Biojet Production from Hydroisomerization of Palm Olein Catalyzed by Ni/Micromesoporous Zeolite Composite Supports

This study investigated the catalytic performance of Ni-based catalysts supported on micromesoporous composites derived from the incorporation of SBA-15 with USY-(SBA-15-xUSY) or Hbeta-(SBA-15-xHbeta) zeolites (where x is wt percentage of zeolite fraction in the composite) for palm oil hydroisomerization to produce biojet fuel range. The hydroisomerization was conducted in a fixed-bed reactor under 25 bar of H2 pressure at 40 mL/min, 425 °C, 0.1 mL/min palm oil feed rate, and 5 g of catalyst. It was observed that the support materials significantly influenced catalytic activity and product selectivity. In the case of zeolite supports, the Ni-based catalysts supported by USY zeolite showed the highest liquid product yield (54.3 wt %) and iso-to-normal (i-/n-) alkane ratio of 1.43, whereas those supported on Hbeta zeolite provide the lower yield of liquid biofuel with high gasoline fraction (25.5%) and i-/n-alkane ratio of 2.58. The micromesoporous composite supports enhanced specific surface area and pore size to decrease the mass transfer limitation, resulting in better catalytic performance. The Ni/SBA-15-50USY and Ni/SBA-15-50Hbeta catalysts exhibited the highest selectivity to biojet fuel-range hydrocarbons, reaching 78.8 and 76.7 wt %, respectively. Moreover, the Ni/SBA-15-xHbeta catalyst promoted significantly higher selectivity to the iso-alkanes fraction in the obtained liquid biofuels than Ni/SBA-15-xUSY catalysts. The maximum i-/n-alkanes ratio at 3.45 was achieved for the system using Ni/SBA-15-30Hbeta catalyst, demonstrating the beneficial role of SBA-15 in boosting diffusion and catalytic efficiency. This result suggested that the integration of BEA zeolite crystals into the mesoporous SBA-15 structure allowed the closer proximity between the Ni-metal and Brønsted acid sites to optimize the hydrocracking efficiency for biojet fuel production.