Methane Combustion Over Ni/CexZr1–xO2 Catalysts: Impact of Ceria/Zirconia Ratio

Abstract

AbstractA series of CexZr1–xO2 (x=1, 0.83, 0.17, 0) supports and 2 wt.% Ni/CexZr1–xO2 catalysts were synthesized and evaluated for CH4 oxidation. The CexZr1–xO2 supports showed moderate activity (T50=519‐638 °C) with CO by‐product formation. Nickel incorporation onto CexZr1–xO2 lowered the T50 to 438–477 °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 (H2‐TPR) leading to an enhanced CH4 combustion turnover frequency: Ni/ZrO2<Ni/Ce0.17Zr0.83O2<Ni/CeO2<Ni/Ce0.83Zr0.17O2. The apparent activation energies of Ni/CexZr1–xO2 catalysts (87‐92 kJ/mol) were much lower than the ones of CexZr1–xO2 supports and Ni/quartz sand (111‐120 kJ/mol) indicating that CH4 oxidation is facilitated when Ni is deposited on CexZr1–xO2. Moreover, stability tests with H2O and CO2 showed that Zr doping can improve the catalyst stability, while H2O had a stronger reversible inhibition effect than CO2 for CH4 combustion.