Honeycomb-shaped three-way catalyst for vehicle and preparation method thereof

Abstract

The invention provides a honeycomb-shaped three-way catalyst for vehicles and a preparation method thereof, and relates to the technical field of catalysts.The catalyst comprises a honeycomb-shaped cordierite ceramic carrier, a Pd / Al2O3-CeZrOx slurry layer arranged on the surface of the honeycomb-shaped cordierite ceramic carrier and an Rh / CeZrOx-Al2O3 slurry layer arranged on the surface of the Pd / Al2O3-CeZrOx slurry layer, the coating amount of the Pd / Al2O3-CeZrOx slurry layer is 120-150 g / L, and the coating amount of the Rh / CeZrOx-Al2O3 slurry layer is 20-30 g / L. The coating amount of the Rh / CeZrOx-Al2O3 slurry layer is 80 to 120 g / L, the content of Pd in the catalyst is 0.01 to 10 g / L, and the content of Rh is 0.01 to 1 g / L. According to the honeycomb-shaped three-way catalyst for the vehicle and the preparation method of the honeycomb-shaped three-way catalyst, the prepared catalyst avoids formation of palladium-rhodium alloy, meanwhile, the dispersity of precious metal is high, the durability of the catalyst is also improved, and the honeycomb-shaped three-way catalyst for the vehicle has high market application value.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts, and in particular to a honeycomb three-way catalyst for vehicles and a preparation method thereof. Background Art

[0002] Automobile exhaust is an important source of air pollution. Exhaust includes carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NO x ), etc., directly endanger the ecological environment and human health. At present, catalytic conversion is the most effective way to deal with motor vehicle exhaust pollutants. The use of three-way catalysts (TWC) can convert automobile exhaust pollutants (HC, CO and NO x ) catalytic conversion to generate friendly gases such as carbon dioxide, nitrogen and water, which are discharged into the atmosphere to reduce environmental pollution; with the introduction of my country's National VI emission regulations, the control of various pollutants is becoming increasingly stringent, and the limits are getting lower and lower; traditional catalysts usually increase the amount of precious metals to meet increasingly stringent emission regulations, but precious metal resources are scarce, expensive, and non-renewable, so improving the utilization rate of precious metals is particularly important and has become a hot topic of current research.

[0003] Traditional catalysts use precious metal solutions that are directly added to the coating slurry, resulting in uneven distribution of the precious metals and easy sintering at high temperatures, causing agglomeration of the precious metals, which will result in reduced precious metal utilization and decreased activity. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a vehicle honeycomb three-way catalyst and a preparation method thereof. The preparation method of the present invention first adopts an in-situ reduction method to load the precious metal active component Pd on γ-Al2O3 and then reduce it into nanoparticles, which can improve the high-temperature sintering resistance of the active component Pd. Then, the precious metal active component Rh is loaded on the cerium-zirconium composite oxide by an ammonia-assisted method, which improves the utilization rate of the precious metal and the catalyst's NO x The processing capacity of the three-effect catalyst prepared can improve the utilization rate of precious metals in the catalyst, the catalytic performance and the service life, and has a large market application space.

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

[0006] A honeycomb three-way catalyst for a vehicle, wherein the catalyst comprises a honeycomb cordierite ceramic carrier, a Pd / Al2O3-CeZrO x Slurry layer and set on Pd / Al2O3-CeZrO x Rh / CeZrO on the surface of the slurry layer x-Al2O3 slurry layer, the Pd / Al2O3-CeZrO x The coating amount of the slurry layer is 120-150 g / L. x -The coating amount of the Al2O3 slurry layer is 80-120 g / L, the Pd content in the catalyst is 0.01-10 g / L, and the Rh content is 0.01-1 g / L.

[0007] The present application also provides a method for preparing a honeycomb three-way catalyst for a vehicle, which comprises the following steps, measured by weight:

[0008] Step S1. 100 parts by weight of γ-Al2O3 powder is added to 150 parts by weight of deionized water to obtain a first slurry, then 3-15 parts by weight of citric acid is added to the first slurry, and the mixture is stirred until the first slurry is evenly dispersed, and finally the first slurry is ground to obtain a second slurry;

[0009] Step S2. slowly dropwise adding 0.01-100 parts by weight of palladium nitrate solution into the second slurry, and continuously stirring for 3-5 hours;

[0010] Step S3. Weigh 1-20 parts by weight of a reducing agent, slowly dropwise add it to the second slurry treated in step S2, and continue stirring for 5-12 hours until the noble metal active components in the second slurry are completely reduced to obtain a third slurry;

[0011] Step S4. adding 100 parts by weight of cerium-zirconium composite oxide to 150 parts by weight of deionized water, stirring for 0.5-1h to obtain a fourth slurry, and then grinding the fourth slurry to obtain a fifth slurry;

[0012] Step S5. The third slurry and the fifth slurry are weighed and mixed according to the weight ratio of the solidified material of 1:5-5:1 to obtain the sixth slurry, and then the solid content of the sixth slurry is adjusted to 24% to 37% with deionized water, and cellulose is added to adjust the viscosity of the sixth slurry to 800-4000 mPa·s to obtain Pd / Al2O3-CeZrO x Slurry;

[0013] Step S6. Pd / Al2O3-CeZrO x The slurry is coated on a honeycomb cordierite ceramic carrier at a coating amount of 120-150 g / L, dried, and calcined to obtain a coated Pd / Al2O3-CeZrO x Semi-finished three-way catalyst for bottom slurry;

[0014] Step S7. Take 250 parts by weight of the fifth slurry, add 0.01 to 20 parts by weight of rhodium nitrate solution dropwise to the fifth slurry, continue stirring for 30 minutes, then add ammonia water dropwise until the pH of the fifth slurry reaches between 10.5 and 11.5, continue stirring for 3 to 5 hours, and obtain the seventh slurry;

[0015] Step S8. The seventh slurry and the second slurry are uniformly mixed in a weight ratio of 7:1-1:7 to obtain an eighth slurry, the solid content of the eighth slurry is adjusted to 24% to 32% with deionized water, cellulose is added, and the viscosity of the eighth slurry is adjusted to 800-2500 mPa·s to obtain Rh / CeZrOx-Al2O3 slurry;

[0016] Step S9: coating the Rh / CeZrOx-Al2O3 slurry on the semi-finished three-way catalyst at a coating amount of 80-120 g / L, drying, and calcining to obtain a finished three-way catalyst.

[0017] Preferably, in the method for preparing the vehicle honeycomb three-way catalyst, the particle size D90 of the second slurry in step S1 is 10-15 μm.

[0018] Preferably, in the method for preparing the honeycomb three-way catalyst for a vehicle, the mass concentration of the palladium nitrate solution in step S2 is 10-15%.

[0019] Preferably, in the method for preparing the vehicle honeycomb three-way catalyst, the reducing agent in step S3 is selected from one of hydrazine hydrate solution, formic acid, formaldehyde and ethylene glycol.

[0020] Preferably, in the method for preparing the vehicle honeycomb three-way catalyst, the particle size D90 of the fifth slurry in step S4 is 10-15 μm.

[0021] Preferably, in the method for preparing the vehicle honeycomb three-way catalyst, the cellulose described in step S5 and step S8 is selected from one or more of methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose.

[0022] Preferably, in the method for preparing the vehicle honeycomb three-way catalyst, in step S5, the drying temperature is 120-150° C., the drying time is 8-12 h, the calcination temperature is 500-600° C., and the calcination time is 2-4 h.

[0023] Preferably, in the method for preparing the vehicle honeycomb three-way catalyst, the mass concentration of the rhodium nitrate solution in step S7 is 10-15%.

[0024] Preferably, in the method for preparing the vehicle honeycomb three-way catalyst, in step S9, the drying temperature is 120-150° C., the drying time is 8-12 hours, the calcination temperature is 500-600° C., and the calcination time is 2-4 hours.

[0025] Advantages of the present invention:

[0026] The vehicle honeycomb three-way catalyst of the present invention and its preparation method, the catalyst comprises a honeycomb cordierite ceramic carrier, a Pd / Al2O3-CeZrO x Slurry layer and set on Pd / Al2O3-CeZrO x Rh / CeZrO on the surface of the slurry layer x -Al2O3 slurry layer, the coating material includes γ-alumina, cerium-zirconium oxygen storage material and binder, which are coated on a cordierite honeycomb ceramic carrier; the active components are precious metals Pd and Rh, which are uniformly dispersed in the coating material; the active component Pd is loaded on the alumina powder by a citric acid-assisted method, and then reduced with hydrazine hydrate, and mixed with an appropriate amount of cerium-zirconium oxygen storage material to make a slurry, which is used as the bottom slurry of the three-way catalyst, and is first coated on the pores of the honeycomb cordierite ceramic carrier; the active component Rh is loaded on the cerium-zirconium oxygen storage material by an ammonia-assisted method, and then mixed with an appropriate amount of γ-alumina to make a slurry, which is used as the outer layer material of the three-way catalyst, and is coated on the pores of the honeycomb cordierite ceramic carrier that has been coated with the bottom slurry. The catalyst prepared by this method avoids the formation of palladium-rhodium alloy, and at the same time, the precious metal dispersion is high, and the durability of the catalyst is also improved, which has a large market application value. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with specific embodiments.

[0028] The honeycomb cordierite ceramic carrier used in Examples 1-5 and Comparative Example 1 has a size of 118.4*114.3 mm, a mesh size of 600 mesh, a wall thickness of 3 mil, and a volume of 1.258 L; the manufacturer of the cerium-zirconium composite oxide is Solavy, and the model is WSZ-269.

[0029] Example 1

[0030] A honeycomb three-way catalyst for a vehicle, the catalyst comprising a honeycomb cordierite ceramic carrier, a Pd / Al2O3-CeZrO x Slurry layer and set on Pd / Al2O3-CeZrO x Rh / CeZrO on the surface of the slurry layer x -Al2O3 slurry layer, the Pd / Al2O3-CeZrO xThe coating amount of the slurry layer is 120 g / L. x -The coating amount of the Al2O3 slurry layer is 80 g / L.

[0031] The preparation method of the honeycomb three-way catalyst for vehicles of this embodiment comprises the following steps, measured by weight:

[0032] Step S1. 100 parts by weight of γ-Al2O3 powder is added to 150 parts by weight of deionized water to obtain a first slurry, and then 3 parts by weight of citric acid is added to the first slurry, and stirred until the first slurry is evenly dispersed, and finally the first slurry is ground to obtain a second slurry, and the particle size D90 of the second slurry is 13.2 μm;

[0033] Step S2. slowly dropwise adding 100 parts by weight of a palladium nitrate solution having a mass concentration of 10.60% into the second slurry, and continuously stirring for 3 hours;

[0034] Step S3. Weigh 20 parts by weight of a hydrazine hydrate solution having a mass concentration of 85%, slowly dropwise add it to the second slurry treated in step S2, and continue stirring for 5 hours until the noble metal active components in the second slurry are completely reduced to obtain a third slurry;

[0035] Step S4. 100 parts by weight of cerium-zirconium composite oxide is added to 150 parts by weight of deionized water, and stirred for 0.5 h to obtain a fourth slurry, and then the fourth slurry is ground to obtain a fifth slurry, and the particle size D90 of the fifth slurry is 12.9 μm;

[0036] Step S5. The third slurry and the fifth slurry were weighed and mixed according to the solidified material weight ratio of 1:5 to obtain the sixth slurry. Then, the solid content of the fourth slurry was adjusted to 32% with deionized water, and 1.5 parts by weight of hydroxyethyl cellulose was added to adjust the viscosity of the sixth slurry to 3456 mPa·s to obtain Pd / Al2O3-CeZrO x Slurry;

[0037] Step S6. Pd / Al2O3-CeZrO x The slurry was coated on a honeycomb cordierite ceramic carrier at a coating amount of 120 g / L, dried at a drying temperature of 150 ° C for 12 h, and calcined at a calcination temperature of 550 ° C for 2 h to obtain a coated Pd / Al2O3-CeZrO x Semi-finished three-way catalyst for bottom slurry;

[0038] Step S7. Take 250 parts by weight of the fifth slurry, add 20 parts by weight of a 11.25% rhodium nitrate solution dropwise to the fifth slurry, continue stirring for 30 minutes, then add ammonia water dropwise until the pH of the fifth slurry is 10.7, continue stirring for 3 hours, and obtain the seventh slurry;

[0039] Step S8. The seventh slurry and the second slurry are mixed evenly in a weight ratio of 5:1 to the solidified material to obtain an eighth slurry, and the solid content of the eighth slurry is adjusted to 27% with deionized water, and 2.0 parts by weight of hydroxyethyl cellulose is added to adjust the viscosity of the eighth slurry to 1800 mPa·s to obtain Rh / CeZrO x -Al2O3 slurry;

[0040] Step S9. Rh / CeZrO x -Al2O3 slurry was coated on the semi-finished three-way catalyst at a coating amount of 80 g / L, dried at 120°C for 12 h, calcined at 600°C for 2 h, and obtained a finished three-way catalyst in which the contents of Pd and Rh were 2.12 g / L and 0.15 g / L, respectively.

[0041] Example 2

[0042] A honeycomb three-way catalyst for a vehicle, the catalyst comprising a honeycomb cordierite ceramic carrier, a Pd / Al2O3-CeZrO x Slurry layer and set on Pd / Al2O3-CeZrO x Rh / CeZrO on the surface of the slurry layer x -Al2O3 slurry layer, the Pd / Al2O3-CeZrO x The coating amount of the slurry layer is 130 g / L. x -The coating amount of the Al2O3 slurry layer is 90 g / L.

[0043] The preparation method of the honeycomb three-way catalyst for vehicles of this embodiment comprises the following steps, measured by weight:

[0044] Step S1. 100 parts by weight of γ-Al2O3 powder is added to 150 parts by weight of deionized water to obtain a first slurry, and then 6 parts by weight of citric acid is added to the first slurry, and stirred until the first slurry is evenly dispersed, and finally the first slurry is ground to obtain a second slurry, and the particle size D90 of the second slurry is 13.2 μm;

[0045] Step S2. 75 parts by weight of a 13.05% palladium nitrate solution was slowly added dropwise to the second slurry and stirred for 4 hours;

[0046] Step S3. Weigh 16 parts by weight of a hydrazine hydrate solution having a mass concentration of 85%, slowly dropwise add it to the second slurry treated in step S2, and continue stirring for 8 hours until the noble metal active components in the second slurry are completely reduced to obtain a third slurry;

[0047] Step S4. 100 parts by weight of cerium-zirconium composite oxide is added to 150 parts by weight of deionized water, and stirred for 0.5 h to obtain a fourth slurry, and then the fourth slurry is ground to obtain a fifth slurry, and the particle size D90 of the fifth slurry is 15.0 μm;

[0048] Step S5. The third slurry and the fifth slurry are weighed and mixed according to the weight ratio of the solidified material of 1:4 to obtain the sixth slurry. Then, the solid content of the sixth slurry is adjusted to 37% with deionized water, and 0.5 parts by weight of hydroxyethyl cellulose is added to adjust the viscosity of the sixth slurry to 1800 mPa·s to obtain Pd / Al2O3-CeZrO x Slurry;

[0049] Step S6. Pd / Al2O3-CeZrO x The slurry was coated on a honeycomb cordierite ceramic carrier at a coating amount of 130 g / L, dried at a drying temperature of 130 ° C for 12 h, and calcined at a calcination temperature of 600 ° C for 2 h to obtain a coated Pd / Al2O3-CeZrO x Semi-finished three-way catalyst for bottom slurry;

[0050] Step S7. Take 250 parts by weight of the fifth slurry, add 16 parts by weight of a 14.58% rhodium nitrate solution dropwise to the fifth slurry, continue stirring for 30 minutes, then add ammonia water dropwise until the pH of the fifth slurry is 11.5, continue stirring for 5 hours, and obtain the seventh slurry;

[0051] Step S8. The seventh slurry and the second slurry are mixed evenly according to a weight ratio of 5:2 of the solidified material to obtain an eighth slurry, and the solid content of the eighth slurry is adjusted to 30% with deionized water, and 2.5 parts by weight of hydroxyethyl cellulose are added to adjust the viscosity of the eighth slurry to 2500 mPa·s to obtain Rh / CeZrO x -Al2O3 slurry;

[0052] Step S9. Rh / CeZrO x -Al2O3 slurry was coated on the semi-finished three-way catalyst at a coating amount of 90 g / L, dried at a drying temperature of 130°C for 8 hours, and calcined at a calcination temperature of 500°C for 2 hours to obtain a finished three-way catalyst, in which the contents of Pd and Rh were 2.12 g / L and 0.15 g / L, respectively.

[0053] Example 3

[0054] A honeycomb three-way catalyst for a vehicle, the catalyst comprising a honeycomb cordierite ceramic carrier, a Pd / Al2O3-CeZrO x Slurry layer and set on Pd / Al2O3-CeZrOx Rh / CeZrO on the surface of the slurry layer x -Al2O3 slurry layer, the Pd / Al2O3-CeZrO x The coating amount of the slurry layer is 140 g / L. x -The coating amount of the Al2O3 slurry layer was 100 g / L.

[0055] The preparation method of the honeycomb three-way catalyst for vehicles of this embodiment comprises the following steps, measured by weight:

[0056] Step S1. 100 parts by weight of γ-Al2O3 powder is added to 150 parts by weight of deionized water to obtain a first slurry, then 9 parts by weight of citric acid is added to the first slurry, and the mixture is stirred until the first slurry is evenly dispersed, and finally the first slurry is ground to obtain a second slurry, wherein the particle size D90 of the second slurry is 13.2 μm;

[0057] Step S2. Slowly drop 50 parts by weight of a palladium nitrate solution having a mass concentration of 12.11% into the second slurry and continue stirring for 4 hours;

[0058] Step S3. Weigh 12 parts by weight of a hydrazine hydrate solution having a mass concentration of 85%, slowly dropwise add it to the second slurry treated in step S2, and continue stirring for 8 hours until the noble metal active components in the second slurry are completely reduced to obtain a third slurry;

[0059] Step S4. Add 100 parts by weight of cerium-zirconium composite oxide to 150 parts by weight of deionized water, stir for 0.5 h to obtain a fourth slurry, and then grind the fourth slurry to obtain a fifth slurry; the particle size D90 of the fifth slurry is 10.9 μm;

[0060] Step S5. The third slurry and the fifth slurry are weighed and mixed according to the weight ratio of the solidified material of 1:3 to obtain the sixth slurry. Then, the solid content of the sixth slurry is adjusted to 30% with deionized water, and 1.8 parts by weight of hydroxyethyl cellulose is added to adjust the viscosity of the sixth slurry to 4000 mPa·s to obtain Pd / Al2O3-CeZrO x Slurry;

[0061] Step S7. Pd / Al2O3-CeZrO x The slurry was coated on a honeycomb cordierite ceramic carrier at a coating amount of 140 g / L, dried at a drying temperature of 150 ° C for 12 h, and calcined at a calcination temperature of 600 ° C for 2 h to obtain a coated Pd / Al2O3-CeZrO x Semi-finished three-way catalyst for bottom slurry;

[0062] Step S7. Weigh 250 parts by weight of the fifth slurry, add 16 parts by weight of a 15.0% rhodium nitrate solution dropwise to the fifth slurry, continue stirring for 30 minutes, then add ammonia water dropwise until the pH of the fifth slurry is 11.1, continue stirring for 4 hours, and obtain the seventh slurry;

[0063] Step S8. The seventh slurry and the second slurry are mixed evenly in a weight ratio of 5:3 to obtain an eighth slurry, and the solid content of the eighth slurry is adjusted to 32% with deionized water, and 1.2 parts by weight of hydroxyethyl cellulose is added to adjust the viscosity of the eighth slurry to 1200 mPa·s to obtain Rh / CeZrO x -Al2O3 slurry;

[0064] Step S9. Rh / CeZrO x -Al2O3 slurry was coated on the semi-finished three-way catalyst at a coating amount of 100 g / L, dried at 150°C for 8 hours, calcined at 500°C for 2 hours, and obtained a finished three-way catalyst, in which the contents of Pd and Rh were 2.12 g / L and 0.15 g / L, respectively.

[0065] Example 4

[0066] A honeycomb three-way catalyst for a vehicle, the catalyst comprising a honeycomb cordierite ceramic carrier, a Pd / Al2O3-CeZrO x Slurry layer and set on Pd / Al2O3-CeZrO x Rh / CeZrO on the surface of the slurry layer x -Al2O3 slurry layer, the Pd / Al2O3-CeZrO x The coating amount of the slurry layer is 150 g / L. x -The coating amount of the Al2O3 slurry layer is 110 g / L.

[0067] The preparation method of the honeycomb three-way catalyst for vehicles of this embodiment comprises the following steps, measured by weight:

[0068] Step S1. 100 parts by weight of γ-Al2O3 powder is added to 150 parts by weight of deionized water to obtain a first slurry, and then 12 parts by weight of citric acid is added to the first slurry, and stirred until the first slurry is evenly dispersed, and finally the first slurry is ground to obtain a second slurry, and the particle size D90 of the second slurry is 14.2 μm;

[0069] Step S2. slowly dropwise add 28.27 parts by weight of a 15% palladium nitrate solution into the second slurry and continue stirring for 5 hours;

[0070] Step S3. Weigh 8 parts by weight of a hydrazine hydrate solution having a mass concentration of 85%, slowly dropwise add it to the second slurry treated in step S2, and continue stirring for 12 hours until the noble metal active components in the second slurry are completely reduced to obtain a third slurry;

[0071] Step S4. adding 100 parts by weight of cerium-zirconium composite oxide to 150 parts by weight of deionized water, stirring for 0.5 h to obtain a fourth slurry, then grinding the fourth slurry to obtain a fifth slurry, the particle size D90 of the fifth slurry is 13.5 μm;

[0072] Step S5. The third slurry and the fifth slurry are weighed and mixed according to the weight ratio of the solidified material of 1:2 to obtain the sixth slurry. Then, the solid content of the fourth slurry is adjusted to 34% with deionized water, and 1.0 part by weight of hydroxyethyl cellulose is added to adjust the viscosity of the fourth slurry to 2000 mPa·s to obtain Pd / Al2O3-CeZrO x Slurry;

[0073] Step S6. Pd / Al2O3-CeZrO x The slurry was coated on a honeycomb cordierite ceramic carrier at a coating amount of 150 g / L, dried at a drying temperature of 150 ° C for 12 h, and calcined at a calcination temperature of 600 ° C for 2 h to obtain a coated Pd / Al2O3-CeZrO x Semi-finished three-way catalyst for bottom slurry;

[0074] Step S7. 16.36 parts by weight of a 15.0% rhodium nitrate solution was added dropwise to the fifth slurry, and the mixture was stirred for 30 min. Ammonia water was then added dropwise until the pH value of the fifth slurry was 10.5, and the mixture was stirred for 5 h to obtain a seventh slurry.

[0075] Step S8. The sixth slurry and the second slurry are mixed evenly in a weight ratio of 5:4 to obtain an eighth slurry, and the solid content of the eighth slurry is adjusted to 24% with deionized water, and 3.0 parts by weight of hydroxyethyl cellulose is added to adjust the viscosity of the eighth slurry to 800 mPa·s to obtain Rh / CeZrO x -Al2O3 slurry;

[0076] Step S9. Rh / CeZrO x -Al2O3 slurry is coated on the semi-finished three-way catalyst at a coating amount of 110 g / L, dried at a drying temperature of 120°C for 8 hours, and calcined at a calcination temperature of 600°C for 2 hours to obtain a finished three-way catalyst.

[0077] Example 5

[0078] A honeycomb three-way catalyst for a vehicle, the catalyst comprising a honeycomb cordierite ceramic carrier, a Pd / Al2O3-CeZrO x Slurry layer and set on Pd / Al2O3-CeZrO x Rh / CeZrO on the surface of the slurry layer x -Al2O3 slurry layer, the Pd / Al2O3-CeZrO x The coating amount of the slurry layer is 120 g / L. x -The coating amount of the Al2O3 slurry layer is 120 g / L.

[0079] The preparation method of the honeycomb three-way catalyst for vehicles of this embodiment comprises the following steps, measured by weight:

[0080] Step S1. 100 parts by weight of γ-Al2O3 powder is added to 150 parts by weight of deionized water to obtain a first slurry, and then 15 parts by weight of citric acid is added to the first slurry, and stirred until the first slurry is evenly dispersed, and finally the first slurry is ground to obtain a second slurry, and the particle size D90 of the second slurry is 11.2 μm;

[0081] Step S2. slowly dropwise add 23.56 parts by weight of a 15% palladium nitrate solution into the second slurry and continue stirring for 5 hours;

[0082] Step S3. Weigh 4 parts by weight of a hydrazine hydrate solution having a mass concentration of 85%, slowly dropwise add it to the second slurry treated in step S2, and continue stirring for 12 hours until the noble metal active components in the second slurry are completely reduced to obtain a third slurry;

[0083] Step S4. adding 100 parts by weight of cerium-zirconium composite oxide to 150 parts by weight of deionized water, stirring for 0.5 h to obtain a fourth slurry, then grinding the fourth slurry to obtain a fifth slurry, the particle size D90 of the fifth slurry is 14.5 μm;

[0084] Step S5. The third slurry and the fifth slurry are weighed and mixed according to a solidified material weight ratio of 1:1 to obtain a sixth slurry, and then the solid content of the sixth slurry is adjusted to 24% with deionized water, and 2.1 parts by weight of hydroxyethyl cellulose is added to adjust the viscosity of the fourth slurry to 3000 mPa·s to obtain Pd / Al2O3-CeZrO x Slurry;

[0085] Step S6. Pd / Al2O3-CeZrO xThe slurry was coated on a honeycomb cordierite ceramic carrier at a coating amount of 120 g / L, dried at a drying temperature of 120 ° C for 12 h, and calcined at a calcination temperature of 600 ° C for 2 h to obtain a coated Pd / Al2O3-CeZrO x Semi-finished three-way catalyst for bottom slurry;

[0086] Step S7. Take 250 parts by weight of the fifth slurry, add 16.67 parts by weight of a 15.0% rhodium nitrate solution dropwise to the fifth slurry, continue stirring for 30 minutes, then add ammonia water dropwise until the pH of the fifth slurry is 10.5, continue stirring for 5 hours, and obtain the seventh slurry;

[0087] Step S8. The seventh slurry and the second slurry are mixed evenly in a weight ratio of 1:1 to the solidified material, the solid content of the eighth slurry is adjusted to 30% with deionized water, 0.8 parts by weight of hydroxyethyl cellulose is added, and the viscosity of the eighth slurry is adjusted to 800 mPa·s to obtain Rh / CeZrO x -Al2O3 slurry;

[0088] Step S9. The Rh / CeZrOx-Al2O3 slurry is coated on the semi-finished three-way catalyst at a coating amount of 120 g / L, dried at a drying temperature of 150°C for 12 hours, calcined at a calcination temperature of 600°C for 2 hours, and obtained a finished three-way catalyst, wherein the contents of Pd and Rh are 2.12 g / L and 0.15 g / L, respectively.

[0089] Comparative Example 1

[0090] Comparative Example 1 The catalyst comprises a honeycomb cordierite ceramic carrier, a Pd / Al2O3-CeZrO x Slurry layer and set on Pd / Al2O3-CeZrO x Rh / CeZrO on the surface of the slurry layer x -Al2O3 slurry layer, the Pd / Al2O3-CeZrO x The coating amount of the slurry layer is 120 g / L. x -The coating amount of the Al2O3 slurry layer is 80 g / L.

[0091] The preparation method of the catalyst of Comparative Example 1 comprises the following steps, measured by weight:

[0092] Step S1. 100 parts by weight of γ-Al2O3 powder is added to 150 parts by weight of deionized water to obtain a first slurry, and then 3 parts by weight of citric acid is added to the first slurry, and stirred until the first slurry is evenly dispersed, and finally the first slurry is ground to obtain a second slurry, and the particle size D90 of the second slurry is 13.2 μm;

[0093] Step S2. slowly dropwise adding 100 parts by weight of a palladium nitrate solution having a mass concentration of 10.60% into the second slurry, and continuously stirring for 3 hours to obtain a third slurry;

[0094] Step S3. adding 100 parts by weight of cerium-zirconium composite oxide to 150 parts by weight of deionized water, stirring for 0.5 h to obtain a fourth slurry, and then grinding the fourth slurry to obtain a fifth slurry, wherein the particle size D90 of the fifth slurry is 12.9 μm;

[0095] Step S4. The third slurry and the fifth slurry were weighed and mixed according to the weight ratio of the solidified material of 1:5 to obtain the sixth slurry. Then, the solid content of the fourth slurry was adjusted to 32% with deionized water, and 1.5 parts by weight of hydroxyethyl cellulose was added to adjust the viscosity of the sixth slurry to 3586 mPa·s to obtain Pd / Al2O3-CeZrO x Slurry;

[0096] Step S5. Pd / Al2O3-CeZrO x The slurry was coated on a honeycomb cordierite ceramic carrier at a coating amount of 120 g / L, dried at a drying temperature of 150 ° C for 12 h, and calcined at a calcination temperature of 550 ° C for 2 h to obtain a coated Pd / Al2O3-CeZrO x Semi-finished three-way catalyst for bottom slurry;

[0097] Step S6. Take 250 parts by weight of the fifth slurry, add 20 parts by weight of a 11.25% rhodium nitrate solution dropwise to the fifth slurry, and continue stirring for 3 hours to obtain a seventh slurry;

[0098] Step S7. The seventh slurry and the second slurry are mixed evenly in a weight ratio of 5:1 to the solidified material to obtain an eighth slurry, the solid content of the eighth slurry is adjusted to 27% with deionized water, 1.8 parts by weight of hydroxyethyl cellulose is added, and the viscosity of the eighth slurry is adjusted to 1560 mPa·s to obtain Rh / CeZrO x -Al2O3 slurry;

[0099] Step S8. Rh / CeZrO x-Al2O3 slurry was coated on the semi-finished three-way catalyst at a coating amount of 80 g / L, dried at 120°C for 12 h, calcined at 600°C for 2 h, and obtained a finished three-way catalyst, in which the contents of Pd and Rh were 2.12 g / L and 0.15 g / L, respectively.

[0100] Catalyst performance evaluation

[0101] The performance of the catalysts prepared in Examples 1-5 and Comparative Example 1 was compared in fresh state and aged state.

[0102] Evaluation conditions: The atmosphere contained NO (800 ppm), CO2 (14%), H2O (10%), C3H6 (300 ppm), C3H8 (140 ppm), and CO (1.2%). The carrier gas was nitrogen. The heating rate was 10°C / min, and finally increased to 500°C.

[0103] Aging conditions: oxidizing atmosphere (1% O2) and reducing atmosphere (0.5% CO) were switched alternately, the aging temperature was 1050°C, and the time was 50 h.

[0104] The activity of fresh and aged states was evaluated in a high temperature reactor. The results are shown in Tables 1 and 2.

[0105] Table 1 Evaluation results of fresh catalyst activity

[0106]

[0107] Table 2 Catalyst aging activity evaluation results

[0108]

[0109] From the results in Table 1 and Table 2, it can be concluded that the three-way catalyst prepared by the patented method of the present invention is superior to the catalyst prepared by the traditional method in both fresh state performance and aged state performance. Among Examples 1-5, the catalyst prepared in Example 3 has the best catalytic performance and service life.

[0110] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A honeycomb three-way catalyst for a vehicle, characterized in that: The catalyst includes a honeycomb cordierite ceramic carrier, a Pd / Al2O3-CeZrO x Slurry layer and set on Pd / Al2O3-CeZrO x Rh / CeZrO on the surface of the slurry layer x - Al2O3 slurry layer, the Pd / Al2O3-CeZrO x The coating amount of the slurry layer is 120-150 g / L. x - The coating amount of Al2O3 slurry layer is 80-120 g / L, the Pd content in the catalyst is 0.01-10 g / L, and the Rh content is 0.01-1 g / L.

2. A method for preparing a honeycomb three-way catalyst for a vehicle according to claim 1, characterized in that: By weight, the method comprises the following steps: Step S1. 100 parts by weight of γ-Al2O3 powder is added to 150 parts by weight of deionized water to obtain a first slurry, then 3-15 parts by weight of citric acid is added to the first slurry, and the mixture is stirred until the first slurry is evenly dispersed, and finally the first slurry is ground to obtain a second slurry; Step S2. slowly dropwise adding 0.01-100 parts by weight of palladium nitrate solution into the second slurry, and continuously stirring for 3-5 hours; Step S3. Weigh 1-20 parts by weight of a reducing agent, slowly dropwise add it to the second slurry treated in step S2, and continue stirring for 5-12 hours until the noble metal active components in the second slurry are completely reduced to obtain a third slurry; Step S4. adding 100 parts by weight of cerium-zirconium composite oxide to 150 parts by weight of deionized water, stirring for 0.5-1h to obtain a fourth slurry, and then grinding the fourth slurry to obtain a fifth slurry; Step S5. The third slurry and the fifth slurry are weighed and mixed according to the weight ratio of the solidified material of 1:5-5:1 to obtain the sixth slurry, and then the solid content of the sixth slurry is adjusted to 24%-37% with deionized water, and cellulose is added to adjust the viscosity of the sixth slurry to 800-4000 mPa·s to obtain Pd / Al2O3-CeZrO x Slurry; Step S6. Pd / Al2O3-CeZrO x The slurry was coated on a honeycomb cordierite ceramic carrier at a coating amount of 120-150 g / L, dried, and calcined to obtain a coated Pd / Al2O3-CeZrO x Semi-finished three-way catalyst for bottom slurry; Step S7. Weigh 250 parts by weight of the fifth slurry, add 0.01 to 20 parts by weight of rhodium nitrate solution dropwise to the fifth slurry, continue stirring for 30 min, then add ammonia water dropwise until the pH of the fifth slurry is 10.5 to 11.5, continue stirring for 3 to 5 h, and obtain the seventh slurry; Step S8. The seventh slurry and the second slurry are mixed evenly according to a weight ratio of 7:1-1:7 of the solidified material to obtain an eighth slurry, and the solid content of the eighth slurry is adjusted to 24% to 32% with deionized water, and cellulose is added to adjust the viscosity of the eighth slurry to 800-2500 mPa·s to obtain Rh / CeZrO x - Al2O3 slurry; Step S9. Rh / CeZrO x - The Al2O3 slurry is coated on the semi-finished three-way catalyst at a coating amount of 80-120 g / L, dried, and calcined to obtain a finished three-way catalyst.

3. The method for preparing a honeycomb three-way catalyst for a vehicle according to claim 2, characterized in that: The particle size D90 of the second slurry in step S1 is 10-15 µm.

4. The method for preparing a honeycomb three-way catalyst for a vehicle according to claim 2, characterized in that: The mass concentration of palladium nitrate solution in step S2 is 10-15%.

5. The method for preparing a honeycomb three-way catalyst for a vehicle according to claim 2, characterized in that: In step S3, the reducing agent is selected from one of hydrazine hydrate solution, formic acid, formaldehyde and ethylene glycol.

6. The method for preparing a honeycomb three-way catalyst for a vehicle according to claim 2, characterized in that: The particle size D90 of the fifth slurry in step S4 is 10-15 µm.

7. The method for preparing a honeycomb three-way catalyst for a vehicle according to claim 2, wherein the cellulose in step S5 and step S8 is selected from one or more of methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose.

8. The method for preparing a honeycomb three-way catalyst for a vehicle according to claim 2, characterized in that: In step S6, the drying temperature is 120-150°C, the drying time is 8-12 h, the calcination temperature is 500-600°C, and the calcination time is 2-4 h.

9. The method for preparing a honeycomb three-way catalyst for a vehicle according to claim 2, characterized in that: The mass concentration of the rhodium nitrate solution in step S7 is 10-15%.

10. The method for preparing a honeycomb three-way catalyst for a vehicle according to claim 2, characterized in that: In step S9, the drying temperature is 120-150°C, the drying time is 8-12 hours, the calcination temperature is 500-600°C, and the calcination time is 2-4 hours.

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