Title : Co-processing bio-oil in conventional refineries: A pathway to sustainable energy transition
Abstract:
The insertion of biogenic raw materials into conventional refineries is a promising option to increasing the green carbon content of traditional fuels and products. Co-processing low carbon footprint bio-oils with petroleum derivatives can be a faster way to decrease greenhouse gases emissions through small modifications in the oil refining existing infrastructure. However, the influence of bio-oil inclusion in the typical processes of conventional oil refineries is still understudied. This work aimed to perform individual chemical structural elucidation via comprehensive two- dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS) of liquid products from wood pyrolysis bio-oils (BO) co-processed with vacuum residue (VR) in two units: the delayed coking process and the pentane solvent deasphalting process. Effluents from delayed coking were obtained using three batch loadings: (A) 100% VR, (B) 95% VR and 5 % BO; and (C) 90% VR and 10 % BO. The effluents were then distilled, and three cuts were obtained: naphtha (up to 150 °C), light gasoil (150-380 °C), and heavy gasoil (+380 °C). The solvent deasphalting process was made by liquid-liquid extraction of BO and VR blend (1:1) with pentane at 65 ?C and 200 psi, and two fractions were produced: deasphalted oil and asphaltic residue. Using GC×GC-TOFMS, an advanced analytical tool, it was possible to identify at the molecular level the contribution of bio-oil in different traditional fossil streams. The biomass-derived carbon inclusion in the delayed coking batch promoted the reduction of alkane, olefin, and alkyl- thiophene concentrations in the effluents. Biogenic C1-alkyl-cyclopentenones (42.7 µg g-1) and C1-C3 alkyl- cyclopentenones (392.3 µg g-1) were detected in effluents B and C, respectively. These cyclic ketones from BO can be a good additive for fossil fuels, due to their high resistance to auto-ignition characteristics. After distillation, a greater BO contribution was observed in light gasoils. The pentane solvent deasphalting process extracts mainly the apolar compounds as aliphatic and aromatic hydrocarbons, whereas the mid-polar to polar ones are partitioned in both phases, with the low molecular mass polar compounds observed in a greater proportion in deasphalted oil. Thus, coprocessing BO with the VR inserted renewable molecules in the deasphalting fraction, which aims to recover lower molecular-weight fractions that can be used to produce valuable byproducts. Deasphalted oil containing green (or biogenic) carbon can be readily co-processed in FCC units, whereas the presence of renewable molecules in the asphaltic residue demonstrated an improvement in bioasphalt stability compared to petroleum asphalt cement. Thus, co-processing biomass-derived carbon in conventional oil refining steps increases the green carbon content and represents a viable pathway for a sustainable energy transition.
