Heterogeneous complexes of nickel MCM-41 with β-diimine ligands: Applications in olefin oligomerization

Article abstract of DOI:10.1016/j.jcat.2014.12.026

The β-diimine ligands 2-(phenyl)amine-4-(phenyl)imine-2-pentene and 2-(2,6-dimethylphenyl)amine-4-(2,6-dimethylphenyl)imine-2-pentene were combined with the alkoxysilane group chloropropyltrimethoxysilane (CPTMS) and covalently anchored to a mesoporous MCM-41 support; they were ordered via interactions with the silanols of the silica matrix and complexed with nickel. The complexes were synthesized for use in ethylene and propylene oligomerization and for comparing the results of homogeneous and heterogeneous systems. The support was first synthesized, calcined, anchored to the ligand, and then, complexed with nickel. These materials were characterized using various techniques, such as ¹H, ¹³C, and ²⁹Si NMR, small angle XRD, thermogravimetric analysis, adsorption isotherms, transmission electron microscopy, and flame atomic absorption spectroscopy, to confirm the success of the synthesis. Both homogeneous and heterogeneous complexes are active and selective for the reactions of ethylene and propylene oligomerization.

Full text of DOI:10.1016/j.jcat.2014.12.026

Journal of Catalysis 323 (2015) 45–54
Contents lists available at ScienceDirect
Journal of Catalysis
journal homepage: www.elsevier.com/locate/jcat
Heterogeneous complexes of nickel MCM-41 with b-diimine ligands:
Applications in olefin oligomerization
Enéderson Rossetto a, Bruna Pes Nicola b, Roberto Fernando de Souza b,1, Katia Bernardo-Gusmão b,
Sibele B.C. Pergher a,
⇑
a LABPEMOL, Institute of Chemistry, Universidade Federal do Rio Grande do Norte-UFRN, Campus universitário, Lagoa Nova, 59078-970 Natal, RN, Brazil
b Institute of Chemistry, Universidade Federal do Rio Grande do Sul-UFRGS, Av. Bento Gonçalves, 9500, P.O. BOX 15003, 91501-970 Porto Alegre, RS, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
The b-diimine ligands 2-(phenyl)amine-4-(phenyl)imine-2-pentene and 2-(2,6-dimethylphenyl)amine-
4-(2,6-dimethylphenyl)imine-2-pentene were combined with the alkoxysilane group chloropropyltrime-
thoxysilane (CPTMS) and covalently anchored to a mesoporous MCM-41 support; they were ordered via
interactions with the silanols of the silica matrix and complexed with nickel. The complexes were syn-
thesized for use in ethylene and propylene oligomerization and for comparing the results of homoge-
neous and heterogeneous systems. The support was first synthesized, calcined, anchored to the ligand,
and then, complexed with nickel. These materials were characterized using various techniques, such as
1H, 13C, and 29Si NMR, small angle XRD, thermogravimetric analysis, adsorption isotherms, transmission
electron microscopy, and flame atomic absorption spectroscopy, to confirm the success of the synthesis.
Both homogeneous and heterogeneous complexes are active and selective for the reactions of ethylene
and propylene oligomerization.
Received 17 September 2014
Revised 21 December 2014
Accepted 22 December 2014
Keywords:
Oligomerization
MCM-41
b-diimine
Nickel complex
Ó 2014 Elsevier Inc. All rights reserved.
1. Introduction
ganic supports (SiO2 or Al2O3), a decrease in activity occurred in
some cases, and increases in selectivity and catalyst stability were
The development of materials and methods for catalytic oligo-
merization of light olefins to give alpha-olefins, such as 1-butene
and 1-hexene, is an important topic in the chemical industry [1].
In the current climate and for the environmental vision of the
world, developing systems that are more efficient, economically
viable, and less harmful to the environment is very important. In
this context, heterogeneous systems and anchoring of homoge-
neous catalytic complexes on supports, such as alumina and silica
[2], are very promising methods for reducing the use of organic sol-
vents in the easy separation of the reaction medium, thus reducing
the costs and environmental impact [3].
The most important heterogeneous catalysts use nickel for eth-
ylene oligomerization and are based on inorganic porous materials.
The major methods for the preparation of heterogeneous nickel
catalysts for oligomerization include NiO or NiSO4 on various inor-
ganic supports, Ni-exchanged zeolites, mesoporous materials
(MCM-41, Al-MCM-41), sulfated alumina, and silica–alumina [4–
7]. However, when nickel complexes were heterogenized on inor-
often observed in ethylene oligomerization reactions [8–10].
Nickel complexes are most commonly used for oligomerization
reactions in homogeneous media because of their high activity and
ability to form specific products. Therefore, they are highly suc-
cessful both from an academic standpoint and in the industry,
resulting in their use in various industrial processes [11–13]. The
commercial oligomerization of ethylene is predominantly per-
formed using transition metal catalysts that produce a wide distri-
bution of linear alpha-olefins, which are used in polymerization
and the preparation of a variety of economically important com-
pounds, such as detergents, synthetic lubricants, plasticizers, and
alcohols [1]. Propylene has been less well studied than ethylene
as an active and selective catalyst for a-olefins; there are also prob-
lems with it regarding its dimer requirements and in obtaining
products with the desired regioselectivity [14].
Highly active nickel complexes with diimine ligands for ethyl-
ene oligomerization or polymerization were introduced by Brook-
hart et al. [15–18]. After that, significant effort was put toward
studying the effects of the structures of the ligands on the catalytic
properties of the metal complexes involved in the oligo/polymeri-
zation [19–22]. b-diimines and b-diiminatos have been studied as
ligands for transition metal compounds [23,24]. Some ligands, such
⇑
Corresponding author.
E-mail address: sibelepergher@gmail.com (S.B.C. Pergher).
In memoriam.
1
http://dx.doi.org/10.1016/j.jcat.2014.12.026
0021-9517/Ó 2014 Elsevier Inc. All rights reserved.

46
E. Rossetto et al. / Journal of Catalysis 323 (2015) 45–54
as b-diimines, are easy to prepare and have several attractive pro-
prieties, including tunable electronic and steric parameters [22]. In
the case of b-diimine ligands, the presence of acidic protons in the
from Vetec and used without further purification. Ethylaluminum
sesquichloride (Al2Et3Cl3, EASC) was supplied by Akzo Nobel and
used with toluene dilution (10%). The solids were dried under
reduced pressure.
a
position facilitates their anchoring via covalent bonding to the
inorganic supports.
Homogeneous catalysts usually contain uniform and well-
defined active sites, which lead to high activities and reproducible
selectivities. However, the major drawback of using these catalysts
is the difficulty in separating the catalysts, products, and solvent.
An alternative to circumvent this drawback is to immobilize the
homogeneous catalyst in various media, including inorganic and
organic supports [25–28].
2.1. Characterization techniques
Elemental analyses were performed using a Perkin Elmer M
CHN Analyzer 2400. The liquid 13C NMR analyses were performed
using a Varian Inova 400 MHz solubilized in deuterated chloroform
(CDCl3). The 13C and 29Si CP-MAS-NMR analyses were performed
using an Agilent 500 MHz spectrometer model DD2 operated at
125.7 MHz for 13C and 99.3 MHz for 29Si using adamantine as a ref-
erence material for peak assignments. The solid NMR conditions
are an acquisition time of 7 ms and a delay of 10 s with a rotation
of 10 kHz to 13C and an acquisition time of 9 ms and a delay of 5 s
with a rotation of 5 kHz to 29Si. Thermogravimetric analyses were
performed on a TA Instrument TGA Q50. The samples were heated
at 10 °C/min from 20 °C to 800 °C under nitrogen flow. The mor-
phology and particle size of the products were investigated using
an EVO50, Carl Zeiss scanning electron microscope (SEM) operating
at 30 kV. For the TEM analysis, a JEOL JEM 2010 transmission
model was used with an acceleration voltage of 200 kV. After sam-
ple pretreatment for 12 h at 90 °C, the specific surface areas of the
samples were determined via nitrogen adsorption–desorption
using a Micrometrics TriStar II 3020. X-ray diffraction analyses
In the1990s, a new family of porous materials, which present a
system of well-defined mesopore sizes with a regular spatial
arrangement, was discovered by scientists at Mobil [29]. This fam-
ily is called M41S and is composed of three types of phases; one of
this materials was called MCM-41. Mesoporous materials of the
MCM-41 type are very interesting because they have ordered
arrays of uniform channels, a high surface area, thermal and chem-
ical stability, and shape selectivity. These materials have a large
number of hydroxyl groups, which provide the necessary qualities
for modification of the internal and external surfaces, and the pos-
sibility of the self-assembly of molecules; these properties provide
excellent chemical aggregation via covalent complexation with
homogeneous media [30]. The synthesis of mesoporous materials
modified with reactive functional groups, such as amines, alde-
hydes, nitriles, phenyls, thiols [31,32], modifying organic groups
(functional ligands), or organometallic complexes with silanol
groups (CPTMS and CPTES), for anchoring via covalent bonding,
has been well studied with promising results observed in the last
decade [3,30]. These systems allow anchoring via covalent bonding
between the silanol groups of the organic functional groups and
the Si–OH groups of the mesoporous materials or between the
functional groups of the modified mesoporous materials and
organic groups of interest.
There are studies that use homogeneous nickel complexes of b-
diimines for oligomerization of olefins [8,33–36]; however, there
are no reports of studies using anchoring via covalent bonds
between nickel complexes, b-diimines, and ordered mesoporous
materials for the oligomerization of ethylene and propylene.
The objective of this study was to investigate the potential for
developing new nickel complexes heterogenized on mesoporous
materials via anchoring with covalent bonds between the MCM-
41 mesoporous support and nickel complexes with b-diimine
ligands, attempting to produce catalyst complexes that are active
and selective for the oligomerization of olefins (ethylene and
propylene).
were performed on a Bruker D2 Phaser using Cu K
a radiation
(k = 1.54 Å) in the range 2h = 1°–8° using slits of 0.1 and 3 nm.
The nickel content of the solids was determined via flame atomic
absorption spectrometry (FAAS). The analysis was performed using
a Perkin Elmer A atomic absorption spectrometer with a hollow
nickel cathode lamp (k = 232 nm) and air–acetylene flame (10 L/
min: 2.5 L/min). The samples were prepared by treating 50 mg of
the heterogeneous complex with 2 mL of HCl, 6 mL of HNO3, and
5 mL of HF, adding the mixture to Teflon autoclaves and, subse-
quently, using a digester for 24 h at 150 °C. After cooling, the sam-
ples were diluted to 50 mL.
2.2. Synthesis of L1 and L2 ligands and homogeneous C1 and C2 nickel
complexes
The syntheses and characterization of ligands L1 = 2-(phenyl)a-
mine-4-(phenyl)imine-2-pentene
phenyl)amine-4-(2,6-dimethylphenyl)imine-2-pentene and their
corresponding nickel complexes C1 = dibromo(N,N-bis(phenyl)-
2,4-pentanediimine)nickel(II)
dimethylphenyl)-2,4-pentanediimine)nickel(II) were described in
a previous work [8].
and
L2 = 2-(2,6-dimethyl-
and
C2 = dibromo(N,N-bis(2,4-
2. Experimental section
2.3. Synthesis of MCM-41
All experiments were performed under an argon atmosphere
using standard Schlenk techniques. The solvents were deoxygen-
ated by refluxing over appropriate drying agents (toluene and ethyl
ether on sodium benzophenone and dichloromethane and acetoni-
trile on phosphorous pentoxide) under argon and distilled immedi-
ately prior to use. Methanol and tetrahydrofuran (THF) were used
without further purification. Aniline, 2,6-dimethylaniline, and hex-
adecyltrimethylammonium bromide (CTABr) were purchased from
Sigma–Aldrich and distilled under reduced pressure prior to use. 3-
chloropropyltrimethoxysilane (CPTMS), sodium aluminate, sodium
hydroxide, tetramethyl ammonium hydroxide (TMAOH), sodium
hydride (NaH), and anhydrous nickel bromide (NiBr2) were pur-
chased from Sigma–Aldrich. Silica Aerosil 200 was purchased from
Degussa. p-Toluenesulfonic acid (Vetec) was distilled on toluene
using the Dean–Stark technique. Sodium carbonate was purchased
The syntheses of mesoporous MCM-41 materials were based on
the synthesis described by Corma et al. [36]. The synthesized mate-
rial has the following molar ratio:
TMAOH:20 H2O.
1 SiO2:0.1 CTABr:0.25
Solution A was added to a plastic beaker under heating at 40 °C
and mechanical agitation with 134 g of distilled water and 20 g of
CTABr. The solution was stirred for 1 h.
Solution B: In a plastic beaker, 34.6 g of TMAOH 25% and 3.84 g
of aerosil silica were added and left under magnetic stirring for
45 min to homogenize the sample.
Subsequently, solution B was added to solution A under
mechanical stirring and slowly added to 18.08 g of aerosil silica.
The gel formed was left under stirring for 1 h to homogenize the
sample (pH = 13). The resulting gel was transferred to 4 stainless
steel autoclaves with Teflon slings and placed in a static oven at

E. Rossetto et al. / Journal of Catalysis 323 (2015) 45–54
47
135 °C for 24 h. The resulting material was filtered with distilled
water and then dried at 100 °C for 4 h. Subsequently, the material
was calcined at 550 °C for 6 h under nitrogen and synthetic air
yielding 15.36 g of calcined MCM-41.
inert atmosphere at a temperature of 35 °C. The solvent was
removed under reduced pressure.
2.4.2. Synthesis of silylated organic precursor
A solution of 1.1 mL (6 mmol) of CPTMS in 5 mL of toluene
(THF) (1:1) was added to sodium salt under an argon atmosphere.
The mixture was stirred and refluxed at 80 °C for 3 h. The resulting
solution was centrifuged to separate the produced NaCl, the excess
NaH, and the supernatant containing the organic ligand precursor,
which is used in the synthesis of the hybrid xerogel. Step 2 in Fig. 1
shows the synthesis reaction of the organic precursor.
2.4. Synthesis of the hybrid mesoporous materials
The hybrid mesoporous materials were synthesized based on
previously published methods [8]. This method requires the
completion of four successive steps:
1. Activation of ligand
2.4.3. Anchoring of the L1 and L2 ligands
2. Synthesis of organic precursor
3. Anchoring of the organic precursor
4. Complexation of nickel
In this method, the mesoporous supports are first synthesized
and calcined at 540 °C for 6 h under airflow. The support of
MCM-41 was calcined and pre-treated at 100 °C for 6 h under high
vacuum. This procedure was used to remove residual moisture
from the support. This step was performed after the synthesis of
the silylated organic precursor using the ligand in a reaction with
NaH followed by reaction with CPTMS. The silylated organic pre-
cursor coupled with the support was combined with toluene and
left for 24 h at 80 °C under reflux, as shown in step 3 of Fig. 1.
2.4.1. Activation of the ligand: synthesis of the sodium salt
The ligand (6 mmol) was activated with sodium hydride NaH
(9 mmol) using dichloromethane (20 mL) as the solvent, as is
shown in step 1 in Fig. 1. This reaction was monitored by the liber-
ation of H2. The mixture was left under stirring for 30 min under an
Fig. 1. Anchoring via covalent attachment of L1 and L2 in MCM-41 and obtaining the heterogeneous complexes HC1 and HC2.

48
E. Rossetto et al. / Journal of Catalysis 323 (2015) 45–54
The solid phase was filtered and washed with dichloromethane to
remove the un-anchored ligands and then dried under vacuum. All
procedures were performed under an argon atmosphere.
Petrocol DH capillary column (methyl silicone, 100 m in length,
0.25 mm ID, 0.5 m film thickness). The analysis conditions for
l
ethylene were 36 °C for 15 min, followed by heating at a rate of
5 °C/min to 250 °C. For propylene, the analysis conditions were
36 °C for 30 min, followed by heating at a rate of 5 °C/min to
250 °C. The products were identified using the method of co-injec-
tion of standards, and isooctane was used as the internal standard
for quantification. The TOF values, defined as moles of converted
ethylene per mole of pre-catalyst per reaction time (in h), show a
variation of 10%, as determined by at least three independent
experiments performed under each condition.
2.4.4. Complexation of nickel
2.4.4.1. Synthesis of the Ni(CH3CN)2Br2 adduct. The synthesis of the
adduct was performed according to Hathaway et al. [37]. In a
Schlenk flask, 4.981 g (22.8 mmol) of NiBr2 was added to 240 mL
of acetonitrile. The reaction mixture was left under stirring and
refluxing conditions for 4 h at 80 °C, forming a blue oil solution.
The mixture was concentrated to 20 mL. A light yellow solid was
obtained, which was filtered, washed with acetonitrile, and dried
under argon flow. The mass of the product was 6.012 g, with a yield
of 87.9%. Ni(CH3CN)2Br2 adduct was used in the synthesis of the
diimine nickel complexes.
3. Results and discussion
The ability of these complexes to anchor via covalent bonding
with the silanol matrix silica allows for the transformation of a
homogeneous system to a heterogeneous system, realizing many
advantages by combining two different materials, for example,
easy separation from the reaction medium and the ability to reuse
and recycle the complex.
The anchoring of complexes C1 and C2 was developed at differ-
ent stages via functionalization of the ligand and its interaction
with the silanol support, as demonstrated in Fig. 1, and the com-
plexes were characterized using various analytical techniques to
confirm the success of the synthesis and evaluate the characteris-
tics of the materials. Fig. 2 shows the XRD patterns of the calcined
MCM-41 after anchoring of the ligands HL1 and HL2 and after
metal complexation of HC1 and HC2. In the diffractogram of the
calcined sample, the presence of three reflections can be observed
(Miller indices (100), (110), and (200)) in the region of 2h = 2°–8°.
The characteristics of the MCM-41 mesoporous materials are a typ-
ical hexagonal structure and a good ordering of the mesopores,
2.4.4.2. Complexation of nickel. These complexes are used as cata-
lyst precursors for the oligomerization reactions of ethylene and
propylene in heterogeneous media. In a Schlenk flask, 1.2 equiva-
lents of Ni(CH3CN)2Br2 were added with respect to the amount of
ligand calculated via elemental analysis of CHN, and 20 mL of
dichloromethane was then added to the hybrid materials HL1
and HL2, as shown in step 4 of Fig. 1. This suspension remained
under agitation for 5 days at room temperature. Upon completion
of the synthesis, the suspension was filtered using a Schlenk filter
and washed with acetonitrile until the solvent was clear (approxi-
mately four 30-mL aliquots). The HC1 and HC2 solids obtained
were dried under reduced pressure and submitted for analysis
using FAAS.
2.5. Ethylene oligomerization runs
The reactions were performed in homogeneous and heteroge-
neous phases, and the results were compared.
The oligomerization reaction experiments were performed in a
450-mL Parr stainless steel autoclave equipped with a magneti-
cally driven mechanical stirrer, a thermocouple, and a pressure
gauge. The reaction temperature (10 °C) was controlled using a
thermostatic bath.
In a typical homogeneous or heterogeneous reaction run, a solu-
tion of EASC and 60 mL of toluene was added to the reactor under
argon, followed by the addition of 20 lmol or 13 lmol of the cat-
alytic precursor. The reactor was pressurized with ethylene or pro-
pylene, and the temperature was adjusted to 10 °C using
thermostatic bath circulation. The Al/Ni molar ratios varied from
100 to 200, and the ethylene or propylene pressure was 15 atm
and 5 atm, respectively. After 30 min, the reaction was stopped,
and the mixture was cooled to ꢀ30 °C for ethylene and 10 °C for
propylene and analyzed immediately using gas chromatography.
Recycle experiments were performed in a 100-mL double-
walled glass reactor containing a magnetic stirring bar with a con-
stant supply of neat gaseous propylene at 6 atm and a thermocou-
ple to measure the temperature. The reaction temperature was
held at 10 °C using an external-circulation ethanol bath. In a typi-
cal experiment, the reactor was charged with a solution of the
desired catalytic precursor (13 lmol) in 60 mL of toluene saturated
with propylene. The reactor was purged with propylene, and the
alkylaluminum solution was added in the amount needed to obtain
an aluminum to nickel molar ratio (Al/Ni) of 200. After 30 min, the
reaction was stopped, and the mixture was cooled and analyzed
using gas chromatography. After the first reaction, the products
were removed from the reactor through a cannula. The catalyst
recycling was accomplished by adding another 50 mL of toluene
and 4.6 mL of EASC and continuing the reaction.
In all cases, the chromatographic analyses were performed
using a Shimadzu GC-2010 gas chromatograph equipped with a
Fig. 2. XRD pattern of (A) calcined MCM-41, HL1 and HL2, and (B) HC1 and HC2.

E. Rossetto et al. / Journal of Catalysis 323 (2015) 45–54
49
which can be confirmed by analyzing the transmission images
shown in Fig. 7. The diffractogram of the sample after anchoring
of the ligand and nickel complexation shows reflection characteris-
tics of the MCM-41 mesoporous materials, but the reflections
(110) and (200) have a lower intensity, which may be due to
the anchoring of the organic matter and the complexation of the
metal. These characteristics may distort the regular matrix of
MCM-41 or interfere with the X-ray analysis. This small decrease
in intensity is not interpreted to be a severe loss of long-range
ordering in the silica structure [38,39].
N2 adsorption–desorption isotherms of calcined MCM-41 and
the samples after the anchoring of L1 and L2 ligands are shown
in Fig. 3. We can observe a typical type IV isotherm of mesoporous
materials (defined using IUPAC) with a type 1 hysteresis [40]. The
results of the texture analysis from the N2 adsorption–desorption
isotherms are shown in Table 1. Calcined MCM-41 has a BET area
of 1009 m2/g and a mesopore volume of 0.98 cm3/g. The HL1 and
HL2 materials exhibit decreases in the BET area of 691 and
698 m2/g and mesopore volume of 0.60 and 0.58 cm3/g, respec-
tively. The values of the pore sizes of the materials (MCM-41 cal-
cined, 2.71 nm) changed after the anchoring of the L1 (2.48 nm)
and L2 (2.35 nm) ligands. The relative pressure where the pores
of the materials are filled is shifted to lower values for the HL1
and HL2 samples compared to the source material, calcined
MCM-41, resulting in a decrease in the BET surface area, pore vol-
ume, and pore diameter, indicating that the anchored organic mat-
ter (L1 and L2) is within the pores of the MCM-41.
and the pore diameters (Dp) of these materials. The results are
shown in Table 1. After the anchoring of the L1 and L2 ligands,
the pore size decreased and the wall thickness increased, indicat-
ing that the ligands are within the pores of the MCM-41 material
and connected to the walls, which is in agreement with the values
obtained from the adsorption–desorption isotherms.
The solution 13C NMR spectrum of L1 and solid 13C and 29Si
NMR spectra of HL1, which were chosen to represent the results
after the anchoring of the ligands, are shown in Fig. 4. In the solu-
tion 13C NMR spectrum of L1, the signals were assigned (Fig. 4A)
and we can observe that the more intense signals are the aromatic
ones (122, 123, and 128 ppm). After anchoring the ligand L1
(Fig. 4B), we can assign the signal at 7.9 ppm to the carbon
attached to the silicon in MCM-41. The signals at 24.8 and
48.3 ppm are attributed to methyl carbon and carbon bound to
the L1 ligand [30]. The only three signals of the ligand that can
be observed are the aromatics carbons. The aliphatic ones related
to the ligand cannot be observed perfectly due to the high noise
level of the analysis and the excess of fixed propyl from chloropro-
pyltrimethoxysilane. Fig. 4C shows the 29Si NMR analysis of the
calcined MCM-41, and we can observe the NMR signals at
94 ppm assigned to the group Q2 [germinal silanol, (SiO)2Si(OH)2],
Q3 at 101 ppm [single silanol, (SiO)3Si(OH)], and Q4 at 109 ppm
[siloxane, (SiO)4 Si], showing the silica sites of the structure [30].
After the anchoring of the L1 and L2 ligands, the intensity of the
signal from silicon Q2 is reduced considerably (94 ppm), but the
signals for Q3 (101 ppm) and Q4 (109 ppm) increase in intensity,
which is due to the consumption of Si–OH and Si(OH)2; this result
can also be observed in the infrared spectrum because the band
related to the Si–O–Si bond in the HL1 and HL2 samples increases
to 1050 cmꢀ1 compared to the MCM-41 matrix. In the HL1 29Si
NMR sample, the appearance of two resonance signals at 60 ppm
is also observed, which are assigned to the group T2 [C–Si(OSi)2
(OH)], and at 68 ppm, which are assigned to the group T3
[C–Si(OSi)3] [30]. From the results of the 13C and 29Si NMR, we
can say that the L1 and L2 ligands are successfully anchored via
covalent Si–O–C bonds to the MCM-41, and together with the
XRD results and adsorption–desorption isotherms of these materi-
als, we see that they are preferably within the pores of the
Using XRD and gas adsorption analyses, we can calculate the
lattice parameters of the unit cells (a0), the wall thicknesses (Wt),
MCM-41, maintaining
a regular structure with characteristic
hexagonal ordered materials. The heterogenized nickel complexes
HC1 and HC2 were not subjected to 13C and 29Si NMR analysis due
to the paramagnetic metal.
The elemental analysis and flame atomic absorption (FAAS)
data (see Table 1) were used to determine the ligand incorporation
percentage and quantify the organic matter attributed to L1 and L2
anchored to the MCM-41 matrix and to quantify the nickel in HC1
and HC2 (see Table 1). The analysis of the N content reveals that
Fig. 3. Adsorption–desorption isotherms of calcined MCM-41, HL1 and HL2.
Table 1
Structural properties of the synthesized materials.
a
b
c
d
e
Sample
d100
(nm)
a0
ABET
(m2 gꢀ1
Vtotal
Vmeso
Dp
Wtf
(nm)
Ligand
Organic content
mol/g)g
Nickel contenth
(lmol/g)
(nm)
)
(cm3 gꢀ1
0.98
)
(cm3 gꢀ1
0.98
)
(nm)
incorporation (%)g
(
l
MCM-41
3.80
4.39
1009 10
2.71
1.68
0.0
0.0
0.0
Calcined
HL1
HL2
4.07
3.82
4.70
4.41
691 15
698 36
0.60
0.53
0.60
0.53
2.48
2.35
2.22
2.06
17
11
124
175
130 1.87i
159 0.85j
p
a
b
c
a0: lattice parameter in the unit cell = 2d100/ 3.
ABET = specific area obtained using the BET method (total area).
Vtotal = total pore volume obtained for P/P0 = 0.98 using the rule of Gurvich.
d
e
f
Vmeso = pore volume related to the contribution of mesopores obtained using BJH method.
Dp = average pore diameter calculated by intervals obtained using the BJH desorption method.
Wt: Wall thickness = a0–Dp.
g
h
Ligand incorporation and organic content: calculated from the %N obtained from the elemental analysis.
Nickel content of complexes HC1i and HC2j.

50
E. Rossetto et al. / Journal of Catalysis 323 (2015) 45–54
Fig. 4. 13C NMR spectra of, (A) Homogeneous L1, (B) HL1 29Si NMR spectrum of (C) calcined MCM-41, and (D) HL1.
the amount of organic material anchored to the MCM-41 matrix
was 17% and 11% of the 6 mmol added. These correspond to
124 lmol/g (36 mg/g) for HL1 and 175 lmol/g (61 mg/g) for HL2.
which are usually observed in MCM-41 [41]. After anchoring of
the L1 and L2 ligands, no change in the morphology of the material
is observed.
The amount of active sites of heterogeneous complexes HC1 and
HC2 was calculated based on the concentration of nickel
(7.84 mg/g HC1 and 9.34 mg/g HC2) obtained using FAAS. These
quantities correspond to about one nickel for each ligand
Fig. 7 shows transmission electron microscopy (TEM) images. A)
image viewed along the [010] axis, and B) image viewed along the
[100] axis. In the TEM images, mesoporous channels in a hexago-
nal arrangement with good order can be observed.
(130
l
mol/g and 159
l
mol/g).
Homogeneous complexes C1 and C2 and the heterogeneous
complexes HC1 and HC2 were combined with EASC and used as
catalysts for the oligomerization reaction of ethylene and propyl-
ene. The results in homogeneous media, as previously described
[8], were compared with those obtained in heterogeneous media.
All reactions were performed at least in duplicate. Both homoge-
neous complexes and heterogeneous complexes were active in
the oligomerization reaction. The reaction parameters of tempera-
ture (10 °C), Al/Ni ratio, reaction time, and ethylene pressure were
studied in the previously described works [8,42].
The results of the oligomerization of ethylene are shown in
Table 2. Entries 1 and 2 are related to the homogeneous complex.
The C1 complex without substituents on the phenyl ring had a
higher activity (210.0 ꢁ 103 hꢀ1), with selectivity for the C4 fraction
of 78%, which were comparable with the C2 complex with substit-
uents on the phenyl ring, but the C2 complex had greater selectiv-
ity for the C4 fractions (97%). These results suggest that the greater
steric hindrance of the methyl groups decreases the accessibility of
the ethylene and, consequently, reduces the activity of the reac-
tion. This behavior is predominantly related to electronic effects
[8,43].
Thermograms of calcined MCM-41 and the HL1 and HL2
hybrid materials are shown in Fig. 5A. In the calcined MCM-41,
water mass loss occurred at temperatures below 150 °C. For the
L1 and L2 ligands, as shown in Fig. 5B, the decomposition tem-
perature of the organic material occurs between 130 and
270 °C, with a degradation peak at 280 °C. After anchoring in
the silica matrix (HL1 and HL2), the TGA curves show loss of
adsorbed water, structural desidroxilation, methanol loss from
methoxy groups, and residual solvent (toluene) and organic mate-
rial decomposition. The temperature range of the decomposition
increases from 150 to 400 °C with a decomposition peak at
380 °C, indicating that the material is more resistant to tempera-
ture effects, which is attributed to covalent ligand anchoring on
the MCM-41 matrix. From NMR results, elemental analysis and
TGA, it can be argued that the ligands were anchored successfully
at the MCM-41 matrix.
Scanning electron microscopy was performed with the aim of
evaluating the morphology of the materials before and after
anchoring of the ligands, which is shown in Fig. 6. We can observe
the morphology of the particle agglomerates with irregular sizes,

E. Rossetto et al. / Journal of Catalysis 323 (2015) 45–54
51
Entries 3 and 4 are related to reactions in heterogeneous media.
Thirteen mol of the complex, determined based on the amount of
l
nickel incorporated in the material, was used, assuming that all
metal species are active. An Al/Ni ratio of 200 for the reactions in
heterogeneous media was used. The HC1 complex has a greater
activity of 18.1 ꢁ 103 hꢀ1 compared with HC2 (12.7 ꢁ 103 hꢀ1
)
and has the same selectivity for the C4 fraction (97% and 98%,
respectively). However, the selectivity for the
a-C4 fraction by
the HC2 complex (90%) is higher than for the HC1 complex
(76%). This behavior may be related to the greater steric hindrance
of the HC2 complex, which possesses two methyl groups at the
ortho position of the phenyl.
The results from the homogeneous complex entries 1 and 2
were compared with the results of the heterogeneous complex
entries 3 and 4. As described in Table 2, Al/Ni = 200. It is necessary
to use a larger amount of the complex to activate the alkylalumi-
num due to the presence of hydroxyl groups in the MCM-41
matrix, which consumes alkylaluminum [8]. The heterogeneous
complex entries 3 and 4 showed a lower catalytic activity for eth-
ylene oligomerization than the homogeneous analogue inputs 1
and 2, most likely because of the heterogeneous catalysts having
a lower number of active species, which is related to the need to
use a greater amount of alkylaluminum to activate the Ni species
due to the presence of hydroxyls.
Heterogenized complexes exhibited a lower activity for oligo-
merization of ethylene. However, the heterogenized complexes
exhibited the best selectivities for both C4 and a-C4 fractions com-
pared with homogeneous complex C1. Heterogenized complex
HC2 exhibited the same selectivity as the analogous homogenous
complex. MCM-41 serves as a support for the catalysts and acts
as a steric hindrance for the formation of internal olefins.
Fig. 5. Thermogravimetric analysis of (A) calcined MCM-41, HL1 and HL2 materials,
and (B) L1 and L2 ligands.
Fig. 6. Micrographs of (A) calcined MCM-41, (B) HL1 and (C) HL2.
Fig. 7. Transmission electron microscopy of calcined MCM-41. (A) Image viewed along the axis [010] and (B) image viewed along the [100] axis.

52
E. Rossetto et al. / Journal of Catalysis 323 (2015) 45–54
Table 2
The homogeneous complex inputs 1 and 2 (Table 3) were active
for the oligomerization of propylene, resulting in activities of
105 ꢁ 103 hꢀ1 for the C1 complex and 42 ꢁ 103 hꢀ1 to the C2 com-
plex, and presenting low activity for toluene alkylation of 1.6 and
0.9 ꢁ 103 hꢀ1, respectively. A selectivity of 98% was obtained for
the C6 products, and 53% was obtained for linear C6 using complex
C1 and 30% using complex C2.
Results of the ethylene reactions of homogenous and heterogeneous nickel
complexes.
Entry
Complex
Al/Ni
TOF (103 hꢀ1
)
Sc4 (%)
a
-c4 (%)
Sc6 (%)
1
2
3
4
C1
C2
HC1
HC2
100
100
200
200
210.0
18.3
18.1
12.7
78
97
97
98
32
87
76
90
20
3
3
2
The HC1 and HC2 heterogeneous complexes, entries 3 and 4 in
Table 3, showed quite different behavior compared with their
homogeneous analogues, showing greater activity for the alkyl-
ation of toluene: 90 ꢁ 103 hꢀ1 for HC1 and 10 ꢁ 103 hꢀ1 for HC2.
This behavior, which favors the formation of alkylation products
of toluene, is possibly related to the high Lewis acidity [52] of
the species formed by the reaction of acidic groups on the surface
of MCM-41 with the EASC co-catalyst.
Blank tests B1, B2, and B3, entries 7, 8, and 9 in Table 4, were
performed to evaluate this behavior. Input 8 describes the B2 test
using the calcined MCM-41 without the complex and anchored
with the EASC cocatalyst, resulting in an alkylation activity of
5 ꢁ 103 hꢀ1. This result was compared with input 7, test B1, which
only uses the co-catalyst EASC, and has an alkylation activity of
2 ꢁ 103 hꢀ1. Entry 9, which has only the B3 complex, uses the cal-
cined MCM-41 and does not exhibit any catalytic activity. These
behaviors explain the influence of the MCM-41 matrix on the cat-
alytic activity for alkylation: it is more active when the MCM-41
and the EASC co-catalyst are combined, indicating that the
Complex: 20 lmol for homogeneous and 13 lmol for heterogeneous, pressure:
15 atm of ethylene, T = 10 °C, time = 0.5 h, solvent = toluene (60 mL),
cocatalyst = EASC.
The results of the oligomerization of propylene for homoge-
neous and heterogeneous complexes are shown in Table 3. The
same reaction conditions were used as in the oligomerization of
ethylene, but for propylene, the maximum usable pressure is
6 atm. The behavior of the homogeneous and heterogeneous com-
plexes used for the oligomerization of propylene was studied, and
the results were compared for the two systems. All complexes
were active for the oligomerization of propylene. When toluene
was used as the solvent, the reaction product was the alkylation
of toluene with propylene after a reaction called Friedel–Crafts
alkylation [44–51]. The product obtained is considered a parallel
reaction to propylene oligomerization. To avoid this unwanted
product, cyclohexane was tested as the solvent in the reaction.
Table 3
Results of the oligomerization of propylene using the homogenous and heterogeneous nickel complexes.
Entry
Complex
nNi (10ꢀ6 mol)
Al/Ni
FRoliga (103 hꢀ1
)
FRalqb (103 hꢀ1
)
% Products
% C6 lineare
c
c
C6
C9
d
Homogeneous tests
1
2
C1
C2
20
20
100
100
105
42
1.6
0.9
98
98
0
0
1
1
0
0
1
1
53
30
Heterogeneous tests with toluene
3
4
HC1
HC2
13
13
200
200
3
2
90
10
3
32
0
0
42
20
19
9
36
39
13
18
Heterogeneous tests with cyclohexane
5
6
HC1
HC2
13
13
200
200
2
4
0
0
100
100
0
0
0
0
0
0
0
0
29
30
Reaction conditions: time = 30 min, temperature = 10 °C, relations. Al/Ni = 100 and 200, cocatalyst = EASC, and propylene pressure = 6 atm.
a
TOF oligomerization: mol of propylene oligomerized/(mol Ni * hours).
TOF alkylation: mol of converted toluene/ (mol Ni * hours).
Oligomerization products.
Mono-(C10), di-(C13), and tri alkylation (C16) of toluene with propylene.
b
c
d
e
% Calculated taking into account only the products of dimerization C6.
Table 4
Results of the blank tests.
Entry
Complex
nNi (10ꢀ6 mol)
FRoliga (103hꢀ1
)
FRalqb (103hꢀ1
)
% Products
% C6 lineare
c
c
C6
C9
d
7
8
9
B1 (EASC)
B2 (EASC/M-41)
B3 (M-41)
0
0
0
0
0
0
2
5
0
0
0
0
0
0
0
25
43
0
15
15
0
60
41
0
0
0
0
Reaction conditions: time = 30 min, temperature = 10 °C, and propylene pressure = 6 atm.
a
TOF oligomerization: mol of propylene oligomerized/(mol Ni * hours).
TOF alkylation: mol of converted toluene/ (mol Ni * hours).
Oligomerization products.
Mono-(C10), di-(C13), and trialkylation (C16) of toluene with propylene.
b
c
d
e
% Calculated taking into account only the products of dimerization C6.

E. Rossetto et al. / Journal of Catalysis 323 (2015) 45–54
53
Table 5
Distribution of the products of interest (C6) from propylene oligomerization reactions in homogeneous and heterogeneous media.a
Entry
Complex
4M1P
2,3DM1B
c4M2P
t4M2P
2M1P
1H
t3H
t2H
2M2P
c2H
2,3DM2B
1
2
3
4
5
6
C1
C2
HC1
HC2
aHC1
aHC2
1.3
3.1
24.9
16.3
19.1
13.4
5.3
8.2
5.2
7.1
7.1
6.7
35.3
55.8
56.3
50.1
41.7
45.8
4.1
2.9
–
–
2.7
4.2
–
–
–
–
2.2
1.2
4.3
2.5
2.1
2.0
1.3
1.3
15.7
17.3
0.9
14.5
14.2
13.9
28.1
4.9
9.2
4.8
4.3
8.4
–
–
–
–
–
–
4.0
4.9
1.4
5.2
6.5
5.1
1.8
0.4
–
–
0.9
–
a
Reactions performed with cyclohexane solvent. 4M1P (4-methyl-1-pentene), 2,3DM1B (2,3-dimethyl-1-butene), c4M2P (cis-4-methyl-2-penteno), t4M2P (trans-4-
methyl-2-penteno), 2M1P (2-methyl-1-penteno), 1H (1-hexene), t3H (trans-3-hexeno), t2H (trans-2-hexene), 2M2P (2-methyl-2-pentene), c2H (cis-2-hexene), 2,3DM2B
(2,3-dimethyl-2-butene).
Table 6
Distribution of products from alkylation reactions of oligomerization of propylene in homogeneous and heterogeneous media.
Entry
Complex
Selectivities for cymenes
a
Meta-cymene
Para-cymene
Ortho-cymene
1
2
3
4
7
8
C1
C2
HC1
HC2
B1
1
1
42
20
43
33
18.3
16.4
17.4
17.0
16.1
16.5
33.4
35.0
35.2
35.5
32.6
34.1
48.3
48.6
47.5
47.5
51.3
49.5
0
0
19
9
20
15
0
1
36
39
47
41
B2
a
Distribution of products in the range of C10
.
material has a certain acidity that directs the reaction to the
formation of alkylation products.
The heterogeneous complexes HC1 and HC2 also have catalytic
activities for C6 products of 3 ꢁ 103 hꢀ1 and 2 ꢁ 103 hꢀ1 with selec-
tivities of 13% and 18% for C6 linear products, respectively. These
homogeneous complexes are preferentially active for products in
the range of C6, with a small activity for the alkylation of toluene.
The heterogeneous complexes exhibited activity for toluene alkyl-
ation products with a small activity for products in the range of C6.
The blank tests (B1, B2, and B3) showed only products for alkyl-
ation of toluene, with lower activity than the homogeneous and
heterogeneous complexes, indicating the importance of the metal
center for this type of reaction system.
Because the goal was to obtain products in the range of C6, cat-
alytic tests were performed using cyclohexane as a solvent, with no
intention of obtaining alkylation products. We can see that entries
5 and 6, for heterogeneous complexes HC1 and HC2, are active in
the oligomerization of propylene and are selective for products in
the range of C6 (100% C6, 30% linear). The catalytic activities shown
in comparison with systems that use toluene as a solvent are
lower. This observed decrease in activity was attributed to the
lower solubility of propylene when in cyclohexane.
Table 5 shows the products obtained in the range of C6 for the
reaction of propylene oligomerization, both in homogeneous and
in heterogeneous media for the two systems with different sol-
vents. The products are branched in all cases, wherein the product
obtained is c4M2P, showing that the second insertion of propylene
occurs primarily at the two carbons, and the expected values of p
and q were obtained.
Fig. 8. Results of the HC1 catalyst recycle reaction.
Recycle reactions (see Fig. 8) were performed using the heterog-
enized HC1 complex, which was shown to be active in recycle reac-
tions and is, therefore, promising for large-scale use. A decrease in
the reaction activity compared to the first cycle is observed while
remaining practically unchanged until the third cycle.
4. Conclusions
In Table 6, the products of alkylation of toluene are shown.
We observed products in the range of C10, C13, C16, and C10, with
a distribution of products in meta-, para-, and ortho-cymene. All
complexes exhibit almost the same behavior with respect to the
In this work, the oligomerization of ethylene and propylene cat-
alyzed by homogeneous nickel diimine complexes and heteroge-
neous complexes combined with ethyl aluminum sesquichloride
was studied. The influences of the structures of the ligands and
the anchoring of ligands via covalent bonding on the activity and
selectivity of the oligomerization were studied on an ordered
MCM-41 support.
distribution of products in the range of C10. Heterogeneous
complexes have the same behavior compared to each other
and tend to produce more alkylation than their homogeneous
analogues.

54
E. Rossetto et al. / Journal of Catalysis 323 (2015) 45–54
[4] A. Lacarriere, J. Robin, D. Swierczynski, A. Finiels, F. Fajula, F. Luck, V. Hulea,
Heterogeneous compounds were obtained via modification of
ChemSusChem 5 (2012) 1787–1792.
the ligands with chloropropyltrimethoxysilane and anchored via
covalent bonds with the silica matrix via O–Si–O–Si–C connec-
tions, confirmed using solid-state 13C and 29Si NMR and infrared
spectroscopy. The XRD patterns confirmed that the structure of
MCM-41 remained in an ordered hexagonal form with a small
reduction of the (110) and (200) reflections after the anchoring
of the ligands. A decrease in the values of the area calculated using
the BET method and a reduction in the pore volume after anchoring
of the ligand in the material were observed via N2 adsorption–
desorption analysis, indicating that the organic material is prefer-
ably anchored within the pores of the MCM-41.
[5] M. Lallemand, A. Finiels, F. Fajula, V. Hulea, J. Phys. Chem. C 113 (2009) 20360–
20364.
[6] A. Finiels, F. Fajula, V. Hulea, Catal. Sci. Technol. 4 (2014) 2412–2426.
[7] V. Hulea, F. Fajula, J. Catal. 225 (2004) 213–222.
[8] E. Rossetto, M. Caovilla, D. Thiele, R.F. de Souza, K.B. Gusmão, Appl. Catal. A:
Gen. 454 (2013) 152–159.
[9] M.O. de Souza, R.F. de Souza, L.R. Rodrigues, H.O. Pastore, R.M. Gauvin, J.M. R
Gallo, C. Favero, Catal. Commun. 32 (2013) 32–35.
[10] M.L. Mignoni, M.O. de Souza, S.B.C. Pergher, R.F. de Souza, K.B. Gusmão, Appl.
Catal. A: Gen. 374 (2010) 26–30.
[11] V.C. Gibson, S.K. Spitzmesser, Chem. Rev. 103 (2003) 283–315.
[12] A. Kermagoret, P. Braunstein, Dalton Trans. (2008) 822–831
[13] G.P. Belov, P.E. Matkovsky, Petrol. Chem. 50 (2010) 283–289.
[14] M.O. De Souza, R.F. de Souza, L.R. Rodrigues, H.O. Pastore, R.M. Gauvin, J.M.R.
Gallo, C. Favero, Catal. Commun. 32 (2013) 32–35.
[15] L.K. Johnson, C.M. Killian, M. Brookhart, J. Am. Chem. Soc. 117 (1995) 6414–
6415.
[16] C.M. Killian, D.J. Tempel, L.K. Johnson, M. Brookhart, J. Am. Chem. Soc. 118
(1996) 11664–11665.
[17] D.P. Gates, S.A. Svejda, E. Onate, C.M. Killian, L.K. Johnson, P.S. White, M.
Brookhart, Macromolecules 33 (2000) 2320–2334.
[18] S.A. Svejda, L.K. Johnson, M. Brookhart, J. Am. Chem. Soc. 121 (1999) 10634–
10635.
Both the homogeneous and heterogeneous complexes are active
in oligomerization reactions. The reactions of ethylene with heter-
ogeneous complexes were less active than their homogeneous ana-
logues; however, they were more selective for both C4and
a-C4
fractions. The addition of silica served as a support for the com-
plexes and also acted as a steric hindrance, preventing the forma-
tion of internal olefins.
[19] C. Bianchini, G. Giambastiani, L. Luconi, A. Meli, Coord. Chem. Rev. 254 (2010)
431–455.
[20] G.C. Vernon, S.K. Spitzmesser, Chem. Rev. 103 (2003) 283–315.
[21] G.J.P. Britovsek, V.C. Gibson, D.F. Wass, Angew. Chem. Int. Ed. 38 (1999) 428–
447.
[22] D.S. McGuinness, Chem. Rev. 111 (3) (2011) 2321–2341.
[23] L. Bourget-Merle, M.F. Lappert, J.R. Severn, Chem. Rev. 102 (2002) 3031–3065.
[24] D.J. Mindiola, Angew. Chem. Int. Ed. 48 (2009) 6198–6200.
[25] C.J. Brinker, G.W. Scherer, Sol–Gel Science the Physics and Chemistry of Sol–
Gel Processing. San Diego, 1990.
[26] R.A. Sheldon, I.W.C.E. Arends, H.E.B. Lempers, Collect. Czech. Chem. Commun.
63 (1998) 1724–1742.
[27] A.P. Wight, M.E. Davis, Chem. Rev. 102 (2002) 3589–3614.
[28] B. Meunier, Chem. Rev. 92 (1992) 1411–1456.
[29] J.S. Beck, J.C. Vartulli, W.J. Roth, M.E. Leonowicz, C.T. Kresge, K.D. Schmitt, C.T.-
W. Chu, D.H. Olson, E.W. Sheppard, S.B. McCullen, J.B. Higgins, J.L. Schlenker, J.
Am. Chem. Soc. 114 (1992) 10834–10843.
[30] K.M. Parida, S. Singha, P.C. Sahoo, J. Mol. Catal. A: Chem. 325 (2010) 40–47.
[31] S. Kumari, B. Malvi, A.Kr. Ganai, V.K. Pillai, S. Gupta, J. Phys. Chem. C 115 (2011)
17774–17781.
In the propylene oligomerization reactions, totally unexpected
results were obtained when using toluene as a solvent in the reac-
tions with heterogeneous complexes. The homogeneous com-
plexes produced nearly the same range of C6 olefins, and the
heterogeneous complexes produce practically only alkylation
products. Products in the range of C6 for both homogeneous and
heterogeneous complexes are preferably branched, and higher pro-
duction was obtained from c4M2P. The products obtained from the
alkylation of toluene with heterogeneous complexes can be
explained by the contribution from the Lewis acidity of the
MCM-41 support, as determined from the blank testing.
Propylene oligomerization reactions using cyclohexane as a sol-
vent were performed. The products were only in the range of C6.
The reactions were less active than reactions using toluene as a sol-
vent, most likely due to the lower solubility of propylene in
cyclohexane.
[32] A.S.M. Chong, X.S. Zhao, J. Phys. Chem. B 107 (2003) 12650–12657.
[33] J. Zhang, H. Gao, Z. Ke, F. Bao, F. Zhu, Q. Wu, J. Mol. Catal. A: Chem. 231 (2005)
27–34.
[34] Y. Li, L. Wang, H. Gao, F. Zhu, Q. Wu, Appl. Organometal. Chem. 20 (2006) 436–
442.
Recycle reactions were performed using the heterogenized HC1
complex, which was shown to be active in recycle reactions and is,
therefore, promising for large-scale use.
[35] M.E. Bluhm, C. Folli, D. Pufky, M. Kröger, O. Walter, M. Döring, Organometallics
24 (2005) 4139–4152.
[36] M.T.N. Villalba, Tese de doutorado, Instituto de Tecnologia de Valência, 1997.
[37] B.J. Hathaway, D.G.J. Holah, J. Chem. Soc. (1964) 2400–2408
[38] M. Kruk, M. Jaroniec, Y. Sakamoto, O. Terasaki, R. Ryoo, C.H. Ko, J. Phys. Chem.
104B (2000) 292–298.
Heterogeneous MCM-b-diimine nickel complexes are very
promising for the oligomerization reactions of ethylene and pro-
pylene. One can change the reaction parameters to obtain the
desired products.
[39] W. Hammond, E. Prouzet, S.D. Mohanti, T.J. Pinnaviam, Micropor. Mesopor.
Mater. 27 (1999) 19–25.
[40] M. Kruk, M. Jaroniec, Chem. Matter. 13 (2001) 3169–3183.
[41] J.L. Blin, C. Otjacques, G. Herrier, B.-L. Su, Int. J. Inorg. Mater. 3 (2003) 75–86.
[42] R.F. de Souza, K.B. Gusmão, G.A. Cunha, C. Loup, F. Leca, R. Reau, J. Catal. 226
(2004) 235–239.
[43] S.A. Svejda, M. Brookhart, Organometallics 18 (1999) 65–74.
[44] S.O. Ojwach, I.A. Guzei, L.L. Benade, S.F. Mapolie, J. Darkwa, Organometellics 28
(2009) 2127–2133.
[45] J. Rigoreau, S. Laforge, N.S. Gnep, M. Guisnet, J. Catal. 236 (2005) 45–54.
[46] J. Joni, M. Haumann, P. Wasserscheid, Appl. Catal. A: Gen. 372 (2010) 8–15.
[47] R.M. Enus, S.F. Mapolie, Inorg. Chim. Acta 409 (2014) 96–105.
[48] M.K. Ainooson, S.O. Ojwach, I.A. Guzei, L.C. Spencer, J. Darkwa, J. Organomet.
Chem. 696 (2011) 1528–1535.
Acknowledgments
The authors thank CAPES and CNPq for financial support,
CNANO UFRGS for the NMR analyses, the CME UFRGS for analysis
of the electron micrographs and transmission images, Cristiano
Favero for analysis of the adsorption–desorption isotherms, and
Isabel Vincent for his help in the propylene gas chromatography
analysis.
References
[49] P.W. Dyer, J. Fawcett, M.J. Hanton, Organometallics 27 (2008) 5082–5087.
[50] P. Prokesová, N. Zilková, S. Mintova, T. Bein, Appl. Catal. A: Gen. 281 (2005) 85–
91.
[51] G.S. Nyamato, S.O. Ojwach, M.P. Akerman, J. Mol. Catal. A: Chem. 394 (2014)
274–282.
[1] A. Forestière, H. Olivier-Bourbigou, L. Saussine, Oil Gas Sci. Technol. Rev. IFP 64
(2009) 649–667.
[2] A. Kermagoret, R.N. Kerber, M.P. Conley, E. Callens, P. Florian, D. Massiot, F.
Delbecq, X. Rozanska, C. Copéret, P. Sautet, J. Catal. 313 (2014) 46–54.
[3] C. delPozo, A. Corma, M. Iglesias, F. Sánchez, Organometallics 29 (2010) 4491–
4498.
[52] K. Bouchmella, P.H. Mutin, M. Stoyanova, C. Poleunis, P. Eloy, U. Rodemerck,
E.M. Gaigneaux, D.P. Debecker, J. Catal. 301 (2013) 233–241.