Synthesis of ZSM-5 by rapid crystallization method for FCC olefins maximization

Abstract

This research aimed to study the effect of changing ZSM-5 Si/Al ratios on maximizing Fluid Catalytic Cracking (FCC) light olefins. ZSM-5 additives with Si/Al ratios of: 20,140,220, and 370, and with different metallosilicates Si/Fe ratios: 47 and 165, and Si/Ni ratios: 46 and 102 were prepared. ZSM-5 zeolite prepared by rapid crystallization method (RCM) yields small uniform sized crystals to provide better selectivity of light olefins via FCC mainly propylene which is in high demand world wide. All prepared samples were characterized by X-ray diffraction, scanning electron microscopy, and sorption analyzer. The effects of varying Si/Al ratio and the concentration of the additives in the FCC catalyst on the activity and selectivity were assessed in a micro-activity test (MAT) unit. It was found that by increasing Si/Al ratio, the yield of propylene was increased in the range studied in this thesis. This was attributed to the lower acidity of ZSM-5 additives with high Si/Al ratio. An increase of 0.9 wt % in the propylene yield was obtained at highest Si/Al ratio studied. The increase of propylene yield did not affect gasoline yield substantially. In the case of metallosilicates, higher propylene was formed by high Si/Ni ratio by about 1.33 wt % compared with Si/Fe sample. This showed higher activity of Nickel silicate over Iron silicate prepared in this study.