期刊
ACS CATALYSIS
卷 6, 期 12, 页码 8127-8139出版社
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.6b01801
关键词
methane combustion; Pd; H-ZSM-5; surface acidity; Lewis acidity
资金
- National Key Research and Development Program of China [2016YFC0204300]
- National Basic Research Program of China [2013CB933201]
- National High Technology Research and Development Program of China [2015AA034603]
- NSFC of China [21171055, 21333003, 21303051, 21571061]
- Shu Guang Project of the Shanghai Municipal Education Commission [12SG29]
- Commission of Science and Technology of Shanghai Municipality [15DZ1205305]
- Shanghai Natural Science Foundation [13ZR1453000]
- Fundamental Research Funds for the Central Universities
- Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund (the second phase) for computing time
Pd/H-ZSM-5 catalysts could completely catalyze CH4 to CO2 at as low as 320 degrees C, while there is no detectable catalytic activity for pure H-ZSM-5 at 320 degrees C and only a conversion of 40% could be obtained at 500 degrees C over pure H-ZSM-5. Both the theoretical and experimental results prove that surface acidic sites could facilitate the formation of active metal species as the anchoring sites, which could further modify the electronic and coordination structure of metal species. PdOx interacting with the surface Bronsted acid sites of H-ZSM-5 could exhibit Lewis acidity and lower oxidation states, as proven by the XPS, XPS valence band, CO-DRIFTS, pyridine FT-IR, and NH3-TPD data. Density functional theory calculations suggest PdOx groups to be the active sites for methane combustion, in the form of [AlO2]Pd(OH)-ZSM-5. The stronger Lewis acidity of coordinatively unsaturated Pd and the stronger basicity of oxygen from anchored PdOx species are two key characteristics of the active sites ([AlO2]Pd(OH)-ZSM-5) for methane combustion. As a result, the PdOx species anchored by Bronsted acid sites of H-ZSM-5 exhibit high performance for catalytic combustion of CH4 over Pd/H-ZSM-5 catalysts.
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