有机铬催化剂催化乙烯聚合

Ethylene polymerization with organic chromium catalyst

研究了有机硅烷铬酸酯催化剂（简称有机铬催化剂）在乙烯气相均聚合小试中的催化性能和聚合动力学行为。考察了不同种子床制备方法、有机铬催化剂加入量、聚合温度、乙烯与氢气分压比对聚合的影响，并对聚乙烯（PE）进行了结构与性能的分析表征。结果表明：经热活化与化学活化处理后的硅胶表面基本不含羟基，适宜作为种子床使用；有机铬催化剂加入量在100.0～150.0mg时其活性最高且保持稳定，聚合动力学曲线为快速上升缓慢下降型；聚合温度在80～100℃时有机铬催化剂活性最高且变化不大，但在110℃时下降；随聚合温度升高，PE的重均分子量与数均分子量均降低，且相对分子质量分布明显变窄；H2的加入会显著降低有机铬催化剂活性。

The authors researched catalytic performance and kinetic behavior of organosilyl chromate catalyst in laboratory scale ethylene gas-phase homopolymerization. The effects of different preparation methods of seed bed, amount of the catalyst, polymerization temperature, ratio of ethylene and hydrogen on ethylene polymerization were explored, and the structure and properties of the resultant products were characterized. The results show that silica gel without hydroxyl on the surface after heat activation and chemical activation treatment is appropriate for being used as the seed bed. The catalytic activity reaches its maximum and remains stable, and the polymerization kinetics curve is the type of rising soon and declining slowly when the amount of the catalyst is 100.0-150.0 mg. And the activity of organic chromium catalyst meets its best and changes slightly when the polymerization temperature is 80-100 ℃, but it has a sharp decrease at 110 ℃. With the increase in the polymerization temperature, both weight average molecular mass and number average molecular mass are decreased, and the relative molecular mass distribution gets narrower. Adding hydrogen can reduce the activity of organic chromium catalyst significantly.