Hydrothermal liquefaction of lignin in near-critical water in a new batch reactor: Influence of phenol and temperature

The hydrothermal conversion of Kraft lignin (6 wt.%) in the presence of K2CO3 (1.7 wt.%) was studied as a function of temperature (T = 280-350 degrees C) and phenol mass fraction. (w(ph) = 0.0-9.7 wt.%). The process was carried out in a new batch reactor with injection of lignin slurry enabling fast heating of the biomass, effective control of reaction pressure, and withdrawal/quenching of the products. An aqueous phase and biocrude were obtained, both containing a broad spectrum of aromatic monomers and dimers. The former group consisted mostly of methoxybenzenes, guaiacols, catechols, and alkylphenols, while the latter included anisolic/phenolic dimers. For a given wph (3.4 wt.%), the total yield of monomeric aromatics (Y-T) was maximized at 320 degrees C. At T =300 degrees C and without phenol, YT was low, whereas it increased steeply up to w(ph) = 6.5 wt.%. (C) 2016 Elsevier B.V. All rights reserved.