KR100488779B1 - Method for manufacturing low precious metal loading Pd only three way catalyst - Google Patents

Abstract

The present invention relates to a method for producing a low palladium content three-way catalyst, and more particularly, a palladium (Pd) solution is impregnated in alumina (Al ₂ O ₃ ) and then reduced and added thereto to cerium oxide (CeO ₂ ) and placer oxide. In the process of adding and reacting Odium (PrO ₂ ) and a mixed solution and then milling it, a cerium oxide and cerium-zirconium composite oxide (Ce.Zr) O ₂ is substituted instead of the conventional method of using only cerium oxide. together, and the mixed solution was added and reaction by giving to after the metal oxide is added the appropriate amount of (a perovskite) of (LaCe) (FeCo) O ₃ and (LaSr) (FeCo) O ₃ selected one of, the finished catalyst The present invention relates to a method for producing a low palladium content three-way catalyst having sufficient nitrogen oxide removal performance and heat resistance, which can be produced by greatly reducing an expensive palladium content as compared to a conventional method.

Description

Method for manufacturing low precious metal loading Pd only three way catalyst

The present invention relates to a method for producing a low palladium content three-way catalyst, and more particularly, a palladium (Pd) solution is impregnated in alumina (Al ₂ O ₃ ) and then reduced and added thereto to cerium oxide (CeO ₂ ) and placer oxide. In the process of adding and reacting Odium (PrO ₂ ) and a mixed solution and then milling it, a cerium oxide and cerium-zirconium composite oxide (Ce.Zr) O ₂ is substituted instead of the conventional method of using only cerium oxide. together, and the above mixed solution was added and the reaction since the metal oxide (a perovskite) of (LaCe) (FeCo) O ₃ and (LaSr) (FeCo) O ₃ an appropriate amount was added to a selected one of the by giving, finished catalyst The present invention relates to a method for producing a low palladium content three-way catalyst having sufficient nitrogen oxide removal performance and heat resistance, which can be produced by greatly reducing an expensive palladium content as compared to a conventional method.

In general, a three way catalyst used to remove pollutants such as nitrogen oxides means a catalyst that reacts with hydrocarbon-based compounds, carbon monoxide and nitrogen oxides (NOx), which are harmful components of exhaust gas, to remove these compounds. For example, Pt / Rh, Pd / Rh or Pt / Pd / Rh based ternary catalysts 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. After adding cerium oxide and a mixed solution and then adjusting the pH to react, milling it to form a coating slurry, and coating it with ceramic monolith, drying and calcining palladium Complete the three-way catalyst.

However, in response to the tightening exhaust gas regulations, in recent years, high performance of catalysts has been required, and as the performance of such catalysts is required, the use of precious metals as a catalyst material has increased, and thus the price of catalysts has continuously increased. It is a situation that is urgently required to take measures.

Therefore, the present invention has been invented to solve the above problems, the palladium (Pd) solution is impregnated with alumina (Al ₂ O ₃ ) and then reduced and added thereto cerium oxide (CeO ₂ ), praseodymium oxide In the process of adding (PrO ₂ ) and a mixed solution, and then milling it to prepare a catalyst slurry, cerium oxide and cerium-zirconium composite oxide (CeZr) O ₂ are used together instead of the conventional method of using only cerium oxide. and the mixed solution was added and the reaction after 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 _3, a sufficient nitrogen finished catalyst It is an object of the present invention to provide a low palladium content three-way catalyst production method that can be produced by reducing the expensive palladium content compared to the existing production method while having oxide removal performance and heat resistance.

In the present invention, a palladium (Pd) solution is impregnated with alumina (Al ₂ O ₃ ) and then reduced, and reacted by adding cerium oxide (CeO ₂ ), praseodymium oxide (PrO ₂ ), and a mixed solution. In the method of preparing a catalyst slurry by milling, the catalyst slurry is coated on a ceramic monolith carrier to produce a palladium terpolymer.

After the reduction, the use ratio of cerium oxide: cerium-zirconium composite oxide (Ce.Zr) O ₂ was mixed at a weight ratio of 15:85 to 30:70, and added at 30 to 40 g / l based on the total carrier apparent volume. Praseodymium oxide is added in an amount of 5 to 7 g / l based on the total carrier apparent volume, and after addition and reaction of the mixed solution, (LaCe (FeCo) O ₃ and (LaSr) ( FeCo) O _{3 It} is characterized in that the addition of 40 to 45g / L relative to the apparent volume of the entire carrier.

Hereinafter, the present invention as described above in more detail.

The present invention relates to a low palladium content three-way catalyst production method that can be produced by reducing the expensive palladium content compared to the conventional production method while having a sufficient nitrogen oxide removal performance and heat resistance.

Referring to the step-by-step description of the method for producing a low palladium three-way catalyst according to the present invention.

In a first process, a palladium solution is impregnated into alumina (Al ₂ O ₃ ), and then a process of reducing it is performed. The reduction process is carried out by dropwise addition of hydrazine hydrate (hydrazinehydrate) to 1.66ml per 1g of palladium.

In a second 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 mixing thereto. The process of adding the solution 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. In addition, the cerium oxide (CeO ₂ ): cerium-zirconium composite oxide (Ce.Zr) O ₂ is added by mixing in a weight ratio of 15:85 to 30:70, and if it is outside the above range, the degree of contribution to improving heat resistance is It is not desirable because there is insufficient problem. In addition, the cerium oxide (CeO ₂ ) and cerium-zirconium compound oxide (Ce.Zr) O ₂ are added in an amount of 30 to 40 g / l based on the apparent volume of the entire carrier. Difficult to do

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 to 5 ~ 7g / ℓ relative to the apparent volume of the entire carrier, if a small amount of less than the above range is a problem that the effect of improving the heat resistance and nitrogen oxide purification efficiency is less There is a problem in that the price is increased compared to the effect of adding over the above range.

The mixed solution is a mixture of barium oxide, lanthanum oxide, acetic acid and water, and barium oxide is 5 to 6 g / l based on the total volume of the carrier, and lanthanum oxide is 1 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 23.5 to 33.5 g / l based on the pH 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 third process, the mixture obtained in the second process is milled while controlling the slurry reaction and particle size by the 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.

A fourth step, the second the (LaCe) (FeCo) O ₃ and (LaSr) the metal oxide (a perovskite), in order to improve the removal performance of the nitrogen oxide to the catalyst slurry obtained in the third step (FeCo) O ₃ of The selected catalyst is added by 40 to 45 g / l relative to the apparent volume of the total carrier to prepare the final catalyst slurry.

In a fifth process, a ceramic monolith carrier is immersed in the catalyst slurry, coated, dried and calcined. At this time, the coating is a single coating using a segregation effect, which is generally a double coating in order to place any component in a desired position, but using a compound state having a property of agglomeration with each other By locating the components in the required portion can maximize the efficiency of the single coating, it is an effect that can improve the catalytic performance. In other words, the desired component, which may be in the form of dipping, is coated at the desired position by the method of dosing each component during the coating 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 this way, if the three-way catalyst is prepared through the above-described manufacturing process, the finished catalyst can have a significant nitrogen oxide removal performance and heat resistance, while reducing the expensive palladium content as compared with the conventional manufacturing process.

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

A solution containing 4.0 g of palladium (Pd) was impregnated into 100 g of alumina (Al ₂ O ₃ ), and then reduced by dropwise addition of hydrazine hydrate to 1.66 mL per 1 g of palladium. Then, 7.5 g of cerium oxide (CeO ₂ ) and 22.5 g of cerium-zirconium composite oxide (Ce.Zr) O ₂ were mixed and added thereto, and 6.0 g of praseodymium (PrO ₂ ) was added thereto. In addition, 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. 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 put in powder form by 45 g / l based on the total volume of the total carrier, and finally, the catalyst slurry was milled to have a particle size of 7 μm or less and 94% of all particles, thereby obtaining a catalyst slurry having a solid content of 40% and viscosity of 300 cpsi. Got it. The ceramic monolith carrier was immersed and coated therein, dried at a temperature of 150 ° C. for 2 hours in a drying furnace, and calcined at 450-550 ° C. in an electric furnace for 4 hours to complete the palladium terpolymer.

Comparative example

A solution containing 7.0 g of palladium (Pd) was impregnated into 100 g of alumina (Al ₂ O ₃ ), and then reduced by dropwise addition of hydrazine hydrate 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. The ceramic monolith carrier was immersed and coated therein, dried at a temperature of 150 ° C. for 2 hours in a drying furnace, and calcined at 450-550 ° C. in an electric furnace for 4 hours to complete the 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 almost the same level as 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 expensive catalyst can significantly reduce the expensive palladium content compared with the conventional production method while having sufficient nitrogen oxide removal performance and heat resistance.

As described above, according to the method for preparing a low palladium content three-way catalyst according to the present invention, the finished catalyst can be prepared by significantly reducing the expensive palladium content as compared to the conventional production method while having sufficient nitrogen oxide removal performance and heat resistance. Due to the economical effect of the production cost savings, the three-way catalyst manufacturing method of the low palladium content according to the present invention can be widely used in the production of catalysts for automobile exhaust gas purification, industrial catalysts and the like.

Claims (1)

The palladium (Pd) solution is impregnated with alumina (Al ₂ O ₃ ) and then reduced, followed by cerium oxide (CeO ₂ ) and praseodymium oxide (PrO ₂ ), and barium oxide 5-6 g / l, oxidation After reacting by adding a mixed solution containing lanthanum at a concentration of 1 to 2 g / l and acetic acid at 23.5 to 33.5 g / l, and then milling to prepare a catalyst slurry, the catalyst slurry is coated on a ceramic monolith carrier to coat a palladium tertiary catalyst. In the method for producing After the reduction, the use ratio of cerium oxide: cerium-zirconium composite oxide (Ce.Zr) O ₂ was mixed at a weight ratio of 15:85 to 30:70, and added at 30 to 40 g / l based on the total carrier apparent volume. Praseodymium oxide is added in an amount of 5 to 7 g / l based on the total carrier apparent volume, and after addition and reaction of the mixed solution, (LaCe (FeCo) O ₃ and (LaSr) ( A method for producing a low palladium content three-way catalyst, characterized in that the selected one of FeCo) O ₃ is added by 40 to 45g / l relative to the apparent volume of the entire carrier.