Advantages of High-Siliceous Zeolites in the Reactivity and Stability of Diesel Oxidation Catalysts
Phuoc Hoang Ho, Dawei Yao, Derek Creaser, Louise Olsson
Abstract
This study demonstrates a comparison of oxidation performance and sulfur poisoning/regeneration between zeolite- and alumina-supported Pt catalysts for their use as diesel oxidation catalysts (DOC). All three Pt/zeolite catalysts (β, Y, and ZSM-5) with a high siliceous content (SiO2/Al2O3 = 211–243) prepared by incipient impregnation had an average size of Pt particles from 15 to 24 nm after degreening at 700 °C. The Pt/BEA catalyst not only outperformed the benchmark Pt/Al2O3 in terms of the conversion and T50 (e.g., lower by 13 and 72 °C for CO and C3H8, respectively) but also exhibited more stable conversion than the benchmark Pt/Al2O3 during five cycles of the activity test. All zeolite-based catalysts exhibited significantly higher conversions of C3H8 than Pt/Al2O3 possibly because of the better confinement of C3H8 in the zeolite pores in Pt/zeolites than Pt/Al2O3. SO2 inhibited the oxidation of CO and NO but promoted the oxidation of C3H8. Pt/zeolites were more susceptible to the poisoning with SO2 than Pt/Al2O3; nevertheless, they could be effectively regenerated in the same way as Pt/Al2O3. Another beneficial aspect of Pt/BEA was that it regained NO oxidation activity faster than Pt/Al2O3 when stopping the exposure to SO2.