Enhancing propylene production from catalytic cracking of Arabian Light VGO over novel zeolites as FCC catalyst additives

The catalytic cracking of vacuum gas oil over fluid catalytic cracking (FCC) catalyst containing novel additives was investigated to enhance propylene yield. A conventional ZSM-5, mesoporous ZSM-5 (Meso-Z), TNU-9 and SSZ-33 zeolite were tested as additives to a commercial equilibrium USY FCC catalyst (E-Cat). Their catalytic performance was assessed in a fixed-bed micro-activity test unit (MAT) at 520 degrees C and various catalyst/oil ratios. The cracking activity of all E-Cat/additives did not decrease by using these additives. The highest propylene yield of 12.2 wt.% was achieved over E-Cat/Meso-Z compared with 9.0 wt.% each over E-Cat/ZSM-5 and E-Cat/TNU-9, at similar gasoline yield penalty. The enhanced production of propylene over Meso-Z is attributed to its mesopores that suppressed secondary and hydrogen transfer reactions and offered easier transport and accessibility to active sites. The lower enhancement of propylene over the large-pore SSZ-33 additive was due to its high-hydrogen transfer activity. Gasoline quality was improved by the use of all additives, as octane rating increased by 7-12 numbers for all E-Cat/additives. (C) 2010 Elsevier Ltd. All rights reserved.