Multi-step separation of different chemical groups from the heavy fraction in biomass fast pyrolysis oil

Abstract The heterogeneity of the heavy fraction in bio-oil (HBO) causes serious problem for its downstream utilization. A multi-step method is thus proposed to separate different chemical groups from HBO. In this study, HBO from fast pyrolysis of poplar wood was collected and the characteristics of the HBO were investigated. A series of separation experiments was conducted on HBO, whose chemical groups were analyzed by chromatography coupled with mass spectrometry. The results show that through primary pH adjustment and CH2Cl2 extraction, HBO is divided into two fractions with fewer types of chemicals. After further distillation, HBO is separated into four fractions, whose primary chemical groups and their peak area percentages are ketones (89.5%), esters (49.9%), aromatic hydrocarbons (63.8%) and phenols (39.2%), respectively. These fractions can be used efficiently for either upgrading towards fuels or purification towards valuable chemicals. The findings in this paper is hoped to shed a light on solving the heterogeneity problem of bio-oil.