Highly Dispersed Pd Species Supported on CeO2 Catalyst for Lean Methane Combustion: The Effect of the Occurrence State of Surface Pd Species on the Catalytic Activity

The correlation between the occurrence state of surface Pd species of Pd/CeO2 for lean CH4 combustion is investigated. Herein, by using a reduction-deposition method, we have synthesized a highly active 0.5% PdO/CeO2-RE catalyst, in which the Pd nanoparticles are evenly dispersed on the CeO2 nanorods CeO2-R. Based on comprehensive characterization, we have revealed that the uniformly dispersed Pd nanoparticles with a particle size distribution of 2.3 ± 0.6 nm are responsible for the generation of PdO and PdxCe1−xO2−δ phase with –Pd2+–O2−–Ce4+– linkage, which can easily provide oxygen vacancies and facilitate the transfer of reactive oxygen species between the CeO2-R and Pd species. As a consequence, the remarkable catalytic activity of 0.5% Pd/CeO2-RE is related to the high concentration of PdO species on the surface of the catalyst and the synergistic interaction between the Pd species and the CeO2 nanorod.

Relationship between penta-coordinated Al3+ sites in the Al2O3 supports and CH4 combustion activity of Pd/Al2O3 catalysts

Pd/Al2O3 catalysts were prepared using various Al2O3 supports with different structural features, revealing a significant insight into the methane (CH4) combustion activity of Pd nanoparticles with the fraction of penta-coordinated Al3+ sites in the Al2O3 supports.

Plasma-induced construction of defect-enriched perovskite oxides for catalytic methane combustion

Perovskite oxides have been considered as appropriate alternatives to precious metal catalysts in CH4 combustion due to their excellent activity and sintering-resistance capacity. Herein, an innovative plasma-induced strategy was employed...

Improvement of Methane Combustion Activity for Pd/ZrO2 Catalyst by Simple Reduction/Reoxidation Treatment

The improvement of methane combustion activity was observed in cyclic temperature-programed and isothermal reactions over Pd/ZrO2 catalysts by simple reduction/reoxidation treatment. The catalytic activity increased during the initial stages of isothermal reaction, and the light-off temperature was lowered as the number of cycles increased in the cyclic temperature-programed reaction. To reveal the origin of activation, variations in the reduction properties after the activation period were carefully investigated through CH4 temperature-programed reduction (TPR) measurements. From the CH4-TPR results, it was confirmed that the reduction temperature decreased significantly after activation. The observation of the CH4-TPR peak at relatively low temperatures is directly proportional to the catalytic activity of CH4 combustion. It was therefore concluded that repeated reduction/reoxidation occurred in the reactant stream, and this phenomenon allowed the combustion reaction to proceed more easily at lower temperatures.

Improvement of Methane Combustion Activity for Pd/ZrO2 Catalyst by Simple Reduction/Re-oxidation Treatment

The improvement of the methane combustion activity was observed in cyclic temperature-programmed and isothermal reactions over Pd/ZrO2 catalysts by simple reduction/re-oxidation treatment. The catalytic activity increased during the initial stages of isothermal reaction, and the light-off temperature was lowered as the number of cycles increased in the cyclic temperature-programmed reaction. To reveal the origin of activation, variations in the reduction properties after the activation period were carefully investigated through CH4 temperature-programmed reduction (TPR) measurements. From the CH4-TPR results, it was confirmed that the reduction temperature decreased significantly after activation. The observation of the CH4-TPR peak at relatively low temperatures is directly proportional to the catalytic activity of CH4 combustion. It was therefore concluded that repeated reduction/re-oxidation occurred in the reactant stream, and this phenomenon allowed the combustion reaction to proceed more easily at lower temperatures.