Ultra-low hydrogen content bowl-shaped polycyclic aromatic hydrocarbons in petroleum

•Ultra-low hydrogen content PAHs observed in the processed petroleum bottoms.•The H10 molecules can be rationalized by the corannulene-based PAHs.•Highly curved bowl-shaped PAH structures proposed for H8, H6 and H4 molecules.•H8, H6 and H4 PAHs do not obey the “isolated pentagon rule” as do H10 PAHs.•Strain energies of the PAHs are lower than that of fullerenes of the same C number.•The bowl-shaped PAHs are likely formed in the catalytic cracking of the petroleums.