Bio-oils produced from algae by applying thermal processes are a promising source of sustainable, low greenhouse gas alternative fuels. These thermal treatment processes are also well suited to decentralized energy production due to low capital and operating costs. However, the oils are viscous, reactive, and thermally unstable. To analyze the effects of different thermal production methods on bio-oil stability an accelerated aging study was performed. Bio-oils were obtained from Scenedesmus dimorphus algae by three different thermal methods: hydrothermal liquefaction, fast pyrolysis, and catalytic pyrolysis. Next, the bio-oils were aged at 80 �C for 24 hours and 2 weeks. Elemental analysis, viscosity, FTIR, 1H and 13C NMR, TGA, and MALDI-TOF were used to analyze the aging process and its relation to the bio-oil production method. The fast pyrolysis and catalytic pyrolysis bio-oils had initial molecular weights of approximately 800 amu while the hydrothermal liquefaction oil had an initial molecular weight of 975 amu. After accelerated aging for 24 hours at 80�C, the two pyrolysis bio-oils molecular weight increased by approximately 80 amu. However, the hydrothermal liquefaction bio-oil molecular weight increased by more than 160 amu, nearly double the increase that the fast pyrolysis and catalytic pyrolysis oils went through. Viscosity of the hydrothermal liquefaction bio-oil also increased substantially in comparison to the two pyrolysis oils and after two weeks the hydrothermal liquefaction bio-oil was completely solid. Characterization analyses indicated that unsaturation, and not oxygen content, played the most significant role in viscosity changes during aging or storage.

Aging study of algae bio-oils produced by different methods

248th National Meeting (2014)

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