Capture and UV-Fluorescence Characterization of Primary Aerosols Ejected During the Fast Pyrolysis of Biomass in a Hot Plate Reactor

This study focuses on the collection and UV characterization of the bio-oil phase from primary aerosols ejected from the liquid intermediate phase during the fast pyrolysis of biomass in a hot plate reactor. The effects of the reactor pressure and aerosol-collecting surface temperature on the bio-oil yield and characteristics were evaluated. The study found that lower reactor pressures and a lower temperature of the collecting surface significantly enhanced the aerosol yield (up to 85%). UV-fluorescence was employed to assess the influence of these parameters on the light-to-heavy compound ratio (monomers vs. oligomers). The heavy fraction of bio-oil from the hot plate reactor was predominantly composed of dimers and trimers (340–370 nm), similar to pyrolytic lignin and the heavy fraction of the bio-oil, which also showed peaks in this range. In contrast, pyrolysis oils from auger and fluidized bed reactors displayed two peaks in the UV spectrum, with a maximum around 300 nm, indicating that they are mainly composed of light monomeric compounds. The UV characterization of the primary aerosols and the comparison with the UV spectra of the bio-oil and its fractions (light and heavy fraction and pyrolignin) revealed similar UV prints, highlighting the importance of aerosol ejection in the final composition of bio-oil.