Catalytic hydrothermal liquefaction of D. tertiolecta for the production of bio-oil over different acid/base catalysts

In this article, two acid catalysts (ZrO2/SO42− and HZSM-5) and two base catalysts (MgO/MCM-41 and KtB) were used in catalytic hydrothermal liquefaction (HTL) of Dunaliella tertiolecta (D. tertiolecta) for the production of bio-oil. The results indicated that the acid/base property of the catalyst plays a crucial role in the catalytic HTL process, and the base catalyst is conducive to the improvement of conversion and bio-oil yield. When KtB was used as the catalyst, the maximum conversion and bio-oil yield was 94.84 and 49.09 wt %, respectively. The detailed compositional analysis of the bio-oil was performed using thermogravimetric analysis, elemental analysis, FT-IR, and GC-MS. The compositional analysis results showed that the introduction of catalyst is beneficial for reducing the fixed carbon content in the bio-oil, and the structure of catalyst influences on the bio-oil composition and boiling point distribution. Based on our results and previous studies, the probable catalytic HTL microalgae model over various catalysts can be described that the main chemical reactions include ketonization, decarboxylic, dehydration, ammonolysis, and so forth. with HZSM-5 and MgO/MCM-41 as the catalyst; the cyclodimerization, decomposition, Maillard reaction, and ketonization are the main reactions with ZrO2/SO42− as the catalyst; the dehydration, ammonolysis, Maillard reaction, and ketonization can occur with KtB as the catalyst. Therefore, a plausible reaction mechanism of the main chemical component in D. tertiolecta is proposed. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1118–1128, 2015