Development of partial oxidation catalysts for the indirect internal reforming (IIR) of methane in solid oxide fuel cells (SOFC)

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Milner-Elkharouf, Lois (2019). Development of partial oxidation catalysts for the indirect internal reforming (IIR) of methane in solid oxide fuel cells (SOFC). University of Birmingham. Ph.D.

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Abstract

Two nickel catalysts were prepared, each adopting a silica support for different functions. One catalyst consisted of silica spheres onto which nickel nanoparticles were anchored with nickel phyllosilicate bonds (Ni/SiO\(_{2, sph}\)). The other catalyst adopted a core@shell configuration whereby nickel nanoparticles were coated in an inert silica shell (Ni@SiO\(_2\)). Bare nickel nanoparticles, with no silica coating, were also prepared to assess the role of the silica shell in the Ni@SiO\(_2\) system. The catalysts were characterised by electron microscopy, TGA, XRD, XPS, and surface area analysis. Performance of the catalysts for the partial oxidation of methane was assessed using a gas chromatograph. Methane conversion, and H\(_2\), CO, and CO\(_2\) product yields were used as performance indicators.

Key findings of the work which add to the understanding of nickel-silica catalysts presented in literature are as follows. Increased nickel loading was shown to improve the activity of the Ni/SiO\(_{2, sph}\) catalyst when the catalyst was tested at high GHSV. Nickel particle agglomeration and carbon deposition were both observed in the tested catalysts, and the extent of degradation increased with nickel loading. The SiO\(_2\) shell was shown to be critical in preventing the re-oxidation and redox cycling of active nickel species in the Ni@SiO\(_2\) system. This catalyst suffered from nickel particle agglomeration due to an incomplete SiO\(_2\) coating. However, the catalyst resisted carbon deposition completely.

For the first time, both catalysts were incorporated into an alumina hollow fibre bundle in an attempt to demonstrate indirect internal reforming within a solid oxide fuel cell. The Ni/SiO\(_{2, sph}\) catalyst readily re-oxidised on the alumina fibre thus losing its catalytic activity, whereas the Ni@SiO\(_2\) catalyst performed well. Indirect internal reforming by partial oxidation was demonstrated as a feasible method of producing syngas to be consumed in a solid oxide fuel cell. This is particularly of interest as the method could be applied to on-board or domestic systems, were direct internal or external reforming might not be feasible.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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