KR100956957B1 - Porous manganese-aluminum composite oxide catalyst, preparation method thereof and preparation method of 2-cyclohexene-1-ol using the catalyst - Google Patents

Abstract

The present invention relates to a porous manganese-aluminum composite oxide catalyst, a method for preparing the same, and a method for preparing 2-cyclohexen-1-ol using the catalyst, and more particularly, an aluminum hydroxide cation having a keggin structure (AlO ₄ Al). ₁₂ (OH) ₂₄ (H ₂ O) _{12 7} ⁺ and a manganese precursor prepared by a method including the step of sintering after the hydrothermal synthesis reaction, the average particle diameter of 5 to 50 nm and Mn / Al molar ratio range of 10 to 50 The present invention relates to a porous manganese-aluminum composite oxide catalyst, a method for preparing the same, and a method for preparing 2-cyclohexen-1-ol using the catalyst, wherein the porous manganese oxide-aluminum oxide composite prepared according to the present invention is a conventional manganese. Unlike oxide, it has the advantage of maintaining the nano size of 10-20 nm even after sintering at high temperature and improving the crystallinity. Of manganese-in aluminum composite oxide, and also it indicates the advantage of exhibiting high catalytic activity for the oxidation of cyclo-hexene molecule.

Manganese-Aluminium Composite Oxide, Catalyst, Hydrothermal Synthesis, Sintering, Crystalline

Description

POROUS MANGANESE-ALUMINUM COMPLEX METAL OXIDE CATALYST, PREPARATION METHOD THEREOF AND PREPARATION METHOD OF 2-CYCLOHEXENE-1-OL USING SAID CATALYST}

The present invention relates to a porous manganese-aluminum composite oxide catalyst, a method for preparing the same, and a method for preparing 2-cyclohexen-1-ol using the catalyst, and more particularly, an aluminum hydroxide cation having a keggin structure (AlO ₄ Al). ₁₂ (OH) ₂₄ (H ₂ O) _{12 7} ⁺ and a manganese precursor prepared by a method including the step of sintering after the hydrothermal synthesis reaction, the average particle diameter of 5 to 50 nm and Mn / Al molar ratio range of 10 to 50 The present invention relates to a porous manganese-aluminum composite oxide catalyst, a method for producing the same, and a method for preparing 2-cyclohexen-1-ol using the catalyst.

Manganese oxide has various applications such as electrodes, biphasic catalysts, adsorbents, biosensors, etc. for electrochemical energy storage devices, and many studies have been conducted because it has advantages in industrial applications such as low price, abundant reserves, and low toxicity. come. In addition, many attempts have been made to develop various nanostructured manganese oxides, as the specific surface area can be increased by increasing the specific surface area when the particle size is reduced to nanometer level, compared to the bulk state with microcrystalline size. Are being done.

In order to develop such various metal oxide nanostructures, various methods such as gas phase-liquid-solid phase method, reverse micelle method, and hydrothermal synthesis method exist. Among them, hydrothermal synthesis method that can be easily and simply reacted at low temperature is mainly used. However, since the reaction by hydrothermal synthesis is mostly performed at low temperature, it often shows amorphous or low crystallinity. Since there is a need to improve the crystallinity of the metal oxide in order to optimize the functionality, for this purpose, the crystallinity of the metal oxide is improved through a high temperature sintering process. However, this high temperature sintering process not only improves the crystallinity of the metal oxide but also increases the particle size. This results in the loss of the advantages attributed to the nanocrystal size.

Therefore, the technical problem to be achieved in the present invention is to prepare a manganese-aluminum composite oxide of manganese-aluminum oxide, the manufacturing process is easy and simple, porous manganese-aluminum having a high crystallinity while maintaining a nanometer particle size It is to provide a composite oxide catalyst and a method of manufacturing the same.

It is another object of the present invention to provide a method for preparing 2-cyclohexene-1-ol by cyclohexene oxidation in the presence of the catalyst.

In order to achieve the above technical problem, the present invention includes the step of sintering the aluminum hydroxide cation (AlO ₄ Al ₁₂ (OH) ₂₄ (H ₂ O) _{12 7} ⁺ ) and manganese precursor of the keggin structure after the hydrothermal synthesis reaction It is prepared by the method, and provides a porous manganese-aluminum composite oxide catalyst, characterized in that the average particle diameter of 5 to 50 nm and Mn / Al molar ratio ranges from 10 to 50.

In addition, the present invention comprises the steps of hydrothermally synthesizing the aluminum precursor and manganese precursor of the keggin structure; Ii) It provides a method for producing a porous manganese-aluminum composite oxide catalyst comprising the step of sintering at a temperature in the range of 400 to 800 ℃.

In addition, the present invention provides a method for producing a porous manganese-aluminum composite oxide catalyst, characterized in that hydrothermal synthesis of the aluminum precursor and manganese precursor.

In addition, the present invention provides a method for producing a porous manganese-aluminum composite oxide catalyst, characterized in that the manganese precursor is a permanganate.

In order to achieve another object of the present invention, the present invention is a method for producing 2-cyclohexen-1-ol by the oxidation reaction of cyclohexane, characterized in that the oxidation reaction is carried out in the presence of the catalyst Provided is a method for preparing 2-cyclohexen-1-ol.

The porous manganese-aluminum composite oxide catalyst prepared according to the present invention maintains a nano-size of 5-50 nm even after a sintering process at high temperature, unlike a conventional manganese oxide, even though it is not complicated. Has the advantage of being. In addition, the porous manganese-aluminum composite oxide catalyst of the present invention is a manganese-aluminum composite oxide with aluminum oxide having excellent reactivity and selectivity, and also exhibits an advantage of showing high catalytic activity against oxidation of cyclohexene molecules.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The porous manganese-aluminum composite oxide catalyst of the present invention includes a step of sintering an aluminum hydroxide cation (AlO ₄ Al ₁₂ (OH) ₂₄ (H ₂ O)) ₁₂ ⁷⁺ having a keggin structure and a manganese precursor after hydrothermal synthesis. Prepared by the method, the average particle diameter is 5 to 50 nm and Mn / Al molar ratio is characterized in that 10 to 50 range.

 The porous manganese-aluminum composite oxide catalyst of the present invention comprises the steps of: hydrothermally synthesizing an aluminum precursor having a kegin structure and a manganese precursor; Ii) sintering at a temperature ranging from 400 to 1,200 ° C. In the method for preparing a porous manganese-aluminum composite oxide catalyst of the present invention, hydrothermal synthesis is preferably performed in a range of 50 to 150 ° C. Since the hydrothermal reaction is well known to those of ordinary skill in the art to which the present invention pertains, no further description will be given herein.

As described above, in the case of the general inorganic catalyst, when sintered, the particles become large particles due to the growth of the particles, thereby degrading the catalytic activity. However, the manganese-aluminum composite oxide catalyst of the present invention has excellent crystallinity as the particle size can be maintained in the range of 5 to 50 nm while improving crystallinity through high temperature sintering.

In the preparation of the manganese-aluminum composite oxide catalyst of the present invention, the sintering step is preferably performed at a temperature in the range of 400 to 1,200 ° C, preferably at a temperature in the range of 400 to 800 ° C. If the sintering is carried out below 400 ℃ the improvement of crystallinity is insignificant, whereas if it exceeds 1,200 ℃ catalyst particles after sintering is too large.

Hereinafter, the present invention will be described in more detail with reference to examples which are preferred embodiments of the present invention.

(Manufacture) Example and Comparative Example

An aqueous solution of Al ₁₃ ⁷⁺ keggin cluster ion was prepared by dropping 26 ml of a 2.79 M sodium hydroxide solution into 200 ml of a 0.2 M aqueous aluminum nitrate solution. At this time, the OH / Al molar ratio was 1.8. Separately, 50 ml of an aqueous 0.12 M permanganic acid solution was prepared as a manganese precursor. Permanganic acid solution and 0.0136 M Al ₁₃ ⁷⁺ keggin aqueous solution were mixed in a hydrothermal reactor so that the molar ratio of Mn / Al was 18, and the mixture was hydrothermally synthesized for 3 hours while maintaining a temperature of 70 ° C. for manganese-aluminum composite oxide. Was prepared. The dark wet powder obtained after the reaction was separated through a centrifuge, washed with ethanol and dried in an oven at 60 ℃ to obtain a manganese-aluminum composite oxide. In order to improve the crystallinity of the manganese-aluminum composite oxide, heat treatment was performed in air at 400, 600 and 800 ° C. for 3 hours.

1 is an X-ray diffraction pattern of a porous manganese-aluminum composite oxide powder. In Figure 1 each a) is a manganese-aluminum composite oxide obtained by hydrothermal synthesis, b) manganese-aluminum composite oxide heat-treated at 400 ℃, c) manganese-aluminum composite oxide heat-treated at 600 ℃ and d) manganese-heat treatment at 800 ℃ Aluminum composite oxide. The manganese-aluminum composite oxide synthesized through hydrothermal synthesis at 70 ° C. and the manganese-aluminum composite oxide heat-treated at 400 ° C. had an amorphous structure in which no Bragg peak was observed, and had a small particulate form. It was found that the manganese-aluminum composite oxide powder heat-treated at 600 ° C. had a crystal structure of α-MnO ₂ having 2 × 2 pores and the above fine particle shape, and the manganese-aluminum composite oxide powder heated at 800 ° C. was Mn ₃ O _4. / Mn ₂ O _{3 It} was confirmed to have a crystal structure and a particulate form. Since the XRD peak due to aluminum oxide is not observed even after the heat treatment, it is interpreted that the aluminum oxide exists in an amorphous state.

In addition, Raman spectroscopy was performed to confirm the local structural state change of the manganese-aluminum composite oxide due to heat treatment. 2 is a Raman spectroscopic analysis of the porous manganese-aluminum composite oxide synthesized according to the present invention. In Fig. 2, respectively, a) represents manganese-aluminum composite oxide obtained by hydrothermal synthesis, b) manganese-aluminum composite oxide heat treated at 400 ° C., c) manganese-aluminum composite oxide heat treated at 600 ° C., and d) manganese heat treated at 800 ° C. It is the spectrum of aluminum composite oxide. According to the XRD results, the manganese-aluminum composite oxide powder heat-treated at 600 ° C. showed a Raman spectrum corresponding to α-MnO ₂ and a spectrum corresponding to Mn ₃ O ₄ / Mn ₂ O ₃ after 800 ° C. heat treatment. Although the Raman spectrum reflects the local structure well, no Raman peak corresponding to aluminum oxide was observed. Among various aluminum oxide phases, α-Al ₂ O ₃ and β-Al ₂ O ₃ show characteristic Raman peaks, but γ-Al ₂ O ₃ hardly exhibits Raman peaks. Therefore, it can be interpreted that the aluminum oxide in the synthesized nanocomposite is stabilized by the structure of γ-Al ₂ O ₃ .

In order to confirm the form of the crystal structure thus obtained, scanning electron microscopy (SEM) was confirmed. In Fig. 3, respectively, a) represents manganese-aluminum composite oxide obtained by hydrothermal synthesis, b) manganese-aluminum composite oxide heat treated at 400 ° C., c) manganese-aluminum composite oxide heat treated at 600 ° C., and d) manganese heat treated at 800 ° C. Scanning electron micrograph of aluminum composite oxide. As shown in FIG. 3, manganese-aluminum composite oxide synthesized through hydrothermal synthesis at 70 ° C. and manganese-aluminum composite oxide subjected to heat treatment at 400 ° C., 600 ° C. and 800 ° C. were confirmed to have particulate forms. In addition, it was measured using a transmission electron microscope (TEM) to cross-check each crystal size, crystal form, and elemental components. As shown in Figure 4 a) is a manganese-aluminum composite oxide obtained by hydrothermal synthesis, b) manganese-aluminum composite oxide heat-treated at 600 ℃. As shown in FIG. 3, it can be seen that a) and c) both manganese-aluminum composite oxides are in particulate form. Small pictures below the images of a) and b) show spots for Selected Area Electron Diffraction. It was confirmed that a) amorphous and b) tetragonal structure. 5 a) and b) are quantitative analysis results using EDS Mapping of a) manganese-aluminum composite oxides obtained by hydrothermal synthesis and b) manganese-aluminum composite oxides heat-treated at 600 ° C., respectively. This shows that aluminum and manganese ions are evenly distributed, confirming the synthesis of manganese-aluminum composite oxide. The thermogravimetric analysis (TGA) results of the synthesized manganese-aluminum composite oxide precursors are shown in FIG. 6. From FIG. 6, the synthesized manganese oxide-aluminum oxide manganese-aluminum composite oxide shows a sudden mass loss of 22% at around 220 ° C. due to the removal of adsorbed water molecules and hydroxyl groups. It was also confirmed that there was a slight mass loss around 620 ℃ because of the decrease in oxygen content due to the reduction of manganese +4 ions into +3 ions. FIG. 7 is a graph showing isothermal adsorption and desorption curves through BET analysis for measuring specific surface areas of porous manganese-aluminum composite oxide powders. The observed hysteresis confirms that they have a porous structure. In addition, the specific surface area of each powder shows: a) manganese-aluminum composite oxide (416 m ² / g) obtained by hydrothermal synthesis, b) manganese-aluminum composite oxide (333 m ² / g), heat-treated at 400 ° C., c) Manganese-aluminum composite oxide (145 m ² / g) heat-treated at 600 ° C, (d) Manganese-aluminum composite oxide (68 m ² / g) heat-treated at 800 ° C, and the specific surface area decreased with increasing temperature. This indicates that the sintering between the particles in the heat treatment process increases the size of the particles.

(Use) Examples and Comparative Examples

8 to 12 show the results of evaluating catalytic activity for cyclohexane oxidation. FIG. 8 is a porous manganese-aluminum composite oxide obtained by hydrothermal synthesis, FIG. 9 is a manganese-aluminum composite oxide heat-treated at 400 ° C, FIG. 10 is a manganese-aluminum composite oxide heat-treated at 600 ° C, and FIG. 12 is a graph showing the aluminum composite oxide, and FIG. 12 is a graph showing the reactivity according to temperature and the selectivity to 2-cyclohexene-1-ol within 2 hours. After the heat treatment at 600 ° C., the manganese-aluminum composite oxide was found to be a highly active oxidation catalyst having a conversion frequency of 90% or more and selectivity to 60% 2-cyclo-hexene-1-ol after 15 minutes. This result shows that the porous manganese-aluminum composite oxide catalyst has a high activity as an oxidation catalyst of the olefin molecule.

One embodiment of the present invention described above should not be construed as limiting the technical spirit of the present invention. The protection scope of the present invention is limited only by the matters described in the claims, and those skilled in the art can change and change the technical idea of the present invention in various forms. Therefore, such improvements and modifications will fall within the protection scope of the present invention, as will be apparent to those skilled in the art.

1 is a powder X-ray diffraction graph showing the crystal structure of the porous manganese-aluminum composite oxide prepared in the (Manufacture) Examples and Comparative Examples of the present invention

2 is a Raman spectrum of the porous manganese-aluminum composite oxide prepared in the (Manufacture) Examples and Comparative Examples of the present invention

3 is a scanning electron microscope (SEM) photograph of the crystalline form of the porous manganese-aluminum composite oxide prepared in (Manufacture) Examples and Comparative Examples of the present invention

FIG. 4 is a transmission electron microscope (TEM) photograph and a selected area electron diffraction graph of the crystal form and crystal structure of the porous manganese-aluminum composite oxide prepared in the (Manufacture) Examples and Comparative Examples of the present invention.

5 is an EDS mapping result of the porous manganese-aluminum composite oxide prepared in the (Manufacture) Examples and Comparative Examples of the present invention.

Figure 6 is a graph of the weight loss using the thermogravimetric analyzer of the porous manganese-aluminum composite oxide prepared in the (Manufacture) Example and Comparative Example of the present invention

Figure 7 is a graph showing the isothermal adsorption and desorption curves through the BET analysis of the porous manganese-aluminum composite oxide prepared in (Manufacture) Examples and Comparative Examples of the present invention

8 is a graph showing the catalytic activity of a porous manganese-aluminum composite oxide obtained by hydrothermal synthesis

9 is a graph showing the catalytic activity of a manganese-aluminum composite oxide heat-treated at 400 ℃

10 is a graph showing the catalytic activity of a manganese-aluminum composite oxide heat-treated at 600 ℃

11 is a graph showing the catalytic activity of a manganese-aluminum composite oxide heat-treated at 800 ℃

12 is a graph showing the reactivity and temperature selectivity for 2-cyclohexene-1-ol within 2 hours ((a), (b), (c) and (d) shows the results of manganese-aluminum composite oxides which were not heat treated, and manganese-aluminum composite oxides which were heat treated at 400 ° C., 600 ° C. and 800 ° C., respectively.

Claims (5)

It is prepared by a method including the step of sintering after the hydrothermal synthesis of aluminum hydroxide cation (AlO ₄ Al ₁₂ (OH) ₂₄ (H ₂ O) _{12 7} ⁺ ) of the keggin structure and the manganese precursor, A porous manganese-aluminum composite oxide catalyst having an average particle diameter of 5 to 50 nm and a Mn / Al molar ratio in the range of 10 to 50. Iii) hydrothermally synthesizing an aluminum precursor and a manganese precursor having a kegin structure; Ii) A method for producing a porous manganese-aluminum composite oxide catalyst comprising the step of sintering at a temperature ranging from 400 ° C to 800 ° C. The method of claim 2, The method of preparing a porous manganese-aluminum composite oxide catalyst, characterized in that the keggin aluminum precursor and manganese precursor has a Mn / Al molar ratio of 10 to 50. The method according to claim 2 or 3, The kegin-structured aluminum precursor is a keggin-structured aluminum hydroxide cation (AlO ₄ Al ₁₂ (OH) ₂₄ (H ₂ O) ₁₂ ⁷⁺ , and the manganese precursor is a permanganate, characterized in that the porous manganese-aluminum composite Oxide catalyst production method.  In the method for producing 2-cyclohexen-1-ol by oxidation of cyclohexane, The oxidation reaction is carried out in the presence of the catalyst of claim 1, characterized in that 2-cyclohexene-1-ol.

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