Simple and Strong Dative Attachment of α-Diimine Nickel (II) Catalysts on Supports for Ethylene Polymerization with Controlled Morphology

Article abstract of DOI:10.1007/s10562-020-03116-z

Abstract: In this article, preparation of novel spherical MgCl₂ supported α-diimine nickel (II) catalysts for ethylene polymerization in slurry phase is reported. α-Diimine ligands were synthesized by condensation reaction of 2, 6-disubstituted alkyls or aryls anilines and Ace naphthoquinone Which have hydroxyl functionality in their para-position. Hydroxyl functionalized α-diimine attached strongly on to the spherical MgCl₂ support surface by dative bonding. No linker was needed to attach the complexes onto the support surface and the amount of loaded Nickel was controllable to improve morphology and especially bulk density of polymer powder. A significant reduction in catalysts activity has happened when homogeneous catalysts were supported onto silica but this reduction was decreased when they were supported onto thermally treated spherical MgCl₂. As homogeneous bis(N,N′-(4-(3-hydroxyl-propyl)-2,6-di[(4-tert-butyl-phenyl)-phenyl) amino] Ace naphthoquinone Nickel dibromide(d) showed the highest activity among other evaluated homogeneous catalysts, its MgCl₂ supported catalyst (d/S-MgCl₂) has shown the highest activity among MgCl₂ supported catalysts too. These MgCl₂ supported catalysts were pre-polymerized in presence of ethylene monomer in the mild polymerization condition to yield a pre-polymerized catalyst with polymer/catalyst weight ratio equal to six. Ethylene polymerization was carried out to make spherical particles of polyethylene without reactor fouling by these pre-polymerized catalysts. Clearly, it is shown in SEM images that the spherical morphology of MgCl₂ support is replicated in the produced polymer. The molecular weight and molecular weight distribution of produced polymer with MgCl₂ supported catalysts were higher than those produced by homogeneous catalysts. Graphic Abstract: α–Diimine nickel (II) complexes have hydroxy functionality where produce strong dative bonding onto spherical MgCl₂. This bonding is strong enough that these catalysts are suitable for slurry polymerization of ethylene without reactor fouling due to catalyst leaching from support. The chemical structure of MgCl₂ leads to high active supported catalysts. The molecular weight and polydispersity index of produced polymrers using these supported catalysts are higher than those produced by equivalent homogeneous catalysts and are controllable by selection of appropriate ligand for used α–diimine nickel (II) complex or hydrogen concentration in ethylene polymerization.[Figure not available: see fulltext.].

Full text of DOI:10.1007/s10562-020-03116-z

Catalysis Letters
https://doi.org/10.1007/s10562-020-03116-z
Simple and Strong Dative Attachment of α‑Diimine Nickel (II) Catalysts
on Supports for Ethylene Polymerization with Controlled Morphology
Ehsan Kianfar1,2 · Reza Azimikia1 · Seyed Mohammad Faghih3
Received: 27 November 2019 / Accepted: 17 January 2020
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
In this article, preparation of novel spherical MgCl2 supported α-diimine nickel (II) catalysts for ethylene polymerization
in slurry phase is reported. α-Diimine ligands were synthesized by condensation reaction of 2, 6-disubstituted alkyls or
aryls anilines and Ace naphthoquinone Which have hydroxyl functionality in their para-position. Hydroxyl functionalized
α-diimine attached strongly on to the spherical MgCl2 support surface by dative bonding. No linker was needed to attach the
complexes onto the support surface and the amount of loaded Nickel was controllable to improve morphology and especially
bulk density of polymer powder. A signifcant reduction in catalysts activity has happened when homogeneous catalysts were
supported onto silica but this reduction was decreased when they were supported onto thermally treated spherical MgCl2.
As homogeneous bis(N,N′-(4-(3-hydroxyl-propyl)-2,6-di[(4-tert-butyl-phenyl)-phenyl) amino] Ace naphthoquinone Nickel
dibromide(d) showed the highest activity among other evaluated homogeneous catalysts, its MgCl2 supported catalyst (d/S-
MgCl2) has shown the highest activity among MgCl2 supported catalysts too. These MgCl2 supported catalysts were pre-
polymerized in presence of ethylene monomer in the mild polymerization condition to yield a pre-polymerized catalyst with
polymer/catalyst weight ratio equal to six. Ethylene polymerization was carried out to make spherical particles of polyethylene
without reactor fouling by these pre-polymerized catalysts. Clearly, it is shown in SEM images that the spherical morphology
of MgCl2 support is replicated in the produced polymer. The molecular weight and molecular weight distribution of produced
polymer with MgCl2 supported catalysts were higher than those produced by homogeneous catalysts.
* Ehsan Kianfar
ehsan_kianfar2010@yahoo.com; e-kianfar94@iau-arak.ac.ir
1
Department of Chemical Engineering, Arak Branch, Islamic
Azad University, Arak, Iran
2
Young Researchers and Elite Club, Gachsaran Branch,
Islamic Azad University, Gachsaran, Iran
3
Department of Chemical Engineering, Susangerd Branch,
Islamic Azad University, Susangerd, Iran
Vol.:(0123456789)
1 3

E. Kianfar et al.
Graphic Abstract
α–Diimine nickel (II) complexes have hydroxy functionality where produce strong dative bonding onto spherical MgCl2. This
bonding is strong enough that these catalysts are suitable for slurry polymerization of ethylene without reactor fouling due
to catalyst leaching from support. The chemical structure of MgCl2 leads to high active supported catalysts. The molecular
weight and polydispersity index of produced polymrers using these supported catalysts are higher than those produced by
equivalent homogeneous catalysts and are controllable by selection of appropriate ligand for used α–diimine nickel (II)
complex or hydrogen concentration in ethylene polymerization.
Keywords Supported catalysts · Ni diimine · Ethylene polymerization
1 Introduction
polyethylene on the reactor wall and stirrer, which decreases
heat removing rate and (2) a signifcant decrease in cata-
lyst activity. Covalently attaching of active centers on the
support is a common approach to overcome these obsta-
cles so that researchers used chemically treated supports
with aluminum alkyl derivatives to make covalently link
betwe`en support and α-diimine Ni(II) catalysts [11–15].
These covalently attached supported catalysts were shown
good performances in gas and slurry phase polymerization
[16, 17]. Homogenous and appropriate fragmentation of sup-
ported catalysts in polymerization process led to the reduc-
tion of fne particles portion in produced polymer but the
morphology of produced polymer by these supported cata-
lysts was not as good as that produced by spherical MgCl2
supported catalysts [18]. In another procedure, α-diamine
Ni(II) complexes were reacted with MAO which then was
added to the slurry of support in a solvent [19–22]. These
procedures have been mostly used for catalysts. The obtained
data showed that supported late transition metal catalysts by
these methods would have low activity [4, 6, 23]. To over-
come this disadvantage, several research groups reported
new methods to attach α-diimine Ni(II) complexes onto
MgCl2 support surface covalently [24–27]. These supported
catalysts were prepared by reaction of α-diimine Ni(II) com-
plexes containing hydroxyl or amino functionality and SiO2
which were pretreated with aluminum alkyl derivatives [28,
Since the discovery of late transition metal catalysts for ole-
fns polymerization by Brookhart, these kinds of catalysts
have been interested due to their unique and potential ability
to chain walking and produce tailored branch polyethylene
from ethylene alone. Despite their versatile advantages, one
major drawback to the commercialization of Brookhart cata-
lysts is their rapid and quantitative deactivation in the pres-
ence of hydrogen, which is unavoidable for molecular weight
control in technical polymerization processes. Recently,
Rigger and coworkers reported new polychromatic, highly
active and hydrogen-stable Ni(II) complexes [1, 2]. On the
other hand, these new late transition metal catalysts have
to support a suitable carrier if they want to apply in indus-
trial processes [3–5]. Many diferent procedures were intro-
duced for preparing supported catalyst using silica, MgCl2
or SiO2/MgCl2 supports. Silica supports and silica/magne-
sium chloride supports are commonly used as appropriate
supports for Ziegler–Natta and Metallocene catalysts [4, 6,
7] and recent late transition metal catalysts [8, 9]. In some
articles, late transition metal catalysts were impregnated
on the surface of support physically [10]. In polymeriza-
tion condition, leaching of catalyst from support is one of
the limitations of physically supported late transition metal
catalysts [11–14]. This event leads to (1) agglomeration of
1 3

Simple and Strong Dative Attachment of α‑Diimine Nickel (II) Catalysts on Supports for Ethylene…
29]. The most efcient support that has created a revolu-
tion in Ziegler–Natta catalysts for ethylene polymerization
is MgCl2 and morphology of polymer particles has been
one of the most important issues in the polymerization of
ethylene. Several diferent procedures were employed to
prepare MgCl2 support to enhance Ziegler–Natta catalysts
performance and polymer morphology. Yiyoung et al. [3]
and Severn et al. [18] used MgCl2 as support for late transi-
tion metal catalysts. Soars and coworkers crystallized MgCl2
from MgCl2/heavy alcohol adducts by reaction with alkyl
aluminum and then supported α-diimine Ni(II) complexes
through an amino functionality onto the support. Cova-
lently bonded α-diimine catalysts to the support surface
prevented leaching of catalysts during ethylene polymeriza-
tion in slurry phase. Their results showed that MgCl2 sup-
ported α-diimine catalysts have higher activity compared to
SiO2 supported catalysts, for the same α-diimine catalysts.
In another procedure, Chadwick and coworkers supported
α-diimine Ni(II) complexes on MgCl2 by a simple proce-
dure [30, 31]. In this procedure, spherical MgCl2/ethanol
adduct was reacted with aluminum alkyls to produce spheri-
cal support of composition MgCl2·0.24Al (Et) 2.3(OEt) 0.7.
Immobilization of α-diimine Ni(II) catalysts with methyl and
isopropyl substituents in the Orth positions of the aryl rings
on MgCl2 led to an increase in ethylene polymerization rate
compared to those reported for catalysts prepared using sil-
ica support. The molecular weight distribution of produced
polyethylene by this immobilized catalyst was narrow [32,
33]. The data show that this preparation procedure, conserve
single-site characterization of these supported catalysts. In
this work, a simple and efcient procedure is introduced
for heterogenization of α-diimine Ni(II) catalysts on MgCl2
support with spherical morphology and good mechanical
properties. Spherical MgCl2·nEtOH was prepared using
the presented method in previous articles [34, 35]. Spheri-
cal MgCl2 support was thermally treated to decrease alco-
hol content and increase the surface area and mechanical
properties of the support. The dealcoholized spherical
MgCl2·nEtOH was directly used as a support for α-diimine
Ni(II) catalysts (Fig. 1) that have hydroxyl functionality in
para-position of their aryl rings. The hydroxyl groups were
attached to the support without any chemical treatment of
the surface. In addition, the infuence of ligand structure
and the type of support on the polyethylene properties and
polymer particle morphology were evaluated with electron
microscopy experiments. The most important perspective
has been the synthesis of the hydroxy functionalized steric
bulky α-diimine ligand with 4-butyl phenyl substituents to
improve catalyst activity in presence of hydrogen as well as
its thermal stability and The molecular weight and molecular
weight distribution of produced polymer with MgCl2 sup-
ported catalysts were higher than those produced by homo-
geneous catalysts.
Fig. 1 α-Diimine nickel (II)
catalysts
1 3

E. Kianfar et al.
obtained from Bandar Imam Petrochemical Co, from
HDPE unit. 2,6-diphenylaniline, 2,6-di(4-tert-butyl phe-
nyl)aniline, N-heterocyclic carbon palladium complex,
Ionic liquid matrix immobilized on silica and α-diimine
complexes and intermediate materials for the synthesis of
a to d were synthesized [26].
2 Experimental
2.1 Materials and Methods
The water content of solvents and reagents should be
lower than 5 ppm. Reagents were added to the reaction
vessels under a nitrogen blanket. The nitrogen was dried
by passing through the columns of molecular sieve 13XA
with an average pore diameter 3–4 Å. Syntheses of oxy-
gen and water sensitive materials were carried out under
dried nitrogen by dried glassware. The water content
of methylene dichloride (CH2Cl2) and the other solvent
like diethyl ether, hexane and toluene were reduced to
an acceptable amount. The synthesized compound and
sensitive material were manipulated in a nitrogen-filled
glovebox at ambient temperature. Aniline, 2,6-diisopro-
pylaniline, 2,6-dimethylaniline, nickel bromide acenaph-
thenequinone, lithium aluminium hydride, palladium ace-
tate, tri-ethyl amine, methyl acrylate, 10% palladium on
activated carbon, bromine, and acetic acid were purchased
from Merck Chemical Co. Silica gel (mesh 300–425) and
Anhydrous magnesium chloride were purchased from
Grace Davison and Aldrich Co. respectively. Hexane
(was used after passing over molecular sieves (4 Å) and
Na), hydrogen and polymerization grade ethylene were
3 Results and Discussion
3.1 Ligands and Complexes Synthesis
2,6-Dimethyl and diisopropyl anilines were purchased and
used directly. 2,6-Diphenyl-substituted anilines were syn-
thesized in agreement with literature procedure reported by
Reiger et al. [1]. Based on the procedure, the bromination,
Grignard and Suzuki cross coupling reactions by palladium
catalyst can be performed to produce 2,6-disubstituted
anilines. A modifed procedure was used to functionalize
these anilines with a hydroxyl group in their para position
(Scheme 1). In this method, anilines were functionalized by
Heck reaction with methyl acrylate in the presence of sup-
ported recoverable palladium catalyst. α-Diimine were syn-
thesized by condensation reaction of the functionalized ani-
lines with acenaphthenequinone in presence of para-toluene
sulfonic acid as a catalyst. the α-diimine nickel (II) catalysts
Scheme 1 Ligands synthesis procedure
1 3

Simple and Strong Dative Attachment of α‑Diimine Nickel (II) Catalysts on Supports for Ethylene…
Scheme 2 Synthetic route of α-diimine precatalyst
with hydroxy functionality were synthesized in two steps: in
the frst step, α-diimine ligands were synthesized by reaction
of 2,6-disubstituted anilines (a–d) and acenaphthenequinone
and in the second step, the produced α-diimines ligands were
reacted with(NiBr2(DME)) in dichloromethane (Scheme 2).
3.2 Heterogenization of α‑Diimine Nickel (II)
Complexes on Spherical MgCl2 Support
These supported catalysts were prepared by reaction of
hydroxyl functionality of α-diimine Ni(II) complexes with
spherical MgCl2 particles without any linker α-diimine
Ni(II) catalysts was dissolved in CH2Cl2 to make a clear
Fig. 2 Proposed complexes of
MgCl2 and α-diimine nickel (II)
catalysts
1 3

E. Kianfar et al.
Table 1 Elemental analysis of spherical MgCl2 supported α-diimine
content in supported catalysts was determined by elemental
analysis and reported in Table 1.
nickel (II) catalysts
Catalyst type
Mga
Clb
Loaded Nia
Ethanolc
3.3 Slurry Phase Ethylene Polymerization
a
b
c
d
d′
16.4
16.1
15.8
14.9
n.d
48.8
47.8
45.5
43.8
n.d
0.89
0.92
0.85
0.78
2.23
22.2
20.3
19.8
19.5
n.d
The slurry phase ethylene polymerizations were carried
out in a one-litter stainless steel Buchi reactor in 750 mL
dried hexane. Polymerization of ethylene using unsupported
and supported catalysts were carried out in the same condi-
tion to compare their performances. The ethyl aluminum
sesquichloride was used as an efcient co-catalyst and the
selected Al/Ni mole ratio was equal to 300. The reaction
time was one hour and the polymerizations were carried out
in 45 °C controlled by a high fow rate circulator. To obtain
polymer particles with better morphology, the perpolym-
erization step was carried out in a mild reaction condition
before the main polymerization step. The prepolymerization
was performed in 10 °C temperature reaction and ethylene
partial pressure of 0.2 bar. A mass fow controller measured
and controlled the fow rate of ethylene to the prepolymeri-
zation reaction. The weight ratio of polymer to the supported
aDetermined by atomic absorption
bDetermined by titration
cDetermined by GC
solution. Then thermally treated spherical MgCl2 was dis-
persed in the solution and mixed gently every 15 min. the
solution color gradually disappeared. The slurry was fltered
and spherical catalyst was dried in vacuum at room tempera-
ture. The attachment of α-diimine Ni(II) catalyst on MgCl2
surface via hydroxyl functionality is shown in Fig. 2. The Ni
Table 2 Ethylene
Run
Catalyst
Activitya
Temp (°C)
Yieldb
Mw×10c3 c
PDId
Tm (°C)
polymerization results with
homogeneous, MgCl2/SiO2
bisupported and spherical
MgCl2 supported α-diimine
nickel (II) catalysts
1
2
3
4
5
6
7
8
a
b
c
d
12,600
17,440
25,040
30,080
13,000
11,120
18,800
21,120
14,200
12,480
24,760
25,680
20,800
15,120
8450
22,600
9320
16,000
18,600
35,080
23,360
45
45
45
45
45
45
45
45
45
45
45
45
45
30
60
30
60
30
60
30
60
29.0
43.6
62.6
75.2
32.5
27.8
47.0
52.8
35.5
31.2
61.9
64.2
52.0
37.8
16.9
56.5
23.3
40.0
46.5
87.7
58.4
52.0
247.5
1093
3700
175.8
384.6
3680
4200
146
517.6
1246
3952
2779
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
1.69
2.85
2.72
2.74
5.78
6.23
7.02
7.52
7.23
6.38
8.30
7.04
7.5
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
128
116
127
126.5
128
127
127.5
128
129
128
128
129
129
128
110
128.5
74.8
128
127.5
129
a/Si-Mg
b/Si-Mg
c/Si-Mg
d/Si-Mg
a/S-Mg
b/S-Mg
c/S-Mg
9
10
11
12
13
14
15
16
17
18
19
20
21
d/S-Mg
d/S-Mg*
a
a
b
b
c
c
d
d
128
Polymerization conditions: homogenous and heterogeneous catalyst 2.5 μmol, cocatalyst: EASC (Al/
Ni=300), nickel loaded in supported catalyst:<1 wt% and*: 2.23 wt% in Run 13, solvent hexane, ethylene
pressure 10 bars, time 60 min
aActivity in kg PE/(mol Ni×h)
bYield in gram
cMolecular weight in g/mol
dPolydispersity index (Mw/Mn), Run 5–8 [26]
1 3

Simple and Strong Dative Attachment of α‑Diimine Nickel (II) Catalysts on Supports for Ethylene…
catalyst was about 6. The prepolymerized catalyst was dried
and diluted in dried hexane. The amount of injected prepo-
lymerized catalyst to the reactor was determined based on
concentration of Ni in reactor. Polymerization of ethylene
using homogeneous, SiO2/MgCl2 bisupported and spherical
MgCl2 supported α-diimine nickel (II) catalysts were per-
formed. The results of polymerizations are shown in Table 2.
The results showed that, synthesized α-diimine nickel (II)
catalysts by tert-butyl phenyl substitutes in ortho positions
of aryl ring have the highest activity among other catalysts.
The data show that the activity of homogenous catalysts sig-
nifcantly depends on the polymerization temperature. The
stability of active centers is decreased in higher tempera-
ture and this phenomenon is signifcant for homogeneous
α-diimine nickel (II) catalysts with ligands bearing lower
steric hindrance. The catalyst activity is decreased when
homogeneous catalysts are supported. Exceptional results in
Table 2 (run 5 and 9) show that supporting of catalyst a with
methyl substituents in their ortho-aryl positions increases
thermal stability of active centers. This thermal stability
leads to increased insertion and decreased β-hydride elimi-
nation reactions. Reduction in activity is signifcant when
SiO2/MgCl2 bisupport is used, but the activity reduction
for spherical MgCl2 supported α-diimine nickel catalysts is
lower. In supported catalysts, the α-diimine nickel (II) com-
plexes with hydroxyl functionality are strongly attached to
the magnesium atoms of SiO2/MgCl2 and spherical MgCl2
surface. These supported catalysts exhibit high activity
and are desirable for ethylene polymerization in industrial
processes. Polyispersity index (PDI) of produced polyeth-
ylene with homogenous catalyst is about 3, but the support-
ing of these catalysts increased PDI of the produced poly-
mers in the same polymerization condition. On the other
hand, molecular weight of produced polymer by the sup-
ported catalyst is higher than homogeneous catalysts. It can
be explained by reduced chain termination and increased
chain propagation rate of active centers in supported cata-
lysts. Immobilization of α-diimine catalysts on the surface
of support reduces the space around the active metal cent-
ers and as reported by Rieger and Gibson et al. [33, 34] it
might decrease chain transfer rates. Increase in molecular
weight of produced polymer by spherical MgCl2 supported
catalysts is larger than the polymer produced by SiO2/MgCl2
bisupported catalysts. It can be related to the acidic nature
of MgCl2 support and the electronical efect on the chain
propagation rate of active centers. Ethylene polymerization
using d onto spherical MgCl2 were carried out in diferent
temperature (Table 3). The results show that, the activity
of this supported catalyst increases when the reaction tem-
perature is increased from 45 to 60 °C. More increase in
reaction temperature has inverse efect on activity due to
instability of active centers in α-diimine complexes at high
temperature. The molecular weight of produced polymer by
homogeneous and supported catalyst was increased using
Table 4 Efect of hydrogen partial pressure on molecular weight of
produced polymer by d/S-Mg
Run
H2 (bar)
Yielda
Activityb
Mw×103 c
PDId
1
2
3
4
5
0
72
70
67.5
67
66.7
28,800
28,000
27,000
26,800
26,680
3260
2220
765.2
553
11.5
10.8
11.3
9.2
0.5
1.0
2.0
3.0
360
8.7
Polymerization conditions: heterogeneous catalyst 2.5 μmol, cocata-
lyst: EASC (Al/Ni=300), nickel loaded in supported catalyst:<1
wt%, solvent hexane, ethylene pressure 10 bars, time 60 min, temp:
60 °C
aYield in gram
bActivity in kg PE/(mol Ni×h)
cMolecular weight in g/mol
dPolydispersity index (Mw/Mn)
Table 3 Efect of temperature
on performance of Spherical
MgCl2 supported α-diimine
nickel (II) catalysts
Run
Catalyst
Temp (°C)
Yielda
Activityb
Mw×103c
PDId
1
2
3
4
5
6
7
a/S-Mg
a/S-Mg
b/S-Mg
b/S-Mg
d/S-Mg
d/S-Mg
d/S-Mg
30
60
30
60
30
60
80
31.5
22.6
23.5
29.3
48.7
72.0
35.5
12,600
10,720
9400
11,720
19,480
28,800
14,200
201
84
662
370
n.d
3260
860.8
7.0
8.3
6.2
7.4
n.d
7.5
6.8
Polymerization conditions: heterogeneous catalyst 2.5 μmol, cocatalyst: EASC (Al/Ni=300), nickel loaded
in supported catalyst:<1 wt%, solvent hexane, ethylene pressure 10 bars, time 60 min
aYield in gram
bActivity in kg PE/(mol Ni×h)
cMolecular weight in g/mol
dPolydispersity index (Mw/Mn)
1 3

E. Kianfar et al.
Fig. 3 SEM image of a bisupported catalyst d/Si-Mg, b produced
polymer by bisupported catalyst d/Si-Mg in 45 °C, c Cross section a
particle shown in b with 2000-fold magnifcation, d spherical MgCl2
support, e heat treated Spherical MgCl2 support, f produced polymer
by d/s-Mg supported catalyst onto spherical MgCl2
more bulky ligands. It seems that, bulkier ligands increase
chain propagation or reduced chain termination rates [2].
Homogeneous and supported catalyst, d which carries bulky
2,6-di(4-tert-butyl phenyl) aryl has shown good activity
to produce polyethylene with high molecular weight. In
Table 4, the hydrogen response of supported d onto spheri-
cal MgCl2 was shown. The molecular weight of polymers
was decreased by increasing the partial pressure of hydrogen
without any sharp decrease in catalyst activity.
particles. Strongly attachment of α-diimine nickel (II) com-
plexes onto the MgCl2 support led to free-fowing polymer
particles and the reactor fouling was not observed during
ethylene polymerization.
4 Conclusion
α-Diimine nickel (II) complexes were synthesized using
different anilines with methyl, isopropyl, phenyl and
tert-butyl phenyl substitutes in their ortho positions and
hydroxyl functionality in their para position. These com-
plexes were supported on SiO2/MgCl2 bisupport and
thermally treated spherical MgCl2 support. Supporting of
homogeneous α-diimine nickel (II) complexes reduced the
catalyst activity. The reduction in activity for bisupported
catalyst was signifcant but it was low or negligible when
spherical MgCl2 was used as catalyst support. The sup-
ported α-diimine complex on spherical MgCl2 that was
prepared from aniline with tert-butyl phenyl substitutes
showed the highest activity among the examined cata-
lysts. According to the results, this catalyst is desirable
for industrial ethylene polymerization processes and has a
good hydrogen response for controlling molecular weight.
The produced polymer by this supported catalyst had high
molecular weight and melting point temperature. The SEM
micrographs show that the morphology of spherical MgCl2
3.4 Catalyst and Polymer Particle Morphology
The SEM images in Fig. 3 show an irregular shape of poly-
mer particles with low bulk density using catalysts SiO2/
MgCl2 and spherical MgCl2 supported catalysts surface and
regular shape and their related produced polymer particles. It
is shown that polymer morphology is not sufcient for poly-
mer processing and it has motivated researchers to attach
these catalysts specially SiO2/MgCl2 and spherical MgCl2
supported catalysts and their related produced polymer par-
ticles by covalent bonds onto supports to produce polymer
particles with desirable morphology. The SEM images of
the polymers showed regular morphology and agglomera-
tion of the polymers on reactor wall and agitator. The SEM
micrographs show that the morphology of spherical MgCl2
supported catalyst was replicated into the fnal polymer
1 3

Simple and Strong Dative Attachment of α‑Diimine Nickel (II) Catalysts on Supports for Ethylene…
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particles. Strongly attachment of α-diimine nickel (II)
complexes onto the MgCl2 support led to free-fowing
polymer particles and the reactor fouling was not observed
during ethylene polymerization.
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