超支化铬系催化剂的合成及乙烯齐聚性能研究

以不同端基烷基链长度的1.0G超支化大分子为桥联基，通过对其端基氨基进行催化功能改性，合成了系列具有不同桥联基长度的超支化PNP铬系催化剂。采用红外光谱(IR)、核磁共振氢谱(1H-NMR)、核磁共振磷谱(31P-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相符。详细考察了溶剂种类、反应温度、Al/Cr摩尔比、反应压力、催化剂用量和催化剂结构对催化剂乙烯齐聚性能的影响。实验结果表明，当以甲苯为溶剂，甲基铝氧烷(MAO)为助催化剂时，超支化PNP铬系催化剂表现出良好的催化乙烯齐聚性能，产物以低碳烯烃为主。最佳条件下，催化活性最高可达到1.69×105g/mol Cr·h，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

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, 1H-NMR, 31P-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 type, reaction temperature, Al/Cr molar ratio, reaction pressure, catalyst amount and catalyst structure on the oligomerization of ethylene were investigated in detail. The experimental results show that when the toluene is used as the solvent and the methylaluminoxane (MAO) is used as the promoter, the hyperbranched PNP chromium catalyst exhibits good catalytic ethylene oligomerization performance, and the product is mainly low-carbon olefin. The catalytic activity can reach up to 1.69×105g/mol Cr·h. And 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.