Investigation of the Reaction Pathways of Biomass‐Derived Oxygenate Conversion into Monoalcohols in Supercritical Methanol with CuMgAl‐Mixed‐Metal Oxide

Reaction pathways for the conversion of cellulose into C2–C6 monoalcohols by supercritical methanol depolymerization and hydrodeoxygenation (SCM‐DHDO) over a CuMgAl oxide catalyst have been elucidated using a range of model compounds. SCM‐DHDO of intermediate oxygenates including glycerol, methyl la...

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Bibliographic Details
Published in:ChemSusChem 2018-12, Vol.11 (23), p.4007-4017
Main Authors: Galebach, Peter H., Thompson, Sean, Wittrig, Ashley M., Buchanan, J. Scott, Huber, George W.
Format: Article
Language:English
Subjects:
Alcohol
biomass
Cellulose
Chemical reactions
Cleavage
Condensates
Conversion
Coupling (molecular)
C−C coupling
Dehydration
Dehydrogenation
Depolymerization
Dihydroxyacetone
Diols
Esterification
Esters
fuels
hydrodeoxygenation
Methanol
Molecular weight
Supercritical fluids
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Summary:Reaction pathways for the conversion of cellulose into C2–C6 monoalcohols by supercritical methanol depolymerization and hydrodeoxygenation (SCM‐DHDO) over a CuMgAl oxide catalyst have been elucidated using a range of model compounds. SCM‐DHDO of intermediate oxygenates including glycerol, methyl lactate, and 1,2‐ethanediol produces similar products as those produced from the SCM‐DHDO of cellulose. The pathway to C2–C6 monoalcohols occurs through rapid C−C coupling reactions between methanol and diols followed by C−C scission between vicinal alcohol groups to produce two monoalcohols. Methyl‐branched monoalcohols are produced through a methyl shift in a secondary diol followed by dehydration. Esters are produced by dehydrogenative coupling between an adsorbed methoxy and a primary alcohol. Both dehydrogenation to a ketone and esterification to a methyl ester are in equilibrium with the corresponding alcohol and were reversible. Dehydration of diols is the slowest observed reaction and not a main pathway to monoalcohols. SCM‐DHDO of glucose, dihydroxyacetone, and cellulose all produced similar high molecular weight species indicating that condensation of intermediates can produce undesired side products. The scissions, the scissions: Cellulose is converted into alcohols over CuMgAlOx catalyst in supercritical methanol. The reaction proceeds through retroaldol condensation of cellulose to oxygenates, condensation with methanol, and C−C scission reactions to monoalcohols (see scheme).
ISSN:1864-5631
1864-564X
DOI:10.1002/cssc.201801816