基于茂金属催化剂的聚乙烯颗粒内部的单颗粒传质模型

Abstract

针对负载型茂金属催化剂催化乙烯聚合中的聚乙烯颗粒增长过程,采用改进的多粒模型建立了淤浆聚合条件下聚乙烯颗粒内部的单颗粒传质模型。采用该模型分析了负载型茂金属催化剂在聚合过程中的破碎行为,结合本征反应考察了传质对聚合反应的影响,计算出乙烯单体浓度和聚乙烯颗粒孔隙率在聚合过程中的变化。模拟结果表明,聚乙烯颗粒内部的传质阻力对聚合反应影响较大,聚合反应约200 S后,负载型茂金属催化剂由外至里逐层破裂。

Ethylene slurry polymerization on silica-supported metallocene catalyst was simulated based on a modified multigrain model.The modified model combined with the intrinsic reaction investigation was used to analyze catalyst fragmentation and polyethylene intraparticle mass transfer.The model can be used to calculate monomer concentration and growth of macro-particle during polymerization.The model can also be applied to predict the variations of particle porosity and monomer concentration distribution during the polymerization.Intraparticle mass transfer resistance has great effect on polymerization.The catalyst fragmentation happen shell-by-shell from surface to centre of catalyst at 200 s after starting of polymerization.