阅读说明：本技术 一种三效催化剂及其制备方法和应用 (Three-way catalyst and preparation method and application thereof ) 是由 宋锡滨 邢晶 刘洪升 潘光军 于 2019-09-09 设计创作，主要内容包括：本申请公开了一种三效催化剂及其制备方法和应用,属于吸附催化剂材料领域。该用于CO氧化反应的三效催化剂包括负载贵金属的铈锆复合氧化铝,所述三效催化剂中贵金属含量为0.5wt％-1.5wt％,所述铈锆复合氧化铝包括铈锆固溶体和γ-Al<Sub>2</Sub>O<Sub>3</Sub>,所述铈锆复合氧化铝中的γ-Al<Sub>2</Sub>O<Sub>3</Sub>的含量为20wt％-50wt％,所述铈锆固溶体包括20wt％-50wt％CeO<Sub>2</Sub>和38wt％-65wt％ZrO<Sub>2</Sub>；所述贵金属选自铂、铑和钯中的至少一种。该三效催化剂催化氧化CO的温度低、储氧量大、优异的抗老化性能和高温稳定性好。(The application discloses a three-way catalyst, a preparation method and application thereof, and belongs to the field of adsorption catalyst materials. The three-way catalyst for CO oxidation reaction comprises cerium-zirconium composite alumina loaded with noble metal, wherein the noble metal content in the three-way catalyst is 0.5-1.5 wt%, and the cerium-zirconium composite alumina comprises cerium-zirconium solid solution and gamma-Al 2 O 3 gamma-Al in the cerium-zirconium composite alumina 2 O 3 The content of (A) is 20 wt% -50 wt%, and the cerium-zirconium solid solution comprises 20 wt% -50 wt% of CeO 2 And 38 wt% to 65 wt% ZrO 2 (ii) a The noble metal is at least one selected from the group consisting of platinum, rhodium and palladium. The three-way catalyst has the advantages of low temperature, large oxygen storage amount, excellent ageing resistance and good high-temperature stability in CO catalytic oxidation.)

1. The three-way catalyst for catalyzing CO oxidation is characterized by comprising cerium-zirconium composite alumina loaded with noble metal, wherein the noble metal content in the three-way catalyst is 0.5-1.5 wt%, and the cerium-zirconium composite alumina comprises cerium-zirconium solid solution and gamma-Al₂O₃gamma-Al in the cerium-zirconium composite alumina₂O₃The content of (A) is 20 wt% -50 wt%, and the cerium-zirconium solid solution comprises 20 wt% -50 wt% of CeO₂And 38 wt%

-65wt％ZrO₂(ii) a The noble metal is at least one selected from the group consisting of platinum, rhodium and palladium.

2. The three-way catalyst according to claim 1, wherein the noble metal content of the three-way catalyst is 1 wt.%;

preferably, the noble metal is palladium.

3. The three-way catalyst according to claim 1, wherein γ -Al in the cerium zirconium composite alumina₂O₃The content of (B) is 30-40 wt%.

4. The three-way catalyst according to claim 1, wherein the cerium zirconium solid solution further comprises 2-4 wt% La₂O₃And 10 wt% to 15 wt% Y₂O₃；

Preferably, the cerium and zirconium are solid solutionThe body also comprises 3 wt% La₂O₃And 12.5 wt% Y₂O₃。

5. The three-way catalyst according to claim 1, wherein the cerium zirconium solid solution further comprises 4 wt% to 7 wt% La₂O₃And 4 wt% -8 wt% of Pr₆O₁₁；

Preferably, the cerium zirconium solid solution further comprises 5.5% La₂O₃And 6 wt% of Pr₆O₁₁。

6. Process for the preparation of a three-way catalyst according to any one of claims 1 to 5, characterized in that it comprises the following steps:

1) providing a cerium zirconium solid solution;

2) mixing cerium-zirconium solid solution with gamma-Al₂O₃Mixing, and carrying out first roasting to obtain cerium-zirconium composite alumina;

3) and loading the noble metal on the cerium-zirconium composite alumina by an isometric impregnation method, and performing second calcination to obtain the three-way catalyst.

7. The method according to claim 6, wherein the method of preparing the cerium-zirconium solid solution of step 1) comprises:

A. mixing materials: preparing a raw material into a primary mixture of a strong acid aqueous solution of a metal containing at least cerium ions and zirconium ions;

B. a first hydrothermal reaction: adding an alkaline precipitator into the primary mixture to prepare an acid mixture with the pH value of 1.5-2.0, and carrying out a first hydrothermal reaction on the acid mixture to prepare a precursor solution;

C. a second hydrothermal reaction: adding an alkaline precipitator into the precursor solution to prepare an alkaline mixture with the pH value of 8-11, and carrying out second hydrothermal reaction, filtering, washing and first calcining to prepare the cerium-zirconium solid solution;

wherein the temperature of the first hydrothermal reaction is 160-200 ℃ and the time is 15-25 h;

the temperature of the second hydrothermal reaction is 160-200 ℃, and the time is 6-10 h;

the first calcining comprises: heating to 250-300 ℃ at the rate of 40-60 ℃/h and keeping for 3-5h, heating to 700-800 ℃ at the rate of 110-130 ℃/h and keeping for 3-5 h;

the concentration of the metal oxide in the primary mixture is 85-160 g/L.

8. The method according to claim 6, wherein the cerium-zirconium solid solution in the step 2) is mixed with γ -Al₂O₃The mixing comprises the following steps: subjecting the gamma-Al to₂O₃Ball-milling for 8-12h under the protection of inert gas with the ball-material ratio of 8: 1 and the rotating speed of 250r/min, adding the cerium-zirconium solid solution, and continuing ball-milling for 5-25 h;

preferably, the first firing comprises: roasting at 800-900 deg.c for 1-5 hr.

9. The preparation method as claimed in claim 6, wherein the second calcination is carried out under conditions of calcination at 550 ℃ and 450 ℃ for 2-6 h.

10. Use of a three-way catalyst in a CO oxidation reaction, wherein the three-way catalyst is selected from the three-way catalysts of any one of claims 1 to 9.

Technical Field

The application relates to a three-way catalyst and a preparation method and application thereof, belonging to the field of adsorption catalyst materials.

Background

With the continuous and rapid prosperity of the economic society of China, the automobile conservation quantity rises linearly. The rapid development of motor vehicles is also accompanied by severe atmospheric pollution. Therefore, the work of controlling the automobile exhaust emission pollution becomes very difficult, especially in big cities, the situation is more severe, and about 60-80% of the total amount of the atmospheric pollutants come from the automobile exhaust emission. The automobile exhaust contains hundreds of different compounds, and the pollutants mainly comprise carbon monoxide (CO) and Nitrogen Oxide (NO)_x) Hydrocarbon (HC), suspended solid particles, sulfur oxides, and the like. Wherein CO is colorless and odorless, is a suffocating toxic gas, and can be combined with hemoglobin (Hb) at a very rapid speed, compared with O₂The bonding speed of (a) is 250 times faster. Meanwhile, under the condition of high temperature, nitrogen and oxygen in the air of the engine are subjected to chemical reaction to generate NO_xA contaminant. The pollutants cause serious damage and harm to the environment and human health, for example, high concentration of NO may cause mild central nervous disorder, NO may damage high altitude ozone protective layer, nitrogen dioxide can combine with water vapor in atmosphere to cause acid rain, NO₂Is also the main reason for generating acid rain, climate change and smog, NO₂When the catalyst is used together with HC, photochemical reaction can be generated to form photochemical smog, which directly threatens the physical and psychological health of people.

At present, the problem of controlling the emission pollution of the motor vehicle is mainly solved by a Three-way catalytic converter (TWC) pollution control device, so that increasingly strict emission standards put higher requirements on the industry of the Three-way catalyst.

The three-way catalyst mainly comprises a carrier, a coating, an active component and an auxiliary agent. For example, the support is a cordierite ceramic support and the active component can be both noble and non-noble types. The noble metal has a low melting point, and is easy to aggregate, grow and run off at high temperature, so that the catalytic activity is greatly reduced and even inactivated, the high-temperature stability of the noble metal catalyst is improved, and the ignition temperature of polluted gases such as CO is reduced, which becomes a problem to be solved urgently. In addition, the lower pollutant emission limits of the light motor vehicles of state six require high conversion efficiency and long service life of the catalyst.

Disclosure of Invention

In order to solve the problems, the three-way catalyst for catalyzing CO oxidation is low in temperature and stable in high temperature, and the preparation method and the application of the three-way catalyst are provided.

According to one aspect of the application, a three-way catalyst for catalyzing CO oxidation is provided, and comprises cerium-zirconium composite alumina loaded with noble metal, wherein the noble metal content of the three-way catalyst is 0.5 wt% -1.5 wt%, and the cerium-zirconium composite alumina comprises cerium-zirconium solid solution and gamma-Al₂O₃gamma-Al in the cerium-zirconium composite alumina₂O₃The content of (A) is 20-50 wt%, and the cerium-zirconium solid solution comprises 20-50 wt% of CeO₂And 38-65 wt% ZrO₂(ii) a The noble metal is at least one selected from the group consisting of platinum, rhodium and palladium.

Optionally, the three-way catalyst has a noble metal content of 1 wt%.

Preferably, the noble metal is palladium.

Optionally, gamma-Al in the cerium zirconium composite alumina₂O₃The content of (B) is 30-50 wt%.

Optionally, the cerium zirconium solid solution further comprises 2 wt% -4 wt% of La₂O₃And 10 wt% to 15 wt% Y₂O₃. Preferably, the cerium zirconium solid solution further comprises 3 wt% of La₂O₃And 12.5 wt% Y₂O₃。

Optionally, the cerium zirconium solid solution further comprises 4 wt% -7 wt% of La₂O₃And 4 wt% -8 wt% of Pr₆O₁₁. Preferably, the cerium zirconium solid solution further comprises 5.5% La₂O₃And 6 wt% of Pr₆O₁₁。

According to another aspect of the present application, there is provided a method for preparing the three-way catalyst, comprising the steps of:

1) providing a cerium zirconium solid solution;

2) mixing cerium-zirconium solid solution with gamma-Al₂O₃Mixing, and carrying out first roasting to obtain cerium-zirconium composite alumina;

3) and loading the noble metal on the cerium-zirconium composite alumina by an isometric impregnation method, and performing second calcination to obtain the three-way catalyst.

Optionally, the preparation method of the cerium zirconium solid solution of step 1) includes:

A. mixing materials: preparing raw materials into a primary mixture of a strong metal acid aqueous solution at least containing cerium ions and zirconium ions;

B. a first hydrothermal reaction: adding an alkaline precipitator into the primary mixture to prepare an acid mixture with the pH value of 1.5-2.0, and carrying out a first hydrothermal reaction on the acid mixture to prepare a precursor solution;

C. a second hydrothermal reaction: adding an alkaline precipitator into the precursor solution to prepare an alkaline mixture with the pH value of 8-11, and carrying out second hydrothermal reaction, filtering, washing and first calcining to obtain the cerium-zirconium composite oxide.

Optionally, the temperature of the first hydrothermal reaction is 160-200 ℃ and the time is 15-25 h.

Optionally, the temperature of the second hydrothermal reaction is 160-200 ℃ and the time is 6-10 h.

Optionally, the first calcining comprises: heating to 250-300 ℃ at the rate of 40-60 ℃/h and keeping for 3-5h, and heating to 700-800 ℃ at the rate of 110-130 ℃/h and keeping for 3-5 h.

Optionally, the oxide concentration of the metal in the initial mixture is 85-160 g/L. Preferably, the oxide concentration of the metal in the initial mixture is 110-140 g/L.

Optionally, the cerium zirconium solid solution in the step 2) is mixed with gamma-Al₂O₃The mixing comprises the following steps: the gamma-Al is added₂O₃Ball-milling for 8-12h under the protection of inert gas with the ball-material ratio of 8: 1 and the rotating speed of 250r/min, adding the cerium-zirconium solid solution, and continuing ball-milling for 5-25 h. Traditional mechanical mixing has easy operation, labour saving and time saving's advantage, but the homogeneity of mixing is poor, and the mixing method of this application can improve the homogeneity of mixing.

Optionally, the first firing comprises: roasting at 800-900 deg.c for 1-5 hr.

As an embodiment, the cerium-zirconium solid solution in the step 2) is mixed with γ -Al₂O₃The method of mixing comprises the steps of: according to the composite proportion of cerium, zirconium and alumina, firstly adding a certain amount of gamma-Al₂O₃Ball milling is carried out for 10 hours under the conditions that the ball material ratio is 8: 1, the rotating speed is 250r/min and nitrogen is used as protective gas, the particle size distribution is uniform, then cerium and zirconium with corresponding amount are added for ball milling for 20 hours, the cerium and zirconium are fully mixed, and finally, the cerium and zirconium composite alumina sample is prepared by roasting at 850 ℃ for 3 hours.

As an embodiment, the step 3) is performed by using palladium nitrate dihydrate (Pd (NO)₃)₂·2H₂O) is a noble metal precursor, and the isovolumetric impregnation method for preparing a sample with a theoretical loading of noble metal Pd of 1 wt% comprises the following steps:

0.13g Pd (NO) was weighed₃)₂·2H₂Dissolving O in 11.5mL of deionized water, dropwise adding a palladium nitrate aqueous solution into 5g of the cerium-zirconium composite alumina carrier, drying the catalyst slurry loaded with the Pd metal in a rotary evaporator, then placing the catalyst slurry in a forced air drying oven at 110 ℃ for drying for 3 hours, and then placing the catalyst slurry in a calcining furnace to calcine for 3 hours at 500 ℃ in a nitrogen atmosphere.

Optionally, the second calcination is calcination at 450-550 ℃ for 2-6 h. Preferably, the second calcination is calcination at 500 ℃ for 3 h.

According to a further aspect of the present application there is provided the use of a three-way catalyst selected from any of the three-way catalysts described above in a CO oxidation reaction.

Benefits of the present application include, but are not limited to:

1. the three-way catalyst for catalyzing CO oxidation has the excellent performances of low temperature, large oxygen storage amount, high ageing resistance and high temperature stability for catalyzing CO oxidation.

2. The preparation method of the three-way catalyst has the advantages of simple preparation method, low cost and easy industrialization.

3. According to the application of the three-way catalyst in catalyzing CO oxidation, the three-way catalyst can realize low-temperature high conversion rate of CO when being used for catalyzing CO oxidation.

Detailed Description

The present application will be described in detail with reference to examples, but the present application is not limited to these examples.

Unless otherwise specified, the raw materials and solvents in the examples of the present application were all purchased commercially. Gamma-alumina with a purity of > 99.0% was purchased from Zibozifeng aluminum industries, Inc.

The analysis method in the examples of the present application is as follows:

analysis of the specific surface area of the three-way catalyst was carried out using a Micromeritics TriStar model II fully automated adsorption apparatus from Mac instruments USA.

The analysis of the oxygen storage capacity of the three-way catalyst was carried out using the ChemBET-3000 instrument from Kangta.

Analysis of the three-way catalyst reduction temperature was performed using a PCA1200-TPR instrument from Pioder.

The method for evaluating the conversion rate of CO catalytically oxidized by the three-way catalyst comprises the following steps:

1) the activity evaluation of the catalyst is carried out on a self-made small sample evaluation reaction device provided with a U-shaped quartz reaction tube, a small group of quartz wool is plugged at the bottom of one side of the U-shaped quartz reaction tube, a weighed catalyst sample is placed, and mixed gas is introduced for determination;

2) the reaction is carried out at normal pressure, the loading of the catalyst is 120mg, the granularity is 40-60 meshes, and the volume of the raw material gas comprises: 3.76% CO, 6.24％O₂、90％N₂Space velocity 25000mL g^-1·h^-1The reaction temperature rise rate is 2 ℃/min;

3) the composition of the gas after passing through the catalyst was detected by chromatography, and the conversion of CO was calculated from the change in gas content before and after analysis.

According to one embodiment of the present application, a method of preparing a three-way catalyst comprises the steps of:

1) providing a cerium zirconium solid solution;

a, mixing materials: preparing raw materials into a primary mixture of a strong acid aqueous solution of rare earth metal at least containing cerium ions and zirconium ions, wherein the oxide concentration of the metal in the primary mixture is 85-160 g/L;

b, first hydrothermal reaction: adding an alkaline precipitator into the primary mixture to prepare an acid mixture with the pH value of 1.5-2.0, and carrying out a first hydrothermal reaction on the acid mixture to prepare a precursor solution; the temperature of the first hydrothermal reaction is 160-200 ℃ and the time is 15-25 h;

c, second hydrothermal reaction: adding an alkaline precipitator into the precursor solution to prepare an alkaline mixture with the pH value of 8-11, and carrying out second hydrothermal reaction, filtering, washing and first calcining to prepare the cerium-zirconium composite oxide; the temperature of the second hydrothermal reaction is 160-200 ℃ and the time is 6-10 h; the first calcination includes: heating to 250-300 ℃ at the rate of 40-60 ℃/h and keeping for 3-5h, heating to 700-800 ℃ at the rate of 110-130 ℃/h and keeping for 3-5 h;

2) mixing cerium-zirconium solid solution with gamma-Al₂O₃Mixing, and carrying out first roasting to obtain cerium-zirconium composite alumina;

cerium zirconium solid solution and gamma-Al₂O₃The mixing comprises the following steps: subjecting the gamma-Al to₂O₃Ball-milling for 8-12h under the protection of inert gas with the ball-material ratio of 8: 1 and the rotating speed of 250r/min, adding the cerium-zirconium solid solution, and continuing ball-milling for 5-25 h; the first firing includes: roasting at 800-900 deg.c for 1-5 hr;

3) loading noble metal on the cerium-zirconium composite alumina by an isometric impregnation method, and performing second calcination to prepare a three-way catalyst;

the second calcination was at 500 ℃ for 3 h.