1 Kinetics of Olefin Polymerization
Olefin polymerization kinetics are considered and discussed in many reviews [1–6].
In this section, the influence of the main parameters such as the concentrations
of catalysts and cocatalysts and time of polymerization on polymerization rate,
and the main reactions in the olefin polymerization process will be briefly reviewed.
We also consider the problems of deviation from the linear law of polymerization
rate with changing monomer concentration, the effect of hydrogen in the ethene and
propene polymerizations, as well as the nature of the comonomer effect, which are
under discussion in the literature and the natures of which are not yet completely
clear.
To describe the kinetics of olefin polymerization with heterogeneous catalysts,
kinetic models based on adsorption isotherm theories have been proposed [7–10].
The most accepted two-step mechanism of ZN polymerization, proposed by
Cossee [10–12], includes olefin coordination and migratory insertion of coordinated monomer into a metal–carbon bond of the growing polymer chain.
1.1 Influence of Catalyst and Cocatalyst Concentrations
The olefin polymerization rate with heterogeneous catalysts is directly proportional
to catalyst concentration [5, 13–15]. The concentration of metallorganic cocatalyst
does not affect the polymerization rate with TiCl 3 unless a too-high Al-alkyl
concentration is used [15, 16]. The catalysts based on VCl 3 are more sensitive to
the concentration and type of AlR 3 [17]. According to many observations, in the
case of MgCl 2 -supported catalyst, increasing the Al-alkyl concentration leads
to an increase in the maximum rate of polymerization and an increase in the
polymerization rate decay [5, 18, 19].
1.2 Main Reactions of Olefin Polymerization
Chain propagation:
Mt–CH 2 –CH(CH 3 )–Polymer þ CH 2 ═CH(CH 3 ) ! Mt–CH 2 –CH(CH 3 )–CH 2 –CH
(CH 3 )–Polymer
Polymer chain termination occurs mainly through the following reactions:
1. Transfer with monomer:
Mt–CH 2 –CH(CH 3 )–Polymer þ CH 2 ═CH(CH 3 ) ! Mt–CH 2 –CH 2 CH 3 +
CH 2 ═C(CH 3 )–Polymer
Kinetics of Olefin Polymerization and Active Sites of Heterogeneous Ziegler. . .
101
Olefin polymerization kinetics are considered and discussed in many reviews [1–6].
In this section, the influence of the main parameters such as the concentrations
of catalysts and cocatalysts and time of polymerization on polymerization rate,
and the main reactions in the olefin polymerization process will be briefly reviewed.
We also consider the problems of deviation from the linear law of polymerization
rate with changing monomer concentration, the effect of hydrogen in the ethene and
propene polymerizations, as well as the nature of the comonomer effect, which are
under discussion in the literature and the natures of which are not yet completely
clear.
To describe the kinetics of olefin polymerization with heterogeneous catalysts,
kinetic models based on adsorption isotherm theories have been proposed [7–10].
The most accepted two-step mechanism of ZN polymerization, proposed by
Cossee [10–12], includes olefin coordination and migratory insertion of coordinated monomer into a metal–carbon bond of the growing polymer chain.
1.1 Influence of Catalyst and Cocatalyst Concentrations
The olefin polymerization rate with heterogeneous catalysts is directly proportional
to catalyst concentration [5, 13–15]. The concentration of metallorganic cocatalyst
does not affect the polymerization rate with TiCl 3 unless a too-high Al-alkyl
concentration is used [15, 16]. The catalysts based on VCl 3 are more sensitive to
the concentration and type of AlR 3 [17]. According to many observations, in the
case of MgCl 2 -supported catalyst, increasing the Al-alkyl concentration leads
to an increase in the maximum rate of polymerization and an increase in the
polymerization rate decay [5, 18, 19].
1.2 Main Reactions of Olefin Polymerization
Chain propagation:
Mt–CH 2 –CH(CH 3 )–Polymer þ CH 2 ═CH(CH 3 ) ! Mt–CH 2 –CH(CH 3 )–CH 2 –CH
(CH 3 )–Polymer
Polymer chain termination occurs mainly through the following reactions:
1. Transfer with monomer:
Mt–CH 2 –CH(CH 3 )–Polymer þ CH 2 ═CH(CH 3 ) ! Mt–CH 2 –CH 2 CH 3 +
CH 2 ═C(CH 3 )–Polymer
Kinetics of Olefin Polymerization and Active Sites of Heterogeneous Ziegler. . .
101