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

• Datura stramonium L. was converted to bio-oils by liquefaction and pyrolysis processes.
• Effects of temperature and catalysts on product yields were investigated.
• Use of catalysts increased both conversions and bio-oil yields.
• The compositions of bio-oils were analyzed and compared.
• Bio-oils obtained from liquefaction were found to have higher calorific values.

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 °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 °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 °C in liquefaction and at 500 °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.

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