Thermally stable α-alumina supported ceria for coking resistance and oxidation of radical coke generated in-situ
| Autor: | Pradeep K. Agrawal, Liwei Li, Andrzej Malek, Christopher W. Jones, Hirokazu Shibata, Kehua Yin, Robert J. Davis, Micaela Taborga Claure, Shilpa Mahamulkar |
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| Rok vydání: | 2018 |
| Předmět: |
Materials science
General Chemical Engineering Oxide Energy Engineering and Power Technology chemistry.chemical_element 02 engineering and technology 010402 general chemistry complex mixtures 01 natural sciences Redox Catalysis chemistry.chemical_compound Organic Chemistry technology industry and agriculture Coke 021001 nanoscience & nanotechnology XANES respiratory tract diseases 0104 chemical sciences Cracking Fuel Technology chemistry Chemical engineering 0210 nano-technology Pyrolysis Carbon |
| Zdroj: | Fuel. 218:357-365 |
| ISSN: | 0016-2361 |
| DOI: | 10.1016/j.fuel.2018.01.001 |
| Popis: | A series of thermally stable α-alumina supported and unsupported ceria catalysts with varying composition is systematically investigated under realistic coke – catalyst contact conditions for the oxidation of in-situ generated coke during ethylene pyrolysis. These catalysts have been designed for use in high temperature applications of steam cracking. The textural and structural characterization of α-alumina supported ceria catalysts show the absence of solid oxide solutions, with the supported catalysts having distinct ceria domains on the alumina support. For comparison, two types of coke – catalyst contacting are explored: (i) tight contact by grinding industrial coke with catalyst and (ii) realistic in-situ contact, where coke is deposited on the catalytic support. During in-situ coke deposition, ceria-containing catalysts demonstrate resistance to coking as compared to the bare α-alumina support. Ceria and ceria – alumina composites also enabled coke oxidation at lower temperatures than the un-catalyzed coke oxidation. The presence of both Ce3+ and Ce4+ is confirmed by X-ray absorption near edge structure (XANES), consistent with the well-known redox capability of ceria catalysts. Kinetic studies revealed 50–80 mol% Ce as the best compositions for oxidation activity towards both industrial and in-situ coke. The catalytic activity correlates with the presence of reactive lattice oxygen atoms on ceria for both types of contact, indicating a similar mechanism of carbon oxidation under in-situ contact and tight contact conditions. A mechanism of reaction involving lattice oxygen of ceria is proposed for the oxidation of coke as well as for retardation of coke deposition on ceria domains. |
| Databáze: | OpenAIRE |
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