Design and screening of bimetallic Ni‐based ZSM ‐5 catalysts for enhanced ethylene oligomerization

Nickel‐based heterogeneous catalysts (Ni‐ZSM‐5 and bimetallic Ni‐M‐ZSM‐5, M = Cr, Co, Fe) were prepared by ultrasonic‐assisted impregnation, and their catalytic performance and product regulation mechanism in ethylene oligomerization reaction were systematically investigated. The characterization analysis showed that the metal loading did not destroy the structure of ZSM‐5 zeolite skeleton, but significantly affected the carbon deposition behaviour: Ni‐ZSM‐5 mainly generated carbon nanotube structure carbon deposits, while bimetallic catalysts (such as Ni‐Cr‐ZSM‐5) mainly used ordinary carbon accumulation. In the fixed‐bed reactor (ethylene pressure 1 MPa, temperature 300°C, flow rate 10 mL/min(GHSV(120 mL/(mL·h)), reaction 48 h), Ni‐Fe‐ZSM‐5 showed the best ethylene conversion rate and the highest selectivity for C4 olefins, and its conversion rate to ethylene could still be maintained at about 96.3% after 48 h of reaction, while the selectivity for C4 could also reach 65.2%. Among the liquid phase products generated, Ni‐Cr‐ZSM‐5 had the highest selectivity for olefins (46.8%), Ni‐ZSM‐5 had the highest selectivity for aliphatic hydrocarbons (69.24%), while pure ZSM‐5 had a selectivity of 63.49% for aromatics due to the strong acidic site as the dominant reaction path, and the amount of liquid phase products generated when using pure ZSM‐5 was much higher than that of other metal‐loaded ZSM‐5 zeolites.