KR102309341B1 - Catalyst support having a core-shell structure with enhanced thermal stability and preparation method thereof - Google Patents

Abstract

The present invention relates to a catalyst carrier having a core-shell structure and a method for preparing the same, wherein the catalyst carrier has a core structure having a small specific surface area and a shell including SiC having high thermal conductivity. The metal catalyst can be supported in a small size on the surface of the support by suppressing the sintering of the metal catalyst by increasing the thermal conductivity of the support.

Description

CATALYST SUPPORT HAVING A CORE-SHELL STRUCTURE WITH ENHANCED THERMAL STABILITY AND PREPARATION METHOD THEREOF}

The present invention relates to a catalyst carrier having a core-shell structure with improved thermal stability and a method for preparing the same. Specifically, two kinds of inorganic materials are synthesized in a core-shell structure, and SiC is included in the shell It relates to a catalyst carrier and a method for preparing the same.

The present invention relates to an inorganic carrier used in a catalyst and a method for synthesizing the same. In general, the inorganic carrier used in the catalyst is used for high dispersion and structural stability of the metal, which is an active component of the catalyst. In order to maintain a high degree of dispersion of the metal catalyst even during a reaction with a large calorific value, the heat of reaction must be smoothly removed. Reaction heat is generated on the surface of the catalyst, and if it is not removed, a hot spot is partially created on the surface of the catalyst, which causes sintering of the metal catalyst. When the metal catalyst is sintered (when the size of the metal catalyst increases), the area of the metal catalyst exposed decreases, which leads to a decrease in catalytic activity.

As a method of suppressing the sintering of the metal catalyst, a high dispersion method utilizing the attractive force between the metal catalyst and the carrier (support) is generally used. However, the metal-support interaction has a disadvantage in that materials interacting with each other are limited. Accordingly, the method of removing the reaction heat in order to suppress the sintering of the metal catalyst does not need to consider the attractive force between the metal catalyst and the carrier.

In the present invention, a catalyst carrier having a core-shell structure with increased thermal stability has been developed. For the core, an inorganic material with a small specific surface area, for example, α-alumina (α-Al ₂ O ₃ ) is used, and for the shell, silicon carbide (SiC) with excellent thermal conductivity and an inorganic material such as θ-alumina, α-alumina or a mixture thereof was used. The thermal conductivity of α-Al ₂ O ₃ is 30 W/mK, and the thermal conductivity of SiC is 360 to 490 W/mK, and SiC is more than 12 times superior in thermal conductivity than alumina. Accordingly, when the thermal stability of the catalyst carrier is increased, it is possible to effectively suppress the phenomenon of sintering the metal catalyst.

Accordingly, the present invention provides a method for improving catalytic activity by providing a catalyst carrier having a core-shell structure and including SiC having excellent thermal conductivity in the shell.

An object of the present invention is to improve the thermal stability of a catalyst by improving the thermal properties of a catalyst carrier used for an exothermic reaction. Specifically, the present invention is a catalyst carrier having a core-shell structure in which an inorganic material with a small specific surface area is used as a core and the core is coated with a shell containing SiC and an inorganic material having high thermal conductivity. Metal supported by increasing the thermal stability of the catalyst It aims at suppressing sintering of a catalyst.

In order to achieve the above object, the present invention

A catalyst carrier having a core-shell structure, comprising:

The shell comprises 20 to 50% by weight of SiC,

The components of the core and the shell are each independently selected from the group consisting of silica, alumina, zirconia and titania.

Also, the present invention

(a) adding a first inorganic material and SiC to distilled water, adding an acid solution, and stirring at room temperature to produce a mixture;

(b) gelling the mixture by adding a second inorganic material and an alkalizing agent;

(c) drying the product obtained in step (b) at 60 to 110°C; and

(d) calcining the product obtained in step (c) at 1000 to 1300° C. for 8 to 12 hours to obtain a catalyst carrier having a core-shell structure,

The first inorganic material and the second inorganic material are each independently selected from the group consisting of silica, alumina, zirconia and titania.

In the prior art, there is no technique for improving the thermal stability of the catalyst by synthesizing a catalyst carrier to which SiC is added in a core-shell structure. In the present invention, by introducing SiC into the shell of the catalyst support having a core-shell structure, the thermal conductivity of the catalyst support is increased, thereby providing an effect of suppressing sintering of the metal catalyst.

1 is a schematic diagram of a catalyst carrier having a core-shell structure containing SiC in a shell according to an embodiment of the present invention.
2 is a SEM-EDS analysis result of the surface of a catalyst carrier having a core-shell structure to which SiC is added according to an embodiment of the present invention. In the SEM image, it _{was difficult to distinguish between SiC and Al 2} O ₃ , so it was confirmed that SiC was distributed on the surface through EDS analysis, which is an elemental analysis. It is confirmed that SiC is shown in purple in FIG. 2 and is distributed in the size of several tens of micro units.
3 is a core-shell structure containing 30% by weight and 50% by weight of Ag supported on a catalyst carrier having a core-shell structure without SiC according to Comparative Example 1 of the present invention and SiC of Examples 1 and 2, respectively; SEM analysis result image of Ag supported on the catalyst carrier of
4 shows Ag supported on a core-shell structure catalyst carrier not containing SiC according to Comparative Example 1 of the present invention and Ag supported on a core-shell structure catalyst carrier containing SiC of Examples 1 and 2; This is an image of the SEM analysis result of Ag after heat treatment at 300° C. for 1 hour.

In the present invention, a catalyst carrier having a core-shell structure was synthesized by adding SiC to increase the thermal stability of the catalyst carrier. SiC was added to the shell portion of the catalyst carrier and the amount added was 20 to 50% by weight.

When the SiC content is lower than 20% by weight, the effect of increasing the thermal stability of the catalyst is insignificant, and when the SiC content is higher than 50% by weight, the SiC may not be stably bonded to the core.

In one embodiment, the present invention provides a catalyst carrier in which two kinds of inorganic substances are synthesized in a core-shell structure.

In one embodiment, the present invention provides

A catalyst carrier having a core-shell structure, comprising:

The shell comprises 20 to 50% by weight of SiC,

The components of the core and the shell are each independently selected from the group consisting of silica, alumina, zirconia and titania.

In one embodiment, the core of the present invention is an aggregate of the component particles and the core is surrounded by the component particles of the shell, and the average diameter of the particles of the shell to the average diameter of the particles of the core is from 1:80 to 1: 150 or 1:90 to 1:130.

In one embodiment, the core of the catalyst carrier of the present invention is one of a ring, a sphere, a macaroni or a cylinder shape.

In one embodiment, the component of the core of the invention is α-alumina (α-Al ₂ O ₃ ).

In one embodiment, the component of the shell of the present invention is θ-alumina, α-alumina, or mixtures thereof.

In one embodiment, the catalyst carrier of the present invention is _{coated on the surface of the Al 2} O ₃ core by mixing tens of micrometers of silicon carbide particles with alumina.

In one embodiment, the SiC content of the shell of the present invention is between 30 and 50% by weight.

In one embodiment, the specific surface area of the catalyst carrier of the present invention is 0.6 to 1.0 m 2 /g.

In one embodiment, the metal supported on the catalyst carrier of the present invention is at least one selected from the group consisting of Ag, Pd and Pt.

In one embodiment, the present invention provides

(a) adding a first inorganic material and SiC to distilled water, adding an acid solution, and stirring at room temperature to produce a mixture;

(b) gelling the mixture by adding a second inorganic material and an alkalizing agent;

(c) drying the product obtained in step (b) at 60 to 110°C; and

(d) calcining the product obtained in step (c) at 1000 to 1300° C. for 8 to 12 hours to obtain a catalyst carrier having a core-shell structure,

The first inorganic material and the second inorganic material are each independently selected from the group consisting of silica, alumina, zirconia and titania.

In one embodiment, in the method for preparing the catalyst carrier of the present invention, the component of the core is α-alumina (α-Al ₂ O ₃ ).

In one embodiment, in the method for preparing the catalyst carrier of the present invention, the component of the shell is θ-alumina, α-alumina, or a mixture thereof.

In one embodiment, in the method for preparing the catalyst carrier of the present invention, the SiC content of the shell is 30 to 50% by weight.

In one embodiment, in the method for preparing the catalyst support of the present invention, the specific surface area of the catalyst support is 0.6 to 1.0 m 2 /g.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

Example 1 : Synthesis of alumina carrier with core-shell structure

(1) Boehmite (aluminium oxide hydroxide) and 30 wt% of SiC were added to distilled water (100ml) and stirred.

(2) To the mixed solution from (1) was added nitric acid (1.5 ml).

(3) α-alumina (α-Al ₂ O ₃ ) was added to the mixture from (2) and stirred at room temperature for 30 minutes.

(4) After adding aqueous ammonia (15 ml) to the mixed solution from (3), the mixture was stirred at room temperature for 30 minutes to gelation.

(5) The synthesized carrier from (4) was sieved and dried in an oven (80° C.) for 24 hours.

(6) The dried carrier was calcined at 1100° C. for 10 hours under air flow to obtain _{a catalyst carrier having a core-shell structure (α-Al 2} O ₃ /SiC+θ-alumina and α-alumina mixture). prepared.

Example 2 : Synthesis of alumina carrier with core-shell structure

The core-shell structure (α-Al ₂ O ₃ /SiC+θ-alumina and α- A mixture of alumina) was prepared as a catalyst carrier.

Comparative Example 1

_{A catalyst carrier having a core-shell structure (a mixture of α-Al 2} O ₃ /θ-alumina and α-alumina) was prepared in the same manner as in Preparation Example 1 except that SiC was not added.

Experimental Example 1 : Ag supported on catalyst carrier

1) Ag supported on the catalyst carrier synthesized in Example 1

(1) 7 g of silver oxalate was added to distilled water (7 ml) and stirred while cooling to 5°C.

(2) 3.5 ml of 92% by weight of ethylenediamine (8% by weight is H ₂ O) was added with respect to the total weight of the solution from (1) and stirred while cooling to 5°C.

(3) Re ₂ O ₇ (37.4 mg) and (NH ₄ ) ₆ Mo ₇ O _24· 4H ₂ O (3.7 mg) were respectively dissolved in a mixed solution (1 ml) of ethylenediamine and aqueous ammonia.

(4) LiNO ₃ (28 mg) and Cs ₂ CO ₃ (18.3 mg) were each dissolved in distilled water (1 ml).

(5) The solutions of Re, Mo, Li, and Cs of (3) and (4) were put into the stirred solution of (2) and stirred while cooling to 5°C.

(6) All of the precursor solution completed in (5) was absorbed into 15 g of the catalyst carrier having a core-shell structure prepared in Preparation Example 1.

(7) The catalyst carrier absorbing the precursor solution was dried under reduced pressure.

(8) The catalyst carrier dried under reduced pressure was heat-treated at 300° C. for 1 hour under an air flow. The finished (Re, Mo, Li, Cs)Ag/(α-Al ₂ O ₃ /SiC+θ-alumina and α-alumina mixture) catalyst contains 20 wt% silver (Ag) and 360 ppm rhenium It contains (Re), contains 100 ppm of molybdenum (Mo), contains 750 ppm of cesium (Cs), and contains 140 ppm of lithium (Li).

2) Ag supported on the catalyst carrier synthesized in Example 2

_{(Re, Mo, Li, Cs)Ag/(α-Al 2} O ₃ /SiC+θ-alumina) in the same manner as in Experimental Example 1, except that the catalyst carrier having a core-shell structure prepared in Example 2 was used. and α-alumina) catalyst was prepared.

3) Ag supported on the catalyst carrier synthesized in Comparative Example 1

(Re, Mo, Li, Cs)Ag/(α-Al ₂ O ₃ / A mixture of θ-alumina and α-alumina) catalyst was prepared.

Experimental Example 2 : Heat treatment

To confirm the thermal stability of the three supported catalysts prepared in Experimental Example 1, heat treatment was performed at 300° C. for 1 hour. Table 1 below shows the specific surface area of the carrier according to the SiC addition amount and the particle size according to the SEM analysis of the supported Ag.

In addition, the SEM-EDS analysis result of the surface of the support having a core-shell structure to which SiC is added according to Examples 1 and 2 above is shown in FIG. 2 , and the SiC-free core-shell structure carrier according to Comparative Example 1 Figure 3 shows the SEM analysis result image of Ag supported on the Ag supported on the carrier of the core-shell structure containing the SiC of Examples 1 and 2 and. In addition, the SEM analysis result image after heat-treating the Ag-supported catalyst at 300° C. for 1 hour is shown in FIG. 4 .

carrier SiC content
(weight%) Specific surface area (m ² /g) Ag supported catalyst Ag particle size (nm) before heat treatment after heat treatment Comparative Example 1:
Core-shell (Al ₂ O ₃ ) 0 0.74 Comparative Example 1:
Ag/core-shell (Al ₂ O ₃ ) 214 515 Example 1:
Core-shell (SiC + Al ₂ O ₃ ) 30 0.88 Example 1:
Ag/core-shell (SiC + Al ₂ O ₃ ) 260 396 Example 2:
Core-shell (SiC + Al ₂ O ₃ ) 50 0.69 Example 2:
Ag/core-shell (SiC + Al ₂ O ₃ ) 217 335

The Ag particle sizes listed in Table 1 are the average Ag particle sizes on the SEM images of FIGS. 3 and 4 . From FIGS. 3 and 4 , it can be confirmed the extent of Ag sintering through the Ag particle size change before and after the heat treatment of the Ag-supported catalyst. In the case of using the carrier of Comparative Example 1 in which SiC was not added, the size of Ag was very large after heat treatment (average size 214 nm → 515 nm), and the size of Ag in the case of using the carriers of Examples 1 and 2 in which SiC was added was determined by heat treatment. It was confirmed that even after Comparative Example 1 was maintained in a small state (Example 1: 260nm → 396nm, Example 2: 217nm → 335nm).

Therefore, according to the present invention, as a carrier of a core-shell structure including two inorganic substances, the carrier containing SiC in the shell suppresses the sintering of the supported metal catalyst compared to the carrier without adding SiC, thereby increasing the size of the metal catalyst. It provides the effect of increasing the thermal stability of the metal catalyst by suppressing the growth.

As the specific parts of the present invention have been described in detail above, for those of ordinary skill in the art, it is clear that these specific descriptions are only preferred embodiments, and the scope of the present invention is not limited thereby. something to do. Accordingly, it is intended that the substantial scope of the present invention be defined by the appended claims and their equivalents.

Claims (12)

A catalyst carrier having a core-shell structure, comprising:
A component of the core is α-alumina (α-Al ₂ O ₃ ),
The component of the shell is a mixture of θ-alumina and α-alumina,
The shell is a catalyst carrier comprising 20 to 50% by weight of SiC. The catalyst carrier according to claim 1, wherein the core of the catalyst carrier is one of a ring, a sphere, a macaroni, and a cylinder shape. delete delete The catalyst carrier according to claim 1, wherein the SiC content of the shell is 30 to 50 wt%. The catalyst support according to claim 1, wherein the specific surface area of the catalyst support is 0.6 to 1.0 m 2 /g. The catalyst carrier according to claim 1, wherein the metal supported on the catalyst carrier is at least one selected from the group consisting of Ag, Pd and Pt. (a) adding boehmite (aluminium oxide hydroxide) and SiC as a first inorganic material to distilled water, adding an acid solution, and stirring at room temperature to produce a mixture;
(b) gelling the mixture by adding α-alumina (α-Al ₂ O _{3 ) and an alkalizing agent as a second inorganic material;}
(c) drying the product obtained in step (b) at 60 to 110°C; and
(d) calcining the product obtained in step (c) at 1000 to 1300° C. for 8 to 12 hours to obtain a catalyst carrier having a core-shell structure. delete delete The method according to claim 8, wherein the SiC content of the shell is 30 to 50 wt%. The method according to claim 8, wherein the specific surface area of the catalyst support is 0.6 to 1.0 m 2 /g.

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