Investigation of chemical modifications of micro- and macromolecules in bio-oil during hydrodeoxygenation with Pd/C catalyst in supercritical ethanol

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>Miscanthus bio-oil was subjected to hydrodeoxygenation (HDO) with Pd/C at different temperatures (250, 300 and 350°C) and times (30, 45 and 60min) to investigate the chemical modification of micro- and macromolecules in bio-oil. Four main products – char, gas and two immiscible oils (light and heavy oil) – were obtained from the HDO reaction. Yields of heavy oil as a targeting product of HDO varied from 60% to 13%, whereas those of gas and char were ranged from 7% to 36% and 6% to 17%, respectively. Water content was estimated to<1% and heating value was 26–31MJkg<SUP>−1</SUP>.</P> <P>Reduction of unstable oxygen-containing compounds such as acids (2-hydroxy-butanoic acid), aldehydes (furfural), alcohols (butanedial) and sugars (levoglucosan) were characteristic in heavey oil. Apart from hydrogenation and deoxygenation, micromolecules in bio-oil were plausibly modified to stable ketones, esters and saturated components via demethoxylation, dealkylation, decarbonylation, dehydroxylation and ring opening.</P> <P>Macromolecular lignin fragments (referred to as pyrolytic lignins in bio-oil and phenol polymers in heavy oil) were extracted and subjected to several analyses. Approximately 60% of the pyrolytic lignins were decomposed into low molecular weight compounds during HDO reaction. Moreover, essential functional groups, OCH<SUB>3</SUB> and phen-OH groups attached to pyrolytic lignin, were severely modified during HDO reaction.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Miscanthus bio-oil was subjected to hydrodeoxygenation in the presence of Pd/C. </LI> <LI> Structural modification of chemical components in bio-oil was investigated. </LI> <LI> Reduction of unstable oxygen-containing components were characteristic. </LI> <LI> Micromolecules were modified to stable ketones, esters and saturated components. </LI> <LI> Depolymerization of macromolecular lignins were verified during hydrodeoxygenation. </LI> </UL> </P>