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Bio-oil Production from Sweet Sorghum Bagasse Via Liquefaction Using Alkaline Solutions and Identification of Phenolic Products


The feasibility of converting biomass into bio-oil and the effect of an alkaline treatment during biomass liquefaction was studied. Sweet sorghum bagasse (SSB) was treated with NaOH concentrations of 0.5, 1.0, 3.0 and 6.0 M. The experiments were conducted in a temperature range of 260–320 °C in N2. The results showed that the alkaline treatment affected the product distribution of SSB liquefaction. The highest yield of bio-oil (53.2 wt%) and phenols extracted (≈ 40.0 wt%) were obtained at 320 °C and NaOH aqueous solution of 3.0 M. The ATR-FTIR results indicated the presence of carboxyl, ketone, ester and aromatic ring structures in the bio-oils. The absorption intensities of all the bio-oils at 1100 cm−1 (primary alcohols) substantially decreased with an increase in temperature and NaOH concentration. At given reaction temperature, the use of 3.0 and 6.0 M NaOH resulted in the extraction of more identifiable phenol derivatives than were obtained with the lower concentrations of NaOH. These results suggest that a temperature of 320 °C and a NaOH concentration of 3.0 M yields the best results among the temperatures and concentrations tested, and also that alkaline treatment is feasible for liquefaction and extraction of phenols from the bio-oil.

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The authors thank Dr. Roelf Venter for GC–MS analysis, and Dr. Nemera Shargie from the Agricultural Research Council, Grain Crops Institute, for the supply of sweet sorghum bagasse. The work presented in this paper is based on research financially supported by the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation of South Africa (Coal Research Chair Grant No. 86880, UID115228, Grant No. TP1208137225). Any opinion, finding, conclusion, or recommendation expressed in this material is that of the authors(s), and the NRF does not accept any liability in this regard.

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Correspondence to Thabo Z. Sehume.

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Sehume, T.Z., Strydom, C.A., Bunt, J.R. et al. Bio-oil Production from Sweet Sorghum Bagasse Via Liquefaction Using Alkaline Solutions and Identification of Phenolic Products. Waste Biomass Valor 11, 3593–3607 (2020).

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  • Liquefaction
  • Sweet sorghum bagasse
  • Bio-oil
  • Phenols
  • Alkaline treatment