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2 Zeigler-Natta Catalyst
The commercial viability of PE took a revolutionary leap in 1953 after the momentous invention of a versatile organometallic catalyst for polymerization of ethylene
by Karl Waldemar Ziegler of the Kaiser Wilhelm Institute and Erhard Holzkamp.
Ziegler utilized a binary mixture of transition metal halides of group IV and metal
alkyls of group I to III, typically TiCl 4 and AlEt 3 to polymerize ethylene under normal pressure and room temperature conditions [1]. The procedure was able to minimize the branching and produced high-density polyethylene (HDPE). Soon after
this invention, Giulio Natta and coworkers further demonstrated the versatility of
this catalyst and trivalent titanium chloride-based system to polymerize different
α-olefins such as propylene and butylene to produce stereoregular isotactic polymers [2]. This path-breaking invention led to development of commercial plastics
and elastomers, and living cationic, anionic, and radical polymerizations evolved
with time, expanding the research and development on synthetic high polymers.
The income earned from his patents ensured financial independence and further
expansion of the Institute of which he was the Director.
Since 1955, the scientific literature exploded especially with several thousands
of reports on utilization of these catalysts for polymerization of a range of olefins
and dienes and further modification of the catalyst to improve the versatility and
efficiency. This chemistry associated with the name of Karl Ziegler is considered as
one of the “historical landmarks in chemistry,” and in recognition to their efforts,
both Professor K. Ziegler and G. Natta were honored with the prestigious Nobel
Prize in Chemistry in 1963. In general, though the number of variations in transition
and alkyl metals is large, the number of useful combinations for efficient catalysis
is limited. Titanium and vanadium have so far displayed excellent activity, and zirconium, hafnium, and tungsten have shown promise for future development.
Similarly, in case of alkyl metals, aluminum have been outstanding and utilized in a
number of catalyst compositions followed by magnesium and zinc in selective
cases. The versatility of this Ziegler-Natta catalyst is ascertained to the number of
monomers these catalyst systems can efficiently polymerize and the number of different products those can be obtained from each monomer.
2.1 Mechanism of Polymerization
Several mechanistic pathways are proposed in the literature towards the polymerization of olefins in presence of Ziegler-Natta catalyst. Most of the reports agree to
one general aspect of the polymerization, i.e., the polymerization occurs through
insertion of olefin monomer between the metal atom and one of the alkyl groups of
Evolution of Ziegler-Natta Catalysts for Polymerization of Olefins
2 Zeigler-Natta Catalyst
The commercial viability of PE took a revolutionary leap in 1953 after the momentous invention of a versatile organometallic catalyst for polymerization of ethylene
by Karl Waldemar Ziegler of the Kaiser Wilhelm Institute and Erhard Holzkamp.
Ziegler utilized a binary mixture of transition metal halides of group IV and metal
alkyls of group I to III, typically TiCl 4 and AlEt 3 to polymerize ethylene under normal pressure and room temperature conditions [1]. The procedure was able to minimize the branching and produced high-density polyethylene (HDPE). Soon after
this invention, Giulio Natta and coworkers further demonstrated the versatility of
this catalyst and trivalent titanium chloride-based system to polymerize different
α-olefins such as propylene and butylene to produce stereoregular isotactic polymers [2]. This path-breaking invention led to development of commercial plastics
and elastomers, and living cationic, anionic, and radical polymerizations evolved
with time, expanding the research and development on synthetic high polymers.
The income earned from his patents ensured financial independence and further
expansion of the Institute of which he was the Director.
Since 1955, the scientific literature exploded especially with several thousands
of reports on utilization of these catalysts for polymerization of a range of olefins
and dienes and further modification of the catalyst to improve the versatility and
efficiency. This chemistry associated with the name of Karl Ziegler is considered as
one of the “historical landmarks in chemistry,” and in recognition to their efforts,
both Professor K. Ziegler and G. Natta were honored with the prestigious Nobel
Prize in Chemistry in 1963. In general, though the number of variations in transition
and alkyl metals is large, the number of useful combinations for efficient catalysis
is limited. Titanium and vanadium have so far displayed excellent activity, and zirconium, hafnium, and tungsten have shown promise for future development.
Similarly, in case of alkyl metals, aluminum have been outstanding and utilized in a
number of catalyst compositions followed by magnesium and zinc in selective
cases. The versatility of this Ziegler-Natta catalyst is ascertained to the number of
monomers these catalyst systems can efficiently polymerize and the number of different products those can be obtained from each monomer.
2.1 Mechanism of Polymerization
Several mechanistic pathways are proposed in the literature towards the polymerization of olefins in presence of Ziegler-Natta catalyst. Most of the reports agree to
one general aspect of the polymerization, i.e., the polymerization occurs through
insertion of olefin monomer between the metal atom and one of the alkyl groups of
Evolution of Ziegler-Natta Catalysts for Polymerization of Olefins