Nature of the Active Sites in Ethylene Oligomerization Catalyzed by Ni-Containing Molecular Sieves: Chemical and IR Spectral Investigation

Thermoactivated Ni-exchanged AlMCM-41 mesoporous materials were found to be very efficient heterogeneous catalysts for ethylene oligomerization. By means of diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy of adsorbed CO, it has been established that, during the thermal activation under dry atmosphere, the Ni2+ ions were partially reduced to Ni+ ions. A very good correlation between the activation temperature and the catalytic activity in the ethylene oligomerization was observed. Both Ni+ and dehydrated Ni2+ ions were proposed as catalytic active sites in this process.