Sub-Product

Pyrolysis Fuel Oil is obtained as the residual fraction from the distillation of the products of a steam cracking process (including steam cracking to produce ethylene)^[1].

This product is a dark coloured, oily liquid with a pungent odour whose odour threshold is < 1 ppm^[2].

It is known that yield, composition and properties of PFO depend mainly on steam cracking feedstock (gas / naphtha / gas oil fractions):

• According to one source, it is a complex combination of hydrocarbons consisting predominantly of unsaturated hydrocarbons having carbon numbers predominantly greater than C₁₄ and boiling above approximately 260°C (500°F). This stream is likely to contain 5 wt. % or more of 4- to 6-membered condensed ring aromatic hydrocarbons^[1].
• Another source reports that the main components of PFO are bi- and tricyclic aromatic hydrocarbons. The PFO cut with boiling point = 200–330°С consists mainly from C₁₀–C₁₄ hydrocarbons; naphthalene and alkylnaphthalenes account for up to 82% wt; about 10% wt are acenaphthenes, biphenyls and fluorenes. The content of naphthalene, alkylnaphthalenes and biphenyl in the volatile part of PFO is about 77 wt %^[3].
• A third source mentions that PFO is a complex mixture of naphthalene, polycyclic aromatic hydrocarbons, indene, and dicyclopentadiene^[2].

It finds uses as chemical intermediate feedstock or industrial fuel^[2].

References

1. ECHA, Substance Infocard, Residues (petroleum), steam-cracked.
2. NOVA Chemicals, Product Backgrounder, Pyrolysis Fuel Oil (PFO).
3. V.O. Samoilov et al., 2^nd Jan 2024, The production of a liquid organic hydrogen carrier (LOHC) and jet fuel fractions by hydroprocessing of pyrolysis fuel oil (PFO),
   International Journal of Hydrogen Energy, Volume 49, Part B, 2024, Pages 1386-1400, ISSN 0360-3199.