On the development of active and stable Pd–Co/γ-Al2O3 catalyst for complete oxidation of methane

Low-Temperature Activity and PdO-PdOx Transition in Methane Combustion by a PdO-PdOx/γ-Al2O3 Catalyst

“…Figure 5 gives the contrast HAADF and Bright-field STEM images of PdO/PdO x and γ-Al 2 O 3 ; these images demonstrate that the support is crystalline and contains nanosize particles. Our STEM data on average particle sizes are close to the particle size of 10 nm for a PdO/γ-Al 2 O 3 catalyst [3,22] and 5 nm for a Pd-Co/γ-Al 2 O 3 catalyst [7].…”

“…XPS is widely used in catalytic research for identifying surface compounds and their composition [3,7,9,10]. An important objective of this research is to find out the change in surface composition of the catalyst before and after methane combustion and to identify the active phases in the catalytic reaction.…”

“…Gholami and Smith [5] prepared Pd/SiO 2 catalysts by the incipient wetness method and reported 50% conversion at 550 • C and 100% at 600 • C. Goodman et al [6] developed a Pd/γ-Al 2 O 3 catalyst that converted 90% methane at 400 • C, but only 30% at 325 • C. Several researchers have also used other precursors and supports for the combustion of methane. Stefanov et al [7] reported a Pd-Co/γ-Al 2 O 3 catalyst with 70% methane conversion at 400 • C; Ercolino et al [8] developed a Pd/Co 3 O 4 catalyst on ZrO 2 open cell foam, and the catalyst converted about 90% methane at 325 • C and 100% at 400 • C. Cargnello et al [9] used a supramolecular approach to develop a novel Pd@CeO 2 /hydrophobic-Al 2 O 3 core-shell catalyst that converted 50% methane at 325 • C and 100% at 400 • C. A Pd/Ceria nanocatalyst supported on alumina and prepared by the solution combustion method showed 50% activity at 300 • C and 90% at 400 • C [10]. A nanozeolite silicalite-1 coating on cordierite catalyst and a nitrogen-modified perovskite-type composite catalyst converted 90% methane at 350 • C [11,12].…”

“…The nature and identity of the active phase in Pd catalysts during methane combustion is currently under dispute [2,6,7,9,[18][19][20][21]. Several researchers recognize PdO as the active phase [2,6,7,9]; some advocate for Pd [18,19], and others for the Pd to PdO ratio [20,21].…”

“…Several researchers recognize PdO as the active phase [2,6,7,9]; some advocate for Pd [18,19], and others for the Pd to PdO ratio [20,21]. Another consideration is the possibility of the support lending its constituents to the catalytic active site during the course of the reaction [20].…”