Effect of Prepolymerization on the Kinetics of Ethylene Polymerization and Ethylene/1‐Hexene Copolymerization with a Ziegler–Natta Catalyst in Slurry Reactors

Abstract

The effect of prepolymerization on ethylene homopolymerization and ethylene/1‐hexene copolymerization with a commercial TiCl4/MgCl2 catalyst was investigated and the apparent homo‐ and copolymerization rate constants were estimated by varying polymerization temperature, pressure, time, and 1‐hexene/ethylene molar ratio during the prepolymerization. The apparent rate constants for activation, propagation, and deactivation depend on the prepolymerization conditions, showing that the prepolymerization stage strongly regulates the behavior of the catalyst in the main polymerization. Interestingly, the surface morphology of the prepolymer particles correlates to and explains these changes in polymerization kinetics behavior.

Particle morphology and morphogenesis of nascent polyethylene produced with a spherical MgCl2‐supported Ziegler–Natta catalyst in slurry process

“…In ethylene polymerization with MgCl 2 ‐supported Ziegler–Natta catalysts, the activity can be markedly enhanced by adding a small amount of α‐olefin comonomer like propylene, 1‐butene, or 1‐hexene . In order to synthesize PE at higher polymerization activity, small amount of propylene was added to the ethylene polymerization system after the prepolymerization step, and ethylene–propylene copolymerization was conducted for 30 min.…”

“…Without effective control on the particle morphology, intensive polyolefin production in either slurry or gas phase continuous polymerization processes cannot be made because of serious reactor fouling, sheeting, or clogging problems. For this reason, intensive efforts have been paid to the studies of morphology and morphogenesis of polyethylene (PE) and polypropylene nascent particles synthesized with heterogeneous Ziegler–Natta catalysts. In the past, a large number of microscale morphologies have been observed on the external and internal surfaces of nascent PE particles, including fibrillar, wormlike, globular, and cobweb‐like morphologies.…”

Influence of the Ethanol Content of Adduct on the Comonomer Incorporation of Related Ziegler–Natta Catalysts in Propylene (Co)polymerizations

“…In this study, the effect of the alcohol content (n = 0.7, 1.2, and 2.8) of the MgCl 2 .nEtOH adducts on the related ZN catalyst performance is investigated in relation to copolymerizations [19,20], and, in particular, propylene/1-hexene copolymerizations [18,21]. For this purpose, their activity, comonomer susceptibility toward 1-hexene comonomer in the presence of hydrogen, and their effect on the final structure of the produced polymer are assessed in depth.…”

Comparative Study on Kinetics of Ethylene and Propylene Polymerizations with Supported Ziegler–Natta Catalyst: Catalyst Fragmentation Promoted by Polymer Crystalline Lamellae

“…Despite extensive fundamental studies in this field over the past decades, there are still many unsolved problems concerning the polymerization mechanism and relationships between catalyst structure and polymerization behaviors. The kinetics and mechanism of ethylene and propylene polymerizations with Z–N catalysts have been studied in a broad span of reaction durations ranging from less than 1 s to more than one hour [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. When ethylene and propylene polymerizations with the same catalyst are compared, several peculiarities in the reaction kinetics have been reported.…”