预聚合条件对高效催化剂催化乙烯气相聚合的影响

采用经预聚合处理的ＭｇＣｌ２负载的钛系催化剂进行乙烯气相聚合和淤浆聚合比较．乙烯淤浆聚合其表观动力学呈现为加速型或渐升衰减混合型，而气相聚合则为衰减型．在聚合前期阶段，气相聚合速度明显高于淤浆聚合速度．这样的差别是由于淤浆聚合中明显存在着单体在颗粒中扩散受阻的影响，气相聚合中则存在过热现象．测定了两种聚合方式中催化剂的钛价态，结果表明气相聚合条件下钛的价态分布比淤浆聚合更大程度倾向于低价态．催化剂预聚合温度和预聚合产率对气相聚合活性及表观动力学行为的影响表明预聚合工艺是气相聚合反应平稳控制有效技术．

THE EFFECT OF PREPOLYMERIZATION PROCESS ON GAS-PHASE POLYMERIZATION OF ETHYLENE WITH HIGHLY ACTIVE CATALYST

as-phase polymerization of ethylene over a prepolymerized MgCI,supported TiCl4. catalyst was compared with slurry polymerization. An accelerationtype or hybrid-type rate behavior for the slurry polymerization, but a decay-type rate behavior for the gas-phase polymerization have been observed. The difference in the apparent kinetics between these two processes could result from monomer diffusion resistance in the slurry polymerization and overheat effect in the gas-phase polymerization. The measurment of the oxidation states of titanium in the catalyst indicated that more titanium ions were reduced to lower oxidation state in the gasphase process than in the slurry process. The prepolymerization temperature and yield also remarkably affected the polymerization activity and kinectic behavior.