A high-temperature fixed precious metal catalyst and its preparation method

Abstract

The present invention provides a high-temperature immobilized precious metal catalyst comprising a carrier and a coating applied to the carrier. The coating comprises a composite oxygen storage agent, a precious metal immobilizer, and precious metal Rh. The composite oxygen storage agent accounts for 47% to 81% of the coating mass, the precious metal immobilizer accounts for 18% to 51% of the coating mass, and the coating is applied in an amount of 90 to 180 g / L. The high-temperature immobilized precious metal catalyst and its preparation method of the present invention improve the catalytic performance of gaseous pollutants while reducing the total amount of precious metal used, significantly reducing production costs. Simultaneously, the precious metal forms a synergistic catalytic effect in the coating, increasing the number of catalytically active sites and further enhancing catalytic activity. The catalyst exhibits high purification capacity for carbon monoxide, nitrogen oxides, and hydrocarbons and exhibits strong resistance to high-temperature aging.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a high-temperature fixed noble metal catalyst and a preparation method thereof. Background Art

[0002] Motor vehicle exhaust is the main component of smog particles. The main pollutants in automobile exhaust are carbon monoxide (CO), nitrogen oxides (NO X ) and hydrocarbons (HC). The multi-catalyst installed in the exhaust system can effectively convert CO, NO X The main function of the catalyst is to purify CO and HC compounds, while the main function of rhodium is to reduce NO X The current price of precious metals continues to rise, which has brought cost pressure to multi-component catalysts. Therefore, reducing the total amount of precious metals in the catalyst has become the current research trend of multi-component catalysts for gasoline vehicles. Summary of the Invention

[0003] The purpose of the present invention is to overcome and supplement the deficiencies in the prior art and to provide a high-temperature fixed precious metal catalyst and a method for preparing the same. The present invention improves the catalytic performance of gaseous pollutants while reducing the total amount of precious metals used, reduces production costs, and the prepared multi-component catalyst has good high-temperature anti-aging performance.

[0004] The present invention introduces rare earth metals such as La, Y, Eu and Sm during the coating preparation process. Through the synergistic effect between the rare earths, the precious metals Pt and Pd can be effectively fixed while the precious metal atoms are dispersed more evenly, thereby providing more active sites for coating catalysis. While reducing the total amount of precious metals used, the catalytic performance of gaseous pollutants is improved and the production cost is reduced. The prepared high-temperature fixed precious metal catalyst has good high-temperature anti-aging performance, which solves the problem of reduced catalytic performance caused by reducing precious metals.

[0005] The technical solution adopted in the present invention is:

[0006] A high-temperature fixed precious metal catalyst, wherein: the catalyst comprises a carrier and a coating coated on the carrier, the carrier is a honeycomb cordierite ceramic carrier, the coating comprises a composite oxygen storage agent, a precious metal fixing agent and precious metal Rh, the composite oxygen storage agent accounts for 47% to 81% of the coating mass, the precious metal fixing agent accounts for 18% to 51% of the coating mass, the coating amount is 90 to 180 g / L, and the loading amount of precious metal Rh is 0.75 to 5 g / ft 3 .

[0007] Preferably, in the high-temperature fixed noble metal catalyst, the composite oxygen storage agent comprises, by mass percentage, 90% to 96% of cerium-zirconium composite oxide and 4% to 10% of rare metals.

[0008] Preferably, the high-temperature fixed precious metal catalyst, wherein: by mass percentage, the cerium-zirconium composite oxide includes 40% to 76% of zirconium oxide, 20% to 50% of cerium oxide, 2% to 3% of lanthanum oxide, 1% to 4% of yttrium oxide, and 0% to 4% of one or two of europium oxide and samarium oxide.

[0009] Preferably, in the high-temperature fixed precious metal catalyst, the rare metals are selected from at least two of La, Y, Eu and Sm.

[0010] Preferably, the high-temperature fixed precious metal catalyst, wherein: the precious metal fixing agent comprises ZrO2, Al2O3, TiO2 and precious metals, and the precious metals are selected from one or both of Pt and Pd.

[0011] Preferably, the high temperature fixed noble metal catalyst, wherein: the noble metal fixing agent comprises 30% to 50% zirconium oxide, 40% to 63% aluminum oxide, 7% to 10% titanium dioxide, the noble metal

[0012] A method for preparing a high-temperature fixed noble metal catalyst, comprising the following steps:

[0013] (1) Preparation of composite oxygen storage agent: rare metal oxide powder is added to nitric acid solution and heated to 70°C for full reaction until all rare metal oxides are completely reacted and dissolved, and then cooled to room temperature. Cerium-zirconium composite oxide is added to the above solution, stirred until uniform, dried, and placed in a muffle furnace for calcination at 650°C to 700°C for 4 hours, and cooled to room temperature to obtain a composite oxygen storage agent;

[0014] (2) Preparation of precious metal fixing agent: 30% to 50% of zirconium oxide and 40% to 63% of aluminum oxide powder were added to deionized water and dispersed uniformly, and the pH of the system was adjusted to 8 to 10 to obtain a zirconium-aluminum mixed solution; 7% to 10% of sponge porous titanium was added to an excess of nitric acid solution, heated to 75°C, and fully reacted until the reaction was completely dissolved, cooled to room temperature, and the zirconium-aluminum mixed solution was slowly poured in, and the pH of the system was continuously maintained at 8 to 10. The mixture was dispersed for 0.5 h to obtain a mixed solution; 3 to 17 g / ft 3 The noble metal Pt or Pd is added dropwise while maintaining the system pH at 8-10, and dispersed for 1 hour, dried, and then calcined in a muffle furnace at 850-900°C for 3 hours, and cooled to room temperature to obtain a noble metal fixing agent;

[0015] (3) Preparation of coating slurry: Mix the composite oxygen storage agent and the precious metal fixing agent in a mass ratio of 47-81:18-51 and add deionized water to disperse evenly, then add 0.75-5g / ft 3 The precious metal Rh was dispersed for 0.5 h and then the pH of the system was adjusted to 6.5 to obtain a coating slurry.

[0016] (4) coating: uniformly coating the coating slurry obtained in step (3) on the honeycomb cordierite ceramic support, with a coating amount of 90 to 180 g / L;

[0017] (5) Drying and calcining: The carrier coated with the precious metal slurry obtained in step (4) is placed at 100°C to 180°C for 5 to 9 hours, and then calcined at 500 to 650°C for 2 to 4 hours to obtain a high-temperature fixed precious metal catalyst.

[0018] Preferably, in the method for preparing the high-temperature fixed noble metal catalyst, the mass ratio of the composite oxygen storage agent, the noble metal fixing agent and the deionized water in step (3) is 0.5:2.3 to 1.4:3.5.

[0019] Advantages of the present invention:

[0020] (1) The high-temperature fixed precious metal catalyst and its preparation method of the present invention improve the catalytic performance of gaseous pollutants while reducing the total amount of precious metals used, thereby significantly reducing production costs; at the same time, the precious metals form a synergistic catalytic effect in the coating, the catalytic active sites increase, and the catalytic activity is further enhanced. It has a high purification capacity for carbon monoxide, nitrogen oxides and hydrocarbons and has strong resistance to high-temperature aging. DETAILED DESCRIPTION

[0021] The present invention will be further described below with reference to specific embodiments.

[0022] The following examples and comparative examples all use honeycomb cordierite with a specification of Ф118.4mm×100mm, a pore density of 600cpsi, a pore wall thickness of 0.1016mm, and a volume of 1.101L as the carrier, Pt uses Pt(NO3)2 solution, Pd uses Pd(NO3)2 solution, and Rh uses Rh(NO3)3 solution.

[0023] Example 1

[0024] A high-temperature fixed noble metal catalyst comprises the following preparation steps:

[0025] (1) Preparation of composite oxygen storage agent: 6 g of lanthanum oxide, 12 g of yttrium oxide, 6 g of europium oxide and 6 g of samarium oxide powder were respectively placed in 1500 g of 7% nitric acid solution, heated to 70 ° C, and fully reacted until all rare metal oxides were completely reacted and dissolved, and cooled to room temperature. 270 g of cerium-zirconium composite oxide with a mass ratio of cerium oxide to zirconium oxide of 50:40 was added to the above solution, stirred for 1 hour, vacuum-dried at 90 ° C, placed in a muffle furnace and calcined at 650 ° C for 4 hours, and cooled to room temperature to obtain a composite oxygen storage agent;

[0026] (2) Preparation of precious metal fixing agent: 200g zirconium-aluminum composite oxide powder with a mass ratio of zirconium oxide to aluminum oxide of 30:63 was mixed with deionized water at a mass ratio of 1:2, dispersed evenly, the pH of the system was adjusted to 8.8, and stirred continuously to obtain a zirconium-aluminum mixed solution; 14g sponge porous titanium was placed in an excess of 5% nitric acid solution, heated to 75°C, and fully reacted until the reaction was completely dissolved, cooled to room temperature, and the dispersed zirconium-aluminum mixed solution was slowly poured into the titanium solution, and the pH of the system was maintained at 8-10 during the pouring process, and the dispersion was continued for 0.5h; 12g / ft2 was added dropwise to the mixed solution. 3 The noble metal Pt was added while maintaining the system pH at 8-10. The system was dispersed for 1 hour, dried under vacuum at 90°C, calcined in a muffle furnace at 850°C for 3 hours, and cooled to room temperature to obtain a noble metal fixing agent.

[0027] (3) Preparation of coating slurry: Mix the composite oxygen storage agent and the precious metal fixing agent in a mass ratio of 6:4 and add deionized water to disperse evenly. Add 2g / ft 3 The precious metal Rh was dispersed for 0.5 h and then the pH of the system was adjusted to 6.5. The particles were ball-milled to a D90 of 6 μm to obtain a coating slurry.

[0028] (4) coating: the coating slurry obtained in step (3) is evenly coated on the honeycomb cordierite ceramic support, with a coating amount of 120 g / L;

[0029] (5) Drying and calcining: The carrier coated with the precious metal slurry obtained in step (4) is dried at 180°C for 5 hours, and then calcined at 650°C for 2 hours to obtain a high-temperature fixed precious metal catalyst.

[0030] Example 2

[0031] A high-temperature fixed noble metal catalyst comprises the following preparation steps:

[0032] (1) Preparation of composite oxygen storage agent: 6 g of lanthanum oxide, 12 g of yttrium oxide and 12 g of samarium oxide powder were respectively placed in 1500 g of 7% nitric acid solution, heated to 70 ° C, and fully reacted until all rare metal oxides were completely reacted and dissolved, and cooled to room temperature. 270 g of cerium-zirconium composite oxide with a mass ratio of cerium oxide to zirconium oxide of 50:40 was added to the above solution, stirred for 1 hour, vacuum-dried at 90 ° C, placed in a muffle furnace and calcined at 650 ° C for 4 hours, and cooled to room temperature to obtain a composite oxygen storage agent;

[0033] (2) Preparation of precious metal fixing agent: 200g zirconium-aluminum composite oxide powder with a mass ratio of zirconium oxide to aluminum oxide of 30:63 was mixed with deionized water at a mass ratio of 1:2, dispersed evenly, the pH of the system was adjusted to 8.8, and stirred continuously to obtain a zirconium-titanium mixed solution; 20g sponge porous titanium was placed in 500g 5% nitric acid solution, heated to 75°C, and fully reacted until completely dissolved, cooled to room temperature, and slowly poured into the dispersed zirconium-aluminum mixed solution, maintaining the system pH at 8-10 during the pouring process, and continued to disperse for 0.5h; 12g / ft2 was added dropwise to the mixed solution. 3 The noble metal Pt was added while maintaining the system pH at 8-10. The system was dispersed for 1 hour, dried under vacuum at 90°C, calcined in a muffle furnace at 850°C for 3 hours, and cooled to room temperature to obtain a noble metal fixing agent.

[0034] (3) Preparation of coating slurry: The composite oxygen storage agent and the precious metal fixing agent prepared in step (1) and step (2) were mixed in a mass ratio of 7:3 and dispersed evenly with deionized water. 2 g / ft 3 The precious metal Rh was dispersed for 0.5 h and then the pH of the system was adjusted to 6.5. The particles were ball-milled to a D90 of 6 μm to obtain a coating slurry.

[0035] (4) coating: the coating slurry obtained in step (3) was evenly coated on the honeycomb cordierite ceramic support, with a coating amount of 170 g / L;

[0036] (5) Drying and calcining: The carrier coated with the precious metal slurry obtained in step (4) is dried at 180°C for 5 hours, and then calcined at 650°C for 2 hours to obtain a high-temperature fixed precious metal catalyst.

[0037] Example 3

[0038] A high-temperature fixed noble metal catalyst and a preparation method thereof, comprising the following steps:

[0039] (1) Preparation of composite oxygen storage agent: 6 g of lanthanum oxide and 24 g of yttrium oxide powder were respectively placed in 1500 g of 7% nitric acid solution, heated to 70°C, and reacted until all rare metal oxides were completely reacted and dissolved. The mixture was cooled to room temperature, and 270 g of cerium-zirconium composite oxide with a mass ratio of cerium oxide to zirconium oxide of 50:40 was added to the above solution. The mixture was stirred for 1 hour, vacuum-dried at 90°C, and calcined in a muffle furnace at 650°C for 4 hours. The mixture was cooled to room temperature to obtain a composite oxygen storage agent.

[0040] (2) Preparation of precious metal fixing agent: 200g zirconium-aluminum composite oxide powder with a mass ratio of zirconium oxide to aluminum oxide of 30:63 was mixed with deionized water at a mass ratio of 1:2, dispersed evenly, and the pH of the system was adjusted to 8.8, and stirred continuously; 20g sponge porous titanium was placed in 500g of 5% acid solution, heated to 75°C, and fully reacted until completely dissolved, cooled to room temperature, and slowly poured into the solution system with zirconium and aluminum dispersed therein, maintaining the pH of the system at 8-10 during the pouring process, and continued to disperse for 0.5h; 12g / ft2 was added dropwise to the mixed solution. 3 The noble metal Pt solution was added dropwise, and the pH of the system was maintained at 8-10. The solution was dispersed for 1 hour, dried under vacuum at 90°C, calcined in a muffle furnace at 850°C for 3 hours, and cooled to room temperature to obtain a noble metal fixing agent.

[0041] (3) Preparation of coating slurry: Mix the powders prepared in step (1) and step (2) in a mass ratio of 7:3 and add deionized water to disperse evenly. Add 2g / ft 3 The noble metal Rh solution was dispersed for 0.5 h and then the pH of the system was adjusted to 6.5 to obtain a coating slurry;

[0042] (4) coating: the coating slurry obtained in step (3) was evenly coated on the honeycomb cordierite ceramic support, with a coating amount of 170 g / L;

[0043] (5) Drying and calcining: The carrier coated with the precious metal slurry obtained in step (4) is dried at 180°C for 5 hours, and then calcined at 650°C for 2 hours to obtain a high-temperature fixed precious metal catalyst.

[0044] Comparative Example 1

[0045] A method for preparing a gasoline vehicle exhaust multi-element catalyst comprises the following steps:

[0046] (1) Preparation of coating slurry: 300 g La2O3-Al2O3, 650 g cerium-zirconium composite oxide and deionized water were mixed, and the mass ratio of the total mass of La2O3-Al2O3, cerium-zirconium composite oxide and deionized water was controlled to be 1:2;

[0047] (2) Preparation of coating slurry: The slurry prepared in step (1) was added to the Pt solution and the Rh solution respectively and stirred evenly, wherein the Pt loading was 19 g / ft 3 , the Rh loading is 2.5g / ft 3 , controlling the amount of deionized water added so that the mass fraction of solid matter in the suspension is 40%, and ball milling the suspension to obtain a uniformly dispersed Pt and Rh co-layer coating slurry;

[0048] (3) Coating, drying and calcining: The Pt and Rh co-layer coating slurry was coated on the honeycomb cordierite carrier with a coating amount of 120 g / L, dried at 150°C for 4 h, and then calcined at 550°C for 4 h to obtain a Pt and Rh co-layer multi-component catalyst.

[0049] Among them, La2O3-Al2O3 in the coating accounts for 22% of the coating mass, and cerium-zirconium composite oxide accounts for 78% of the coating mass; the composition of La2O3-Al2O3 is: 3% lanthanum oxide and 97% aluminum oxide; the composition of cerium-zirconium composite oxide is: 75% zirconium oxide, 20% cerium oxide, 1% lanthanum oxide and 4% neodymium oxide.

[0050] Comparative Example 2

[0051] A method for preparing a gasoline vehicle exhaust multi-element catalyst comprises the following steps:

[0052] (1) Preparation of coating slurry: 600 g of La2O3-Al2O3, 1300 g of cerium-zirconium composite oxide and deionized water were mixed, and the mass ratio of the total mass of La2O3-Al2O3, cerium-zirconium composite oxide and deionized water was controlled to be 1:2;

[0053] (2) Preparation of coating slurry: The slurry prepared in step (1) was added to the Pt solution and the Rh solution respectively and stirred evenly, wherein the Pt loading amount was 19 g / ft3 and the Rh loading amount was 2.5 g / ft3. The amount of deionized water added was controlled so that the mass fraction of solid matter in the suspension was 40%. The suspension was ball milled to obtain a uniformly dispersed Pt and Rh coating slurry.

[0054] (3) Coating, drying and calcining: The Pt and Rh co-layer coating slurry was coated on a honeycomb cordierite carrier with a coating amount of 170 g / L, dried at 150°C for 4 h, and then calcined at 550°C for 4 h to obtain a Pt and Rh co-layer multi-component catalyst.

[0055] Among them, La2O3-Al2O3 in the coating accounts for 22% of the coating mass, and cerium-zirconium composite oxide accounts for 78% of the coating mass; the composition of La2O3-Al2O3 is: 3% lanthanum oxide and 97% aluminum oxide; the composition of cerium-zirconium composite oxide is: 75% zirconium oxide, 20% cerium oxide, 1% lanthanum oxide and 4% neodymium oxide.

[0056] The catalyst samples prepared in Examples 1-3 and Comparative Examples 1-2 were aged according to the China VI SBC standard. After aging for 50 hours under the same conditions, vehicle emission tests were conducted according to the WLTC cycle. The test vehicle had an engine displacement of 1.4T. The emission test results are shown in Table 1:

[0057] Table 1 Catalyst emission test results

[0058] HC(g / km) CO(g / km) <![CDATA[NO X (g / km)]]> Example 1 0.0433 0.457 0.0306 Comparative Example 1 0.0514 0.525 0.0347 Example 2 0.0269 0.267 0.0173 Example 3 0.0281 0.284 0.0190 Comparative Example 2 0.0331 0.326 0.0215

[0059] Compared with Comparative Examples 1-2, Examples 1-3 were tested with the amount of precious metal Pt reduced by 36.8% and the amount of precious metal Rh reduced by 20.0%.

[0060] The catalyst emission test results in Table 1 show that Example 1 is more effective in purifying HC, CO, and NO than Comparative Example 1. X The catalytic performance of Example 2, Example 3 and Comparative Example 2 were significantly improved by 15.7%, 12.9% and 11.8% respectively; after increasing the amount of slurry coating and the ratio of the oxygen storage layer to the precious metal fixed catalyst layer, Example 2, Example 3 and Comparative Example 2 all had a significant improvement in catalytic performance. At the same time, compared with Comparative Example 2, Example 2 had a significant improvement in purifying HC, CO, and NO. X The results of Example 3 were improved by 18.7%, 18.1% and 19.5% respectively; compared with Comparative Example 2, the purification of HC, CO, and NO X The figures for the first half of 2019 showed an increase of 15.1%, 12.8% and 11.6% respectively.

[0061] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a high-temperature fixed noble metal catalyst, characterized in that: The following steps are involved: (1) Preparation of a composite oxygen storage agent: Powders of at least two rare earth metal oxides are added to a nitric acid solution and heated to 70°C for sufficient reaction until all rare earth metal oxides are completely reacted and dissolved, and then cooled to room temperature. A cerium-zirconium composite oxide is added to the above solution, stirred until uniform, dried, and placed in a muffle furnace for calcination at 650°C to 700°C for 4 hours, and cooled to room temperature to obtain a composite oxygen storage agent, wherein the rare earth metals are at least two selected from La, Y, Eu and Sm; (2) Preparation of precious metal fixing agent: According to the mass percentage, 30%~50% zirconium oxide and 40%~63% aluminum oxide powder are added to deionized water and dispersed evenly, and the pH of the system is adjusted to 8~10 to obtain a zirconium-aluminum mixed solution; 7%~10% sponge porous metal titanium is placed in an excess of nitric acid solution, heated to 75℃, and fully reacted until the reaction is completely dissolved, cooled to room temperature, and the zirconium-aluminum mixed solution is slowly poured in, and the pH of the system is continuously maintained at 8~10. Continue to disperse for 0.5h to obtain a mixed solution; 3~17 g / ft 3 The noble metal Pt or Pd is added while maintaining the system pH at 8-10. The system is dispersed for 1 hour and dried. The system is then calcined in a muffle furnace at 850-900°C for 3 hours and cooled to room temperature to obtain a noble metal fixing agent. (3) Preparation of coating slurry: Mix the composite oxygen storage agent and the precious metal fixing agent in a mass ratio of 47~81:18~51 and add deionized water to disperse evenly, then add 0.75~5 g / ft 3 The precious metal Rh was dispersed for 0.5 h and then the pH of the system was adjusted to 6.5 to obtain a coating slurry. (4) Coating: The coating slurry obtained in step (3) is evenly coated on the honeycomb cordierite ceramic carrier in an amount of 90 to 180 g / L; (5) Drying and calcining: The carrier coated with the precious metal slurry obtained in step (4) is placed at 100°C to 180°C for 5 to 9 hours, and then calcined at 500 to 650°C for 2 to 4 hours to obtain a high-temperature fixed precious metal catalyst.

2. The method for preparing a high-temperature immobilized noble metal catalyst according to claim 1, wherein: In step (3), the mass ratio of the composite oxygen storage agent, the noble metal fixing agent and the deionized water is 0.5:2.3~1.4:3.

5.

3. A high-temperature immobilized precious metal catalyst prepared according to the method for preparing a high-temperature immobilized precious metal catalyst according to any one of claims 1 to 2, characterized in that: The catalyst includes a carrier and a coating coated on the carrier. The carrier is a honeycomb cordierite ceramic carrier. The coating includes a composite oxygen storage agent, a precious metal fixing agent, and precious metal Rh. The composite oxygen storage agent accounts for 47% to 81% of the coating mass, the precious metal fixing agent accounts for 18% to 51% of the coating mass, and the loading amount of the precious metal Rh is 0.75 to 5 g / ft 3 The coating amount is 90~180 g / L.

4. The high-temperature immobilized noble metal catalyst according to claim 3, characterized in that: The noble metal fixing agent includes ZrO2, Al2O3, TiO2 and a noble metal, and the noble metal is selected from one of Pt and Pd.

5. The high-temperature immobilized noble metal catalyst according to claim 4, characterized in that: The precious metal fixing agent comprises 30% to 50% zirconium oxide, 40% to 63% aluminum oxide, and 7% to 10% titanium dioxide. The loading amount of Pt or Pd in ​​the precious metal is 3 to 17 g / ft 3 .