Nickel-based solid catalysts for ethylene oligomerization – a review
Ni-based inorganic porous materials are the most important heterogeneous catalysts for ethylene oligomerization. In spite of extensive research carried out in previous decades on these catalysts, only a few aspects have been reviewed in the literature. We illustrate here the main properties of these materials and their catalytic performances in oligomerization reactions performed under mild conditions. The major groups of oligomerization catalysts, including NiO on various carriers and Ni-exchanged zeolites, sulfated-alumina or silica–alumina, are described in the first part of this review. The nature of the active sites and their role in the ethylene oligomerization process are pointed out. In the second part, the literature dealing with the catalyst performances under various reaction parameters is reviewed. The influence of catalyst properties (in particular the catalyst pore size) and reaction conditions (i.e. temperature and pressure) on the productivity and the product distribution in oligomerization is methodically discussed. The excellent performances of Ni-exchanged ordered mesoporous silica–alumina, which are the best oligomerization catalysts known today, are carefully emphasized.