Ni-exchanged AlMCM-41—An efficient bifunctional catalyst for ethylene oligomerization

A series of Ni-exchanged AlMCM-41 catalysts with carefully controlled concentrations of metallic and acidic sites was prepared, characterized, and tested in ethylene oligomerization performed in slurry batch mode. The mesoporous materials were characterized using various techniques including X-ray diffraction, nitrogen sorption measurements, temperature-programmed desorption of NH3, thermal gravimetric analysis, and temperature-programmed reduction. The presence of a uniform pore-size distribution in the ordered mesoporous materials is very favorable for the oligomerization process. High activities were obtained for most of tested catalysts, and the reaction was highly selective, resulting almost exclusively in olefins with an even number of C4–C12 carbon atoms. Both metal and acid sites are required for the activation of ethylene oligomerization. However, the samples with lower acidity showed very high reaction activity and stability due to their lower deactivation rate. The catalytic activity and product spectrum showed a pronounced dependence on the oligomerization conditions. Thus, the ethylene conversion goes through a maximum at 150 °C reaction temperature, and increased linearly when the pressure increased from 2 to 5 MPa. n-Heptane was found to be an efficient solvent for the ethylene oligomerization.