Effect of ceria on palladium supported catalysts for high temperature combustion of CH4 under lean conditions

Oxidative coupling of methane using microwave dielectric heating

“…The absence of lanthanum oxide peaks is indicative that this material has low crystallinity, which could arise either from a very small particle size or the existence of a thin layer of La 2 O 3 adsorbed on the ␥-alumina particles. This observation was in agreement with the previous studies on the La 2 O 3 /CeO 2 system [18,19].…”

“…At high temperatures, the conversion of ␣-alumina from ␥-alumina and the formation of CeO 2 /La 2 O 3 solid solutions have been suggested by other researchers [19,20]. However, these changes were not observed significantly in our XRD studies.…”

Development of Granular Catalysts and Natural Gas Combustion Technology for Small Gas Turbine Power Plants

“…There is still no consensus as to what form of oxidized palladium -bulk PdO, Pd with oxygen chemisorbed on its surface, or Pd particles covered by PdO -is the most active species in combustion ((McCarty, 1995;Burch, 1996;Su et al, 1998a;Su et al, 1998 b;Lyubovsky & Pfefferle, 1998;Lyubovsky & Pfefferle, 1999). Supporting of palladium on a substrate, primarily -or α-Al 2 O 3 or Al 2 O 3 modified with rare-earth metal oxides, raises the activity and thermal stability of the catalyst through an increase in the degree of dispersion of the active component and in its aggregation stability (Baldwin & Burch, 1990;Groppi et al, 1999, Ozawa et al, 2003, Liotta & Deganello, 2003Yue et al, 2005). Alternative catalytic systems for methane combustion are catalysts based on hexaaluminates and transition metal oxides.…”

Palladium-supported catalysts in methane combustion: comparison of alumina and zirconia supports

“…[1][2][3][4][5][6][7][8][9] Some reasons for this include: palladium-based catalysts are extremely active in methane oxidation which guarantees ignition at low temperatures (below 400 o C); palladium species formed under reaction conditions (up to 800 o C) present low volatility; these systems have the unique capability of temperature self-control associated with the reversible PdO (active)/Pd (inactive) transformation.…”

“…Among the various supports used, alumina and zirconia have been the most studied. 1,[3][4][5]9,11,13,[17][18][19][20][21][22][23][24] The support most commonly used for Pd catalysts is alumina and many studies focusing on Pd/alumina catalysts are available. 10,11,18 However, alumina is not fully stable at the high temperatures reached in methane combustion as it undergoes a phase change at 800 o C from γ-alumina to δ-alumina, resulting in a loss of surface area.…”