Comparative study of the characteristics and activities of Pd/γ-Al 2 O 3 catalysts prepared by vortex and incipient wetness methods
72-h stability test, Catalytic activity, Metal-support interaction, Methane combustion, PdO-PdO /γ-Al O catalyst x 2 3, Steam deactivation, Vortex method
© 2019 by the authors. Licensee MDPI, Basel, Switzerland. 5 wt% Pd/γ-Al 2 O 3 catalysts were prepared by a modified Vortex Method (5-Pd-VM) and Incipient Wetness Method (5-Pd-IWM), and characterized by various techniques (Inductively coupled plasma atomic emission spectroscopy (ICP-AES), N 2 -physisorption, pulse CO chemisorption, temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), and X-ray diffraction (XRD)) under identical conditions. Both catalysts had similar particle sizes and dispersions; the 5-Pd-VM catalyst had 0.5 wt% more Pd loading (4.6 wt%). The surfaces of both catalysts contained PdO and PdO x with about 7% more PdO x in 5-Pd-VM. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and scanning electron microscope (SEM) images indicated presence of PdO/PdO x nanocrystals (8-10 nm) on the surface of the support. Size distribution by STEM showed presence of smaller nanoparticles (2-5 nm) in 5-Pd-VM. This catalyst was more active in the lower temperature range of 275-325 °C and converted 90% methane at 325 °C. The 5-Pd-VM catalyst was also very stable after 72-hour stability test at 350 °C showing 100% methane conversion, and was relatively resistant to steam deactivation. Hydrogen TPR of 5-Pd-VM gave a reduction peak at 325 °C indicating weaker interactions of the oxidized Pd species with the support. It is hypothesized that smaller particle sizes, uniform particle distribution, and weaker PdO/PdO x interactions with the support may contribute to the higher activity in 5-Pd-VM.
Banerjee, Anil C.; Golub, Kristina W.; Hakim, Md Abdul; and Billor, Mehmet Z., "Comparative study of the characteristics and activities of Pd/γ-Al 2 O 3 catalysts prepared by vortex and incipient wetness methods" (2019). Faculty Bibliography. 2790.