrier is at most 30 m ² / g, which is extremely low as compared with γ-alumina, which is inferior in catalyst support ability.

Further, many inventions have been disclosed regarding the control and structure of the pore distribution of the alumina catalyst carrier.

For example, JP-A-57-123820, JP-A-57-135721, and JP-A-57-1
Japanese Patent No. 70822 discloses that a bimodal pore radius distribution is obtained by adding carbon black,
Further, in JP-A-58-252, it is possible to adjust the pore volume by heat-treating two or more kinds of oxides under steam, and further in JP-A-58-119341. , The alumina compound solution was spray-dried to have a total pore volume of 0.8 to 1.7 ml / g and a specific surface area of 80 to 135 m.
It is disclosed to obtain a porous surface of ² / g. Further, JP-A-58-216740 discloses that a multimodal pore size distribution is obtained by mixing two or more kinds of boehmite sols, and further JP-A-1-254254 discloses. A method by spray drying is disclosed.

However, all of the above patent documents relate to the control of the pore structure in a relatively low temperature range,
There is no disclosure about improvement in heat resistance of the alumina porous body used in a high temperature range of 1000 ° C. or higher.

The only one disclosed in Japanese Patent Laid-Open No. 3-199120 is an alumina porous body having a large specific surface area and excellent heat resistance at high temperature, by drying the alumina airgel under the condition of exceeding the critical temperature and the critical pressure. It is disclosed.

However, none of the alumina porous bodies is sufficient for long-term use under high temperature or high pressure.

[0018]

The present invention is based on the conventional γ-
It is intended to provide an alumina-based porous body which has higher heat resistance than alumina and has a higher active surface than α-alumina, and whose activity is retained for a long time even under high temperature and high pressure.

[0019]

The alumina-based porous material of the present invention has a total pore volume of 2.0 ml / g or more, and the specific surface area and the pore volume due to the pores having a pore diameter radius of 100 nm or less are respectively 50-500 m ² / g and 0.1-6.0 m
1 / g and the pore volume of 10 to 100 nm is 100
30% or more of the pore volume of not more than nm and a pore radius of 0.
It has excellent heat resistance, which is characterized by having one or more peaks of pore size at 01 μm or more.

Further, all or most of the crystal phase is γ
It is composed of a phase or theta phase and also has excellent water resistance.

The alumina porous body composed of all or most of the crystal phase of the γ phase has a total pore volume of 2.5 ml.
/ G or more and the pore diameter radius is 100 nm or less, the specific surface area and the pore volume of the pores are 200 to 500 m ² respectively.
/ G and 0.5 to 6.0 ml / g, and 10 to 1
The pore volume of 00 nm is 40 of the pore volume of 100 nm or less.
%, And has one or more peaks of pore diameter at pore diameter radius of 0.01 μm or more, and has high pore volume and specific surface area.

Further, all or most of the crystal phase is θ.
The alumina porous body composed of phases has a pore radius of 10
The specific surface area and pore volume due to pores of 0 nm or less are 50-250 m ² / g and 0.1 to 1.0 ml / g, respectively, and the pore volume of 10 to 100 nm is 100 nm or less. 30% or more and a pore diameter radius of 0.0
It has one or more pore diameter peaks at 1 μm or more, and has a smaller specific surface area and pore volume due to pores having a pore radius of 100 nm or less compared to alumina composed of γ phase, but conversely, It has excellent heat resistance at high temperatures.

The physical properties in the present invention are measured by the BET method.

The pore volume of 100 nm or more is Hg
The result measured by the press fitting method is shown.

The alumina according to the present invention can be manufactured by the following method.

The chemical formula Al (O
R) ₃ and an alkoxide represented by O. 5 to 2 mole times polyfunctional organic compound (β-ketoester, β-diketone, etc.)
The alcohol mixed solution or the alcohol solution of the compound substituted with the polyfunctional organic compound of Al (OR) ₃ is hydrolyzed with 0.5 to 2 times mol of water of the alkoxide to prepare a gel. The gel thus obtained was placed in an autoclave at 270 ° C. and 25
Heat treatment is performed under the condition of 0 atm to obtain a dry gel. The obtained gel is heat-treated at 500 to 1200 ° C. By changing the firing time within that temperature range, it is possible to obtain an alumina porous body having a desired specific surface area and pore volume and excellent in water resistance and heat resistance.

[0027]

The porous alumina material according to the present invention has an excellent pore distribution.

First, in the pore volume, conventionally, it is 1.5
What was less than or equal to ml / g has a larger pore volume than that. It has fine pores of 10 nm or less and a high specific surface area. There is a peak of the pore diameter in the pore radius region of 10 nm or more.

Due to the fine pores and the specific surface area resulting therefrom, the surface has a high catalytic activity. Pore with a radius of 10 nm or more and a large pore volume, that is,
It will have a large geometric volume.

[0030]

【Example】

Example 1 Ethyl acetate aluminum diisopropylate 27
After dissolving 4 g in 500 ml of ethanol, 72 ml of water was added and hydrolyzed to obtain a gel. The obtained gel was heated in an autoclave at 270 ° C. and 250 atm for 48 hours to obtain a dried gel. Atmosphere 500 ° C, 800
5 ° C, 1000 ° C, 1100 ° C, and 1200 ° C
Heat treated for hours. The obtained dried gel was boehmite and had a pore diameter radius of 100 nm or less and a pore volume of 4.11 ml / g and 2.01 ml / g at 100 nm or more, respectively. The γ phase changes to the θ phase by heat treatment. 10
Pore volume of 0 nm or less is 4.07 ml / g to 0.1 m
It varied in the range of 1 / g. The pore volume above 100 nm varied from 4.0 to 2.0 ml / g. Further, there is a peak of pore distribution at a location where the pore radius is about 30 nm, and the pore volume of the pore diameter radius of 10 to 100 nm is 100.
The ratio of the pore volume of nm or less to the pore volume varied in the range of 96 to 40%. The crystal phase and pore volume of the dried gel after heat treatment at each temperature are shown in Table 1 together with Comparative Example 1.

[0031]

[Table 1] FIG. 1 shows the pore size distribution of the alumina of Example 1 heat-treated at 600 ° C. and commercially available γ-alumina measured by the BET method.
The alumina according to the present invention has a pore peak in the vicinity of 20 nm and pores evenly exist in the area of 10 nm or less.
On the other hand, commercially available alumina has a pore peak near 4 nm, but almost no pore exists above 10 nm. Figure 2
It shows a pore distribution of 0.1 μm or more as measured by the Hg press-fitting method.
There is a pore peak near 0.5 μm. Commercially available alumina has no pores in this pore size range. A in alcohol
By changing the metal concentration and the drying conditions, it is possible to obtain an alumina porous body having characteristics other than those exemplified in the table. Further, it can be easily inferred that an alumina-based porous body in which other components such as rare earths and precious metals are mixed in advance has the same characteristics.

Comparative Example 1 Commercially available γ-alumina (trade name PUR, manufactured by Condea)
The pore volume and specific surface area of LOX: SBa-180) were measured. The pore volume of 100 nm or less is about the same as 0.48 ml / g, but the peak of the pore distribution is seen only in the pore radius of 4 nm, and the pores of 100 nm or more hardly exist. Further, this powder hardly shows a transition to the α phase at heat treatment temperatures up to 1000 ° C and retains a specific surface area of 100 m ² / g or more, but it rapidly transforms to the α phase by heat treatment at 1100 ° C. The specific surface area was reduced to 18.5 m ² / g, and the heat resistance was inferior to the alumina porous body of the present invention.

Example 2 The gel obtained in Example 1 and the powder after heat treatment were dispersed in water, and then heat treated again at a temperature up to 1200 ° C. for 5 hours. When the unheated powder was dispersed in water, the specific surface area was remarkably reduced, and the transition to the α phase was already observed by the heat treatment at 1100 ° C. No transition to α phase was observed in the powder in which γ phase or θ phase was generated by preheating. Further, it can be seen that the high pore volume is maintained. The formation of γ and θ phases is effective for water resistance and heat resistance after treatment with water. In particular, the powder in which the θ phase is generated has almost no change in specific surface area and pore volume. 1100 ° C
Table 2 shows the crystal phase and the pore volume after the reheating treatment for 5 hours. Table 3 shows changes in specific surface area after preheating, after water dispersion and after reheating.

[0034]

[Table 2]

[Table 3] Comparative Example 2 Commercially available γ-alumina was treated in the same manner as in Example 2 and the change in specific surface area was measured. 100 m ² / g below 1000 ° C
Although the specific surface area was maintained to some extent, a sharp decrease in the specific surface area was observed at 1100 ° C or higher. This powder has already been converted to α at 1100 ° C., and as shown in Table 2, the pore volume is almost 0.04 ml / g, which is significantly lower than that when untreated. Table 3 shows the changes in specific surface area after dispersion in water and after reheat treatment.

Example 3 The gel obtained in the same manner as in Example 1 was heat-treated in an autoclave at 270 ° C. and 25 atm for 2, 5 and 10 hours to obtain a dry gel. After heat treatment at 600 ℃ for 5 hours,
The specific surface area and pore size distribution were measured. The results are shown in Table 4. All of the γ-phases were main crystals, and the specific surface areas were 300 m ² / g or more, 100 nm or less, and the pore volumes at and above 300 m ² / g were 4.0 and 2.0 ml / g or more, respectively. The peak of the pore size distribution moved from 13 nm to 30 nm as the heat treatment time increased. Also, the pore radius is 10
The ratio of the pore volume of ˜100 nm to the pore volume of 100 nm or less was 90% or more. By adjusting the conditions and the heat treatment, it was possible to adjust the alumina porous body having the pore volume and pore distribution within the range of the present invention and the binder phase.

[0036]

[Table 4]

[0037]

The alumina porous body of the present invention has the following effects.

(1) It has an excellent pore distribution that can be used as a catalyst carrier having excellent heat resistance and water resistance, and has a fine catalytic activity surface due to its fine pores and specific surface area.

(2) Since it has excellent water resistance and heat resistance, it is effective for the treatment with water such as washcoat, the catalytic reaction system of water system and the reaction system at high temperature.

[Brief description of drawings]

FIG. 1 shows the pore size distribution of the alumina of Example 1 heat-treated at 600 ° C. and a commercially available γ-alumina measured by the BET method.

FIG. 2 shows a pore distribution of 0.1 μm or more measured by the Hg press-fitting method.

Claims (3)

[Claims] 1. A total pore volume of 2.0 ml / g or more,
The specific surface area and pore volume of pores having a pore diameter radius of 100 nm or less are 50 to 500 m ² / g and 0.1 to, respectively.
Alumina having a volume of 6.0 ml / g, a pore volume of 10 to 100 nm is 30% or more of a pore volume of 100 nm or less, and a peak of one or more pore diameters in a pore radius of 0.01 μm or more. Porous body. 2. An alumina-based porous body in which all or most of the crystal phase is composed of γ phase has a total pore volume of 2.5 m.
The specific surface area and the pore volume due to the pores having a pore diameter radius of 100 nm or less are 200 to 500 m, respectively.
² / g and 0.5-6.0 ml / g, and 10-
The pore volume of 100 nm is 4 of the pore volume of 100 nm or less.
An alumina porous body having 0% or more and one or more pore diameter peaks at a pore radius of 0.01 μm or more. 3. An alumina-based porous body composed of all or most of the crystal phase having a θ phase has a pore radius of 100 n.
The specific surface area and pore volume due to pores of m or less are 5
0-250 m ² / g and 0.1-1.0 ml / g,
Further, an alumina porous body having a pore volume of 10 to 100 nm of 30% or more of a pore volume of 100 nm or less and having one or more peaks of pore diameter at a pore radius of 0.01 μm or more.