- Title
- Comparison of direct, selective oxidation of methane by N₂O over Fe-ZSM-5, Fe-Beta, and Fe-FER catalysts
- Creator
- Zhao, Guangyu; Benhelal, Emad; Adesina, Adesoji; Kennedy, Eric; Stockenhuber, Michael
- Relation
- The Journal of Physical Chemistry Part C Vol. 123, Issue 45, p. 27436-27447
- Publisher Link
- http://dx.doi.org/10.1021/acs.jpcc.9b04388
- Publisher
- American Chemical Society
- Resource Type
- journal article
- Date
- 2019
- Description
- In this study, the activity and selectivity to Fe-ZSM-5, Fe-Beta, and Fe-FER catalysts were studied at 350 °C for the partial oxidation of methane using N2O as oxidant. Spectroscopic and solid characterization tools including H2-TPR, in situ IR, N2 gas adsorption, CO chemisorption, and TGA-MS were used in the investigation. Ammonia adsorption data suggested that among the studied zeolites, H-FER zeolite contained the highest concentration of framework Al atoms, which are essential for the formation of active extra-framework Fe species. The oxidation state and redox active species of Fe-ZSM-5, Fe-Beta, and Fe-FER catalysts were studied by H2-TPR, which disclosed the presence of a unique reduction peak (originating from N2O pretreatment) centered at approximately 235 °C over the samples. The hydrogen consumption peak was more prominent over Fe-FER than other catalysts, demonstrating that the Fe-FER catalyst contained more active sites for N2O conversion in comparison to Fe-Beta and Fe-ZSM-5 catalysts. For IR spectra of NO adsorbed on the Fe zeolites, a band at 1874 cm–1 with a shoulder at 1894 cm–1 was observed over the three catalysts, suggesting the presence of extra-framework Fe clusters in ion exchange positions. We demonstrated these clusters are acting as active sites for the oxidation of methane with N2O. Bands of methoxy groups were observed in FTIR profiles of CH4 and N2O adsorbed on Fe-FER, Fe-ZSM-5, and Fe-Beta catalysts at 350 °C. Over Fe-FER, the concentration of silanol-bonded methoxy groups accounted for over 95% of all methoxy groups under all the reaction conditions studied. In comparison, for the Fe-ZSM-5 and Fe-Beta catalysts, the proportion was less than 80%. The catalytic activity studies showed that Fe-FER was the most active catalyst based on methane and N2O conversion, and displayed the highest selectivity to C1-oxygenates and dimethyl ether formation, while Fe-ZSM-5 obtained the highest selectivity to ethylene among the three catalysts. Fe-ZSM-5 was found to deactivate significantly due to coke formation.
- Subject
- hydrocarbons; alcohols; adsorption; zeolites; catalysts
- Identifier
- http://hdl.handle.net/1959.13/1421798
- Identifier
- uon:37767
- Identifier
- ISSN:1932-7447
- Language
- eng
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