Abstract
Thermochemical liquefaction characteristics of Spirulina, a kind of high-protein microalgae, were investigated with the sub- and supercritical ethanol as solvent in a 1000
mL autoclave. The influences of various liquefaction parameters on the yields of products (bio-oil and residue) from the liquefaction of Spirulina were studied, such as the reaction temperature (
T), the
S/
L ratio (
R
1, solid: Spirulina, liquid: ethanol), the solvent filling ratio (
R
2) and the type and dosage of catalyst. Without catalyst, the bio-oil yields were in the range of 35.4
wt.% and 45.3
wt.% depending on the changes of
T,
R
1 and
R
2. And the bio-oil yields increased generally with increasing
T and
R
2, while the bio-oil yields reduced with increasing
R
1. The FeS catalyst was certified to be an ideal catalyst for the liquefaction of Spirulina microalgae for its advantages on promoting bio-oil production and suppressing the formation of residue. The optimal dosage of catalyst (FeS) was ranging from 5–7
wt.%. The elemental analyses and FT-IR and GC–MS measurements for the bio-oils revealed that the liquid products have much higher heating values than the crude Spirulina sample and fatty acid ethyl ester compounds were dominant in the bio-oils, irrespective of whether catalyst was used.