Enhancing the Production of Light Olefins by Catalytic Cracking of FCC Naphtha over Mesoporous ZSM-5 Catalyst

Abstract

The enhanced production of light olefins from the catalytic cracking of FCC naphtha was investigated over a mesoporous ZSM-5 (Meso-Z) catalyst. The effects of acidity and pore structure on conversion, yields and selectivity to light olefins were studied in microactivity test (MAT) unit at 600°C and different catalyst-to-naphtha (C/N) ratios. The catalytic performance of Meso-Z catalyst was compared with three conventional ZSM-5 catalysts having different SiO 2 /Al 2 O 3 (Si/Al) ratios of 22 (Z-22), 27 (Z-27) and 150 (Z-150). The yields of propylene (16 wt%) and ethylene (10 wt%) were significantly higher for Meso-Z compared with the conventional ZSM-5 catalysts. Almost 90% of the olefins in the FCC naphtha feed were converted to lighter olefins, mostly propylene. The aromatics fraction in cracked naphtha almost doubled in all catalysts indicating some level of aromatization activity. The enhanced production of light olefins for Meso-Z is attributed to its small crystals that suppressed secondary and hydrogen transfer reactions and to its mesopores that offered easier transport and access to active sites.

Binder Selection to Modify Hydrocarbon Cracking Properties of Zeolite-Containing Composites

“…In the formulation with water glass binder (S), the formation of olefins was reduced because of the low acidity of the matrix; that is, all the cracking reactions occur mainly at the zeolite Y, where hydrogen transfer takes place because of the low Si/Al ratio of the zeolite. 40 In addition, as observed in Figure 4 and Table 3 , the pore volume of this sample was low, which reduced the pore diffusion in the system. This favored subsequent cracking reactions because of diffusion limitations and reduced the yield of olefins.…”

Crude oil to chemicals: light olefins from crude oil

“…Mesoporosity can be introduced by alkaline treatment or secondary templating, improving selectivity to propylene. 89 ZSM-5 based additives were firstly commercially introduced into the FCC process in the 1980's to improve gasoline octane numbers. Nevertheless, today the additive is principally used with the purpose of increasing C3-C5 olefins yields.…”

Maximizing propylene production via FCC technology

“…8 Effect of ZSM-5 loading on propylene yield [20] Appl Petrochem Res (2015) 5:377-392 383 ratios when acidity is high [13,35]. These hydrogen transfer reactions lead to the production of more dry gas, such as methane and ethane, leading to a drop in the selectivity of light olefins.…”