KR20130066916A - Method to improve catalytic activities by employing network-typed pore structure in formed-catalyst - Google Patents

Abstract

PURPOSE: A catalyst having micro and macro pores and a manufacturing method thereof are provided to maintain micro pores, to form macro pores properly inside of the catalyst, to secure enough paths for reactants to move inside of the catalyst together by maintaining the high intrinsic activity of a catalyst, and to maximize catalytic activity. CONSTITUTION: A manufacturing method of a catalyst having micro and macro pores comprises the following steps: a step of molding and calcinating a mixture of catalyst powder, a binder, and 25-60 parts by weight of pore control material of to the weight of catalyst powder. The catalyst powder is manufactured by a precipitation method. Average particle diameter of the catalyst powder is 1-10um. The binder comprises a binding agent, a plasticizer, and a solvent. The binding agent is cellulose series or polyvinyl alcohol. The plasticizer is glycerine. The pore control material is starch. Calcination is carried out at 500-650 deg. C.

Description

[0001] The present invention relates to a method for improving catalytic performance by forming network-like macropores in a catalyst,

The present invention relates to a method for promoting catalytic activity by forming network-type macropores in a catalyst, and more particularly, to a method for increasing the catalytic activity by introducing a pore-controlling substance into a catalyst, To a pore control method of a catalyst capable of maximizing the performance of the catalyst by preparing macropores having a network structure.

The production method of the catalyst can be classified into the impregnation method and the precipitation method. The impregnation method is a method of preparing a catalyst by impregnating a preformed support with an active material. In the precipitation method, the active material and the support material are precipitated together to obtain a powdery catalyst, . Since the impregnation method and the precipitation method each have advantages and disadvantages, a suitable method is selected according to the purpose and place of use to prepare the catalyst.

The precipitation method can be usefully used when the active material is contained at a high concentration or when a catalyst having strong bond between the active material and the support is produced. The impregnation method has difficulties in supporting active materials such as noble metals, nickel and the like on the support at high concentration.

The precipitation method specifically produces a catalyst by precipitation of solid particles produced by reacting precursor solutions with each other, and the prepared catalyst has a shape of a powder state. In order to use it in an actual process, it is molded into a spherical or cylindrical shape through a molding process. As the molding method, an extrusion or tableting method or the like can be used.

Pores of various sizes are present in the catalyst prepared by the precipitation method. These pores can be classified into micro-pores (2 nm or less in diameter), meso-pores (2 to 50 nm in diameter), and macro-pores (50 nm or more in diameter).

The micropores are directly related to the specific surface area size of the catalyst. If the number of micropores is large, the specific surface area of the catalyst becomes large, and the number of active sites of the catalyst increases, and the intrinsic activity of the catalyst increases. Therefore, in order to prepare a highly active catalyst, it is necessary to prepare a catalyst having many micropores.

On the other hand, mesopores and macropores are pores that act as a channel for reactants and products. When the catalytic reaction is activated and proceeds rapidly, more reactants are supplied from the outside to the catalytic active sites. If the movement of the reactant increases abruptly, the flow will be resisted. This state is called a mass diffusion limited region. In actual catalytic reactors, most of them are used in the region of mass transfer control. Therefore, to overcome the mass transfer dominant region, meso and macropores should be as large as possible in the catalyst.

In order to enhance the intrinsic activity of the catalyst and, at the same time, to obtain a catalytic reaction with a limited mass transfer restriction, both nano-pores, mesopores, and macropores must be increased at the same time. However, it is practically impossible to increase three types of pores at the same time in the catalyst produced by the precipitation method. The catalysts prepared by the precipitation method have a tendency that meso and macro pores are reduced when the number of the nano pores is increased in the catalyst, and that the nanopores are decreased when the meso and macro pores are increased.

Therefore, in order to obtain a catalyst having excellent performance, it is necessary to make as many mesopores or macropores as possible so as to increase the nano pore as much as possible to increase the intrinsic activity of the catalyst and to minimize the mass transfer restriction of the catalyst reactant.

In this connection, U.S. Patent No. 4,632,714 describes a method for producing macropores in a catalyst using a porosity regulating material. However, the pore volume of the catalyst prepared in the above patent is 0.31 cm ³ / g, which means that it is difficult to expect an increase effect of macropores.

The present invention contemplates a method for efficiently producing macropores in a catalyst prepared by a precipitation method without affecting the micropores present in the catalyst. Particularly, it is possible to increase the pore volume of the macropores by providing a network-like structure in which macropores generated in the catalyst are connected to each other to connect with each other, thereby minimizing the migration resistance of the reactants during the catalytic reaction How to do it.

The present invention relates to a method for preparing a catalyst having macropores comprising molding and calcining a mixture of 25 to 60 parts by weight of the pore control material relative to the weight of the catalyst powder, the binder and the catalyst powder.

Hereinafter, the method for producing the catalyst according to the present invention will be described in more detail.

The kind of the catalyst powder in the present invention is not particularly limited, and a catalyst powder produced by a precipitation method can be used.

As the precipitation method, a coprecipitation method, a homogeneous precipitation method, or a sequential precipitation method can be used. In the preparation of the catalyst powder by the precipitation method, the active material and the support are simultaneously precipitated to obtain a powdery catalyst, the ratio of the active material can be freely adjusted, and the mutual binding force between the active material and the support is strengthened, It is possible to produce an excellent catalyst powder.

Preferably, the catalyst powder prepared in Korean Patent Laid-Open Publication No. 2009-0117082 can be used in the present invention.

Specifically, a nickel-alumina catalyst prepared by mixing a nickel nitrate aqueous solution, an aluminum nitrate aqueous solution and an urea solution, followed by aging and firing can be used.

In the present invention, a step of pulverizing the catalyst powder may be further carried out. By pulverizing the catalyst powder, a catalyst powder having a uniform size can be obtained, and mixing with the binder and the pore controlling material can be facilitated.

The catalyst powder may be pulverized using a ball mill, a high-speed pulverizer, a jet mill or the like, preferably a ball mill or a high speed pulverizer.

In the present invention, the average particle diameter of the catalyst powder may be 1 to 10 mu m. It is easy to uniformly mix the binder and the pore controlling material at the particle diameter within the above range, and it is easy to manufacture a catalyst having macropores. When the average particle size of the catalyst powder prepared by the precipitation method is 1 to 10 탆, the pulverization process can be omitted.

In the present invention, the binder includes a binder, a plasticizer and a solvent. The binder may be mixed with the catalyst powder and the pore-controlling material to facilitate the extrusion.

The binder is an element that affects the viscosity and the binding force of the mixture of the catalyst, the binder and the pore-controlling material. Examples of the binder include organic-based cellulose or polyvinyl alcohol, and preferably cellulose-based methylcellulose MC, methyl cellulose) can be used. The binder may be used in an amount of 1 to 10 parts by weight, specifically 2 to 8 parts by weight, based on the weight of the catalyst powder. The binder strength is excellent in the above content range, and the removal of the binder from the extruded catalyst product is easy.

In addition, the plasticizer enhances the moldability of a mixture of a catalyst, a binder and a pore-controlling material, and glycerin may be used as the plasticizer. The plasticizer may be used in an amount of 1.0 to 10 parts by weight, specifically 2 to 8 parts by weight, based on the weight of the catalyst powder. The formability and binding force of the mixture is excellent in the above content range. When glycerin is used as the plasticizer, not only the plasticizer but also the lubricant which reduces the frictional force at the time of extrusion can be simultaneously performed.

As the solvent, water (distilled water) can be used.

In the present invention, the binder may be used in an amount of 50 to 150 parts by weight based on the weight of the catalyst powder. In this range, extrusion of the mixture of the catalyst powder, the binder and the pore-controlling material can be easily performed.

In the present invention, when the porosity regulating material is mixed with the catalyst powder and the binder and is completely incinerated through the firing after completion of the molding, the porosity regulating material serves to provide void space having the same volume and shape as the porosity regulating material inside the catalyst.

For example, starch particles, polyvinyl alcohol particles or polyethylene glycol particles extracted from grains can be used. Preferably, starch particles, such as starch Particles can be used. The starch particles extracted from the grains, that is, the grain starch have an average particle diameter of 1 to 100 μm, specifically 10 to 50 μm, and the above grain starch can be used as a macropore controlling substance of the catalyst, .

First, it is possible to easily select a pore control material having a size suitable for controlling the macro pore size. Because starch has various sizes depending on the type of grain, it is possible to select the kind of starch according to the macro pore size to be obtained. In addition, since starch is composed of amylose and amylopectin, no poisoning is given to the catalyst. Further, when starch is used as the porosity regulating material, starch can be completely incinerated through a sintering operation at a high temperature after molding by extrusion. Since the starch has a characteristic of being completely incinerated in an air atmosphere of 500 to 650 ° C, the removal operation is easy after extrusion. In addition, since starch is inexpensive and is a grain component, it has an advantage that it is harmless to health when it is handled.

The types and particle sizes (particle diameters) of the starch particles usable in the present invention are shown in Table 1 below. In Table 1, the gelatinization temperature refers to a temperature at which starch is converted into gelatin when it is dissolved in water.

Starch type Particle size (탆) Gelatinization temperature (℃) range Average corn 5-25 15 62-72 wheat 2-35 20 52-63 rice 3-8 5 61-78 Sorghum 6-30 26 69-75 sweet potato 2-40 18 69-75 potato 15-100 33 59-68

As shown in Table 1, the average particle size of starch (hereinafter referred to as rice starch) extracted from rice is the smallest at 5 μm and the average particle size of corn starch (hereinafter referred to as corn starch) is 15 μm. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an electron microscope (SEM) photograph of corn starch (a) and potato starch (b) in the present invention. Both starches have a rounded shape and corn starch is smaller than potato starch.

Specifically, in order to produce a catalyst having small macropores, it is preferable to use rice starch having an average particle diameter of 5 탆, and in order to produce a catalyst having a large macropore, potato starch having an average particle size of 33 탆 is preferably used . Also, if necessary, the above grain cores can be appropriately mixed and used.

The content of the pore controlling material directly affects the properties of macropores and the mechanical strength of the catalyst. Specifically, when the amount of the pore-controlling material is insufficient, macropores are not sufficiently formed. On the contrary, when the amount of pore-controlling material is too large, macropores are sufficiently generated, but there is a possibility that the strength of the catalyst becomes weak.

Also, the content of the porosity controlling material affects the structure of macropores produced in the catalyst. Specifically, when the amount of the pore-controlling material is insufficient, macro-pores generated in the catalyst are dispersed. In this case, macro-pores in the catalyst during the catalytic reaction are not sufficiently utilized as a passage for reactant, can not do. Accordingly, it is important to control the amount of the pore-controlling material introduced so that macropores generated in the catalyst penetrate each other to form a network-like structure.

Therefore, in the present invention, the pore control material may be included in an amount of 25 to 60 parts by weight, specifically 40 to 50 parts by weight, based on the weight of the catalyst powder. In the above range, the macro pore formation rate and the strength of the produced catalyst are excellent. Macro pores may have a reticulated structure in the above content range.

In the present invention, the above-mentioned mixing of the catalyst powder, the binder and the pore-controlling material can be carried out by a general method used in the art.

In the present invention, the mixture of the catalyst powder, the binder and the porosity regulating material may be molded and fired to finally produce the catalyst.

In the present invention, extrusion molding may be used. As the molding machine used in the extrusion molding method, a piston type extrusion molding machine or a screw type extrusion molding machine can be used, and it is preferable to use a screw type extrusion molding machine to facilitate continuous extrusion.

The mixture extruded by the extrusion molding method may be further subjected to a step of drying before firing. The drying can be carried out in a drying oven at 80 to 150 DEG C for 12 to 30 hours.

In the present invention, firing is carried out to remove the binder and the pore-controlling material in the extruded mixture. The calcination may be performed in an air atmosphere and at 500 to 650 ° C for 3 to 12 hours. The binder and the pore controlling material are removed through firing, and the catalyst in which macropores are generated can be finally removed.

The present invention also relates to a catalyst prepared by the above-mentioned method for producing a catalyst, wherein the catalyst has micro or mesopores of 50 nm or less and macropores of 1 to 100 탆, Gt; pore structure. ≪ / RTI >

In the present invention, macropores of 1 to 100 탆 are connected to each other through a network structure, so that the reactants can easily pass through the network structure in which the pores are connected during the catalytic reaction, thereby maximizing the catalytic activity.

In the present invention, the pore volume of micro or mesopores of 50 nm or less may be 0.2 to 1.0 cm < ³ > / g.

Further, the pore volume of macropores of 1 to 100 mu m may be 0.2 to 3.0 cm < ³ > / g.

Further, the total pore volume of the catalyst may be 0.5 to 3.0 cm < ³ > / g. The catalytic activity of the catalyst according to the present invention can be maximized by having the pore volume in the above range.

The catalyst prepared by the production method according to the present invention maintains the micropores while appropriately producing macropores inside the catalyst. As a result, it is possible to maximize the catalytic activity since it can maintain a high intrinsic activity of the catalyst and ensure sufficient passage for the reactant to move into the catalyst.

1 is an electron microscope (SEM) photograph of corn and potato starch used in the present invention.
FIG. 2 is a view illustrating a process for producing a catalyst according to an embodiment of the present invention.
3 is an SEM photograph of the catalyst prepared according to Examples and Comparative Examples of the present invention.
4 is a graph showing the results of analyzing the pore distribution of the catalysts prepared according to Examples and Comparative Examples of the present invention.
5 is a graph showing the results of experiments on the performance of methane steam reforming according to Examples and Comparative Examples of the present invention.

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

FIG. 2 is a process diagram of a catalyst according to an embodiment of the present invention.

As shown in FIG. 2, the catalyst is prepared by preparing a catalyst powder using a precipitation method or the like, mixing the catalyst powder with a binder and a pore-controlling material, extruding and firing (removing a binder and a pore-controlling material) Can be finally manufactured. At this time, the powder catalyst may be further pulverized.

Hereinafter, the present invention will be described in more detail with reference to Examples. Embodiments of the present invention are for the purpose of detailed description and are not intended to limit the scope of the rights.

Example

1. Catalyst Powder Production

A Ni / Al ₂ O ₃ catalyst powder having a nickel content of 50 wt% was prepared using a uniform precipitation method using urea as a precipitant. The preparation of the catalyst powder was carried out according to the method of Korean Patent Publication No. 2009-0117082.

The prepared Ni / Al ₂ O ₃ catalyst powder was pulverized using a high-speed crusher. The average particle size of the catalyst powder after grinding was 4 탆.

 2. Binder manufacturing

The weight ratio of the binder methylcellulose (4000 cP, Kanto chemical) and distilled water was 5: 100, and the mixture was homogeneously mixed using a stirrer.

3. Preparation of porosity control substance

Corn starch was used as a porogen.

4. Catalyst Manufacturing

100 parts by weight of the catalyst powder prepared in the above item 1 was uniformly mixed with 50 parts by weight of corn starch using a high speed mill, 100 parts by weight of the binder prepared in 2. was added, and the mixture was uniformly mixed with a high speed mill to prepare a mixture .

The prepared mixture was molded using an extrusion molding machine. At this time, the extrusion molding machine was a piston type molding machine, and the nozzle diameter of the extrusion molding machine was 2.0 mm. Specifically, the mixture was placed in an extruder cylinder and extruded through a nozzle under pressure (up to 10 tonnes).

The molded mixture was dried in a drying oven for 24 hours. After drying was completed, the final catalyst was prepared by calcining in an air atmosphere at 600 ° C. for 6 hours in a firing furnace.

Comparative Example 1

A catalyst was prepared in the same manner as in Example except that corn starch was used in an amount of 20 parts by weight.

Comparative Example 2

The catalyst was prepared in the same manner as in Example except that no porosity control material was used.

Experimental Example

1. Measurement of shape of catalyst

The catalysts prepared according to Examples and Comparative Example 1 were measured for their shapes using an electron microscope (SEM, S4800, Hitachi). The measured results are shown in Fig.

FIG. 3 (a) is an SEM photograph of the catalyst prepared according to the embodiment, and FIG. 3 (b) is a SEM photograph of the catalyst prepared according to the comparative example.

3, it can be seen that the catalyst (a) prepared according to the embodiment has macro pores formed therein, and the pore size is almost the same as the average particle size (15 μm) of the corn starch used as the pore controlling material have. In particular, it can be seen that the catalyst prepared according to the embodiment has a network structure in which macropores are connected to each other.

In the catalyst (b) prepared in Comparative Example 1, it was confirmed that macropores were generated by the corn starch. However, the macropores were dispersed and the pores were not connected to each other.

2. Measurement of pore distribution

The pore distribution of the catalysts prepared in Examples and Comparative Examples 1 and 2 was measured using a mercury porosimeter (Micrometics). The measured results are shown in Fig.

In FIG. 4, the catalyst prepared by the Example, the starch 20% + catalyst, the catalyst prepared by Comparative Example 1, and the starch 0% + catalyst have pore distribution of the catalyst prepared by Comparative Example 2 .

As shown in FIG. 4, in Comparative Example 2 in which no porosity regulating material was used and in Comparative Example 1 where 20 parts by weight of the porosity regulating material was used, there was one peak in the range of 10 to 20 nm, In the range of 10 to 20 nm and in the range of 2 to 3 mu m in the example using 50 parts by weight of the polymer. This is because macropores are generated in the interior of the catalyst due to the pores of the catalyst of the examples.

In the case of Comparative Example 1, although having macropores, the pore distribution analysis shows different results in which macropores are not observed. This is because the macropores of the catalyst prepared in Comparative Example 1 are dispersed and distributed and the pores are not connected to each other. This fact implies that macro-pores can be effective macro-pores when the macro-pores are connected to each other when the pore-controlling material is used to produce macro-pores.

On the other hand, the pore volume was 0.45 cm ³ / g for the catalyst prepared in Comparative Example 2, and 1.21 cm ³ / g for the catalyst prepared in the Example. This is because the pore volume is increased due to the porosity control material.

3. Modification reaction experiment

In order to analyze the methane steam reforming activity of the catalysts prepared according to Examples and Comparative Examples 1 and 2, a reaction experiment was conducted in a fixed bed reactor made of a 0.375-inch quartz tube. The catalyst was used in a cylindrical shape having a diameter of 1.8 mm and a length of 2.0 mm. The amount of catalyst was 200 mg, the flow rate of methane was 150 cm ³ / min, and the flow rate of water (water vapor) was 300 cm ³ / min. The catalyst was subjected to reduction treatment for 1 hour at a flow rate of hydrogen gas (10% H ₂ / N ₂ ) at a flow rate of 100 cm ³ / min and at a temperature of 700 ° C. before performing the full steam reforming experiment. The product gas after the steam reforming reaction was analyzed using GC (Agilent 3000 Micro GC). The results are shown in FIG.

As shown in FIG. 5, in the case of Comparative Example 2 in which the porosity regulating material was not used, the methane conversion was about 64%, which was lower than the methane conversion of the embodiment of about 81%. As a result, it can be seen that the catalyst having pore control by injecting the porosity controlling material has better catalytic performance than the catalyst having no porosity.

In addition, the methane conversion of Comparative Example 1 using 20 parts by weight of corn starch was about 72%, which was higher than that of Comparative Example 2, but lower than that of Examples.

This is because the catalyst of Comparative Example 1 does not have a network structure in which macropores are connected to each other, and thus has a lower methane conversion rate than the embodiment.

Claims (11)

A method for preparing a catalyst having micro and macro pores comprising molding and firing a mixture of 25 to 60 parts by weight of the pore control material relative to the weight of the catalyst powder, binder and catalyst powder.
The method of claim 1, wherein
The catalyst powder is a method for producing a catalyst having micro and macro pores is prepared by the precipitation method.
The method of claim 1, wherein
A method for producing a catalyst having micro and macro pores, the average particle diameter of the catalyst powder is 1 to 10 ㎛.
The method of claim 1, wherein
The binder is a process for producing a catalyst having micro and macro pores comprising a binder, a plasticizer and a solvent.
The method of claim 4, wherein
The binder is cellulose-based or polyvinyl alcohol, and a method for preparing a catalyst having micro and macro pores comprising 1 to 10 parts by weight based on the weight of the catalyst powder.
The method of claim 4, wherein
Plasticizer is glycerin, the production method of the catalyst having micro and macro pores comprising 1 to 10 parts by weight based on the weight of the catalyst powder.
The method of claim 1, wherein
A pore control material is a method of preparing a catalyst having micro and macro pores of starch.
The method of claim 7, wherein
Starch is a method for producing a catalyst having micro and macro pores having an average particle diameter of 1 to 100 ㎛.
The method of claim 1,
Firing is a method for producing a catalyst having micro and macro pores at 500 to 650 ℃.
A catalyst having micro or meso pores of 50 nm or less and macro pores of 1 to 100 μm, wherein the macro pores have a reticulated pore structure connected to each other.
11. The method of claim 10,
The total pore volume of the catalyst is from 0.5 to 3.0 cm ³ / g.

Images