Olefins production from cracking of a Fischer–Tropsch naphtha

This paper explores the potential of converting a naphtha-cut (C5–C16) obtained from Fischer–Tropsch synthesis into small olefins under conditions close to commercial FCC operation. Comparing the activity of HZSM-5 and H-Y catalysts in the transformation of FT naphtha fraction at 450 °C under FCC conditions, H-ZSM-5 was found to be more active. In the present case, calculation of conversion is not straightforward since boiling point range of reactant molecules overlaps with the boiling point of many observed products. A method to estimate the conversion is proposed based on detailed PIANIO analysis of the liquid products. Hydrothermal deactivation reduces H-ZSM-5 activity and cyclization followed by hydrogen transfer reactions, but can be compensated by an increase in reaction temperature. Results obtained at six distinct H-ZSM-5 percentages (from 0.5 to 20 wt.%) suggest that under commercial FCC conditions, the use of H-Y zeolite to primary crack feed molecules that would further react on ZSM-5 is not necessary. Naphtha from FT synthesis can be potentially used to produce base petrochemical products in a dedicated FCC unit.