Methane Combustion Over Ni/CexZr1-xO2Catalysts: Impact of Ceria/Zirconia Ratio

A series of CexZr1-xO2(x=1, 0.83, 0.17, 0) supports and 2 wt.% Ni/Ce(x)Zr(1-x)O(2)catalysts were synthesized and evaluated for CH(4)oxidation. The Ce(x)Zr(1-x)O(2)supports showed moderate activity (T-50=519-638 degrees C) with CO by-product formation. Nickel incorporation onto Ce(x)Zr(1-x)O(2)lowered the T(50)to 438-477 degrees C and eliminated the formation of CO. The results indicated that moderate Zr doping improved the support oxygen storage capacity (OSC) and reducibility of the catalyst at low temperatures (H-2-TPR) leading to an enhanced CH(4)combustion turnover frequency: Ni/ZrO2<Ni/Ce0.17Zr0.83O2<Ni/CeO2<Ni/Ce0.83Zr0.17O2. The apparent activation energies of Ni/Ce(x)Zr(1-x)O(2)catalysts (87-92 kJ/mol) were much lower than the ones of Ce(x)Zr(1-x)O(2)supports and Ni/quartz sand (111-120 kJ/mol) indicating that CH(4)oxidation is facilitated when Ni is deposited on CexZr1-xO2. Moreover, stability tests with H2O and CO(2)showed that Zr doping can improve the catalyst stability, while H2O had a stronger reversible inhibition effect than CO(2)for CH(4)combustion.