Polyethylene Formation Investigated in Micro Reactors

3 Polyethylene Formation Investigated in Micro Reactors Organic synthesis 62 [OS 62] Radical polymerization of ethylene 

A stream of ethylene is fed into the reactor by use of quaternary LC pumps and subsequently dissolved in a 1.90 ml h toluene stream [1]. Ethylene is handled at 60 °C, well above the critical temperature. Catalyst additions are fed via HPLC-type sample injection valves. Various combinations of precatalysts and activators were sampled and loaded by an autoinjector. Catalyst solutions typically were diluted 20-fold within the micro reactor. 

The total solvent flow rate was set to 2.0mlmin . Separate streams of catalyst (0.02 M in toluene) and cocatalyst (0.02 M in toluene) formulations were fed to the tubing reactor in the microliter per minute range by use of special micro-pumps. 

The volume of the injection loops amounted to 20 pi the catalyst stream was set to 50 pi min In an electrothermal pre-heat zone the ethylene/comonomer mixture in toluene was brought close to reaction temperature before adding catalyst. The reaction was carried out at 175 °C and a pressure of 2.8 MPa. In several subsequent zones each of 16 cm length (volume 200 pi) along the reactor tubing, temperature was monitored by voltage pads. 

By deliberately changing the pressure (in a loop), the temperature response followed immediately [1]. This proved that control of pressure is cmcial for obtaining stable temperature baselines. 

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