Active oxygen center in oxidative coupling of methane on La2O3 catalyst
| Autor: | Zebang Liu, Evgeny I. Vovk, Yong Yang, Yaoqi Pang, Shenggang Li, Alexander P. van Bavel, Xiaohong Zhou |
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| Rok vydání: | 2021 |
| Předmět: |
Radical
Binding energy Energy Engineering and Power Technology chemistry.chemical_element 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology Photochemistry 01 natural sciences Peroxide Oxygen Methane 0104 chemical sciences Catalysis chemistry.chemical_compound Fuel Technology chemistry Electrochemistry Oxidative coupling of methane 0210 nano-technology Selectivity Energy (miscellaneous) |
| Zdroj: | Journal of Energy Chemistry. 60:649-659 |
| ISSN: | 2095-4956 |
| DOI: | 10.1016/j.jechem.2021.01.008 |
| Popis: | La2O3 catalyzed oxidative coupling of methane (OCM) is a promising process that converts methane directly to valuable C2 (ethylene and ethane) products. Our online MS transient study results indicate that pristine surface without carbonate species demonstrates a higher selectivity to C2 products, and a lower light-off temperature as well. Further study is focused on carbonate-free La2O3 catalyst surface for identification of active oxygen species associated with such products behavior. XPS reveals unique oxygen species with O 1 s binding energy of 531.5 eV correlated with OCM catalytic activity and carbonates removal. However, indicated thermal stability of this species is much higher than the surface peroxide or superoxide structures proposed by earlier computation models. Motivated by experimental results, DFT calculations reveal a new more stable peroxide structure, formed at the subsurface hexa-coordinate lattice oxygen sites, with energy 2.18 eV lower than the previous models. The new model of subsurface peroxide provides a perspective for understanding of methyl radicals formation and C2 products selectivity in OCM over La2O3 catalyst. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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