Identification of a Polycyclic Aromatic Hydrocarbon Indicator for the Onset of Coke Formation during Visbreaking of a Vacuum Residue

Abstract

To identify hydrocarbons that might be sensitive indicators of coke formation in visbreaking, experiments have been conducted on a vacuum residue at 410 °C with residence times of up to 60 min in a microreactor. An induction period of 40 min prior to coke formation was observed, consistent with previous laboratory studies, with the changes in bulk aromaticity being small. As an example of trace aliphatic components, the distribution of hopanes proved to be highly sensitive to cracking severity but not to the onset of coke formation. In contrast, the concentrations and distributions of polycyclic aromatic hydrocarbons (PAHs) are sensitive to coke formation. Small ring size PAHs and their substituted equivalents were present in the feed, and their concentrations increased with coke formation. However, for the 6-ring PAH, benzo[ghi]perylene, the concentration was constant at ca. 0.1 ppm of the total aromatics during the coke induction period and then increased sharply thereafter to ca. 0.3 ppm. Therefore, it is proposed that tracing the concentrations of large ring PAHs, such as benzo[ghi]perylene, offers a novel and sensitive approach to assess the onset of coke formation in visbreaking.

Upgrading bio-oils obtained from bio-ethanol and bio-diesel production residues into bio-crudes using vis-breaking

“…However, an aromatic product with elemental formula similar to that of anthracene whose yield tends to increase during visbreaking was generated at 410 °C. 29 The data indicate that the RSM bio-crude is similar to decant oil (C 100 H 110 ON) 32 while the WSG bio-crude are more similar to those of conventional petroleum. Therefore, 410 °C seems to be a critical temperature for the breakage of C-H bonds and generation of H 2 O and light hydrocarbons in the gas phase, while lower temperature should be used to promote the C-O bond breakage but retain hydrogen into the bio-crude.…”

“…These data are in agreement with the findings of Ogbuneke et al that showed a reduction in coke formation during visbreaking of heavy vacuum residues with addition of more than 2 wt% water probably due to gasification reactions. 26 3.3 Bio-crude characterisation 3.3.1 Elemental analysis and calorific values. Table 3 shows the elemental analysis of the bio-crudes from Thermo-t.…”

“…[24][25] Recently, a small addition of water has showed reduced coke formation during visbreaking. 26 This work focuses on the upgrading of bio-oils obtained from rapeseed meal (biodiesel production residue) and wheat spent grains (bioethanol residue) into high quality bio-crudes using vis-breaking. The effect of temperature on deoxygenate yield and quality of the bio-crudes from the Thermo-t process was studied.…”

“…Furthermore, the addition of water was evaluated in order to enhance the deoxygenation of pyrolytic bio-oil in comparison to work done on upgrading crude-oil heavy vacuum residues. 26,[27][28][29] The integration of this process into a biorefinery system has been analysed.…”

Application of Ethylene Tar as an Additive in Visbreaking of Petroleum Vacuum Residue

“…The coking tendencies of various vacuum residues during visbreaking, which depend on the time and temperature of exposure, have been the subject of several studies. ,− An increase in the harshness of the visbreaking conditions speeds up the conversion. It leads to the formation of carbon structures without hydrogen, which enter into condensation and polymerization reactions generating insoluble polycondensed structures, ultimately leading to coke formation.…”