Smith, Louise R., Smith, Paul J., Mugford, Karl S., Douthwaite, Mark, Dummer, Nicholas F. ![]() ![]() ![]() ![]() ![]() |
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Abstract
Aqueous glycerol solutions of up to 50 wt% were reacted over magnesium oxide catalysts at temperatures greater than 300 °C, the reactivity of which was compared to catalyst-free reactions. Under catalyst-free conditions, modest levels of dehydration to hydroxyacetone were observed at temperatures >400 °C in a steel reactor tube and >320 °C over silicon carbide. For reactions over MgO, the product distribution becomes more diverse, resulting in the formation of methanol, acetaldehyde, ethylene glycol, 1,2-propanediol and acetic acid. The methanol space–time–yield over MgO catalyst samples (0.5 g) was found to be highest at 400 °C (205 g h−1 kgcat−1) with a 50 wt% solution of glycerol, or with a glycerol concentration of 10 wt%; 255 g h−1 kgcat−1 over 0.1 g of catalyst. Despite the high glycerol conversion achieved, the MgO catalyst was found to be stable over 48 h, following a modest decrease in glycerol conversion during the initial 2 h of reaction. Post-reaction characterisation revealed that the level of coking at high glycerol conversions (>90%) was ≥120 mg gcat−1. The carbon mass balance determined by GC analysis for a typical reaction was 75% and so the carbon lost from catalyst coking only represents a modest quantity of the missing carbon; typically <10%. MgO was also found to promote the formation of high molecular weight products via condensation reactions, which were responsible for the remainder of the missing carbon; ca. 15%. Therefore, the total organic content of the post-reaction mixture and coke was calculated to be 94% of the starting solution. We conclude that the catalyst surface directs the formation of methanol, however, the results indicate that the reaction conditions are crucial to obtain optimum yields.
Item Type: | Article |
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Date Type: | Publication |
Status: | Published |
Schools: | Chemistry Cardiff Catalysis Institute (CCI) |
Publisher: | Royal Society of Chemistry |
ISSN: | 2044-4753 |
Funders: | EPSRC |
Date of First Compliant Deposit: | 15 March 2019 |
Date of Acceptance: | 7 February 2019 |
Last Modified: | 11 Oct 2023 19:14 |
URI: | https://orca.cardiff.ac.uk/id/eprint/120750 |
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