Deterioration Mode of Barium-Containing NOx Storage Catalyst |
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Authors: | Bo-Hyuk Jang Tae-Hun Yeon Hyun-Sik Han Yong-Ki Park Jae-Eui Yie |
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Affiliation: | (1) School of Chemical Engineering, Ajou University, San 5, Wonchon, Suwon, Kyungki, Korea;(2) Heesung Engelhard Co., R&D Center, 16B-12, 455, Moknae, Ansan, Kyungki, Korea;(3) Korea Research Institute of Chemical Technology, Yusong, Taejon, 305-600, Korea |
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Abstract: | Barium-containing NOx storage catalyst showed serious deactivation under thermal exposure at high temperatures. To elucidate the thermal deterioration of the NOx storage catalyst, four types of model catalyst, Pt/Al2O3, Ba/Al2O3, Pt–Ba/Al2O3, and a physical mixture of Pt/Al2O3 + Ba/Al2O3 were prepared and their physicochemical properties such as BET, NO TPD, TGA/DSC, XRD, and XPS were evaluated while the thermal aging temperature was increased from 550 to 1050°C. The fresh Pt–Ba/Al2O3 showed a sorption capacity of 3.35 wt%/g-cat. but the aged one revealed a reduced capacity of 2.28 wt%/g-cat. corresponding to 68% of the fresh one. It was found that this reduced sorption capacity was directly related to the deterioration of the NOx storage catalyst by thermal aging. The Ba on Ba/Al2O3 and Pt–Ba/Al2O3 catalysts began to interact with alumina to form Ba–Al solid alloy above 600°C and then transformed into stable BaAl2O4 having a spinel structure. However, no phase transition was observed in the Pt/Al2O3 catalyst having no barium component, even after aging at 1050°C. |
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Keywords: | NOx storage catalyst deactivation mode Pt– Ba/Al2O3 BaAl2O4 |
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