持液颗粒聚合:一种新型环境下的乙烯/α-烯烃反应

Liquid Containing Particle Polymerization:Ethylene/α-Olefin Reaction in a New Environment

通过改变乙烯/1-己烯共聚合反应中冷凝剂正己烷的含量,建立了纯气相、贫己烷和富己烷3种聚合环境,结合共单体效应和共溶效应的作用机制,分析了3种聚合环境下的聚合反应.结果表明,在纯气相环境下,由于干颗粒内部的毛细冷凝现象,共单体效应占据主导,聚合反应活性下降.在贫己烷环境下,初期由于湿颗粒内高浓度的1-己烯/乙烯比,聚合反应活性在共单体效应和共溶效应竞争作用下基本保持不变,后期随着正己烷含量的增加,共溶效应占据主导,聚合反应活性上升,在持液颗粒聚合模式下,气相和液相环境的初始1-己烯/乙烯摩尔比均是最佳,聚合反应活性最大.在富己烷环境下,聚合反应活性由于1-己烯浓度被正己烷溶剂稀释而略有下降.聚乙烯产品支化度在纯气相环境和贫己烷环境中相当,略高于富己烷环境的聚乙烯支化度.

With the change of the condensing agent(n-hexane)content in the process of ethylene/1-hexene copolymerization,three polymerization environments of pure gas phase environment,poor n-hexane environment and rich n-hexane environment were established.The"comonomer effect"and the"cosolubility effect"collectively affect the copolymerization reaction.The results show that the polymerization activity decreases in the pure gas phase environment,due to the capillary condensation inside the dry particles,and the comonomer effect dominates.In the poor n-hexane environment,because of the high molar concentration ratio of 1-hexene/ethylene in the wet particles at the initial stage,the polymerization activity remains basically unchanged under the competition of the comonomer effect and the cosolubility effect.With the increase of n-hexane content,co-solubility effect dominates,and the polymerization activity rises.The liquid-containing particle polymerization mode that the molar concentration ratio of 1-hexene/ethylene in the gas phase and slurry environment is the best maximizes the polymerization activity.In the rich n-hexane environment,the polymerization activity decreased slightly due to the dilution of 1-hexene concentration by n-hexane.The short chain branch degree of polyethylene products is almost the same in the pure gas phase environment and the poor n-hexane environment,slightly higher than that in the rich n-hexane environment.