Ziegler–Natta Catalysts

Abstract

This article describes the development and characteristics of Ziegler–Natta catalysts for the polymerization of ethylene, propylene, and other alpha‐olefins. Particular emphasis is given to state‐of‐the‐art MgCl 2 /TiCl 4 /donor catalysts for polypropylene, including current insight into mechanistic aspects of Ziegler–Natta catalysis in relation to catalyst performance and polymer molecular composition and properties. Ziegler–Natta catalysts are multisite systems, in which the nature and the distribution of the active species can be steered to give polymers having different tacticity and molecular weight distributions. MgCl 2 ‐supported catalysts have almost totally replaced the TiCl 3 catalysts used previously and have enabled the development of cost‐efficient bulk and gas‐phase polymerization processes. Spherical particle morphology and controlled particle size and porosity have been achieved and this has played an important role in the widespread application of these catalysts.

The interfacial properties of MgCl2 films grown on a flat SiO2/Si substrate. An XPS and ISS study

“…This procedure leads to desorption of the largest percentage of hydroxyl species from the SiO 2 surface, leaving about 1-3 OH/nm 2 [10]. This is a common treatment of silica supports during the industrial preparation of Ziegler-Natta catalysts [1,2].…”

“…Silicon oxide in combination with magnesium chloride is used as a support for the industrial preparation of some types of ZieglerNatta catalysts [1][2][3]. These catalysts are the best candidates for the low pressure production of linear low-density polyethylene and ethylene co-polymers from the gas phase, with improved optical properties in the film form.…”

Investigation of Planar Ziegler-Natta Model Catalysts Using Attenuated Total Reflection Infrared Spectroscopy

“…We previously reported yields up to 1 kg PP g -1 MgCl 2 after 24 h propylene polymerization in presence of a diether as internal donor [14]. The lower yield of PP in the presence of DIBP as internal donor, as opposed to a diether donor, is to be expected taking into account that esters are to a large extent removed from the support by alkylation and complexation reactions with the cocatalyst (AlEt 3 ) [36]. Figure 4a shows overview spectra of polypropylene obtained when no internal donor was incorporated (24 h polymerization) and polypropylene obtained when DIBP donor was incorporated (2 h polymerization).…”

Growth Mode Study of MgCl2 on Ti (0001) and SiO2 under Ultra High Vacuum by XPS

“…This procedure leads to desorption of the largest percentage of hydroxyl species from the SiO 2 surface, leaving about 1-3 OH/nm 2 [6]. This is a common treatment of silica supports during the industrial preparation of Ziegler-Natta catalysts [7,8].…”