超支化铬系催化剂的合成及乙烯齐聚性能研究

以正辛胺和十二胺为原料,分别制备了两种超支化PNP配体,通过引入金属铬活性位点的方法合成了具有不同烷基链长度的超支化PNP铬系催化剂.采用红外光谱(IR)、核磁共振磷谱(~(31)P-NMR)、核磁共振氢谱(~1H-NMR)、紫外光谱(UV)和质谱(MS)等表征方法证明合成催化剂的结构与理论结构预测相符.详细考察了催化剂用量、溶剂种类、反应条件以及配合物结构对乙烯齐聚性能的影响.实验结果显示,超支化PNP铬系催化剂在甲苯作溶剂,甲基铝氧烷(MAO)做助催化剂时表现出良好的催化乙烯齐聚性能,产物主要为低碳烯烃.在最佳条件下,催化活性最高可达到1.69×10~5 g·(mol Cr·h)~(-1),己烯和辛烯的选择性为43.3%以上.相同聚合条件下,其催化活性随着端基烷基链长度的增加而下降.

Synthesis of Hyperbranched Chromium Catalysts and Study on Ethylene Oligomerization Properties

Two kinds of hyperbranched PNP ligands were prepared from n-octylamine and decylamine respectively. And the hyperbranched PNP chromium catalysts with different alkyl chain lengths were synthesized by introducing metal chromium active sites. A series of hyperbranched PNP chromium catalysts with different bridged alkyl chain lengths were synthesized by catalyst functionalizing the terminal amino groups using 1.0G hyperbranched macromolecules with different end alkyl chain lengths as bridged groups. IR,³¹P-NMR, ¹H-NMR, UV and MS were used to prove that the structure of the synthesized catalyst was consistent with the theoretical structure. The effects of solvent dosage, solvent type, reaction conditions and complex structure on the oligomerization of ethylene were investigated in detail. The experimental results show that the hyperbranched PNP chromium catalyst exhibits good catalytic ethylene oligomerization performance, when the toluene is used as the solvent and the methylaluminoxane (MAO) is used as the promoter, and the product is mainly low-carbon olefin. The catalytic activity can reach up to 1.69×10⁵ g·(mol Cr·h)^-1. Under the optimum conditions, the selectivity of hexene and octene is above 43.3%. Under the same polymerization conditions, the catalytic activity decreased with the increase of terminal alkyl chain length.