Study on the Oligomerization of Ethylene in Fluidized Catalytic Cracking (FCC) Dry Gas over Metal-Loaded HZSM-5 Catalysts

Abstract

Oligomerization of ethylene in fluidized catalytic cracking (FCC) dry gas was investigated as a feasible route for the use of FCC dry gas. A series of metal-loaded HZSM-5 (MZSM-5) catalysts were prepared by the impregnation method. It was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and N2 adsorption that the metal introduction did not change the structure of the HZSM-5 catalyst but had an influence on acidic properties, i.e., decreasing Brönsted acid sites and forming Lewis acid sites together with the blocking of channels. The catalytic performances of MZSM-5 catalysts for the oligmerization of ethylene in FCC dry gas were studied in a fixed-bed reactor. It was observed that the addition of metal to fresh HZSM-5 enhanced the olefin yield. Among all catalysts studied, MgZSM-5 exhibited the highest propylene and total olefin yields of 12.21 and 17.28%, respectively. Higher olefin yields were obtained over the steam-treated HZSM-5 catalyst when adding moderate N2 as a diluent gas. The catalytic performance of the steam-treated HZSM-5 catalyst was also investigated in a fluidized-bed reactor, and similar product distribution could be obtained in comparison to that in a fixed-bed reactor. The conversion of ethylene could reach 47.22% at 500 °C with a propylene yield of 14.32%.