Second-generation green diesel from castor oil: Development of a new and efficient continuous-production process

•Green diesel was obtained in 95.3% purity and 98.4% relative yield.•Secondary reactions of castor oil were suppressed using two-stage continuous system.•Green diesel met most of specifications of European standard EN 590.•Green diesel blend with petro-diesel met specifications for CFPP of diesel grade B.

A new continuous process for the selective production of castor-oil green diesel was developed, leading to 95.3% purity and ca. 98% relative yield. Castor oil was hydrotreated in fixed-bed continuous reactors, with one or two stages, using NiMo/Al2O3 as catalyst. It was demonstrated that performing the process in a single hydrotreating bed the presence of hydroxyl groups in castor oil afforded secondary reactions that led to low values of purity and yield. Running the reactions in a two-stage continuous system allowed to remove, in the first bed at 270 °C, hydroxyl groups and unsaturations before the deoxygenation of the carboxylic groups in the second bed at 350 °C, improving in this way the purity and the yield considerably. Physicochemical properties of the so-obtained product met most of the specifications of the European standard EN 590 but the CFPP. Blending of green diesel (20% vol) with petro-diesel satisfied CFPP specifications for diesel grade B.

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