Palladium species in Pd/H-ZSM-5 zeolite catalysts for CH4-SCR
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- Kikuchi, E. & Ogura, M. Res. Chem. Intermed. (2000) 26: 55. doi:10.1163/156856700X00084
The active state of palladium for NO reduction with methane (CH4-SCR) was investigated by comparing the catalytic activity of Pd/H-ZSM-5 with that of PdO/SiO2. High catalytic activity for CH4-SCR was given by Pd/H-ZSM-5 in the temperature range of 300–500 °C. PdO/SiO2 catalyzed the reaction between NO2 and CH4 in the absence of oxygen, which retarded the reaction by consuming CH4 in combustion. CH4 combustion occurred on either zeolite-supported or silica-supported catalyst, while NO preferentially retarded the combustion on Pd/H-ZSM-5. NO was found to be chemisorbed on the palladium sites in zeolite, while it was hardly chemisorbed on PdO/SiO2. NaCl titration showed that the palladium species in zeolite are Pd2+ cations content, on which NO is strongly chemisorbed resulting in high selectivity for CH4-SCR.