Polymerization of olefins with single-site catalyst anchored on amine-functionalized surface of SBA-15

Mesoporous silica SBA-15 functionalized with amine or nitrile group have been synthesized and (n-BuCp)2ZrCl2 and methylaluminoxane (MAO) were subsequently immobilized on the functionalized SBA-15 for the further evaluation as a catalyst of ethylene polymerization. Five silanes such as 3-aminopropyltrimethoxysilane(1NS), N-[(3-trimethoxysilyl)propyl]ethylenediamine(2NS), N1-[3-(trimethoxysilyl)propyl]diethylenetriamine(3NS), and 4-(triethoxysilyl)butyronitrile(1NCy), 1-(3-triethoxysilylpropyl)-2-imidazoline(2NIm) were compared as functional groups for the immobilization (n-BuCp)2ZrCl2 and methylaluminoxane (MAO). Zr contents in the final supported catalysts were observed to be strongly dependent on the nitrogen content on the surface of functionalized SBA-15, indicating the more Zr could be immobilized due to the interaction between (n-BuCp)2ZrCl2 and amine or nitrile groups presented on the surface of SBA-15. 2NIm, 2NS and 3NS were shown to interact with (n-BuCp)2ZrCl2 strongly compared to 1NCy and 1NS due to larger number of amine groups and formation of stable active species. The ethylene homo- and copolymerization activities of (n-BuCp)2ZrCl2 supported on the amine or nitrile-functionalized SBA-15 were increased with an increase in the nitrogen and Zr content in the supported catalyst. The electron-donating effect of the amine or nitrile surface group on the surface toward the (n-BuCp)2ZrCl2 was expected to be a significant parameter in consideration of the higher activity of ethylene homopolymerization and ethylene-1-hexene copolymerization. SBA-15/1NCy/(n-BuCp)2ZrCl2 also showed different chemical compositional distribution of ethylene-1-hexene copolymer compared to the others, meaning change in nature of active species. It would result from different electric environment of nitrile group from amine one. It also revealed that the resulting polymer particle prepared supported (n-BuCp)2ZrCl2 on the amine or nitrile-functionalized SBA-15 was more regular and larger in particle size than that of no functionalized SBA-15.

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► Single site polymerization catalyst anchored on amine-functionalized surface of SBA-15.
► The higher nitrogen contents, the higher Zr contents and polymerization activities.
► It might be due to interaction between Zr complex and amine group of SBA-15.
► Electron-donating effect of the amine group toward the (n-BuCp)2ZrCl2.