KR102015941B1 - Pt/Pd BINARY CATALYST FOR REMOVING LOW-CONCETRATION GAS - Google Patents

Abstract

The present invention relates to a catalyst for removing gas such as hydrogen, carbon monoxide or methanol at low concentrations at room temperature, and a method for preparing the same, wherein the active metal of the catalyst is composed of a platinum / palladium binary system, and a slurry precursor is prepared during catalyst preparation. And by controlling the reduction process, the particle size of the active metal, the oxidation state of the palladium and the surface exposure rate can be specifically controlled to remove hydrogen and carbon monoxide at low temperatures with relatively low precious metal content. do.

Description

Platinum / Palladium binary catalyst for the removal of low concentration harmful gas and its manufacturing method {Pt / Pd BINARY CATALYST FOR REMOVING LOW-CONCETRATION GAS}

The present invention relates to a catalyst for removing gas at room temperature and a method for producing the same, and more particularly, to a catalyst for removing gas such as hydrogen, carbon monoxide or methanol at low concentration at room temperature, and a method for producing the same.

In general, hydrogen (H ₂ ) is not only generated as a process gas or a by-product of industrial processes such as semiconductor processes, but also due to the recent depletion of fossil fuels, soaring international oil prices and raising safety issues in nuclear power plants to replace them. Increasingly, there is an increasing interest in using hydrogen as an energy source with high calorific value, but since it is spontaneously ignited and explodes under a specific mixing ratio, it needs to be controlled as low as possible to ensure stability. In addition, carbon monoxide (CO) is a kind of colorless and odorless toxic gas, methanol (MeOH) is a toxic substance is converted to formaldehyde when absorbed by the human body is harmful to the human body, so it needs to be effectively removed even at low concentrations.

In order to solve the stability problem of harmful gases such as carbon monoxide or methanol in addition to hydrogen, researches are being conducted in consideration of specificities of various industrial fields, and researches on gas storage and blocking and leakage prevention sensors are mainly made. In recent years, research on a technique for removing gas has been actively conducted. Representative degassing technologies include igniters, thermal recombiners, or catalytic oxidation methods to prevent the damage of explosions. Among them, a gas such as hydrogen is combined with oxygen using a catalyst without a separate energy source. Catalytic oxidation, which is removed by means of removal, is most popular.

However, the technique related to the catalytic oxidation method for removing the gas is a reaction that proceeds when the gas is concentrated above a certain concentration, so that the concentration of hydrogen reaches a high concentration and explodes or harmful gases such as carbon monoxide or methanol There is a limit that can not effectively prevent the risk of causing irreparable harm to the human body concentrated in a high concentration, it has been required to secure a catalyst technology that can control harmful gases such as hydrogen, carbon monoxide or methanol even at a low concentration.

Conventional catalytic oxidation technology that can remove a low concentration of gas at room temperature is disclosed in Korean Patent No. 10-1319064. Patent No. 10-1319064 discloses a method for preparing formaldehyde, carbon monoxide, methanol, and a hydrogen catalyst for removing platinum oxide at room temperature. The catalyst is prepared by coating platinum with a sol state on a carrier and supporting platinum by ultraviolet irradiation. The method is disclosed. However, Patent No. 10-1319064 uses a single catalyst made of platinum as the active metal, and the platinum content is 2.5% by weight, which is relatively expensive, because it contains a relatively large amount of precious metals.

As another example of the conventional catalytic oxidation technique, Patent No. 10-1331391 discloses a palladium / titania catalyst and a method for preparing the same, and a palladium / titania catalyst having a formaldehyde, carbon monoxide, and hydrogen removal ability included in air at room temperature and its preparation A method is disclosed. However, the palladium / titania catalyst according to Patent No. 10-1331391 also shows a hydrogen conversion when the weight part is 2.5, and thus has the same limitation as that of Patent No. 10-1319064.

Accordingly, the present inventors pay close attention to the problems of the techniques for removing the low concentration of gas at room temperature, including the aforementioned Patent Nos. 10-1319064 and 10-1331391, and lower the precious metal content as an active metal. At the same time, intensive studies of catalysts that can effectively control low concentrations of gas at room temperature have led to the present invention.

Patent Registration No. 10-1319064 Patent Registration No. 10-1331391

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a catalyst capable of removing low concentrations of hydrogen and carbon monoxide at room temperature while maintaining a low precious metal content as an active metal and a method for producing the same.

The present inventors, while the active metal of the catalyst is composed of a platinum / palladium binary system, while controlling the production and reduction process of the slurry precursor during the catalyst preparation, the particle size of the active metal, the oxidation state of the palladium and the surface exposure rate The present invention has led to the discovery that by controlling specifically, low concentrations of hydrogen and carbon monoxide can be removed at room temperature while having a relatively low precious metal content. The gist of the present invention based on the recognition of the above-mentioned problem and this knowledge is as follows.

(1) binary active metals of platinum / palladium; And a carrier on which the active metal is supported, wherein the active metal precursor is supported at 0.1 to 1 part by weight based on 100 parts by weight of the carrier.

(2) Platinum precursor is carried at 0.5 or less with respect to 100 parts by weight of the carrier, the palladium precursor is carried at 0.5 or more with respect to 100 parts by weight of the carrier, the low temperature gas for removing the concentration of (1) Palladium catalyst.

(3) The room temperature platinum / palladium catalyst for low concentration gas removal according to (1), wherein an oxidation ratio (Pd ⁰ / Pd _total ) of palladium in the active metal is 35% or more.

(4) The room temperature platinum / palladium catalyst for low concentration gas removal according to (1), wherein the particle size of the active metal is 5 nm or less.

(5) The low-temperature removal platinum / palladium catalyst according to (1), wherein the surface exposure rate of palladium in the active metal is 10% or more by atomic fraction.

(6) The room temperature platinum / palladium catalyst for low concentration gas removal according to (1), wherein the low concentration gas is hydrogen, carbon monoxide or methanol.

(7) preparing a slurry by carrying a carrier in an aqueous solution containing a platinum precursor and a palladium precursor, followed by drying and calcining, wherein the calcining process further includes a reducing process under a reducing gas atmosphere. Room temperature platinum / palladium catalyst production method for low concentration gas removal.

(8) The slurry is prepared by dissolving the platinum precursor and the palladium precursor at the same time in an aqueous solution. Room temperature platinum / palladium catalyst production method for removing the low concentration of gas (7).

(9) The platinum precursor is platinum chloride (PtCl ₄ ), tetra-amine platinum nitrate (Pt (NH ₃ ) ₄ (NO ₃ ) ₂ ), platinum hydroxide (Pt (OH) ₂ ), hydroxyl platinum ((NH ₂ -CH ₂ CH ₂ -OH) ₂ Pt (OH) ₆ ) The method for producing a low-temperature concentration of gas (7) platinum / palladium catalyst production method, characterized in that any one or more selected from.

(10) The palladium precursor is palladium chloride (PdCl2) or palladium nitrate dihydrate (N ₂ O ₆ Pd.2H ₂ O), palladium nitrate hydrate (N ₂ O ₆ Pd.xH ₂ O), palladium hydroxide (Pd Method for producing a room temperature platinum / palladium catalyst for low concentration gas removal of (7), characterized in that any one or more selected from (OH) ₂ ).

(11) The method for producing a low-temperature concentration of platinum / palladium catalyst for the low concentration gas of (7), characterized in that the reduction step, heat treatment for 0.5 ~ 2hr at a temperature of 500 ~ 700 ℃.

(12) A room temperature platinum / palladium catalyst for low concentration gas removal according to any one of (7) to (11).

According to the present invention, the active metal of the catalyst is composed of a platinum / palladium binary system, and the particle size of the active metal, the oxidation state of the palladium, and the surface exposure rate are controlled by controlling the production process and the reduction process of the slurry precursor during catalyst preparation. By specifically controlling the present invention, it is possible to provide a catalyst capable of removing low concentrations of hydrogen and carbon monoxide at room temperature while having a relatively low precious metal content.

1 to 5 is a TEM (Transmission Electron Microscope) photograph of the surface state of the catalyst prepared according to Preparation Example 1 and Comparative Preparation Examples 1 to 4 of the present invention.
6 is a graph showing the results of the TPOR (Temperature Program Oxidation & Reduction) analysis for comparing the hydrogen adsorption capacity of the catalyst prepared according to Preparation Example 1 and Comparative Preparation Examples 1 to 4 of the present invention.
7 and 8 are TEM photographs of the surface state of the catalyst prepared according to Preparation Example 4 and Preparation Example 5 of the present invention.
9 to 12 are graphs showing the results of X-ray Photoelectron Spectroscopy (XPS) analysis to investigate the surface oxidation state of the catalyst prepared according to Preparation Examples 5 to 8 of the present invention.
FIG. 13 is a graph comparing the surface density of Pd ⁰ and the hydrogen concentration removal reaction characteristic of 0.5% of catalysts prepared according to Preparation Examples 5 to 8 of the present invention. FIG.
14 is a graph showing the results of TPOR analysis for comparing the hydrogen adsorption capacity of the catalyst prepared according to Preparation Examples 5 to 8 of the present invention.

Hereinafter, the present invention will be described in detail. The catalyst according to the present invention is a platinum / palladium binary catalyst capable of removing a low concentration of hydrogen, carbon monoxide or methanol (hereinafter referred to as 'low concentration gas') at room temperature while maintaining a low precious metal content as an active metal. The present invention relates to a method for preparing a catalyst, which will be described first.

The catalyst is a binary active metal of platinum / palladium; And a carrier on which the active metal is supported, wherein the precursors of platinum and palladium, which are the active metals, are supported at 0.1 to 1 parts by weight based on 100 parts by weight of the carrier. That is, in the case of a catalyst composed of an active metal of a noble metal series, it is desirable to minimize the amount in terms of cost as long as it can achieve catalytic activity. In the present invention, the active metal is composed of a platinum and palladium binary system, To limit the total content of platinum and palladium for the range of 0.1 to 1 parts by weight, which is at least as compared to the prior art, while minimizing the cost and at the same time characterized in that it has a resolution for the low concentration gas.

In this case, the palladium content of the active metal is preferably higher than the platinum content. The reason for this is that palladium is more advantageous to oxidation than platinum, and palladium is more advantageous than platinum in terms of cost. Specifically, the total amount of the active metal is supported in 0.1 to 1 parts by weight based on 100 parts by weight of the carrier, the platinum precursor is carried in less than 0.5 with respect to 100 parts by weight of the carrier, the palladium precursor is 100 parts by weight of the carrier It is preferable to carry at least 0.5 with respect to.

The carrier is preferably a titania-based carrier as a representative reducing carrier, and the titania-based carrier interacts with the active metals of platinum and palladium during heat treatment at a temperature of 500 ° C. or more under a reducing atmosphere in the catalyst manufacturing process as described below. The shape is changed, and by such a change, particles of fine active metal can be uniformly and highly dispersed in the titania-based carrier.

One of the other characteristics according to the present invention is a factor that can substantially contribute to the decomposition of low concentration gas of less than 1% at room temperature conditions around 25 ℃ through the control of the catalyst production process, the oxidation ratio of the active metal, particle size By selectively controlling the relevant factors, the total content of the active metals is minimized as described above.

Specifically, the oxidation rate (Pd ⁰ / Pd _total ) of palladium in the active metal is preferably 35% or more. In this case, the valence of palladium may be present in zero, divalent and tetravalent species, and the Pd ⁰ Denotes palladium in which the oxidation value is 0, and Pd _total denotes the _total palladium. If the oxidation rate (Pd ⁰ / Pd _total ) of palladium is less than 35%, the oxidation reaction is low. The oxidation ratio (Pd ⁰ / Pd _total ) of palladium may be controlled through a reduction temperature during the catalyst preparation process.

In addition, the active metal is preferably a particle size of 5nm or less. If the particle size of the active metal is more than 5 nm, the reaction activity is low. The particle size of the active metal can be controlled through the order and method of supporting palladium and platinum during the catalyst preparation process.

In addition, the palladium surface exposure rate is preferably 10% or more in atomic ratio. In this case, the surface exposure rate refers to the extent to which palladium is exposed to the surface of the catalyst. If the surface exposure rate is less than 10%, palladium is less exposed to the surface of the catalyst, which is not preferable because of low reaction activity. The surface exposure rate of palladium in the active metal is related to the platinum and palladium loading in the manufacturing process, and can be controlled by adjusting the ratio of the loading.

The catalyst manufacturing method which concerns on this invention is demonstrated. The catalyst is basically prepared by carrying a carrier in an aqueous solution containing an active metal precursor, followed by drying and calcining, and further including a reducing step under a reducing gas atmosphere after the calcining step. It is characterized by controlling the oxidation ratio, particle size and surface exposure rate of the active metal as described above to give the catalyst a resolution for low concentration gas at room temperature conditions.

As an active metal precursor included in the slurry, a platinum precursor and a palladium precursor, each of which is quantified in an amount of 0.1 to 1 parts by weight based on 100 parts by weight of the titania-based carrier, are prepared together and dissolved in an aqueous solution. The reason is that by simultaneously supporting the platinum precursor and the palladium precursor, the active metal is highly dispersed and the heat treatment process can be reduced to a single process.

In this case, the platinum precursor is platinum chloride (PtCl ₄ ), tetra-amine platinum nitrate (Pt (NH ₃ ) ₄ (NO ₃ ) ₂ ), platinum hydroxide (Pt (OH) ₂ ), hydroxyl platinum ((NH ₂ -CH ₂ CH ₂ -OH) ₂ Pt (OH) ₆ ), the palladium precursor is palladium chloride (PdCl 2) or palladium nitrate dihydrate (N ₂ O ₆ Pd.2H ₂ O ), Palladium nitrate hydrate (N ₂ O ₆ Pd.xH ₂ O), palladium hydroxide (Pd (OH) ₂ ) may be any one or more selected, and is not particularly limited.

Next, after mixing the slurry consisting of a platinum precursor and a palladium precursor and a titania carrier, the mixture is stirred and heated using a vacuum evaporator, and then completely removed from the micropores using a dryer. Subsequently, the dried sample is fired in an air atmosphere.

Finally, by performing the additional reduction process carried out by the heat treatment in a reducing gas atmosphere after the firing process as a characteristic process of the present invention, the catalyst production is completed. This reduction process involves controlling the oxidation state of the active metal, ultimately dispersing the active metal to a fine particle size and increasing the oxidation state of the active metal palladium to high Pd ^0. By controlling the ratio, it is to improve the oxidative decomposition at room temperature with respect to the low concentration gas. In general, the noble metal catalyst is known to exhibit excellent reaction activity when the particle size of the active metal is formed small and highly dispersed, and the hydrogen oxidation reaction is best when the oxidation state of palladium is present in the zero state.

Specifically, the heat treatment in the reduction process is preferably carried out for 0.5 to 4 hours at a temperature of 500 ~ 700 ℃. If the heat treatment temperature is less than 500 ℃, there is no interaction between the active metal and titania, which is a carrier, so that the active metal is not highly dispersed. Therefore, the oxidation resolution of the low concentration gas is low. Agglomeration occurs and dispersibility and particle size of the active metal are large, which is undesirable. Similarly, if the heat treatment time is less than 0.5hr, the Pd ⁰ ratio is low. On the contrary, if the heat treatment time is more than 4 hours, the dispersion degree and the particle size of platinum may be large due to the aggregation of the active metal. On the other hand, the reducing atmosphere during the heat treatment may use a gas of 1 to 50% composition containing hydrogen, ammonia, methane and the like.

The catalyst according to the present invention prepared as described above may be provided in powder form, or may be formed in various bulk shapes such as honeycomb, slate or pellet, or plate, fiber, filter or honeycomb of metal or ceramic material. It can be used by coating the surface of the structure.

Hereinafter, the present invention will be described in more detail based on preferred examples and experimental examples of the present invention. However, the technical idea of the present invention is not limited thereto, but may be variously implemented by those skilled in the art.

Preparation Example 1

First, platinum chloride (PtCl ₄ : trade name of Aldrich Chemical Co.), tetra-amine platinum nitrate (Pt (NH ₃ ) ₄ (NO ₃ ) ₂ : trade name of Aldrich Chemical Co.) or hydroxyl platinum ((NH ₂ -CH ₂ CH ₂ -OH) ₂ Pt (OH) ₆ ), platinum hydroxide (Pt (OH) ₂ ) any one of the platinum precursor, palladium chloride (PdCl ₂ ), palladium nitrate dihydrate (N _{2 O 6 Pd · 2H 2 O)} , palladium nitrate hydrate _{(N 2 O 6 Pd · xH} 2 O) or palladium hydroxide (Pd (OH) ₂₎ for any one of a palladium precursor titania carrier 100 parts by weight is selected from 0.5 parts by weight of platinum and 0.5 parts by weight of palladium were dissolved in distilled water at the same time.

Next, the titania (TiO ₂ ) carrier was added to the prepared active metal precursor aqueous solution to prepare a slurry, and then heated under a stirring condition at about 70 ° C. using a vacuum evaporator, and 5 to 30 hours at 80 ° to 120 ° C. Drying to completely remove the moisture contained in the micropores.

Subsequently, when chlorine was contained as a precursor of platinum and palladium, such as platinum chloride or palladium, chlorine was excluded using 30% hydrogen / nitrogen gas at 300 ° C. for 3 hr and calcined under air atmosphere at 400 ° C. for 4 hr. do. On the other hand, when the precursors of platinum and palladium do not contain chlorine, only the firing process was performed under an air atmosphere at 400 ° C. for 4hr.

Finally, the catalyst was prepared by reducing the calcined sample for activation of the catalyst at 600 ° C. for 1 hr in a 30% hydrogen / nitrogen gas atmosphere. In this case, a tubular calciner was used to sufficiently bring the reducing gas into contact with the catalyst, and the sample obtained by this method was screened at 40 to 50 mesh.

Preparation Example 2

A catalyst was prepared in the same manner as in Preparation Example 1, except that the active metals, platinum and palladium, were prepared in a ratio of platinum (0.9): palladium (0.1).

Preparation Example 3

A catalyst was prepared in the same manner as in Preparation Example 1, except that the active metals, platinum and palladium, were prepared in a ratio of platinum (0.7): palladium (0.3).

Preparation Example 4

A catalyst was prepared in the same manner as in Preparation Example 1, except that the active metals, platinum and palladium, were prepared in a ratio of platinum (0.3): palladium (0.7).

Preparation Example 5

A catalyst was prepared in the same manner as in Preparation Example 1, except that the active metals, platinum and palladium, were prepared in a ratio of platinum (0.1): palladium (0.9).

Preparation Example 6

A catalyst was prepared in the same manner as in Preparation Example 5 except that the temperature of the final reduction process was performed at 500 ° C. for 1 hr.

Preparation Example 7

A catalyst was prepared in the same manner as in Preparation Example 5, except that the temperature of the final reduction process was performed at 400 ° C. for 1 hr.

Preparation Example 8

A catalyst was prepared in the same manner as in Preparation Example 5 except that the temperature of the final reduction process was performed at 300 ° C. for 1 hr.

Comparative Production Example 1

First, platinum chloride (PtCl ₄ : trade name of Aldrich Chemical Co.), tetra-amine platinum nitrate (Pt (NH ₃ ) ₄ (NO ₃ ) ₂ : trade name of Aldrich Chemical Co.), hydroxyl platinum ((NH ₂ Platinum precursor selected from any one of -CH ₂ CH ₂ -OH) ₂ Pt (OH) ₆ ) and platinum hydroxide (Pt (OH) ₂ ) was quantified to 1 part by weight based on 100 parts by weight of the titania carrier, Dissolved. In this case, when platinum chloride (PtCl ₄ ) is used as the platinum precursor, the temperature of the distilled water is raised to 60 ° C. to dissolve it.

Next, the platinum precursor aqueous solution was added to the prepared titania carrier and mixed to prepare a slurry, and then stirred and heated at about 70 ° C. using a rotary vacuum evaporator to evaporate moisture, and at least 24hr at a temperature of 80 ° C. to 120 ° C. Drying was completely removed from the water contained in the micropores.

Next, if platinum chloride was used as the platinum precursor, chlorine was removed using 30% hydrogen / nitrogen gas at 300 ° C. for 3hr, and a firing process was performed at 400 ° C. for 4hr under an air atmosphere. On the other hand, when tetra-amine platinum nitrate or hydroxyl platinum containing no chlorine was used as the platinum precursor, only a calcination process was performed under an air atmosphere for 4 hours at a temperature of 400 ° C.

Finally, after the calcination process was completed, the catalyst was prepared by reducing the sample for 1 hr at 600 ° C. in a 30% hydrogen / nitrogen gas atmosphere. In this case, a tubular calciner was used to sufficiently bring the reducing gas into contact with the catalyst, and the sample obtained by this method was sieved through a 40-50 mesh.

Comparative Production Example 2

It was prepared in the same manner as in Comparative Preparation Example 1 except that a catalyst was prepared using the active metal as palladium.

Comparative Production Example 3

First, platinum chloride (PtCl ₄ : trade name of Aldrich Chemical Co.), tetra-amine platinum nitrate (Pt (NH ₃ ) ₄ (NO ₃ ) ₂ : trade name of Aldrich Chemical Co.) or hydroxyl platinum ((NH ₂ Platinum precursor selected from any one of -CH ₂ CH ₂ -OH) ₂ Pt (OH) ₆ ) and platinum hydroxide (Pt (OH) ₂ ) was quantitated at 0.5 parts by weight based on 100 parts by weight of the titania carrier to distilled water at room temperature. Dissolved. In this case, when platinum chloride (PtCl ₄ ) is used as the platinum precursor, the temperature of the distilled water is raised to 60 ° C. to dissolve it.

Next, titania (TiO ₂ ) carrier was added to the prepared platinum precursor aqueous solution to prepare a slurry, and then stirred and heated at about 70 ° C. using a vacuum evaporator to evaporate moisture, and then, 5 to 80 ° C. at 120 ° C. Drying for 30hr to completely remove the water contained in the micropores.

Next, a firing process was performed at 400 ° C. for 4hr in an air atmosphere, and the sample was prepared by reducing the calcined sample for 30 minutes at 300 ° C. using hydrogen / nitrogen gas for activation of the catalyst.

Subsequently, palladium chloride (PdCl ₂ ) or palladium nitrate dihydrate (N ₂ O ₆ Pd.2H ₂ O), palladium nitrate hydrate (N ₂ O ₆ Pd.xH ₂ O), palladium hydroxide (Pd (OH) _The palladium precursor selected from any one of ₂ ) is quantitated at 0.5 part by weight based on 100 parts by weight of the sample in which the reduction process is completed, and dissolved in distilled water at room temperature.

Next, the palladium precursor aqueous solution was added to the prepared sample and mixed with the prepared sample to prepare a slurry form, and then stirred and heated at 70 ° C. using a rotary vacuum evaporator to evaporate moisture, and 24hr at a temperature of 80 to 120 ° C. Dry over to completely remove the moisture contained in the micropores.

Finally, the catalyst was prepared by performing a calcination process under an air atmosphere at 400 ° C. for 4 hr and reducing the calcined sample for 1 hr at 600 ° C. using 30% hydrogen / nitrogen gas for activation of the catalyst. In this case, a tubular calciner was used so that the reducing gas was sufficiently in contact with the catalyst, and the sample obtained by this method was sieved through a 40-50 mesh.

Comparative Production Example 4

The catalyst was prepared in the same manner as in Comparative Preparation Example 4, except that palladium was first supported on tinania and then platinum was supported on palladium / titania prepared above.

The conditions relating to the composition and content of the active metals according to Preparation Examples 1 to 8 and Comparative Preparation Examples 1 to 4, firing and reduction processes are summarized in Table 1 below.

division Active ingredient Active minutes Reduction temperature (℃) Heat treatment condition Preparation Example 1 Platinum-palladium 0.5-0.5 600 Firing (1), Reduction (1) Preparation Example 2 Platinum-palladium 0.9-0.1 600 Firing (1), Reduction (1) Preparation Example 3 Platinum-palladium 0.7-0.3 600 Firing (1), Reduction (1) Preparation Example 4 Platinum-palladium 0.3-0.7 600 Firing (1), Reduction (1) Preparation Example 5 Platinum-palladium 0.1-0.9 600 Firing (1), Reduction (1) Preparation Example 6 Platinum-palladium 0.1-0.9 500 Firing (1), Reduction (1) Preparation Example 7 Platinum-palladium 0.1-0.9 400 Firing (1), Reduction (1) Preparation Example 8 Platinum-palladium 0.1-0.9 300 Firing (1), Reduction (1) Comparative Production Example 1 platinum 1.0 600 Firing (1), Reduction (1) Comparative Production Example 2 Palladium 1.0 600 Firing (1), Reduction (1) Comparative Production Example 3 Palladium / platinum 0.5 / 0.5 600 Firing (2), Reduction (2) Comparative Production Example 4 Platinum / palladium 0.5 / 0.5 600 Firing (2), Reduction (2)

Experimental Example 1

Low concentration room temperature hydrogen oxidation experiment of the catalysts prepared according to Preparation Example 1 and Comparative Preparation Examples 1 to 4 of the present invention was carried out, the results are shown in the following [Table 2]. The experiment was carried out by injecting a mixed gas containing water with a relative humidity of 135% (at 25 ° C) and 0.15 to 1.5 vol.% Of hydrogen and 21 vol.% Of oxygen to a reaction column equipped with a catalyst, and the initial temperature of the reaction was 25 After the reaction was conducted at a space velocity of 60,000 hr ¹ while maintaining the temperature, the composition of the exhaust gas was measured using a hydrogen analyzer (FTC 200 Thermal Conductivity Analyzer, messkonzept Co.) and summarized in Table 2 below.

division H ₂ 1.5% H ₂ 1.0% H ₂ 0.5% H ₂ 0.25% H ₂ 0.15% Preparation Example 1 100 100 80 14.46 0 Comparative Production Example 1 100 4.1 0 0 0 Comparative Production Example 2 100 100 26.4 2.4 0 Comparative Production Example 3 100 96.11 10.74 0 0 Comparative Production Example 4 100 95.91 0 0 0

As a result of the experiment, as shown in Table 2, the room temperature hydrogen oxidation reaction was different according to various active metals and preparation methods. Looking at the results, the catalyst prepared in Preparation Example 1 exhibited a hydrogen conversion rate of 80% or more even at 0.5% hydrogen injection concentration, showing the best room temperature hydrogen oxidation characteristics. Next, room temperature hydrogen oxidation characteristics were shown in order of Comparative Preparation Example 3, Comparative Preparation Example 4, and Comparative Preparation Example 1, including Comparative Preparation Example 2 using only palladium as the active metal. In Comparative Preparation Example 1, which was the catalyst showing the lowest concentration of room temperature hydrogen oxidation, the active metal was composed only of platinum, followed by the catalyst of Comparative Preparation Example 4 having the last supported platinum. Reaction characteristics were shown. In other words, when the above results are summarized, a platinum / palladium binary catalyst prepared by dissolving simultaneously in a platinum and palladium precursor aqueous solution is a single catalyst of platinum or palladium according to Comparative Production Examples 1 and 2, or Comparative Production Example 3 and Compared with the platinum catalyst or the palladium precursor supporting platinum 4 according to 4, it was confirmed that it exhibited excellent room temperature oxidation characteristics for the lowest concentration of hydrogen at least 0.5%, compared to the binary catalyst of platinum / palladium. In the case of the active metal was found to exhibit excellent reaction characteristics when exposed to the catalyst surface as palladium rather than platinum.

Experimental Example 2

In order to confirm the particle size of the active metal in the catalysts according to Preparation Example 1 and Comparative Preparation Examples 1 to 4 of the present invention, a TEM (Transmission Electron Microscope) analysis was performed and the results are shown in FIGS. 1 to 5. In addition, the results of the EDX (Energy Dispersive X-ray) of the catalyst prepared according to Preparation Example 1, Comparative Preparation Example 1, Comparative Preparation Example 4 for the component analysis of the catalytically active metal according to the catalyst preparation method are shown in Table 3 below. It was.

Preparation Example 1 Comparative Production Example 1 Comparative Production Example 4 Element Atomic% Atomic% Atomic% Ti K 20.31 23.21 18.30 Cu K 56.99 58.12 59.23 Pd L 11.88 - 4.31 Pt L 10.83 18.67 18.15

Referring to the results of FIGS. 1, 2, and 5 for each of the catalysts prepared in Preparation Example 1, Comparative Preparation Example 1, and Comparative Preparation Example 4, particles of the active metal of the catalyst were formed to be very small with an average diameter of 5 nm or less. Was confirmed. On the other hand, when looking at the results of Figures 3 and 4 for the catalyst prepared according to Comparative Preparation Example 2, Comparative Preparation Example 3, the particle size of the active metal particles are 5nm or more larger than the catalysts according to the other manufacturing methods It was confirmed that it was formed. In the case of Preparation Example 1, Comparative Preparation Example 1 and Comparative Preparation Example 4, as platinum is finally supported, it is exposed to the surface of the catalyst during heat treatment, so that the interaction between the active metal and titania, a carrier, occurs, resulting in high dispersion of the active metal. do. On the other hand, in the case of Comparative Preparation Example 2 and Comparative Preparation Example 3, the palladium is finally supported, so that the heat-sensitive palladium is more agglomerated than the platinum, resulting in the coagulation of heat-sensitive palladium. As the strength of the interaction between the metal and the support is weak, it is determined that the active metal is not highly dispersed. In general, platinum is known to have a stronger interaction with a support than palladium.

Subsequently, the EDX results according to Preparation Example 1, Comparative Preparation Example 1, and Comparative Preparation Example 4, in which the particle size of the active ingredient of the catalyst was formed, were examined based on Table 3. Although both Pt and Pt were present in a high ratio, the catalysts according to Comparative Preparation Example 1 and Comparative Preparation Example 4 showed a low content of Pd. On the other hand, in Comparative Preparation Example 2 and Comparative Preparation Example 3 the size of the active metal was formed large, the component analysis was unnecessary. Accordingly, combining the results of the TEM and EDX according to Experimental Example 2 and the room temperature hydrogen oxidation characteristics shown in Experimental Example 1, the surface exposure amount of palladium on the surface of the catalyst was more than 10% in atomic fraction, the lowest 0.5%. It was confirmed that it is advantageous in the low-temperature room temperature hydrogen oxidation characteristics, it is confirmed that the platinum is added to the palladium is highly dispersed in a small particle size, the smaller the particle size is formed to 5nm or less, it is advantageous in the low-temperature room temperature hydrogen oxidation characteristics. That is, in the case of room temperature hydrogen oxidation, palladium shows a better reaction activity than platinum, whereas palladium is a material that easily aggregates, and has a disadvantage in that the particle size is large, but in the present invention, when supported with a small amount of platinum, platinum and a support Through the interaction of, it is possible to form a small particle size of palladium.

Experimental Example 3

The hydrogen dissociation adsorption capacity of the catalyst as a physical property value of the catalyst which can substantially contribute to the low concentration room temperature hydrogen oxidation reaction was compared and analyzed in Preparation Examples 1 and Comparative Preparation Examples 1 to 4 according to the present invention. The amount of hydrogen dissociation adsorption of the catalyst was measured using TPOR (Temperature Programmed Oxidation & Redcution, hereinafter “TPRO”) analysis. The TPOR analysis is based on the difference between the hydrogen concentration in the reference gas entering the detector without passing the catalyst and the hydrogen concentration in the reaction gas passing through the catalyst bed and reacting with the catalyst and entering the detector. It is an analysis that measures the amount of hydrogen consumed by comparing. The amount of hydrogen consumed refers to the amount of hydrogen dissociated and adsorbed on the catalyst.

Specifically, 2920 Autochem (Micromeritics) was used, and the detector (detector) for concentration measurement was carried out TPOR analysis using a Thermal Conductivity Detector (TCD). The analysis sequence was prepared according to Preparation Example 1 and Comparative Preparation Examples 1 to 4 and filled with 0.25 g of each catalyst which was pulverized to 100 μm or less, and then flowed up to 120 ° C. while flowing argon (Ar) of 50 cc / min. After the temperature was raised to ℃ / min and maintained for 10 minutes to remove moisture and residual impurities on the surface of the catalyst to activate the catalyst. Thereafter, the temperature was lowered to 30 ° C., and then 1.5 vol.% Oxygen / nitrogen was injected for 10 minutes, and then 5,000 ppm hydrogen / nitrogen was continuously flowed, and the amount of hydrogen consumed using TCD was observed. Shown in

Looking at the results of TPOR shown in Figure 6, it was confirmed that the amount of hydrogen consumed was more catalysts with excellent reaction activity, it was confirmed that the dissociation adsorption amount of hydrogen is closely related to the low concentration of room temperature hydrogen oxidation reaction characteristics. That is, the greater the oxidation rate and surface leakage rate of palladium, the greater the amount of dissociation adsorption.

Experimental Example 4

In order to confirm the correlation between the ratio of platinum and palladium and the normal temperature hydrogen oxidation characteristics of the catalyst in the present invention, room temperature hydrogen oxidation experiments of the catalysts prepared according to Preparation Examples 1 to 4 were carried out. It is shown in Table 4. Experimental conditions were carried out in the same manner as in Experimental Example 1 except that the hydrogen concentration was performed at 0.15 to 1.0 vol.%.

division H ₂ 1.0% H ₂ 0.75% H ₂ 0.5% H ₂ 0.25% H ₂ 0.15% Preparation Example 1 100 100 80 14.46 0 Preparation Example 2 100 100 0 0 0 Preparation Example 3 100 100 65 9 0 Preparation Example 4 100 100 82.38 26.74 0 Preparation Example 5 100 100 92.83 30.07 9.61

As a result, as shown in Table 4, the room temperature hydrogen oxidation reaction was different according to various platinum / palladium ratios. The order of the catalysts showing excellent room temperature hydrogen oxidation characteristics was found in the order of Preparation Example 5, Preparation Example 4, Preparation Example 1, Preparation Example 3, Preparation Example 2, and the surface exposure rate of palladium was increased as the ratio of palladium was increased. It was confirmed that the excellent low-concentration hydrogen oxidation reaction properties appeared, which can correspond to the results of Experimental Example 1.

Experimental Example 5

In order to check the correlation between the platinum and palladium ratio and the particle size and surface exposure rate of the active metal in the present invention, by performing the transmission electron microscopy (TEM) analysis of the catalyst prepared according to Preparation Examples 1, 4 and 5 The results are shown in FIGS. 1, 7 and 8. In addition, the results of EDX (Energy Dispersive X-ray) of the catalyst prepared according to Preparation Example 1, Preparation Examples 4 and 5 for the component analysis of the catalytically active metal according to the catalyst preparation method are shown in Table 5 below.

Preparation Example 1 Preparation Example 4 Preparation Example 5 Element Atomic% Atomic% Atomic% Ti K 20.31 43.96 55.22 Cu K 56.99 37.88 32.9 Pd L 11.88 12.77 11.08 Pt L 10.83 4.39 0.8

Referring to the results of FIGS. 1, 7 and 8 for each of the catalysts prepared in Preparation Example 1, Preparation Example 4 and Preparation Example 5, particles of the active metal of the catalyst were formed to be very small with an average diameter of 5 nm or less. It was confirmed.

Subsequently, when the EDX results according to Preparation Example 1, Preparation Example 4 and Preparation Example 5 were examined based on Table 5, it was confirmed that the higher the amount of the catalyst supported by the preparation of the catalyst, the more the palladium was exposed to the surface of the catalyst. Accordingly, comparing the results of TEM and EDX with the room temperature hydrogen oxidation characteristics shown in Experimental Example 1, it was prepared in the ratio of platinum (0.1) -palladium (0.9), which is largely exposed to a small particle size of palladium on the catalyst surface. It was confirmed that the catalyst of Preparation Example 5 showed the best low concentration hydrogen oxidation characteristics.

Experimental Example 6

In order to investigate the room temperature hydrogen oxidation characteristics of the catalyst prepared according to the reduction process, which is the final heat treatment process, the room temperature hydrogen oxidation characteristics of the catalysts prepared according to Preparation Examples 5 to 8 were tested, and the results are shown in Table 6 below. Indicated. Experimental conditions were carried out in the same manner as in Experiment 4.

division H ₂ 1.0% H ₂ 0.75% H ₂ 0.5% H ₂ 0.25% H ₂ 0.15% Preparation Example 5 100 100 92.83 30.07 9.61 Preparation Example 6 100 91.06 61.45 5.34 0 Preparation Example 7 100 85.86 38.48 5.81 0 Preparation Example 8 100 75.6 15.90 3.16 0

As a result of the experiment, as shown in Table 6, it showed different room temperature hydrogen oxidation characteristics according to various temperature conditions in the reduction process. The order of the catalysts showing the excellent room temperature hydrogen oxidation characteristics was shown in the order of Preparation Example 5, Preparation Example 6, Preparation Example 7, Preparation Example 8, and excellent low concentration as the temperature in the reduction process increased in the 400 ~ 600 ℃ range It was confirmed that the hydrogen oxidation reaction at room temperature.

Experimental Example 7

In order to investigate the oxidation state of palladium, the active metal disclosed in the present invention, as the physical property of the catalyst, the oxidation state of the catalyst prepared according to Preparation Examples 5 to 8 was changed to XPS (VG Scientific Co. trade name ESCALAB 201). The results are shown in FIGS. 9 to 12, and quantitative values are shown in Table 7 below. Referring to FIG 9 to FIG 12, it is possible, depending on the oxidation state of the palladium exposed in the surface of the catalyst confirm that the Pd ⁰ of the peak, Pd ^{+ 2,} and the peak peak of Pd ⁴⁺ appear.

division Palladium oxide Pd ⁰ (atom) Pd ²⁺ + Pd ⁴⁺ (atom) Pd _Total (atom) Pd ⁰ / Pd _Total (%) Preparation Example 5 1522.85 1754.02 3276.87 46.47 Preparation Example 6 1153.11 1708.05 2861.01 40.30 Preparation Example 7 470.69 868.77 1339.46 35.14 Preparation Example 8 658.11 1308.58 1966.69 33.46

In addition, referring to Table 7, it can be seen that as the reduction temperature is increased in the final process, the number of atoms of Pd ⁰ in the catalyst increases, so that the proportion of Pd ⁰ in the total palladium (Pd _Total ) gradually increases. In particular, in the case of the catalyst prepared at a reduction temperature of 500 ° C. or higher according to Preparation Example 5 and Preparation Example 6, it was found that the proportion of Pd ⁰ was 35% or more.

In addition, the correlation between the palladium oxide ratio (Pd ⁰ / Pd _total ) through Experimental Example 7 and the hydrogen oxidation of 0.5 vol.% Of Experimental Example 6 at room temperature hydrogen oxidation reaction is shown in FIG. As a result, as the palladium oxide ratio (Pd ⁰ / Pd _total ) was increased, it was confirmed that the room temperature hydrogen oxidation reaction characteristics were improved.

Experimental Example 8

In order to investigate the hydrogen dissociation adsorption amount of the catalyst prepared according to Preparation Examples 5 to 8 of the present invention, TPOR analysis was performed, and the results are shown in FIG. 14. TPOR measurement was performed in the same manner as in Experiment 3.

Looking at the results of TPOR shown in FIG. 14, it can be seen that the amount of hydrogen consumed increases as the reduction temperature is increased. Accordingly, it was confirmed that the dissociation adsorption amount of hydrogen is increased as the reduction temperature is increased, which is advantageous for low concentration room temperature hydrogen oxidation. That is, the higher the Pd ⁰ ratio of the oxidation value of palladium is, the higher the exposure rate of the palladium, the higher the dissociation adsorption amount.

Experimental Example 9

The carbon monoxide at room temperature oxidation characteristics of the catalysts prepared according to Preparation Example 1 and Comparative Preparation Examples 1 to 2 were tested, and the results are shown in Table 8 below. The experiment was conducted by injecting a mixed gas containing water with a relative humidity of 135% (at 25 ° C) and 500 ppm of carbon monoxide and 21 vol.% Of oxygen into a reaction column equipped with a catalyst, and maintaining the initial temperature of the reaction at 25 ° C. After reacting at a space velocity of 140,000 / hr, the composition of the exhaust gas was measured using a non-dispersive infrared gas analyzer (ZKJ-2, Fuji Electric Co.).

division Carbon Monoxide Removal Rate (%) Preparation Example 1 98 Comparative Production Example 1 100 Comparative Production Example 2 18

As a result, as shown in Table 8, the carbon monoxide at room temperature oxidation reaction was different according to various active metals. Looking at the results, the catalyst prepared in Preparation Example 1 and Comparative Preparation Example 1 exhibited the best carbon monoxide room temperature oxidation characteristics. On the other hand, Comparative Preparation Example 2 catalyst using only palladium as the active metal showed the lowest carbon monoxide oxidation at room temperature. That is, palladium generally shows lower carbon monoxide at room temperature oxidation characteristics than platinum, but the catalyst prepared according to the present invention was found to exhibit excellent carbon monoxide conversion by decreasing the particle size of palladium.

Experimental Example 10

The methanol room temperature oxidation characteristics of the catalysts prepared according to Preparation Example 1 and Comparative Preparation Examples 1 to 2 were tested, and the results are shown in Table 9 below. The experiment was conducted by injecting water with a relative humidity of 135% (at 25 ° C) and 10 ppm / air mixed gas into methanol into a reaction column equipped with a catalyst, and maintaining the initial temperature at 25 ° C at a space velocity of 140,000 / hr. After the composition was measured using a non-dispersive infrared gas analyzer (ZKJ-2, Fuji Electric Co.).

division Methanol Removal Rate (%) Preparation Example 1 33 Comparative Production Example 1 34 Comparative Production Example 2 4

As a result of the experiment, as shown in Table 9, different oxidation of methanol at room temperature was shown according to various active metals. Looking at the results, the catalyst prepared in Preparation Example 1 and Comparative Preparation Example 1 showed the best methanol room temperature oxidation characteristics. On the other hand, Comparative Preparation Example 2 catalyst using only palladium as the active metal showed the lowest methanol room temperature oxidation. That is, in the case of palladium generally shows lower methanol room temperature oxidation characteristics compared to platinum, it was confirmed that the catalyst prepared according to the present invention can exhibit excellent methanol conversion by reducing the particle size of palladium.

Claims (12)

Binary active metals of platinum / palladium; And a carrier on which the active metal is supported,
The active metal precursor is supported by 0.1 to 1 parts by weight based on 100 parts by weight of the carrier, the platinum precursor is carried by 0.5 or less with respect to 100 parts by weight of the carrier, the palladium precursor is carried by 0.5 or more with respect to 100 parts by weight of the carrier ,
Palladium surface exposure rate of the active metal is at least 10% by atomic fraction,
Characterized in that the oxidation ratio (Pd ⁰ / Pd _total ) of palladium in the active metal is 35% or more,
Room temperature platinum / palladium catalyst for low concentration gas removal.
delete delete The room temperature platinum / palladium catalyst of claim 1, wherein the active metal has a particle size of 5 nm or less.
delete The room temperature platinum / palladium catalyst of claim 1, wherein the low concentration gas is hydrogen, carbon monoxide or methanol.
After preparing a slurry by supporting a carrier in an aqueous solution containing a platinum precursor and a palladium precursor, it is prepared through a drying and baking process,
After the firing step further comprises a reducing step under a reducing gas atmosphere,
The slurry is prepared by simultaneously dissolving the platinum precursor and the palladium precursor in an aqueous solution,
Platinum precursor is supported at 0.5 or less with respect to 100 parts by weight of the carrier, palladium precursor is supported at 0.5 or greater with respect to 100 parts by weight of the carrier,
Low-temperature platinum for low concentration gas, characterized in that the palladium surface exposure rate of the active metal is controlled to be 10% or more in atomic fraction and the oxidation rate (Pd ⁰ / Pd _total ) of palladium in the active metal is 35% or more. Palladium catalyst production method.
delete The method of claim 7, wherein the platinum precursor is platinum chloride (PtCl ₄ ), tetra-amine platinum nitrate (Pt (NH ₃ ) ₄ (NO ₃ ) ₂ ), platinum hydroxide (Pt (OH) ₂ ), hydroxyl platinum ((NH ₂ —CH ₂ CH ₂ —OH) ₂ Pt (OH) ₆ ) At least one selected from the group consisting of low-temperature gas for removing a low-temperature platinum / palladium catalyst.
The method of claim 7, wherein the palladium precursor is palladium chloride (PdCl2) or palladium nitrate dihydrate (N ₂ O ₆ Pd. 2H ₂ O), palladium nitrate hydrate (N ₂ O ₆ Pd.xH ₂ O), hydroxide Palladium (Pd (OH) ₂ ) It is at least one selected from the group consisting of low-temperature platinum / palladium catalyst production method.
8. The method of claim 7, wherein the reduction process is performed at a temperature of 500 to 700 ° C. for 0.5 to 2 hours. 9.
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