On the understanding of bio-oil formation from the hydrothermal liquefaction of organosolv lignin isolated from softwood and hardwood sawdust

Conversion of organosolv lignins isolated with and without an inorganic acid catalyst (H2SO4) from hard- and softwood (birch and spruce) into bio-oil through hydrothermal liquefaction has been investigated. Furthermore, fractions of the isolated bio-oils were catalytically deoxygenated to improve the bio-oil properties. As elucidated through NMR, both biomass source and extraction mode influence the bio-oil product distribution. Depending on whether the lignins carry a high content of native structures, or are depolymerized and subsequently condensed in the presence of sugar dehydration products, will dictate heavy oil (HO) and light oil (LO) distribution, and skew the HO product composition, which again will influence the requirements upon catalytical deoxygenation. Organosolv fractionation of hard- and softwood is applied to obtain lignin substrates utilized for bio-oil production through hydrothermal liquefaction. The resulting bio-oil properties reflect the stemming lignin chemistries.