Investigation On The Preparation Of Biodiesel From Microalgae Oil

The purpose of this study is to find high efficient microalgae resource for the preparation of biodiesel, and the investigation was carried out systematically in the following four aspects: optimized cultivation of microalgae, extraction and analysis of microalgae oil, discussion on the cultivation conditions for the microalgae with high-content oil, preparation and properties of biodiesel from the microalgae oil. The results of the research are summarized as follows:Three strains of microalgae, Chlorella spp, Chlorella sorokiniana and Chlorella vulgaris, were incubated under different conditions to determine their suitable culture conditions. The results show that the optimized cultivation conditions for the microalgae are: BG11 as medium, inoculation density 0.25 (OD_540nm), initial pH8, temperature 25℃,light intensity 3500⁴500lux, and NH₂CONH₂ as nitrogen source but its suitable dosage for above three strains of microalgae is 0.125g/l, 0.0625g/l and 0.125g/l, respectively.Solvent extraction is more efficient for extracting lipid from microalgae, and its highest yield is obtained when petroleum ether/ethyl ether (2:1, v/v) solution is used to extract for 5h at 40℃.The lipid content of microalgae was measured to determine the suitable cultivation conditions for the lipid-accumulation. GC-MS and GC were employed to determine the composition of fatty acids and their content in three strains of microalgae. The results demonstrate that the major components of fatty acids in three strains of microalgae are C16 and C18 fatty acids.Regarding both propagation and lipid-accumulation, we determined the optimum culture conditions of microalgae. Among the three strains of microalgae, Chlorella spp is the one with the highest content of lipid. The optimum culture conditions of Chlorella spp are: initial pH 8, temperature 25℃, light intensity 3500lux, and NaNO3 as nitrogen source and N content 0.25g/l. Under the optimum conditions, the lipid content of microalgae is up to 43.7%.Biodiesel was prepared from the microalgae oil through methyl esterification reaction with methanol. The properties of the resulting biodiesel were measured, and it was confirmed to fulfill the biodiesl standards of GB/T 20828-2007 and ASTM 6751-03.