The study of Pt/zeolites for CO oxidation: Effects of skeleton structure and Si/Al ratio

Abstract

Recently, catalytic oxidation of CO over zeolite supported Pt catalysts has garnered significant attention. The effect of zeolite structure (BEA, MFI and CHA) and Si/Al (17, 10 and 6) molar ratio of Pt/zeolites on CO catalytic oxidation activity were investigated in this work. CO conversion increased with decreasing pore size and increasing Si/Al molar ratio. The optimized Pt/CHA with Si/Al of 17 shows the highest activity, achieving complete CO conversion below 140 °C. N2-sorption isotherms, XRD patterns, TEM images, in-situ DRIFTS, and XAFS measurements were conducted to investigate the zeolite structure and Pt species. The large cavity of CHA zeolite plays important role in the CO catalytic oxidation in the fresh Pt/zeolites, which lead to the higher CO conversion of Pt/CHA than Pt/BEA and Pt/MFI zeolites. Increasing the Si/Al favors the presence of Pt0 species, which showed excellent CO catalytic oxidation ability. Moreover, the structure with high Si/Al is stable, which protect Pt0 species from accumulating during hydrothermal aging. This work provides a guidance to controllably select optimal Si/Al molar ratio and channel structures of zeolite as support for CO oxidation reaction.

Keywords

• Pt/zeolites
• Si/Al ratio
• Channels structure
• CO oxidation