Effect of aluminum on the mesoporous materials support of heterogenized Nickel β-diimine in oligomerization reactions

Abstract

The β-diimine ligand 2-(phenyl)amine-4-(phenyl)imine-2-pentene was combined with the alkoxysilane group CPTMS, covalently anchored to the mesoporous supports (Al-MCM-41 (Si/Al = 15) and Al-SBA-15 (Si/Al = 15) and (Si/Al = 5)) by interaction with the silanol groups of the silica matrix, then complexed with nickel bromide. The Ni-β-diimine/Al-mesoporous materials complexes were synthesized for application in olefin oligomerization reactions, and the results were compared to those obtained of complexes obtained using the mesoporous materials Si-MCM-41 and Si-SBA-15. To confirm the success of the synthesis, the materials were characterized through several techniques such as 1H, 13C and 29Si NMR, small angle XRD, elemental analysis, N2 adsorption and desorption isotherms, transmission electron microscopy and flame atomic absorption spectroscopy. The Ni-β-diimine/Al-MCM-41 complexes are active and selective for ethylene and propylene oligomerization reactions, also showed to be more active for usage in oligomerization reactions of both olefins when compared to complexes obtained using Si-MCM-41. Ni-β-diimine/SBA-15 complexes obtained using pure silica SBA-15, Al-SBA-15 (Si/Al = 15) or Al-SBA-15 (Si/Al = 5) were also applied on ethylene oligomerization reactions. It was observed a significant rise in the catalytic activity with increase of aluminum content. The higher activity was followed by a greater selectivity for short chain oligomers, in this case butenes (mainly 1-butene).