Fast pyrolysis oils (bio-oil/biofuel) were derived from woody biomass, which undergoes rapid heating in the absence of oxygen. Though the liquid bio-oils hold potential as carbon neutral fuels, they can be viscous, unstable and need to be upgraded to be used as transportation fuels. Understanding the reactions that cause aging is crucial to prevent aging processes. Our chemical analysis identified aldehydes, trihydroxy alcohols and conjugated aromatics that react away during accelerated aging. To understand the chemical reactions responsible for bio-oil aging, we augmented oils with reactive precursors and characterized reaction products using 1D and 2D NMR spectroscopy and LC/MS/MS. Based on our findings, we suggest an acid catalyzed quinone methide reaction mechanism to account for the reactivity of coniferyl alcohol with formaldehyde to form the dimeric structure. A nucleophilic addition of coniferyl alcohol with the carbonyl carbon of the protonated formaldehyde leads to ring closing by the attack of the alcohol group on the conjugated double bond. Subsequent C-C bond formation between the intermediate and another coniferyl alcohol (quinine methide form) at the γ-position leads to the formation of the dimeric product.<br/>

Chemical reactions and structural identification of a coniferyl alcohol dimer causing instability in wood-derived pyrolysis oils

253rd National Meeting (2017)

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