Benefits of the SiO₂-supported nickel phosphide catalyst on ethylene oligomerization

Abstract

Although homogeneous catalytic systems have been central in ethylene oligomerization, the SiO2-Al2O3-supported nickel phosphide (Ni2P) catalyst was recently examined to be capable of transforming ethylene into higher olefins. Herein, better catalytic performance in ethylene oligomerization is achieved with Ni2P/SiO2 than Ni2P/SiO2-Al2O3 and Ni2P/Al2O3. As a factor influencing ethylene oligomerization, the particle size of Ni2P is the smallest over Ni2P/SiO2 due to strong metal-support interaction. While the oligomer productivity is affected by the density of Bronsted acid site present in the supported Ni2P catalysts, Ni2P/SiO2 has a relatively high ratio of Bronsted to Lewis acid sites. Moreover, Ni2P/SiO2 is able to easily generate and transfer hydrogen species via the Bronsted acid P OH groups, which would affect formation of nickel hydride species that is important in oligomerizing ethylene. Therefore, the above features of Ni2P/SiO2 are beneficial for ethylene oligomerization into higher olefins.