Co-pyrolysis characteristics of vacuum residue and pretreated woody biomass-derived pyrolysis oils under simulated delayed coking temperature and pressure

Integrating renewable carbon into existing petroleum refinery infrastructure is a promising strategy for the energy transition. This study investigates how bio-oil pretreatment and heating mode govern the co-pyrolysis of vacuum residue (VR) with commercial woody biomass pyrolysis oil (WBPO), dehydrated WBPO (dWBPO), and hydrotreated WBPO (hWBPO) under simulated delayed coking conditions. Under slow heating, co-pyrolysis of VR with 10 wt% dWBPO shifted condensable products toward heavy oil, reaching 136% of the additive prediction with only a slight increase in coke formation, whereas hWBPO favored hydrocarbon-rich light products. Direct-injection co-pyrolysis of VR/dWBPO increased light oil to 120% and reduced heavy oil to 50% of the predicted values. Petroleomics showed increased polar species with higher aromaticity and trace toluene-insoluble products during slow VR/dWBPO co-pyrolysis, although physical precipitation of heavy polar components cannot be excluded. High-temperature electron spin resonance showed radical concentrations close to additive predictions and slightly higher g -values, indicating a greater contribution from oxygen-containing radical environments without identifying specific radicals. These results demonstrate that WBPO pretreatment governs the chemical nature of interacting species, while heating history influences redistribution between light and heavy condensable fractions. These findings provide support evaluation of WBPO pretreatment and operating conditions for integration into delayed coking processes.