球形TiCl_4/MgCl_2催化剂引发丙烯气相聚合动力学

Kinetics of gas phase propylene polymerization usingspherical TiCl_4/MgCl_2 catalyst

采用微机在线控制的半连续烯烃聚合反应器,在加压条件下进行了球形TiCl4/MgCl2催化剂催化的丙烯气相聚合,测定了单体瞬时聚合速率等重要的动力学数据,考察了不同聚合条件对聚合动力学的影响,并用Flory-Huggins方程估算了聚合物非晶区中的单体浓度Cm.研究表明聚合速率与Cm成正比;丙烯聚合速率在反应一开始就迅速衰减,之后是缓慢的衰减.提出了一个n级衰减的丙烯气相聚合动力学模型,根据实验数据拟合得到了模型的各个参数,其中活性中心的衰减级数为2.5,气相聚合的表观增长活化能为77.1kJ.mol-1.用该模型可以较好地模拟加压条件下的丙烯气相聚合动力学行为.

The kinetics of gas phase propylene polymerization was studied at elevated pressures by using a spherical TiCl4/MgCl2 catalyst. The experiments were carried out in a semi-batch olefin polymerization reactor equipped with an on line computer control system. Important kinetic data such as instantaneous reaction rate of monomer were obtained. The effects of polymerization conditions on reaction kinetics were systematically studied. The Flory-Huggins equation was used to estimate the monomer concentration in the polymer amorphous region. It was found that reaction rate had a linear relationship with monomer concentration. The time evolution of polymerization rate under all conditions followed the same pattern, with a fast decay in the early stage of polymerization and a relatively slow decay in the later stage. An nth decay model was developed to describe the dynamic changes of polymerization rate. Experimental data were used to estimate the model parameters. The decay order n was found to be 2.5 and the lumped propagation activation energy was estimated to be 77.1 kJ · mol^-1 , which was similar to the value in the liquid phase reported by other researchers. The model described the experiments well.