摘要
非均相氧化铬催化剂的聚合机理包括Cr^(6+)还原为Cr^(2+)形成活性中心的过程、链引发的单活性中心机理、链增长的Cossee机理、通过β-H消除的链终止机理。硅胶、磷酸铝等载体的改性影响催化剂活性和聚合物性质氧化铬催化剂的负载和活化过程,氟、钛、磷、卤代烃等改性剂对氧化铬催化剂性能有重要的影响.铬系催化剂与其他催化剂复配使用也能缩短诱导期,提高聚合活性,并制备出宽相对分子质量分布的聚乙烯。
The polymerization mechanisms in the presence of heterogeneous chromium oxide catalysts involve the reduction and activation from Cr^6＋ to Cr^2＋, the single active center mechanism of chain initiation, the Cossee mechanism of chain propagation and the termination mechanism based on G-hydrogen elimination. The modification of carriers like silicon and aluminophosphates exerts influence on the catalysts＇ activity and the resultant polymers＇ properties. The loading and activation process of the catalysts and the addition of modifiers like fluorine, titanium, phosphorus and halohydrocarbon have impact on the properties of chromium oxide catalysts. The application of composite catalysts consisting of the chromium-based catalysts and other catalysts can shorten the induction time, improve the polymerization activity and produce polyethylene with broad relative molecular mass distribution.
出处
《合成树脂及塑料》
CAS
北大核心
2011年第6期70-74,共5页
China Synthetic Resin and Plastics
关键词
聚乙烯
铬系催化剂
载体
改性
polyethylene
chromium-based catalyst
carrier
modification
