- Title
- Effect of Desilication On the Catalytic Activity of Fe-FER For Direct, Selective, Partial Oxidation of Methane
- Creator
- Zhao, Guangyu; Yan, Penghui; Procter, Kerryn; Adesina, Adesoji; Jin, Yonggang; Kennedy, Eric; Stockenhuber, Michael
- Relation
- Journal of Catalysis Vol. 417, Issue January 2023, p. 140-152
- Publisher Link
- http://dx.doi.org/10.1016/j.jcat.2022.11.030
- Publisher
- Academic Press
- Resource Type
- journal article
- Date
- 2023
- Description
- The effect of desilication on the physic-chemical properties of ferrierite zeolite was investigated using spectroscopic and solid characterisation techniques including N2-adsorption, XRD, SEM, H2-TPR, NH3-TPD and in situ FTIR. Stability of active oxygen species formed from N2O over the Fe-FER catalysts and the catalytic activity for direct conversion of methane to value-added products at temperatures between 300 °C and 400 °C were studied. Ferrierite zeolites, pre-treated with 0.1 M, 0.2 M and 0.3 M NaOH solutions preserved the crystal structure of the ferrierite zeolite but their textural properties were significantly modified, leading to an increase in mesopore area and creating a greater concentration of terminal Si-OH groups, concomitant with increase in the amount of extra-framework Al and reduction in the number of bridging Si-OH-Al species. Batch-mode catalytic reaction studies of methane with N2O conducted in an in situ FTIR cell demonstrate that the methoxy groups formed on extraframework iron sites followed by the migration of these species to silicon defect sites, which resulted in a decline in the intensity of terminal Si-OH groups bands in the IR spectra. N2O-TPD experiments confirm that N2O is converted to N2, O2 and NO over Fe-FER catalysts at 350 °C. The decline in the desorption temperature of these products observed over Fe-FER catalysts treated with alkaline solution is consistent with a significant increase in the mesopore surface area from 28.3 m2/g to 102.4 m2/g. The peak areas of desorbed O2 and NO were estimated, and the different ratios of O2/NO observed on these catalysts appears to be related to the difference stabilities of surface oxygen species. Studies under continuous reaction conditions demonstrate that, at a similar level of methane conversion (ca. 2.8 %), Fe-FER catalysts prepared with the moderately alkaline solution (0.2 M NaOH) results the highest yield of methanol, dimethyl ether and formaldehyde. It is asserted that this enhanced selectivity is the result of the comparatively high concentrations of terminal silanol groups, Brønsted-acid sites, stability of active oxygen species and mesopore volume.
- Subject
- desilication; ferrierite zeolite; active oxygen species; terminal silanol groups; Brønsted-acid sites; mesopore
- Identifier
- http://hdl.handle.net/1959.13/1480433
- Identifier
- uon:50501
- Identifier
- ISSN:0021-9517
- Language
- eng
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