Fractional conversion of microalgae from water blooms
Fractional conversion of natural algae Cyanobacteria from Taihu Lake (TLA) was conducted. The raw TLA and pretreated samples were pyrolyzed at 290 oC and 450 oC according to the TGA results. The extraction of lipids or saccharides from TLA was performed as pretreatment to obtain lipid extracted algae (LEA) or saccharide extracted algae (SEA). The total yields of bio-oil from fractional pyrolysis were 40.9 wt % from TLA, 42.3 wt % from LEA, and 48.5 wt % from SEA, respectively. From TLA, the major components of bio-oil were fatty acids, amides and hydrocarbons (heptadecane) at 290 oC whereas those at 450 oC were phenols and C10-C15 hydrocarbons. After the lipid extraction, acids, amides and indoles accounted for a large proportion at 290 oC, while the main products obtained at 450 oC were phenols, indoles and pyrroles. It is worth mentioning that the yield of bio-oil from LEA increased, and the composition of bio-oil was simplified. Moreover, the average molecular weight of bio-oil obtained from LEA went down. Interestingly, the extraction of saccharides inhibited the pyrolysis of lipids, so the distribution of bio-oil from SEA changed a little. The fractional pyrolysis of pretreated microalgae not only increased the bio-oil yield but also improved the quality of bio-oil.