New insights in the fractionation of Pinus pinaster wood: sequential autohydrolysis, soda ethanol organosolv and acidic precipitation

•Pine wood was fractionated into hemicellulosic liquors, cellulosic pulp and lignin.•Up to 51 wt.% hemicelluloses, 66 wt.% cellulose and 77 wt.% lignin were recovered.•Pulps had cellulose, hemicellulose and lignin contents >90 wt.%, 3 wt.% and 5 wt.%.•Recovered lignin fractions presented purities >97 wt.%.•The three-steps fractionation shows potential towards a biorefinery-based economy. Pinus pinaster wood (PPW) was fractionated by two different routes: (1) a two-steps system by soda ethanol organosolv (SEOS) followed by lignin precipitation (LP) and (2) a three-steps procedure encompassing autohydrolysis (AH) followed by SEOS and LP. In the two-steps route, the effect of ethanol mass fraction in the cooking liquor (15-55 wt.%) on pulps and lignins purities was studied. In the three-steps system, the effects of AH temperature (160-180 °C) and reaction time (30 and 60 min) on hemicelluloses removal were evaluated. Then the effects of AH temperature (175 and 180 °C) and ethanol concentration (15-35 wt.%) on SEOS derived pulps and lignins purities were considered. The SEOS reaction temperature (170 °C) and time (90 min) were kept constant in all SEOS experiments. In the case of the two-steps approach, pulps with lignin and hemicellulose contents as low as 6 and 15 wt.% (respectively), as well as precipitates having lignin contents up to 94 wt.% were obtained. Up to 81 wt.% of the cellulose and 66 wt.% of the lignin initially present in PPW were recovered in pulps and precipitates (respectively) by this fractionation pathway. When the three-steps fractionation was applied, up to 17 wt.% of the original biomass was recovered in AH liquors. Pulps having hemicellulose contents as low as 3 wt.% and lignin contents as low as 5 wt.% were produced by sequential AH and SEOS, while LP products presented lignin contents higher than 98 wt.%. The results show the potential of the three-steps fractionation towards a biorefinery-based bioeconomy.