Effect of impurities in ethylene gas on the catalytic activity of ziegler-natta catalyst and polyethylene properties

Abstract

In this current study, the various types of impurity, which were mostly found in ethylene gas, were used to investigate the influence of impurities on the catalytic activity of a commercial Ziegler-Natta catalyst and polyethylene properties. A desired amount of impurities was injected during ethylene polymerization both in the absence and presence of hydrogen. In the absence of hydrogen, CO, CO₂ and CH₄ poisoned to the catalyst resulting in a decrease in the activity, while C₃H₆ and C₂H₂ enhanced the activity causing from the copolymerization with ethylene. In the presence of hydrogen, hydrogen was differently affected on impurities. It had a beneficial effect in the case of CO. While other compounds exhibited the results in the opposite side. The effects of H₂O and CH₃OH were varied relying on their quantities and operating condition. Hydrogen also gave a beneficial effect on the activity as well. The effects of impurities on ethylene consumption and catalyst decay rate between in the absence and presence of hydrogen were also investigated in this study. Moreover, our studies have been found that impurities reduced Mw and narrow MWD, but they did not affect on the thermal behavior of polyethylene.