Gas-phase conversion of glycerol to methanol over magnesium oxide catalysts

Mugford, Karl S. 2022. Gas-phase conversion of glycerol to methanol over magnesium oxide catalysts. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

The gas phase conversion of aqueous glycerol feedstocks to methanol has been investigated over a series of MgO catalysts, conducted at atmospheric pressure and in the absence of external reductants. MgO catalysts with characteristics altered by varying the preparation heat treatment temperature were studied. Glycerol reactions were carried out over the samples. The samples exhibited a complex product distribution. Major products observed included hydroxyacetone, ethylene glycol, acetaldehyde, acrolein and methanol. Gaps in the carbon mass balance occurred the catalysts. These were proposed to be due to high weight molecular products, which can form via bi-molecular condensation reactions. Promotion of condensation reactions was linked to strong O 2- basic sites on MgO. These are proposed to readily dissociate water, which can lead to hydroxylation of the sites in-situ. It was theorised that the hydroxylation of the catalysts surface promoted glycerol conversion and condensation reactions, due to substrate stabilisation. The catalyst treated at 650 °C was found to not require the dissociation of water to activate glycerol and exhibited more coke than the other samples. This was proposed to be linked to its morphology which differed from the others, resulting in a less prominent ratio of the O2- sites. This sample exhibited a high carbon mass balance over all conditions tested. This was concluded to be due to it suppressing the formation of high weight molecular products. The high carbon balance resulted in a higher yield to the identified products. The catalyst exhibited a higher methanol STY of 93 g h-1 kg cat-1 than the other catalysts tested. Finally, reactions investigating the mechanism were conducted using intermediates products. It was concluded that hydroxyacetone and glycolaldehyde C-C bond cleavage was unlikely to be the primary route to methanol. Instead, it is proposed to be the initial homolytic C-C cleavage of glycerol.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Chemistry
Date of First Compliant Deposit:	8 June 2022
Last Modified:	08 Jun 2022 13:57
URI:	https://orca.cardiff.ac.uk/id/eprint/150283

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