A Comparative Study of Ni-Based Catalysts Prepared by Various Sol-Gel Routes

The use of heterogeneous catalysts to increase the development of green chemistry is a rapidly growing area of research to save industry money. In this paper, mesoporous SiO₂-Al₂O₃ mixed oxide supports with various Si/Al ratios were prepared using two different sol-gel routes: hydrolytic sol-gel (HSG) and non-hydrolytic sol-gel (NHSG). The HSG route was investigated in both acidic and basic media, while the NHSG was explored in the presence of ethanol and diisopropyl ether as oxygen donors. The resulting SiO₂-Al₂O₃ mixed oxide supports were characterized using EDX, N₂ physisorption, powder XRD, ²⁹Si, ²⁷Al MAS-NMR and NH₃-TPD. The mesoporous SiO₂-Al₂O₃ supports prepared by NHSG seemed to be more regularly distributed and also more acidic. Consequently, a simple one-step NHSG (ether and alcohol routes) was selected to prepare mesoporous and acidic SiO₂-Al₂O₃-NiO mixed oxide catalysts, which were then evaluated in ethylene oligomerization. The samples prepared by the NHSG ether route showed better activity than those prepared by the NHSG alcohol route in the oligomerization of ethylene at 150 °C.