Highly Active and Thermally Stable Supported Pd@SiO2 Core–Shell Catalyst for Catalytic Methane Combustion

A series of Pd-based core–shell catalysts (Pd@SiO 2 , Pd@CeO 2 , and Pd@ZrO 2 ) supported on Si-modified Al 2 O 3 were prepared for the catalytic combustion of lean methane. Pd@SiO 2 exhibited slightly lower catalytic activity than Pd@CeO 2 and higher catalytic activity than Pd@ZrO 2 in dry conditions; however, Pd@SiO 2 had the highest catalytic activity among the three catalysts in the presence of high concentrations of water vapor. Furthermore, the Pd@SiO 2 catalyst showed good thermal stability and resistivity to water poisoning. CO chemisorption and TEM results demonstrated that the core–shell structure could help in the stabilization of the active phase compared to the uncoated Pd/Si-Al 2 O 3 catalyst. XRD and X-ray photoelectron spectroscopy results indicated that a balanced mixed phase of PdO x /Pd 0 is the main active phase of these Pd-based catalysts.