Highly thermo-stable mesoporous catalyst Pt/BaCO 3–Al 2O 3 used for efficient NO x storage and desulfation: Comparison with conventional impregnated catalyst

Abstract

A mesoporous NSR catalyst Pt/BaCO 3–Al 2O 3 was synthesized by using tri-block copolymer P123 as template. Systematic comparative studies on the structural and catalytic performance between the mesoporous catalyst and the conventional impregnated one were performed. N 2 physisorption, XRD, TPD were employed for their structural characterization. In situ DRIFTS, TPR, TEM were used for investigation of the catalytic behaviors for NO x and SO x sorption, as well as desulfation. The results of structural characterization show that mesoporous Pt/BaCO 3–Al 2O 3 exhibits high surface area (261 m 2 g −1 after calcination at 600 °C), uniform pore size with a diameter of ca. 5 nm and high thermal stability up to 800 °C. The Ba-containing species are highly dispersed in three-dimensions and strongly interacted with Al 2O 3, and all the BaCO 3 presents as LT-BaCO 3 (BaCO 3 with low thermal stability). By contrast, most of the Ba species in the impregnated sample exist predominantly as HT-BaCO 3 (BaCO 3 with high thermal stability) and are enriched on the surface. As a result, the mesoporous sample possesses great advantages in serving as NSR catalysts, such as enhanced NO x trapping ability, lower sulfation degree, and higher desulfation extent, as compared with the impregnated one. In addition, after NO x and SO x sorption, no bulk phases of barium nitrates and sulfates were observed in the mesoporous catalyst, while they are evidently formed on the impregnated one. In a word, the mesoporous structure is of great significance in achieving high dispersion of barium species and better performance for NO x storage and regeneration of the catalyst.