Process for producing ceria-zirconia-alumina composite oxides and applications thereof
A composite oxide, aluminum oxide technology, applied in chemical instruments and methods, metal/metal oxide/metal hydroxide catalysts, separation methods, etc., can solve problems such as reduced oxygen storage capacity
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Embodiment 1
[0031] Embodiment 1: Preparation of Ce-Zr-Al composite oxide
[0032] Catalyst 1A : La-doped γ-alumina (22.5 kg, containing 4% La in distilled water (495 kg) 2 o 3 , d50=20μm) slurry was heated to 70°C, and then an aqueous solution of cerium (IV) nitrate (37.2kg, 16.3wt% Ce), an aqueous solution of zirconium oxynitrate (27.0kg, 14.6wt% Zr) and hydroxide Aqueous ammonium solution (31kg, 29wt% NH 4 OH). The reaction mixture was heated at 70°C for 1 hour while maintaining the pH above 8, then filtered and washed with distilled water. The wet cake filtrate was heated in air at 110°C for 12 hours in a static oven, and then calcined at 500°C in air for 4 hours to obtain Catalyst 1A. Catalyst 1A contains 21 wt% CeO 2 and 15wt% ZrO 2 .
[0033] Catalyst 1B : Catalyst 1B was prepared following the procedure of Catalyst 1A, except that 4% La 2 o 3 The colloidal boehmite (3.23kg, d50=70nm) was substituted for La-doped γ-alumina, and was slurried in 70kg distilled water, using...
Embodiment 3
[0036] Example 3: Laboratory Test Procedures and Results
[0037] Thermal durability tests were performed on powder samples of Catalysts 1A and 1B and Comparative Catalyst by firing in air at 1000°C for 4 hours. After firing, the samples were characterized using BET surface area, XRD crystal structure, and oxygen release capacity.
[0038] The BET surface area results are listed in Table 1. Catalyst 1A has the highest surface area, then Comparative Catalyst 2, and then Catalyst 1B. The lower surface area of Catalyst 1B is attributed to the lower thermal durability of boehmite compared to γ-alumina. Both Catalyst 1A and Comparative Catalyst 2 use γ-alumina. Catalyst 1A has a higher surface area, demonstrating the benefit of the inventive process for increased surface area.
[0039] XRD tests of the catalysts demonstrated that Catalyst 1A and Catalyst 1B exhibit a single Ce 0.5 Zr 0.5 o 2 crystal phase. In contrast, Comparative Catalyst 2 exhibits a mixed cerium-zircon...
Embodiment 4
[0043] Example 4: Engine Test Procedures and Results
[0044] Comparative Catalyst 4A is a commercial three-way (Pd-Rh) catalyst, using commercial La-stabilized alumina (4% La 2 o 3 ) Ce-Zr-Al mixed oxides produced by blending at a weight ratio of 0.57:1.
[0045] Catalyst 4B Same as Comparative Catalyst 4A, except that the Ce-Zr-Al mixed oxide used in Comparative Catalyst 4A was replaced by the ceria-zirconia-alumina mixed oxide of Catalyst 1A.
[0046] Comparative Catalyst 4A and Catalyst 4B were tested according to the Exhaust Emissions Federal Test Procedure (FTP) following EPA certification procedures and tolerances.
[0047] 2.3L engine motor vehicle FTP test : The three-way catalyst was aged in a gasoline engine for 100 hours at a maximum temperature of 924°C. Testing Aged Catalysts (4A and 4B) for Exhaust Pipe NO During FTP Cycles on a 2.3L Gasoline Vehicle x , hydrocarbon (HC) and CO emissions. The results are shown in Table 3, which shows the percent reduc...
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