Abstract
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•Thermochemical liquefaction of COC was a prominent process for producing bio-oil.•Type of solvent affected the yield and composition of bio-oil considerably.•Liquefaction of COC in SCEL at 300°C was preferred for producing bio-oil.
Thermochemical liquefaction of Camellia oleifera cake (COC) for producing bio-oil was conducted in supercritical methanol (SCML), ethanol (SCEL) and acetone (SCAL), respectively. GC–MS, elemental analysis and ICP-OES were used to characterize properties of bio-oil. Results showed that thermochemical liquefaction of COC was a prominent process for generating bio-oil. Increase of temperature was beneficial to the increase of bio-oil yield, and yield of bio-oil followed the sequence of SCAL>SCEL>SCML. In spite of the highest bio-oil yield, the lowest calorific value and highest contents of Zn, Pb, Cd, Ni, Fe, Mn, and Cr were found in bio-oil from SCAL. Though SCML has very similar bio-oil composition and calorific value with SCEL, higher bio-oil yield and lower contents of heavy metals could be obtained with SCEL, especially in bio-oil from SCEL at 300°C. Moreover, the origin of ethanol could make the bio-oil product totally renewable. Therefore, liquefaction of COC in SCEL at 300°C could have great potential in generating bio-oil.