Effects of vapor-/solid-phase interactions among cellulose, hemicellulose and lignin on the formation of heavy components in bio-oil during pyrolysis.

The vapor-/solid-phase interactions are the inevitable phenomenon in biomass pyrolysis process, which significantly affects the formation of heavy components (molecular weight > 200 Da) in bio-oil (HCO). In this study, to deeply understand the mechanism of the formation of HCO during biomass pyrolysis, the effects of the vapor-/solid-phase interactions among cellulose, hemicellulose, and lignin (biomass three components) on the formation of HCO during pyrolysis were studied in a fixed-bed reactor system. The HCO were analyzed by the FT-ICR MS spectrometer and the UV-F spectrometer. The results showed that the vapor-phase interactions mainly promoted the formation of heavy phenolic compounds at a slow heating rate, and the total content of HCO was increased. The vapor-phase interactions decreased the total content and the O content of HCO obviously at a fast heating rate; meanwhile, the highly reactive compounds (e.g., furans, acids, and ketones) generated from the pyrolysis of cellulose and hemicellulose could interact with the phenol monomers. Thus the phenolic compounds were transformed into large aromatic compounds via the vapor-phase interactions. The solid-phase interactions facilitated the transformation of O-containing structures of the HCO into the char via cross-condensation reaction, decreasing the yield of HCO, especially the phenolic compounds and the saccharides. • Vapor-/solid-phase interactions affect the heavy components formation in bio-oil. • Effects of vapor-/solid-phase interactions vary with the changes in heating rate. • Vapor-/solid-phase interactions affect the primary and secondary reaction pathways. • Interactions are hard to bring new O-/H-structures into the heavy components. [ABSTRACT FROM AUTHOR]