KR102122660B1 - AMOURPHOUS CeTi-OXIDE CATALYSTS AND METHOD FOR PREPARING THE SAME - Google Patents

Abstract

The production method produced through the amorphous Ce-Ti oxide production method of the present invention is an amorphous substance in which a fine crystal structure is not formed by using anhydrous ethanol as a solvent, and thus, when used as a catalyst, may exhibit excellent catalyst efficiency.

Description

Amorphous CeTi-oxide and its manufacturing method {AMOURPHOUS CeTi-OXIDE CATALYSTS AND METHOD FOR PREPARING THE SAME}

The present invention relates to an amorphous CeTi oxide and a method for manufacturing the same, and more specifically, to a method for producing an amorphous CeTi oxide using ethanol and anhydrous, and an amorphous CeTi oxide prepared therefrom.

Cerium oxide (CeO _x , ceria) exists in a stable form in both cerium trivalent and tetravalent ions, and thus a redox (reduction-oxidation) reaction easily occurs according to changes in temperature and pressure. Therefore, the change in the number of oxygen vacancy can be seen according to the ratio of cerium trivalent and tetravalent ions. Oxygen vacancies may be formed by changing the oxidation value of cerium ions through transition metal doping. In addition, cerium oxide has a characteristic characteristic of oxygen storage capacity, and has been studied as a catalyst material for nitrogen oxide removal through selective catalytic reduction.

Recently, as it has been found that the properties of the amorphous catalyst are excellent, various studies have been conducted on the amorphous catalyst. This is because the selectivity of the catalytic reaction is increased in the case of the amorphous catalyst because there are many incomplete and broken bonds compared to the crystalline.

Ce-Ti oxide (ceria-titania complex) catalyst in which cerium oxide is supported on a support titanium oxide (TiO _X , titania) is impregnated with a solution of titania crystalline powder in cerium nitrate (Ce(NO ₃ ) ₃ , cerium nitrate) It is prepared by impregnation method, a method of coprecipitation with cerium nitrate using a titania precursor, or a sol-gel method, in which a high pressure heat treatment process is generally performed to prepare an amorphous catalyst. When synthesized using a commercial titania powder, it is reported that the titania crystallinity is strong, whereas when prepared by a co-precipitation method or a sol-gel method using a titania precursor, an amorphous catalyst can be synthesized.

However, looking at the high resolution TEM image of the Ce-Ti oxide that can be used as an amorphous catalyst prepared by the above method, a fine ceria or titania crystalline lattice is formed by random distribution on the surface of the support. Can be confirmed. Existing Ce-Ti oxides represented as amorphous have a ceria, titania or Ce-Ti oxide (cerium-titanium oxide) lattice crystallized on the surface, but are difficult to observe because they exist at a size of about 5 nm and are classified as amorphous catalysts. It was confirmed that it was present but not completely amorphous. In addition, in the case of the Ce-Ti oxide prepared in this way, the amount of ceria supported is limited, and when the ceria is added in excess, ceria crystalline particles precipitate to form agglomeration. Therefore, it is difficult to view the existing Ce-Ti oxides as an amorphous surface and an entire region. Therefore, there is a need for an amorphous Ce-Ti oxide over the entire area including the surface and a new technology for manufacturing the same.

One object of the present invention is to provide a method for producing an amorphous Ce-Ti oxide using amorphous Ce-Ti oxide and anhydrous ethanol.

A method for producing an amorphous Ce-Ti oxide for one purpose of the present invention comprises: a first step of preparing a mixed solution by mixing a titanium precursor and a cerium precursor using anhydrous ethanol as a solvent; And a second step of preparing cerium-titanium oxide with the mixed solution using a sol-gel method.

In one embodiment, the titanium precursor may be titanium isopropoxide (TTIP).

In one embodiment, the cerium precursor is cerium nitrate (Ce(NO ₃ ) ₃ ).

In one embodiment, after the first step, the precursor mixture solution may further include adjusting the pH to 4 to pH 11.

Amorphous Ce-Ti oxide for another purpose of the present invention is prepared through the method for preparing the amorphous Ce-Ti oxide of the present invention.

In one embodiment, the amorphous Ce-Ti oxide may be used as a catalyst for removing nitrogen oxides.

Amorphous Ce-Ti oxide may be provided through the method for preparing amorphous Ce-Ti oxide using ethanol anhydrous of the present invention. The amorphous Ce-Ti oxide of the present invention is an amorphous Ce-Ti oxide in which a crystal structure is not formed in all regions as compared with the conventional Ce-Ti oxide. In the case of amorphous Ce-Ti oxide, there are more incomplete bonds or broken bonds than crystalline Ce-Ti oxides, and thus, when used as a catalyst, selectivity is increased, and thus excellent catalyst efficiency can be exhibited.

1 is a view showing a completely amorphous Ce-Ti oxide according to an embodiment of the present invention.
2 is a view showing a comparative example.
3 to 5 are diagrams showing Ce-Ti oxide analysis results.
6 is a diagram of Ce-Ti oxide of Example 3.

The terms used in the present application are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "include" or "have" are intended to indicate the presence of features, steps, actions, components, parts or combinations thereof described in the specification, one or more other features or steps. It should be understood that it does not preclude the existence or addition possibility of the operation, components, parts or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains. Terms, such as those defined in a commonly used dictionary, should be interpreted as having meanings consistent with meanings in the context of related technologies, and should not be interpreted as ideal or excessively formal meanings unless explicitly defined in the present application. Does not.

In the present invention, ceria-titania (Ce-Ti oxide) uniformly amorphized throughout the entire area including the surface, which can be used as a catalyst, was synthesized.

A method of preparing an amorphous Ce-Ti oxide of the present invention comprises: a first step of preparing a mixed solution by mixing titanium precursor and cerium precursor using anhydrous ethanol as a solvent; And a second step of preparing cerium-titanium oxide with the mixed solution using a sol-gel method.

The mixed solution of the first step may be prepared by dissolving the titanium precursor in a solvent, and then adding the cerium precursor, dissolving the cerium precursor in a solvent, and then adding the titanium precursor. Can be one Alternatively, the cerium precursor and the titanium precursor may be prepared by dissolving each in a solvent and then mixing.

The solvent may be anhydrous ethanol.

In one embodiment, the titanium precursor includes titanium, but is not limited thereto, and may be titanium isopropoxide (TTIP), a titanium alkoxide-based material such as titanium butoxide, and mixtures thereof. Can be The titanium precursor may be used in a solution state by mixing with a solvent, that is, a titanium precursor solution.

In one embodiment, the cerium precursor may be cerium nitrate (Ce(NO ₃ ) ₃ ). The cerium precursor may be used in a solution state by mixing with a solvent, that is, a cerium precursor solution.

In one embodiment, after the first step, it may further include the step of adjusting the mixed solution to pH 4 to pH 11. For example, the precursor mixture solution may be adjusted to pH 5 or pH 10. The step of adjusting the pH is not limited thereto, and may be performed using an ammonia solution.

The amorphous Ce-Ti oxide of the present invention was prepared through the manufacturing method of the present invention.

In one embodiment, the amorphous Ce-Ti oxide may be used as a catalyst. For example, it can be used as a catalyst for removing nitrogen oxides.

In one embodiment, the amorphous Ce-Ti oxide is one in which a fine crystal structure of 1 nm or more is not formed.

As a result of XRD analysis, the amorphous Ce-Ti oxide does not show a peak (pattern) indicating at least one of ceria and titania. In other words, it is an amorphous structure in which a fine oxide crystal structure of 1 nm or more is not formed.

Hereinafter, embodiments of the present invention will be described in detail. However, the following examples are only some embodiments of the present invention, and the present invention should not be construed as being limited to the following examples.

Example 1

Titanium isopropoxide (TTIP) and cerium(Ce(NO ₃ ) ₃ , cerium(III) nitrate hexahydrate) are used as precursors through an embodiment, and anhydrous ethanol is used as a solvent. The amorphous Ce-Ti oxide of the present invention was prepared through a sol-gel method as follows.

Specifically, first, TTIP, a Ti precursor, and ethanol anhydride were mixed at a mass ratio of 1:5, and then 5 times anhydrous ethanol and a dispersant were further added to the anhydrous ethanol mixed to obtain a titanium precursor solution.

At this time, the titanium precursor solution may be obtained by mixing the TTIP and anhydrous ethanol to a mass ratio of about 1:30 from the beginning without dividing the step, and then adding a dispersant.

Then, cerium nitrate, a cerium precursor, was weighed so that the molar ratio of titanium and cerium was 7:3, and cerium nitrate was added to the titanium precursor solution to obtain a mixed solution. After this, the ammonia solution was reacted while slowly dropping the mixture to pH 10 (pH 9.5 to pH 10.5). The pH-adjusted mixed solution was stirred and aging at room temperature and normal pressure, then prepared as a Ce-Ti mixture, dried at 80°C, and heat-treated at 550°C to prepare Ce-Ti oxide powder.

Example 2 (Comparison of mixing order)

In Example 2, the same material as in Example 1 was used, and the oxide powder was prepared by changing only the order of preparing the mixed solution.

Specifically, cerium nitrate, a precursor of cerium, was dissolved in anhydrous ethanol to prepare a cerium precursor solution. Then, the titanium precursor TTIP was added by weighing so that the Ti:Ce molar ratio became 7:3, and stirred to obtain a mixed solution. Then, ammonia solution was added to the mixed solution to adjust the pH to 10 (pH 9.5 to pH 10.5). Then, the pH-adjusted mixed solution was prepared as a Ce-Ti mixture, dried at 80 °C, and heat-treated at 550 °C to prepare Ce-Ti oxide powder.

Example 3 (Cerium precursor comparison)

Example 3 is to prepare a Ce-Ti oxide powder by changing only the cerium precursor in Example 1.

Specifically, the titanium precursor TTIP was dissolved in anhydrous ethanol as a solvent to obtain a transparent titanium precursor solution. Cerium chloride was added to the titanium precursor solution as a cerium precursor and stirred to obtain a mixed solution. Then, ammonia solution was added to the mixed solution to adjust the pH to 10 (pH 9.5 to pH 10.5). The pH-adjusted mixed solution was prepared as a Ce-Ti mixture, dried at 80°C, and heat-treated at 550°C to prepare Ce-Ti oxide powder.

Example 4 (pH range comparison)

Example 4 is a change in only the pH range in Example 1 to prepare a Ce-Ti oxide powder.

Specifically, the titanium precursor TTIP was dissolved in anhydrous ethanol as a solvent to obtain a transparent titanium precursor solution. Cerium nitrate was added as a cerium precursor to the titanium precursor solution and stirred to obtain a mixed solution. Then, ammonia solution was added to the mixed solution to adjust the pH to 5 (pH 4.5 to pH 5.5). The pH-adjusted mixed solution was prepared as a Ce-Ti mixture, dried at 80°C, and heat-treated at 550°C to prepare Ce-Ti oxide powder.

Example 5 (Comparison of changes in order and pH range simultaneously)

In Example 5, the same material as in Example 1 was used, and an oxide powder was prepared by changing the order and pH range of the mixed solution preparation.

Specifically, cerium nitrate, a precursor of cerium, was dissolved in anhydrous ethanol to prepare a cerium precursor solution. Then, the titanium precursor TTIP was added by weighing so that the Ti:Ce molar ratio became 7:3, and stirred to obtain a mixed solution. Then, ammonia solution was added to the mixed solution to adjust the pH to 5 (pH 4.5 to pH 5.5). The pH-adjusted mixed solution was prepared as a Ce-Ti mixture, dried at 80°C, and heat-treated at 550°C to prepare Ce-Ti oxide powder.

Comparative Example 1 (solvent comparison)

Comparative Example 1 is to prepare a Ce-Ti oxide powder using ethanol only in the solvent in Example 1. Specifically, TTIP and ethanol were mixed at a mass ratio of 1:5, and then distilled water and a dispersant corresponding to 5 times the ethanol mass mixed above were further added to prepare a titanium precursor solution. Subsequently, cerium nitrate was added to the titanium precursor solution to obtain a mixed solution so that the molar ratio of titanium and cerium was 7:3 to the titanium precursor solution. After this, the ammonia solution was reacted while slowly dropping the mixture to pH 10 (pH 9.5 to pH 10.5). The pH-adjusted mixed solution was prepared as a Ce-Ti mixture, dried at 80°C, and heat-treated at 550°C to prepare Ce-Ti oxide powder.

Comparative Example 2 (titanium hydrolysis 1)

Comparative Example 2 was weighed so that the Ti:Ce molar ratio became 3:7, and cerium chloride was completely dissolved in anhydrous ethanol to prepare a cerium precursor solution, and TTIP was added to an aqueous and alcoholic solution to perform the hydrolysis. It was decomposed to prepare a titanium precursor solution. And the cerium precursor solution and the titanium precursor solution were mixed to obtain a mixed solution. In the case of Comparative Example 2, the pH was not adjusted, the mixed solution was prepared as a Ce-Ti mixture, dried at 80° C., and heat-treated at 550° C. to prepare Ce-Ti oxide powder.

Comparative example 3 (titanium Hydrolysis 2 )

In Comparative Example 3, the cerium nitrate was dissolved in anhydrous ethanol by weighing the Ti:Ce molar ratio to be 3:7, and a titanium precursor TTIP was added to an aqueous and alcoholic solution. Hydrolyzed to prepare a titanium precursor solution. And the cerium precursor solution and the titanium precursor solution were mixed to obtain a mixed solution. In the case of Comparative Example 3, the pH was not adjusted, and the mixed solution was prepared as a Ce-Ti mixture, dried at 80°C, and heat-treated at 550°C to prepare Ce-Ti oxide powder.

As a result of comparing Ce-Ti oxides prepared through Examples 1 to 5 and Comparative Examples 1 to 3, Ce-Ti oxides prepared through Examples 1 and 3-5 except for Example 3 show no crystallinity. Amorphous Ce-Ti oxide. In the case of Example 3 using cerium chloride, crystals were confirmed as shown in FIG. 7. In order to prepare amorphous Ce-Ti oxide, it is preferable that the cerium precursor is cerium nitrate. As a result of XRD analysis of Ce-Ti oxide of Comparative Example 1, a peak showing cerium oxide was found, and Ce-Ti oxides of Comparative Example 2 and Comparative Example 3 were Ce-Ti oxides in which titanium oxide crystals were present. Through this, it was found that cerium oxide or titanium oxide may be present on the surface depending on the synthesis method. The specific analysis results are shown through the drawings below.

1 is a TEM photograph of the amorphous Ce-Ti oxide according to Example 1, and FIG. 2 is a TEM photograph of the comparative example. Specifically, FIG. 1 shows a high-resolution transmission electron microscopy (HR-TEM) image of an amorphous Ce-Ti oxide prepared using anhydrous ethanol according to Example 1 of the present invention, and FIG. 2 shows Comparative Example 1 HR-TEM image of a conventional Ce-Ti oxide synthesized using ethanol is shown.

Titanium oxide crystals in the left image shown in FIG. 2 and cerium oxide crystals were confirmed in the right image in FIG. 2 (the image on the left in FIG. 2 is Ce-Ti Amorphous Oxides for Selective Catalytic Reduction of NO with NH3: Confirmation of Ce-Ti Active Sites Environ.Sci.Technol. (2012) 46 9600-9605 (left)). Referring to FIG. 2, it can be seen that a fine lattice of nanometer level (about 5 nm) exists. On the other hand, looking at Figure 1 showing the amorphous Ce-Ti oxide of the present invention, it can be confirmed that a fine crystal structure of 1 nm or more is not observed.

The titanium precursor, for example TTIP, can undergo a hydrolysis reaction with water. When TTIP and water undergo a hydrolysis reaction, TiO ₂ nuclei are generated and white particles may be formed as the nuclei grow. When the TiO ₂ nucleus is generated and then reacted with a cerium precursor, for example, cerium nitrate, the reaction region where the reaction occurs may be limited to a few nm region near the surface. Therefore, in the case of Comparative Example 1 using distilled water or ethanol as a solvent, excessively added ceria or titania crystals may be precipitated on the catalyst surface as shown in FIG. 2.

On the other hand, in the case of Example 1, which is prepared by using anhydrous ethanol as a solvent as in the present invention, TiO ₂ nuclei are not generated and can react with the cerium precursor in a transparently dissolved state in anhydrous ethanol, so that the reaction region is The reaction is not limited to the TiO ₂ surface and may occur in all regions. Therefore, an amorphous Ce-Ti oxide in which a fine crystal structure is not observed over the entire region can be formed.

3 and 6 are diagrams showing Ce-Ti oxide analysis results.

Specifically, FIG. 3 is a Ce-Ti oxide prepared using anhydrous ethanol as a solvent (Example 1) and a conventional Ce-Ti oxide prepared using ethanol as a solvent (Comparative Example 1) according to an embodiment of the present invention. The XRD (X-ray diffraction, X-Ray Diffraction) analysis results show that when comparing the two X-ray diffraction pattern graph, Example 1 (top graph), Comparative Example 1 using ethanol (bottom graph) It can be seen that unlike the CeO ₂ crystal phase does not appear.

4, electron diffraction pattern of Ce-Ti oxide prepared with an ethanol solvent through Comparative Example 1 on the left, electron diffraction of Ce-Ti oxide prepared with anhydrous ethanol as a solvent through Example 1 on the right. It shows the pattern. It can be seen that, unlike the electron diffraction pattern of Comparative Example 1 shown on the left, a relatively distinct ring pattern appears, but no pattern appears on the electron diffraction pattern of Example 1 shown on the right. Therefore, it can be confirmed that the crystal phase was not formed.

Referring to FIG. 5, the blue graph shown at the top shows the analysis results of Ce-Ti oxide of Comparative Example 2 using a cerium precursor (cerium chloride) and a titanium precursor (TTIP), and the red graph in the middle shows the cerium precursor (nitric acid The results of the Ce-Ti oxide analysis of Comparative Example 3 using cerium) are shown, and the black graph at the bottom shows the results of Example 3. (When interpreted together with the TEM image of FIG. 6, when using a single solvent of anhydrous ethanol and cerium chloride as a precursor, it appears that an amorphous catalyst was formed in the XRD phase, but observing the TEM image shows that crystalline lattice is observed as shown in FIG. 2. Can.)

6 is a photograph of Ce-Ti oxide of Example 3. Example 3 shows that cerium chloride was used as the cerium precursor in Example 1, but unlike Example 1 using cerium nitrate, Ce-Ti oxide shows crystallinity when cerium chloride is used. It may be desirable to use certain cerium precursors, such as the use of cerium nitrate, to obtain an amorphous Ce-Ti oxide.

3 to 5, regardless of the order of the pH range, the method of manufacturing, when producing Ce-Ti oxide using only anhydrous ethanol, an amorphous Ce-Ti oxide in which a crystal structure is not formed is produced. Able to know.

The amorphous Ce-Ti oxide prepared through the method for preparing an amorphous Ce-Ti oxide using anhydrous ethanol of the present invention is an amorphous Ce-Ti oxide in which a crystal structure is not formed in all regions compared to the conventional Ce-Ti oxide. There may be more incomplete bonds or broken bonds than the compound containing crystalline, and when used as a catalyst, selectivity is increased, and thus excellent efficiency can be exhibited.

Although described above with reference to the preferred embodiments of the present invention, those skilled in the art may variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. You will understand that you can.

Claims (7)

A first step of preparing a mixed solution by mixing titanium precursor and cerium precursor using anhydrous ethanol as a solvent; And
The second step of producing a cerium-titanium oxide (Ce-Ti oxide) with the mixed solution using a sol-gel (sol-gel) method; includes,
The prepared amorphous Ce-Ti oxide is characterized in that a fine crystal structure of 1 nm or more is not formed,
Method for manufacturing amorphous Ce-Ti oxide.
According to claim 1,
The titanium precursor is characterized in that it is titanium isopropoxide (Titanium isopropoxide),
Method for manufacturing amorphous Ce-Ti oxide.
According to claim 1,
The cerium precursor is characterized in that the cerium nitrate (Ce (NO ₃ ) ₃ ),
Method for manufacturing amorphous Ce-Ti oxide.
According to claim 1,
After the first step, characterized in that it further comprises the step of adjusting the precursor mixture solution to pH 4 to pH 11,
Method for manufacturing amorphous Ce-Ti oxide.
Prepared through any one of claims 1 to 4,
Amorphous Ce-Ti oxide.
The method of claim 5,
The amorphous Ce-Ti oxide is characterized in that it is used as a catalyst for removing nitrogen oxides,
Amorphous Ce-Ti oxide.
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