Fischer–Tropsch tail gas oligomerization to synthetic kerosene: Impact of low concentration of carbonyl compounds

Abstract The tail gas produced from the final vapour–liquid–liquid phase separation after Fischer–Tropsch synthesis was converted over H‐ZSM‐5 at 240°C and 2.5 MPa in an oligomerization process. The C 2 –C 5 alkene conversion was ≥95%, and approximately 67% of the oligomerization product was within the kerosene boiling range. Unexpectedly, the aromatic selectivity was nearly 50% at this low temperature. It was postulated that the aromatics were produced through acid‐catalyzed carbonyl conversion. A model compound study involving acetone, butanone, ethanal (acetaldehyde), and butanal (butyraldehyde) was performed. Acid‐catalyzed conversion of carbonyl compounds was shown to produce aromatics even at 200°C. Aromatic selectivity decreased in the order: acetone (60%–80%) > butanone (15%–25%) > ethanal (<10%) > butanal (<2%). Despite these positive outcomes, the cause of the unusually high aromatic selectivity in Fischer–Tropsch tail gas oligomerization remained unresolved.