Non-catalytic and catalytic fast pyrolysis of Schizochytrium limacinum microalga

In this study, fast pyrolysis of lipid-rich microalga, Schizochytrium limacinum, is carried out to evaluate the potential of deriving valuable chemicals and fuel molecules from this algae variety. The alga was characterized for its proximate and elemental composition, and heating value. The pyrolytic mass loss profiles of the alga were obtained from thermogravimetric analyzer, and the apparent kinetic parameters of degradation were evaluated using advanced isoconversional method of Vyazovkin. Fast pyrolysis experiments were performed in analytical pyrolyzer coupled with gas chromatograph/mass spectrometer. Long chain carboxylic acids, primarily tetradecanoic and hexadecanoic acids, were observed as the major pyrolysates in the temperature range of 350-650 degrees C in the absence of catalyst. A clear increase in production of aromatics and cyclic hydrocarbons was observed at high temperatures owing to the cracking of long chain hydrocarbon portion of the carboxylic acids. Catalytic fast pyrolysis was performed at 400 degrees C using zeolite Y-hydrogen (ZYH), zeolite Y-sodium (ZYNa), and oxides like MgO, ZrO2 and TiO2. The production of polyaromatic hydrocarbons and nitriles increased, while that of long chain carboxylic acids decreased with increasing acidity of ZYH. Increasing the loading of ZYNa resulted in the formation of long chain ketones. The formation of ketones was more pronounced with MgO and ZrO2 catalysts. The major ketones obtained include 16-hentriacontanone and 14-heptacosanone, which were formed via ketonization reactions of palmitic and myristic acids present in the algae. This study demonstrates that selective production of valuable chemical intermediates can be achieved from complex feedstocks like microalgae via catalytic fast pyrolysis using zeolites and metal oxides. (C) 2017 Elsevier Ltd. All rights reserved.