Gas‐phase polymerization of ethylene using MgCl2/ethyl benzoate/TiCl4 + triethylaluminum catalyst: Effects of triethylaluminum and temperature

A gas‐phase reactor system was developed to polymerize ethylene using the MgCl2/ethyl benzoate (EB)/TiCl4+ triethylaluminum (TEA) catalyst. The reproducibility of the reactor was tested and found to be adequate for kinetic study. The effects of TEA and temperature were studied with the multisite model that assumes a multiplicity of active sites. It was found that the productivity increased with Al/Ti molar ratio while initial activity leveled off. The deactivation rate, after an initial increase, Al/Ti molar that assumes a multiplicity of active sites. It was found that the productivity increase, decreased with Al/Ti. This corresponded with a transition in deactivation order: below Al/Ti = 70, first‐order deactivation was predominant; above Al/Ti = 70, second‐order deactivation was predominant. The second‐order deactivation reactions were made less disperse at higher Al/Ti. Molecular weight of the polyethylene was very high (> 1,000,000) indicating negligible transfer reactions. For Al/Ti > 130 a monomer sorption limitation for polymerization was found. The effect of temperature was also studied with a maximum in productivity at 55°C for Al/Ti = 98.0 and no maximum when Al/Ti = 53.0. Apparent activation energies (Ea) for activity were found to be 19.5 ±3.3 kJ/mol at Al/Ti = 98.0 and 9.3±1.1 kJ/mol at Al/Ti = 53.0. for deactivation Ea was found to be 36.6±5.0 kJ/mol at Al/Ti = 98.0 and–15.5± 4.4 kJ/ mol at Al/Ti = 53.0. Temperature increased the dispersity of second‐order deactivation reactions.