Mechanistic study of liquid phase glycerol hydrodeoxygenation with in-situ generated hydrogen

• Published in: Journal of catalysis Vol. 368; pp. 98 - 111
• Main Authors: Yfanti, V.-L., Lemonidou, A.A.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.12.2018
• Subjects: 1,2-Propanediol; Glycerol hydrodeoxygenation; In-situ IR; Mechanism; Methanol reforming; Glycerol hydrodeoxygenation; 1,2-Propanediol; In-situ IR; Methanol reforming; Mechanism
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2018.09.036

[Display omitted] •Methanol aqueous phase reforming (APR) is used as the H2 donor reaction.•H2 formation proceeds via consecutive methanol dehydrogenation-WGS reaction.•Cu:Zn:Al selectively catalyzes glycerol hydrodeoxygenation-methanol APR reaction.•The first step of glycerol hydrodeoxygenation depends on hydrogen availability.•Hydroxyacetone is the main intermediate for 1,2-propanediol formation. The mechanism of the liquid phase glycerol hydrodeoxygenation–methanol reforming tandem reaction cycle over a Cu:Zn:Al catalyst is investigated. The hydrogen needed is provided in-situ via methanol reforming. In–situ DRIFTS of adsorbed methanol proved that methanol reforming proceeds via sequential methanol dehydrogenation to CO and further conversion to CO2 via water gas shift reaction. High hydrogen formation rate is achieved by increasing methanol to glycerol molar ratio. The elucidation of reaction pathways using mechanistic tests and in-situ IR spectroscopy showed that the first step of glycerol hydrodeoxygenation depends on hydrogen availability. Glycerol hydrodeoxygenation proceeds mainly via dehydration-hydrogenation route with hydroxyacetone as the main intermediate product. However at low methanol/glycerol molar ratio, the simultaneous formation of 1,2-propanediol via glyceraldehyde route cannot be excluded. 1,2-propanediol is stable product with low rate of further hydrodeoxygenation to 1-propanol. Though at low selectivities, ethylene glycol is the main degradation byproduct formed via direct hydrogenolysis of glycerol.