Hydrotreatment of sunflower oil using supported molybdenum carbide

Pure sunflower oil was hydrotreated (T = 633 K, P = 5 MPa) aiming the production of a biofuel in the diesel range using β-Mo2C/Al2O3 as catalyst. The catalyst was synthesized in situ using the temperature-programmed carburization (TPC) methodology with a 20% (v/v) CH4/H2 gas mixture and 923 K/2 h as synthesis temperature. The catalytic evaluation results indicate that for the employed conditions n-C18 was the major product. The association of the results of the experiments without (blank) and with catalyst suggests that the overall triglyceride transformation into linear alkanes proceeds in two steps: (i) thermal cracking of the triglyceride forming free fatty acids and (ii) hydrogenation of the double bonds and of the carboxylic group of the free fatty acid forming n-alkanes. No CO and/or CO2 formation were detected implying that decarbonylation and/or decarboxylation routes do not play an important role when molybdenum carbide is used, contrarily to what is commonly observed when supported Co–Mo or Ni–Mo sulfides are employed as catalysts.

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► The activity of Mo2C/Al2O3 in the hydrotreating of sunflower oil was evaluated.
► Mo2C/Al2O3 promotes deoxygenation of the carboxyl of the free fatty acids.
► The by-product of the reaction is water.
► Little contribution of decarbonylation and decarboxylation was observed.
► Mo2C/Al2O3 is stable in reaction times greater than 150 h.