Date of Award
Spring 4-26-2022
Type
Thesis
Major
Master of Science
Degree Type
Master of Science
Department
Chemistry
First Advisor
Dr. Anil C. Banerjee
Second Advisor
Dr. Zewdu Gebeyehu
Third Advisor
Dr. Daniel Wade Holley
Abstract
The effects of sequence of impregnation (Pd on cerium oxides -alumina and cerium oxides on Pd-alumina) and calcination temperature (500 ℃ and 850 ℃) on the catalytic oxidation of methane under lean conditions were investigated. The catalysts were prepared by a combination of impregnation, slurry and vortexing methods. The catalysts had 4.7 wt.% Pd and 10.7 wt.% Ce based on inductively coupled plasma optical emission spectrometry (ICP-OES) analysis. The catalysts were characterized by pulse chemisorption, temperature programmed reduction (TPD), scanning transmission electron microscopy (STEM), and X-ray photoelectron spectroscopy (XPS). The activity of the catalysts for methane combustion was measured in a fixed-bed flow reactor by flowing a gas mix (0.98 vol % methane, 4.01 vol % and balance nitrogen) through a catalytic bed. The temperature of the catalytic bed was controlled by a temperature -controlled tube furnace. The % methane in the effluent gas mix was measured by a gas chromatograph fitted with a flame ionization detector and a ‘Carbon Plot’ column. Palladium was present as PdO and PdOx x>2+ and cerium as CeOx (+3 and +4 oxidation states) as per XPS analysis. The activity of the Pd/cerium oxides-alumina500C catalyst was higher than the cerium oxides/Pd-alumina500C catalyst at 250-500 ℃. Similar trends in the activity were seen for the two catalysts calcined at 850 ℃. Higher dispersion and lower particle size, and the presence of small Pd particles on alumina accounted for the higher catalytic activities of the Pd/cerium oxides-alumina500C and 850C catalysts. The lower activities of cerium oxides/Pd-alumina500C and 850C were primarily due to the embedment of Pd onto ceria due to strong PdO-CeOx interactions. This research implies that the sequence of impregnation and calcination temperature could alter catalytic properties and activity for methane combustion through PdO/PdOx -support interactions.
Recommended Citation
Park, Jihyeon, "Synthesis, Characterization and Activity of Palladium Catalysts on the Dual Support of Cerium and Aluminum Oxides" (2022). Theses and Dissertations. 468.
https://csuepress.columbusstate.edu/theses_dissertations/468
