Comparative Study of the Characteristics and Activities of Pd/γ-Al2O3 Catalysts Prepared by Vortex and Incipient Wetness Methods

Catalysts

Md.Abdul Hakim¹  AnilC. Banerjee²  MehmetZ. Billor²  KristinaW. Golub³ 

[1] Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA;Department of Chemistry, Columbus State University, Columbus, GA 31907, USA;;School of Chemical &

关键词: methane combustion;    PdO-PdO_x/γ-Al₂O₃ catalyst;    vortex method;    catalytic activity;    steam deactivation;    72-h stability test, metal-support interaction;   

DOI  :  10.3390/catal9040336

来源: DOAJ

【 摘 要 】

5 wt% Pd/γ-Al₂O₃ 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), N₂-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.

【 授权许可】

Unknown