Hydrotreatment of Algal Oil to Sustainable Aviation Fuel Over Base Metal Catalysts

The catalytic conversion of algal oil to sustainable aviation fuel (SAF) was investigated in this study using in-house synthesized NiMo/HY and NiMo/HZSM-5 catalysts. Experiments were initially conducted with canola oil in a single-stage and two-step process (hydrodeoxygenation and subsequently cracking and isomerization) to evaluate the performance of both catalysts, before testing with algal oil. NiMo/HZSM-5 led to higher yields of cycloalkanes, iso-alkanes and aromatics, and lower yields of olefins compared to NiMo/HY and was selected as the better performance catalyst for optimization studies of SAF production from algal oil. H2/feed ratio, temperature, pressure and liquid hourly space velocity (LHSV) process parameters were optimized in a two-step hydroconversion process using commercial sulfided NiMo/γ-Al2O3 catalyst for the hydrodeoxygenation process, and the in-house synthesized NiMo/HZSM-5 catalyst for the cracking and isomerization step. Optimal process conditions for the HDO process were determined tobe 1000 SmL/mL, 900 psig H2, 400 °C and 0.5 h–1 LHSV which prolonged catalyst life and increased the yield of jet-range alkanes. Optimal process conditions for the cracking and isomerization step were: 3000 SmL/mL, 700 psig H2, 310 °C and 0.5 h–1 LHSV which reduced excessive cracking in the reactor and favored the formation of iso- and cyclo- alkanes thus leading to an improvement of the quality of the jet fuel. At the optimized process conditions, the overall yield obtained was about 47% (∼6.9% iso-alkanes, ∼6.6% aromatics, ∼4.3% cyclo-alkanes, ∼24.7% linear alkanes and ∼4.7% olefins) which is higher than most values in literature.