Highly thermo-stable mesoporous catalyst Pt/BaCO3–Al2O3 used for efficient NOx storage and desulfation: Comparison with conventional impregnated catalyst

A mesoporous NSR catalyst Pt/BaCO3–Al2O3 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. N2 physisorption, XRD, TPD were employed for their structural characterization. In situ DRIFTS, TPR, TEM were used for investigation of the catalytic behaviors for NOx and SOx sorption, as well as desulfation. The results of structural characterization show that mesoporous Pt/BaCO3–Al2O3 exhibits high surface area (261 m2 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 Al2O3, and all the BaCO3 presents as LT-BaCO3 (BaCO3 with low thermal stability). By contrast, most of the Ba species in the impregnated sample exist predominantly as HT-BaCO3 (BaCO3 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 NOx trapping ability, lower sulfation degree, and higher desulfation extent, as compared with the impregnated one. In addition, after NOx and SOx 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 NOx storage and regeneration of the catalyst.