Pyrolysis of a Naturally Dried Botryococcus braunii Residue

Abstract

The extant chlorophyte microalga Botryococcus braunii is a potential source of biofuel. In any future biofuel plant, it may be dried and stockpiled after harvesting and then pyrolyzed to generate oil. To investigate the formation of bio-oil from B. braunii, its naturally occurring residue known as coorongite was pyrolyzed non-isothermally and isothermally under about 1 atm of pure nitrogen carrier gas. The apparent pyrolysis activation energy of coorongite (25 kJ/mol) is much lower than those of most kerogens, which are on the order of 130–250 kJ/mol. However, it approaches that reported for a Moroccan marine oil shale, implying similarities in their responses to pyrolysis. Non-isothermal pyrolysis by thermogravimetry coupled with infrared spectroscopy (TG–IR) revealed coorongite to contain a significant amount of alkanes. Molecular analysis of the isothermal pyrolysates by gas chromatography–mass spectrometry (GC–MS) identified a homologous series of normal alkanes and alkenes (C9–C21), normal ketones (C...