共价负载型α-二亚胺镍催化剂的制备及其催化乙烯聚合

合成了一种含有胺基的α-二亚胺镍配合物,该配合物与三乙基铝改性的SiO2通过共价键结合形成负载型α-二亚胺镍催化剂,以一氯二乙基铝为助催化剂,研究了其对乙烯聚合性能的影响。实验结果表明,以庚烷作溶剂时,该催化剂具有较高的催化活性,聚合温度和n(Al):n(Ni)对催化活性和聚合物的性质有较大的影响。得到的聚乙烯产品是不仅含有甲基支链,而且含有乙基、丙基、丁基、戊基甚至长支链的高支化聚乙烯。支链数(1 000 C)随聚合温度升高而增加,从0℃时的12．94增加到75℃时的116．02,重均相对分子质量和熔融温度却随聚合温度的升高而下降。用扫描电镜表征聚合物的形态,结果发现催化剂的形态对聚合物形态具有模板作用。

(α-Diimine) Nickel Covalently Supported Catalyst for Ethylene Polymerization

Bis(4-(4-amine-3,5-diisopropylbenzyl)-2,6-diisopropylphenylimino)acenaphthene NiBr2 was synthesized. The complex was covalently supported on silica pretreated with triethyl aluminum and was used to prepare catalyst for ethylene polymerization. The polymerization was carried out with inexpensive common alkylaluminum compounds as cocatalyst and heptane as solvent. Branched polyethylene was obtained. The supported diimine Ni complex showed high activities for the polymerization. Reaction conditions, namely n(Al) :n(Ni)and temperature, had significant effects on catalytic activity and properties of obtained polyethylene. Structure of obtained polyethylene was confirmed by means of high-temperature 13C NMR. It contained evident amount of methyl, ethyl, propyl,butyl,pentyl and longer branched chains. The branching degree of the polymer(1 000 C) was 12.94 at 0℃ to 116. 02 at 75℃. It increased with reaction temperature,but weight average relative molecular mass and melting point of polyethylene changed conversely. This led to a linear semicrystalline polymer which was amorphous in bulk. The SEM images of the polymers obtained on the supported catalyst showed that catalyst morphology had templated effect to the polymers.