KR101308496B1 - Methods of manufacturing a honeycomb catalyst - Google Patents

Abstract

In the method for producing a honeycomb catalyst, the catalyst raw material is mixed with a solvent to form a catalyst composition. The catalyst composition is kneaded to form a catalyst clay. The catalyst clay is extruded to form a honeycomb molded body. The honeycomb molded body is coated with a cocatalyst solution containing a tungsten precursor. By coating the expensive promoter after the honeycomb molded body is formed, the production cost can be reduced, and the conversion of sulfur dioxide can be effectively suppressed.

Description

METHODS OF MANUFACTURING A HONEYCOMB CATALYST}

The present invention relates to a process for preparing a catalyst. More specifically, the present invention relates to a method for producing a honeycomb catalyst for use in exhaust gas purification.

Active research is being conducted on methods for removing or purifying NOx contained in exhaust gases generated from automobiles, thermal power plants, chemical plants, and the like. As the above method, a post-treatment technique for removing nitrogen oxides emitted by combustion is mainstream, and in particular, a selective catalyst for removing nitrogen oxides using a denitrification catalyst and a reducing agent such as ammonia (NH ₃ ) or urea (urea) Selective catalytic reduction (SCR) is known to have good efficiency. According to the selective catalytic reduction method, a reduction reaction of nitrogen oxides can be induced and decomposed into nitrogen and water vapor.

As the catalyst used in the selective catalytic reduction method, it is divided into honeycomb form, plate form, corrugate form, etc. according to its form, and according to the raw materials of manufacture, metal oxides, zeolites, Rare earth catalysts and the like. Among them, a honeycomb catalyst capable of securing a large surface area per volume based on titanium dioxide (TiO ₂ ) has been widely commercialized.

As a method for producing a honeycomb catalyst, a method of coating a mixture of an active metal and a carrier such as titanium dioxide and alumina (Al ₂ O ₃ ) as a catalyst material on a metal plate or a ceramic support such as zeolite or cordierite is known.

However, the metal plate or the ceramic support has a problem that the specific surface area is very low and peeling of the coating material may occur.

Another method is to use clay as a support and to coat a mixture of an active metal and a carrier as a catalyst material, but the clay has problems in terms of mechanical or thermal stability.

In addition, as the raw material prices of WO ₃ , V ₂ O ₅ , MnO ₂ , MoO _3, etc., used as active metals increase rapidly, honeycomb catalyst manufacturing costs also increase rapidly. Therefore, there is a need to develop a method for producing an optimized honeycomb catalyst that can minimize the addition of active metal while satisfying a predetermined denitrification efficiency.

It is an object of the present invention to provide a process for producing a honeycomb catalyst which is excellent in denitrification efficiency and cost-effective.

According to the method for producing a honeycomb catalyst according to the embodiments of the present invention to achieve the above object, the catalyst raw material is mixed with a solvent to form a catalyst composition. The catalyst composition is kneaded to form catalyst clay. The catalyst clay is extruded to form a honeycomb molded body. The honeycomb molded body is coated with a cocatalyst solution containing a tungsten precursor.

According to exemplary embodiments, the tungsten precursor may include ammonium meta tungstate, ammonium para tungstate, tungstic acid, and the like.

According to exemplary embodiments, the catalyst raw material may include a support and a catalytically active component.

According to exemplary embodiments, the support may include titanium dioxide, and the catalytically active component may include one or more metals having denitrification activity, oxides of the metals, salts of the metals, and mixtures thereof.

According to exemplary embodiments, examples of the metal include vanadium (V), manganese (Mn), molybdenum (Mo), nickel (Ni), iron (Fe), palladium (Pd), platinum (Pt), Copper (Cu), cobalt (Co), aluminum (Al), etc. are mentioned. These may be used alone or in combination of two or more.

According to exemplary embodiments, ammonium meta vanadate, which is a precursor of vanadium oxide, may be used as the catalytically active component.

According to exemplary embodiments, the catalyst composition may further include an organic binder or an inorganic binder.

According to exemplary embodiments, after forming the catalyst clay, the catalyst clay is filtered using an aluminum mesh. The filtered catalyst cover is aged at constant temperature and humidity conditions.

According to exemplary embodiments, the honeycomb molded body may be coated through a dipping process of immersing and coating a promoter solution.

According to exemplary embodiments, in order to fire the honeycomb molded body coated with the promoter solution, the first firing is performed at a temperature of 300 ° C to 400 ° C. Secondary firing at a temperature of 500 ° C to 650 ° C.

As described above, according to the honeycomb catalyst production method according to the embodiment of the present invention, a catalyst clay comprising a titanium dioxide raw material and an active metal is first formed and extruded to produce a honeycomb molded body. Thereafter, a promoter solution including a tungsten precursor is coated on the honeycomb molded body. Thereby, manufacturing cost can be reduced compared with the case where the catalyst component containing expensive tungsten is thrown in at the time of catalyst discharge or the production of a titanium dioxide raw material. In addition, the cocatalyst solution can be uniformly coated using a dipping coating, so that the conversion of sulfide can be efficiently suppressed, so that the denitrification efficiency can be further improved.

1 is a flowchart illustrating a method for preparing a honeycomb catalyst according to exemplary embodiments of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail a method for producing a nanoparticle according to an embodiment of the present invention. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. In the accompanying drawings, the dimensions of the structures are enlarged to illustrate the present invention in order to clarify the present invention.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, the terms "comprising ", or" having ", and the like, are intended to specify the presence of stated features, integers, steps, operations, elements, or combinations thereof, , Steps, operations, elements, or combinations thereof, as a matter of principle, without departing from the spirit and scope of the invention.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

1 is a flowchart illustrating a method for preparing a honeycomb catalyst according to exemplary embodiments of the present invention.

Referring to FIG. 1, first, a catalyst raw material is mixed with a solvent to form a catalyst composition (S1).

In exemplary embodiments, the catalyst raw material may include a support and a catalytically active component. At this time, an organic or inorganic binder may be added together to improve moldability.

The carrier may be titanium dioxide (TiO ₂ ) powder. Titanium dioxide does not react easily with sulfur compounds, so it can react selectively with nitrogen oxides. In addition, since the pore size and specific surface area in the particles are large, high denitrification efficiency can be exhibited in a wide temperature range of 200 ° C to 500 ° C.

The support may have a weight ratio of 70 to 90% relative to the total weight of the total catalyst raw material. When the content of the carrier is less than 70% by weight, the durability of the honeycomb catalyst may be lowered. When the content of the carrier exceeds 90% by weight, the denitrification efficiency may not be sufficient because the denitrification efficiency does not include a sufficient amount of catalytically active components.

Specifically, the titanium dioxide powder may be prepared by the following process. The following process is illustrative, and the titanium dioxide powder used in the present invention is not necessarily produced by such a process, but may be produced by various other methods.

First, metatitanic acid (TiO (OH) ₂ ) is added to water as a titanium dioxide precursor and washed with water and stirred. In an embodiment, ammonia (NH ₃ ) may be added to the solution in which water washing and stirring are completed, and then stirred again. At this time, the sulfate ions containing a sulfur atom such as (SO ₄ ^2-, sulfate) ions present in the meta-titanic acid, may be the formation of ammonium sulfide (ammonium sulfate) in combination with ammonia.

The ammonium sulfide can then be removed by transferring the solution to a filter press and filtering.

Subsequently, the metatitanic acid in the form of slurry or cake discharged from the filter press is dried using hot air or the like. When the drying is completed, the firing process may be further performed at a higher temperature than when drying. At this time, as the growth of the particles of metatitanic acid occurs, it may be crystallized into titanium dioxide.

Then, the final titanium dioxide powder may be prepared by grinding the slurry or cake containing crystallized titanium dioxide using a roller mill or a jet mill.

The catalytically active component is supported on the support to serve as a main catalyst for removing nitrogen oxides.

The catalytically active component may include metals having catalytic activity, oxides thereof and / or salts thereof. Examples of the metal include vanadium (V), manganese (Mn), molybdenum (Mo), nickel (Ni), iron (Fe), palladium (Pd), platinum (Pt), copper (Cu) and cobalt (Co) ), Aluminum (Al) and the like, but is not necessarily limited thereto. These may be used alone or in combination of two or more.

According to exemplary embodiments, vanadium oxide (V ₂ O ₅ ) may be used as the catalytically active component. Specifically, ammonium metavanadate may be used as a precursor of vanadium oxide.

The catalytically active component may have a content of 0.5 to 3% by weight relative to the total weight of the total catalyst raw material. When the content of the catalytically active component is less than 0.5% by weight, the denitrification efficiency of the honeycomb catalyst may be lowered. When the content of the catalytically active component exceeds 3% by weight, the thermal or mechanical durability of the honeycomb catalyst may be deteriorated, and the conversion rate of SO ₂ gas present in the exhaust gas to SO ₃ may be seriously affected in the denitrification plant. .

The organic or inorganic binder may be added to improve the plasticity and formability of the catalyst soil formed from the catalyst composition and to enhance the strength of the honeycomb.

Examples of the organic binder include hydroxypropoxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyethylene, polypropylene, polyvinyl chloride, polystyrene, and the like. have. These may be used alone or in combination of two or more.

Examples of the inorganic binder include silica-based or alumina-based materials, and one or two or more materials may be mixed and used.

The organic or inorganic binder may be used in a range that does not lower the activity of the honeycomb catalyst. In exemplary embodiments, the organic or inorganic binder may have a content of 10 to 20% by weight relative to the total weight of the catalyst raw material.

Referring back to FIG. 1, the catalyst composition is kneaded to form a catalyst soil (S2).

In exemplary embodiments, the kneading may be performed using a suitable kneader such as a kneader mix. At this time, it is preferable to perform the kneading by repeating several times for homogeneous mixing of the catalyst raw materials. In one embodiment, the kneading may be performed once to twice for about 12 hours.

On the other hand, it is preferable that the water content rate of the said catalyst soil formed after the said kneading process is 20%-35%. When the water content is less than 20%, the catalyst raw materials may not be mixed homogeneously. When the water content is 35% or more, the formability of the catalyst soil may be lowered in a subsequent process.

According to one embodiment, the filtration process and the aging process may be further performed after the catalyst clay is formed.

The filtration process may be performed to remove foreign matter in the catalyst soil. For example, the catalyst cover may be introduced into a strainer, and an aluminum mesh may be attached to the end of the strainer to remove foreign substances and at the same time, to make the catalyst cover more uniform.

The aging process can be carried out to further improve the homogeneity of the catalyst cover and to remove internal stresses in the cover. For example, the filtration process may be stored in a aging chamber in a constant temperature and constant humidity in a plastic container containing the catalyst tops. According to one embodiment, the aging process may be carried out at a temperature of about 10 ℃ to 60 ℃ for a aging time of 1 to 5 days.

Referring back to FIG. 1, the catalyst clay is extruded to form a honeycomb (S3).

According to exemplary embodiments, the honeycomb molded body may be formed by injecting the catalyst clay into a vacuum extruder equipped with a honeycomb die at an end thereof and passing the die through linear motion.

The vacuum extruder may include a screw for linearly moving the catalyst soil, and may include a deceleration part for adjusting a moving speed of the catalyst soil.

In one embodiment, an additional aging process may be further performed on the extruded honeycomb molded body. By the aging process, the catalyst soil is extruded and the stresses received can be eliminated, and thus, warping or cracking of the honeycomb molded body can be prevented. The aging process may be performed for about 1 day to 5 days under constant temperature and humidity conditions of about 30 ℃ to 60 ℃.

The honeycomb molded body further aged may be further subjected to a drying process using hot air. By the drying process, the water content of the honeycomb molded body may drop to about 5% or less.

The honeycomb molded body according to the exemplary embodiments of the present invention has been described above, but is not necessarily limited thereto. That is, the honeycomb molded body can be manufactured through various other application methods.

Subsequently, the cocatalyst solution is coated on the honeycomb molded body (S4).

The promoter solution is coated to inhibit the conversion of sulfur dioxide (SO 2) into sulfur trioxide (SO 3) or other sulfur compounds present in the exhaust gas. The produced sulfur trioxide (SO3) reacts with water vapor in the exhaust gas to produce highly corrosive sulfuric acid to corrode the denitrification plant, or react with unreacted ammonia (NH3) to form ammonium sulfate or ammonium bisulfate (Ammonium). Bi-sulfate) forms and deposits in the pores of the catalyst, causing the problem of lowering the efficiency of the catalyst and increasing the differential pressure in the denitrification plant. Accordingly, it is necessary to uniformly coat the honeycomb molded body with a cocatalyst for suppressing sulfur compound conversion.

Tungsten oxide can be used as said promoter. In exemplary embodiments, a cocatalyst solution for coating tungsten oxide on the honeycomb catalyst body may be prepared by mixing a tungsten precursor in a solvent.

Examples of the tungsten precursor include ammonium meta tungstate, ammonium para tungstate, tungstic acid and the like. These may be used alone or in combination of two or more.

The solvent may be appropriately selected as one capable of dissolving the tungsten precursor, and a basic solvent such as an alkoxide solvent or an amine solvent may be used.

The promoter solution may comprise a tungsten precursor in a weight ratio of about 3 to 10% by weight of the total. When the content of the tungsten precursor is less than 3% by weight, the conversion rate of sulfur dioxide (SO2) into sulfur trioxide (SO3) in the exhaust gas may be increased, and when it exceeds 10% by weight, it is uneconomical and may hinder the activity of the main catalyst. have.

In order to coat the promoter solution, a dipping process may be performed. That is, the co-catalyst solution may be coated on the honeycomb catalyst body by immersing the prepared honeycomb molded body in the cocatalyst solution twice to four times for about 10 minutes to 30 minutes, respectively.

In the case of coating the promoter solution by spray coating, shower coating, bar coating, etc. instead of the dipping process, it is uniform to the inside of the honeycomb molded body including a plurality of fine cells. Can not be coated.

In addition, according to the dipping step, the composition solution can penetrate not only the surface of the honeycomb molded body but also the inside thereof.

According to the exemplary embodiments as described above, after forming a catalyst cover comprising the support and the catalytically active component as the main catalyst, the honeycomb molded body is manufactured by extrusion molding. Thereafter, a promoter solution including a tungsten precursor is coated on the honeycomb molded body.

Unlike the embodiment of the present invention, a large amount of tungsten precursor or tungsten oxide may be consumed when tungsten precursor or tungsten oxide is added to form titanium dioxide powder (or titania) or when added to form catalytic soil. There is nothing else. As a result, the cost of preparing the honeycomb catalyst increases rapidly. In particular, as raw material prices of rare metals such as transition metals soar in recent years, this may be a more serious problem.

In addition, when the tungsten precursor or tungsten oxide is added during titania or catalytic soil formation, the component distribution of tungsten oxide may not be uniform throughout the honeycomb catalyst.

However, according to exemplary embodiments of the present invention, after the honeycomb molded body is first formed by using the catalytic clay, the catalyst solution containing the tungsten precursor is coated, thereby preventing unnecessary waste of raw materials and cost-effectively the honeycomb catalyst. Can produce The dipping process also allows the tungsten oxide to be uniformly coated throughout the honeycomb catalyst.

According to an embodiment, the honeycomb molded body coated with the promoter solution may be dried using hot air or the like. Through this, aggregation of tungsten precursor on the honeycomb molded body can be prevented. The drying process may be performed for 4 to 5 hours at a temperature of about 30 to 90 ℃.

In one embodiment, the cocatalyst solution coating and drying process may be performed repeatedly two to five times for a more sufficient and uniform coating.

Referring back to FIG. 1, the honeycomb molded body coated with the promoter solution is further calcined to produce a final honeycomb catalyst (S5).

By the firing process, the moisture contained in the honeycomb molded body is finally removed, and the metal and the promoter metal of the active ingredient as the main catalyst can be oxidized.

According to exemplary embodiments, the firing may be performed at a temperature of 300 ° C. to 650 ° C. for about 1 to 3 hours using a tunnel type firing furnace. According to one embodiment, after the first firing for 1 to 2 hours at a temperature of 300 ℃ to 400 ℃, the secondary firing may be performed for about 1 hour at a temperature of 500 ℃ to 650 ℃.

The honeycomb catalyst prepared by the above process can be commercialized by sizing or modularizing.

Hereinafter, the present invention will be described in more detail through specific examples and comparative examples.

Example

1) Preparation of Honeycomb Molded Body

As active ingredient 1.0% by weight of ammonium metavanadate relative to the weight of the catalyst raw material was mixed in a solvent together with 25 kg of the titanium dioxide raw material. Thereafter, an alumina-silica-based inorganic binder was added, and then a catalyst clay was prepared by kneading. A filtration process through an aluminum mesh was carried out to remove foreign substances and homogenize the catalyst soil, and then aged at 40 ° C. for about 2 days under constant temperature and humidity conditions. A honeycomb molded body having a length of 5 cm in length * 5 cm in length * 10 cm in length was prepared by using a vacuum extruder. The honeycomb molded body was aged for 4 days in a constant temperature and humidity atmosphere and then dried using hot air.

2) Preparation of Cocatalyst Solution

As a tungsten precursor, ammonium metatungstate was added at a weight ratio of 10% to 200 g of an amine solvent, followed by stirring for about 5 minutes to prepare a cocatalyst solution.

3) Promoter solution coating

The dried honeycomb molded body was coated by repeatedly immersing the honeycomb solution prepared in the above two times for 10 minutes using the Dip coating equipment. After the coated honeycomb molded body is taken out of the coating vessel, compressed air is evenly dispersed using compressed air. Thereafter, the honeycomb molded body was dried at 30 ° C. for 3 hours, and then dried at 90 ° C. for 2 hours. The coating and drying were repeated three times so that the promoter solution could be sufficiently uniformly coated on the surface of the honeycomb molded body. After the honeycomb molded body was dried, the honeycomb molded body was heated by heating up to 300 ° C. at 2 ° C. per minute and then calcining for 2 hours.

Meanwhile, the honeycomb catalyst was pulverized to make a powder for a comparative experiment with the following comparative example, and 6 g of the powder and 1 g of the binder were mixed to prepare a disk-shaped sample.

Comparative example

Comparative samples in the form of discs were prepared by mixing 6 g of the powder and 1 g of the binder as in the above example using a commercially available and commercially available denitrification honeycomb catalyst.

The surface of the honeycomb catalyst prepared or used in Examples and Comparative Examples, and the composition ratio in the bulk state of the sample and the comparative sample produced by grinding it are shown in Table 1 below.

[Table 1]

Denitrification Efficiency of Honeycomb Catalyst

After the honeycomb catalysts of Examples and Comparative Examples were installed in the center of the reactor of the small activity evaluation device, the denitrification conversion efficiency was measured over a gas surface speed of 25 m / h and a reaction temperature of 200 ° C to 450 ° C. Gases introduced into the reactor include nitrogen monoxide (NO), ammonia (NH ₃ ), sulfur dioxide (SO ₂ ), nitrogen, oxygen, moisture and the like. The concentrations of nitrogen monoxide, ammonia and sulfur dioxide were adjusted to 300 ppm, 300 ppm and 500 ppm, respectively.

According to the reaction temperature, the measured denitrification efficiency (%) measurement results are shown in Table 2 below.

[Table 2]

Referring to Table 2, both honeycomb catalysts of Examples and Comparative Examples exhibited high denitrification efficiency of 90% or more in the temperature range of 250 ° C to 400 ° C.

Measurement of sulfur dioxide (SO2) conversion rate in exhaust gas

After the honeycomb catalysts of Examples and Comparative Examples were installed in the center of the reactor of the small activity evaluation device, sulfur dioxide, nitrogen monoxide, nitrogen, and oxygen were introduced for 12 hours at a gas surface velocity of 10 m / h and a reaction temperature of 380 ° C. Water was injected and the conversion of sulfur dioxide was measured. In the case of the honeycomb catalyst according to the embodiment, the conversion rate of sulfur dioxide was measured to be low as 0.2%, while the honeycomb catalyst of the comparative example was measured to be relatively high as 0.73%.

That is, in the case of the embodiment in which the honeycomb molded body is first formed and then dipped in a promoter solution containing a tungsten precursor, the promoter is coated uniformly over the surface and the inside of the honeycomb catalyst to efficiently convert the sulfur compound. It can be seen that. On the other hand, in the case of the comparative example in which the tungsten precursor is injected when forming the titanium dioxide raw material or when forming the catalyst soil, the distribution of the sulfur compound is measured to be higher because the distribution of tungsten oxide is uneven than that of the example.

In other words, it can be seen that the Example showed a higher sulfur compound conversion inhibiting effect despite using less tungsten precursor than the comparative example (the composition ratio of WO ₃ is lower).

As described above, according to the present invention, since the co-catalyst component containing expensive tungsten is coated on the honeycomb molded body prepared first, the manufacturing cost can be reduced compared to when the cocatalyst is added during the production of catalytic clay or titanium dioxide raw material. have. In addition, it is possible to efficiently suppress the conversion of sulfur dioxide because the cocatalyst solution is uniformly coated using a dipping coating, thereby improving the performance of the denitrification catalyst and the life of the denitrification equipment.

Honeycomb catalysts prepared according to exemplary embodiments of the present invention can be widely used as selective reduction catalysts for removing nitrogen oxides in exhaust gases generated in automobiles, power plants, chemical plants, and the like.

Claims (10)

Mixing the catalyst raw material with a solvent to form a catalyst composition;
Kneading the catalyst composition to form catalyst clay;
Filtering the catalyst cover using an aluminum mesh;
Aging the filtered catalyst cover at constant temperature and humidity conditions;
Extruding the matured catalytic clay to form a honeycomb molded body; And
Method of producing a honeycomb catalyst comprising the step of coating the honeycomb molded body with a cocatalyst solution containing a tungsten precursor. The method of claim 1, wherein the tungsten precursor comprises at least one selected from the group consisting of ammonium meta tungstate, ammonium para tungstate and tungstic acid. Method for producing honeycomb catalyst. The method for producing a honeycomb catalyst according to claim 1, wherein the catalyst raw material includes a support and a catalytically active component. The method of claim 3, wherein the carrier comprises titanium dioxide,
Wherein said catalytically active component is selected from the group consisting of one or more metals having denitrification activity, oxides of said metals, salts of said metals, and mixtures thereof. The method of claim 4, wherein the metal is vanadium (V), manganese (Mn), molybdenum (Mo), nickel (Ni), iron (Fe), palladium (Pd), platinum (Pt), copper (Cu), A method for producing a honeycomb catalyst, characterized in that it comprises at least one selected from the group consisting of cobalt (Co) and aluminum (Al). The method for producing a honeycomb catalyst according to claim 4, wherein ammonium meta vanadate, which is a precursor of vanadium oxide, is used as the catalytically active component. The method of claim 1, wherein the catalyst composition further comprises an organic binder or an inorganic binder. delete The method of claim 1, wherein the coating of the honeycomb molded body with the cocatalyst solution is performed through a dipping process of dipping and coating the honeycomb molded body in the cocatalyst solution. . The method of claim 1, further comprising, after the coating of the honeycomb molded body with the promoter solution, firing the honeycomb molded body coated with the promoter solution,
Firing the honeycomb molded body coated with the promoter solution,
Primary firing at a temperature of 300 ° C. to 400 ° C .; And
Method for producing a honeycomb catalyst comprising the step of secondary firing at a temperature of 500 ℃ to 650 ℃.

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