Heterogeneous oligomerization of ethylene to liquids on bifunctional Ni-based catalysts: The influence of support properties on nickel speciation and catalytic performance

•Ni speciation in Ni-based ethylene oligomerization catalysts studied by FTIR-CO.•Ni/Al-MCM-41 and Ni/Siralox-30 much more active than Ni/Beta.•Ni2+ species with mild Lewis acidity proposed as main active sites.•Higher selectivity and octane for gasoline-range oligomers obtained on Ni/Beta.•Productivity to liquid oligomers maximal for Ni/Al-MCM-41 catalyst.