Deoxygenation of Bio-oil during Pyrolysis of Biomass in the Presence of CaO in a Fluidized-Bed Reactor

The direct deoxygenation effect of CaO on bio-oil during biomass pyrolysis in a fluidized-bed reactor was studied. Bio-oils were produced from white pine in the presence and absence of CaO at 520 °C and a carrier gas flow rate of 50 L/min (standard temperature and pressure). The results showed that the oxygen content of the organic components in the bio-oils was 39, 39, 39, 36, 32, and 31 wt % for white pine alone and white pine accompanied with CaO at CaO/biomass mass ratios of 1, 2, 3, 4 and 5, respectively. At a CaO mass ratio of 5, the relative reduction of oxygen content in the bio-oil reached 21%. Detailed gas chromatography−mass spectrometry analysis showed that the relative abundances of high oxygen content laevoglucose, formic acid, and acetic acid were highly reduced by CaO, indicating direct fixation of “the active quasi-CO 2 intermediates” produced during biomass pyrolysis. Furthermore, the relative abundances of furfural, furfuryl alcohol, etc., mainly derived from dehydration reactions, all increased, showing that CaO addition could also catalyze dehydration reactions. X-ray diffraction and Fourier transform infrared analyses of the solid residues prepared by a thermal balance confirmed the direct fixation of the active quasi-CO 2 intermediates and showed that some organic calcium salts appeared at 350 °C, which would decompose below 400 °C to form easily regenerated CaCO 3 . This further confirmed the feasibility of CaO recycling for in situ deoxygenation of bio-oil.