Multi-Scale, Multi-Phase Modelling of a Slurry-Phase Catalytic Ziegler-Natta HDPE Continuous Process

Conference Dates

May 20-25, 2018


Continuous slurry-phase polymerization, in the presence of a heterogeneous Ziegler–Natta (Z–N) catalyst, is one of the most commonly employed processes in the production of polyolefins, including high-density polyethylene (HDPE), isotactic polypropylene (IPP) as well as their copolymers with higher olefins. Polymerization in a series of reactors is often employed to control comonomer distribution, which is important for resin grades such as pipe applications that require excellent environmental stress crack resistance. The slurry HDPE process technology employs two or more stirred-tank reactors in series and utilizes a Z-N catalyst system composed of a titanium chloride compound and an alkyl aluminum cocatalyst. The process uses hydrogen as a chain-termination agent to control the molecular weight of the product and a comonomer to control the density of the polyethylene grade. The process operates in a continuous mode in a cascade of two or three autoclave-type vessels. Each reactor can operate under a different hydrogen partial pressure, thereby allowing the control of the molecular weight distribution. Typical reaction operating conditions are temperature 70 - 90 °C and a pressure less than 10 bar with a residence time 45 min per reactor.

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