Effect of ethanol on Mulberry bark hydrothermal liquefaction and bio-oil chemical compositions

The aim of the study was to investigate hydrothermal liquefaction of Mulberry bark in sub-critical ethanol-water co-solvents (S-C-E-W) (50:50, v/v) and sub-critical water (S-C-W) with K2CO3 as catalyst at fixed condition (300 °C and 60 min). The derived bio-oil was analyzed by FTIR and GC-MS, FTIR and XRD were used to characterize Mulberry bark and the solid residues. The results showed that liquefaction efficiency of Mulberry bark was higher in S-C-E-W (95.72 wt %) than that in S-C-W (87.5 wt%), and the bio-oil yield was a little more in S-C-E-W (30.32 wt %) than that in S-C-W (28.81 wt%), although the yield of the heavy oil (HO) varied little (26.16% in S-C-E-W, 26.25% in S-C-W), and the yield of the light oil (LO) was very low (4.16% in S-C-E-W and 2.56% in S-C-W). There was small difference between the higher heating values. The bio-oil components were complex, mainly contained phenols, aromatic, alkanes, ketone, esters, furans, nitrogen compounds, etc. The content of phenols in the bio-oil derived in S-C-W was more than that derived in S-C-E-W, and HO derived in S-C-E-W contained higher content of ester components. The liquefaction of Mulberry bark can be enhanced by ethanol.