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

Abstract

Abstract 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.