Separation of BTX chemicals from biomass pyrolysis oils via continuous flash distillation

Abstract

Partially deoxygenated pyrolysis oils, such as those produced by tail gas reactive pyrolysis (TGRP), show promise for use in biorefineries if they can integrate into standard refinery operations, one of which is distillation. A feasible method for modeling the process and for removing aqueous components will advance progress. This study investigated the potential of continuous flash distillation for fractionating partially deoxygenated bio-oil component chemicals benzene, toluene, and xylene (BTX), which are critical feedstocks for producing many refinery products. A model bio-oil mixture was used to evaluate process performance, and process conditions were investigated with respect to separation efficiency (temperature = 120, 130, and 140 °C; input flow rate = 2 or 3 mL min−1). Mean BTX yield (gout gin−1) for an oil flow rate of 2 mL min−1 ranged between 0.134 and 0.222 gout gin−1, while for 3 mL min−1 yields ranged from 0.135 to 0.400 gout gin−1. In all treatments, the measured amounts of BTX from model bio-oil were less than those from ASPEN simulations. From the distillates, aqueous fractions phase separated while sequestering acetic acid from the organics. Residence time within the drum was positively correlated with concentration of BTX in the distillates. At no point did solid residues form within the flash drum. When compared with analogous experiments at optimal conditions, BTX yields from real TGRP oil were comparable but less than the analogous model experiment. These results suggest that continuous, atmospheric pressure distillation of low-oxygen bio-oils can be used for separating commodity, refinery-grade chemicals such as BTX from biomass pyrolysis-derived bio-oils.