JP2515379B2 - Heat-resistant inorganic porous composition and catalyst carrier comprising the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-resistant inorganic oxide composition and a catalyst carrier comprising the same, which can withstand use under high temperature conditions. The present invention relates to a heat-resistant inorganic oxide composition comprising silica-alumina in which silica is highly dispersed, and a catalyst carrier comprising the same.

[Conventional technology]

Catalysts used under high temperature and high humidity conditions such as gas turbines, kerosene and gas heaters, oil and gas water heaters, heavy oil combustion equipment, fuel cell reformers, etc. As carriers for steam reformer catalysts and various combustion exhaust gas purification catalysts, cordierite (2MgO ・ 2Al ₂ O ₃・ 5SiO ₂ ) and mullite (3
Al ₂ O ₃ -2SiO ₂ )) and the like have been proposed, but since they have heat resistance but are not porous, they are coated with a porous material at the time of use to form a porous carrier layer. The formed one is used. Alumina is generally used as the porous material, and a carrier layer made of this porous material is used as a catalyst by supporting a catalytically active metal component. However, under high temperature conditions, alumina transforms its crystalline form into α-type, resulting in a smaller specific surface area, lower dispersion of supported active metal components, and rapid deactivation of catalytically active metal components. To do.

Further, there is a report that lanthanum β-alumina (LaO ₃ · 11Al ₂ O ₃ ) and barium alumina (BaO · 6Al ₂ O ₃ ) have high heat resistance (Japanese Patent Laid-Open No. 62-153158), but both have high temperature firing. The specific surface area afterwards is not large enough to be satisfied,
In addition, there is a problem that the cost becomes high for commercial use.

Further, a basic compound is added to a mixed aqueous solution of alumina hydrate and colloidal silica to thicken the mixed aqueous solution, and the resulting gel is dried and burned to obtain a heat-resistant catalyst carrier composition. (Japanese Patent Application Laid-Open No. 61-287446), and it has a structure layer of a sintered ceramic material and a high surface area carrier layer of a porous oxide integrated with the structure layer. A monolithic catalyst carrier having an oxide carrier layer containing 50 to 93% by weight of alumina and 7 to 50% by weight of silica as main components has been reported (JP-A-61-242639). When used at a high temperature of 1200 ° C for a long time, there is a problem that the specific surface area is rapidly reduced.

[Problems to be Solved by the Invention]

The present invention is based on the findings obtained as a result of various examinations of conventional techniques, and the aggregation of silica is suppressed even when kept for a long time under high temperature and high humidity conditions, and silica bonded to alumina is It is an object of the present invention to provide a heat resistant inorganic oxide composition having a uniform phase and having a large specific surface area.

Another object of the present invention is to provide a catalyst carrier which can retain a large catalytic activity even when it is kept at high temperature and high humidity for a long time.

[Means for solving the problem]

The present invention is composed of silica and alumina, and the content of silica is in the range of 2% by weight to 30% by weight. In the nuclear magnetic resonance measurement ( ²⁹ Si-NMR measurement), silicon rubber (-21.9 p
pm) as a reference peak, the peak area of −50 to −80 ppm is 0 to 25% of the peak area of −50 to −130 ppm, and the peak area of −110 to −130 ppm is −50 to −130 ppm. A heat-resistant inorganic porous composition having an area of 0 to 10% is provided.

The present invention is also characterized by providing a catalyst carrier comprising this heat-resistant inorganic porous composition.

The content of silica in the heat-resistant inorganic porous composition of the present invention is in the range of 2% by weight to 30% by weight, preferably 5% by weight to 10% by weight. When the content of silica is less than 2% by weight, the heat-resistant inorganic porous composition of the present invention cannot be obtained, and the crystal structure of alumina becomes α due to high temperature firing, and the specific surface area decreases. On the other hand, when the content of silica exceeds 30% by weight, the component ratio of mullite increases due to high temperature firing, the specific surface area decreases, and the reaction activity decreases.

The heat-resistant inorganic oxide composition of the present invention has a silicone rubber (-21.9 pp) in nuclear magnetic resonance measurement ( ²⁹ Si-NMR measurement).
m) as a reference peak, the peak area of −50 to −80 ppm is 0 to 25% with respect to the peak area of −50 to −130 pp, preferably 2 to 22%, and the peak area of −110 to −130 ppm is It is necessary to be 0 to 10%, preferably 0 to 8% with respect to the peak area of -50 to -130 ppm.

The bonding state of silica-alumina in the alumina-silica composition is Is.

²⁹ Si with silicon rubber (-21.99 ppm) as the reference peak
-When NMR measurement is performed, the number of Al bonded to 1 SiO is 4
The number of the structures represented by the above formula (I) has a peak position at −80 ppm, and when the number of Al is the same, the number of the structures represented by the above formula (II) is −88 ppm. The peak position is at -97 ppm when it has two structures represented by the above formula (III), and it is at -105 ppm when it has the structure represented by the above formula (IV) where the number of Al is one. The above (V) in which aluminum is not substituted
The structure of has a peak position at -111 ppm.

FIG. 4 is a diagram illustrating the result of ²⁹ Si-NMR measurement of the silica-alumina composition, the horizontal axis shows the shift value from the reference peak, and the vertical axis shows the relative absorption intensity.

In FIG. 4, the peak positions of the above formulas (I) to (V) are indicated by a to e, respectively. As shown by the dotted lines, each intensity curve shows a relative relative intensity with respect to the shift value from the reference peak. In order to show, the measurement result is shown as the sum of absorption values based on each structure, and shows the composition of the present invention (I
The maximum value of the relative absorption intensities of the absorption curves corresponding to the equations I) to (IV) is not clearly shown.

However, this measurement reveals at least the relative abundance of bound states corresponding to formulas (I) and (V) above. When the relative strength curve moves to the bonding state part of the above formula (I) as a whole, Al / Si approaches 4, and when the relative strength curve moves to the bonding state part of the above formula (V) as a whole, dispersion occurs. Property deteriorates, and Al / Si approaches 0.

Therefore, in defining the composition of the present invention,
As shown in the figure, the area (s ′) formed by the curve and the reference line A having a shift value or more when the Al / Si ratio is 4 and the area (s ′) which is the shift value or less when the Al / Si ratio is 0 ( s ″) was measured, and the shape of the composition of the present invention was defined by the ratio of each area to the total area S formed by the curve and the reference line A.

In addition, ²⁹ Si-NMR measurement was performed by JEOL Ltd., JNM-GX 2
Type 70 is used to measure ²⁹ Si nuclei (53.54MHZ) in CP / MAS (Cr
oss Polari-zation, Magic Angle Spinning) method. Use silicone rubber as a standard substance,
−21.90ppm was the standard.

Next, a method for producing the heat resistant inorganic porous composition of the present invention will be described.

The method for producing the silica-alumina composition of the present invention is produced by a coprecipitation method and uses sodium aluminate and water glass as an alumina source and a silica source, respectively, and makes the atomic ratio of Al / Si 2 to 3. By adjusting the pH to 8 in the aqueous nitric acid solution, or by dropping sodium aluminate and water glass into the water, or by simultaneously dropping the aqueous sodium aluminate solution, water glass solution and nitric acid solution into the water. Step of reacting.

If necessary, the silica content is adjusted to 2 to 30% by weight while maintaining the pH at 8.

Sodium aluminate is used in the form of an aqueous solution, and its concentration is about 0.1 to 4.0 mol of its soluble salt, preferably about 0.3 to 2.0.
It is good to set it in the molar range.

Silica is an alkali metal silicate (Na ₂ O: SiO ₂ = 1: 2 to 1: 4
Aqueous solution is used, and the concentration thereof is about 0.1 to 10 mol, preferably about 0.3 to 5.0 mol.

The usage ratio is such that the atomic ratio of aluminum to silicon is 2 to
Mix to give 3.

In order to adjust the content of silica in the silica-alumina composition thus formed to 2 to 30% by weight,
If necessary, add a predetermined amount of aluminum sulfate aqueous solution and react by maintaining the pH at 8 with nitric acid,
Allow to settle.

The silica-alumina composition of the present invention can be produced by the above-mentioned production method to highly disperse silica, and can be a composition mainly composed of a bonded state represented by the above formulas (II) to (III). Is.

The precipitate formed is filtered, washed with an aqueous solution of ammonium carbonate, ammonium chloride or ammonium nitrate, and dried in air at 80 to 200 ° C, preferably 90 to 150 ° C.

The silica-alumina composition after drying is 400 to 1200 ° C.,
The heat-resistant inorganic porous composition of the present invention can be produced by preferably firing in air at 500 to 1000 ° C.

Next, the shape of the catalyst carrier of the present invention will be described. That is, the silica-alumina precipitate collected by filtration is dried,
In addition, if necessary, crush the powder obtained, or
Alternatively, without firing, water is added to this and the mixture is subjected to humidity control.
Alternatively, the precipitate (hydrogel) may be mixed. This mixture is extruded to obtain an extruded body, a honeycomb shape, a granular shape, etc.
Baking in air at ℃, preferably 500-1000 ℃.

On the other hand, when a catalyst such as mullite, silica-alumina, cordierite, or honeycomb is wash-coated and used as a combustion catalyst, the above powder is used as an acid (acetic acid, nitric acid, hydrochloric acid, etc.) or a base (ammonium hydroxide, etc.). ) And / or a hydrogel-added suspension of the support. Excessive deposits are purged with an inert gas (such as nitrogen), and then dried and baked. Drying in air 80-200 ℃, preferably 90-150
The firing temperature is 400 ° C to 1200 ° C, preferably 500 to 1000 ° C in the air.

Further, when the catalyst carrier of the present invention is used as a catalyst carrier for purifying automobile exhaust gas, the active metal component of the periodic table
At least one metal component selected from the group of Group VIII metals, such as iron, nickel, iron group metal components such as cobalt,
A noble metal such as platinum, palladium, iridium, rhodium, ruthenium or osmium is supported. The preferred active metal component is at least one selected from the group of platinum, palladium, rhodium, and iridium. These active metal components can be supported on the carrier as oxides in catalytically effective amounts. The preferred loading is in the range of 0.001% to 5% by weight, especially 0.005% to 2% by weight.

Further, in the composition of the present invention, an alkaline earth metal such as barium, calcium, strontium, zirconium, and magnesium, an element periodic table such as boron, scandium, and yttrium Group III metal, titanium, zirconium, hafnium One or more oxides of rare earth elements such as Group IV metal, lanthanum, cerium and thorium are added in an amount of 0.01 to 30% by weight, preferably 0.05 to 10% by weight. be able to. The method of addition is not limited, but it is preferable to coprecipitate alumina or silica at the same time.

[Action]

Generally, in the catalytic reaction, the quality of the catalyst carrier significantly affects the activity, life, selectivity or economy of the catalyst. The reaction requires a high specific surface area to proceed on the surface of the catalyst, durability as a catalyst is required, and mutual relation between these physical properties is required.

The present inventors have found that the silica-alumina composition has a silica content in the range of 2% by weight to 30% by weight, the silica is highly dispersed, and nuclear magnetic resonance measurement ( ²⁹ Si-NMR
In the measurement), the peak area of -50 to -80 ppm is -50 to -1 with silicone rubber (-21.9 ppm) as the reference peak.
0 to 25% for the peak area of 30 ppm, and -110 to -13
When the peak area of 0 ppm is 0 to 10% with respect to the peak area of -50 to -130 ppm, the aggregation of silica is suppressed even when it is kept for a long time under high temperature and high humidity conditions, and it is bonded to alumina. It has been found that a silica phase having a uniform surface area can provide a heat-resistant inorganic oxide composition having a large specific surface area. It was also found that the use of the Koku composition as a catalyst carrier is a desirable catalyst carrier that exhibits long-term reaction activity.

This silica-alumina composition uses an alumina source, and sodium aluminate and water glass as a silica source,
/ Si atomic ratio of 2-3, while adjusting the pH to 8 with an aqueous nitric acid solution, a step of dropping sodium aluminate and water glass by a coprecipitation method to react, and optionally containing silica The heat-resistant inorganic porous composition having the above-mentioned constitution can be obtained by producing the composition by the production method comprising the step of adjusting the amount to 2 to 30% by weight while maintaining the pH at 8.

In this ²⁹ Si-NMR measurement, silicone rubber (-21.9 p
pm) as a reference peak and the peak area of −50 to −80 ppm is 25% or more of the peak area of −50 to −130 ppm, for example, as shown in FIG. 2 described later,
Silica shows a state in which it is unnecessarily highly dispersed in alumina, the composition in this case is poor in heat resistance, and the peak area at −110 to −130 ppm is −50 to −130 pp.
When the content is 10% or more with respect to the peak area of m, it indicates that silica is not well dispersed in alumina, and in this case as well, it was found that the composition has poor heat resistance. .

The detailed reason for this is not clear, but in the case of a reaction mode in which silica is added to an alumina source, for example, SiO 1
It is considered that the bonded state corresponding to the above formula (I) in which the number of Al bonded to each is 4 is partially formed and silica is not uniformly dispersed. In such cases, the composition is unstable and mullite (3 Al ₂ O ₃ -2Si
It is considered that a large phase change occurs when it changes to O ₂ ).

On the other hand, in the method for producing the composition of the present invention, by adopting the coprecipitation method, it is possible to obtain a dispersion of silica in an appropriate amount by controlling the pH, and by uniformly dispersing in this way. It is considered that the material has good heat resistance because it does not undergo a phase change when it is stabilized and changes into light (3 Al ₂ O ₃ -2SiO ₂ ) during firing. Further, it is considered that when silica and alumina are not mixed and simply mixed, the silica is not dispersed in the alumina at all, the specific surface area becomes small due to the α-formation of the alumina crystal, and the heat resistance becomes poor.

Hereinafter, examples of the heat-resistant inorganic porous composition of the present invention will be described in comparison with comparative examples.

[Example 1] 1000 ml of 4 wt% sodium aluminate aqueous solution, and 25 wt%
130 ml of No. 3 water glass (JIS K-1408) aqueous solution was prepared separately. These two aqueous solutions were added dropwise to 2500 ml of ion-exchanged water stored in a reaction vessel equipped with a stirrer at room temperature while stirring to precipitate a silica-alumina hydrate having an atomic ratio of aluminum to silicon of 3. During this precipitation preparation operation, a 5% by weight aqueous nitric acid solution was added dropwise at the same time as the above two aqueous solutions were added, the pH was adjusted to 8 and the mixture was kept for 1 hour.

The silica content in the produced silica hydrate was 28.
Since it has become wt%, 14 wt% aluminum sulfate aqueous solution
The total amount of 3050 ml was added dropwise while adjusting the pH of the contents to 8 to form a precipitate.

The formed precipitate was separated by filtration, washed with water and dried in air at a temperature of 120 ° C. for 12 hours. The dried silica-alumina is 50% in the presence of air using an electric furnace.
It was calcined at a temperature of 0 ° C. for 3 hours.

As described above, a silica-alumina composition having a peak of aluminum / silicon atomic ratio of 3 to 2 in the portion where silica is forming a bond and a silica content of 10% by weight was obtained (“Composition A ])). The result of ²⁹ Si-NMR measurement of this composition is shown in FIG. CP / M at ²⁹ Si nucleus at 53.54 MHz
It was performed by AS (Cross Polari-zation, Magic Angle Spinning) method. Silicone rubber was used as a standard. The following results were obtained from FIG.

Further, each was fired at 1200 ° C. for 15 hours, 100 hours, and 200 hours to obtain three kinds of 1200 ° C. fired products.

[Example 2] The 4 wt% sodium aluminate aqueous solution in Example 1 was added.
A silica-alumina composition was prepared in the same manner as in Example 1 except that 830 ml and 3200 ml of 14 wt% aluminum sulfate aqueous solution were used.

Example 3 The 4 wt% sodium aluminate aqueous solution in Example 1 was added.
An alumina composition was prepared in the same manner as in Example 1 except that 1960 ml and 2960 ml of a 14 wt% aluminum sulfate aqueous solution were used.

[Comparative Example 1] 10% ammonia water was added to 4000 ml of 14% by weight aluminum sulfate aqueous solution to adjust the pH to 8 and then 25% by weight so that the silica content in the product was 10% by weight as in Example 1 above. No. 3 water glass (JIS K-1408) aqueous solution 130 ml
Was added to produce a silica-alumina precipitate. The resulting precipitate was aged at 60 ° C. for 3 hours using an aqueous nitric acid solution to lower the final pH to 6.2. After aging, the precipitate was filtered, washed with water, dried in air at 120 ° C for 12 hours, and then at 500 ° C.
The product was calcined in air for 3 hours to obtain a calcined product at 500 ° C. Again 1200
Calcination at 15 ℃, 100 hours, 300 hours, 3 kinds of 1200 ℃
A baked product was obtained.

[Comparative Example 2] Alumina sol (manufactured by Nishio Industry Co., Ltd.) and colloidal silica (manufactured by Nissan Chemical Industries) were suspended in water, and the final composition was mixed so that silica was 10% by weight. The alumina composition was precipitated. The precipitate is filtered, washed with water, dried in air at 120 ° C for 12 hours, and then at 500 ° C.
The product was calcined in air for 3 hours to obtain a calcined product at 500 ° C. Again 1200
Calcination at 15 ℃, 100 hours, 300 hours, 3 kinds of 1200 ℃
A baked product was obtained.

²⁹ Si-NMR measurement was performed on the 500 ° C. calcined products of the silica-alumina compositions prepared in Examples 2 and 3 and Comparative Examples 1 and 2. Comparative Example 2 and Comparative Example 3
The measurement results of are shown in FIG. 2 and FIG. 3, respectively. Although the results of the NMR measurement of Examples 2 and 3 are not shown, first, based on the respective measurement results, first, −50 to −13.
Total area S of 0ppm, then -50 to 80ppm, -1 respectively
The area s ′s ″ between the absorption intensity curve and the reference line A was measured between 10 and −130 ppm, and the respective ratios s ′ / S and s ″ / S to the total area S are shown in Table 1 below. Show.

Also, s'for the three types of fired products fired at 1200 ° C
With respect to / S and s "/ S, the same result as that of the product baked at 500 ° C was obtained.

Next, the heat resistance was evaluated by measuring the specific surface area of the 1200 ° C. calcined product having a calcining time of 15 hours, 100 hours, and 200 hours by the nitrogen adsorption method. The results are shown in Table 2 below.

[Example 4] (Method for preparing catalyst) The precipitate prepared in Example 1 was filtered and washed to obtain 120
After drying at ℃ for 20 hours, it was crushed by a ball mill. After adding water to this and kneading to make it into a clay shape, it is extruded by an extruder equipped with a die having many holes with a diameter of 1/16 inch,
After forming into a cylindrical shape, it is dried in air at 120 ° C and then 500 ° C.
It was calcined in air for 3 hours to obtain a catalyst carrier.

Commercially available primary nitric acid was added to deionized water to prepare a 0.1N nitric acid aqueous solution, and 1.6 g of commercially available palladium chloride powder was added to this aqueous solution 1 and dissolved by heating to prepare a palladium solution.

20 ml of the above cylindrical catalyst carrier was immersed in 25 ml of this solution, and 0.024 g of palladium was added while slowly stirring for about 2 hours.
/ 20 ml (carrier) was supported. After washing with deionized water, it was dried in air at 120 ° C. for 12 hours and calcined in air at 500 ° C. for 3 hours.

In the same manner as above, the compositions obtained in Comparative Examples 1 and 2 were used as a carrier, and palladium was supported thereon to prepare catalysts.

(Activity test) A mixture of CO; 1%, O ₂ ; 4%, balance: N ₂ was used as a reaction gas, and the space velocity was 30000 V / H / V, the reaction tube heating furnace temperature was 250 ° C. The silica glass tube having an inner diameter of 12.7 mm (volume: 1.9 cm ³ ) was passed through a reactor filled with each catalyst shown in Table 3. After the reactor inlet concentration increased to 250 ° C. and became stable, the reactor outlet gas was analyzed by gas chromatography. The catalyst used was 500 ° C / 3 hours calcined product, 1
It is a product baked at 000 ° C / 100 hours and a product baked at 1200 ° C / 100 hours. The results of measuring the CO conversion are shown in Table 3 below.

As shown in Table 3, the catalyst using the carrier of the present invention has a reaction activity which is not significantly different from that of Comparative Examples 1 and 2 in the low temperature treatment of 500 ° C. for 3 hours. It can be seen that the high CO conversion rate is still exhibited even after the high temperature treatment of calcination.

An accelerated durability test is also conducted to check the durability of the catalyst.
The test was performed on the products baked at 1000 ° C and 1200 ° C. In the accelerated durability test, the catalyst was placed in an electric furnace, heated to 1000 ° C., and steam was injected into the furnace at a water / air mole fraction of 0.0029.
After holding for 200 to 500 hours, the specific surface area of the catalyst (ml /
g) is measured. As the composition according to the present invention, the catalyst of Example 1 and the catalysts of Comparative Examples 1 and 2 were used as carriers. The results are shown in Table 4 below. Further, the composition of the present invention showed almost no change in pore distribution. This also shows that it withstands long-term operation under high humidity conditions.

[Effect of the Invention] The present invention is composed of silica and alumina, and the content of silica is in the range of 2% by weight to 30% by weight. In the nuclear magnetic resonance measurement ( ²⁹ Si-NMR measurement), the silicone rubber (- twenty one.
9ppm) as a reference peak, the peak area of −50 to −80ppm is 0 to 25% with respect to the peak area of −50 to −130ppm,
The present invention also provides a heat-resistant inorganic porous composition having a peak area of −110 to −130 ppm of 0 to 10% with respect to a peak area of −50 to −130 ppm, and the heat resistant inorganic porous composition. And a catalyst carrier comprising Further, the heat-resistant inorganic porous composition of the present invention has a high specific surface area and high durability even under high temperature and high humidity, and when used as a catalyst carrier, it can be used not only under low temperature conditions but also under high temperature conditions. It is possible to reduce the deactivation of and retain high reaction activity.

[Brief description of drawings]

FIG. 1 shows a nuclear magnetic resonance measurement of the heat-resistant inorganic porous composition of the present invention with silicon rubber (-21.9 ppm) as a reference peak (
²⁹ Si-NMR measurement), FIG. 2 shows the heat-resistant inorganic porous composition prepared in Comparative Example 1 as silicone rubber (-21.9
(ppm) as a reference peak showing the results of nuclear magnetic resonance measurement ( ²⁹ Si-NMR measurement), and FIG. 3 shows the heat-resistant inorganic porous composition prepared in Comparative Example 2 based on silicon rubber (-21.9 ppm). shows a nuclear magnetic resonance measurement ⁽²⁹ Si-NMR measurement) result of the peak, Figure 4 is a diagram for explaining a nuclear magnetic resonance measurement of the heat-resistant inorganic porous composition ⁽²⁹ Si-NMR measurement) results is there.

(72) Inventor Masaaki Tsunono 1-3-1 Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Prefecture Toa Fuel Industry Co., Ltd. Research Institute (72) Masakichi Shimada 1 Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Prefecture 3-3-1 Toa Fuel Industry Co., Ltd.

Claims (2)

(57) [Claims] 1. Silica and alumina, wherein the content of silica is in the range of 2% by weight to 30% by weight, and in the nuclear magnetic resonance measurement ( ²⁹ Si-NMR measurement), silicon rubber (-21.
9ppm) as a reference peak, the peak area of −50 to −80ppm is 0 to 25% with respect to the peak area of −50 to −130ppm,
A heat-resistant inorganic porous composition having a peak area of −110 to −130 ppm of 0 to 10% with respect to a peak area of −50 to −130 ppm. 2. Silica and alumina, wherein the content of silica is in the range of 2% by weight to 30% by weight, and in the nuclear magnetic resonance measurement ( ²⁹ Si-NMR measurement), silicon rubber (-21.
9ppm) as a reference peak, the peak area of −50 to −80ppm is 0 to 25% with respect to the peak area of −50 to −130ppm,
A catalyst carrier comprising a heat-resistant inorganic porous composition having a peak area of −110 to −130 ppm of 0 to 10% with respect to a peak area of −50 to −130 ppm.