Structurally uniform 1-hexene, 1-octene, and 1-decene oligomers: Zirconocene/MAO-catalyzed preparation, characterization, and prospects of their use as low-viscosity low-temperature oil base stocks

Article abstract of DOI:10.1016/j.apcata.2017.09.016

An original approach to α-olefin oligomerization as well as novel thermally stable zirconocene catalysts for use in such reactions has been elaborated. The method reported allows the achievement of fractions of lightweight α-olefin oligomers up to 90% yields without considerable formation of byproducts like internal alkenes, alkanes, and higher oligomers. Trimers, tetramers, and pentamers of 1-hexene, 1-octene, and 1-decene were isolated as individual compounds and were hydrogenated. Viscosity characteristics of the isolated saturated and unsaturated hydrocarbons have been studied at various temperatures. The isolated saturated oligomers of 1-octene and 1-decene outperform the traditional electrophilic oligomerization products in terms of viscosity indexes, pour points, and low-temperature viscosity.

Full text of DOI:10.1016/j.apcata.2017.09.016

Accepted Manuscript
Title: Structurally uniform 1-hexene, 1-octene, and 1-decene
oligomers: zirconocene/MAO-catalyzed preparation,
characterization, and prospects of their use as low-viscosity
low-temperature oil base stocks
Authors: Ilya E. Nifant’ev, Alexander A. Vinogradov, Alexey
A. Vinogradov, Igor V. Sedov, Viktor G. Dorokhov, Anton S.
Lyadov, Pavel V. Ivchenko
PII:
S0926-860X(17)30445-3
DOI:
Reference:
http://dx.doi.org/10.1016/j.apcata.2017.09.016
APCATA 16410
To appear in:
Applied Catalysis A: General
Received date:
Revised date:
Accepted date:
13-7-2017
11-9-2017
14-9-2017
Please cite this article as: Ilya E.Nifant’ev, Alexander A.Vinogradov, Alexey
A.Vinogradov, Igor V.Sedov, Viktor G.Dorokhov, Anton S.Lyadov, Pavel
V.Ivchenko, Structurally uniform 1-hexene, 1-octene, and 1-decene oligomers:
zirconocene/MAO-catalyzed preparation, characterization, and prospects of
their use as low-viscosity low-temperature oil base stocks, Applied Catalysis A,
Generalhttp://dx.doi.org/10.1016/j.apcata.2017.09.016
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Structurally uniform 1-hexene, 1-octene, and 1-decene oligomers:
zirconocene/MAO-catalyzed preparation, characterization, and prospects of their
use as low-viscosity low-temperature oil base stocks
Ilya E. Nifant'ev,a), b), * Alexander A. Vinogradov,a) Alexey A. Vinogradov,a) Igor V. Sedov,c)
Viktor G. Dorokhov,c) Anton S. Lyadov, a) Pavel V. Ivchenko a), b)
a) A. V. Topchiev Institute of Petrochemical Synthesis RAS, Lenuinsky avenue 29, Moscow 119991,
Russian Federation
b) Department of Chemistry, M. V. Lomonosov Moscow State University, Leninskie Gory 1–3,
Moscow 119991, Russian Federation
c) Institute of Problems of Chemical Physics RAS, Academician Semenov avenue 1, Chernogolovka,
Moscow region 142432, Russian Federation
* Corresponding author. E-mail: inif@org.chem.msu.ru; ilnif@yahoo.com. 119991, Leninskie Gory,
1–3, Moscow, Russian Federation.
Graphical Abstract
Highlights
 Heterocene activated by 10 eq. of MAO is effective in α-olefin oligomerization
 Up to 90% isolated yields of lightweight -olefin oligomer fractions were achieved
 Unsaturated and saturated -olefin oligomers were isolated as individual compounds
 Hydrogenated 1-octene and 1-decene oligomers outperformed conventional PAOs
Abstract
1

An original approach to -olefin oligomerization as well as novel thermally stable zirconocene
catalysts for use in such reactions has been elaborated. The method reported allows the achievement of
fractions of lightweight -olefin oligomers up to 90% yields without considerable formation of
byproducts like internal alkenes, alkanes, and higher oligomers. Trimers, tetramers, and pentamers of
1-hexene, 1-octene, and 1-decene were isolated as individual compounds and were hydrogenated.
Viscosity characteristics of the isolated saturated and unsaturated hydrocarbons have been studied at
various temperatures. The isolated saturated oligomers of 1-octene and 1-decene outperform the
traditional electrophilic oligomerization products in terms of viscosity indexes, pour points, and low-
temperature viscosity.
Keywords: α-olefins, oligomerization, zirconocenes, oil base stocks, viscosity
1. Introduction
Saturated high-boiling hydrocarbons are traditionally used as base stocks of engine oils and
lubricants. Hydrocarbon-based oils can be divided into four groups of products [1]. Group I represents
the dewaxed and deasphalted crude oil fractions, whose catalytic hydrogenation leads to Group II oils.
Group III represents semi-synthetic oils produced by the catalytic hydrocracking of higher crude oil
distillates. This process is accompanied by partial transformation of linear paraffins into branched
saturated hydrocarbons. Group IV represents fully synthetic oils, which comprise the hydrogenated -
olefin oligomers. Compounds that belong to this group are generally called poly-alpha-olefin (PAO)
oils or PAOs. High-quality engine oil should have moderate viscosity at low temperatures, which is
necessary for a safe "cold start" of the engine. The reliability of engine oil at low temperatures is
characterized in terms of the pour point (PP) and kinematic viscosity at −40 °C (KV–40). At the same
time, engine oil should remain viscous at working engine temperatures to minimize friction and engine
aging. A commonly accepted quantitative characteristic that describes the dependence of oil viscosity
on the temperature is the viscosity index (VI), which is determined by a standard method, ASTM D-
2270, in which the values of kinematic viscosity of an oil at 40 °C (KV40) and 100 °C (KV100) are
compared against the viscosities of two reference oils.
It was found that the PP and VI values of oils depend strongly on the architecture of the
constituent hydrocarbons [2–5]. Long, linear hydrocarbons, petroleum waxes (Fig 1A), present in high
quantities in Group I and II oils, are characterized by high PPs. It is for this reason that Group I and II
oils cannot be used at low temperatures. Group III oil base hydrocarbons, which contain compounds
2

with short branches (Fig 1B) and cycloalkanes (Fig 1C), also have relatively high PP and KV–40
values. On the other hand, long-chain branched hydrocarbons (Fig 1D) are characterized by low PPs
and high VIs. Oligomerization of -olefins followed by hydrogenation is the only way to obtain
hydrocarbons with the structure type D [3]. An important aspect of PAO use is their biodegradability,
which is also dependent from the hydrocarbon molecular structure. It has been determined [6] that the
presence of quaternary carbon atoms blocks the oxidative breakdown of hydrocarbons in surrounding
media. It has been reported [7] that PAOs based on 1-decene are characterized by satisfactory
biodegradability, surpassing that of Group III oils. Therefore, structural type D offers prospects in
minimizing the environmental impact of the use of PAOs.
Compounds of the structural type D are targeted for Group IV base stock synthesis via -olefin
oligomerization. However, bulk scale production of low-viscosity PAOs utilizes electrophilic catalysis
with significant skeletal isomerization (Scheme 1a). In particular, many methyl groups are generated at
random positions along the carbon chain with formation of type B structures [4,5,8]. In some cases,
alicyclic type C products are formed [9–11]. These skeletal isomerizations lead to complex
hydrocarbon mixtures containing spillover components having lower viscosity indexes than those of
targeted type D hydrocarbons. An alternative approach to olefin oligomer synthesis is based on
coordination polymerization. Various catalytic systems using this process have been studied. It has
been determined that coordination oligomerization in the presence of heterogeneous titanium–
aluminum [12,13] and chromium [14] Ziegler–Natta catalysts is also accompanied by skeletal
rearrangements. Isomerization of the skeleton has been observed even for oligomerization catalyzed by
dimethylzirconocenes, activated by perfluoroborates [15], and post-metallocene catalysts [16–18].
It was found that undesirable side reactions are minimal for oligomerization of -olefins when
the process is catalyzed by zirconocene dichlorides (LZrCl2) activated by methylalumoxane (МАО)
[19–22]. In this case, chain growth occurs only by 1,2-insertions and the chain terminates by β-hydride
elimination or β-hydride transfer. As a result, the products of this process characterized by Flory-
Shultz distribution are vinylidene-type -olefin oligomers with uniform molecular structures (Scheme
1b). Vinylidene dimers of -olefins are not suitable for use as oil base stocks because of their low VI
and high PP. However, they can be transformed into hydrocarbons structurally similar to type D
species by electrophilic dimerization (Scheme 1c) [23].
To date, vinylidene dimers of 1-hexene, 1-octene, and 1-decene have been isolated and
characterized [23–26]. Higher -olefin oligomers prepared by single-site catalysis have been usually
isolated in the form of mixtures with a large Pn range [26–32]. Thus, the characteristics of individual
3

oligomers and hydrogenated oligomers of 1-hexene, 1-octene, and 1-decene as a components of PAO
base stocks are currently unknown. The determination of these characteristic remains a fundamental
issue.
The main practical issue of zirconocene catalysis of -olefin oligomerization to obtain type D
hydrocarbons lies in reaching the maximum isolated yield of dimers and lower oligomers,
corresponding to a degree of oligomerization Pn = 2 and 3–5, respectively. The problem in the
selective synthesis of -olefin dimers (Pn = 2) has been successfully solved by using low AlMAO/Zr
ratios (1–10 by mol) and zirconocene catalysts of specific structural types. It was reported that
zirconocene dichloride (η5-C5H5)ZrCl2 (1) [24–27], ring monosubstituted zirconocenes [29], and ansa-
complexes Z(C5H4)2ZrCl2 [33] selectively dimerize -olefins in the presence of a minimal excess of
MAO activator to produce dimers of the vinylidene structure (Scheme 1). It has been found that an
increase in the AlMAO/Zr ratio for reactions of 1, (η5-C5H4R)ZrCl2, and certain ring disubstituted
zirconocenes leads to the growth of the proportion between the contents of lower oligomers and
dimers, which can reach ~1:1 [26,29,31,34,35]. Basing on GC data, Kissn and Schwab [23,36]
reported that 1 and (n-BuC5H4)2ZrCl2 (2) are very effective in 1-hexene and 1-decene oligomerization
at AlMAO/Zr = 200.
At first glance, the effectiveness of the -olefin oligomerization process can be qualified only
by the distribution of lightweight -olefin oligomers, since the mass fraction of higher oligomers
usually does not exceed several mass percent. However, real yields of oligomers are also affected by
some side processes. One such process is the isomerization of initial -olefins. In our recent work [37],
we showed that internal alkenes can comprise as much as 25% of the yield during zirconocene-
catalyzed oligomerization. Another such side reaction is the reduction of starting -olefins and the
formation of n-alkanes through hydroalumination. This reaction is stimulated on increasing the
AlMAO/Zr ratios and has not been studied yet.
In this paper, we report our study of -olefin oligomerization catalyzed by a series of catalysts
derived from zirconocenes 1–14 (Scheme 2), at medium (200) and low (10) AlMAO/Zr ratios. We found
that the catalyst prepared from the heterocyclic zirconocene 14 demonstrated the best performance. As
far as -olefin oligomerization in the presence of zirconocene 14 at low AlMAO/Zr ratios went without
any isomerization of the skeleton, we have managed to isolate for the first time and study as individual
compounds the trimers, tetramers, and pentamers of 1-hexene, 1-octene, and 1-decene and the products
of their hydrogenation. Moreover, we studied the physical properties and viscosity indexes of the
newly obtained unsaturated and saturated hydrocarbons and compared the data obtained with known
characteristics of conventional oligomers prepared using electrophilic catalysts. The results of this
4

comparison allowed us to draw conclusions regarding the use of zirconocene oligomers as PAO base
stocks.
2. Experimental section
2.1. Solvents, reagents and catalysts
Benzene, n-heptane, 1-hexene, 1-octene and 1-decene (Sigma-Aldrich) were stored over Na
wire and distilled under argon. Diethyl ether was refluxed over Na/benzophenone and distilled under
argon. CH2Cl2 was refluxed over CaH2 and distilled before use. MAO (1.51M solution in toluene),
MMAO-12 (1M solution in toluene), TIBA (1M solution in hexane), 2-methylthiophene,
chlorotrimethylsilane (TMSCl), ZrCl4, SnCl4, propionyl chloride, (η5-C5H5)2ZrCl2 (1) and (η5-C5H4- n-
Bu)2ZrCl2 (2) were used as purchased (Sigma-Aldrich). Zirconocene pre-catalysts 3 [37], 4 [38], 5
[33,39], 6 [40], 7 [41], 8 [42], 9 [43], 10 [44], 11 [45], 12 and 13 [46] (Scheme 2) were synthesized
according to previously reported procedures.
2.2. Analysis
CDCl3 (Cambridge Isotope Laboratories, Inc., D 99.8 %) was used as purchased. The 1H and
13C NMR spectra were recorded on a Bruker AVANCE 400 spectrometer (400 MHz) at 20 °C. The
chemical shifts are reported in ppm relative to the solvent residual peaks.
The distribution of α-olefin oligomers produced in zirconocene-catalyzed reactions and the
conversion of the oligomers in post-oligomerization reactions were measured by gas chromatography
(GC) method. GC analysis was carried out with a KRISTALL-2000M gas chromatograph equipped
with a SolGel-1ms (60m×0.25mm×0.25m) column and a flame ionization detector. Helium was used
as a carrier gas at a rate of 1.364 cc/min and with a split ratio of 73.3 : 1. The injection temperature
was 320 °C, and the column temperature was 200 °C within 5 min and then increased from 200 °C to
300 °C at a rate of 10 °C/min.
Size exclusion chromatography (SEC) of polyhexene samples was performed on an Agilent
PL-GPC 220 chromatograph equipped with a PLgel column, and THF was used as the eluent (1
mL/min). The measurements were recorded with universal calibration according to a polystyrene
standard at 40 °C. Elemental analysis (C, H) was performed on a Perkin Elmer Series II CHNS/O
Analyzer 2400.
2.3. Preparation of zirconocene 14
5

All of the synthesis experiments were conducted under an argon atmosphere. Zirconocene 14
was prepared in six stages starting from 2-methylthiophene (Scheme 3) and characterized by 1H, 13C
NMR spectroscopy (see Appendix A) and by elemental analysis.
2.3.1. 1-(5-Methyl-2-thienyl)-1-propanone
SnCl4 (117 g, 450 mmol) was added dropwise to a well-stirred solution of propionyl chloride
(41.6 g, 450 mmol) and 2-methylthiophene (44.1 g, 450 mmol) in dry benzene (300 mL) at 0 °C. The
solution was allowed to warm to room temperature and stirred for additional 16 h. HCl (10% aq., 500
mL) was added dropwise, water phase was extracted by benzene (3100 mL), combined organic
fraction was washed by water, aq. NaHCO3, and dried over MgSO4. Solvent was removed under
reduced pressure, and the residue was distilled in vacuo. B.p. 100–106 °C/10 Torr. The yield was 50.0
g (72%) as a pale-yellow liquid. 1H NMR (CDCl3, 20 °C) : 7.54 (d, 1H); 6.80 (d, 1H) {-CH=}; 2.89
(q, 2H, -CH2-); 2.54 (s, 3H, -CH3); 1.23 (t, 3H, -CH3).
2.3.2. 2-Methyl-1-(5-methyl-2-thienyl)-2-propen-1-one
1-(5-Methyl-2-thienyl)-1-propanone (50 g, 324 mmol), hexamethylenetetramine (63.6 g, 454
mmol) and Ac2O (56 mL, 583 mmole) were mixed in a 250 mL flask, sparged with argon, and stirred
for 48 h at 100 °C. The mixture was cooled to 60 °C and poured into 1 L of 2M aq. NaOH. The
resulting mixture was extracted by CH2Cl2 (5250 mL), combined organic fraction was washed by
1M HCl, aq. NaHCO3, and dried over MgSO4. Evaporation of solvents gave crude product (~55 g,
80% of desired compound by NMR) used without further purification. 1H NMR (CDCl3, 20 °C) :
7.50 (d, 1H); 6.80 (d, 1H) {-CH=}; 5.76 (bs, 1H); 5.73 (bs, 1H) {=CH2}; 2.54 (s, 3H, -CH3); 2.05 (s,
3H, -CH3).
2.3.3. 2,5-Dimethyl-4,5-dihydro-6H-cyclopenta[b]thiophen-6-one
Crude 2-methyl-1-(5-methyl-2-thienyl)-2-propen-1-one in CH2Cl2 (50 mL) was added to
heated to 50 °C MSA (260 mL). The resulting mixture was stirred for 2 h, poured into ice/water (500
mL) and extracted by CH2Cl2 (5200 mL). Combined organic phase was washed by aq. KHCO3,
water, and dried over MgSO4. The resulting dark brown solution was evaporated and distilled in vacuo
(b.p. 105-120 °C/1 torr) yielding 17.74 g of the product as colourless liquid. The yield based on 1-(5-
methyl-2-thienyl)-1-propanone was 32.9%. 1H NMR (CDCl3, 20 °C) : 6.66 (s, 1H, -CH=); 3.12 (dd,
2J = 16.5 Hz, 3J = 7.0 Hz, 1H); 2.85 (ddt, 3J = 7.0 Hz, 7.0 Hz, 2.8 Hz, 1H); 2.41 (dd, 2J = 16.5 Hz, 3J =
2.8 Hz, 1H) {ABC of C5 ring}; 2.49 (s, 3H, -CH3); 1.23 (d, 3J = 7.0 Hz, 3H, -CH3). 13C NMR (CDCl3,
20 °C) : 199.4 (>C=O); 167.3; 157.0; 137.5 (>C=); 122.4 (-CH=); 46.1; 16.4 (-CH3); 32.7 (-CH2-).
6

2.3.4. 2,5-Dimethyl-4H-cyclopenta[b]thiophene
2,5-Dimethyl-4,5-dihydro-6H-cyclopenta[b]thiophen-6-one (8.31 g, 50 mmol) in Et2O (30 mL)
was added dropwise to cooled (–40 °C) suspension of LiAlH4 (0.52 g, 13.8 mmole) in Et2O (100 mL).
The resulting mixture was allowed to warm to room temperature and stirred for additional 1 h. Then
H2O (10 mL) was added, the resulting suspension was poured into CH2Cl2 (200 mL) and filtered.
Organic phase was washed by water and evaporated. The flask was sparged with argon; benzene (150
mL) and p-TsOH (0.3 g) were added, and the resulting solution was refluxed with Dine-Stark head
(control by TLC, benzene/EtOAc 4:1) within ~40 min. Then the resulting yellow solution was washed
by water, aq. KHCO3, dried over MgSO4, passed through silica gel (benzene), evaporated and dried in
vacuo yielding 6.5 g (86.5%) of yellow oil. 1H NMR (CDCl3, 20 °C) : 6.72 (bs,1H) {thiophene ring};
6.42 (m); 6.38 (m) {=1H; -CH= of cyclopentadienyl ring}; 3.22 (bs, 1H); 3.12 (bs, 1H) {=2H, -
CH2-}; 2.55 (s, 3H, -CH3 of thiophene ring); 2.51 (bs); 2.17 (bs) {3H, -CH3 of cyclopentadiene ring).
2.3.5. Bis(5-2,5-dimethyl-4H-cyclopenta[b]thienyl)dichlorozirconium (IV) 14
n-BuLi (17 mL, 2.5 М in hexane, 42.5 mmol) was added at –60 °C to a solution of 2,5-
dimethyl-4H-cyclopenta[b]thiophene (6.0 g, 40 mmol) in Et2O (50 mL). The resulting mixture was
allowed to warm to room temperature, stirred for 1 h, and cooled to –40 °С. TMSCl (5.6 mL, 44
mmol), was added, the mixture was stirred for 12 h at room temperature, and filtered. Solvents were
removed under reduced pressure, toluene (10 mL) was added, and removed in vacuo to eliminate the
traces of the ether. The residue was dissolved in CH2Cl2 (80 mL), the mixture was cooled to –40 °С,
and ZrCl4 (4.6 g, 19.7 mmol) was added. The mixture was allowed to warm to room temperature,
stirred for 12 h, volatiles were removed under reduced pressure. The residue was dissolved in CH2Cl2
(20 mL), n-hexane was added dropwise at room temperature until the beginning of the crystallization.
The resulting mixture was stored overnight at –20 °C. Light green crystalline product was filtered off,
the residue was evaporated to one half of the initial volume and stored for 3 days at –20 °C. The
crystalline product was filtered off and combined with the first portion of the product. The yield was
6.2 g, 68%. 1H NMR (CDCl3, 20 °C) : 6.69 (m); 6.67 (m) {1H, thiophene ring}; 5.93 (bs); 5.80 (bs)
{1H}; 5.74 (bs); 5.46 (bs) {1H}; 2.52 (s, 3H); 2.17 (s, 3H). 13C NMR (CD2Cl2, 20 °C) : 147.58;
147.46; 137.92; 136.82; 136.00; 135.41; 129.41; 128.04; 116.94; 116.90; 105.27; 104.53; 104.09;
103.64; 17.29; 16.69. Elemental Analysis: Calc. C, 46.94%; H, 3.94%. Found: C, 47.03%; H, 3.90%.
2.4. Oligomer preparation and characteristics
All of the synthetic experiments were conducted under an argon atmosphere.
7

Oligomerization of 1-hexene, 1-octene and 1-decene to prepare individual oligomers was
carried out in bulk or in n-heptane solution using 2 mol of α-olefin, 10 mmol of zirconocene dichloride
catalyst activated subsequently by 200 mmol of TIBA and 100 mmol of MMAO-12 as reported ealier
[33]. After treatment with a minimal quantity of ethanol and water, the reaction mixtures were rectified
in vacuo. The basic characteristics of the products (boiling points, GC retention times) are provided in
Appendix A. The isomeric purity of the products is confirmed by GC, and by the absence of 4.9-6 ppm
peaks in 1H NMR spectra. 1H and 13C NMR spectra of all obtained oligomers are provided in
Appendix A.
Dimerization of α-olefin dimers H2 (1-hexene dimer), O2 (1-octene dimer) and D2 (1-decene
dimer) was conducted in the presence of tert-BuCl and EtAlCl2 (1% mol) at –30 °С. 98% dimer
conversion was achieved after two hours. After treatment with a minimal quantity of methanol and
aqueous KHCO3 the reaction mixtures were rectified in vacuo. Results: 1-hexene dimer of dimer H22
(yield 92%, B.p. 140-142 °C/ 0.1-0.2 Torr), 1-octene dimer of dimer O22 (yield 89%, B.p. 196-200
°C/ 0.1-0.2 Torr) and 1-decene dimer of dimer D22 (yield 84%, B.p. 230-235 °C/ 0.1-0.2 Torr). For
spectral data, see Appendix A.
2.5. Hydrogenation of oligomers
Hydrogenation was performed in a stainless steel apparatus with mechanical stirrer, equipped
with temperature and pressure sensors. Oligomer mixture and Pd/Al2O3 catalyst (0.1% Pd) in molar
ratio 3000:1 were loaded, apparatus was filled with hydrogen via a three-fold increase of pressure to 3-
5 bar with subsequent decrease to 0.1 bar. The process was conducted at 88–90 °С and hydrogen
pressure of 10-11 bar; the magnetic stirrer was set to 500-550 rpm. The hydrogenation was finished
after the hydrogen absorption rate was reduced 100-fold, after which the reaction mixture was
separated from the catalyst and analyzed by GC and 1H NMR spectroscopy. For spectral data, see
Appendix A.
2.6. Viscosity and Pour point determination
The kinematic viscosity of the oligomers at 40, 100 and –40°С was determined in accordance
with ASTM D445-17 after a certain volume of liquid passed under gravitational pull through a
calibrated capillary flow meter. VI values were calculated according to the ASTM D2270-10 (2016).
Pour points were determined in accordance with ASTM D97 method.
Oil density at 20 °С was determined with a pycnometer in accordance with ASTM D1480. Oil
density at -40°С was calculated with the formula:
8

dt = d20 – Δt(t – 20),
where Δt is the temperature differential to density per 1 degree, calculated by:
Δt = (18.319 – 13.233·d20) ·10–4
3. Results and discussions
3.1. Zirconocene-catalyzed α-olefin oligomerization at the ratio MAO/Zr = 200
We began our work with the investigation of 1-hexene, 1-octene, and 1-decene oligomerization
with catalysts prepared from the zirconocenes 1 and 2 by activating them with significant excesses of
MAO up to AlMAO/Zr ratios ≈ 200. These catalysts were first studied by Kissin and Schwab [23] and
have been reported as effective in olefin oligomerization. In our experiments, we used a MMAO-12
dissolved in heptane along with standard MAO. The results are summarized in Table 1.
We found that zirconocene dichloride 1 activated by 200 eq. of MMAO-12 at 60 °C
demonstrated high activity in the oligomerization of 1-hexene, 1-octene, and 1-decene. 99% monomer
conversion was achieved after 4 h (Table 1, runs 1–3). Investigation of the product yields
demonstrated fractions with Pn = 2–5 (dimer and lightweight -olefin oligomers) comprising 65.5%
(1-hexene) to 73.4% (1-decene) of the products. In most cases, -olefin oligomer distribution could be
described by Flory-Schulz equation and a parameter  which correlates with relative rates or
propagation vs termination (Table 1, column 6) [47]. For runs 1–3,  are 0.25 (1-hexene), 0.30 (1-
octene) and 0.33 (1-decene).
The fraction of higher-weight -olefin oligomers was inversely proportional to the starting
hydrocarbon length, ranging from 21% for 1-hexene to 11.7% for 1-decene. We also observed
formation of ~1% internal alkenes (mainly, 2-alkenes) and 12–14% n-alkanes (n-hexane, n-octane and
n-decane). n-Alkanes formation under high Al/MAO ratio can be attributed to alklyl transfer to
aluminium processes. Therefore, with 1, primarily -olefin dimers are formed and yields of lower
oligomers do not exceed 30%. Assuming high loss of the initial olefin due to formation of alkanes and
internal alkenes, zirconocene dichloride 1 at AlMAO/Zr ≈ 200 cannot be considered an effective
oligomerization catalyst.
The data we obtained for complex 2 (Table 1, run 5) were considerably different from those
published in [23] (Table 1, run 4).1 In our experiments at 70 °C using 2 activated by 200 eq. of МАО,
conversion of 1-hexene after 4 h was 91%, and the resulting reaction mixture contained only 19.9 wt%
of vinylidene dimer. Approximate yield of the fraction, corresponding to Pn = 2–5 (dimer and
lightweight oligomers), was 53.6%. Replacing MAO with MMAO-12 (Table 1, run 6) led to an
1 The closest result to these data is the spread of oligomers obtained during catalysis of 1 (run 1).
9

insignificant increase in the conversion and an increased dimer fraction in the products without change
of  value (0.49 and 0.48, respectively); the fraction of higher-weight oligomers (Pn > 5) decreased
from 32.8 to 22.6%. In both cases, we observed a formation of ~1.5% of internal hexenes and
significant quantities (about 12 wt%) of hexane.2 We also studied the oligomerization of 1-hexene in
the presence of 2 in a hydrogen atmosphere (Table 1, run 7). The hydrogen pressure was 1 bar and did
not practically affect the yield of the targeted fraction (61.5%) with the dimer/lightweight oligomer
ratio at 0.87. However, the quantity of internal hexenes in the products decreased to 0.3%, but the
quantity of n-hexane increased to 14%. We also investigated the oligomerization of 1-hexene in bulk
(Table 1, run 9). An insignificant increase in the conversion was accompanied by increase of the
higher-weight oligomer fraction in the reaction products to 41%; yield of the targeted fraction (dimer
and lightweight oligomers) constituted only 45.1%. Oligomerization experiments for 1-octene and 1-
decene in the presence of 2 allowed us to achieve 71–72% yield of the target fraction with a
dimer/lightweight oligomer ratio of 0.73 and 0.81, respectively. Therefore, use of the zirconocene 2
activated by 200 eq. of MAO allowed us to achieve satisfactory dimer/lightweight oligomer ratios (up
to ~1:1). However, the isolated yield of the target compounds, vinylidene dimers and lightweight
oligomers, amounted to about 70%. A significant part of the initial olefin, up to 15%, was wasted
because of the formation of isomerization products, internal alkenes and α-olefin reduction products.
Therefore, considering the losses of α-olefins due to the formation of n-alkanes and the high
cost of MAO, as well as the obvious preparatory difficulties at the step of hydrolyzing the reaction
mixtures with a high concentration of aluminum–organic compounds, the use of high ratios of
AlMAO/Zr in zirconocene-catalyzed α-olefin catalysis is ineffective.
3.2. Zirconocene-catalyzed -olefin oligomerization at MAO/Zr ratio = 10
In order to increase the target product yield and reduce the loss of α-olefins arising after the n-
alkane formation via alkyl transfer to aluminium side reaction, we turned to low AlMAO/Zr ratios in
oligomerization experiments. Since zirconocene dichlorides do not effectively transform into an active,
soluble form after treatment with a few eq. of MAO, in our catalytic experiments we used a recently
developed method [33] based on the subsequent interaction of zirconocene dichloride with 20 eq. of
TIBA and 10 eq. of MMAO-12. At the first stage of this study, we examined the catalytic properties of
a range of described zirconocene dichlorides 1–13 (Scheme 2) during oligomerization of 1-hexene in
bulk at 60 °С (monomer/Zr ratio = 2000:1). In all experiments (Table 2, runs 1-6, 9, 10) relative low n-
alkane formation was detected, due to use of relative low Al/Zr ratios.
2 The exact calculation of hexane levels in reaction products by GC was difficult due to the use of TIBA solution in hexane.
10

We determined that the zirconocenes 1–13 demonstrate markedly different reactivities
depending on their structure (Table 2, runs 1–13). Zirconocene dichloride 1 (Table 2, run 1) primarily
catalyzed the formation of 1-hexene dimers; α was only 0.11. The yields of lightweight oligomers and
internal hexenes were only 12.2% and 3.4%, respectively. The fraction of the monomer reduction
product (n-hexane) did not exceed 2%. We found that if ring monosubstituted bis-cyclopentadienyl
complexes 2, 4, and 5 are used, significant quantities of oligomer products are formed along with the
1-hexene dimer (α = 0.55, 0.44 and 0.38, correspondingly). The catalyst productivity depends on the
type of substituents in cyclopentadienyl rings. Zirconocenes 2 and 5 are comparable to 1 with respect
to activity, while complex 4 is not very active. Lightweight oligomers fraction yield with catalysis by 2
was 70.8% (dimer/lightweight oligomers ratio of 0.98) with 20% yield of high-weight oligomers, with
over 7% internal hexenes and ~2% of n-hexane. Complex 3, which we studied earlier [37],
demonstrated properties similar to those of 2 and 5 (α = 0.41). However, the dimer/lightweight
oligomers ratio for this complex was 1.33. We found that catalysis with disubstituted (such as 6, α =
0.81) or mixed-ligand indenyl-cyclopentadienyl complexes 9 and 10 (α = 0.50 and 0.52) leads to a
higher concentration of oligomers relative to dimers; however, these zirconocenes are not very
promising for lightweight oligomers preparation due to high concentrations of higher oligomers in the
reaction mixtures. Bis-indenyl complexes 11–13 as well as ring-substituted ansa-zirconocene 8
catalyzed the polymerization reactions. Based on the experiments we performed, one can conclude that
the use of low AlMAO/Zr ratios in olefin oligomerization is reasonable. For example, for zirconocene 2
activated by 10 eq. of MMAO-12 (Table 2, run 2), the target fraction yield was more than 1.5 times
greater than the yields in the presence of 200 eq. of MAO (Table 1, run 9). Complex 2 as well as ansa-
zirconocene 3 had the best characteristics among the examined zirconocenes 1–13. Target fraction
yields (Pn = 2–5) for these complexes were similar and amounted to ~70%. On catalyzing with
complex 2 (Table 2, run 2), the yield of the lightweight oligomer fraction (Pn = 3–5) was significantly
higher (35.7% vs 29.3% for 3). On the other hand, reaction with 2 showed higher losses for
isomerization into internal hexenes.
Complexes 2 and 3 were used in studying the oligomerization of 1-hexene, 1-octene, and 1-
decene with the purpose to optimize the yields of lower α-olefin oligomers. The results of the
conducted experiments are summarized in Table 3 (runs 1–13). For zirconocene 2, we studied the
influence of hydrogen, the monomer type, and the temperature on the product distribution. We
determined that, at 1 bar of hydrogen during oligomerization of 1-hexene (Table 3, run 2), the
dimer/lower oligomer ratio increased from 0.98 to 1.65, and the yield of the fraction corresponding to
Pn 3–5 decreased from 35.7% to 30.7%. The introduction of 1-octene (Table 3, run 3) and 1-decene
(Table 3, run 4) into the reaction led to decrease in the catalytic productivity and had very little
influence on the dimer/lower oligomer ratio. When the temperature was raised 100 °С (1-decene), the
11

catalyst partially lost activity and the quantity of the byproducts, internal decenes, increased to 11.2%
(Figure 2).
Similar results were obtained for zirconocene 3. With this catalyst, we were able to synthesize
oligomers of 1-hexene characterized by a dimer/lightweight oligomer ratio of ~1 (Table 3, run 8) with
an isolated yield of 68.4%. Similar yields were achieved with oligomers of 1-octene (Table 3, run 9).
Oligomerization of 1-decene at 100 °C (Table 3, run 10) catalyzed by complex 3 progressed with a
higher productivity than that by 2 (Figure 2), with the fraction of internal decenes in reaction products
comprising 5.6%.
Therefore, “classic” zirconocenes demonstrated a limited applicability in the synthesis of lower
oligomers even at low Al/Zr ratio. The main problems with their use arise from the formation of
significant quantities of internal alkenes (complex 2) or high-weight oligomers (complex 3). The use
of molecular hydrogen or increasing the temperature with the aim to lower the high-weight oligomer
fraction was not effective for 2 due to side reactions, such as the formation of n-alkanes in the presence
of molecular hydrogen and internal alkenes at high temperatures. At AlMAO/Zr = 200, the
oligomerization catalyzed by zirconocene 2 was not influenced by hydrogen. One can suppose that the
mechanism of chain release in primary alkyl complex A during oligomerization at AlMAO/Zr ~ 10
(Scheme 3) “switches” from traditional -hydride transfer [36] to -hydride elimination. This
mechanism was proposed earlier by Bergman [24,25] for selective dimerization of -olefins. After -
hydride elimination, the zirconocene-hydride complex B is formed [24]. This complex, compared to
primary alkyl complex A (Scheme 3), is less sterically hindered and more susceptible to monomer 2,1-
insertion. Products of monomer 2,1-insertion, such as secondary alkyl complexes C, represent the
"resting states" in zirconocene-catalyzed polymerization. Their reactivation can run via isomerization
into primary alkyl complexes as well as via -hydride elimination with internal alkene formation [48]
(Scheme 3).
The high concentration of internal alkenes in oligomerization products can be considered as an
experimental criterion of -hydride elimination and low regioselectivity of -olefin
coordination/insertion in hydride complex B. Besides generally slowing down the reaction and
formation of 2-alkenes, 2,1-insertion hinders the use of molecular hydrogen. In the presence of
hydrogen, the main reaction pathway becomes hydrogenation of the Zr-C bond and the formation of n-
alkanes, which leads to decreased target oligomer product yields. Both side reactions were observed
for zirconocene complexes 2 and 3, with 3 only moderately surpassing 2 in terms of regioselectivity.
12

The results of the performed experiments allowed us to formulate the criteria for a promising
oligomerization catalyst. This catalyst should be very regioselective that can be demonstrated by the
formation of low amounts of internal alkenes, and should be characterized by relatively high α level.
Besides, it should be very stable, retaining high productivity at high temperatures and low ratios of
AlMAO/Zr.
3.3. Novel zirconocene catalyst for -olefin oligomerization
It is known that zirconocenes derived from cyclopentadienes with condensed donor
heterocyclic fragments (heterocenes) demonstrate high thermal stability and productivity even at low
ratios of AlMAO/Zr [49–56]. We proposed that -olefin oligomerization can be effectively performed
with a heteroanalogue of bis-indenyl complex 11, which catalyzed the formation of low-molecular-
weight polyhexene at 60 °C (Table 2, run 11). We elaborated the synthesis of a new zirconocene 14
(Scheme 4) starting from the commercially available 2-methyl-thiophene and using an effective Si-Zr
transmetallation reaction [46] on the final stage.
We carried out the oligomerization of 1-hexene in bulk catalyzed by 14 (Table 3, run 12) in the
same conditions as those for complexes 1–13 (Table 2, runs 1–13). In contrast to complexes 1–13,
zirconocene 14 demonstrated higher productivity. However, the target product yield (oligomer fraction
with Pn = 2–5) amounted to only 26.2%. At the same time, catalysis with 14 led to the formation of
minimal quantities of internal hexenes (0.8%) with a 0.55 dimer/lightweight oligomer ratio, and α =
0.63. This experiment demonstrated the high potential of the precursor 14. The low concentration of
internal hexenes in oligomerization products allows us to assume that the main mechanism of chain
release at low МАО/Zr ratios is -hydride transfer to the monomer. Both temperature and molecular
hydrogen can be used to regulate the Pn during oligomerization with 14.
We conducted the oligomerization of 1-octene at 60 °C in bulk, and the target fraction yield (Pn
= 2–5) was 52.9%. Increasing the temperature to 100 °C resulted in an increased yield of 60.7%. On
lowering the monomer concentration by adding heptane (1/2 by volume) at 100 °C (Table 3, run 16),
we achieved 86.7% of the target fraction yield (dimer/lightweight oligomers ratio = 1.18, α = 0.43). As
a result of the oligomerization of 1-decene at 100 °C (Table 3, run 18), the yield of the
dimer/trimer/tetramer mixture amounted to 89.1% (dimer/lightweight oligomers ratio = 0.96, α =
0.51). Moreover, we found that oligomerization in a hydrogen atmosphere at an elevated temperature
in the presence of 14 (Table 3, runs 19–25) allowed 77% isolated yields of octene and decene
13

oligomers with ~5% loss due to monomer reduction and ~15% loss due to higher oligomer formation
(α = 0.3-0.6). The resulting oligomers were partially hydrogenated.
Therefore, increasing the temperature and using molecular hydrogen in the case of 14 turned
out to be effective instruments for increasing the yield of lower -olefin oligomers. By using 14, we
undertook preparatory synthesis of 1-octene and 1-decene oligomers (Table 3, runs 22 and 25). Our
method of carrying out oligomerization experiments under ambient pressure did not allow us to
effectively use 14 in the oligomerization of 1-hexene. 1-Hexene oligomers were obtained by catalysis
by 3 (Table 3, run 8).
The high efficiency of 14 in comparison with that of 2 and 3 in the oligomerization of 1-decene
is illustrated in Fig. 2, which shows the fragments of 1H NMR spectra corresponding to vinyl proton
peaks for reaction mixtures of oligomerizations in bulk at 100 °C after 4 h. At this temperature, the
sandwich complex 2 demonstrated the lowest activity. In the presence of both 2 and 3, significant
quantities of internal decenes formed. Conversely, in the presence of 14, almost full monomer
conversion was observed and the formation of 1-decene isomerization products was not significant.
3.4. Characterization of -olefin oligomers
The obtained oligomers were colorless liquids. According to 1H and 13C NMR spectra, all
oligomers contained only vinylidene unsaturation, >C=CH2, and appeared as individual type D (Fig. 1)
compounds from the point of view of structural isomerism. Spectra of all newly obtained compounds
are given in Appendix A; the data for 1-hexene trimer coincided with what has been published earlier
[33,57].
The boiling points of -olefin oligomers, on the whole, correlated with the GC retention times
(see Appendix A). At equal molar weights, the more branched oligomer was characterized by a
slightly lower boiling point, as well as a significantly lower retention time, that that of the less
branched oligomer. For example, С24 hydrocarbons H4 and O3 were characterized by relatively close
boiling points of 392 and 396 °С at 760 Torr, respectively. The retention time of H4 was 13.18 min
and 14.79 min for O3. This observation should be considered when separating and analyzing the
hydrocarbon mixtures by GC.
3.5. Dimerization of -olefin dimers
An alternative way to prepare hydrocarbons of definite structure that can be applied to the
production of PAOs consists of dimerization of vinylidene dimers in the presence of acids (Scheme 1с)
to get “dimers of dimers.” These hydrocarbons can also be categorized as long-chain branched (Fig.
14

1D) hydrocarbons, which makes them promising PAO base stocks. It was shown by Kissin and
Schwab that the dimer of 1-decene, in the presence of EtAlCl2/silica, forms C40-hydrocarbons with a
yield of ~80% at room temperature [23]. We have also studied the acid-catalyzed dimerization of -
olefin dimers and found that EtAlCl2 in the presence of ternary chloride, tert-BuCl, is a much more
effective catalyst than EtAlCl2/silica. This catalyst provided more than 95% substrate conversion after
2 h of reaction even at –30 °C. The main reaction products were “dimers of dimers” of H22, O22, and
D22, which were separated by rectification in vacuo with respective yields of 92, 89, and 84%. We
determined that besides the target “dimers of dimers,” isomers of the initial dimers were formed as
reaction byproducts, as well as insignificant (5–7%) quantities of higher oligomers. 1H and 13С NMR
spectra of -olefin “dimers of dimers” H22, O22, and D22 are given in the Appendix A. These
substances represent mixtures of isomers that differed by the position of double bonds.
3.6. Hydrogenation
In the industrial production of PAOs, a nickel catalyst is usually used for -olefin oligomer
hydrogenation. The nickel catalyst is characterized by moderate activity, and the process is carried out
at high temperature and pressure [15,29]. Since the aim of the current study was the synthesis of
individual compounds with defined molecular structures, we preferred not to carry out the
hydrogenation in rigorous conditions. By using a more active catalyst, palladium on aluminum oxide
(0.1% Pd), we performed comprehensive hydrogenation at 90 °С and 10 bar of pressure at a molar
olefin/catalyst ratio of 3000:1. The typical experiment was completed in 3–5 h. According to GC and
NMR spectroscopy (see Appendix A) data, no isomerization of initial oligomers was observed during
the hydrogenation.
3.7. Viscosity characteristics
The kinematic viscosity (KV) of the obtained -olefin oligomers was determined at
temperatures of –40, 40, and 100 °С. The values KV40 and KV100 as well as the viscosity indexes (VI)
are given in Table 4. Known characteristics of -olefin oligomers, produced by acid catalysis, are
given in the same table for comparison.
Analysis of the obtained data allowed us to make several important conclusions (Table 4).
1-Hexene oligomers. Tetramer H4H and pentameter H5H as well as the dimer of dimer of
hexene H22H represented low-viscosity oils (KV100 2.1, 3.8, and 2.72 cSt, respectively). However,
these oligomers were characterized by low viscosity indexes.
15

1-Octene oligomers. The oligomers of 1-octene prepared by zirconocene-catalyzed processes
had medium viscosity and outperformed octene oligomers obtained in the presence of BF3–ROH in
terms of viscosity indexes, while possessing the same low-temperature kinematic viscosity.
1-Decene oligomers. The decene oligomers synthesized by us, as expected, significantly
outperformed electrophilic oligomers obtained in the presence of BF3–ROH in terms of viscosity
ratings and can be considered as base stocks for modern PAOs.
Dimers of -olefin dimers. Given equal molecular mass, dimers of -olefin dimers had slightly
lower viscosity than coordination -olefin oligomers. The tentative application of these compounds as
low-temperature single-component oil base stocks [23] is limited by their high KV–40 values.
4. Conclusions
We have studied the catalytic activity of zirconocenes activated by minimal excesses of TIBA
and MMAO-12, in oligomerization of 1-hexene (H), 1-octene (O), and 1-decene (D). Using of low
Al/Zr ratios leads to reduction of n-alkane formation caused by hydroalumination processes. As a
result, we found effective catalysts to produce the oligomer mixtures with oligomerization grades Pn =
2–5 with yields of up to 90% with a lightweight oligomer fraction (Pn 3–5) of up to 50%.
Conducting oligomerization experiments in the 2–5 mol scale, we obtained and separated as
individual compounds the oligomers, corresponding to Pn = 2–5. -Olefin trimers (H3, O3, and D3),
tetramers (H4, O4, and D4), and pentamers (H5 and O5) have been characterized as individual
compounds for the first time. “Dimers of dimers” of -olefins H22, O22, and D22 were synthesized
by cationic dimerization of vinylidene dimers H2, O2, and D2, and characterized as structurally
homogeneous compounds. All newly obtained -olefin oligomers were hydrogenated under mild
conditions with the hydrogenation products characterized as individual compounds.
In order to match the viscosity ratings of hydrogenated -olefin oligomers with the ratings of
oligomeric mixtures obtained by conventional electrophilic catalysis we determined the pour points
and kinematic viscosities at –40, 40, and 100 °C and also calculated the viscosity indexes for all the
oligomers obtained (Table 4, Fig. 3). We determined that the hydrogenated coordination oligomers of
1-hexene are characterized by quite low VI values, significantly lower than those of the hexene
products obtained under conditions of “soft” electrophilic catalysis (BF3/ROH), and as a result cannot
be used as oil base stocks. On the contrary, hydrogenated coordination oligomers of 1-decene
significantly outperform the products of 1-decene cationic oligomerization which are base stocks of
high-quality PAOs.
Despite the favorable properties of 1-decene-based PAOs, however, their production cost is
high and the search continues for cheaper raw materials that can provide oil base stocks with similar
16

properties to those of base stocks made from 1-decene. It is important that the octene-based PAOs
obtained by coordination oligomerization show only slightly inferior main characteristics than those of
the commercial 1-decene-derived products synthesized by electrophilic catalysis (Fig. 3). Recent
progress in the development of selective methods of ethylene tetramerization [58–63] can make 1-
octene more readily available than 1-decene as the raw material in the near future. This allows us to
view 1-octene-based products as available alternatives to conventional decene PAOs.
Acknowledgment
The authors are thankful to Russian Science Foundation, Grant No. 15-13-00053, for financial support.
17

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[60] Y. Shaikh, K. Albahily, M. Sutcliffe, V. Fomitcheva, S. Gambarotta, I. Korobkov, R. Duchateau,
Angew. Chem., Int. Ed. 51 (2012) 1366–1369.
[61] S. Kuhlmann, C., Paetz C. Hägele, K. Blann, R. Walsh, J.T. Dixon, J. Scholz, M. Haumann, P.
Wasserscheid, J. Catal. 262 (2009) 83–91.
[62] D.S. McGuinness, Chem. Rev. 111 (2011) 2321–2341.
[63] K.A. Alferov, G.P. Belov, Y. Meng, Appl. Catal. A: General 542 (2017) 71-124.
20

Fig 1 Main structural types of hydrocarbons – components of oils
Fig 2 Vinyl proton peaks in reaction mixtures of 1-decene oligomerization in the presence of
zirconocenes 2, 3, and 14 (4 h, 100 °С).
21

Fig 3 Viscosity characteristics of 1-decene (green), 1-octene (red), and 1-hexene (blue) oligomers
obtained by coordination polymerization (this work) and in the presence of BF3–ROH [3]. D3*:
decene trimer obtained using [EBTHI]ZrCl2–TIBA–perfluoroborate [15]. The range of technical
requirements for promising PAOs was limited to the segment corresponding to VI = 100 for KV100 = 2
and VI = 120 for KV100 = 6.
22

Scheme 1 Cationic (a) and coordination (b) -olefin oligomerization. Dimerization of -olefin
vinylidene dimers (c)
Scheme 2 Zirconocenes studied in oligomerization of -olefins
Scheme 3 Alternative pathways of chain release in -olefin oligomerization
23

Scheme 4. Preparation of zirconocene 14.
24

Table 1 Oligomerization of α-olefins during catalysis with 1 and 2 at AlMAO/Zr = 200, AlTIBA/Zr = 100.
Reaction time: 4 h. Activator: MMAO-12
% wt. of components, approximated for 100%
conversion
GC Data, % wt. of
Conv. oligomers in the reaction
Run Cat olefin, T, °C value after mixture after 4 h, for Pn:
α-
α
Dimer/
lower
olig.
% Pn 3-5 % 2-
% Pn 2-5
oligomers dimer
%
%
1)
solv.
4 h, %
(lower)
alkenes/
residue
2
3
4
5
oligomers alkanes
1
2
3
H
O
D
60
60
60
0.25 99
0.30 99
0.33 99
44.8 13.0 4.4 2.7 65.5
45.2 15.0 6.0 4.4 71.3
42.3 21.2 9.2 n.d. 73.42)
45.2
44.8
42.7
61.6
21.9
26.0
28.6
26.4
14.8
30.7
32.0
30.0
20.2
25.6
30.73)
38.4
31.7
37.1
32.9
38.1
30.0
41.4
39.32)
41.32)
1.2/~122)
1.2/12.8
0.8/14.1
n.d.
~21
2.24
1.78
1
2
14.7
11.74) 1.39
45)
55)
6
H+C7 70
H+C7 70
H+C7 70
H+C7 70
H+C7 60
0.39 72.9 44.9 15.4 8.1 3.3 100
n.d.
32.8
22.6
24.2
22.3
41
1.60
0.69
0.70
0.87
0.69
0.49
0.74
0.49 91
0.48 96
0.46 99
0.63 97
0.62 98
0.54 98
0.49 98
0.60 94
19.9 11.6 7.6 9.6 53.6
25.0 14.8 9.4 11.4 63.2
28.3 15.4 9.4 7.8 61.5
25.6 12.7 10.7 10.6 64.5
14.5 11.0 9.1 9.5 45.1
30.1 16.6 12.0 12.0 72.2
31.3 23.3 15.2 n.d. 71.33)
28.2 21.6 17.2 n.d. 71.43)
1.6/~122)
1.2/~132)
0.3/~142)
1.2/~122)
1.9/~122)
1.8/10.4
0.8/8.2
76)
8
9
H
60
10
11
12
O+C7 60
D+C7 60
D+C7 70
15.6
19.84) 0.81
20.64) 0.73
1.4/6.6
1) α = tetramer/trimer molar ratio, characteristics of Flory-Schulz distribution shape
2) Determining the exact concentration of n-hexane in reaction mixture was difficult due to the use of TIBA solution in
hexane.
3)
Not counting decene pentameter due to low resolution of C50H100 by GC.
4) Including decene pentamer
5) MAO used instead of MMAO-12
6) 1 bar of hydrogen
Table 2 Zirconocene-catalyzed oligomerization of 1-hexene at AlMMAO-12/Zr = 10. Reaction time: 4 h,
60 °С, bulk.
% wt. of components, approximated for 100%
GC Data, % wt. of oligomers in the
conversion
Conv. α
Dimer/
lower
olig.
reaction mixture after 4 h, for Pn:
Run Cat. after value
% Pn 3-5 % 2-
% Pn 2-5
oligomers dimer
%
%
1)
4 h, %
(lower)
alkenes/
residue
2
3
4
5
oligomers alkanes
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
97
85
98
16
92
72
<2
89
95
0.11 79.7
0.55 29.8
0.41 40.3
0.44 6.4
0.38 32.4
0.81 5.4
10.1
12.7
14.2
2.4
16.0
7.1
1.5
9.3
7.7
1.4
8.1
7.7
-
0.3
8.3
6.9
1.0
4.2
9.8
-
94.0
70.8
70.4
70.0
66.0
41.7
-
81.8
35.1
41.1
40.0
35.2
7.5
12.2
35.7
29.3
30.1
30.8
34.2
-
3.4/~22) ~12)
6.70
0.98
1.40
1.33
1.14
0.22
-
7.2/~22) ~202)
2.4/~32) ~242)
8.8/~22) ~192)
1.2/~22) ~312)
1.4/~22) ~552)
-
-
-
-
-
-
Polymer (isotactic); Mn = 3 730, Ð = 3.76
0.50 21.3
0.52 19.2
13.7
12.6
9.2
8.8
7.8
7.6
54.7
51.3
22.4
20.4
32.3
30.9
4.6/~22) ~392)
6.4/~22) ~402)
0.69
0.66
10 10 94
11 11 88
12 12 94
13 13 92
Polymer (atactic); Mn = 2 140, ÐM = 1.82
Polymer (isotactic); Mn = 9 120, ÐM = 1.79
Polymer (isotactic); Mn = 3 110, ÐM = 2.73
1) α = tetramer/trimer molar ratio, characteristics of Flory-Schulz distribution shape
2) Determining exact n-hexane concentration in reaction mixture was difficult due to the use of TIBA solution in hexane as
a scavenger.
25

Table 3. -olefin oligomerization optimization experiments with zirconocenes 2, 3 and 14.
GC Data, % wt. of oligomers in
% Pn 3-5
(lower)
oligomers,
approx.
35.7
α-
Run Cat. olefin,
solv.
Conv.
after
4 h, %
% Pn 2-5
oligomers,
approx
%
% 2-
%
Dimer/
the reaction mixture after 4 h,
for Pn:
T,
°C
α
H2
dimer,
approx.
alkenes/
alkanes
residue lower
approx. olig.
value1)
2
3
4
5
1
2
3
4
5
6
H
H
O
D
D
H
H+C7
H+C7
O
D
D
H
O
O
O
O+C7
O
D
60
60
60
60
100
60
60
60
60
60
100
60
60
80
100
100
120
100
60
100
120
100
100
120
100
-
85
99
83
72
69
98
96
98
97
96
86
100
100
100
100
97
0.55
0.39
0.52
0.58
0.40
0.41
0.42
0.53
0.47
0.62
0.22
0.63
0.47
0.36
0.49
0.43
0.32
0.51
0.66
0.32
0.30
0.38
0.28
0.28
0.33
29.8
50.1
33.0
27.5
27.9
40.3
40.3
33.7
35.2
29.0
35.6
9.3
23.3
27.5
37.0
45.5
44.0
40.5
13.4
47.4
51.0
41.0
44.8
50.0
35.6
12.7
16.3
13.1
14.3
16.2
14.2
14.2
14.2
14.6
17.4
19.5
6.4
12.8
14.3
16.2
19.4
19.0
25.1
8.6
9.3
8.5
9.0
11.0
8.7
7.7
8.0
10.1
9.2
14.3
5.6
5.4
8.0
6.8
8.9
11.0
8.0
17.2
7.6
9.9
8.6
9.6
11.0
9.0
9.5
8.3
5.5
10.9
n.d.
n.d.
6.9
7.8
9.8
7.4
n.d.
n.d.
5.1
8.9
5.2
8.6
8.2
4.9
n.d.
7.4
6.9
5.0
7.2
n.d.
n.d.
n.d.
70.8
81.2
76.6
73.33)
76.43)
70.4
73.2
68.4
68.5
63.33)
75.23)
26.2
52.9
53.8
60.7
86.7
76.0
89.13)
36.9
87.1
86.4
76.9
85.2
83.8
77.4
35.1
50.6
39.8
38.2
40.4
41.1
42.0
34.0
36.3
30.2
41.4
9.3
23.3
27.5
37.0
47.0
44.0
43.5
13.4
47.4
51.0
41.0
44.83)
50.53)
41.43)
7.2/~22)
0.3/~82)
7.0/2.6
7.2/2.4
11.2/3.1
2.4/~31)
2.7/~31)
2.4/~21)
2.0/0.6
1.4/0.6
5.6/0.4
0.8/~12)
0.9/1.1
0.9/1.1
1.1/1.2
2.2/1.8
1.4/1.6
2.1/1.4
0.4/~62)
0.8/4.1
1.6/2.5
0.3/5.1
0.3/8.2
0.3/6.2
0.3/6.1
20.02)
10.52)
10.8
17.14)
9.74)
24.21)
21.11)
27.51)
28.9
34.74)
18.84)
72.1
45.1
44.3
27.0
9.3
21.0
7.4
56.7
8.0
9.5
17.7
6.34)
9.84)
16.24)
0.98
1.65
1.00
1.09
1.12
1.40
1.35
0.99
1.13
0.91
1.22
0.55
0.79
1.05
1.10
1.18
1.38
0.96
0.57
1.20
1.44
1.14
1.11
1.52
1.15
1 bar
30.7
2
3
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
39.8
35.03)
36.13)
29.3
7
31.2
34.4
85)
9
32.2
106)
11
12
13
14
15
16
17
18
19
20
21
225)
23
24
255)
33.13)
33.83)
16.9
29.6
26.3
33.6
39.8
100
93
32.0
45.53)
23.5
14
1 bar
1 bar
1 bar
1 bar
1 bar
1 bar
1 bar
H
O
O
O
D
D
D
100
100
100
100
99
22.9
21.7
19.1
29.4
23.9
21.5
39.7
35.4
35.9
40.53)
33.33)
36.03)
99
86
1) α = tetramer/trimer molar ratio, characteristics of Flory-Schulz distribution shape
2) Determining the concentration of n-hexane in reaction mixture is made difficult due to use of TIBA solution in hexane.
3) Not counting decene pentameter (low resolution of C50H100 by GC)
4) Including decene pentamer
5) Preparatory experiment, 5 mol. of monomer, 1 mmol (0.02%) of zirconocene.
6) Preparatory experiment, 5 mol of monomer, 1 mmol (0.02%) of zirconocene, 8 h.
For 5) and 6) the yield was determined by weighing and GC analysis of fractions rectified in vacuo (dimer, oligomers, remainder)
26

Table 4 Viscosity characteristics of -olefin oligomers.
No. of
C
atoms
d at
–40 °C, 20 °C,
g/mL g/mL
0.7920 0.7412
d at
KV–40
sSt
,
KV40,
sSt
KV100
sSt
,
Oligomer
VI
PP, °C
–73
H2H
O2
O2H
H3
12
16
16
18
18
18
20
20
24
24
24
24
24
24
24
30
30
30
30
30
30
30
32
32
32
32
32
40
40
40
40
40
30
40
40
9.00
–
53.1
1.28
2.6
2.82
3.12
3.57
3.8
4.55
5.30
7.55
8.93
9.8
12.4
6.5
7.56
8.0
17.55 3.6
19.2
18.1
–
–
–
–
–
–
–
–
0.8190 0.7699
0.8355 0.7878
0.8355 0.7878
–43
H3H
167.2
165
–
–
–
14
14
62
46
94
27
114
92
92
76
76
–94
< –55
H3H (BF3 catalyst) [3]
D2
D2H
H4
1.4
1.7
–
2.10
2.28
2.6
2.72
2.06
2.20
2.3
0.7829
0.8425 0.7957
0.8475 0.8016
0.8420 0.7955
–7
H4H
1335
1780
3030
–79
–71
H4H (BF3 catalyst) [3]
H22H
O3
O3H
O3H (BF3 catalyst) [3]
H5
H5H
H5H (BF3 catalyst) [3]
D3
D3H
D3H [EBTHI]Zr - borate [15]
D3H (BF3 catalyst) [3]
O4
O4H
552.1
580
–86
< –55
6798
7850
3.8
3.8
0.8465 0.8007
0.8515 0.8058
–67
96
14.61 3.65
15.05 3.70
13.5
15.6
140
137
128
122
125
115
106
130
119
132
129
124
142
145
141
150
136
1897
2070
–75
3.39
3.7
< –55
13.94 3.44
3135
4750
18.4
20.0
28.1
29.4
32.9
36.2
30.9
31.3
34.5
29.0
4.0
4.1
5.4
5.4
6.05
6.4
5.6
6.03
6.52
5.7
0.8655 0.8211
–74
< –55
O4H (BF3 catalyst) [3]
O22
O22H
O5
6374
0.8755 0.8320
0.8750 0.8317
–68
–68
O5H
11651
10225
O5H (BF3 catalyst) [3]
D4
D4H
D4H (BF3 catalyst) [3]
D22
D22H
8631
7475
0.8755 0.8322
–66
–52
29.43 5.90
42.0 7.25
0.8780 0.8346
0.8346 0.7920
15615
27