Hierarchical zeolite enveloping Pd-CeO₂ nanowires: An efficient adsorption/catalysis bifunctional catalyst for low temperature propane total degradation

Volatile organic compounds (VOCs) are significant ozone (O₃) and particulate matter (PM) formation precursors and are deleterious to both human health and environment. Catalytic combustion can degrade VOCs to H₂O and CO₂ without secondary pollution, suggesting a potential sustainable technology for air pollution control. However, the concentration of exhausted VOCs is usually too low for effective decomposition. Herein, a novel adsorption/catalysis bifunctional catalyst, hierarchical silicalite-1 (S-1) zeolite enveloping Pd-CeO₂ nanowires (Pd-CeO₂NW@S-1), was designed and prepared using a simple one-pot two-step method and applied for the degradation of propane. Pd-CeO₂NW@S-1 exhibited superior catalytic activity (T₉₀ decreased to 296 °C) as well as increased thermal and hydrothermal stability (no obviously decrease in activity when treated at 700 °C or reacted with water gas, respectively) compared with Pd-CeO₂ nanowires supported on the outer surface of S-1 (Pd-CeO₂NW/S-1) and previously reported Pd based catalysts for propane degradation. In addition, the activity over Pd-CeO₂NW@S-1 after five reaction cycles just with little decrease and could be restored by a simple regeneration step and without any detection of coke. The remarkable performance over Pd-CeO₂NW@S-1 was attributed to the high dispersion of Pd and Ce encapsulated in hierarchical zeolite with superior propane adsorption performance and the special confinement structure according the Mars-van-Krevelen (MvK) mechanism. This confinement adsorption/catalysis bifunctional strategy can be used to design other high-performance catalysts for degradation of VOCs.