Direct recycling of heavy cycle oil, light cycle oil and heavy naphtha to the RFCC reactor feed: Study on product yield distribution

• Direct recycling of HCO, LCO, and HN to RFCC feed was evaluated using ACE microreactor testing. • Mono-aromatics enhance gasoline formation, while di-aromatics preferentially generate LCO. • ATR + HN achieved the highest conversion and gasoline yield among all blended feeds. • Increasing catalyst-to-oil ratio raised gasoline and olefin yields while reducing LCO and MCB. • Recycling RFCC side streams enables operational control of refinery product value and flexibility. This study examines the recycling of heavy cycle oil (HCO), light cycle oil (LCO), and heavy naphtha (HN) into the feed of a residue fluid catalytic cracking (RFCC) reactor to evaluate their effects on product yield distribution. The objective is to develop strategies for steering RFCC operations toward higher-value products. The recycled streams, rich in aromatic compounds, were tested in a fixed fluidized bed microreactor (ACE test) using a commercial RFCC equilibrium catalyst. The NOFs (neat oil fractions), namely HCO, LCO and HN, and blended feeds with atmospheric residue (ATR) were cracked at 520 °C under varying catalyst-to-oil (C/O) ratios. Conversion of the NOFs followed the order HN (99 wt%) > LCO (87.5 wt%) > HCO (42 wt%), with corresponding gasoline yields of 69, 51, and 14 wt%. For blended feeds, ATR + HN achieved the highest conversion (79.1 wt%) and gasoline yield (51 wt%), while ATR + LCO generated the most olefins. Results demonstrate that mono-aromatics act as gasoline precursors, whereas di-aromatics favor LCO formation. Increasing C/O ratio enhanced gasoline and olefin yields while reducing LCO and main cycle oil. These findings highlight the potential of recycling side streams to optimize RFCC performance and improve refinery fuel flexibility.