Continuous hydroprocessing of microalgae biodiesel to jet fuel range hydrocarbons promoted by Ni/hierarchical mesoporous Y zeolite catalyst

To simulate the industrial production of jet fuel range hydrocarbons, the hydroprocessing of Nannochloropsis oceanica microalgae biodiesel over a nickel-based hierarchical mesoporous Y (meso-Y) zeolite catalyst in a continuous process was investigated. The goal was to optimize two of the key parameters involved in hydroprocessing process, i.e., the reaction temperature and feedstock injection rate, to improve the biodiesel conversion and product selectivity, especially to iso-alkanes. A microalgae biodiesel conversion of 91.5% with a selectivity to jet fuel range hydrocarbons of 56.2% was obtained for a feedstock injection rate of 0.02 mL/min at 275 °C over Ni/meso-Y zeolite catalyst (total acid density = 3.08 mmol/g and BET surface area = 599.57 m2/g) in a fixed bed continuous hydroprocessing system. In addition, an isomerization ratio of 46.4% was achieved and attributed to the optimized reaction conditions, as well as to the shape selectivity exhibited by the catalyst. XRD performed for the used catalyst revealed unchanged crystallinity of the zeolite while a sintering process was noted for Ni nanoparticles whose crystallite size increased from 25 to 54 nm during hydroprocessing at 275 °C. FTIR detected functional groups of CH2 (final saturated hydrocarbons), CHO (intermediate aldehydes), and CC (intermediate olefins), which were generated over catalyst after reactions. SEM and EDS showed that carbon element (22.9 wt%) uniformly distributed over catalyst after reaction at 275 °C due to efficient conversion.