KR100494542B1 - Method for manufacturing double layer coated Pd only three way catalyst - Google Patents

Abstract

The present invention relates to a method for preparing a palladium tertiary catalyst having a double layer coating structure, and more particularly, using alumina (Al ₂ O ₃ ), cerium oxide (CeO ₂ ), a mixed solution, and the like as an additive. In the process of preparing the secondary and secondary catalyst slurry, cerium oxide and cerium-zirconium compound oxide (CeZr) O ₂ are used together instead of the conventional method of using only cerium oxide, and then prasedium oxide (PrO ₂ ) and the addition, the addition of the mixture solution and reaction after which the metal oxide (a perovskite) of (LaCe) (FeCo) O ₃ and (LaSr) (FeCo) O by giving to the appropriate amount added to a selected one of _three, and the finished catalyst The present invention relates to a method for preparing a palladium tertiary catalyst having a double layer coating structure, which can be manufactured by significantly reducing the amount of expensive palladium, compared to a conventional manufacturing method, while having improved nitrogen oxide removal performance and heat resistance.

Description

Method for manufacturing double layer coated Pd only three way catalyst

The present invention relates to a method for producing a low palladium content three-way catalyst having a double layer coating structure, and more particularly, to a double layer using alumina (Al ₂ O ₃ ), cerium oxide (CeO ₂ ), and a mixed solution as an additive. In the process of preparing the primary and secondary catalyst slurry for coating, instead of the conventional method using only cerium oxide, cerium oxide and cerium-zirconium compound oxide (CeZr) O ₂ are used together, and then prasedium oxide (PrO ₂₎ it has a metal oxide was added, and the addition of the mixture solution and reaction after (a perovskite) of (LaCe) (FeCo) O ₃ and (LaSr) (FeCo) O ₃ of by giving to the appropriate amount added to one selected The present invention relates to a method for preparing a palladium tertiary catalyst having a double layer coating structure, which can reduce the amount of expensive palladium, compared to a conventional manufacturing method, while having improved nitrogen oxide removal performance and heat resistance.

In general, a three way catalyst refers to a catalyst that removes these compounds by simultaneously reacting with hydrocarbon-based compounds, carbon monoxide and nitrogen oxides (NOx), which are harmful components of the exhaust gas, and conventionally, mainly Pt / Rh, Pd / Three-way catalysts of Rh or Pt / Pd / Rh systems have been used.

By the way, the catalyst as described above uses rhodium (Rh) as an element for reducing nitrogen oxides in the exhaust gas, which is problematic in terms of cost and heat resistance.

Thus, palladium ternary catalysts using only palladium (Pd) without rhodium have been known and developed [Korean Patent Registration No. 235029, US Patent No. 6,043,188].

First, the palladium solution is impregnated with alumina (Al ₂ O ₃ ) and then reduced.

Next, cerium oxide (CeO ₂ ) and a mixed solution are added to the reduction product, and then the pH is adjusted to react, and the catalyst is milled to form a slurry.

Then, the ceramic monolith (ceramic monolith) is immersed in the catalyst slurry prepared as described above, dried and calcined to complete the palladium tertiary catalyst.

However, in response to the tightened exhaust gas regulations, in recent years, high performance and high heat resistance of catalysts have been required. Due to the high performance and high heat resistance of these catalysts, the use of precious metals as catalyst materials has increased. The price is gradually rising.

Therefore, it remains a challenge to develop a three-way catalyst production method that can reduce the use of precious metals while reducing nitrogen oxide removal performance and heat resistance of the finished catalyst.

Therefore, the present invention has been invented to solve the above problems, using alumina (Al ₂ O ₃ ), cerium oxide (CeO ₂ ) and a mixed solution as an additive for the primary and secondary coating for the double layer coating In the process of preparing the catalyst slurry, instead of the conventional method using only cerium oxide, cerium oxide and cerium-zirconium compound oxide (Ce.Zr) O ₂ are used together, and then praseodymium oxide (PrO ₂ ) is added, after the addition and reaction of the mixed solution, the metal oxide (a perovskite) of (LaCe) (FeCo) O ₃ and (LaSr) (FeCo) O ₃ of by giving to the appropriate amount added to one selected, the improved nitrogen finished catalyst It is an object of the present invention to provide a method for preparing a palladium tertiary catalyst having a double layer coating structure which can reduce the amount of palladium that is expensive and has an oxide removal performance and heat resistance, compared to a conventional manufacturing method.

Hereinafter, the present invention will be described.

The present invention is to prepare a primary and secondary catalyst slurry using alumina, cerium oxide and mixed solution, and then the primary catalyst slurry is first coated on a ceramic monolith carrier, and the secondary catalyst slurry is coated on the primary In the method of manufacturing a palladium tertiary catalyst having a double-layer coating structure by secondary coating on a ceramic monolith carrier after drying and firing,

The primary catalyst slurry is a mixture of alumina and cerium oxide: cerium-zirconium composite oxide (Ce.Zr) O ₂ in a weight ratio of 15:85 to 30:70, and is 15 to 25 g / l based on the total carrier apparent volume. Praseodymium oxide was added at 2 to 5 g / l based on the total carrier apparent volume, followed by addition of the mixed solution and the reaction (LaCe (FeCo) O ₃ ), which is a metal oxide (perovskite). And (LaSr) (FeCo) O ₃ , by adding from 15 to 25 g / l based on the total volume of the total carrier; The secondary catalyst slurry was prepared by mixing alumina impregnated with a palladium solution with a ratio of cerium oxide: cerium-zirconium composite oxide (Ce.Zr) O ₂ at a weight ratio of 15:85 to 30:70, and the total carrier apparent volume. It is added at 15 to 25g / l with respect to this, Praseodymium oxide is added at 2 to 5g / l with respect to the total carrier apparent volume, and then the metal solution (perovskite) after the addition of the mixed solution and the reaction (LaCe) (FeCo) and with O ₃ and characterized in that made by adding as much as 15 ~ 25g / ℓ with respect to (LaSr) (FeCo) a selected one of O ₃ in the apparent volume of the total carrier.

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

The present invention relates to a method for producing a palladium tertiary catalyst having a double-layer coating structure in which the finished catalyst can be produced by significantly reducing the amount of expensive palladium, compared to a conventional production method, while having improved nitrogen oxide removal performance and heat resistance.

In the three-way catalyst production method of the present invention, among the platinum (Pt), palladium (Pd), and rhodium (Rh) used as the catalyst material, it is excellent in automobile exhaust gas purification effect, and particularly excellent in removing nitrogen oxides and having only excellent heat resistance. A three-way catalyst is prepared and prepared by double coating a ceramic monolith.

That is, in order to manufacture a palladium tertiary catalyst having a double-layer coating structure, a separate first and second catalyst slurry was prepared, and then, the ceramic monolith carrier was immersed in the first catalyst slurry, and then first coated, dried and calcined, The secondary coating is subjected to a process of immersing the primary coated ceramic monolith carrier in a secondary catalyst slurry.

Referring to the step-by-step description of the palladium three-way catalyst production method according to the present invention.

In a first process, bulk cerium oxide (CeO ₂ ) and cerium-zirconium composite oxide (Ce.Zr) O ₂ are added to alumina (Al ₂ O ₃ ), and praseodymium oxide (PrO ₂ ) is added thereto. ) Is added and then a mixed solution is added.

At this time, the cerium oxide (CeO ₂ ) and cerium-zirconium composite oxide (Ce.Zr) O ₂ are mixed and added to each other, in order to induce structural stabilization to improve heat resistance of the catalyst.

Here, the ratio of the cerium oxide (CeO ₂ ): cerium-zirconium composite oxide (Ce.Zr) O ₂ is added in a weight ratio of 15:85 to 30:70, and when it is out of the above range, the heat resistance is improved. There is a problem of insufficient contribution, which is undesirable.

In addition, the mixture of cerium oxide (CeO ₂ ) and cerium-zirconium composite oxide (Ce.Zr) O ₂ is added at 15 to 25 g / l based on the apparent volume of the entire carrier, and out of this addition range, the heat resistance is also improved. It is hard to expect.

The praseodymium oxide (PrO ₂ ) is added in the form of a powder, which stabilizes cerium (Ce) on the catalyst, thereby effectively controlling the adsorption and oxygen storage capacity of carbon monoxide (CO) to effectively remove nitrogen oxides (NOx). .

At this time, the Praseodymium oxide (PrO ₂ ) is added at 2 ~ 5g / ℓ relative to the apparent volume of the entire carrier, when a small amount of less than the above range is less effective in improving the heat resistance and efficiency of nitrogen oxide purification efficiency There is a problem in that the price is increased compared to the effect when added beyond the above range.

The mixed solution is a mixture of barium oxide, lanthanum oxide, acetic acid and water, and barium oxide is 2 to 4 g / l based on the total volume of the carrier, and lanthanum oxide is 0.5 to 2 g / l relative to the apparent volume of the carrier. It is preferable to add in order to improve the heat resistance of alumina and the characteristic of cerium oxide.

In addition, acetic acid is preferably 10 to 20 g / l relative to the apparent volume of the total carrier, and the pH is preferably 4.5 or less for controlling the viscosity in preparing the catalyst slurry for the next coating.

In the second step, the mixture obtained in the first step is milled while controlling the slurry reaction and particle size by a ball mill method, and the fine particles are finely ground so as to have 90% or more of the total particles having a particle size of 7 μm or less.

At this time, when milling the particle size outside the above range there is a problem that the reduction in activity and durability is reduced.

As a result of the milling process, a catalyst slurry having a solid content of 30 to 50% and a viscosity of 200 to 400 cpsi is obtained.

A third step, the first metal oxide in order to improve the removal performance of the nitrogen oxide to the catalyst slurry obtained in the second step (perovskite) is (LaCe) (FeCo) O ₃ and (LaSr) (FeCo) O ₃ of The selected one is added at 15-25 g / l relative to the apparent volume of the total carrier to prepare the final primary catalyst slurry.

In the fourth process, the ceramic monolith carrier is immersed in the primary catalyst slurry prepared through the first to third processes, followed by primary coating, followed by drying and firing.

The coating of the present invention is a double coating method using a segregation effect, by maximizing the efficiency of the catalyst by locating the components in the necessary portion using the compound state having the property of agglomeration with each other, the catalytic performance The effect can be improved.

In other words, in the coating of the present invention, the desired component, which can be in the form of dipping, is coated at a desired position by the method of adding each component and selecting an appropriate starting material of the component.

In addition, the drying process is performed for 2 hours at a temperature of 150 ℃ in a drying furnace, the firing process is carried out for 4 hours at 450 ~ 550 ℃ temperature in an electric furnace.

At this time, when the drying and firing conditions are out of the above range, there is a problem that cracks occur in the coating layer and harmful compounds are formed.

In a fifth process, a palladium (Pd) solution is impregnated into alumina (Al ₂ O ₃ ), and then a process of reducing the same using a thermosetting method is performed.

As an embodiment of the heat-purifying method, the heat-purifying treatment is performed for 3 hours at a temperature of 500 ℃.

In a sixth process, bulk cerium oxide (CeO ₂ ) and cerium-zirconium composite oxide (Ce.Zr) O ₂ are added, and praseodymium (PrO ₂ ) is added thereto, followed by a mixed solution. The process of adding is carried out.

At this time, the cerium oxide (CeO ₂ ) and cerium-zirconium composite oxide (Ce.Zr) O ₂ are mixed and added to each other, in order to induce structural stabilization to improve heat resistance of the catalyst.

Here, the ratio of the cerium oxide (CeO ₂ ): cerium-zirconium composite oxide (Ce.Zr) O ₂ is added in a weight ratio of 15:85 to 30:70, and when it is out of the above range, the heat resistance is improved. There is a problem of insufficient contribution, which is undesirable.

In addition, the mixture of cerium oxide (CeO ₂ ) and cerium-zirconium composite oxide (Ce.Zr) O ₂ is added at 15 to 25 g / l based on the apparent volume of the entire carrier, and out of this addition range, the heat resistance is also improved. It is hard to expect.

The praseodymium oxide (PrO ₂ ) is added in the form of a powder, which stabilizes cerium (Ce) on the catalyst, thereby effectively controlling the adsorption and oxygen storage capacity of carbon monoxide (CO) to effectively remove nitrogen oxides (NOx). .

At this time, the Praseodymium oxide (PrO ₂ ) is added at 2 ~ 5g / ℓ relative to the apparent volume of the entire carrier, when a small amount of less than the above range is less effective in improving the heat resistance and efficiency of nitrogen oxide purification efficiency There is a problem in that the price is increased compared to the effect when added beyond the above range.

The mixed solution is a mixture of barium oxide, lanthanum oxide, acetic acid and water, and barium oxide is 2 to 4 g / l based on the total volume of the carrier, and lanthanum oxide is 0.5 to 2 g / l relative to the apparent volume of the carrier. It is preferable to add in order to improve the heat resistance of alumina and the characteristic of cerium oxide.

In addition, acetic acid is preferably 10 to 20 g / l relative to the apparent volume of the total carrier, and the pH is preferably 4.5 or less for controlling the viscosity in preparing the catalyst slurry for the next coating.

In the seventh step, the mixture obtained in the sixth step is milled while controlling the slurry reaction and particle size by a ball mill method, and the fine particles are finely ground to have 90% or more of the total particles having a particle size of 7 μm or less.

At this time, when milling the particle size outside the above range there is a problem that the reduction in activity and durability is reduced.

As a result of the milling process, a catalyst slurry having a solid content of 30 to 50% and a viscosity of 200 to 400 cpsi is obtained.

The eighth step, the second the (LaCe) (FeCo) O ₃ and (LaSr) 7 step catalyst slurry the metal oxide in order to improve the removal performance of the nitrogen oxide in (a perovskite) obtained in (FeCo) O ₃ of The selected one is added at 15-25 g / l relative to the apparent volume of the total carrier to produce the final secondary catalyst slurry.

In a ninth process, the ceramic monolith carrier first coated in the secondary catalyst slurry prepared through the fifth to eighth processes is immersed in a secondary coating, followed by drying and firing.

The drying process is carried out for 2 hours at a temperature of 150 ℃ in a drying furnace, the firing process is carried out for 4 hours at a temperature of 450 ~ 550 ℃ in an electric furnace.

At this time, when the drying and firing conditions are out of the above range, there is a problem that cracks occur in the coating layer and harmful compounds are formed.

In this way, when the three-way catalyst is prepared according to the manufacturing method of the present invention made of the above-described manufacturing process, the amount of the expensive palladium used while the finished catalyst has improved nitrogen oxide removal performance and heat resistance, It can be greatly reduced.

The low palladium content three-way catalyst production method as described above can be widely used in the production of catalysts for automobile exhaust gas purification and industrial catalysts.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by Examples.

Example

In order to compare with the conventional palladium oxide catalyst using palladium (Pd) at 7.0 g / l relative to the total carrier apparent volume, in this embodiment a double layer using palladium (Pd) at 4.0 g / l relative to the total carrier apparent volume A palladium tertiary catalyst with a coating structure was prepared.

First, in order to prepare a primary catalyst slurry, a mixture of 3.75 g of bulk cerium oxide (CeO ₂ ) and 11.25 g of cerium-zirconium compound oxide (Ce.Zr) O ₂ was _first mixed with 50 g of alumina (Al ₂ O ₃ ). To this was added 3.0 g of praseodymium oxide (PrO ₂ ).

In addition, a solution containing 2.8 g of barium oxide, 0.67 g of lanthanum oxide, 13.5 g of acetic acid, and 187.5 ml of water was added thereto, and the pH was adjusted to 4.2 using acetic acid.

Then, the particle size is milled to 9 μm or less by a ball mill method, and then a metal oxide (perovskite) selected from (LaCe (FeCo) O ₃ and (LaSr) (FeCo) O ₃ is selected. One was added in powder form by 22.5 g / L based on the total volume of the whole carrier, and finally, the final particle size was 40% and the viscosity was 300 cpsi. The primary catalyst slurry of was obtained.

Here, the ceramic monolith carrier was dipped and coated, and then dried in a drying furnace at a temperature of 150 ° C. for 2 hours and calcined in an electric furnace at a temperature of 450 to 550 ° C. for 4 hours.

Next, to prepare a secondary catalyst slurry, first, a solution containing 4.0 g of palladium (Pd) was impregnated into 50 g of alumina (Al ₂ O ₃ ), and then reduced by thermal purification for 3 hours at a temperature of 500 ° C. I was.

Then, 3.75 g of cerium oxide (CeO ₂ ) and 11.25 g of cerium-zirconium composite oxide (Ce.Zr) O ₂ were mixed and added thereto, and 3.0 g of praseodymium (PrO ₂ ) was added thereto.

In addition, a solution containing 2.8 g of barium oxide, 0.67 g of lanthanum oxide, 13.5 g of acetic acid, and 187.5 ml of water was added thereto, and the pH was adjusted to 4.2 using acetic acid.

Then, the particle size is milled to 9 μm or less by a ball mill method, and then a metal oxide (perovskite) selected from (LaCe (FeCo) O ₃ and (LaSr) (FeCo) O ₃ is selected. One was charged in powder form by 17.5 g / L based on the total volume of the total carrier, and finally, the particle size was 7 μm or less, milled to 94% of the total particles, and the final content was 40% solids and 300 cpsi. A secondary catalyst slurry was obtained.

The first coated ceramic monolith carrier was dipped and coated therein, followed by drying for 2 hours at a temperature of 150 ° C. in a drying furnace, and firing at a temperature of 450 to 550 ° C. for 4 hours in an electric furnace, thereby forming a palladium having a double layer coating structure. The three-way catalyst was completed.

Comparative example

In order to compare the palladium (Pd) to the oxidation catalyst of the low palladium content of the present invention using 4.0 g / l of the total carrier apparent volume, in the comparative example, palladium (Pd) was 7.0 g / l of the total carrier apparent volume. The used palladium terpolymer was prepared by a known method.

First, a solution containing 7.0 g of palladium (Pd) was impregnated into 100 g of alumina (Al ₂ O ₃ ), and then hydrazine hydrate (hydrazinehydrate) was added dropwise to 1.66 ml per 1 g of palladium.

Then, 30 g of cerium oxide (CeO ₂ ) was added, and a solution containing 5.6 g of barium oxide, 1.33 g of lanthanum oxide, 27.3 g of acetic acid, and 375 ml of water was added thereto, and the pH was adjusted to 4.2 using acetic acid.

The final catalyst slurry having a solid content of 40% and a viscosity of 300 cpsi was obtained by milling the particle size of 7 µm or less by 94% of the total particles by a ball mill method.

Here, the ceramic monolith carrier was immersed and coated, then dried at a temperature of 150 ° C. for 2 hours in a drying furnace, and calcined at 450 to 550 ° C. for 4 hours in an electric furnace to complete a conventional single layer palladium terpolymer. .

The catalyst prepared according to the above Example and Comparative Example was tested and the results are shown in Table 1 below.

In Table 1, the low temperature activation temperature is a 50% purification temperature means that the lower the measured temperature, the better the purification efficiency of hydrocarbons, carbon monoxide, nitrogen oxides, the three-way characteristic is high to indicate the removal performance of the three components The better the property is.

In addition, 950 degreeC aging is the result of having carried out for 140 hours in the atmosphere of 950 degreeC electric furnace in air | atmosphere.

As a result of the comparative test, as shown in Table 1, the three-way catalyst prepared according to the embodiment of the present invention, despite the significantly reduced palladium content compared to the comparative example prepared, purifying hydrocarbons, carbon monoxide, nitrogen oxides Efficacy and removal performance was found to be superior to the three-way catalyst of the comparative example.

In this way, when the three-way catalyst is produced through the production method of the present invention, the amount of the expensive palladium can be significantly reduced compared to the conventional production method while the finished catalyst has more improved nitrogen oxide removal performance and heat resistance.

As described above, according to the method for preparing a palladium three-way catalyst having a double-layer coating structure according to the present invention, the finished catalyst has a double-layer coating structure that can further improve the catalytic performance, thereby further improving nitrogen oxide removal. Palladium tri-catalyst manufacturing method of the double-layer coating structure according to the present invention has the effect of reducing the amount of expensive palladium used compared to the existing manufacturing method while having the performance and heat resistance, and economical effect of manufacturing cost reduction Can be widely used in the manufacture of catalysts for automobile exhaust gas purification and industrial catalysts.

Claims (1)

After preparing the first and second catalyst slurry using alumina, cerium oxide and the following mixed solution, the first catalyst slurry is first coated on a ceramic monolith carrier, and the second catalyst slurry is first coated after In the method of preparing a palladium tertiary catalyst having a double coating structure by secondary coating on a dried and calcined ceramic monolith carrier, The primary catalyst slurry is a mixture of alumina and cerium oxide: cerium-zirconium composite oxide (Ce.Zr) O ₂ in a weight ratio of 15:85 to 30:70, and is 15 to 25 g / l based on the total carrier apparent volume. Praseodymium oxide was added at a concentration of 2 to 5 g / l based on the total carrier apparent volume, followed by addition of the following mixed solution and the reaction (LaCe) (FeCo), which is a metal oxide (perovskite) Prepared by adding one selected from O ₃ and (LaSr) (FeCo) O _{3 by} 15 to 25 g / l based on the total volume of the total carrier; The secondary catalyst slurry was prepared by mixing alumina impregnated with a palladium solution with a ratio of cerium oxide: cerium-zirconium composite oxide (Ce.Zr) O ₂ at a weight ratio of 15:85 to 30:70, and the total carrier apparent volume. 15 to 25 g / l, and praseodymium oxide was added to 2 to 5 g / l based on the total carrier apparent volume, followed by the addition of the following mixed solution and metal oxide (perovskite) a (LaCe) (FeCo) O ₃ and (LaSr) (FeCo) O against ₃ of the one selected in the apparent volume of the entire carrier 15 ~ 25g / ℓ of palladium double-layer coating structure, characterized in that the addition produced by three won Catalyst preparation method. Mixed solution: A mixed solution containing 2 to 4 g / l of barium oxide, 0.5 to 2 g / l of lanthanum oxide and 10 to 20 g / l of acetic acid