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ISSN 20700504, Catalysis in Industry, 2014, Vol. 6, No. 3, pp. 198–201. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © I.I. Salakhov, A.Z. Batyrshin, S.A. Sergeev, G.D. Bukatov, A.A. Barabanov, A.G. Sakhabutdinov, V.A. Zakharov, Kh.Kh. Gilmanov, 2014, published in
Kataliz v Promyshlennosti.
198
INTRODUCTION
Most of the world’s polypropylene is currently pro
duced with titaniumcontaining Ziegler–Natta catalysts
[1, 2]. Highperformance catalytic systems based on tita
nium chlorides deposited on magnesium dichloride have
found the widest industrial application in synthesizing
polypropylene with trialkylaluminum and electron
donor compounds, TiCl
4
/
D
1
/MgCl
2
+AlR
3
/
D
2
(where
D
1
and
D
2
denote internal and external donors, respec
tively) [3–15]. During polymerization in liquid mono
mer, socalled fourthgeneration Ziegler–Natta cata
lysts yield 30–60 kg of polymer per 1 g catalyst with
polypropylene isotacticity above 96 wt % [16]. In
industry, phthalates are used as internal donors while
alkylalkoxysilanes serve as external donors [17–19].
At present, there is no industrial production of
fourthgeneration catalysts in Russia. All domestic
manufacturers of polypropylene traditionally use cat
alysts recommended, produced, and/or sold by licens
ers of the process; i.e., they are imported [20, 21]. At
the same time, researchers at the Boreskov Institute of
Catalysis are developing stateoftheart Ti–Mg cata
lysts (
TM
Cs) for the polymerization of olefins, includ
ing propylene [22–24].
In this work, propylene polymerization in liquid
monomer was studied using the IK821 Ti–Mg cata
lyst synthesized at the Boreskov Institute of Catalysis
and a number of imported catalysts in order to deter
mine their catalytic properties and other features of
polypropylene synthesis.
EXPERIMENTAL
The IK821 Ti–Mg catalyst was prepared follow
ing the procedure described in [22]. The catalytic com
plex was synthesized by mixing calculated amounts of
trimethylaluminum solution (TEA) in dry
n
hexane,
cyclohexylmethyldimethoxysilane (donor
D
2
), and the
Ti–Mg catalyst in glass flasks with separation funnels
under an inert atmosphere. After introducing reagents
into the flasks, the contents were stirred for 5 min and
the catalytic complex was then loaded in reactor.
Propylene of polymerization purity (
OAO
Nizhne
kamskneftekhim) with a 99.8% volume fraction of the
main substance was used in the synthesis of polypro
pylene (PP). The following conditions were taken as
standard: mass of propylene = 1300 g; mass of
catalyst shot
m
cat
= 0.01 g; molar ratio Al : Ti = 1000;
molar ratio Al : Si = 20. The equivalent amount of
hydrogen (20 vol % in the gas phase) was initially
introduced in reactor in order to control the molecular
mass of the synthesized polymer. To prevent the
destruction of catalyst particles, preliminary polymer
ization under mild conditions was conducted at 20°C
for 5 min, and the temperature was then raised. The
polymerization of propylene was conducted in a
mC3H6
Polymerization of Propylene in Liquid Monomer Using
StateoftheArt HighPerformance Titanium–Magnesium Catalysts
I. I. Salakhov
a
, A. Z. Batyrshin
a
, S. A. Sergeev
b
, G. D. Bukatov
b
, A. A. Barabanov
b
,
A. G. Sakhabutdinov
a
, V. A. Zakharov
b
, and Kh. Kh. Gilmanov
a
a
OAO Nizhnekamskneftekhim, Nizhnekamsk, 423574 Russia
b
Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
email: SalahovII@nknh.ru; i.i.salahov@gmail.com; bukatov@catalysis.ru; zva@catalysis.ru
Received January 20, 2014
Abstract
—A comparative study of propylene polymerization in liquid monomer is performed under labora
tory conditions using the IK821 Ti–Mg catalyst designed at the Boreskov Institute of Catalysis and
imported industrial catalysts (conditionally labeled
TM
C1, 2, and 3). The activity and stereospecificity of
the catalysts are estimated along with properties of the resulting polypropylene (granular composition and
physicomechanical characteristics). It is shown that the IK821 catalyst is not inferior to imported counter
parts in terms of catalytic properties in the synthesis of polypropylene. The polypropylene powder formed on
IK821 is homogeneous and has good morphology. The physicomechanical characteristics of polypropylene
synthesized on the domestic IK821 catalyst are similar to those for polypropylene prepared with the
imported
TM
K1 catalyst.
Keywords:
Ti–Mg catalyst, propylene, polymerization, polypropylene, isotacticity, granulation, physical and
mechanical properties
DOI:
10.1134/S2070050414030106
CATALYSIS IN CHEMICAL
AND PETROCHEMICAL INDUSTRY
CATALYSIS IN INDUSTRY Vol. 6 No. 3 2014
POLYMERIZATION OF PROPYLENE IN LIQUID MONOMER 199
5dm
3
autoclave using liquid monomer at a polymer
ization temperature (
T
pm
) of 70°C and pressure (
P
pm
)
of 30 kgf/cm
2
. The duration of propylene polymeriza
tion (
τ
pm
) was 120 min.
Polypropylene isotacticity was determined using a
procedure based on dissolving a shot of polyolefin in
o
xylene, cooling the solution to 25°C under con
trolled conditions, filtering the solid phase, distilling
the
o
xylene from solution, and measuring the mass of
the dissolved substances.
The size of polypropylene powder particles was
determined by measuring the grains; the tap density of
the PP powder corresponded to GOST 11035.1–93.
The melting point and crystallinity were measured via
differential scanning calorimetry (DSC) on a Netzsch
DSC 204F1 Phoenix unit in accordance with
ASTM E 794–85.
The melt flow index (MFI) of the polymer was
measured on a RayRan extrusion rheometer accord
ing to ASTM 1238 at 230°C and a constant load of
2.16 kg. The Izod impact strength was determined
according to ASTM D 256; the bend elasticity modu
lus, according to ASTM D 790; and the tensile yield
limit upon stretching and the relative elongation at the
tensile yield limit, according to ASTM D 638.
RESULTS AND DISCUSSION
For our comparative study, we chose imported the
industrial fourthgeneration Ti–Mg catalysts
ТМC
1,
TMC2, and
TMC
3 from leading European manu
facturers. These are commonly used in the produc
tion of polypropylene and allow us to obtain a wide
assortment of branded polyolefins. Basic data on the
IK821,
ТМC
1, 2, and 3 Ti–Mg catalysts are
given in Table 1.
All samples of the Ti–Mg catalysts were character
ized by having phthalatetype internal donor
D
1
. The
titanium content in the TMC samples was 2.4–2.9 wt %;
that of magnesium was 16–22 wt %. The mean parti
cle size of the investigated catalysts differed on average
from 30 to 50
μ
m.
In studying catalysts of polypropylene synthesis, we
must consider the requirements made of them: high
activity; high stereoregularity of the resulting PP;
enhanced morphology of the PP powder, i.e., low con
tent of the fine (<200
μ
m) fraction in the polymer; and
susceptibility to chain regulators (e.g., hydrogen) and
comonomers.
The data presented in the figure allow us to com
pare the activities of imported industrial TMC1, 2, 3,
and domestic IK821 Ti–Mg catalysts, obtained at
the laboratory of the Boreskov Institute of Catalysis.
The results from our analysis of the polypropylene
formed on the investigated catalysts are also given in
the figure for the content of atactic fraction. Our
results from studying propylene polymerization in liq
uid monomer show that the IK821 Ti–Mg catalyst
has activity similar to that of TMC samples and results
in high yields of polymer: for TMC samples, the activ
ity was 36–55 kg PP/g cat.; for IK821 catalyst, it
was 48 kg PP/g cat. The polymerization of propylene
in liquid monomer in this case proceeds in a stable
manner both on the IK821 and TMC1, 2, and 3
catalysts. In addition, 0.460–0.480 g/cm
3
of homoge
neous PP powder with high tap density are formed
(Table 2).
The isotacticity of polypropylene samples obtained
with the IK821 catalyst was also high, and the con
tent of the atactic fraction was 2.3 wt % (see figure).
For PP samples prepared on TMC1, 2, and 3, the
content of atactic fraction ranges from 2.1 to 8.2 wt %,
all other conditions being equal. It is well known that
the isotacticity of polypropylene can be controlled by
varying the concentration of the external electron
donor compound
D
2
; however, an increase in the con
tent of
D
2
in the polymerization system would be
accompanied by a drop in the activity of the catalyst.
The granular characteristics of the formed powder
are of great importance in the industrial production of
PP, since the stability of an installation’s operation
depends on them. It is essential that a catalyst ensures
the optimum mean particle size and forms a smaller
number of fine polymer fractions. Estimates of the
granular composition of polypropylene powders formed
on the investigated catalysts showed that the mean size
of PP powder particles synthesized with IK821 was
1030
μ
m, while those of PP powder particles obtained
on TMC1 (1380
μ
m) and TMC3 (1920
μ
m) were
considerably larger (Table 2). This difference was due
to the difference between the initial particle sizes of
Table 1.
Characteristics of the catalysts of polypropylene synthesis studied in this work
Parameter Imported industrial catalysts Domestic laboratory
catalyst
TMC1 TMC2 TMC3 IK821
Composition TiCl
4
/phthalatetype donor
D
1
/MgCl
2
Titanium content, wt % 2.5 2.4 2.9 2.8
Magnesium content, wt % 19 16 22 20
Mean particle size of catalyst,
µ
m 43–48 30–35 48–52 34–36
200
CATALYSIS IN INDUSTRY Vol. 6 No. 3 2014
SALAKHOV et al.
each catalyst; the bulkier the catalyst particles (see
Table 1), the greater the particle size of the formed
polypropylene. The particle sizes of TMC2 (30–
35
μ
m) and IK821 (34–36
μ
m) catalysts were simi
lar, so the mean particle sizes of PP powders obtained
on them were nearly identical (1020 and 1030
μ
m,
respectively). At the same time, the content of fine
(<200
μ
m) particles in the polypropylene powders was
different: during polymerization with the IK821 cat
alyst, we have a lower content of the fine fraction than
with TMC2 (0.8 and 4.3 wt %, respectively). We
should note that the method of preparing IK821
allows us to control the mean particle size of the cata
lyst in the range of 15 to 65
μ
m while preserving the
narrow particle size distribution and the lack of a dust
fraction in the polymer.
The polypropylene samples obtained on IK821
and TMC1, 2, and 3 were similar in their melting
points and crystallinities (see Table 2).
CONCLUSIONS
Our study of the physicomechanical properties of
polypropylene samples obtained on the
TMK
1 and
IK821 catalysts showed that at similar melt flow
rates, PP samples synthesized on the IK821 catalyst
were not inferior to those obtained on TMC1 in terms
of their physicomechanical characteristics (Table 3).
80
60
40
20
0TMC3TMC2TMC1
10
8
6
4
2
0
IK821
Activity of catalyst, kg PP/g catalyst
Content of atactic fraction, wt %
—Activity of catalyst —Content of atactic fraction
44
2.1
36
3.4
55
8.2
48
2.3
Activity of imported
TM
C1, 2, 3 industrial catalysts and domestic IK821 laboratory catalyst designed at the Boreskov Insti
tute of Catalysis, used for propylene polymerization in liquid monomer, and the content of atactic fraction in PP samples
.
Poly
merization conditions:
T
pm
= 70°C,
P
pm
=30kgf/cm
2
, = 1300 g,
m
cat
= 0.01 g, Al/Ti = 1000 (mol), TEA/donor =
20 (mol), and
τ
pm
=120min.
mC3H6
Table 2.
Characteristics of polypropylene powders (PPs) prepared on the imported (TMC1, 2, 3) and domestic (IK821)
catalysts
Parameter Characteristics of PP powders
Used catalyst TMC1 TMC2 TMC3 IK821
Appearance of prepared PP powder Homogeneous white powder
with spherical particles
Homogeneous white
powder with raspberry
shaped particles
Tap density, g/cm
3
0.460 0.465 0.470 0.470
Mean particle size,
µ
m 1380 1020 1920 1030
Amount of fine fractions (less than 200
µ
m), % 0.6 4.3 0.3 0.8
Melt flow index (2.16 kg/230
°
C), g/10 min 8.0 7.5 10.0 6.5
Melting point,
°
C 164 166 165 166
Crystallinity, % 32 30 27 30
CATALYSIS IN INDUSTRY Vol. 6 No. 3 2014
POLYMERIZATION OF PROPYLENE IN LIQUID MONOMER 201
Our studies showed that the IK821 Ti–Mg cata
lyst designed at the Boreskov Institute of Catalysis,
Siberian Branch, Russian Academy of Sciences, is not
inferior to its imported counterparts. The IK821
catalyst exhibits high activity and stereospecificity
during propylene polymerization in liquid monomer.
The resulting polypropylene powder is homogeneous
and has good morphology. The physicomechanical
characteristics of polypropylene synthesized on the
domestic IK821 Ti–Mg catalyst are similar to those
for polypropylene prepared with the imported TMC1
catalyst.
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Translated by A. Muravev
Table 3.
Physicomechanical properties of polypropylene
(PP) samples obtained on the MTC1 and IK821 catalysts
Parameter PP prepared on
TMC1 IK821
Melt flow index
(2.16 kg/230°C), g/10 min 3.1 3.0
Bend elasticity modulus, MPa 1600 1630
Izod impact strength
at 23
°
C, J/m 82 99
Tensile yield limit, MPa 35 35
Relative elongation at tensile yield
limit, % 11 11