Chemistry Reference
In-Depth Information
ABSTRACT
The effect particle size of micro heterogeneous catalyst TiCl
4
−Al(iso-
C
4
H
9
)
3
on the basic patterns of isoprene polymerization is studied. Frac-
tion of particles with a certain size isolated from the mixture of particles,
which is formed by reacting the initial components of the catalyst and its
following exposition. The most active in isoprene polymerization is par-
ticles fraction with starting diameter of 0.7−4.5 μm. In these particles pref-
erably localized highly active polymerization site. Doping diphenyloxide
and piperylene, lower exposition temperature, hydrodynamic actions in
turbulent flows result in formation of nearly mono disperse catalyst with
diameter of 0.15−0.18 μm. In this case there is a shift in activity spectrum
of polymerization sites towards formation of single site with high activity.
PACS: 82.65.+r, 82.35.-
x
.
3.1 INTRODUCTION
The formation of highly stereo regular polymers under the action of micro
heterogeneous Ziegler-Natta catalysts is accompanied by broadening of the
polymer MWD [1, 2]. This phenomenon is related to the kinetic heterogeneity
of active sites (АС) [1, 3, 4]. The possible existence of several kinetically non-
equivalent AC of polymerization correlates with the nonuniform particle size
distribution of a catalyst [4]. At present time much attention is given to study
the influence of micro heterogeneous catalysts particle size on the properties
of polymers [5, 6]. However, almost no detailed study of the effect particle
size catalysts on their kinetic heterogeneity.
The micro heterogeneous catalytic system based on TiCl
4
and Al (iso-
C
4
H
9
)
3
that are widely used for the production of the cis-1,4-isoprene. The
research [7] show that the targeted change of the solid phase particle size
during the use of a tubular turbulent reactor at the stage of catalyst expo-
sure for many hours is an effective method for controlling the polymeriza-
tion process and some polymer characteristics of isoprene. We suppose
that the key factor is the interrelation between the reactivity of isoprene
polymerization site and the size of catalyst particles on which they local-
ize.
The aim of this chapter was to investigate the interrelation between
the particle size of a titanium catalyst and its kinetic heterogeneity in the
polymerization of isoprene.
