Heterogeneous oligomerization of ethylene over highly active and stable Ni-AlSBA-15 mesoporous catalysts

Abstract

Ni-AlSBA-15 oligomerization catalysts (2.6wt% Ni, Si/Al=7) were prepared by post-synthesis alumination of SBA-15 silica with sodium aluminate, followed by ion exchange with nickel. Characterization techniques, including powder X-ray diffraction, N2 sorption, TEM, 27Al, and 29Si MAS NMR proved the perfect pore system of the SBA-15 materials, with aluminum tetrahedrally mainly coordinated in the silica framework. Ni-AlSBA-15 exhibited outstanding catalytic behavior in the oligomerization reaction of ethylene. At 150°C and 3.5MPa, in both batch and flow mode, the catalyst was highly active (up to 175g of oligomers per gram of catalyst per hour), selective (C4, C6, C8, and C10 olefins, no cracking products), and stable (high conversion during 80h on stream). These performances were superior than those exhibited by other Ni-based heterogeneous catalysts, without using alkylaluminum cocatalysts. A mechanistic pathway involving metallacyclic intermediates is supported by the experimental results.