Fractionation and catalytic upgradation of crude tall oil into sustainable transportation fuels via blending and co-refining

Abstract

The integration of biogenic non-edible oils into conventional fuels is a lucrative pathway to lower the carbon intensity of the transportation industry. This study investigates the emerging co-refining potential of tall oil fatty acids when blended with conventional oil refinery streams before hydrotreatment and distillation to produce high-quality low-carbon transport fuels. Among refinery integration points, the strong miscibility of tall oil fatty acids with unifiner hot feed highlights the feasibility of seamless tall oil fatty acid integration into existing infrastructure. Hydrotreatment using NiMo and CoMo catalysts effectively upgraded the tall oil fatty acid–unifiner hot feed blends, increasing heating values by up to 9.4% from the original blend and achieving high values (45.4–47.9 MJ kg⁻¹), while significantly reducing oxygen content from 12.2 wt% in tall oil fatty acid to 0.2 wt% in the final NiMo-treated diesel fraction. Both catalysts were effective, with NiMo exhibiting higher deoxygenation activity, while CoMo had higher selectivity for lower volatility fuel products. The resulting distillate fractions exhibited improvements in deoxygenation, viscosity, density, and total acid number (TAN), with kerosene fractions demonstrating particularly desirable fuel properties when compared to ASTM and European fuel standards. However, the TAN, viscosity, density, and sulphur content of select gasoline and diesel fractions presented a challenge, necessitating adjustment of these property deviations through further development of this refinement pathway to meet increasingly stringent specifications. Overall, the measured behaviour and microscopic imaging showed that the fuel products of this study were comparable to those available commercially. Advancing the utilization of bio-derived feedstocks like TOFA can contribute to reducing dependence on fossil fuels and achieving long-term net-zero emissions goals for Canada.