Business and Technology of the Global Polyethylene Industry: An In-depth Look at the History, Technology, Catalysts, and Modern Commercial Manufacture of Polyethylene and Its Products

Chapter 2

Titanium-Based Ziegler Catalysts for the Production of Polyethylene

2.1 Introduction

Ethylene polymerization catalysts based on titanium as the active center are primarily used in the low-pressure manufacture of polyethylene with a relatively narrow molecular weight distribution to include both high density polyethylene (HDPE) and linear low density polyethylene (LLDPE). Table 2.1 summarizes a few examples of end-use applications for titanium-based polyethylene in terms of the density, molecular weight distribution and molecular weight for various applications.

Table 2.1 Examples of product applications for titanium-based catalysts.

2.2 Titanium-Based Catalyst Developments

2.2.1 Historical Developments

In the early 1950s, Ziegler and coworkers [1] were attempting to produce high molecular weight polyethylene by repetitive insertion of ethylene between the aluminum-carbon bond in triethylaluminum, as shown in the growth step (Equation 2.1), where R represents additional alkyl chains that are formed simultaneously.

(2.1)

A termination step (Equation 2.2) involving beta-hydride transfer to an aluminum atom leads to the formation of a vinyl-terminated polymer molecule and an Al-H bond, which can insert an ethylene molecule to initiate the growth of additional polymer species. ...