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Polymerization of propylene in liquid monomer using state-of-the-art high-performance titanium-magnesium catalysts

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A comparative study of propylene polymerization in liquid monomer is performed under laboratory conditions using the IK-8-21 Ti-Mg catalyst designed at the Boreskov Institute of Catalysis and imported industrial catalysts (conditionally labeled TMC-1, -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 IK-8-21 catalyst is not inferior to imported counterparts in terms of catalytic properties in the synthesis of polypropylene. The polypropylene powder formed on IK-8-21 is homogeneous and has good morphology. The physicomechanical characteristics of polypropylene synthesized on the domestic IK-8-21 catalyst are similar to those for polypropylene prepared with the imported TMK-1 catalyst. © Pleiades Publishing, Ltd., 2014. © 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.
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ISSN 20700504, 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 titaniumcontaining Ziegler–Natta catalysts
[1, 2]. Highperformance 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, socalled fourthgeneration 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
fourthgeneration 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 stateoftheart 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 IK821 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 IK821 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
StateoftheArt HighPerformance 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
email: 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 IK821 Ti–Mg catalyst designed at the Boreskov Institute of Catalysis and
imported industrial catalysts (conditionally labeled
TM
C1, 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 IK821 catalyst is not inferior to imported counter
parts in terms of catalytic properties in the synthesis of polypropylene. The polypropylene powder formed on
IK821 is homogeneous and has good morphology. The physicomechanical characteristics of polypropylene
synthesized on the domestic IK821 catalyst are similar to those for polypropylene prepared with the
imported
TM
K1 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
5dm
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 RayRan 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 fourthgeneration Ti–Mg catalysts
ТМC
1,
TMC2, 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
IK821,
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 phthalatetype 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
comonomers.
The data presented in the figure allow us to com
pare the activities of imported industrial TMC1, 2, 3,
and domestic IK821 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 IK821 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 IK821 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 IK821 and TMC1, 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 IK821 catalyst was also high, and the con
tent of the atactic fraction was 2.3 wt % (see figure).
For PP samples prepared on TMC1, 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 IK821 was
1030
μ
m, while those of PP powder particles obtained
on TMC1 (1380
μ
m) and TMC3 (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
TMC1 TMC2 TMC3 IK821
Composition TiCl
4
/phthalatetype 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 TMC2 (30–
35
μ
m) and IK821 (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 IK821 cat
alyst, we have a lower content of the fine fraction than
with TMC2 (0.8 and 4.3 wt %, respectively). We
should note that the method of preparing IK821
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 IK821
and TMC1, 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
IK821 catalysts showed that at similar melt flow
rates, PP samples synthesized on the IK821 catalyst
were not inferior to those obtained on TMC1 in terms
of their physicomechanical characteristics (Table 3).
80
60
40
20
0TMC3TMC2TMC1
10
8
6
4
2
0
IK821
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
C1, 2, 3 industrial catalysts and domestic IK821 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 (TMC1, 2, 3) and domestic (IK821)
catalysts
Parameter Characteristics of PP powders
Used catalyst TMC1 TMC2 TMC3 IK821
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 IK821 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 IK821
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 IK821 Ti–Mg catalyst are similar to those
for polypropylene prepared with the imported TMC1
catalyst.
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Translated by A. Muravev
Table 3.
Physicomechanical properties of polypropylene
(PP) samples obtained on the MTC1 and IK821 catalysts
Parameter PP prepared on
TMC1 IK821
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
... IK-8-21 magnesium-titanium catalyst (MTC) was developed at the Boreskov Institute of Catalysis for the PP polymerization process [4,5]. A number of tests were performed with catalysts for the polymerization process in a liquid monomer and they showed that IK-8-21 catalyst is not inferior to its foreign analogues in terms of activity and the quality of the resulting PP [6]. ...
Article
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The effect of the particle size of an IK-8-21 domestic titanium-magnesium catalyst on the properties of polypropylene (PP) produced during the polymerization of propylene in a liquid monomer is studied. Catalysts with particle sizes of 20 to 64 μm are shown to have high activity and identical sensitivity to hydrogen and allow PP to be obtained with a narrow distribution of particles over size, high isotacticity, and close values of crystallinity, melting temperature, and physicomechanical properties. A slight decrease in the activity and bulk density of PP powder is observed when the average size of catalyst particles is increased from 20 to 43 μm. A more notable reduction in the activity and bulk density of PP powder is observed for catalyst with particle sizes of 62 to 64 μm. IK-8-21 catalyst is not inferior to its foreign analogues with respect to the properties of the resulting PP.
Article
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The effect of polymerization conditions (temperature, polymerization time, monomer and hydrogen concentrations) on propylene polymerization in the liquid monomer in the presence of a TiCl4/DBP/MgCl2 + TEA/cyclohexylmethyldimethoxysilane catalyst system is studied . It is shown that the variation of the propylene polymerization conditions in the studied ranges leads to a change in the characteristics of the resulting polypropylene. The kinetic parameters of propylene polymerization in the liquid monomer for the studied catalyst system are determined. Polymerization conditions providing the formation of polypropylene with high polymer yield, isotacticity, and bulk density values are found. The process parameters that make it possible to effectively control the molecular and rheological characteristics of polypropylene are identified.
Article
Two new ethers were synthesized using the Williamson reaction from related alcohols and were used as external donors in propylene polymerization in the presence of the industrial diisobutyl phthalate-based MgCl2-supported Ziegler-Natta catalyst. For comparison the propylene polymerization was carried out in the presence of silane and in the absence of external donors. The produced polymers were characterized by differential scanning calorimetry, xylene extraction, melt flow index, scanning electron microscopy and gel permeation chromatography. The isotacticity, molecular weight and molecular weight distribution, melt flow index, crystallinity degree and thermal properties of polypropylenes were influenced by the type of external donors.
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Current production of polyethylene (PE) and polypropylene (PP) is ∼ 80 million ton/yr, translating into a catalyst business of ∼ 6000 ton, depending on the activity of the catalyst used. The 1990s brought two major thrusts in polyolefin polymerization, i.e., single catalysis, including the metallocene catalysts, for both PE and PP, and the development of bimodal PE, with closely controlled molecular weight distribution. Most of the leading catalyst producers keep close contact with end-users, the polymer converters and even major users, to assess requirements, and indeed in most cases are producers of themselves, e.g., Basell, Borealis, and Equistar. Univation Technologies has close interactions with two equal shareholders Dow Chemical and ExxonMobil Chemical, both major polyolefin producers. Basell is the leading PP catalyst producer, supplying a third of the world's capacity. Basell is broadening its Avant ZN family of Z-N catalysts to offer four types, so it can meet most PP producers' needs.
Article
The chain transfer reaction with hydrogen at propylene polymerization over Ti-Mg catalysts (TMCs) of composition TiCl4/D1/MgCl2-AlEt3/D2 is studied in a wide hydrogen concentration range. A two-step mechanism of this reaction is suggested. This mechanism accounts for the fractional order of the reaction with respect to hydrogen concentration. Constants of chain transfer reaction with hydrogen are determined for TMC with different donors: 1,3-diether or dibutyl phthalate as D1 and tetraethoxysilane or dicyclopentyldimethoxysilane as D2. In propylene polymerization over the TMCs, the length of the polymer chain is mainly determined by the ratio of the propylene and hydrogen concentrations because the propagation and chain transfer rate constants are comparable. The rate constant of chain transfer with hydrogen at ethylene polymerization is significantly (more than one order of magnitude) less, and higher hydrogen concentrations are required for attaining the same degree of polymerization. The results of this study might be helpful in simulation of industrial polymerization processes and in control of the polymer molar mass.
Article
A study has been made of the polymerization of liquefied propylene using a catalyst system based on titanium and magnesium. Included is the dependence of the activity and stereospecificity of the catalyst on the concentration of triethyl aluminium (electron donor) and the time and temperature of polymerization.
Article
The most advanced catalysts, based on MgCl2-supported TiCl4 and electron donors, are able to provide polypropylenes with an isotacticity higher than 99%. This, together with the continuous progress made in understanding and exploiting the role of electron donors in controlling polymer MW and MWD, has led to polypropylene products having an unprecedented level of stiffness or stiffness/impact balance. On the other hand, other potential fields of application exist where rigidity is not required and, actually, the key property is softness rather than stiffness. As a matter of fact, it has clearly been established that soft polypropylenes can be more attractive from the business standpoint than their stiff counterparts. Generally, these materials are multiphase copolymers obtained via sequential gas-phase copolymerization of propylene and ethylene-propylene mixtures using the morphology-controlled conventional MgCl2-TiCl4 catalysts based on the couple phthalatesilane as internal and external donors. This communication deals with a new class of donors that can be used either as external donors in combination with phthalates (A) or as internal/external donors (B). When combined with the MgCl2-TiCl4 systems, both donors substantially improve the flexibility and softness of the resulting soft materials while maintaining the operability window of the Catalloy process. This is due to the particular microstructure of the relevant building blocks: the presence of a controlled concentration of stereodefects in the homopolymer fraction, and good comonomer distribution in the copolymer fraction. As compared with the conventional products, the new ones show comparable or better flexibility when the rubber phase is relatively rich in ethylene. This likely opens the door for these products to enter the demanding thermoplastic elastomers (TPE) application field.
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