Fine structural characterization of noble metals in washcoat of motorcycle three-way converter catalysts. Issue 2 (April 2023)

• Record Type: Journal Article
• Authors: Lin, Kuen-Song; Mdlovu, Ndumiso Vukile; Juang, Ruey-Shin; Tang, Mau-Tsu
• Is Part Of: Journal of environmental chemical engineering. Volume 11:Issue 2(2023)
• Publication Date: 2023-04
• Subjects: Three-way catalyst -- Washcoat -- Catalytic converter -- Deactivation -- Motorcycle -- XANES/EXAFS; Chemical engineering -- Environmental aspects -- Periodicals; Environmental engineering -- Periodicals; Chemical engineering -- Environmental aspects; Environmental engineering; Periodicals; 660.0286
• DOI: 10.1016/j.jece.2023.109530
• Languages: English
• ISSNs: 2213-2929

Abstract

Abstract: In Taiwan, over 14 million motorcycles exhaust vast amounts of pollutant gases, for which 24% of the total air pollutants cause significant air pollution in urban areas. The fine structures and the oxidation states of Pt/Pd/Rh/Ce species in washcoat catalysts of three-way motorcycle catalytic converters were investigated using EXAFS/XANES spectroscopy. Herein, a test of the federal test procedure (FTP) cycle for the deactivation of a motorcycle catalytic converter was conducted at running distances of 0, 5, 000, 10, 000, 15, 000, and 30, 000 km. Emissions of HCs pollutants were well controlled with Pt/Rh/Pd/Ce species supports on ceria/alumina washcoat owing to the exclusion of CO. The oxygen-rich environment leads to readily oxidized Rh and Pd species in the washcoat, while the Pt species are relatively difficult to oxidize. The Pd (Rh and Pt) species in the fresh and used washcoat catalysts have bond distances of 2.02 (2.03 and 1.90) and 2.75 (2.68 and 2.76) ± 0.02 Å and coordination numbers of 3.32 (5.70 and 4.13) and 11.81 (11.94 and 12.05) ± 0.05, respectively. Ceria species in washcoat catalysts are associated with the promotion of the crystalline phase to Ce(III) with a bond distance of 2.61 Å and a coordination number of 10.18 after 15, 000 km catalyst FTP cycling. In addition, the transition metal is satisfactorily consisted with the La-O distances at about 2.49 Å. Graphical Abstract: ga1 Highlights: Fine structures of Pt/Pd/Rh/Ce species investigated by EXAFS/XANES spectroscopy. HCs and NOx emissions well controlled with Pt/Rh/Pd/Ce supports on ceria/alumina. Ceria species promote crystalline phase to Ce(III) with a bond distance of 2.61 Å after 15, 000 km. CO, HCs or NOx conversion of the fresh catalyst was more efficient than the used one. The thermal aging generally promoting an increase of sample crystallinity was observed.