KR102506775B1 - Method for manufacturing exhaust gas purifying catalyst and the exhaust gas purifying catalyst therefrom - Google Patents

Abstract

The present invention relates to a catalyst for purifying exhaust gas, and more particularly, to a catalyst for purifying exhaust gas in which a noble metal catalyst is supported on a support, by aging at a low temperature of less than 100 ° C. A zirconia (ZrO ₂ ) carrier composed of a monoclinic crystal phase and a tetragonal crystal phase is prepared and a palladium metal catalyst is supported thereon to solve the problem of performance and durability deterioration due to changes in the electrochemical properties of the noble metal catalyst. It relates to a method for manufacturing a catalyst for purifying exhaust gas having improved durability and purifying performance of exhaust gas by controlling and solving the electrochemical properties of a noble metal catalyst through action, and a catalyst for purifying exhaust gas formed through the manufacturing method.

Description

Method for manufacturing a catalyst for purification of exhaust gas and a catalyst for purification of exhaust gas formed through the method

The present invention relates to a catalyst for purifying automobile exhaust gas, and more particularly, in a catalyst for purifying exhaust gas in which a noble metal catalyst is supported on a carrier, performance and durability deterioration due to changes in electrochemical properties of the noble metal catalyst are prevented between the carrier and the noble metal. It relates to a manufacturing method of a catalyst for purifying exhaust gas, which improves durability and purifying performance of exhaust gas by controlling electrochemical properties of a noble metal catalyst through interaction, and a catalyst for purifying exhaust gas formed thereby.

Catalysts for purifying automobile exhaust gases are catalysts that convert automobile exhaust pollutants such as hydrocarbons, carbon monoxide and nitrogen oxides into harmless N ₂ , H ₂ and CO ₂ , and these catalysts are generally made of platinum on a porous carrier as the active component of the catalyst. (Pt), rhodium (Rh), palladium (Pd), etc. are supported in the form of precious metals.

Catalysts using palladium (Pb) among noble metals show very excellent performance in purifying carbon monoxide and hydrocarbons, and have the advantage of being cheaper than other precious metals such as platinum. is actively developing

In addition, the porous carrier supporting the precious metal catalyst is a porous oxide support, and generally, a material having excellent thermal stability even at high temperatures and maintaining a high specific surface area is suitable, and Al ₂ O ₃ , SiO ₂ , ZrO ₂ , CeO ₂ and TiO ₂ or their oxide composites are mainly used, and since the absorption-desorption performance of these materials affects the purification efficiency of exhaust gas, increasing the efficacy of these materials is still being pursued.

Zirconia (ZrO ₂ ) used as a porous carrier of an exhaust gas purifying catalyst may exist in three crystal phases, such as monoclinic, tetragonal and cubic, depending on the firing temperature. Specifically, at temperatures below 1100 ° C, the zirconia crystal phase exists as a monoclinic crystal phase, from 1100 ° C to 2300 ° C, the zirconia crystal phase exists as a tetragonal crystal phase, and at a temperature of 2300 ° C, the zirconia melting point is about 2600 It exists in the cubic crystal phase until less than ℃. In the crystal phase of such zirconia (ZrO ₂ ), it is known that the tetragonal and cubic crystal phases have relatively superior physical and chemical properties than the monoclinic crystal phase.

However, as described above, the existing tetragonal crystal phase of zirconia (ZrO ₂ ) uses a method of synthesizing at a high temperature of 1100 ° C or higher, which causes problems in operation cost of the process, standardization of the manufacturing process, and difficulty in mass production. did

Compressed Natural Gas (hereinafter also referred to as 'CNG') engines operating in lean burn atmosphere contain precious metals including platinum (Pt) and palladium (Pd) as catalysts for purifying exhaust gas for CNG vehicles. A catalyst for purifying exhaust gas from compressed natural gas vehicles is applied to oxidize and purify methane, the main component of natural gas.

Specifically, as shown in FIG. 1 _{, the reaction of methane (CH 4 )} in the palladium catalyst supported on the support is as shown in FIG. When approaching from , after bonding to the palladium (Pd) position, the hydrogen (H) atom of the methane molecule is bonded to the oxygen vacancy part of the nearby palladium oxide (PdO). Methane is then converted to PdO to Pd-OH, which is reduced back to Pd.

The conversion reaction between palladium (Pd) and palladium oxide (PdO) is reversible, but this is the case when there is only methane (CH ₄ ) or oxygen (O ₂ ). Due to their interruption, the conversion reaction between palladium (Pd) and palladium oxide (PdO) is not reversible due to the durability of the catalyst, that is, the deactivation of the catalyst. As the mileage of the vehicle increases, the appropriate Pd ⁰ /Pd ^{2 +} ratio required for the reaction cannot be maintained, and Pd ^{2 +} is reduced to Pd ⁰ , resulting in a deterioration in exhaust gas purification performance.

J.N.carstens, S.C. Su, A.T. Bell, J. Catal. 176 (1998) 136. S.C. Su, J.N.carstens, A.T. Bell, J. Catal. 176 (1998) 125.

Therefore, in view of the above problems, the present invention uses zirconia (ZrO ₂ ) composed of a monoclinic crystal phase and a tetragonal crystal phase by aging at a low temperature of less than 1000 ° C. as a carrier in an exhaust gas purification catalyst. A catalyst for purifying exhaust gas that can improve purification performance as well as durability of the catalyst by controlling the electrochemical properties of noble metal (palladium) by the electrochemical interaction between palladium and the carrier by manufacturing a carrier and supporting a palladium catalyst. It is an object of the present invention to provide a manufacturing method and a catalyst for purifying exhaust gas formed through the manufacturing method.

As shown in FIG. 2, the method for producing a catalyst for purifying exhaust gas of the present invention to achieve the above object is to form a precipitate by adding a basic solution to an aqueous solution containing a zirconium precursor and mixing (S110 ), (b) preparing a zirconia (ZrO ₂ ) carrier by aging the precipitate formed in step (a) (S120), (c) washing and drying the prepared zirconia carrier (S130), (d) calcining the dried zirconia carrier (S140), (e) supporting palladium on the zirconia carrier (S150), (f) calcining the exhaust gas purifying catalyst formed by supporting palladium on the zirconia carrier ( S160) may be included.

Steps (a) (S110) and (b) (S120) are steps for preparing a zirconia (ZrO ₂ ) carrier for supporting a palladium catalyst.

First, step (a) is a step of adding a basic solution as a precipitant to an aqueous solution of a zirconium precursor dissolved in distilled water to form a precipitate, and specifically, zirconium oxychloride octahydrate (ZrOCl ₂ 8H ₂ O) as a zirconium precursor Zirconium hydroxide (Zr(OH) ₄ .nH ₂ O) may be formed as a precipitate when a basic solution is added and mixed so that the pH concentration of the aqueous solution of the zirconium precursor dissolved in distilled water is adjusted to 9 to 10. If the pH concentration of the aqueous solution of the zirconium precursor is out of the above range, it precipitates non-uniformly, and some of it remains in an ionic state without precipitating, resulting in a decrease in the productivity of the catalyst and also a decrease in the efficiency of the finally produced catalyst. It is preferable to adjust the concentration so that it is in the range, and it is more preferable that the pH concentration of the zirconium precursor aqueous solution is adjusted to 9.5.

Here, aqueous ammonia (NH ₄ OH) or aqueous sodium hydroxide (NaOH) may be used as the basic solution. The amount of the basic solution is not limited, but may be added to the zirconium precursor aqueous solution until it satisfies the suggested pH concentration.

Next, step (b) (S120) is a step of preparing a zirconia (ZrO ₂ ) carrier having a specific crystal structure by aging the aqueous solution containing the precipitate formed in step (a) under a constant temperature condition.

Specifically, in step (b) (S120), the precipitate, zirconium hydroxide (Zr(OH) ₄ .nH ₂ O), is aged for 48 hours or less at a temperature of 30 ° C or more and less than 70 ° C to form monoclinic (monoclinic) ) A zirconia (ZrO ₂ ) carrier comprising both a crystalline phase and a tetragonal crystalline phase can be prepared.

In the step (b) (S120), if the aging temperature and time are out of the ranges suggested above, the crystal structure of the zirconia (ZrO ₂ ) carrier to be manufactured is not properly generated, so it is preferable to satisfy the ranges suggested above. desirable.

The crystal structure of the zirconia carrier formed through step (b) (S120) preferably includes more than 0 vol% and less than 65 vol% of the tetragonal crystal phase with respect to the total composition of the zirconia carrier, more preferably It is preferable to include more than 0 vol% and less than 15 vol%.

If the content of the tetragonal crystalline phase is 65 vol% or more, the low-temperature methane (CH ₄ ) oxidation activity is rather reduced, so the composition of the tetragonal crystalline phase preferably satisfies the range suggested above.

The step (c) (S130) is a step of washing and drying the prepared zirconia carrier, washing foreign substances such as a basic solution remaining on the surface of the manufactured zirconia carrier with water, and washing the washed zirconia carrier at 50 to 70 ° C. It is a step of drying in less than an hour. Preferably, the drying conditions of the zirconia carrier are preferably dried at 60° C. for 24 hours, but are not limited thereto and can be variously changed by those skilled in the art.

The (d) step (S140) is a step of obtaining a final zirconia carrier by firing the zirconia carrier dried through the (c) step (S130), and is performed by heating the dried zirconia carrier to a high temperature in an air or oxygen atmosphere. can

Specifically, step (d) (S140) is preferably performed at 300 ° C. to 700 ° C. for 2 hours to 10 hours, more preferably at 600 ° C. for 6 hours. If the firing in step (d) (S140) is performed at a temperature of less than 300 ° C, impurities in the zirconia carrier are not sufficiently removed due to the low firing temperature, and at a temperature exceeding 700 ° C, due to an excessively high temperature Since the catalyst particles are sintered and the performance of the catalyst for purifying exhaust gas is deteriorated, it is preferable that the above-mentioned range is satisfied.

The step (e) (S150) is a step of supporting palladium as a precious metal catalyst on a zirconia carrier. An aqueous palladium precursor solution obtained by dissolving a palladium precursor in distilled water may be supported on a zirconia carrier to form a catalyst for purifying exhaust gas, preferably zirconia. A noble metal catalyst may be supported on a carrier so that the content of palladium is 1 wt% based on the weight of the entire exhaust gas purifying catalyst.

The method of supporting the palladium on the zirconia support is not particularly limited, but it can be supported through an impregnation method, precipitation method, deposition method, ion exchange method, etc., and in the step (e), the palladium precursor solution is preferably impregnated. Palladium may be supported on a zirconia carrier having a modified crystal structure.

The palladium precursor is a compound containing palladium (Pd), preferably chloride (PdCl ₂ ), but may be used, but is not necessarily limited thereto, and conventional palladium precursors known in the art to which the present invention pertains may be used without limitation.

In the step (f) (S160), the catalyst for purifying exhaust gas may be calcined at 500° C. to 700° C. for 2 hours to 10 hours, preferably at 600° C. for 6 hours.

In addition, in order to achieve the above object, the catalyst for purifying exhaust gas of the present invention is prepared using the manufacturing method as described above, and the palladium catalyst is supported on a zirconia support, and the crystal structure of the zirconia support is monoclinic (monoclinic). ) It is characterized in that the crystal phase and the tetragonal crystal phase are included together.

It is preferable to include the tetragonal crystal phase in an amount greater than 0 vol% and less than 65 vol% with respect to the total composition of the zirconia carrier.

In addition, as a precious metal catalyst in the catalyst for purifying exhaust gas, the content of palladium relative to the weight of the entire catalyst for purifying exhaust gas may be included as 1 wt%.

The catalyst for purifying exhaust gas of the present invention is preferably used as an exhaust gas catalyst for lean-burn CNG vehicles, but the catalyst for purifying exhaust gas of the present invention is not limited to the above-mentioned application targets, and methane (CH ₄ ) As an oxidation catalyst, it can be applied and used to various catalysts that can be easily performed by those skilled in the art.

According to the method for preparing a catalyst for purifying exhaust gas of the present invention as described above, as a conventional catalyst for purifying exhaust gas, tetragonal crystal phase zirconia (ZrO ₂ ) used as a carrier of a noble metal palladium (Pd) catalyst is used. Unlike a separate firing process at a high temperature of 1100 ° C or higher, zirconia composed of a monoclinic crystal phase and a tetragonal crystal phase by aging at a low temperature of less than 100 ° C as a carrier in an exhaust gas purification catalyst (ZrO ₂ ) Since the support can be prepared by supporting the palladium catalyst on the zirconia support, the operating cost of the process is reduced and the problem of difficult mass production can be solved.

In addition, by preparing a zirconia (ZrO ₂ ) support composed of a monoclinic crystal phase and a tetragonal crystal phase as a support in a catalyst for purification of exhaust gas and supporting a palladium catalyst, the electrochemical interaction between palladium and the support Through the control of the electrochemical properties of the precious metal (palladium), there is an effect of improving the purification performance as well as the durability of the catalyst.

1 is a schematic diagram showing an oxidation reaction process of methane (CH ₄ ) on the surface of a conventional palladium (Pd)-palladium oxidation (PdO) catalyst reaction site.
2 is a flow chart showing a process of a method for preparing a catalyst for purifying exhaust gas according to an example of the present invention.
3 is a graph of X-ray diffraction (XRD) results of a catalyst for purifying exhaust gas prepared according to an embodiment of the present invention.
4A and 4B are scanning electron microscope (SEM) images of a catalyst for purifying exhaust gas manufactured according to an embodiment of the present invention.
5 is a schematic diagram briefly illustrating a method for evaluating purification performance of a catalyst for purifying exhaust gas according to the present invention.
6 is a graph showing the results of light-off temperature (LOT) analysis of a catalyst for purifying exhaust gas in a comparative example.
7 is a graph showing the results of light-off temperature (LOT) analysis of a catalyst for purifying exhaust gas prepared according to an embodiment of the present invention.

Hereinafter, examples and comparative examples of the catalyst for purification of exhaust gas of the present invention will be described in detail, and these examples and comparative examples can be implemented in various different forms by those skilled in the art as an example. Therefore, it is not limited to the embodiment described here.

On the other hand, terms such as “include” or “add” used in this specification should not be construed as necessarily including all of the various components or steps described in the specification, and some of the components or It should be construed that some steps may not be included and may further include additional components or steps.

In addition, the number of repetitions of each step and process conditions described in the manufacturing method of the catalyst for purifying exhaust gas of the present invention are not particularly limited as long as they do not deviate from the object of the present invention.

In Example 1, a zirconium precursor solution was prepared by dissolving zirconium oxychloride octahydrate (ZrOCl ₂ .8H ₂ O) in distilled water as a zirconium precursor, and 28 wt% ammonia water (NH ₄ OH) was added to the zirconium precursor solution, and the pH concentration is adjusted to be 9.5 to form a precipitate, zirconium hydroxide (Zr(OH) ₄ nH ₂ O), and an aqueous solution containing the zirconium hydroxide (Zr(OH) ₄ nH ₂ O) at 30 ° C for 48 hours. During aging, a zirconia (ZrO ₂ ) carrier is prepared. The prepared zirconia carrier is washed, dried at 60° C. for 24 hours, and then calcined at 600° C. for 6 hours. Palladium chloride (PdCl ₂ ) is sufficiently stirred and dissolved in an aqueous solution of 1 M hydrochloric acid to prepare an aqueous palladium precursor solution, which is then impregnated into a zirconia (ZrO ₂ ) carrier so that the palladium content is 1 wt% by an impregnation method, and palladium is impregnated. The resulting zirconium precursor was calcined at 600° C. for 6 hours to prepare a final 1 wt% Pd/ZrO ₂ exhaust gas purifying catalyst.

Example 2 was carried out in the same manner as in Example 1, except that the aging temperature was set at 50° C. to prepare a 1 wt% Pd/ZrO ₂ exhaust gas purifying catalyst.

Example 3 was carried out in the same manner as in Example 1, except that the aging temperature was set at 70° C. to prepare a 1 wt% Pd/ZrO ₂ exhaust gas purifying catalyst.

Example 4 was carried out in the same manner as Example 1, except that the aging temperature condition was 85° C. to prepare a catalyst for purifying exhaust gas of 1 wt% Pd/ZrO ₂ .

Example 5 was carried out in the same manner as Example 1, except that the aging temperature condition was 100° C. to prepare a catalyst for purifying exhaust gas of 1 wt% Pd/ZrO ₂ .

In Comparative Example 1, after dissolving palladium chloride (PdCl ₂ ) in a 1 M hydrochloric acid aqueous solution by stirring sufficiently, it is impregnated into a γ-Al ₂ O ₃ carrier so that the palladium content is 1 wt% by an impregnation method, and palladium is impregnated. The prepared zirconium precursor was calcined at 600° C. for 6 hours to prepare a catalyst for purifying exhaust gas of 1 wt% Pd/γ-Al ₂ O ₃ as a comparative catalyst.

Comparative Example 2 was carried out in the same manner as Comparative Example 1, except that cerium oxide (CeO ₂ ) was used as a carrier, to prepare a catalyst for purifying exhaust gas of 1 wt% Pd/CeO ₂ as a comparative catalyst.

Comparative Example 3 was carried out in the same manner as Comparative Example 1, except that tin oxide (SnO ₂ ) was used as a carrier to prepare a comparative catalyst, 1 wt% Pd/SnO ₂ catalyst for purifying exhaust gas.

Comparative Example 4 was carried out in the same manner as Comparative Example 1, except that magnesium aluminate (MgAl ₂ O ₄ ) was used as a carrier, to prepare a catalyst for purifying exhaust gas of 1 wt% Pd/ MgAl ₂ O ₄ as a comparative catalyst. .

The catalysts for exhaust gas purification prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were measured and evaluated for physical properties and activity of the catalysts by the measurement methods presented in the following experimental examples.

In Experimental Example 1, X-ray diffraction (XRD) analysis of the crystalline phase of the zirconia (ZrO ₂ ) carrier prepared before supporting palladium in Examples 1 to 5 of the present invention was performed, and the result It is shown in Figure 3 and Table 1 below.

division Crystal Size(nm) tetragonal content
(vol %) tetragonal system
(2θ=30.3°) monoclinic system
(2θ=28.2°) ZrO ₂ (30℃) 13.7 21.7 9.0 ZrO ₂ (50℃) 12.4 14.3 10.5 ZrO ₂ (70℃) 10.6 9.6 66.8 ZrO ₂ (85℃) 7.8 - 100 ZrO ₂ (100℃) 6.8 - 100

As seen, as the aging temperature conditions increase, the tetragonal composition content increases in the crystal structure of the zirconia (ZrO ₂ ) carrier, and in particular, Example 4 in which the aging temperature is 85 ° C and 100 ° C In Example 5, it was confirmed that only the tetragonal crystal phase was observed.

Experimental Example 2 is BET of the zirconia (ZrO ₂ ) support prepared before supporting palladium in Examples 1 to 5 of the present invention and the 1 wt% Pd/ZrO ₂ catalyst obtained according to Examples 1 to 5 The specific surface area (S _BET ), pore volume (V _P ), and average pore size (D _P ) were measured and shown in Table 2.

division ZrO ₂ 1 wt % Pd/ZrO ₂ S _BET
(m ² /g) V _P
(cm ³ /g) D _P (nm) S _BET
(m ² /g) V _P
(cm ³ /g) D _P (nm) ZrO ₂ (30℃) 17 0.093 15.0 15 0.091 19.2 ZrO ₂ (50℃) 33 0.131 12.8 29 0.127 14.7 ZrO ₂ (70℃) 71 0.217 10.6 68 0.205 10.6 ZrO ₂ (85℃) 123 0.341 10.5 111 0.331 11.6 ZrO ₂ (100℃) 157 0.386 9.5 148 0.389 10.2

From Table 2, as the aging temperature increases, the diameter of the average pore size of the zirconia (ZrO ₂ ) carrier and the 1 wt% Pd/ZrO ₂ catalyst carrying palladium thereon decreases, resulting in a BET specific surface area and pore volume. increase can be seen.

In addition, the zirconia (ZrO ₂ ) carriers of Examples 1 and 2 were observed through a scanning electron microscope (SEM), and the observed photographs are shown in FIGS. 4a and 4b.

When comparing the particle size of the zirconia carrier of Example 1 observed in FIG. 4a and the zirconia carrier of Example 5 observed in FIG. 4b, the particle size of the zirconia carrier of Example 5 having a relatively high aging temperature is I could see it getting smaller.

Therefore, it was confirmed that the particle size of the zirconia carrier decreased as the aging temperature conditions increased, and the specific surface area of the catalyst increased due to the development of micropores.

Experimental Example 3 relates to catalyst activity evaluation, and as shown in FIG. 5, after filling 0.1 g of the catalyst in powder form prepared in Examples 1 to 5 and Comparative Examples 1 to 4 into a reaction tube, After air flow and pretreatment at 500℃ for 1 hour, a mixture of methane (CH ₄ ), oxygen (O ₂ ), water vapor (H ₂ O), and nitrogen (N ₂ ) was used as the reaction gas at 400 ml/min ( 0.1% CH ₄ : 10% H ₂ O) using MFC (Mass Flow controller) to adjust and supply the flow rate of gas, raise the temperature at a temperature increase rate of 5 ℃ / min, and measure the reaction activity by temperature The oxidation performance of methane (CH ₄ ) was evaluated, and the results are shown in FIGS. 6 and 7 and Tables 3 and 4 below.

In Tables 3 and 4 below, T ₃₀ represents a 30% methane conversion temperature, T ₅₀ represents a 50% methane conversion temperature, and T ₉₀ represents a 90% methane conversion temperature, respectively.

division T _-30
(℃) T _-50
(℃) T _-90
(℃) Comparative Example 1 483.6 501.2 545.5 Comparative Example 2 448.3 469.7 594.1 Comparative Example 3 470.8 511.5 - Comparative Example 4 491.1 514.4 571.4

division T _-30
(℃) T _-50
(℃) T _-90
(℃) Example 1 420.5 439.9 492.7 Example 2 427.8 448.6 499.4 Example 3 455.5 488.7 559.2 Example 4 451.4 480.4 542.7 Example 5 458.9 488.6 540.4

As a result of evaluating the catalytic activity, based on the 50% methane conversion temperature (T ₅₀ ), Examples 1 and 2, in which monoclinic and tetragonal crystal phases were mixed, were composed of only a single tetragonal crystal structure. It was confirmed that methane (CH ₄ ) oxidation activity was better at low temperature compared to zirconia (ZrO ₂ ) carrier, and γ-Al ₂ O ₃ , CeO ₂ , Sn ₂ O ₃ , MgAl ₂ O ₄ of Comparative Examples 1 to 4 It can be seen that the methane oxidation activity is excellent compared to the carriers such as .

According to Non-Patent Documents 1 and 2, when palladium (Pd) exists as metallic palladium (metallic Pd) in the Pd/ZrO ₂ catalyst, the activity is low _. ) has been described as enhancing the oxidation activity. In particular, when a small proportion of metallic Pd is present on the surface of palladium oxide (PdO), the oxidation activity of methane (CH ₄ ) is enhanced, and this is because methane is more easily dissociated and adsorbed to metal palladium than palladium oxide (PdO). is described.

Therefore, it was confirmed from this Example that the electrochemical control of palladium (Pd) supported thereon is possible according to the crystal structure of zirconia (ZrO ₂ ), and the single yarn manufactured by aging at a temperature of 30° C. as in Example 1 It was confirmed that the methane (CH ₄ ) oxidation activity was the most excellent in the zirconia carrier including both the monoclinic and tetragonal crystal phases.

The specific technology discussed above is only a preferred implementation example, and is not limited to the foregoing examples and accompanying drawings. Therefore, various substitutions and changes are possible within the scope not departing from the technical spirit of the present invention.

Claims (14)

(a) forming a precipitate by adding and mixing a basic solution so that the pH concentration of an aqueous solution of a zirconium precursor dissolved in water is adjusted to 9 to 10;
(b) Aging the aqueous solution containing the precipitate formed in step (a) for 48 hours or less at a temperature of 30 ° C or more and less than 70 ° C to change the crystal structure to a monoclinic crystal phase and a tetragonal crystal phase. Preparing a zirconia (ZrO ₂ ) carrier comprising the same;
(c) washing and drying the prepared zirconia carrier;
(d) calcining the zirconia carrier dried in step (c) at 600° C. for 2 to 10 hours;
(e) supporting palladium on the zirconia carrier subjected to step (d); and
(f) calcining a catalyst for purifying exhaust gas formed by supporting palladium on a zirconia support through step (e);
The tetragonal crystal phase is a method for producing a catalyst for purifying exhaust gas, characterized in that it comprises more than 0 vol% and less than 65 vol% with respect to the total composition of the zirconia support. delete delete According to claim 1,
The step (c) is a method for producing a catalyst for purifying exhaust gas, characterized in that for drying the washed zirconia support at 50 to 70 ° C. for 24 hours or less. delete According to claim 1,
In the step (e), an aqueous palladium precursor solution in which the palladium precursor is dissolved in distilled water is supported on a zirconia carrier so that the palladium content is 1 wt%. According to claim 1,
In the step (f), the catalyst for purifying exhaust gas is calcined at 500° C. to 700° C. for 2 to 10 hours. According to claim 1,
The zirconium precursor is a method for producing a catalyst for purifying exhaust gas, characterized in that zirconium oxychloride octahydrate (ZrOCl ₂ · 8H ₂ O). delete According to claim 1,
The basic solution is a method for producing a catalyst for purifying exhaust gas, characterized in that ammonia water (NH ₄ OH) or sodium hydroxide (NaOH) aqueous solution. delete It is manufactured by the manufacturing method of any one of claims 1, 4, 6, 7, 8 and 10, and the crystal structure includes both a monoclinic crystal phase and a tetragonal crystal phase. A catalyst for purifying exhaust gas, characterized in that a palladium catalyst is supported on a zirconia support, and the tetragonal crystal phase comprises more than 0 vol% and less than 65 vol% with respect to the total composition of the zirconia support. delete delete

Images