Catalytic Cracking of Light Crude Oil to Light Olefins and Naphtha over E-Cat and MFI: Microactivity Test versus Advanced Cracking Evaluation and the Effect of High Reaction Temperature

The catalytic cracking of light paraffinic crude oil with an API gravity of 51 degrees was compared using two laboratory testing techniques, a fixed-bed microactivity test (MAT) unit and a fixed fluidized-bed advanced cracking evaluation (ACE) unit. Both units were operated using equilibrated FCC catalyst (E-Cat), MFI zeolite (ZSM-5), and E-Cat/MFI (equal mixture with MFI) at two temperatures (550 and 600 degrees C) and a constant catalyst-to-oil ratio of 4.0. Despite the different hydrodynamics in MAT and ACE reactors, both units gave similar catalyst ranking based on the conversion of 221+ degrees C feed fraction at 550 and 600 degrees C in the order of E-Cat > E-Cat/MFI > MFI, which is attributed to diffusion limitation of MFI catalyst. While both testing techniques showed variation in product yield structure (dry gas, LPG, naphtha, and unconverted 221+ degrees C) over the three catalysts, the ACE unit gave significantly higher coke yield compared with MAT. The highest yield of light olefins was obtained over E-Cat/MFI (29 wt %) at 600 degrees C in MAT compared with MFI (23 wt %) and E-Cat (21 wt %). The effect of high temperature (650 degrees C) on crude oil cracking in ACE showed an increase in conversion and light olefins yield for all catalysts as well as in thermal cracking case (no catalyst) associated with a decrease in naphtha yield. The highest yields of light olefins (35 wt %) was obtained at a naphtha yield of 37 wt % over E-Cat/MFI compared with 30 and 41 wt %, respectively, for no catalyst. However, the operation at high temperature introduced the adverse effects of thermal cracking resulting in high yields of dry gas (14 wt % for E-Cat and 17 wt % for no-catalyst), which reflects a significant contribution of pyrolytic cracking reactions.