Thermochemical conversion of Datura stramonium L. by supercritical liquefaction and pyrolysis processes

Two thermochemical processes, namely supercritical liquefaction and slow pyrolysis, were used to produce bio-oils from Datura stramonium L. Liquefaction experiments were performed in a cylindrical reactor in organic solvents (isopropanol, acetone) under supercritical conditions with (zinc oxide, calcium hydroxide) and without catalyst at the temperatures of 275, 300 and 325 degrees C. Pyrolysis experiments were performed in a fixed-bed tubular reactor without and with same catalysts used in liquefaction at the temperatures of 400, 500 and 600 degrees C with a constant heating rate. The effects of process variables including temperature and catalyst on product yields were investigated. Product yields and composition of bio-oils were evaluated and compared for liquefaction and pyrolysis. The produced liquids at 300 degrees C in liquefaction and at 500 degrees C in pyrolysis were analyzed and characterized by elemental analysis, GC-MS and FT-IR. 102 and 87 different types of compounds were identified by GC-MS obtained in acetone and isopropanol, respectively, whereas pyrolysis liquids had 57 different types of compounds. Bio-oils from liquefaction were composed of various organics including aromatics, nitrogenated and oxygenated compounds, while phenolics were major compounds in pyrolysis liquids. Bio-oils obtained from liquefaction were found to have higher calorific values and superior fuel properties compared to pyrolysis bio-oils. (C) 2015 Elsevier B.V. All rights reserved.