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Selective Production of Formic Acid by Wet Oxidation of Aqueous-Phase Bio-oil
journal contribution
posted on 2016-11-04, 20:43 authored by Niels Müller, Romina Romero, Héctor Grandón, Cristina SeguraFractionation of
bio-oil is an important step in the development
of an effective upgrading strategy of bio-oil to transport fuels and
chemicals because it reduces bio-oil complexity and side reactions;
however, the strategy should preferably make use of all fractions.
We therefore fractionated bio-oil from fast pyrolysis of pine wood
using water addition and liquid–liquid extraction and studied
its aqueous-phase oxidation to formic acid. One potential use of formic
acid is as a hydrogen source for upgrading of the organic phase. The
effects of the temperature, oxygen pressure, and concentration of
substrates and phenolic compounds on the yield and selectivity of
formic acid were investigated. Batch experiments revealed a yield
of up to 56 wt % (dry basis) and high selectivity, after 30 min at
170 °C and 5.0 MPa. However, the presence of phenolic compounds
in the aqueous phase and substrate concentrations greater than 3%
were detrimental. Extraction of the aqueous phase with butyl acetate
was effective for removing low-molecular-weight phenolic compounds
and enhanced reaction rate and yield. Intrinsic acidity of aqueous
bio-oil favored hydrolysis of anhydrosugars, but best results were
obtained with the addition of an acid catalyst (1.4 wt % sulfuric
acid). A low production of solids (<0.15 wt %) and gases (<1
wt %) makes wet oxidation a promising alternative for the processing
of aqueous-phase bio-oil. Estimated hydrogen production from formic
acid satisfied reported demands for catalytic hydrodeoxygenation of
the organic phase.