KR102216948B1 - Catalyst for low temperature using hexagonal boron nitride and its preparation method - Google Patents

Abstract

The present invention relates to a denitrification catalyst using hexagonal boron nitride and a method for manufacturing the same, and specifically, to a denitrification catalyst that is stable at high temperatures and has improved catalytic efficiency and physical properties by providing a hexagonal boron nitride as a support and a method for manufacturing the same. About.
Using hexagonal boron nitride, which is a stable material as a catalytically active material and a support, it exhibits the effect of inhibiting the phase change and aggregation of the catalyst. It provides a denitration catalyst and a manufacturing method thereof.

Description

Denitrification catalyst using hexagonal boron nitride and its preparation method {Catalyst for low temperature using hexagonal boron nitride and its preparation method}

The present invention relates to a denitrification catalyst using hexagonal boron nitride and a method for manufacturing the same, and specifically, to a denitrification catalyst that is stable at high temperatures and has improved catalytic efficiency and physical properties by providing a hexagonal boron nitride as a support and a method for manufacturing the same. About.

As attention has recently been focused on the atmospheric environment, various regulations (EURO6, Tier III, special measures for fine dust, etc.) on gaseous pollutants emitted from various industrial fields such as fixed sources (power plants, incinerators) and mobile sources (cars, ships) It is being strengthened. Accordingly, various technologies for satisfying regulations are being studied.

Nitrogen oxide (NO _x ), one of the most well-known air pollutants, is very harmful to the human body by itself, but it is the main cause of the generation of fine dust, smog, and acid rain. There are several techniques for removing nitrogen oxides, but the most efficient SCR (Selective Catalytic Reduction) and selective catalytic reduction are typically used.

SCR technology is a technology that converts nitrogen oxides (NO _x ) into nitrogen and water vapor that are harmless to the human body by using NH ₃ and Urea as reducing agents. Korean Patent Registration '10-1798713' describes an SCR catalyst for removing nitrogen oxides and its manufacturing method, and says that an SCR catalyst having excellent nitrogen oxide removal performance and convenience is needed in accordance with the continuous increase in demand and strengthening environmental regulations. have. However, the SCR catalyst currently applied to various pollutants uses V ₂ O ₅ -WO ₃ as a catalytically active material based on TiO ₂ support, and is used in a high temperature range of 350 to 380°C, so it is efficient in terms of thermodynamics and economy. Is lowered.

Therefore, research is being conducted on the development of highly efficient SCR catalysts that can be used in the low temperature (below 300℃) region, and common catalytically active materials include V ₂ O ₅ , MoO ₃ and WO ₃ , and MnO _x , CeO in the low temperature region. ₂ and Co ₃ O ₄ . However, as the content of the active ingredients increases, there is a problem in that the surface is easily aggregated and a phase change occurs.

KR 10-1798713)

Recent Trends in Hexagonal Boron Nitride, 2016.07, DOI 10.3938)

In order to solve the above problem, the present invention includes a hexagonal boron nitride (h-BN) having excellent thermal and chemical stability, including phase change and agglomeration inhibition, and at the same time, surface modification by improving the dispersibility of the catalytically active material. It aims to provide a denitration catalyst having excellent furnace efficiency and properties.

In addition, an object of the present invention is to provide a selective catalytic reduction (SCR) catalyst comprising hexagonal boron nitride and having the above-described superiority.

In addition, an object of the present invention is to provide a method for producing a low-temperature denitration catalyst containing hexagonal boron nitride having the above excellent effects.

In order to solve the above object, the present invention,

Catalytically active material; And

It provides a denitration catalyst comprising; hexagonal boron nitride (h-BN), which is a support for the catalytically active material.

The catalytically active material includes any one or more of MnO, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , CeO ₂ , Co ₃ O ₄ , ZrO _2, V ₂ O ₅ , and WO ₃ , and 100°C- It can be activated at a temperature of 300°C.

In addition, the hexagonal boron nitride has a porous surface and a thickness of 80-100 nm.

In order to solve the above other object, the present invention,

Catalytically active material; And

It provides a selective catalytic reduction (SCR) catalyst comprising; hexagonal boron nitride, which is a support for the catalytically active material.

The hexagonal boron nitride has a porous surface and a thickness of 80-100 nm.

In addition, the catalytically active material may be activated at a temperature of 100°C-300°C.

In order to solve the another object, the present invention,

Stirring the catalytically active material and hexagonal boron nitride;

catalytic synthesis of the mixture through a sol-gel method; And

It provides a method for producing a denitration catalyst comprising a; sintering step for inducing a porous surface to the hexagonal boron nitride of the catalyst.

The catalytically active material includes any one or more of MnO, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , CeO ₂ , Co ₃ O ₄ , ZrO _2, V ₂ O ₅ , and WO ₃ .

In addition, the catalyst is an SCR catalyst, and can be activated at a temperature of 100°C-300°C.

The present invention provides a catalytically active material and a low-temperature denitration catalyst using hexagonal boron nitride, which is a stable material as a support, and a method of manufacturing the same, thereby showing the effect of inhibiting the phase change and aggregation of the catalyst, and improving the dispersibility of the catalytically active material. Due to the reforming, the efficiency and physical properties of the catalyst are excellent.

1 shows a catalyst synthesis process according to an Example and a Comparative Example of the present invention.
2 is a graph showing the denitration efficiency of a porous h-BN catalyst and a non-porous h-BN catalyst according to an embodiment of the present invention.
3 is a graph showing the denitration efficiency of porous h-BN catalysts having different weight ratios and BN thickness conditions according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

According to one aspect of the present invention, a catalytically active material; And hexagonal boron nitride (h-BN), which is a support for the catalytically active material, and provides a denitration catalyst.

In the present invention, the catalytically active material includes at least one of MnO, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , CeO ₂ , Co ₃ O ₄ , ZrO _2, V ₂ O ₅ , and WO ₃ . Preferably it includes any one or more of MnO, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , CeO ₂ , Co ₃ O ₄ , and ZrO ₂ , and more preferably MnO, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , CeO ₂ , And It includes any one or more of Co ₃ O ₄ .

The catalytically active material may be activated at a temperature of 100°C-300°C. Preferably it may be activated at a temperature of 150 ℃-300 ℃, more preferably it may be activated at a temperature of 200 ℃-300 ℃.

In addition, hexagonal boron nitride has a porous surface and has a thickness of 80-100 nm. More specifically, it is hexagonal boron nitride in which a porous surface is induced through a heat treatment process in an air atmosphere.

Catalysts are catalytically active substances that exhibit catalytic activity and cocatalysts that improve catalytic activity or extend the life of the catalyst, and support that supports these catalytically active substances and cocatalysts and provides a high surface area to increase the reaction area. That is, it is composed of a support.

The conditions that a carrier, which plays a very important role in the use of a catalyst, must have a wide surface area and a wide contact area, and a low heat capacity and a low coefficient of thermal expansion of the material, due to its application characteristics. In addition, the use temperature, strength, and oxidation resistance should be high, and the coating properties and compatibility of the carrier and catalyst should be good.

Carriers can be broadly divided into metal-based and ceramic-based depending on the material of the composition. The carrier provides a relatively high surface area such as silica and alumina carriers depending on the chemical reaction and interaction with the catalytically active material, but does not have catalytic activity and is an inert carrier that performs only the role of a support, and a catalyst such as a silica-alumina carrier or zeolite carrier It can be classified into an active support having some activity and a catalytically active material interaction support that has a strong interaction with the catalytically active material such as titanium dioxide and Nb ₂ O ₅ .

Boron Nitride is a ceramic material having a variety of structures (hexagonal, cubic, and wurtzite), and has various properties such as high thermal stability and electrical insulation. Other than that, precision processing is possible, so it is indispensable as an insulating material for vacuum equipment and experimental equipment used in a heated state. In addition, it is used as an insulating material for transistors, IC substrates, and sealing heaters because of its characteristics of electrical insulation and high thermal conductivity.

Among them, hexagonal boron nitride (h-BN) having a hexagonal structure in a plate shape as a 2D material has a high melting point of 2970℃ and is a stable material that maintains its properties up to 1000℃ in air. Research is ongoing. h-BN is a strong covalent bond where boron and nitrogen are bonded, so it does not have an unsaturated bond on the surface, and has a flat structure at the atomic level. In addition, similar to graphene, it has excellent mechanical properties that are transparent, flexible, and sturdy, and has excellent thermal conductivity while having insulating properties, and has thermal or chemical stability.

Porous materials are characterized by excellent adsorption power because they have numerous pores, and for this reason, they have a high surface area and volume per unit mass. Porous materials facilitate loading of various active materials and catalysts, and if the pores can be controlled at the nanometer level and nanostructures can also be controlled, it can be used for nano adsorption and separation, sensors, catalysts, optical materials, energy materials The application of is possible. In general, nanoporous materials are classified into microporous (2 nm or less), mesoporous (2-50 nm), and macroporous (50 nm or more) depending on the size of the pores. The porous material has a high surface area, so it is possible to make a catalyst with a high degree of dispersion while using only a minimum amount. In addition, improved activity and stability may be obtained by uniformly supporting nanometer-sized particles in the pores or on the walls.

According to another aspect of the present invention, a catalytically active material; And it provides a selective catalytic reduction (Selective Catalytic Reduction, SCR) catalyst comprising; and hexagonal boron nitride, which is a support for the catalytically active material.

The catalytically active material may be activated at a temperature of 100°C-300°C. Preferably it may be activated at a temperature of 150 ℃-300 ℃, more preferably it may be activated at a temperature of 200 ℃-300 ℃.

In addition, hexagonal boron nitride has a porous surface and has a thickness of 80-100 nm. More specifically, it is hexagonal boron nitride in which a porous surface is induced through a heat treatment process in an air atmosphere.

Selective Catalytic Reduction (SCR) is to purify exhaust gas by contacting the SCR catalyst, and with the help of the SCR catalyst, nitrogen oxides (NOx) in the exhaust gas are converted into nitrogen and water that are harmless to the human body and then discharged. At this time, ammonia (NH ₃ ) or urea water (Urea) is used as a reducing agent, and the reducing agent is injected to the catalyst heated to a high temperature to selectively reduce only nitrogen oxides in the exhaust gas.

SCR catalysts include metal oxide, zeolite, alkaline earth metal, and rare earth catalysts, but catalytically active substances such as WO ₃ , V ₂ O ₅ and MoO _{3 using} sulfated TiO ₂ as a carrier are combined. A honeycomb-shaped monolithic honeycomb extrusion catalyst is commercially available. However, these honeycomb-shaped monolithic catalysts are expensive due to the use of TiO ₂ used as a carrier and WO ₃ and V ₂ O ₅ as catalytic active materials, and the production cost of the catalyst is high due to poor moldability compared to other carrier materials. .

Hexagonal boron nitride has a porous surface and is 80-100 nm thick. More specifically, it is hexagonal boron nitride in which a porous surface is induced through a heat treatment process in an air atmosphere. Hexagonal Boron Nitride (h-BN), which has a hexagonal structure in a plate shape as a 2D material, has a high melting point of 2970℃ and is a stable material that maintains its properties up to 1000℃ in air. It is going on. h-BN is a strong covalent bond where boron and nitrogen are bonded, so it does not have an unsaturated bond on the surface, and has a flat structure at the atomic level. In addition, similar to graphene, it has excellent mechanical properties that are transparent, flexible, and sturdy, and has excellent thermal conductivity while having insulating properties, and has thermal or chemical stability.

According to another aspect of the present invention, the step of stirring the catalytically active material and hexagonal boron nitride; catalytic synthesis of the mixture through a sol-gel method; And a sintering step for inducing a porous surface on the hexagonal boron nitride of the catalyst. It provides a method for producing a denitration catalyst.

The catalytically active material includes one or more of MnO, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , CeO ₂ , Co ₃ O ₄ , ZrO _2, V ₂ O ₅ , and WO ₃ . Preferably it includes any one or more of MnO, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , CeO ₂ , Co ₃ O ₄ , and ZrO ₂ , and more preferably MnO, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , CeO ₂ , And It includes any one or more of Co ₃ O ₄ .

The catalyst is an SCR catalyst and can be activated at a temperature of 100°C-300°C. Preferably it may be activated at a temperature of 150 ℃-300 ℃, more preferably it may be activated at a temperature of 200 ℃-300 ℃.

In the sol-gel method, a metal monomer dissolved in a solution generally reacts with water, and a condensation reaction occurs after hydrolysis. sol means that a solid is in a colloidal state in a liquid phase, and a gel has a viscoelastic property like a semi-solid. The advantage of sol-gel processing is that low-temperature synthesis is possible, various shapes and microstructures can be adjusted, homogeneity can be improved, environment-friendly productivity can be improved, and all raw materials generating -OH groups can be used as materials, and organic -Can easily make inorganic hybrid compounds. The advantage of the sol-gel method is that it is possible to obtain a chemical composition that cannot be obtained by a conventional method, a homogeneous solid can be obtained in atomic order, and a high purity substance can be obtained.

Nanomaterials produced by the sol-gel method are largely divided into xerogel and aerogel. Zerogel is used as a general material because it changes from sol to gel and changes into large particles with relatively high density during drying and firing. However, as the name suggests, airgel is mostly made up of pores, so it is very light and is therefore used as a functional material including catalysts. In general, an aerosol is prepared by a sol-gel reaction, and the resulting gel is supercritically dried so that the original structure of the gel is maintained without shrinking. Since it has such a peculiar pore structure, aerosols have very good various physical properties, and if they are effectively utilized, they can be applied in a wide variety of fields. Recently, it has been newly recognized that aerosols have a large surface area and pore volume and that they are synthesized by a sol-gel process capable of controlling solid properties at the atomic stage, and thus, research for full-scale application in the field of catalyst manufacturing is actively being started.

A general characteristic of aerosols is that the basic structure of the gel is maintained, so the surface area and pore volume are very large. In particular, since the catalytic chemical reaction that goes through the adsorption step and the surface reaction step occurs on the surface of the catalyst, the large surface area means that the number of active sites on the surface of the catalyst where the reaction can occur is large. It can be a useful material. In addition, most catalysts are in the form of dispersing metals or other oxides on the oxide surface. As the surface area of the support increases, the amount of metal or oxide that can be dispersed as a monolayer on the support increases, increasing the active site of the catalyst. It is also useful as Aerosols having such characteristics have a relatively slow rate of reduction in surface area due to heat treatment-type sintering due to their unique strong pore structure.

Hexagonal boron nitride in the present invention may be included in 50-90 wt%, preferably 70-85 wt% as a support for the catalytically active material. If the support, hexagonal boron nitride, is included in less than 50 wt%, it is difficult to fulfill its role as a support, and when included in an amount in the range of 50 to 90 wt%, effective denitrification efficiency can be achieved even if the weight ratio of the catalytically active material is low.

Hereinafter, the present invention will be described in more detail by the following examples. However, the following examples are intended to illustrate the present invention, and the scope of the present invention is not limited by the examples. The disclosure of the present invention is provided to be complete, and to fully inform the scope of the invention to those of ordinary skill in the art to which the present invention pertains.

<Example>

Example 1. Preparation of a catalyst containing porous hexagonal boron nitride (porous h-BN)

Solution1 was prepared by dissolving Mn(NO ₃ ) ₂ ·4H ₂ O, Ce(NO ₃ ) ₂ ·6H ₂ O, which are precursors of catalytically active materials, in ethanol, and solution2 was prepared by dissolving h-BN powder in ethanol. . For dispersion and dissolution of each solution, the solution was stirred for 15 minutes after ultrasonication for 30 minutes, and solution1 was poured into solution2 and stirred for 6 hours in order to support (Mn-Ce) on h-BN, thereby preparing solution3. In order to evaporate the ethanol of solution3, the temperature was maintained at 80℃ for 6 hours.

After that, the catalyst was synthesized by the sol-gel method, heat-treated at 250°C, and sintered in an air atmosphere to prepare a catalyst having h-BN with a porous surface induced.

The process of preparing the catalyst is shown in FIG. 1.

Example 2. Evaluation of denitrification efficiency of porous h-BN catalyst

A fixed bed was used as the evaluation equipment, and a chemi-luminescent detection analyzer (CLD) was used as the analysis equipment. After installing 0.1 ml of the synthesized catalyst in a 3/8-inch reactor, NO (300 ppm), NH ₃ (360 ppm) and O ₂ (5 vol%) using MFC (flow control system) while the mixed gas does not pass through the sample. ) To adjust the gas concentration. In order to maintain the total flow rate at 500 sccm, N ₂ was used as a balanced gas, and when the gas concentration stabilized, the gas passed to the reactor (reactor pass), and the resultant was synthesized by increasing the temperature at intervals of 50℃ from 150℃ to 300℃. The denitration efficiency of the catalyst was evaluated.

Example 3. Evaluation of denitrification efficiency of porous h-BN catalyst according to weight ratio of catalyst components

In the same manner as in Example 2, the denitration efficiency of the porous h-BN catalyst was evaluated according to the weight ratio of the catalyst components. The weight ratio (wt%) of the catalytically active components Mn and Ce and the support h-BN are shown in Table 1 below. In Table 1, BN refers to h-BN prepared according to Example 1, and BNNS (h-Boron Nitride Nano Sheet) is a process of peeling to improve the denitrification efficiency of BN having a thick plate-like structure by overlapping several sheets. It means a thin BN manufactured through

BNNS can be made by making BN thinner by giving ultrasonic waves for 5 hours through a tip sonicator. The thickness is 10-40 nm, and the tip diameter is 7 mm.

Mn Ce BN BNNS

wt% 30 15 - - 30 15 55 - 20 10 70 - 20 10 - 70 10 5 - 85

Comparative Example 1. Preparation of a catalyst containing non-porous hexagonal boron nitride (non-porous h-BN)

Solution1 was prepared by dissolving Mn(NO ₃ ) ₂ ·4H ₂ O, Ce(NO ₃ ) ₂ ·6H ₂ O, which are precursors of catalytically active materials, in ethanol, and solution2 was prepared by dissolving h-BN powder in ethanol. . For dispersion and dissolution of each solution, the solution was stirred for 15 minutes after ultrasonication for 30 minutes, and solution1 was poured into solution2 and stirred for 6 hours in order to support (Mn-Ce) on h-BN, thereby preparing solution3. In order to evaporate the ethanol of solution3, the temperature was maintained at 80℃ for 6 hours.

After that, the catalyst was synthesized by the sol-gel method, heat-treated at 250° C. and sintered in an Ar atmosphere to prepare a catalyst having h-BN with a non-porous surface induced.

Comparative Example 2. Evaluation of denitrification efficiency of non-porous h-BN catalyst

A fixed bed was used as the evaluation equipment, and a chemi-luminescent detection analyzer (CLD) was used as the analysis equipment. After installing 0.1 ml of the synthesized catalyst in a 3/8-inch reactor, NO (300 ppm), NH ₃ (360 ppm) and O ₂ (5 vol%) using MFC (flow control system) while the mixed gas does not pass through the sample. ) To adjust the gas concentration. In order to maintain the total flow rate at 500 sccm, N ₂ was used as a balanced gas, and when the gas concentration was stabilized, the gas was passed to the reactor (reactor pass), and the temperature was increased from 150℃ to 300℃ at 50℃ intervals. The denitration efficiency of the resulting catalyst was evaluated.

<Evaluation and results>

Results 1. Evaluation of denitrification efficiency of porous h-BN and non-porous h-BN catalysts

The denitration efficiency of the catalyst using porous h-BN and non-porous h-BN prepared according to Examples and Comparative Examples as a support was evaluated, and the results are shown in Table 2 and FIG. 2 below.

'(Mn+Ce)/porous-BN' in the following table is a description that refers to a catalyst supported by Mn and Ce, which are catalytically active materials, using porous h-BN as a support. In the following description in the specification,'/' is used to mean that the active material is supported on the support.

The Mn-Ce catalyst composed of only catalytically active material and the catalyst supporting Mn-Ce with non-porous h-BN as a support showed 45 to 56% NOx removal activity at each temperature, but porous h-BN was used as a support. Thus, the Mn-Ce-supported catalyst showed a high NOx removal activity of 77-93% at each temperature.

Therefore, when h-BN having a porous surface was used as a support, it was confirmed that the denitration efficiency was the best.

NOx removal efficiency (%) Temperature (℃) 150 200 250 300 (Mn+Ce) 47 60 62 55 (Mn+Ce)/porous-BN 77 93 90 78 (Mn+Ce)/non-porous-BN 45 61 63 56

Results 2. Evaluation of denitrification efficiency of porous h-BN catalyst according to the weight ratio of catalyst components and thickness of h-BN

BN (h-BN) and BNNS (h-BN Nano Sheet) were used as a support, and catalysts having different weight ratios of the catalytically active material and the support were prepared according to Examples, and then the denitration efficiency was evaluated. The results are shown in Table 3 and FIG. 3 below.

The weight ratio of Mn-Ce is the same, and as a result of confirming the NOx removal activity according to the use of BN or not, about 20 to 35% high denitrification efficiency in the catalyst containing BN was shown.

In addition, as a result of confirming the NOx removal activity of the catalyst using BN as a support and the catalyst synthesized using BNNS as a support under the same Mn-Ce weight ratio condition, the catalyst containing BNNS showed a high denitration efficiency of 3 to 20%. .

In addition, when comparing the denitrification efficiency of a catalyst using BNNS as a support and a catalyst synthesized with only catalytically active material, the weight ratio of Mn-Ce is three times lower than that of a catalyst synthesized with only catalytically active material in the catalyst containing BNNS. And showed similar denitrification efficiency.

Taken together, the above results show that the catalyst containing BN or BNNS has a higher denitrification efficiency than that of the catalyst that does not, and when comparing BN and BNNS, a higher denitration efficiency was confirmed in the catalyst containing BNNS. It was confirmed that the catalyst prepared by containing BN or BNNS exhibited excellent denitrification efficiency even if the weight ratio of the catalytically active material was relatively low.

NOx removal efficiency (%) Temperature (℃) 150 200 250 300 (Mn30+Ce15) 47 60 62 55 (Mn30+Ce15)/BN 77 93 90 78 (Mn20+Ce10)/BN 61 80 83 75 (Mn20+Ce10)/BNNS 81 90 86 72 (Mn10+Ce5)/BNNS 50 64 70 57

Claims (10)

A first step of preparing hexagonal boron nitride nanosheets (BNNS) having a thickness of 10 to 40 nm by applying ultrasonic waves to hexagonal boron nitride and catalytically active materials MnO ₂ and CeO ₂ ;
A second step of forming a mixture by mixing 70 to 85% by weight of the hexagonal boron nitride nanosheets and 15 to 30% by weight of the catalytically active materials MnO ₂ and CeO ₂ ;
A third step of evaporating the solvent from the mixture and synthesizing the catalyst through a sol-gel method; And
A method of manufacturing a low-temperature denitration catalyst comprising a fourth step of heat-treating and sintering the synthesized catalyst at 250°C in an air atmosphere.
The method of claim 1,
The method for producing a denitrification catalyst for low temperature, characterized in that the content ratio of the MnO ₂ and CeO ₂ is 2:1.
The method of claim 1,
The catalyst is characterized in that the NOx removal activity at a temperature of 150 ℃ to 300 ℃ low-temperature denitrification catalyst manufacturing method. delete delete delete delete delete delete delete

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