KR20140042128A - Fabrication method of catalyst-carrier composite powder - Google Patents

Abstract

Provided is a preparation method for a composite powder consisting of a noble metal catalyst and a carrier, which can prevent deterioration in the activity of a noble metal catalyst such as platinum used for an exhaust gas purifier, etc. due to the agglomeration and coarsening of metal at a high temperature, and which can reduce the use of a high-priced catalyst being unnecessarily used, by uniformly dispersing a catalyst only on the surface of a carrier. The composite powder consisting of a noble metal catalyst and a carrier is obtained by: dissolving a precursor substance, which constitutes a noble metal catalyst particle, in a solvent to prepare a precursor solution (S10); dispersing constituents of a carrier in the precursor solution (S20) to prepare a colloidal solution (S30); spray pyrolyzing the colloidal solution to prepare a composite powder (S40); and collecting the composite powder through a filter (S50). A dispersing agent can be further added in the preparation of the colloidal solution so as to disperse the constituents of the carrier in the precursor solution in a desired composition ratio for preparing a stabilized colloid. [Reference numerals] (AA) Dispersant; (S10) Prepare a precursor solution for a noble metal catalyst; (S20) Disperse constituents of a carrier in the precursor solution; (S30) Prepare a colloidal solution; (S40) Spray pyrolyze the colloidal solution; (S50) Collect composite powder

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a catalyst-

The present invention relates to a method for producing a composite powder composed of a noble metal catalyst and a support carrying a catalyst, and more particularly to a method for producing a composite powder composed of a noble metal catalyst and a support, which are used for purification of exhaust gas using spray pyrolysis .

In general, a catalyst must be supported in an exhaust gas purifying apparatus. Conventionally, a porous support such as a washcoat or the like having a wider effective surface area has been used in order to support platinum as a catalyst. When the catalyst is supported by such a washcoat method, the catalyst may be unevenly distributed, or even a part of the catalyst may flocculate, and a large amount of the catalyst may penetrate into the support.

Particularly, in the case of a catalyst for purification of exhaust gas, since the area of the active catalyst is remarkably reduced due to the phenomenon that the platinum catalyst is sintered during use, the amount of excess catalyst It will carry platinum. As a result, the platinum particles are agglomerated or unevenly distributed to deteriorate the catalyst characteristics, and a large amount of the inactive platinum does not act as a catalyst in the wash coat. Moreover, since the platinum powder is a precious metal, the cost increases when an excess amount is added, and development of a technology for replacing or reducing the platinum powder is demanded.

Therefore, a problem to be solved by the present invention is to prevent a noble metal catalyst such as platinum used in an exhaust gas purifying device from being reduced in catalytic property due to a decrease in active specific surface area due to coagulation and coarsening of metal at a high temperature, And a method for producing a noble metal catalyst-support composite powder capable of reducing the amount of expensive catalyst used unnecessarily by dispersing evenly on the surface.

According to another aspect of the present invention, there is provided a process for preparing a noble metal catalyst-support composite powder, comprising the steps of: preparing a precursor solution by dissolving a precursor material constituting noble metal catalyst particles in a solvent; Preparing a solution for this month, spray pyrolyzing the colloidal solution, and collecting the prepared powder as a filter.

The step of preparing the colloidal solution may further include adding a dispersant to disperse the carrier-constituting material in a desired composition to produce a stable colloid. Also, the precursor solution is 0.1 × 1 ^-6 to 1M, and the noble metal catalyst and carrier component may be incorporated in the range of 0.0001 to 10 wt% and 0.1 to 50 wt%, respectively, with respect to the total weight of the solution.

The noble metal catalyst may be at least one selected from the group consisting of Pt, Au, Fe, Cr, Pd, Co, Ag, Rh, ) And ruthenium (Ru), a compound containing the single elements, a mixture of the single element and the compound, or a mixture of a plurality of the compounds, and the nitrate acetate, nitrate, chloride, hydroxide, and oxide, and combinations thereof.

The carrier material may be a metal oxide made of a single element or a composite metal oxide containing the single metal and may be a silicon (Si) based, an aluminum (Al) based, a titanium (Ti) based, Complex oxide, and the size of the noble metal catalyst-support composite powder may be 0.1 to 10 탆.

In a preferred embodiment of the present invention, the precursor of the platinum is at least one selected from the group consisting of chloroplatinic acid hexa hydrate (H ₂ PtCl _{6 6} H ₂ O), platinum acetylacetonate (Pt (acac) ₂ ) chloride (Platinum chloride, PtCl _4), tetraamine platinum (ⅱ) hydroxide hydrate (Tetraammine platinum (ⅱ) hydroxide hydrate , Pt (NH 3) 4 (OH) 2 (H 2 O)), potassium tetrachloro platinum carbonate (Potassuinm tetrachloroplatinate, K ₂ PtCl ₄ ).

According to the method for producing a noble metal catalyst-support composite powder of the present invention, a composite powder in which noble metal catalyst particles are evenly distributed on the surface of a support powder is manufactured using a spray pyrolysis method, It is possible to prevent the deterioration of the catalyst characteristics and reduce the use amount of the expensive noble metal catalyst.

1 is a flow chart showing a process for producing a noble metal catalyst-support composite powder according to the present invention.
2 is a schematic representation of a spray pyrolysis process for preparing a noble metal catalyst-support composite powder according to the present invention.
FIG. 3 is a conceptual view showing a mechanism for synthesizing a composite powder of a noble metal catalyst-support through a spray pyrolysis process according to the present invention.
FIGS. 4A and 4B are views for explaining the application of the noble metal catalyst-support composite powder prepared according to the experimental example of the present invention.
5 is a TEM photograph showing the particle morphology of Pt / SiO ₂ composite powders when the amount of Pt added is increased in the same amount of SiO ₂ produced by the experiment of the present invention.
FIG. 6 is a TEM photograph showing the particle morphology of Pt / SiO ₂ composite powders when the amount of SiO ₂ added is different at the same amount of Pt produced by the experimental example of the present invention.
FIG. 7 is a graph showing the CO conversion of Pt / SiO ₂ composite powders according to the amount of Pt produced according to the experimental example of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments described below can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

In the present invention, the precursor material constituting the noble metal catalyst particles is dissolved in a solvent and the substance constituting the carrier is uniformly dispersed in a solvent to prepare a colloidal solution of the precursor solution by spray pyrolysis to prepare a catalyst-carrier composite powder. A noble metal catalyst such as a platinum used in a purifying device is prevented from deteriorating catalytic activity due to coagulation and coarsening of the metal at a high temperature and the catalyst is uniformly dispersed evenly on the surface of the carrier to reduce the amount of expensive catalyst used unnecessarily The present invention provides a method for producing a noble metal catalyst-support composite powder. To this end, a noble metal catalyst-support composite powder will be described, and then a method for preparing a noble metal catalyst-support composite powder using atomization pyrolysis will be described in detail.

Since the catalyst used in the exhaust gas purifying apparatus is significantly reduced in area of the active catalyst due to sintering at high temperature during use, the catalyst powder adhered to the carrier exhibits minimal deformation characteristics at a high exhaust gas temperature It is very important to synthesize the particles so as not to lose the characteristics of the catalyst. In particular, in the case of the platinum catalyst, since it is a noble metal, it is necessary to avoid excessive use of the catalyst in consideration of deterioration of catalyst characteristics due to coarsening of the catalyst powder under high temperature conditions. For this purpose, it is very important to uniformly disperse the catalyst particles having a small and uniform particle size on the surface of the carrier particles.

Accordingly, in the present invention, a spray pyrolysis process is used to synthesize a noble metal catalyst-support composite powder in which a noble metal catalyst is uniformly dispersed on the surface of a carrier carrying the catalyst. Spray pyrolysis is a process in which a liquid phase method and a gas phase method are applied together. The raw material of a desired composition is dissolved in a solvent such as alcohol or distilled water to form a solution state. Then, using a ultrasonic droplet generating device, And is generated as a droplet. The generated droplets are passed through a furnace along a pipe by a carrier gas, and are dried, pyrolyzed, and crystallized, and synthesized into a single flame. Since the component of the desired composition is uniformly dispersed in the liquid level droplet generated by the ultrasonic droplet generating device, the spray pyrolysis process using the same is a very advantageous process for synthesizing the multi-component powder.

According to this method, finely dispersed particles without aggregation can be obtained, and since the raw material is a solution, each metal component can be uniformly mixed at a desired ratio. In addition, the size or shape of the particles can be controlled by changing the residence time with the concentration of the solution and the control of the reactor temperature and the flow rate of the transporting fluid.

Hereinafter, a method of synthesizing a noble metal catalyst-support composite powder using a pyrolysis step will be described in detail. Here, the noble metal catalyst-support composite powder refers to a hybrid powder in which a noble metal catalyst is adhered to the surface of the support.

1 is a flow chart showing a process for producing a noble metal catalyst-support composite powder according to the present invention.

Referring to FIG. 1, a precursor solution is prepared by dissolving a precursor material constituting noble metal catalyst particles in distilled water or alcohol to prepare a spray solution (S10). Next, a nano powder to be a carrier in the precursor solution, that is, a carrier constituting material is dispersed (S20) to prepare a colloidal solution in which particles are dispersed (S30).

Here, it is preferable that the precursor solution is 0.1 x 1 ^-6 to 1M, and the noble metal catalyst and the carrier component are mixed in the range of 0.0001 to 10 wt% and 0.1 to 50 wt%, respectively, with respect to the total weight of the solution. If the content of the noble metal catalyst is less than the above range, the catalyst can not act as a catalyst due to the insufficient catalytic component. On the other hand, if the noble metal catalyst is larger than the above range, the active area is significantly reduced under high temperature, This is because separation phenomenon occurs. In addition, when the content of the carrier is less than the above range, it can not serve as a carrier. On the other hand, if it is larger than the above range, it may not be dispersed in the solvent or may not be generated as droplets.

The noble metal catalyst may be at least one selected from the group consisting of Pt, Au, Fe, Cr, Pd, Co, Ag, Rh, , A compound containing the single elements, a mixture of the single element and the compound, or a mixture of a plurality of the compounds. In addition, salts and oxides such as acetate, nitrate, chloride, hydroxide and oxide may be used, and these may be used in combination with each other. At this time, the solvent to be used is not particularly limited, but any one selected from C _n H _{2n + 1} OH system, acetone, hexane and water is preferable.

 The material of the carrier may be a metal oxide consisting of a single element or a composite metal oxide including the single metal and may be a silicon (Si), aluminum (Al), titanium (Ti) And a complex oxide.

The colloidal solution may further include various dispersants such as P123 and BYK dispersants in order to disperse the powder constituting the carrier in a solution containing the noble metal catalyst in a desired composition to produce a stable colloid. The colloidal solution thus prepared is sprayed into a fine droplet of several microns in size using a spray pyrolysis apparatus, and the powder is synthesized by spray pyrolysis in various temperatures in the reactor according to the catalyst component of the noble metal (S40).

Generally, when a droplet is generated using a colloidal solution in which particles are dispersed, a droplet having the same composition as that of the original solution is produced. When the powder is produced by the spray pyrolysis process using this droplet, the carrier maintains the form of a spherical porous carrier having a shape similar to the droplet generated by the droplet generating device, and a small amount of noble metal salt is nucleated, Fine catalyst particles are uniformly dispersed on the surface of the carrier. Next, the synthesized powder is collected by a filter to obtain a composite powder in which fine catalyst particles are evenly dispersed on the surface of the support (S50). The composite powder thus prepared has a size of 0.1 to 10 mu m.

2 is a schematic representation of a spray pyrolysis process for preparing a noble metal catalyst-support composite powder according to the present invention.

2, the spray pyrolysis apparatus 100 includes an ultrasound droplet generating device 10, a reactor 20 for drying and pyrolyzing droplets, and a bag filter 30 for collecting particles. The spray solution 2 produced as described in FIG. 1 is continuously supplied to the ultrasonic liquid droplet ejector 10 through the pump 4 and is converted into a fine droplet 6. The converted droplet 6 moves to the reactor 20 along the flow path with a constant flow rate by the flow meter 12 according to the flow rate of the carrier gas 8. At this time, The residence time is determined by the flow rate of the enemy and the temperature inside. The thus synthesized particles are collected in the bag filter 30, and the discharged gases are discharged through the exhaust pipe 40 or the condensed gas is liquefied and collected in the trap 42. [

In addition to the temperature of the reactor 20 in the spray pyrolysis process, the flow rate of the carrier gas 8 and the size of the reactor 20, especially the concentrations of Pt and SiO ₂ as reactants are very important in preparing noble metal catalyst and carrier composite powders It serves as an important variable. This can be an important parameter because it requires a sufficient residence time to allow complete decomposition and nucleation of the noble metal catalyst precursor. In addition, it is a very important parameter because the size of Pt changes depending on the concentration of Pt and SiO ₂ , which can affect the catalyst characteristics.

In the present invention, the droplet generator 10 employs an industrial humidifier operating at a frequency of 1.7 MHz and has a carrier gas 8 for smoothly transporting a large amount of droplets generated by the twenty ultrasonic vibrators into the reactor 20, And the flow rate was maintained at 50 l / min. Here, argon, helium, nitrogen, oxygen and mixed gas may be used as the carrier gas if necessary. In addition, the length of the furnace in the reactor 20 is 800 mm. For this purpose, a quartz tube having a length of 1000 mm and a diameter of 100 mm is used as a reactor, and the temperature of the reactor is maintained at 200 to 1000 ° C. In the above temperature range, the noble metal catalyst precursor materials are decomposed by heating to be converted into fine noble metal catalyst particles and dispersed on the surface of the carrier particles to obtain a composite powder of a noble metal catalyst and a carrier.

FIG. 3 is a conceptual view showing a mechanism for synthesizing a composite powder of a noble metal catalyst-support through a spray pyrolysis process according to the present invention.

As shown in Fig. 3, in the synthesis of the composite powder of the noble metal catalyst and the carrier obtained through the spray pyrolysis process by converting the catalyst precursor solution in which the carrier is dispersed into fine droplets by the ultrasonic droplet generating device, Nucleation occurs almost simultaneously with drying and decomposition of the precursor materials when the gas flow rate is appropriate. The carrier constituents dispersed in the droplets have a spherical shape in the form of a porous body similar to a droplet shape, and a composite powder of a noble metal catalyst and a carrier, in which fine noble metal catalyst particles are uniformly dispersed on the surface of the carrier particles, are synthesized.

FIGS. 4A and 4B are views for explaining the application of the noble metal catalyst-support composite powder prepared according to the experimental example of the present invention. At this time, FIG. 4B further includes a washcoat coated with an oxide or the like to increase the surface area in FIG. 4A.

4A and 4B, the carrier 60 to which the catalyst 62 is adhered is fixed to the base coat 50 or the wash coat 52 on the base material 50. The carrier 60 according to the experimental example of the present invention can spread the active area while minimizing the amount of the catalyst 62 because the catalyst 62 is dispersed only on the surface without penetrating the inside of the carrier 60. In addition, since the fine catalyst 62 is uniformly dispersed in the carrier 60, sintering between the catalysts 62 is prevented, and the area of the catalyst 62 reacted can be maximized.

On the other hand, when a conventional porous carrier is used, a wash coat is formed on a substrate to ensure porosity, then a solution containing a catalyst is applied, followed by drying and calcination. However, in the experimental example of the present invention, the catalyst attached to the carrier can be manufactured more easily than the conventional method by dispersing the carrier particles in the solution containing the catalyst precursor and spraying and decomposing the colloidal solution. In addition, unlike the prior art, since the solution is not applied, the amount of the catalyst wasted without being applied to the carrier can be minimized, and the composite powder having the catalyst particles dispersed on the surface of the porous carrier is adhered to the surface of the wash coat, Can be maximized.

Hereinafter, the present invention will be described in more detail by way of examples. In the experimental example, platinum (Pt) catalyst was used and silicon oxide (SiO ₂ ) was used as a carrier to support the platinum catalyst. The following experimental examples are only examples of the present invention, but the present invention is not limited thereto.

[Experimental Example]

In order to prepare a hybrid composite powder composed of a noble metal catalyst and a carrier, chloroplatinic acid hexahydrate (H ₂ PtCl ₆ 6H ₂ O) was used as the platinum precursor, and as the ceramic powder, dry silica (Fumed Silica, SiO ₂ ) was used. The platinum precursor was dissolved in distilled water, SiO ₂ powder having an average particle size of less than 50 nm was added, and the dispersion was stably dispersed using a tip sonicator for 10 minutes to prepare a colloidal solution. The colloidal solution thus prepared was spray pyrolyzed to prepare Pt / SiO ₂ composite powder. At this time, the length of the heating furnace was 800 mm, the temperature of the reactor was maintained at 500 ° C, and air was used as the carrier gas, and the flow rate was maintained at 50 L / min.

Under the same conditions as above, the amount of support powder SiO ₂ The Pt / SiO ₂ composite powders were prepared by changing the platinum precursor to 0.001, 0.005, 0.02, and 0.1 wt% based on 1 wt% of the total spray solution. Also, each Pt / SiO ₂ composite powder was prepared while fixing the concentration of Pt to 0.01 wt% of the total spray solution and increasing the carrier powder SiO ₂ to 0.5 and 2 wt%.

In addition to the platinum precursor used in the above experiment, chloroplatinic acid hexa hydrate (H ₂ PtCl _{6 6} H ₂ O), platinum acetylacetonate (Pt (acac) ₂ ), platinum chloride (Platinum chloride, PtCl _4), tetraamine platinum (ⅱ) hydroxide hydrate (Tetraammine platinum (ⅱ) hydroxide hydrate , Pt (NH 3) 4 (OH) 2 (H 2 O)), potassium tetrachloro platinum carbonate (Potassuinm tetrachloroplatinate, K ₂ PtCl ₄ ).

FIG. 5 is a TEM photograph showing the particle morphology of Pt / SiO ₂ composite powders according to the Pt addition amount produced by the experimental example of the present invention.

As shown in FIG. 5, when Pt is 0.001% by weight, a very small amount of Pt is added, so that particles can not be identified. However, it can be seen that as the salt of Pt increases from 0.005 to 0.1 wt%, the number of Pt particles increases, and it can be expected that the particles can be coarsened at the time of heat treatment of the particles.

FIG. 6 is a TEM photograph showing the particle morphology of Pt / SiO ₂ composite powders when the addition amount of SiO ₂ is increased at the same Pt addition amount produced by the experimental example of the present invention. Table 1 shows the ratio of Pt / SiO ₂ according to the amount of SiO ₂ and the amount of Pt corresponding to FIG. 6. In this case, four samples were used for the composite powder, and each sample was a, b, c and d. < / RTI >

Sample  a b c d SiO ₂ wt% 0.5 2 2 4 Pt wt% 0.01 0.01 0.02 0.02 Pt / SiO ₂ ratio 2/100 0.5 / 100 1/100 0.5 / 100

6 and Table 1, the Pt concentrations of samples a and b were the same as 0.01 wt%, but SiO ₂ As the amount increases, it can be confirmed that the fine particle size is evenly adhered to the surface of the support due to the increase of the specific surface area where the Pt can be dispersed. This tendency was the same for samples c and d in which the concentration of Pt was equal to 0.02 wt% and the amount of SiO ₂ increased. That is, it was confirmed that the size of the platinum catalyst particle is small, uniform, and uniformly spaced and formed on the surface of the carrier due to the increase of the specific surface area which can be fixed when the carrier concentration is increased even at the same platinum concentration. In addition, when the concentration of the platinum catalyst was doubled at the same carrier concentration, the catalyst particles tended to be concentrated in the characteristic region, and when the total Pt / SiO ₂ ratio was increased, the particle size was similar It was found that some aggregation occurred in the distribution.

Referring to FIGS. 5 and 6, the composite powder prepared in this Experimental Example was prepared by uniformly dispersing platinum catalysts in SiO ₂ , which serves as a carrier, at a certain interval, And it was found that it was attached. In addition, it was found that the platinum catalyst exhibited a uniform particle size distribution and maintained a spherical shape.

FIG. 7 is a graph showing the CO conversion of the Pt / SiO ₂ composite powders shown in FIG. 5. FIG. Here, the carrier powder SiO ₂ used is fixed at 1 wt%, and the CO conversion rate when the loading amount of the platinum catalyst is changed to 0.001, 0.005, 0.02, and 0.1 wt% of the carrier powder is shown. From FIG. 5, it was found that the conversion of CO when the platinum catalyst was supported by 0.005 wt% and that when the platinum catalyst was supported by 0.2 wt% was almost similar. From the above, it can be seen that the noble metal catalyst-support composite powder of the present invention can control the shape of the catalyst particles through the control of the concentration of Pt and SiO ₂ , so that it is possible to synthesize powder exhibiting excellent catalytic properties even when a small amount of catalyst is supported.

As described above, according to the present invention, since the amount of noble metal catalyst particles supported on the surface of the carrier can be controlled, a small amount of noble metal catalyst particles can be evenly dispersed on the surface of the carrier. Accordingly, the amount of catalyst that is unnecessarily consumed as the inactive catalyst particles can be reduced, and the noble metal is not agglomerated even in a high temperature exhaust gas, so that the characteristics of the catalyst can be improved.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but many variations and modifications may be made without departing from the scope of the present invention. It is possible.

2; Spray solution 4; Pump
6; Droplet 8; Carrier gas
10; Ultrasonic droplet ejection 12; Flow meter
20; Heating furnace 30; Bag filter
40; An exhaust pipe 42; traps
50; A substrate 52; Wash coat
60; Carrier 62; catalyst
100; Spray pyrolysis unit

Claims (8)

Dissolving the precursor material constituting the noble metal catalyst particles in a solvent to prepare a precursor solution;
Dispersing the carrier constituent material in the precursor solution to prepare a colloidal solution;
Synthesizing the powder by spray pyrolysis of the colloidal solution; And
Method for producing a noble metal catalyst-carrier composite powder comprising the step of collecting the synthesized powder with a filter. The method of claim 1, wherein the step of preparing the colloidal solution further comprises dispersing the carrier-constituting material in a desired composition to prepare a stable colloid. ≪ / RTI > The method of claim 1, wherein the precursor solution is 0.1 × 1 ^-6 to 1M. ≪ / RTI > The method of claim 1, wherein the noble metal catalyst and the carrier component are incorporated in the range of 0.0001 to 10% by weight and 0.1 to 50% by weight based on the total of the precursor solution, respectively. The method of claim 1, wherein the noble metal catalyst is platinum (Pt), gold (Au), iron (Fe), chromium (Cr), palladium (Pd), cobalt (Co), silver (Ag), rhodium (Rh) and Acetate, which is any one selected from ruthenium (Ru), a single element selected from the group consisting of a single element, a compound including the single elements, a mixture of the single element and the compound, or a mixture consisting of a plurality of the compounds. A method for producing a noble metal catalyst-carrier composite powder, characterized in that any one salt and oxide selected from nitrate, chloride, hydrate, oxide and combinations thereof. The method according to claim 1, wherein the carrier material is a metal oxide consisting of a single element or a composite metal oxide containing the single metal, and is selected from the group consisting of silicon (Si), aluminum (Al) Wherein the noble metal catalyst-support composite powder is one selected from the group consisting of complex oxides containing an element. The method of claim 1, wherein the noble metal catalyst-support composite powder has a size of 0.1 to 10 μm. 6. The method of claim 5, wherein the precursor of platinum is selected from the group consisting of chloroplatinic acid hexa hydrate (H ₂ PtCl _{6 6} H ₂ O), platinum acetylacetonate (Pt (acac) ₂ ), platinum chloride, PtCl _4), tetraamine platinum (ⅱ) hydroxide hydrate (Tetraammine platinum (ⅱ) hydroxide hydrate , Pt (NH 3) 4 (OH) 2 (H 2 O)), potassium tetrachloro platinum carbonate (Potassuinm tetrachloroplatinate , K ₂ PtCl ₄ ). The method for producing a noble metal catalyst-support composite powder according to claim 1,

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