Comparative Study of Biomass Fast Pyrolysis and Direct Liquefaction for Bio-Oils Production: Products Yield and Characterizations

The objective of this work is to compare two biomass-to-oil processes: fast pyrolysis and direct liquefaction, using the same biomass (beech sawdust). Fast pyrolysis is conducted in a cyclone reactor (wall temperature between 870 and 1040 K) and direct liquefaction in a 150-mL-autoclave reactor (bulk temperature between 420 and 600 K). Three fractions of pyro-oil are obtained from fast pyrolysis (heavy oil, light oil, and aerosol), whereas two fractions of liq-oil (heavy oil and water-soluble organics) are obtained from direct liquefaction. The comparison of both processes is based on the product yields and their characterization (ultimate analysis for solid and oils, oil–water content, gas and oil molecular composition, 1H NMR for oils). For both processes, there is an optimal temperature at which the oil yield is maximum. Up to 62.6 wt % of pyro-oil are obtained at 970 K with the cyclone reactor (with 25.7 wt % of gas and 11.7 wt % of solid), whereas 47.0 wt % of liq-oil was obtained at 573 K with the b...