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Continuous gas phase methane oxidation using nitrous oxide over Fe-based zeolite

Chow, Ying Kit 2018. Continuous gas phase methane oxidation using nitrous oxide over Fe-based zeolite. PhD Thesis, Cardiff University.
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Abstract

This study investigates the direct continuous gas phase methane partial oxidation using nitrous oxide (N2O) over a range of Fe exchanged MFI framework catalysts. It has been shown that the required active species, namely α-oxygen can be generated over the biomimetic catalyst (Fe/ZSM-5) after heating treatment with N2O. The hydrogen abstraction step is followed to cleave the C-H bond to form methoy and hydroxy groups on the Fe sites. Investigating the influence of acid sites in continuous methane oxidation with N2O over Fe/ MFI zeolites revealed that Bronsted acidity of the Fe-zeolite catalyst supports the α-oxygen active species for the hydrogen abstraction to activate methane. The calcination treatment could cause a significantly decrease for both the Brønsted and Lewis acidity of Fe/ZSM-5 via the migration of aluminium as the catalyst treatment temperature increases. A substantial decrease is observed in catalytic performance following such alteration. The desired methanol could undergo further transformation to ethene follow by coke which is observed to behave similar to the methanol to olefin (MTO) reaction over zeolite framework. This side reaction path led to poor carbon balance and limited selectivity to partial oxygenates. The subsequent kinetic study on methane oxidation over 2 wt % Fe/ZSM-5 using N2O for both water-free and water-assisted (20 %) system has shown that the addition of water significantly improves methanol selectivity. A delplot technique was applied after performing a series of reactions using different catalyst mass for both system to identify the product rank of reaction products. Control experiments carried out in the absence of methane shown that the N2O decomposition rate also proceed similar to the full reaction mixture.

Item Type: Thesis (PhD)
Date Type: Submission
Status: Unpublished
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Date of First Compliant Deposit: 11 June 2019
Last Modified: 06 Nov 2019 13:32
URI: http://orca.cf.ac.uk/id/eprint/123369

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