Novel iron molybdate catalysts for the oxidative dehydrogenation of methanol and propane

Pitchers, Jack 2023. Novel iron molybdate catalysts for the oxidative dehydrogenation of methanol and propane. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Novel iron molybdate catalysts were formed from amorphous precursors prepared via supercritical antisolvent (SAS) precipitation. The iron molybdate catalysts were tested for the selective oxidative dehydrogenation of methanol to formaldehyde and the selective oxidative dehydrogenation of propane to propene. Initial development of novel iron molybdates found the influence of water as a cosolvent for SAS precipitation to have a significant effect on the chemical structure of the catalyst, forming carbonates. A definitive screening design was undertaken to uncover the influence of four parameters (water cosolvent content, metal precursor concentration, pressure and solution flow rate) as well as the interdependence between the parameters, with the mapping of cross terms shown for the first time for binary metal oxide precursors. Of particular interest was the use of water as a cosolvent, which has been largely unexplored in literature. The use of a definitive screening design also made it possible to compare the relative strength of the parameters compared to one another on specific catalyst precursor properties, measured via a range of characterisation techniques, including FT-IR, SEM, TGA, MPAES and N2 physisorption. Varying four parameters for SAS precipitation led to different catalyst precursor properties and therefore, a range of iron molybdates were formed with varying physiochemical properties after calcination. Characterisation techniques such as N2 physisorption, H2-TPR, XRD, SEM, TEM, and XPS were undertaken. The physiochemical properties were related to the performance of the catalysts for the selective oxidative dehydrogenation of methanol to formaldehyde. The catalysts were found to be selective and exhibited a higher productivity than catalysts shown in literature for similar Fe:Mo ratios. Isoconversion studies showed that specific iv productivity depended on the mean uncalcined agglomerate size of the SAS precipitates and the mass loss measured during calcination. The same structure-property relationships were found for the oxidative dehydrogenation of propane to propene. This was uncovered by normalising the specific oxygen activity, which was found to strongly influence the propane activity and overoxidation. However, it was found that propene productivity did not vary with O2 activity, with the propene productivity showing a linear relationship for time online studies. This suggested the bulk properties relating to redox rate influenced the performance for the oxidative dehydrogenation of propane within the set of catalysts formed.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Chemistry
Funders:	EP/L016443/1 EPSRC
Date of First Compliant Deposit:	9 July 2024
Last Modified:	09 Jul 2024 15:37
URI:	https://orca.cardiff.ac.uk/id/eprint/170458

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