CN1303737A - Preparation process for composite metal oxide and composite metal catalyst - Google Patents

Abstract

The invention discloses a method for preparing composite metal oxides. A solution is prepared by mixing substituted aluminum and titanium alkoxides or titanium alkoxides in which at least one or more alkoxy groups are substituted by chelating agents into an organic solvent. Then, the above components are hydrolyzed, dried and fired. Since the hydrolysis rates of substituted aluminum alcoholate and titanium salt or titanium alcoholate are basically the same, the generation of free Al ₂ O ₃ can be suppressed. Therefore, the resulting composite metal oxide has a high specific surface area with a completely uniform composition. The invention also discloses an improved variation of the preparation method, three methods for preparing the composite metal catalyst, and various steps of the preparation method.

Description

Preparation method of composite metal oxide and preparation method of composite metal catalyst

The present invention relates to a method for preparing a composite metal oxide or the like usable as a carrier for an automobile exhaust gas purification catalyst; and a method for preparing a composite metal catalyst wherein the obtained composite metal oxide is, for example, incorporated into a carrier.

Alumina (Al ₂ O ₃ ) having a high specific surface area and high activity is often used as a carrier of an automobile exhaust gas purification catalyst. Recently, there has been a technical issue that nitrogen oxides (NO _x ) in exhaust gas should be purified in an oxygen-excess lean atmosphere. Therefore, as disclosed in Japanese Unexamined Patent Publication (KOKAI) 5-317652 and the like, a catalyst has been developed in which _{a NOx} storage element selected from alkali metals and alkaline _earth made on the carrier. According to this catalyst, _NOx is adsorbed on the _NOx storage element in a lean atmosphere. At the stoichiometric point or in a fuel-rich atmosphere, the adsorbed NO _x is released to react with reducing gases such as HC, thereby being purified. Therefore, even under a lean atmosphere, _NOx emission can be suppressed and high _NOx purification performance can be achieved.

But for catalysts in which alkaline earth metals such as barium (Ba) and platinum (Pt) are supported on activated alumina supports, there are the following drawbacks. That is, alkaline earth metals and alumina react at about 800°C, which reduces NO _x storage due to the formation of crystalline aluminates. In addition, the catalyst has insufficient heat resistance as a result.

Accordingly, Japanese Unexamined Patent Publication (KOKAI) 8-057312 discloses a catalyst comprising an amorphous aluminate serving as a support and a noble metal supported on the amorphous aluminate. The amorphous aluminate is composed of a composite metal oxide including a _NOx storage element at least one selected from alkali metals and alkaline earth metals; and aluminum. By making the support from such a composite metal oxide, the formation of crystalline aluminate at high temperature can be suppressed. Therefore, the catalyst is improved in heat resistance.

At the same time, the exhaust gas contains SO ₂ produced from the sulfur contained in the fuel, and it reacts with oxygen in the lean atmosphere on the noble metals to convert it into SO _x , such as SO ₃ . The resulting SO _x is easily converted to sulfuric acid by the water vapor in the tail gas. SO _x and sulfuric acid react with alkaline NO _x storage elements to form sulfite and sulfate. Sulfites and sulfates have been found to reduce the effect of _NOx storage elements. This phenomenon is called "sulfur poisoning". Furthermore, the problem _of exacerbated sulfur poisoning arises because porous supports such as _Al2O3 tend to adsorb _SOx .

However, since TiO ₂ does not adsorb SO ₂ , the inventors of the present invention thought of using a TiO ₂ carrier and conducted experiments. The result is as follows. Sulfur poisoning is less since the _SO2 does not adsorb on the _TiO2 and actually flows downstream, and only the _SO2 that comes into direct contact with the precious metal is oxidized. However, the initial NO _x purification activity of the catalyst using _TiO2 support is low, so it is not suitable for use as a catalyst for automobile exhaust purification.

Therefore, Japanese Unexamined Patent Publication (KOKAI) 8-099034 proposes a composite metal catalyst using a support made of a composite metal oxide such as TiO ₂ -Al ₂ O ₃ , and wherein NO _x storage elements and Noble metals are supported on the carrier. According to this catalyst, sulfur poisoning of _NOx storage elements can be suppressed, and high _NOx purification performance can be secured even after the catalyst is subjected to a durability test.

As a method for producing such a composite metal oxide, for example, a production method is known from Japanese Examined Patent Publication (KOKOKU) 2-033644. This preparation method is characterized in that two or more oxygen-containing organometallic compounds are mixed into a solvent containing polar compounds with polydentate ligands or cross-linking coordination capabilities; they are converted into condensate by hydrolysis glue; the resulting gel is then dried and fired. According to this preparation method, relatively homogeneous composite metal oxides can be easily prepared. In this way, a composite metal catalyst can be produced by supporting a noble metal such as platinum on a support composed of a composite metal oxide.

Japanese Examined Patent Publication (KOKOKU) 2-033644 cites metal alcoholates as oxygen-containing organometallic compounds. Therefore, if the aforementioned preparation method is used to prepare the Al-Ti composite oxide, aluminum alkoxide and titanium alkoxide may be considered.

But aluminum alcoholate and titanium alcoholate have different hydrolysis reaction rates. Therefore, as described later, it is difficult to produce an Al-Ti composite oxide having a homogeneous composition by the production method disclosed in Japanese Examined Patent Publication (KOKOKU) 2-033644.

Therefore, if the catalyst uses an Al-Ti composite oxide prepared by the preparation method disclosed in Japanese Examined Patent Publication (KOKOKU) 2-033644 as a support, TiO ₂ cannot sufficiently exert the sulfur poisoning inhibitory effect. Therefore, the catalyst cannot sufficiently suppress the decrease in the _NOx conversion rate after being subjected to the durability test.

Furthermore, according to the studies of the present inventors, the following have been revealed. If an aluminum alcoholate is used to synthesize a composite metal oxide, the resulting composite metal oxide has insufficient heat resistance and its specific surface area inevitably decreases. If such a composite metal oxide is incorporated into a carrier, and a _NOx storage element is loaded thereon or composited therewith, the resulting catalyst has the following drawbacks. That is, if the catalyst is subjected to high temperature while in use, the dispersibility of the _NOx storage element decreases, causing crystallization of the _NOx storage element. As a result, the _NOx purification performance of the catalyst deteriorates.

Therefore, as described above, if an aluminum alcoholate is used to synthesize a composite metal oxide, the resulting composite metal oxide has insufficient heat resistance and its specific surface area inevitably decreases. Therefore, if the composite metal oxide obtained by the preparation method disclosed in the aforementioned patent is incorporated into a carrier, and _NOx storage elements and noble metals are supported on the carrier to constitute a catalyst, the resulting catalyst has the following drawbacks. That is, if the catalyst is subjected to high temperature while in use, the dispersibility of the _NOx storage element and the noble metal decreases, causing the noble metal to gradually form particles and the _NOx storage element to crystallize. As a result, the three-way catalytic activity and _NOx purification performance of the catalyst deteriorated.

In addition, if a composite metal oxide, such as TiO ₂ -Al ₂ O ₃ disclosed in Japanese Unexamined Patent Publication (KOKAI) 8-099034, is incorporated into a carrier, and a noble metal is supported on the carrier to make a catalyst, the noble metal The particle growth effect in the high-temperature durability test is not low because the support does not have a sufficiently uniform composition. Therefore, the three-way catalytic activity of the resulting catalyst is insufficient.

The present invention has been developed in light of the foregoing circumstances. Accordingly, an object of the present invention is to easily and stably prepare a catalyst in which an Al-Ti composite oxide having a sufficiently uniform composition is made into a support. Another object of the present invention is to make the catalyst have high heat resistance and high purification performance even after being subjected to a high-temperature durability test.

The method for preparing composite metal oxides proposed in claim 1 solves the foregoing technical problems, and is characterized in that it comprises the following steps:

A solution is prepared, wherein at least one of a substituted aluminum alcoholate and a titanium salt and a titanium alcoholate is mixed into an organic solvent, wherein the substituted aluminum alcoholate is an aluminum alcoholate in which at least one or more alkoxy groups are substituted by a chelating agent ;Then

The components of the solution are dried and fired after hydrolysis.

The method for preparing composite metal oxides proposed in claim 2 further embodies the method for preparing composite metal oxides proposed in claim 1, which is characterized in that it comprises the following steps:

A solution is prepared, wherein substituted aluminum propoxide and titanium tetraisopropoxide are mixed into an organic solvent, wherein the substituted aluminum propoxide is a triisopropoxide in which at least one or more isopropoxy groups are replaced by ethyl acetoacetate. aluminum propoxide; then

These alkoxides are dried and fired after hydrolysis.

The method for preparing the composite metal catalyst proposed in claim 3 solves the foregoing technical problems, and is characterized in that it comprises the following steps:

A solution is prepared, wherein at least one of a substituted aluminum alcoholate and a titanium salt and a titanium alcoholate is mixed into an organic solvent, wherein the substituted aluminum alcoholate is an aluminum alcoholate in which at least one or more alkoxy groups are substituted by a chelating agent ;

The components of the solution are dried and fired after hydrolysis, which forms the support; then

At least a noble metal is supported on the carrier.

The method for preparing the composite metal catalyst proposed in claim 4 further embodies the preparation method of the composite metal catalyst proposed in claim 3, which is characterized in that it comprises the following steps:

A solution is prepared, wherein substituted aluminum propoxide and titanium tetraisopropoxide are mixed into an organic solvent, wherein the substituted aluminum propoxide is a triisopropoxide in which at least one or more isopropoxy groups are replaced by ethyl acetoacetate. aluminum propoxide;

These alcoholates are dried and fired after hydrolysis, which forms the support; then

At least a noble metal is supported on the carrier.

The composite metal catalyst preparation method proposed in claim 5 is characterized in that it comprises the following steps:

mixing a substituted aluminum alcoholate and a soluble compound into an organic solvent, wherein the substituted aluminum alcoholate is an aluminum alcoholate whose at least one or more alkoxy groups are substituted by a chelating agent, and the soluble compound is soluble in the organic solvent, and comprising a catalyst metal element composed of at least one of a _NOx storage element and a noble metal, the _NOx storage element being at least one selected from an alkali metal, an alkaline earth metal, and a rare earth element; and then

After hydrolysis of at least the substituted aluminum alcoholate, the components of the mixture are dried and fired.

The preparation method of the composite metal catalyst proposed in claim 6 is characterized in that, in the preparation method of the composite metal catalyst proposed in claim 5, the chelating agent is ethyl acetoacetate.

According to the preparation method of the composite metal oxide of the present invention, the composite metal oxide with uniform composition and good heat resistance can be guaranteed to be prepared.

According to the preparation method of the composite metal oxide of the present invention, a catalyst with a high specific surface area can be easily and stably prepared, wherein the dispersibility of NO _x storage elements and precious metals is improved, and the heat resistance and sulfur poisoning resistance of the catalyst good.

A more complete understanding of the invention and its many advantages, and better understanding thereof, may be obtained by reference to the following detailed description in conjunction with the accompanying drawings and detailed description, all of which are a part of this invention:

Fig. 1 is a schematic diagram for explaining the steps in one example of the production method according to the present invention.

Fig. 2 is a histogram for illustrating the specific surface area of Al-Ti composite oxides obtained in Examples 1-10 and Comparative Examples 1-4.

3 is an X-ray diffraction diagram for illustrating X-ray diffraction patterns of Al-Ti composite oxides obtained in Examples 1, 3, 5 and 7 and Comparative Examples 1 and 3. FIG.

4 is an X-ray diffraction diagram for illustrating X-ray diffraction patterns of Al-Ti composite oxides obtained in Examples 2, 4, 6 and 8 and Comparative Examples 2 and 4.

Having generally described the invention, a further understanding can be obtained by reference to specific preferred embodiments which are provided for illustration only and therefore should not be used to limit the scope of the appended claims.

The inventors of the present invention used the preparation method disclosed in Japanese Examined Patent Publication (KOKOKU) 2-033644 to prepare an Al-Ti composite oxide through research. However, if this preparation method is used to prepare an Al-Ti composite oxide, the following phenomenon occurs. That is, when the obtained Al-Ti composite oxide is fired at about 900°C, its specific surface area decreases. Firing produces α-Al ₂ O ₃ . Regarding these phenomena, it was found that free Al ₂ O ₃ , which does not constitute the composite oxide, remained in the resulting Al-Ti composite oxide in a large amount. That is, free Al ₂ O ₃ is converted into α-Al ₂ O ₃ at high temperature, so the specific surface area of the Al-Ti composite oxide decreases. Therefore, if an Al-Ti composite oxide is used in the catalyst, there occurs a drawback that the activity of the resulting catalyst is lowered.

The reason for this unfavorable phenomenon was further investigated. As a result, it is considered that free Al ₂ O ₃ which is not complexed with TiO ₂ is formed because the hydrolysis rate of aluminum alcoholate is higher than that of titanium alcoholate. That is, when aluminum alcoholate and titanium alcoholate are hydrolyzed in a coexistent state, aluminum alcoholate is hydrolyzed faster than titanium alcoholate. Therefore, after firing the resulting Al-Ti composite oxide, Al ₂ O ₃ that does not participate in the composite remains in the Al-Ti composite oxide.

Therefore, the preparation method of the present invention adopts a substituted aluminum alcoholate as one of the precursors of the composite metal oxide, which is an aluminum alcoholate whose at least one or more alkoxy groups are substituted by a chelating agent.

Such substituted aluminum alcoholates are characterized by a rate of hydrolysis that is lower than that of aluminum alcoholates. Thus, the rate of hydrolysis of such substituted aluminum alcoholates is equal to, for example, the rate of hydrolysis of titanium alcoholates. Therefore, Al ₂ O ₃ and TiO ₂ are convenient for compounding. Furthermore, it is considered that by using such a substituted aluminum alcoholate, composite metal elements such as Al and Ti can be bonded together via a chelating agent. In addition, since the substituted aluminum alcoholate exists stably in the organic solvent, the defect that the aluminum alcoholate with a higher hydrolysis rate is separated due to the dissociation of the chelating agent does not occur.

In addition, if substituted aluminum propoxide (which is an aluminum triisopropoxide whose one or more isopropyl groups are replaced by ethyl acetoacetate) and titanium tetraisopropoxide, then the substituted aluminum propoxide and tetraisopropoxide The hydrolysis rates of titanium propoxide are then very close to each other. Therefore, free Al ₂ O ₃ which does not constitute the composite oxide can be further suppressed from remaining in the obtained Al-Ti composite oxide. Therefore, an Al-Ti composite oxide having a high specific surface area and a uniform composition can be obtained.

In addition, since the substituted aluminum propoxide whose isopropoxy group is replaced by ethyl acetoacetate is soluble in 2-propanol at room temperature, there arises such an advantage that the yield of Al-Ti composite oxide is increased to no 2 times when using this substitute for aluminum propoxide.

In addition, if a soluble compound (soluble in an organic solvent and containing a catalyst metal element composed of at least one of a _NOx storage element and a noble metal) and a substituted aluminum alcoholate is mixed into an organic solvent, and at least the subsequent hydrolysis of this substituted alcoholate aluminum, then the substituted aluminum alcoholate is characterized in that its rate of hydrolysis is lower than that of the aluminum alcoholate. Therefore, this substituted aluminum alcoholate facilitates complexation with soluble compounds compared to the case of using aluminum alcoholate.

For these reasons, free _Al2O3 which is not complexed remains in the resulting Al-Ti composite oxide, and in the composite _formed , aluminum and the catalyst metal element are uniformly composited. Therefore, the resulting composite metal oxide has a high specific surface area and a uniform composition. Thus, the dispersibility of the _NOx storage element and the noble metal is improved, and the heat resistance thereof is also improved.

As for the aluminum alcoholate used as _{the Al2O3} source, an alcoholate whose alkoxy group has 1 to 5 carbon atoms is preferable for reasons such as easiness of drying. For example, aluminum methoxide, aluminum ethoxide, aluminum propoxide, aluminum isopropoxide, aluminum butoxide and aluminum isobutoxide can be used.

In the preparation method of the present invention, such a substituted aluminum alcoholate is used, wherein at least one alkoxy group of the aforementioned substituted aluminum alcoholate is replaced by a chelating agent. If all the alkoxy groups of the aluminum alcoholate are substituted by a chelating agent, the specific surface area of the resulting composite metal oxide will decrease. Therefore, substituted aluminum alkoxides are used in which one or both alkoxy groups are replaced by chelating agents. Among the substituted aluminum alcoholates, those in which two alkoxy groups are replaced by chelating agents are preferred because the hydrolysis rate thereof can be further reduced.

As the chelating agent, dimethylglyoxime, dithizone, ethyl acetoacetate, acetylacetone, glycine, EDTA and NTA can be used. The rate of hydrolysis is optimal if ethyl acetoacetate is used as the chelating agent. Therefore, the specific surface area of the resulting composite metal oxide is especially increased.

Regarding the titanium salt used as the _TiO2 source, a titanium salt soluble in an organic solvent is used. For example, titanium nitrate, titanium chloride, titanium acetate, ammonium titanate and titanium complexes can be used.

Regarding the titanium alcoholate used as a source of TiO ₂ , an alcoholate whose alkoxy group has 1 to 5 carbon atoms is preferred because of easiness of drying and the like. For example, titanium methoxide, titanium ethoxide, titanium propoxide, titanium isopropoxide, titanium butoxide, and titanium isobutoxide can be used.

The mixing ratio of the Al ₂ O ₃ source and the TiO ₂ source is determined according to the composition of the target Al—Ti composite oxide. If the Al-Ti composite oxide is used as the carrier of the exhaust gas purification catalyst, it is preferable to mix the source of Al ₂ O ₃ with the source of TiO ₂ so that the ratio of Al ₂ O ₃ /TiO ₂ is 1/30 to 30/1 (that is, Al ₂ O ₃ /TiO ₂ =1/30-30/1).

As for the catalyst metal element, at least one of _NOx storage elements (at least one selected from alkali metals, alkaline earth metals and rare earth elements) and noble metals may be selected. As the alkali metal, lithium, sodium, potassium and cesium can be cited. Alkaline earth metals are elements of Group 2A of the periodic table, and examples thereof include magnesium, calcium, strontium, and barium. As for rare earth elements, scandium, yttrium, lanthanum, cerium, praseodymium, and neodymium can be exemplified. As for noble metals, platinum (Pt), rhodium (Rh), palladium (Pd) and iridium (Ir) can be exemplified.

For example, if the NO _x storage element is selected as the catalyst metal element, the catalyst can be prepared by loading the noble metal on the formed composite metal oxide by the impregnation loading method or the adsorption loading method. In addition, if a noble metal is selected as the catalyst metal element, the _NOx storage element can be supported on the formed composite metal oxide by the impregnation loading method to make a catalyst. In addition, if both _NOx storage elements and noble metal elements are selected as catalyst metal elements, this scheme is especially preferable because a catalyst in which both _NOx storage elements and noble metal elements are uniformly dispersed can be produced and a subsequent loading step can be avoided. .

The _NOx storage element is preferably compounded with or supported on the composite metal oxide in an amount of 2-50 mol% relative to alumina (made of substituted aluminum alcoholate). If the amount thereof is below this range, the _NOx purification performance deteriorates due to insufficient _NOx storage activity. If the amount thereof exceeds this range, the effect of the _NOx storage element is saturated, and then the _NOx storage element easily reacts with alumina, resulting in a decrease in heat resistance.

The noble metal is preferably compounded with or supported on the composite metal oxide in an amount of 0.1 to 20% by weight relative to alumina (made of substituted aluminum alcoholate). If the amount thereof is below this range, the purification performance is low. If the noble metal is supported beyond this range, the effect of the noble metal will be saturated, and the cost of the resulting catalyst will increase.

Note that in addition to aluminum, metals such as titanium, zirconium, and silicon may be used. In this case, metals such as titanium, zirconium and silicon can be mixed as oxide powders or supplied as alcoholates so that it can be complexed with aluminum and catalyst metal elements. In addition, it is preferable to mix or compound an oxygen storage-release oxygen element such as ceria and ceria-zirconia. Sulfur poisoning of NO _x storage elements can be further suppressed by further compounding with titanium.

The soluble compound (containing the catalyst metal element and soluble in an organic solvent) may be a compound soluble in the organic solvent used. Organometallic compounds such as alcoholates, metal nitrates, metal acetates, metal ammines and metal chlorides may be used.

As for the organic solvent, a solvent capable of dissolving the substituted aluminum alcoholate, titanium salt and titanium alcoholate, or a soluble compound can be used. Methanol, ethanol, 1-propanol, 2-propanol, butanol, isobutanol, sec-butanol and tert-butanol can be used.

In order to hydrolyze the alcoholate in the solution, moisture contained in the air may be used, but it is preferable to add water to the solution while stirring the solution at a predetermined temperature. Since the reaction proceeds rapidly, the specific surface area of the composite metal oxide obtained can be further increased.

Regarding the amount of water added, if the added amount is too low, the hydrolysis time will be longer. If the added amount is too high, it will be difficult to hydrolyze uniformly, resulting in uneven composition of the obtained composite metal oxide. Therefore, the water is preferably added in a molar ratio of 0.5-20, especially 1-10, relative to the alcoholate used.

In order to further accelerate the hydrolysis reaction, it is preferable to add a hydrolysis accelerator including basic substances such as ammonium, ammonium carbonate and amines; or acids such as formic acid, oxalic acid and tartaric acid to the solution.

The heating temperature in the hydrolysis step is preferably 35-150°C. If it is lower than 35°C, the reaction hydrolysis is longer due to the lower reaction rate. If the reaction time is too short, a large amount of free Al ₂ O ₃ without complexing remains. If the heating temperature exceeds 150°C, the alcoholate will decompose. It is especially desirable that the heating temperature is 40-100°C.

After hydrolysis, the precipitate is dried to remove the solvent and the like, followed by firing, whereby a composite metal oxide can be obtained. According to need, one of a _NOx storage element and a noble metal can be supported on the composite metal oxide, whereby a composite metal catalyst can be obtained. Drying conditions are not particularly limited. The firing temperature is preferably 500-1200°C. If the firing temperature is lower than 500°C, it is difficult to form a stable composite metal catalyst. If the firing temperature exceeds 1200°C, the specific surface area of the resulting composite metal catalyst will decrease.

The present invention is described in detail below by way of examples and comparative examples.

Example 1

As shown in Fig. 1, an Al-Ti composite oxide was prepared.

First, 154.6 g of aluminum ethyl acetoacetate diisopropoxide (Al- _EAA ), a substituted aluminum alcoholate, as a source of _Al2O3 , and 40.1 g of _titanium tetraisopropoxide (Ti( OiC ₃ H ₇ ) ₄ ) was added into 423.4 g of 2-propanol, followed by stirring at 82° C. for 2 hours to dissolve ( FIG. 1(A )).

Then, the resulting solution was kept at reflux at 82°C. While stirring the solution, 121.9 g of ion-exchanged water was added dropwise to the solution to hydrolyze the alcoholate. In addition, the solution was stirred at 82° C. under reflux for 4 hours, so that aging was carried out ( FIG. 1(B )).

Then, the solution was vacuum-dried to remove the solvent, and the resulting precipitate was dried at 120 °C for an additional 12 hours (Fig. 1(C)).

Then, the precipitate was calcined at 480°C for 4 hours and then fired at 800°C in air for 5 hours (FIG. 1(D)), which gave the Al-Ti composite oxide of this example.

The specific surface area of the resulting Al-Ti composite oxide was determined by the BET method, and the results are shown in FIG. 2 . Furthermore, this Al-Ti composite oxide was subjected to X-ray diffraction analysis, and the resulting X-ray diffraction pattern is shown in FIG. 3 .

Example 2

The Al-Ti composite oxide of Example 2 was obtained in the same manner as in Example 1, except that the firing temperature was set at 900°C instead of 800°C. The specific surface area was measured in the same manner as in Example 1, and the results are shown in FIG. 2 . In addition, the X-ray diffraction pattern is given in FIG. 4 .

Example 3

The Al-Ti composite oxide of Example 3 was obtained in the same manner as in Example 1, except that the heating temperature in the dissolution step, hydrolysis step and aging step was set at 35°C instead of 82°C. The specific surface area was measured in the same manner as in Example 1, and the results are shown in FIG. 2 . Furthermore, the X-ray diffraction pattern is given in FIG. 3 .

Example 4

The Al-Ti composite oxide of Example 4 was obtained in the same manner as in Example 3, except that the firing temperature was set at 900°C instead of 800°C. The specific surface area was measured in the same manner as in Example 1, and the results are shown in FIG. 2 . In addition, the X-ray diffraction pattern is given in FIG. 4 .

Example 5

The Al-Ti composite oxide of Example 5 was obtained in the same manner as in Example 1, except that the heating temperature in the dissolution step, hydrolysis step and aging step was set at 50°C instead of 82°C. The specific surface area was measured in the same manner as in Example 1, and the results are shown in FIG. 2 . Furthermore, the X-ray diffraction pattern is given in FIG. 3 .

Example 6

The Al-Ti composite oxide of Example 6 was obtained in the same manner as in Example 5, except that the firing temperature was set at 900°C instead of 800°C. The specific surface area was measured in the same manner as in Example 1, and the results are shown in FIG. 2 . In addition, the X-ray diffraction pattern is given in FIG. 4 .

Example 7

The Al-Ti composite oxide of Example 7 was obtained in the same manner as in Example 1, except that the heating temperature in the dissolution step, hydrolysis step and aging step was set at 65°C instead of 82°C. The specific surface area was measured in the same manner as in Example 1, and the results are shown in FIG. 2 . Furthermore, the X-ray diffraction pattern is given in FIG. 3 .

Example 8

The Al-Ti composite oxide of Example 8 was obtained in the same manner as in Example 7, except that the firing temperature was set at 900°C instead of 800°C. The specific surface area was measured in the same manner as in Example 1, and the results are shown in FIG. 2 . In addition, the X-ray diffraction pattern is given in FIG. 4 .

Example 9

The Al-Ti composite oxide of Example 9 was obtained in the same manner as in Example 1, except that 26.7 g of TiCl ₄ was used as the TiO ₂ source instead of 40.1 g of titanium tetraisopropoxide (Ti(OiC ₃ H ₇ ) ₄ ). The specific surface area was measured in the same manner as in Example 1, and the results are shown in FIG. 2 .

Example 10

The Al-Ti composite oxide of Example 10 was obtained in the same manner as in Example 9, except that the firing temperature was set at 900°C instead of 800°C. The specific surface area was measured in the same manner as in Example 1, and the results are shown in FIG. 2 .

Comparative example 1

115.1 g of aluminum triisopropoxide (Al(OiC ₃ H ₇ ) ₃ ) as the source of Al ₂ O ₃ , and 40.1 g of titanium tetraisopropoxide (Ti(OiC ₃ H ₇ ) ₄ ) as the source of TiO ₂ were added 423.4 g of 2-propanol, and then stirred at 82°C for 2 hours to dissolve.

Then, the resulting solution was kept at 82°C. While stirring the solution, 28.2 g of 2,4-pentanedione (acetylacetone) was added dropwise to the solution. The solution was stirred for an additional 2 hours at 82°C. Then, the solution was kept at 82°C. While stirring the solution, 121.9 g of ion-exchanged water was added dropwise to the solution to hydrolyze the alcoholate. The solution was additionally stirred at 82° C. for 4 hours, whereby aging was carried out.

Then, the solution was vacuum dried to remove the solvent, and the resulting precipitate was dried at 120 °C for an additional 12 h. Then, the precipitate was calcined at 480° C. for 4 hours, and then fired at 800° C. in air for 5 hours to obtain the Al—Ti composite oxide of the comparative example. Then, the specific surface area was measured in the same manner as in Example 1, and the results are shown in FIG. 2 . Furthermore, the X-ray diffraction pattern is given in FIG. 3 .

Comparative example 2

The Al-Ti composite oxide of Comparative Example 2 was obtained in the same manner as Comparative Example 1, except that the firing temperature was set at 900°C instead of 800°C. The specific surface area was measured in the same manner as in Example 1, and the results are shown in FIG. 2 . In addition, the X-ray diffraction pattern is given in FIG. 4 .

Comparative example 3

The Al-Ti composite oxide of Comparative Example 3 was obtained in the same manner as Comparative Example 1, except that 36.7 g of ethyl acetoacetate was added dropwise instead of 28.2 g of 2,4-pentanedione (acetylacetone). The specific surface area was measured in the same manner as in Example 1, and the results are shown in FIG. 2 . Furthermore, the X-ray diffraction pattern is given in FIG. 3 .

Comparative example 4

The Al-Ti composite oxide of Comparative Example 4 was obtained in the same manner as Comparative Example 3, except that the firing temperature was set at 900°C instead of 800°C. The specific surface area was measured in the same manner as in Example 1, and the results are shown in FIG. 2 . In addition, the X-ray diffraction pattern is given in FIG. 4 .

Evaluate

Table 1 summarizes the kinds of chelating agents used in the preparation of the Al-Ti composite oxides of Examples and Comparative Examples, the heating temperatures of the dissolution step, the hydrolysis step and the aging step, and the firing temperature.

Table 1 Example comparative example 1 2 3 4 5 6 7 8 9 10 1 2 3 4 Al ₂ O ₃ source Aluminum Ethyl Acetoacetate Diisopropoxide (Al-EAA) Al(OiC ₃ H ₇ ) _{3 TiO2} source Titanium tetraisopropoxide (Ti(OiC ₃ H ₇ ) ₄ ) TiCl ₄ Ti(OiC ₃ H ₇ ) ₄ Chelating agent ethyl acetoacetate Acetylacetone ethyl acetoacetate Heating temperature (℃) 82 82 35 35 50 50 65 65 82 82 - - - - Firing temperature (℃) 800 900 800 900 800 900 800 900 800 900 800 900 800 900

According to Figure 2, Example 3 exhibits the smallest specific surface area among the examples if fired at 800°C. However, it should be understood that the specific surface area of the Al-Ti composite oxide of Example 3 is comparable to that of Comparative Example 1 and Comparative Example 3, and the specific surface area of the Al-Ti composite oxide of other examples is larger than that of Comparative Example 1 and Comparative Example 3. The ratio of 3 is higher. If fired at 900°C, it should be understood that the specific surface area of the Al-Ti composite oxides of these Examples (except Example 4) is higher than that of the Comparative Example.

Therefore, the following is evident. That is, if the firing temperature is 800°C, and if the heating temperature is set at 35°C or higher; in addition, if the firing temperature is 900°C, and if the heating temperature is set at 50°C or higher; then the present invention prepares The specific surface area of the Al-Ti composite oxide prepared by the method is equal to or higher than that of the Al-Ti composite oxide prepared by the conventional preparation method.

In Fig. 4, the α-Al ₂ O ₃ peak was observed in all Al-Ti composite oxides. Since α-Al ₂ O ₃ is generated when ordinary alumina is heated, the presence of α-Al ₂ O ₃ proves that there is free alumina that has not been converted into Al-Ti composite oxide. But in these examples, the peak intensity _{of Al2O3} decreases with increasing heating temperature. For example, the peak intensity of Example 6 is equivalent to that of Comparative Example 2 and Comparative Example 4. Therefore, Example 6 corresponds to Comparative Examples 2 and 4 in terms of the homogeneity of the Al-Ti composite oxide. The heating temperatures of Example 8 and Example 2 are 65°C and 82°C, so Example 8 and Example 2 show higher homogeneity than Comparative Examples 2 and 4.

That is, if the heating temperature is set at 50°C or higher, and if the firing temperature is set at 900°C, Al-Ti equivalent to or higher in homogeneity than the comparative example using the conventional preparation method can be produced. composite oxides. This is consistent with the results _in Fig. 2, and there is clearly a close correlation between the specific surface area and the α- _Al2O3 content. In addition, compared with conventional preparation methods, the preparation method of the present invention can obviously ensure the preparation of Al-Ti composite oxides with a higher uniform composition.

Also in Fig. 3, no α-Al ₂ O ₃ peak was observed in all Al-Ti composite oxides. Therefore, if the firing temperature is up to 800°C and the heating temperature is set at 35°C, it is obvious that an Al-Ti composite oxide with a homogeneity comparable to that of the comparative example can be prepared.

That is, if the Al-Ti composite oxide made by the preparation method of the present invention is made into a carrier, and if the carrier is loaded with noble metal elements or _NOx storage elements to prepare a composite metal catalyst, then this composite metal catalyst is due to its It has high activity due to its high specific surface area, and it has good resistance to sulfur poisoning. Even when subjected to a high-temperature durability test, the support can be suppressed from decreasing in specific surface area. Therefore, particle growth of the noble metal or crystallization of the _NOx storage element due to a decrease in the specific surface area can be suppressed. Therefore, this composite metal catalyst can maintain high purification activity.

Example 11

First, 572.76 g of a solution in which ethyl acetoacetate aluminum diisopropoxide (Al-EAA) (a substituted aluminum alcoholate) as a source of Al ₂ O ₃ was dissolved in 2-propanol in an amount of 75% by weight ), and 26.7 g of barium diisopropoxide (Ba(OiC ₃ H ₇ ) ₂ ) were mixed into 877.8 g of 2-propanol, and then stirred at 82° C. for 2 hours to dissolve.

Then, the resulting solution was kept at reflux at 82°C. While stirring the solution, 268.5 g of ion-exchanged water was added dropwise to the solution to hydrolyze the alcoholate. Furthermore, this solution was aged by refluxing at 82 degreeC for 5 hours.

Then, the solution was vacuum dried to remove the solvent, and the resulting precipitate was dried at 120 °C for an additional 12 h. Then, the precipitate was calcined at 480° C. for 4 hours, and then fired at 1100° C. in air for 5 hours to obtain a composite metal oxide. The specific surface area of the obtained composite metal oxide was measured by the one-point BET method, and the results are shown in Table 2.

An aqueous dinitrodiammine platinum solution of a predetermined concentration is impregnated in a predetermined amount into the obtained composite metal oxide. The composite metal oxide was dried at 120° C. for 1 hour, and then fired at 250° C. for 1 hour to support Pt. Further, the composite metal oxide was molded into a pellet shape by an ordinary method, thus preparing the composite metal catalyst of this example. This composite metal catalyst includes a support comprising a composite metal oxide composed of alumina and barium oxide and Pt supported on the support.

The resulting spherical catalyst was placed in a stream of lean model gas containing 600 ppm _SO2 . Then, durability treatment was performed in which the spherical catalyst was heated at 700° C. for 5 hours. After the durability treatment, the maximum conversion rate of _NOx was measured when the atmosphere of the spherical catalyst changed from rich to lean. The results are given in Table 2.

Example 12

The composite metal oxide of Example 12 is prepared in the same manner as in Example 11, except that 477.2 grams of 75% ethyl acetoacetate aluminum diisopropoxide solution identical to that of Example 11, 44.5 grams of barium diisopropoxide and 796.8 grams of aluminum diisopropoxide are dissolved. gram of 2-propanol, 235.4 grams of ion-exchanged water was added dropwise in the hydrolysis step, and the firing temperature was set at 900°C.

Then, the specific surface area was measured in the same manner as in Example 11. In addition, Pt was also supported to prepare a spherical catalyst including the composite metal catalyst of Example 12. The maximum _NOx conversion of this spherical catalyst after durability treatment was similarly measured. The results are given in Table 2.

Example 13

The composite metal oxide of Example 13 was prepared in the same manner as in Example 11, except that 620.7 grams of 75% ethyl acetoacetate aluminum diisopropoxide solution identical to Example 11, 27.8 grams of potassium acetate (CH ₎ were dissolved COOK) (instead of barium diisopropoxide) and 1036.4 g of 2-propanol, 306.3 g of ion-exchanged water was added dropwise in the hydrolysis step, and the firing temperature was set at 1000°C.

Then, the specific surface area was measured in the same manner as in Example 11. In addition, Pt was also supported to prepare a spherical catalyst including the composite metal catalyst of Example 13. The maximum _NOx conversion of this spherical catalyst after durability treatment was similarly measured. The results are given in Table 2.

Example 14

The composite metal oxide of Example 14 was prepared in the same manner as in Example 11, except that 557.6 grams of 75% ethyl acetoacetate aluminum diisopropoxide solution identical to Example 11, 25.0 grams of potassium acetate (replacing di Barium isopropoxide), 36.2 grams of titanium tetraisopropoxide (Ti(OiC ₃ H ₇ ) 4) and 1007.5 grams of 2-propanol, add 302.6 grams of ion-exchanged water dropwise in the hydrolysis step, and set the firing temperature at 900°C.

Then, the specific surface area was measured in the same manner as in Example 11. In addition, Pt was also supported to prepare a spherical catalyst including the composite metal catalyst of Example 14. The maximum _NOx conversion of this spherical catalyst after durability treatment was similarly measured. The results are given in Table 2.

Example 15

The composite metal oxide of Example 15 was prepared in the same manner as in Example 11, except that 528.5 grams of 75% ethyl acetoacetate aluminum diisopropoxide solution identical to Example 11, 23.7 grams of potassium acetate (replacing di Barium isopropoxide), 54.4 grams of zirconium tetraisopropoxide (Zr(OiC ₃ H ₇ ) ₄ ) and 954.9 grams of 2-propanol, 286.8 grams of ion-exchanged water was added dropwise in the hydrolysis step, and the firing temperature was set at 900°C.

Then, the specific surface area was measured in the same manner as in Example 11. In addition, Pt was also supported to prepare a spherical catalyst including the composite metal catalyst of Example 15. The maximum _NOx conversion of this spherical catalyst after durability treatment was similarly measured. The results are given in Table 2.

Example l6

The composite metal oxide of Example 16 was prepared in the same manner as in Example 11, except that 467.4 grams of 75% ethyl acetoacetate aluminum diisopropoxide solution identical to Example 11, 73.2 grams of lanthanum acetate ((CH ₃ COO) ₃ La) (instead of barium diisopropoxide), and 467.4 g of 2-propanol, 230.6 g of ion-exchanged water was added dropwise in the hydrolysis step, and the firing temperature was set at 900°C.

Then, the specific surface area was measured in the same manner as in Example 11. In addition, Pt was also supported to prepare a spherical catalyst including the composite metal catalyst of Example 16. The maximum _NOx conversion of this spherical catalyst after durability treatment was similarly measured. The results are given in Table 2.

Example 17

The composite metal oxide of Example 17 was prepared in the same manner as in Example 11, except that 612.5 grams of the same 75% ethyl acetoacetate aluminum diisopropoxide solution and 28.8 grams of strontium diisopropoxide were dissolved. (Sr(OiC ₃ H ₇ ) ₂ ) (instead of barium diisopropoxide), and 938.9 g of 2-propanol, 287.1 g of ion-exchanged water was added dropwise in the hydrolysis step, and the firing temperature was set at 1000°C.

Then, the specific surface area was measured in the same manner as in Example 11. In addition, Pt was also supported to prepare a spherical catalyst including the composite metal catalyst of Example 17. The maximum _NOx conversion of this spherical catalyst after durability treatment was similarly measured. The results are given in Table 2.

Example 18

The composite metal oxide of Example 18 was prepared in the same manner as _in Example 11, except that 490.4 grams of 75% ethyl acetoacetate aluminum diisopropoxide solution identical to that of Example 11, 43.0 grams of cesium acetate (CH COOCs) (instead of barium diisopropoxide), and 818.9 grams of 2-propanol, 242.0 grams of ion-exchanged water was added dropwise in the hydrolysis step, and the firing temperature was set at 1000°C.

Then, the specific surface area was measured in the same manner as in Example 11. In addition, Pt was also supported to prepare a spherical catalyst including the composite metal catalyst of Example 18. The maximum _NOx conversion of this spherical catalyst after durability treatment was similarly measured. The results are given in Table 2.

Example 19

633.5 grams of 75% ethyl acetoacetate aluminum dipropoxide solution identical to Example 11, and 41.1 grams of titanium tetraisopropoxide (Ti(OiC ₃ H ₇ ) ₄ ) were mixed in 971.0 grams of 2-propanol, and then Stir at 82°C for 2 hours to effect dissolution.

Then, the above solution was kept under reflux at 82°C. While stirring the solution, 312.59 g of an aqueous dinitrodiammine platinum solution containing 1.1 g of Pt was added dropwise to the solution to hydrolyze the alcoholate. The solution was aged under reflux with stirring for an additional 5 hours at 82°C. Then, Example 19 composite metal oxide was prepared in the same manner as in Example 11, except that the firing temperature was set at 800°C. The content of Pt contained therein was 2% by weight.

Then, the specific surface area was measured in the same manner as in Example 11. Further, the composite metal oxide was molded into a pellet shape by an ordinary method, thus preparing a spherical catalyst including the composite metal catalyst of Example 19. The resulting spherical catalyst was placed in a lean-burn simulated atmosphere. Then, durability treatment was performed in which the spherical catalyst was heated at 800° C. for 5 hours. After the durability treatment, the maximum conversion rates of NO _x , HC and CO of the spherical catalysts were respectively measured in a simulated gas flow corresponding to the ideal air-fuel ratio. The results are given in Table 2.

Example 20

The composite metal oxide of Example 20 was prepared in the same manner as in Example 19, except that 559.0 grams of the same 75% aluminum diisopropoxide solution of ethyl acetoacetate and 48.0 grams of cerium tetraisopropoxide were dissolved. (Ce(OiC ₃ H ₇ ) ₄ ) (replacing titanium tetraisopropoxide) and 856.8 grams of 2-propanol, 275.8 grams of dinitrodiammine platinum aqueous solution containing 1.1 grams of Pt was added dropwise to the solution to hydrolyze alcoholate. The content of Pt contained therein was 2% by weight.

Then, the specific surface area was measured in the same manner as in Example 11. In addition, a spherical catalyst including the composite metal catalyst of Example 20 was prepared from the composite metal oxide by an ordinary method. In the same manner as in Example 19, the maximum conversion rates of _NOx , HC, and CO after the durability treatment were respectively measured. The results are given in Table 2.

Comparative example 5

320.3 g of aluminum triisopropoxide (Al(OiC ₃ H ₇ ) ₃ ), and 26.7 g of barium diisopropoxide were mixed into 941.0 g of 2-propanol, followed by stirring at 82°C for 2 hours to dissolve.

Then, the resulting solution was kept at reflux at 82°C. While stirring the solution, 68.0 g of 2,4-pentanedione was added dropwise. The solution was stirred for a further 2 hours at 82°C. Then, the solution was kept at reflux at 82°C. While stirring the solution, 268.5 g of ion-exchanged water was added dropwise to the solution to hydrolyze the alcoholate. The solution was aged under reflux with stirring for an additional 5 hours at 82°C.

Then, the solution was vacuum dried to remove the solvent, and the resulting precipitate was dried at 120°C for an additional 12 hours. Subsequently, the precipitate was calcined at 480° C. for 4 hours and fired at 1100° C. in air for 5 hours to obtain the composite metal oxide of the comparative example.

Then, the specific surface area was measured in the same manner as in Example 11. In addition, Pt was also supported to prepare spherical catalysts. The maximum _NOx conversion of this spherical catalyst after durability treatment was similarly measured. The results are given in Table 2.

Comparative example 6

The composite metal oxide of Comparative Example 6 was prepared in the same manner as Comparative Example 5, except that 266.8 grams of aluminum triisopropoxide and 44.5 grams of barium diisopropoxide were dissolved in 849.3 grams of 2-propanol, and 61.0 After adding 2,4-pentanedione, 235.4 g of ion-exchanged water was added dropwise in the hydrolysis step, and the firing temperature was set at 900°C.

Then, the specific surface area was measured in the same manner as in Example 11. In addition, Pt was also supported to prepare spherical catalysts. The maximum _NOx conversion of this spherical catalyst after durability treatment was similarly measured. The results are given in Table 2.

Comparative example 7

The composite metal oxide of Comparative Example 7 was prepared in the same manner as Comparative Example 5, except that 311.8 grams of aluminum triisopropoxide, 25.0 grams of potassium acetate (replacing barium diisopropoxide), and 36.2 grams of titanium tetraisopropoxide were dissolved. and 1069.0 g of 2-propanol, 76.4 g of 2,4-pentanedione was added dropwise, and then 302.6 g of ion-exchanged water was added dropwise in the hydrolysis step, and the firing temperature was set at 900°C.

Then, the specific surface area was measured in the same manner as in Example 11. In addition, Pt was also supported to prepare spherical catalysts. The maximum _NOx conversion of this spherical catalyst after durability treatment was similarly measured. The results are given in Table 2.

Comparative example 8

The composite metal oxide of Comparative Example 8 was prepared in the same manner as Comparative Example 5, except that 274.3 grams of aluminum triisopropoxide, 43.0 grams of cesium acetate (replacing barium diisopropoxide), and 872.9 grams of 2-propanol were dissolved , after adding 62.7 g of 2,4-pentanedione dropwise, 242.0 g of ion-exchanged water was added dropwise in the hydrolysis step, and the firing temperature was set at 1000°C.

Then, the specific surface area was measured in the same manner as in Example 11. In addition, Pt was also supported to prepare spherical catalysts. The maximum _NOx conversion of this spherical catalyst after durability treatment was similarly measured. The results are given in Table 2.

Comparative example 9

354.3 g of aluminum triisopropoxide, 41.1 g of titanium tetraisopropoxide, and 1040.8 g of 2-propanol were mixed and stirred at 82°C for 2 hours to dissolve.

Then, the resulting solution was kept at reflux at 82°C. While stirring the solution, 75.3 grams of 2,4-pentanedione were added dropwise. The solution was stirred for a further 2 hours at 82°C. Then, the solution was kept at reflux at 82°C. While stirring the solution, 312.6 g of an aqueous dinitrodiammine platinum solution containing 1.1 g of Pt was added dropwise to the solution to hydrolyze the alcoholate. The solution was aged under reflux with stirring for an additional 4 hours at 82°C. Then, in the same manner as in Example 11, the composite metal oxide of Comparative Example 9 was prepared, except that the firing temperature was set at 800°C. The content of Pt contained therein was 2% by weight.

Then, the specific surface area was measured in the same manner as in Example 11. In addition, a spherical catalyst was prepared from this composite metal oxide by a common method. The resulting spherical catalyst was placed in a lean-burn simulated gas stream. Then, durability treatment was performed in which the spherical catalyst was heated at 800° C. for 5 hours. After the durability treatment, the maximum conversion rates of NO _x , HC and CO of the spherical catalysts were respectively measured in a simulated gas flow corresponding to the ideal air-fuel ratio (stoichiometric point). The results are given in Table 2.

Comparative example 10

The composite metal oxide of Comparative Example 10 was prepared in the same manner as in Example 11, except that 312.6 grams of aluminum triisopropoxide, 48.0 grams of cerium tetraisopropoxide (replacing titanium tetraisopropoxide), and 918.4 grams of 2 - Propanol, 262.0 g of dinitrodiammine platinum aqueous solution containing 1.1 g of Pt was added dropwise to the solution to hydrolyze the alcoholate, and the firing temperature was set at 800°C. The content of Pt contained therein was 2% by weight.

Then, the specific surface area was measured in the same manner as in Example 11. In addition, a spherical catalyst was prepared from this composite metal oxide by a common method. In the same manner as in Comparative Example 9, the maximum conversion rates of NO _x , HC, and CO of the obtained spherical catalyst after the durability treatment were measured, respectively. The results are given in Table 2.

Table 2

Catalyst composition MC ^*7 (%) CMO ^*1 LE ^*2 BT ^*3 (°C) SSA ^*4 (m ² /g) DTC ^*5 EG ^*6 _NOx HC CO Example #11 Al-Ba Pt 1100 135 SO ₂ lean burn 700°C rich-lean 57 - - Example #12 Al-Ba Pt 900 144 SO ₂ lean burn 700°C rich-lean 51 - - Example #13 Al-K Pt 1000 62 SO ₂ lean burn 700°C rich-lean 61 - - Example #14 Al-K-Ti Pt 900 136 SO ₂ lean burn 700°C rich-lean 64 - - Example #15 Al-K-Zr Pt 900 127 SO ₂ lean burn 700°C rich-lean 60 - - Example #16 Al-La Pt 900 76 SO ₂ lean burn 700°C rich-lean 53 - - Example #17 Al-Sr Pt 1000 138 SO ₂ lean burn 700°C rich-lean 58 - - Example #18 Al-Cs Pt 1000 68 SO ₂ lean burn 700°C rich-lean 60 - - Example #19 Al-Ti-Pt - 800 265 Lean burn 800℃ SP ^*8 59 56 61 Example #20 Al-Ce-Pt - 800 198 Lean burn 800℃ SP ^*8 55 57 60 Comparative Example #5 Al-Ba Pt 1100 108 SO ₂ lean burn 700°C rich-lean 26 - - Comparative Example #6 Al-Ba Pt 900 125 SO ₂ lean burn 700°C rich-lean twenty four - - Comparative Example #7 Al-K-Ti Pt 900 110 SO ₂ lean burn 700°C rich-lean 43 - - Comparative Example #8 Al-Cs Pt 1000 48 SO ₂ lean burn 700°C rich-lean 42 - - Comparative Example #9 Al-Ti-Pt - 800 223 Lean burn 800℃ SP ^*8 46 44 48 Comparative Example #10 Al-Ce-Pt - 800 167 Lean burn 800℃ SP ^*8 47 42 46 Note: *1 means "compound metal oxide" *2 means "loaded element" *3 means "firing temperature"*4 means "specific surface area"*5 means "durability treatment conditions"*6 means "evaluation gas"* 7 indicates "maximum conversion" * 8 indicates "stoichiometric point".

Evaluate

By comparing Examples 11 and 12 with Comparative Examples 5 and 6, Example 14 with Comparative Example 7, and Example 18 with Comparative Example 8, the following is evident. That is, the specific surface area of the resulting composite metal oxide is increased by using substituting aluminum alcoholate as a raw material, and a catalyst having a high _NOx conversion rate even after durability treatment can be obtained by supporting Pt on this composite metal oxide. obtained from things.

Comparing Examples 19 and 20 with Comparative Examples 9 and 10, the following is evident. That is, even if Pt is compounded, a catalyst having high three-way catalytic activity even after durability treatment can be obtained by using substituted aluminum alcoholate as a raw material.

Now that the invention has been described in detail, it will be apparent to those skilled in the art that many changes and modifications can be made without departing from the spirit or scope of the invention, including the appended claims.

Claims (12)

1. A method for preparing composite metal oxides, comprising the steps of: A solution is prepared, wherein at least one of a substituted aluminum alcoholate and a titanium salt and a titanium alcoholate is mixed into an organic solvent, wherein the substituted aluminum alcoholate is an aluminum alcoholate in which at least one or more alkoxy groups are substituted by a chelating agent ;Then The components of the solution are dried and fired after hydrolysis. 2. A method for preparing composite metal oxides, comprising the steps of: A solution is prepared, wherein substituted aluminum propoxide and titanium tetraisopropoxide are mixed into an organic solvent, wherein the substituted aluminum propoxide is a triisopropoxide in which at least one or more isopropoxy groups are replaced by ethyl acetoacetate. aluminum propoxide; then These alcoholates are dried and fired after hydrolysis. 3. A method for preparing composite metal catalyst, it comprises the following steps: A solution is prepared, wherein at least one of a substituted aluminum alcoholate and a titanium salt and a titanium alcoholate is mixed into an organic solvent, wherein the substituted aluminum alcoholate is an aluminum alcoholate in which at least one or more alkoxy groups are substituted by a chelating agent ; The components of the solution are dried and fired after hydrolysis, which forms the support; then At least the noble metal is supported on the carrier. 4. A method for preparing composite metal catalyst, it comprises the following steps: A solution is prepared, wherein substituted aluminum propoxide and titanium tetraisopropoxide are mixed into an organic solvent, wherein the substituted aluminum propoxide is a triisopropoxide in which at least one or more isopropoxy groups are replaced by ethyl acetoacetate. aluminum propoxide; These alcoholates are dried and fired after hydrolysis, which forms the support; then At least the noble metal is supported on the carrier. 5. A method for preparing composite metal catalyst, it comprises the following steps: mixing a substituted aluminum alcoholate and a soluble compound into an organic solvent, wherein the substituted aluminum alcoholate is an aluminum alcoholate whose at least one or more alkoxy groups are substituted by a chelating agent, and the soluble compound is soluble in the organic solvent, and comprising a catalyst metal element composed of at least one of a _NOx storage element and a noble metal, the _NOx storage element being at least one selected from an alkali metal, an alkaline earth metal, and a rare earth element; and then After hydrolysis of at least the substituted aluminum alcoholate, the components of the mixture are dried and fired. 6. The preparation method of composite metal catalyst according to claim 5, wherein said chelating agent is ethyl acetoacetate. 7. The method for preparing composite metal oxides according to claim 1, wherein said hydrolysis is carried out at a temperature of 35-150°C. 8. The method for preparing composite metal oxides according to claim 1, wherein said hydrolysis is carried out at a temperature of 40-100°C. 9. The method for preparing composite metal oxides according to claim 2, wherein said hydrolysis is carried out at a temperature of 50-82°C. 10. The preparation method of the composite metal catalyst according to claim 3 and claim 5, wherein said hydrolysis is carried out at a temperature of 35-150°C. 11. The method for preparing a composite metal catalyst according to claim 3 and claim 5, wherein said hydrolysis is carried out at a temperature of 40-100°C. 12. The preparation method of the composite metal catalyst according to claim 4 and claim 6, wherein said hydrolysis is carried out at a temperature of 50-82°C.

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