Bio-oil production from sweet sorghum bagasse via liquefaction using alkaline solutions and identification of phenolic products

Abstract

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