CERIUM-ZIRCONIUM-ALUMINUM-BASED COMPOSITE MATERIAL, CGPF CATALYST AND PREPARATION METHOD THEREFOR

Abstract

A cerium-zirconium-aluminum-based composite material, a cGPF catalyst and a preparation method thereof are provided. The cerium-zirconium-aluminum-based composite material adopts a stepwise precipitation method, firstly preparing an aluminum-based pre-treated material, then coprecipitating the aluminum-based pre-treated material with zirconium and cerium sol, and finally roasting at high temperature to obtain the cerium-zirconium-aluminum-based composite material. The cerium-zirconium-aluminum-based composite material has better compactness and higher density, and when it is used in cGPF catalyst, it occupies a smaller volume of pores on the catalyst carrier, such that cGPF catalyst has lower back pressure and better ash accumulation resistance, which is beneficial to large-scale application of cGPF catalyst.

Claims

1. A preparation method of cerium-zirconium-aluminum-based composite material, which comprises the following steps: (1) Dissolving pseudo-boehmite in citric acid aqueous solution, adjusting the pH value to 4-10 with ammonia water, filtering and drying after the reaction under stirring is completed to obtain a precipitate; roasting the precipitate at a temperature of 200-400° C. for 0.1-5 h to obtain a pre-treated material; wherein the mass ratio of pseudo boehmite to citric acid is 5-20:1; (2) Adding the pre-treated material into a solution of mixed sol, adjusting the pH value to 4-10 with ammonia water after completely dissolution, filtering and drying after the reaction under stirring is completed to obtain a mixture precipitate; wherein the mixed sol is a sol containing cerium ions and zirconium ions; (3) Roasting the mixture precipitate at 500-600° C. for 1-10 h, and then at 800-1100° C. for 1-10 h to obtain the cerium-zirconium-aluminum composite material.

2. The preparation method according to claim 1, characterized in that, the mixed sol in Step (2) is a sol which further contains one or more selected from the group consisting of yttrium ion, lanthanum ion, neodymium ion, praseodymium ion, palladium ion and strontium ion.

3. A cerium-zirconium-aluminum-based composite material, characterized by being prepared by the preparation method of claim 1 or 2.

4. The composite material according to claim 3, characterized in that, the cerium-zirconium-aluminum-based composite material comprises the following components: 4-30 wt % of CeO.sub.2, 1-30 wt % of ZrO.sub.2, 40-95 wt % of Al.sub.2O.sub.3 and 0-20 wt % of rare earth metal oxide.

5. The composite material according to claim 3, characterized in that, the specific surface of the cerium-zirconium-aluminum-based composite material is 50-200 m.sup.2/g.

6. The composite material according to claim 3, characterized in that, the pore volume of the cerium-zirconium-aluminum-based composite material is 0.2-2.0 ml/g.

7. The composite material according to claim 3, characterized in that, the density of the cerium-zirconium-aluminum-based composite material is 0.5-1.5 g/ml.

8. A cGPF catalyst, characterized in that, the catalyst coating of the cGPF catalyst contains the cerium-zirconium-aluminum-based composite material as claimed in any one of claims 3 to 7.

9. A preparation method of cGPF catalyst according to claim 8, which is characterized by comprising the following steps: (1) Preparing slurry: mixing and ball-milling cerium-zirconium-aluminum-based composite material, cerium-zirconium-based material, aluminum sol and deionized water, adding pore-forming agent, mixing and ball-milling, adding palladium salt solution and rhodium salt solution, mixing and ball-milling to obtain coating slurry; (2) Coating: coating the coating slurry on the catalyst carrier; (3) Roasting: drying and roasting the coated catalyst carrier to obtain cGPF catalyst.

10. The preparation method according to claim 9, characterized in that, the mass ratio of the cerium-zirconium-based composite material to the cerium-zirconium-based material in Step (1) is 1:3-3:1.

Description

DETAILED DESCRIPTION OF EMBODIMENTS

[0041] The present invention will be further described in detail below with reference to test examples and specific embodiments. However, it should not be understood that the scope of the above subject matter of the present invention is only limited to the following examples, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

Example 1

[0042] A cerium-zirconium-aluminum-based composite material was consisted of the following components: 20% CeO.sub.2, 25% ZrO.sub.2, 2.5% La.sub.2O.sub.3, 2.5% Y.sub.2O.sub.3 and 50% Al.sub.2O.sub.3. The preparation method was as follows:

[0043] (1) Dissolving pseudo-boehmite in 10% by mass citric acid aqueous solution, adjusting pH value to 7 with ammonia water, filtering and drying to obtain a precipitate after the reaction under stirring was completed; roasting the precipitate at 300° C. for 3 h to obtain a pre-treated material;

[0044] (2) Adding the pre-treated materials into a solution of mixed sol of cerium, zirconium, lanthanum and yttrium (usually hydroxide sol, for example, prepared by mixing salts and reacting with alkali such as ammonia water), adjusting the pH value to 7 with ammonia water after completely dissolution, filtering and drying after the reaction under stirring was completed to obtain mixture precipitate;

[0045] (3) Roasting the mixture precipitate at 550° C. for 5 h, and then at 1000° C. for 3 h to obtain the cerium-zirconium-aluminum-based composite.

[0046] Through testing, the cerium-zirconium-aluminum-based composite had a specific surface of 76.2 m.sup.2/g, a pore volume of 0.8 ml/g, and a density of 1.23 g/ml.

Example 2

[0047] A cerium-zirconium-aluminum-based composite material was consisted of the following components: 20% CeO.sub.2, 25% ZrO.sub.2, 2.5% La.sub.2O.sub.3, 2.5% Y.sub.2O.sub.3 and 50% Al.sub.2O.sub.3. The preparation method was as follows:

[0048] (1) Dissolving pseudo boehmite in 5% by mass citric acid aqueous solution, adjusting pH value to 4 with ammonia water, filtering and drying to obtain a precipitate after the reaction under stirring was completed; roasting the precipitate at 200° C. for 5 h to obtain a pre-treated material;

[0049] (2) Adding the pre-treated material into a solution of mixed sol of cerium, zirconium, lanthanum and yttrium, adjusting the pH value to 4 with ammonia water after completely dissolution, filtering and drying after the reaction under stirring was completed to obtain a mixture precipitate;

[0050] (3) Roasting the mixture precipitate at 500° C. for 10 h, and then at 1100° C. for 1 h to obtain the cerium-zirconium-aluminum-based composite material.

[0051] Through testing, the cerium-zirconium-aluminum-based composite had a specific surface of 74.8 m.sup.2/g, a pore volume of 0.73 ml/g, and a density of 1.25 g/ml.

Example 3

[0052] A cerium-zirconium-aluminum-based composite material was consisted of the following components: 20% CeO.sub.2, 25% ZrO.sub.2, 2.5% La.sub.2O.sub.3, 2.5% Y.sub.2O.sub.3 and 50% Al.sub.2O.sub.3. The preparation method was as follows:

[0053] (1) Dissolving pseudo-boehmite in 15% by mass citric acid aqueous solution, adjusting pH value to 10 with ammonia water, filtering and drying to obtain a precipitate after the reaction under stirring was completed; roasting the precipitate at 400° C. for 0.1 h to obtain a pre-treated material;

[0054] (2) Adding the pre-treated material into a solution of mixed sol of cerium, zirconium, lanthanum and yttrium, adjusting the pH value to 10 with ammonia water after completely dissolution, filtering and drying after the reaction under stirring was completed to obtain a mixture precipitate;

[0055] (3) Roasting the mixture precipitate at 600° C. for 1 h, and then at 800° C. for 10 h to obtain the cerium-zirconium-aluminum-based composite material.

[0056] Through testing, the cerium-zirconium-aluminum-based composite had a specific surface of 78.5 m.sup.2/g, a pore volume of 0.83 ml/g, and a density of 1.21 g/ml.

Example 4

[0057] A cerium-zirconium-aluminum-based composite material was consisted of the following components: 10% CeO.sub.2, 10% ZrO.sub.2, 2.5% La.sub.2O.sub.3, 2.5% Y.sub.2O.sub.3 and 75% Al.sub.2O.sub.3. The preparation method was as follows:

[0058] (1) Dissolving pseudo-boehmite in 12% by mass citric acid aqueous solution, adjusting pH value to 7 with ammonia water, filtering and drying to obtain a precipitate after the reaction under stirring was completed; roasting the precipitate at 300° C. for 3 h to obtain a pre-treated material;

[0059] (2) Adding the pre-treated material into a solution of mixed sol of cerium, zirconium, lanthanum and yttrium, adjusting the pH value to 7 with ammonia water after completely dissolution, filtering and drying after the reaction under stirring was completed to obtain a mixture precipitate;

[0060] (3) Roasting the mixture precipitate at 550° C. for 5 h, and then at 1000° C. for 3 h to obtain the cerium-zirconium-aluminum-based composite.

[0061] Through testing, the cerium-zirconium-aluminum-based composite had a specific surface of 92.3 m.sup.2/g, a pore volume of 0.89 ml/g, and a density of 1.13 g/ml.

Example 5

[0062] A cerium-zirconium-aluminum-based composite material was consisted of the following components: 10% CeO.sub.2, 10% ZrO.sub.2, 2.5% La.sub.2O.sub.3, 2.5% Y.sub.2O.sub.3 and 75% Al.sub.2O.sub.3. The preparation method was as follows:

[0063] (1) Dissolving pseudo-boehmite in 10% by mass citric acid aqueous solution, adjusting pH value to 4 with ammonia water, filtering and drying to obtain a precipitate after the reaction under stirring was completed; roasting the precipitate at 200° C. for 5 h to obtain a pre-treated material;

[0064] (2) Adding the pre-treated material into a solution of mixed sol of cerium, zirconium, lanthanum and yttrium, adjusting the pH value to 4 with ammonia water after completely dissolution, filtering and drying after the reaction under stirring was completed to obtain a mixture precipitate;

[0065] (3) Roasting the mixture precipitate at 500° C. for 10 h, and then at 1100° C. for 1 h to obtain the cerium-zirconium-aluminum-based composite material.

[0066] Through testing, the cerium-zirconium-aluminum-based composite had a specific surface of 91.8 m.sup.2/g, a pore volume of 0.87 ml/g, and a density of 1.14 g/ml.

Example 6

[0067] A cerium-zirconium-aluminum-based composite material was consisted of the following components: 10% CeO.sub.2, 10% ZrO.sub.2, 2.5% La.sub.2O.sub.3, 2.5% Y.sub.2O.sub.3 and 75% Al.sub.2O.sub.3. The preparation method was as follows:

[0068] (1) Dissolving pseudo-boehmite in 20% by mass citric acid aqueous solution, adjusting pH value to 10 with ammonia water, filtering and drying to obtain a precipitate after the reaction under stirring was completed; roasting the precipitate at 400° C. for 0.1 h to obtain a pre-treated material;

[0069] (2) Adding the pre-treated material into a solution of mixed sol of cerium, zirconium, lanthanum and yttrium, adjusting the pH value to 10 with ammonia water after completely dissolution, filtering and drying after the reaction under stirring was completed to obtain a mixture precipitate;

[0070] (3) Roasting the mixture precipitate at 600° C. for 1 h, and then at 800° C. for 10 h to obtain the cerium-zirconium-aluminum-based composite material.

[0071] Through testing, the cerium-zirconium-aluminum-based composite had a specific surface of 95.3 m.sup.2/g, a pore volume of 0.91 ml/g, and a density of 1.11 g/ml.

Comparative Example 1

[0072] A cerium-zirconium-aluminum composite material was obtained by directly mixing 20% CeO.sub.2, 25% ZrO.sub.2, 2.5% La.sub.2O.sub.3, 2.5% Y.sub.2O.sub.3 and 50% Al.sub.2O.sub.3.

[0073] Through testing, the cerium-zirconium-aluminum composite material had a specific surface of 103.2 m.sup.2/g, a pore volume of 0.97 ml/g, and a density of 1.06 g/ml.

Comparative Example 2

[0074] A cerium-zirconium-aluminum-based composite material was consisted of the following components: 20% CeO.sub.2, 25% ZrO.sub.2, 2.5% La.sub.2O.sub.3, 2.5% Y.sub.2O.sub.3 and 50% Al.sub.2O.sub.3. The preparation method was as follows:

[0075] (1) Dissolving pseudo-boehmite in 10% by mass citric acid aqueous solution, adding into mixed sol solution of cerium, zirconium, lanthanum and yttrium, adjusting pH value to 7 with ammonia water after completely dissolution, filtering and drying after the reaction under stirring was completed to obtain mixture precipitate;

[0076] (2) Roasting the mixture precipitate at 550° C. for 5 h, and then at 1000° C. for 3 h to obtain the cerium-zirconium-aluminum-based composite.

[0077] Through testing, the cerium-zirconium-aluminum-based composite had a specific surface of 93.7 m.sup.2/g, a pore volume of 0.90 ml/g, and a density of 1.12 g/ml.

Comparative Example 3

[0078] A cerium-zirconium-aluminum-based composite material was consisted of the following components: 20% CeO.sub.2, 25% ZrO.sub.2, 2.5% La.sub.2O.sub.3, 2.5% Y.sub.2O.sub.3 and 50% Al.sub.2O.sub.3. The preparation method was as follows:

[0079] (1) Dissolving pseudo-boehmite in 10% by mass citric acid aqueous solution, adjusting pH value to 7 with ammonia water, filtering and drying to obtain a precipitate after the reaction under stirring was completed; roasting the precipitate at 300° C. for 3 h to obtain a pre-treated material;

[0080] (2) Adjusting the pH value of a solution of mixed sol of cerium, zirconium, lanthanum and yttrium to 7 with ammonia water, filtering and drying after the reaction under stirring was completed to obtain a mixture precipitate;

[0081] (3) After mixing and homogenizing the mixture precipitation and pre-treated materials, roasting at 550° C. for 5 h, and then at 1000° C. for 3 h to obtain the cerium-zirconium-aluminum-based composite material.

[0082] Through testing, the cerium-zirconium-aluminum-based composite had a specific surface of 96.8 m.sup.2/g, a pore volume of 0.93 ml/g, and a density of 1.09 g/ml.

Comparative Example 4

[0083] A cerium-zirconium-aluminum composite material was obtained by directly mixing 10% CeO.sub.2, 10% ZrO.sub.2, 2.5% La.sub.2O.sub.3, 2.5% Y.sub.2O.sub.3 and 75% Al.sub.2O.sub.3.

[0084] Through testing, the cerium-zirconium-aluminum composite material had a specific surface of 134.3 m.sup.2/g, a pore volume of 1.31 ml/g, and a density of 0.83 g/ml.

Comparative Example 5

[0085] A cerium-zirconium-aluminum-based composite material was consisted of the following components: 10% CeO.sub.2, 10% ZrO.sub.2, 2.5% La.sub.2O.sub.3, 2.5% Y.sub.2O.sub.3 and 75% Al.sub.2O.sub.3. The preparation method was as follows:

[0086] (1) Dissolving pseudo-boehmite in 10% by mass citric acid aqueous solution, adding into mixed sol solution of cerium, zirconium, lanthanum and yttrium, adjusting pH value to 7 with ammonia water after completely dissolution, filtering and drying after the reaction under stirring was completed to obtain mixture precipitate;

[0087] (2) Roasting the mixture precipitate at 550° C. for 5 h, and then at 1000° C. for 3 h to obtain the cerium-zirconium-aluminum-based composite.

[0088] Through testing, the cerium-zirconium-aluminum-based composite had a specific surface of 125.7 m.sup.2/g, a pore volume of 1.26 ml/g, and a density of 0.87 g/ml.

Comparative Example 6

[0089] A cerium-zirconium-aluminum-based composite material was consisted of the following components: 10% CeO.sub.2, 10% ZrO.sub.2, 2.5% La.sub.2O.sub.3, 2.5% Y.sub.2O.sub.3 and 75% Al.sub.2O.sub.3. The preparation method was as follows:

[0090] (1) Dissolving pseudo-boehmite in 10% by mass citric acid aqueous solution, adjusting pH value to 7 with ammonia water, filtering and drying to obtain a precipitate after the reaction under stirring was completed; roasting the precipitate at 300° C. for 3 h to obtain a pre-treated material;

[0091] (2) Adjusting the pH value of a solution of mixed sol of cerium, zirconium, lanthanum and yttrium to 7 with ammonia water, filtering and drying after the reaction under stirring was completed to obtain a mixture precipitate;

[0092] (3) After mixing and homogenizing the mixture precipitation and pre-treated materials, roasting at 550° C. for 5 h, and then at 1000° C. for 3 h, to obtain the cerium-zirconium-aluminum-based composite material.

[0093] Through testing, the cerium-zirconium-aluminum-based composite had a specific surface of 128.4 m.sup.2/g, a pore volume of 1.28 ml/g, and a density of 0.85 g/ml.

[0094] Preparation of the cGPF Catalysts

[0095] (1) Preparing slurry: mixing cerium-zirconium-aluminum-based composite materials (prepared from Examples 1-6 or Comparative Examples 1-6) and cerium-zirconium-based materials (40% CeO.sub.2, 50% ZrO.sub.2, 5% La.sub.2O.sub.3, 5% Y.sub.2O.sub.3) in a ratio of 1:1, and then adding aluminum sol (2% of slurry content) and polyurethane (2% of slurry content) and deionized water, adding rhodium nitrate solution (to ensure the Rh content density in the coating is 5 g/ft.sup.3), ball milling and stirring for 5 min to prepare coating slurry, and controlling the particle size D.sub.50 of the slurry to be 2.4 μm and the solid content to be 33 wt %;

[0096] (2) Coating: coating the coating slurry on the wall-flow cordierite carrier with a coating height of 90% of the carrier height and a coating amount of 50 g/L.

[0097] (3) Roasting: drying the coated catalyst carrier in a muffle furnace at 120° C. for 3 h, and then roasting in a muffle furnace at 550° C. for 3 h to obtain the cGPF catalyst.

[0098] Test Example:

[0099] Ash Loading Test on Bench:

[0100] The cGPF catalysts prepared above were installed on 1.8LTGDI engines, respectively, and loaded with ash according to SBC cycle condition in GB18352.6-2016 Emission Limits and Measurement Methods of Light Vehicle Pollutants (Chinese National Stage VI). The engine oil mixed combustion method was adopted, and the maximum cycle bed temperature was 980° C., and the target loading amount of ash was 30 g/L.

[0101] WLTC Emission Test of Whole Vehicle:

[0102] CGPF catalysts prepared above were used as chassis catalysts respectively, and TWC catalysts (Φ118.4*100−750/2, Pd=103 g/ft.sup.3, Rh=8 g/ft.sup.3) were used as close-coupled catalysts to form a post-treatment system, and emission tests were conducted on a 1.6TGDI car. Type I emission test was carried out according to “GB18352.6-2016 Emission Limits and Measurement Methods of Light Vehicle Pollutants (Chinese National Stage VI)”. In addition, pressure pipes were installed at the inlet and outlet of cGPF catalyst to detect the back pressure under WLTC cycle. The cyclic emission result of the catalyst at 1800 s and the maximum backpressure difference ΔP are recorded as follows.

TABLE-US-00001 PN No. CO(g/km) THC(g/km) NOx(g/km) (PCs/km) ΔP(kpa) Example 1 0.220 0.033 0.037 2.4*10.sup.11 10.5 Example 2 0.218 0.031 0.036 2 3*10.sup.11 10.1 Example 3 0.223 0.034 0.038 2.4*10.sup.11 10.8 Example 4 0.224 0.038 0.040 2.1*10.sup.11 12.3 Example 5 0.226 0.037 0.039 2.0*10.sup.11 11.8 Example 6 0.225 0.039 0.041 2.1*10.sup.11 12.7 Comparative 0.358 0.045 0.044 1.5*10.sup.11 14.5 Example 1 Comparative 0.355 0.044 0.043 1.5*10.sup.11 14.4 Example 2 Comparative 0.361 0.046 0.045 1.6*10.sup.11 14.7 Example 3 Comparative 0.372 0.048 0.050 1.2*10.sup.11 18.2 Example 4 Comparative 0.371 0.047 0.049 1.3*10.sup.11 17.5 Example 5 Comparative 0.369 0.048 0.049 1.3*10.sup.11 17.9 Example 6

[0103] According to the above experimental data, by applying the cerium-zirconium-aluminum-based composite material with higher density prepared by the method of the present invention in Examples 1-6 in the cGPF catalyst, the back pressure of cGPF catalyst after loading ash was significantly lower than that of cGPF catalyst made of conventional materials, and its exhaust emission purification effect was also better. therefore, the cerium-zirconium-aluminum-based composite material prepared by the method of the present invention can significantly improve the ash accumulation resistance of cGPF catalyst, which is beneficial to large-scale production and application of cGPF catalyst. Compared with the cerium-zirconium-aluminum-based composites prepared in Example 1, Comparative Examples 4-6 and Example 3, the density of the cerium-zirconium-aluminum-based composites in Comparative Examples 1-3 was significantly reduced, thus occupying more volume of pores on the catalyst carrier when applied to cGPF catalysts. Therefore, the porosity of cGPF catalysts prepared by using the cerium-zirconium-aluminum-based composites in Examples was higher than that of Comparative Examples, and the dynamic mass transfer of cGPF catalysts was better, and the purification ability of exhaust emission was better, and the ability to capture particulate matter in exhaust emission decreases.