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Gas-phase conversions of glycerol to methanol over ceria-based catalysts

Smith, Louise R. 2020. Gas-phase conversions of glycerol to methanol over ceria-based catalysts. PhD Thesis, Cardiff University.
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Abstract

The conversion of aqueous glycerol feedstocks to methanol has been investigated in the gas phase using metal oxide catalysts, at atmospheric pressures and in the absence of an external reductant. Whilst preliminary investigations included catalyst free conditions and the use of MgO, most studies were performed with CeO2. A complex product distribution was obtained over all catalysts, with hydroxyacetone identified as the major intermediate in the conversion of glycerol to methanol. Investigations into the carbon balance showed the presence of high molecular weight products, likely formed through condensation reactions, highlighting the difficulty in selectively converting concentrated glycerol feedstocks. The use of ceria nanostructures with different exposed surface planes showed a strong dependency between product distribution and ceria surface, with the (111) surface found to be beneficial for methanol productivity. A significant increase in previously reported methanol STYs, with a 50 wt.% glycerol feedstock, was obtained over a polyhedral ceria nanostructured catalyst, with a value of 201 gMeOH h-1 kg-1cat, corresponding to 24.5 % methanol selectivity. Additionally, mechanistic differences across the catalysts showed a strong correlation existed between high hydroxyacetone STYs at low conversion and high methanol STYs at high conversion. The addition of copper and cobalt dopants did not improve the selectivity towards methanol at high conversion, despite the increase in hydroxyacetone at low conversion, particularly over CuCeOx. This was likely due to the conversion of methanol leading to an increased selectivity to CO and H2. Whilst the addition of dopants were not beneficial to methanol production, they were beneficial for the conversion of glycerol to acetaldehyde and H2, which could provide an alternative route for glycerol valorisation.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Cardiff Catalysis Institute (CCI)
Chemistry
Subjects: Q Science > QD Chemistry
Date of First Compliant Deposit: 9 June 2021
Last Modified: 09 Jun 2021 15:11
URI: http://orca.cardiff.ac.uk/id/eprint/141825

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