Hydroprocessing of palm oil using Rh/HZSM-5 for the production of biojet fuel in a fixed bed reactor

The hydroprocessing of palm oil was performed in a continuous fixed bed reactor to produce biojet fuel. Rh/HZSM-5 was used as catalyst and was characterized by N₂ adsorption-desorption, x-ray diffraction (XRD), Scanning electron microscopy (SEM), NH₃-temperature programmed desorption (NH₃-TPD), and H₂-temperature programmed reduction (H₂-TPR). The effect of operating parameters including reaction temperature, molar ratio, and solvent on the yield of biojet and biodiesel was investigated. The catalyst deactivated rapidly in the solvent-free system due to carbon deposition. The application of 30% heptane in the feed maintained the conversion of palm oil above 90% for 8 hours. At 330°C, the yield of liquid fuel product was slightly less than that obtained at 300°C as more gaseous product was formed. The H₂-to-oil molar ratio of 158 at 300°C was insufficient to maintain the reaction at high conversion. At 300°C and a H₂-to-oil molar ratio of 316, the system was stable for the entire experimental period of 8 hours providing the biojet yield and selectivity of 15.3% and 28.5%, respectively. Although, this system was operated at a relatively low temperature for hydroprocessing, the productivity parameter of 0.60 kg product/Kg cat-h was significantly higher compared to the data provided in the literature. (author)