Integration of pyrolysis bio-oils of varying upgrading levels in FCC co-processing with VGO: Benefits and limitations

• Prior HDO enhances physicochemical traits and HVGO blending of pyrolysis oil. • Biogenic C in fuels at 80% conversion: 16% (FPBO) → 65% (SDPO) → 76% (HPO). • Severe HDO (HPO) cuts coke selectivity by 75%, extending catalyst lifetime. • Pre-treated oils (SDPO, HPO) mitigate FPBO’s negative effects in co-processing. • Beyond FCC deoxygenation, phenolic removal occurs via oligomerization and H-transfer. Fast Pyrolysis Bio-Oil (FPBO) and two biocrudes derived from it, a Stabilized and Deoxygenated Pyrolysis Oil (SDPO) and a near oxygen-free Hydrotreated Pyrolysis Oil (HPO), were co-processed independently with a Heavy Vacuum Gas Oil (HVGO) feed in a transported-bed reactor (MicroDowner Unit, MDU) over a commercial FCC equilibrium catalyst. This study examines the influence of bio-oil upgrading severity, incorporation ratio (5–50 wt%), and catalyst-to-oil ratio (CTO = 5–30 g/g) on conversion, product distribution, coke formation, and deoxygenation pathways under typical industrial FCC conditions aimed at maximizing middle distillates. At low blending levels (≤ 10 wt%), upgraded bio-oils had minimal effect on overall conversion and liquid yields; however, FPBO severely deactivated the catalyst even at 5 wt%. Increasing the upgrading severity of pyrolysis oil (FPBO → SDPO → HPO) reduced coke selectivity by up to 75%, preserved gasoline (C 5 –C 12 ) and kerosene (C 10 –C 18 ) yields, and enhanced biogenic carbon recovery into liquid fuels (from 16% for FPBO to 65% for SDPO and 76% for HPO at 80% conversion). In all cases, deoxygenation proceeded primarily via dehydration during FCC coprocessing (>90% for SDPO and HPO). However, for FPBO, due to its different oxygenated-compound composition, decarboxylation and decarbonylation mechanisms also contributed significantly. It has been found that phenol derivatives are the most refractory among the oxygenated compounds in pyrolysis oil and are not efficiently removed during preliminary upgrading or catalytic cracking, leading to their accumulation in the recovered liquid products even after FCC processing. Altogether, this study clearly indicates that pretreatment of pyrolysis bio-oil, such as deep hydrodeoxygenation, is essential to ensure seamless integration into existing FCC operations and to maximize renewable carbon incorporation into drop-in fuels.