Impact of Initiators on Polyethylene Synthesis in a High-Pressure Multizone Autoclave

On an industrial scale, low-density polyethylene (LDPE) is produced under conditions of up to 3000 bar and 300 °C using high-pressure tubular and autoclave reactors. Autoclave reactors are often operated as multizone systems with additional feed points along the reactor axis. In contrast, laboratory-scale reactors are predominantly stirred vessels with a single reaction zone. The residence time behavior and potential for temperature profiling create significant differences between these reactor types. To bridge the gap between laboratory and industrial scale, this work presents a high-pressure multizone autoclave at the laboratory scale which was constructed in the mechanical workshop of the Chemistry Department at the Technical University of Darmstadt. A specially designed stirrer divides the autoclave into three different zones. During high-pressure polymerization experiments, various zones of the autoclave can be targeted with peroxide initiators. The system’s response is evaluated by temperature profiles and the resulting molecular weight distribution (MWD). This paper demonstrates these effects by selectively addressing the individual zones.