Alternatives for Conventional Alkane Solvents

Article abstract of DOI:10.1021/jacs.6b07967

The studies described in this paper show that hydrocarbon oligomers are alternatives for low molecular weight alkane solvents. These oligomeric solvents are nontoxic, nonvolatile, and recyclable alternatives to heptane in thermomorphic solvent mixtures th

Full text of DOI:10.1021/jacs.6b07967

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Article
Alternatives for Conventional Alkane Solvents
Mary L. Harrell, Thomas J. Malinski, Coralys Torres López,
Kimberly Gonzalez, Jakkrit Suriboot, and David E Bergbreiter
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Alternatives for Conventional Alkane Solvents
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Mary L. Harrell, Thomas Malinski, Coralys Torres-López, Kimberly Gonzalez, Jakkrit Suriboot,
and David E. Bergbreiter*
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Department of Chemistry, Texas A&M University, College Station, TX 77842-3012
Green chemistry, solvents, polymers, oligomers, recyclable, sustainable.
ABSTRACT: The studies described in this paper show that hydrocarbon oligomers are alternatives for low molecular
weight alkane solvents. These oligomeric solvents are nontoxic, nonvolatile, and recyclable alternatives to heptane in
thermomorphic solvent mixtures that use a polar solvent such as methanol, aqueous ethanol, or DMF or in biphasic mix-
tures that use acetonitrile. Regardless of which polar solvent is used, hydrocarbon oligomers like poly(α-olefin)s (PAOs)
exhibit very low leaching into the polar phase. UV-Visible spectroscopy studies show that these solvents have the solubili-
ty properties of heptane. For example, PAOs dissolve heptane soluble dyes and quantitatively separate them from polar
phases in thermomorphic solvent mixtures. PAOs either as pure solvents or as additives in heptane act as antileaching
agents, decreasing the already low leaching of such dyes into a polar phase in heptane/polar solvent mixtures. These oli-
gomeric hydrocarbon solvents were also compared to heptane in studies of azo dye isomerization. The results show that
thermal isomerization of an azo dye occurs at the same rate in heptane and a PAO. Further studies of carboxylic acid
promoted dye isomerization in heptane and a PAO show that low molecular weight and oligomeric carboxylic acids are
kinetically equivalent at accelerating this isomerization. The results suggest that these and other hydrocarbon oligomers
behave as solvents like their low molecular weight nonpolar hydrocarbon solvents and that they can be substituted suc-
cessfully
for
conventional
solvents
like
heptane.
Introduction
hydrocarbons and in heptane also occur at the same rate.
Specifically, thermal or acid-promoted azo dye isomeriza-
tions in heptane and in an oligomeric hydrocarbon sol-
vent occur at the same rate. However, oligomeric hydro-
carbon solvents have some significant advantages over
their low molecular weight alkane analogs. First, they are
nonvolatile and relatively nontoxic.4,5 Second, unlike
lower molecular weight alkanes, they do not significantly
contaminate polar phases when used in conjunction with
polar solvents. This is true when the nonpolar and polar
solvents are separated by a liquid/liquid separation after
heating an initial biphasic mixture to form single phase
and then cooling to reform the biphasic mixture (a ther-
momorphic process).6 Finally, when used under ther-
momorphic conditions with soluble hydrocarbon oligo-
mer-tagged dyes that we have shown are surrogates for
phase-anchored catalysts,7 they lower leaching of the hy-
drocarbon phase anchored dye into the polar phase – a
potential advantage in homogeneous catalysis with hy-
drocarbon phase anchored catalysts.
Solvents are a ubiquitous part of many if not most chemi-
cal processes. They serve useful roles in mitigating ex-
otherms, in providing a suitable milieu for reactions, and
in controlling relative concentrations of reacting species.
They are essentially required in homogeneous catalysis.
However, solvents pose environmental issues and intro-
duce additional costs in any system. Ideally, they should
be easily recyclable by a simple physical process. In prac-
tice, they often have to be recovered by energy intensive
processes like distillation. If they are not recovered, they
are disposed of as chemical waste. Lists of greener and
more environmentally benign solvents that include new
types of solvents as well as more benign and more sus-
tainable organic solvents exist.1-3 However, it is difficult if
not impossible to design solvents that have all the desired
criteria for a green solvent.3 For example, sustainable
bioderived organic solvents are often still volatile and as
such can introduce unwanted pollutants into the envi-
ronment.
The volatility, toxicity, and sustainability issues associated
with conventional solvents have spawned the develop-
ment of a variety of alternative and potentially more envi-
ronmentally benign solvents or solvent systems in recent
years.1-3 These include ionic liquids,8 supercritical fluids
like scCO2,9 water (often with surfactants),10 deep eutectic
solvents,11 fluorous solvents,12 and polymers.13. Each of
these alternatives has significant advantages as well as
This paper describes a series of studies of liquid oligomer-
ic hydrocarbons that can serve as substitutes for conven-
tional alkane hydrocarbon solvents. These alternative
solvents are greener than typical hydrocarbon solvents
such as hexane or heptane. As solvents, they are as good
as or as bad as these conventional alkane solvents. They
readily dissolve alkane soluble species and behave as non-
solvents toward polar substrates. Reactions in oligomeric
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some possible disadvantages. Many of these alternatives
have been used in industrial scale processes.
A disadvantage of these procedures is that they use al-
kanes like heptane as the nonpolar phase. While much of
this solvent can be recovered and reused, it has some un-
desirable characteristics due to its volatility. Moreover, a
portion of it cannot be readily recovered because it parti-
tions into the polar phase and is lost.
Ionic liquids provide an excellent medium for polar reac-
tions. They can be costly but have the advantages of non-
volatility and separability by simple gravity separations.
Their structures are easily varied through synthesis, af-
fording additional versatility and tunability.8,14 Supercriti-
cal fluids like scCO2 are industrially used alternative sol-
vents and have been used in applications that range from
catalysis,9 in solvent intensive processes like extrac-
tions,15,16 and even in commercial dry cleaning.17 While
scCO2 requires a pressurized apparatus and depressuriza-
tion/pressurization cycles in use and recycling, CO2 has
the advantage of being an abundant resource and is both
recyclable and sustainable. Water is even more common
as a solvent. It can be recycled and is sustainable. While
it is not always the most suitable solvent for organic
chemistry, the use of surfactants addresses many of these
concerns.10 Its solvent properties are also tunable by the
addition of appropriate cosolvents.18 Large scale transi-
tion metal catalyzed reactions using water under biphasic
conditions too can be effective as seen in aqueous bipha-
sic catalysis.19 Less polar milieu have also received atten-
tion. For example, fluorous solvents and fluorous systems
have received significant attention in part because the
bulk of these solvents can be recovered in biphasic sepa-
rations. These simple gravity-based separations for
fluorous solvents and the high solubility of many gases in
fluorous solvents make them attractive candidates for
catalytic systems.12,20 Lists of solvents that more closely
resemble conventional organic solvents but that can be
derived from non-petroleum sources or that are relatively
non-hazardous have also been published.2 These solvents
are in many cases derived from biobased resources.
While such solvents often have lower toxicity than a con-
ventional solvent they replace, these solvents still have
the volatility issues common to other low molecular
weight organic materials. Finally, there is precedent for
the use of polymeric solvents. The most commonly ex-
ample, poly(ethylene glycol) (PEG),13 addresses the vola-
tility issues associated with low molecular weight sol-
vents. PEG has the attractive feature that it resembles
common polar solvents. However, separation of polar
products from such solvents is not always simple and in
many cases involves use of another solvent.
Some of our prior work suggested that hydrocarbon oli-
gomers could be a sustainable alternative to a conven-
tional alkane solvent like heptane. One example was our
observation that a commercially available low melting
point polyethylene wax26 could recover catalysts in a non-
volatile and nontoxic solid paraffin-like matrix that can
both protects a catalyst from adventitious decomposition
by polar reagents and effects a simple filtration based
separation.27-32 We subsequently showed that these wax-
es can be used as cosolvents,29-32 reducing metal leaching
in processes others described as ‘commercially viable’.33
These PEOlig cosolvents also appeared to decrease leaching
of homogeneous catalysts.29-31
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We more recently reported that the ‘antileaching’ effect
seen with polyethylene oligomer cosolvents is also seen
when liquid hydrocarbon oligomers are added to a ther-
momorphic solvent mixture. Those studies showed re-
duced leaching of either an polyisobutylene (PIB)-bound
azo dye or Ru(bpy)3Cl2 complex into a polar phase when a
polyolefin oligomer was added to thermomorphic mix-
tures of heptane and polar cosolvents.34
Prior work on alternatives to alkane solvents has most
commonly focused on bioderived solvents that mimic
existing alkanes in terms of their molecular weight and
volatility. Hydrogenated terpenes are a common example
of such alternatives.35 While these solvents are derived
from sustainable sources and have useful properties, our
preliminary work described above suggested to us that
oligomeric hydrocarbons too could be useful greener al-
ternatives to low molecular weight alkane solvents.
Here we describe detailed studies of this possibility, stud-
ying polypropylene (PP) oligomers, PIB oligomers, and
readily available poly(α-olefin)s (PAOs) as solvents and
cosolvents. Our results show that inexpensive polyolefin
oligomers can indeed be used like heptane as solvents.
These studies show that polyolefin oligomers are as func-
tional as heptane as solvents and that they do not them-
selves appreciably leach into a polar phase. These studies
also show that these oligomeric hydrocarbon solvents
themselves or as additives reduce leaching of PIB-bound
azo dyes that serve as surrogates of PIB-bound ligands,
catalysts, and reagents. Finally, studies of both thermal
and acid promoted dye isomerization show that reactions
in these oligomeric solvents mirror reactions in heptane.
Our recent work has focused on designing soluble poly-
mer-bound catalysts that can be used in a fully miscible
solvent mixture yet separated in a biphasic separation
step after a homogeneous catalytic reaction.21 This work
used inexpensive oligomeric phase tags to derived from
heptane soluble oligomers or polymers. With such phase
tags, it is possible to effect a biphasic recovery of reagents
or catalysts that have high alkane phase selective solubili-
ty if they have a stable resting state or to separate catalyst
and ligand residues from polar phase soluble products.22-25
Results and Discussion
In considering alternatives to simple alkane solvents we
had several criteria. First, we wanted materials with low
volatility. That criterion can be met simply by using
higher minimal vapor pressure. Second, we wanted to use
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liquid molecular weight hydrocarbon oligomers that have
now biobased, ethylene derived 1-alkenes could be de-
molecular weight hydrocarbon oligomers that have hy-
drocarbon oligomers because we wanted to effect separa-
tions using a simple gravity separation. We have previ-
ously shown that polyethylene oligomers (PEOlig) with
molecular weights of ca. 500-2000 can function as cosol-
vents or solvents.29-32 However, these materials require
separation by filtration, a process that can be problematic
when fine particles form.31 Third, if an oligomeric hydro-
carbon were to be useful, it should have solvent proper-
ties like heptane and dissolve the same things heptane
does and does not. Fourth, while an oligomeric hydro-
carbon cosolvent is likely to have higher viscosity than
heptane, its viscosity should be modest or manageable
when used as part of a solvent mixture under the reaction
conditions. Fifth, if an oligomeric hydrocarbon alterna-
tive solvent were nonvolatile, it could not be removed
from a product phase by evaporation as is the case with
heptane. Thus, contamination of a polar phase has to be
minimal to avoid the need for more purifications of prod-
ucts that might be in that polar phase. Sixth, an alterna-
tive hydrocarbon solvent or cosolvent should mimic hep-
tane in terms of creating an appropriate reaction envi-
ronment. Finally, an alternative to a conventional alkane
ideally would be nontoxic, recyclable, inexpensive, biode-
gradable, and sustainable. As we how below, hydrocar-
bon oligomers meet many or most of these goals as alter-
natives to conventional alkane solvents.
rived from sustainable resources if biobased ethylene be-
came competitive with fossil resource derived ethylene.
Alternative biobased routes to 1-alkene precursors also
exist. For example, a metathesis route to 1-alkenes has
been described by Elevance45 who are already advertising
their bioderived 1-alkenes. Other catalytic processes lead-
ing to 1-alkenes from bioresources have also been de-
scribed.46 Finally, naturally occurring C8-C20 alcohols
could form the alkene precursors of these hydrocarbon
oligomers.
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PAOs have advantages over alkanes as described above
that make them greener and potentially sustainable sol-
vents. However, like all alternative solvents, they have
some potential disadvantages too. Specifically, their lack
of bioavailability, especially for the larger PAOs described
below, limits their biodegradability.38,47 While lower smo-
lecular weight PAOs are biodegradable, the higher mo-
lecular weight PAOs degrade more slowly and could ac-
cumulate in the environment though they reportedly do
not bioaccumulate in aquatic organisms.38 Second they
are more viscous than conventional alkanes like hexane or
heptane and most conventional solvents. The viscosity of
what we suggest is a preferred PAO solvent in the studies
below is 10 CSt at 100 °C, a viscosity like that of olive oil at
95 °c (9.5 cSt).48 Third, they are flammable. However, the
flash point of PAOs is >150 °C while heptane has a flash
point of -4 °C.37 Finally, PAOs without the addition of
another cosolvent are simply alkanes. Thus, PAOs will
not be any better than hexane or heptane as pure solvents
for even modestly polar organic molecules.
The main focus of this work is a particular class of oligo-
meric hydrocarbons – poly(α-olefin)s (PAOs).36 These
materials generally meet the criteria above. They are also
inexpensive and commercially available.37,38 Conventional
alkanes like hexane and heptane have inhalation toxici-
ty.39,40 Hexane in particular is not recommended as a sol-
vent due to its volatility and neurotoxicity.39 PAOs in
contrast are nonvolatile and do not have inhalation toxici-
ty due to their low vapor pressure. They also have low
oral toxicity.4,5 Finally, unlike alkanes PAOs are physically
recyclable by a gravity separation as discussed below.
Our studies focused on three PAOs (cf. Table 1) with in-
termediate molecular weight on a longer list of PAOs that
are available from Exxon Mobil.37 Similar PAOs are avail-
able from other sources.38 These inexpensive commercial-
ly available compounds come in a variety of molecular
weights varying from Mn values of 280 Da to 4100 Da with
dispersity values that range from 1.12 to 1.82 Ð. These
materials have a range of viscosities that vary from 2 to
156 cSt at 100 °C. These viscosities will increase on cool-
ing but we here use the reported 100 °C viscosity values as
they are most relevant to processes that might involve
heated thermomorphic solvent mixtures. The viscosity of
olive oil is comparable to that of PAO 1 at ca. 100 °C. De-
pending on the specific PAO and whether the PAO is
used with or without a cosolvent, viscosities of some
PAOs as pure solvents or most PAO-cosolvent mixtures
are manageable. Three of these PAOs 1-3 were used in
the following studies. PAO 3 which has a molecular
weight of 2505 Da has too high a viscosity to make it a
useful solvent for ambient temperature reactions. How-
ever, it could be useful as a cosolvent. PAO 1 with a mo-
lecular weight of 687 Da has a viscosity similar to that of
olive oil. PAO 2 of molecular weight 1758 Da has an in-
termediate viscosity. All of these PAOs were colorless
PAOs are prepared on a large scale from 1-alkenes most
often for use as lubricants. They are inexpensive. Their
synthesis is carried out with acid or with transition metal
catalyzed oligomerization reactions. Complex mixtures of
constitutional isomers form, even in a dimerization.41
Nonetheless, various PAOs with characteristic viscosities,
average molecular weights, boiling points, and modest
dispersity are available.
The linear alpha olefins or 1-alkene precursors of PAOs
are most often derived from ethylene via processes like
the Aufbau or SHOP processes.42,43. The source of eth-
ylene is determined by economics. Currently ethylene is
derived from non-renewable resources in the U.S. How-
ever, the economics of ethylene production are such that
ethylene derived from bioresources can be competitive in
cost.44 Thus, while ethylene derived 1-alkenes are not
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liquids. They are all fully hydrogenated and in H NMR
alcohols with temperature dependent solubility behavior
that was similar to that of heptane. However, an initial
concern was that hydrocarbon oligomers, like heptane,
could contaminate a polar phase.
spectroscopy, their signals all occur between 0.8 and 1.4 δ.
Table 1. Poly(α-olefin) (PAO) Alternative Solvents
7
8
9
Molecular
Weight (Mn)
Dispersity
Index
Viscosity
at 100 ⁰C
(cSt)
Density
(g/mL)
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687 (1)
1758 (2)
2505 (3)
1.12
1.35
1.47
10
40
65
0.84
0.85
0.85
Our studies also included two other polyolefin oligomers
as solvents or cosolvents that do not meet all our criteria
but that have been used in prior work. One example is a
propylene-hexene random copolymer 4 that is like a cata-
lyst support others have used. This polymer contains
alkene end groups derived from either propylene or hex-
ene units.49 We obtained 4 as a 800 Da material from
Baker-Hughes. It has a 25 °C viscosity that is qualitatively
similar to that of 1. Oligomer 4 has the disadvantage of
containing a terminal alkene group and it is not commer-
cially available so its use in our studies was limited. Poly-
isobutylene (PIB) 5 both with a terminal double bond and
in a hydrogenated form is available too. While we have
used polyisobutylene (PIB) as a ligand and while PIB de-
rivatives are commercially available, nonvolatile, and
nontoxic,50 vinyl-terminated PIB with molecular weights
of 1000 and 2300 Da have viscosities of 190 and 1500 cSt at
100 °C, viscosities that are too high for PIB to be used as a
pure solvent and, in the case of PIB2300, too high to be
used as a significant component even in solvent mixtures.
Scheme 1. Synthesis of Polyisobutylene (PIB)-bound Azo
Dyes 6-8
Table 2. Solubility of Oligomeric Hydrocarbon Alter-
native Solvents with Conventional Solvents
Solvent
heptane
Oligomer
1, 2, 3, 4, or 5
1, 2, 3, 4, or 5
1, 2, 3, 4, or 5
1, 2, 3, 4, or 5
1, 2, 3, or 4
Solubility
Ya
toluene
Ya
dichloromethane
tetrahydrofuran
methanol
ethanol
Ya
Ya
thermomorphicb
thermomorphicb
thermomorphicb
thermomorphicb
N
PAOs 1-3, the PP oligomer 4, and PIB1000 (5) were first
examined as solvents for PIB-bound azo dyes that were
synthesized from PIB oligomers containing a terminal
2,6-dimethylaniline group (Scheme 1).51 These initial
studies used dyes 6-8. All three PAOs 1-3, the PP oligomer
4, and PIB 5 readily dissolved these dyes.
1, 2, 3, or 4
isopropanol
DMF
1, 2, 3, or 4
1, 2, 3, or 4
Next we examined the use of these PAOs 1-3, the PP oli-
gomer 4, and PIB1000 5 with other cosolvents (Table 2).
The PAOs, the PP, and PIB1000 5 were fully soluble in al-
kanes, toluene, dichloromethane, THF, and toluene when
a 1/1 (w/w) mixture of the PAO and solvent was prepared.
A 1/1 (w/w) mixture of the PAO and methanol, ethanol,
isopropanol, DMF, acetonitrile, and water formed bipha-
sic mixtures at room temperature. Oligomers 1 – 4 all
showed varying levels of thermomorphic behavior with
acetonitrile
water
1, 2, 3, 4, or 5
1, 2, 3, 4, or 5
N
a1 g of the PAO visually dissolved in 1 g of the low molecu-
lar weight solvent at room temperature. b 1 g of the PAO
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mixed with 1 g of the low molecular weight solvent
formed a homogeneous solution on heating to ca. 100 °C.
2
3
MeCN
MeCN
0.4
0.4
0.01d
0.01d
This is a concern because if there were significant con-
tamination, such hydrocarbon oligomer contaminants
would have to be removed from products by extractions
with
a A biphasic mixture of 3 g of the PAO and 3 g of the polar
solvent was heated to form a single phase and then cooled to
reform a biphasic mixture. Then a drop of the polar solvent
1
alkanes or by chromatography. Such additional purifica-
tion steps would be a significant liability for an alkane
solvent substitute. To test this issue, we used a version of
solution was removed for H NMR spectroscopic analysis
using CDCl3 as the solvent. These analyses were carried out
at ambient temperature with the exception of the methanol
samples which required analysis at -30 °C to shift the metha-
nol -OH peak away from the PAO peak being analyzed. bThe
mg of the PAO in the polar phase was calculated by setting
the integral for the formyl H of DMF or the methyl singlets of
MeOH or CH3CN to 100 and comparing 1.08% of this integral
to the integration of any detectable PAO peak between 0.8 –
1.4 δ. The supporting information also includes an estimate
of the percent PAO leaching based on a second calculation
that used the measured integrals of the 13C satellites of the
formyl H of DMF or the methyl singlets of MeOH or CH3CN
to the integration of any detectable PAO peak between 0.8 –
1.4 δ (Table S1). The PAO leaching values measured this way
were very similar or identical to the results using a base peak
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a H NMR experiment that relies on the 1.1% natural
abundance of 13C. We have previously used this technique
to assay end functionalized PEG Mn values and others
have used it to analyze trace impurities in products in
asymmetric synthesis.52 In this experiment, we examined
a 10 mL solution of a 3:2:5 (by weight) thermomorphic
mixture of cyclooctane, 4, and DMF. When this mixture
was heated to ca. 70 ⁰C, a monophasic solution formed.
On cooling to room temperature, it again became bipha-
sic. At that point, it was possible to isolate the DMF
phase and show by integrating the peaks at 8.0 δ versus
the cyclooctane peak at 1.3 δ the amount of the cyclooc-
tane that had partitioned into the denser DMF phase. In
addition to the cyclooctane singlet at 1.3 δ, two satellite
c
with an integration of 100. The percent leaching of the PAO
was based on the mg of PAO in the polar phase relative to
the 3 g of PAO in experiments that used equal weights of the
PAO and polar solvent. dAnalyses of the PAO leaching where
the PAO leaching is less than 0.03% have to be considered
estimates because of the difficulties in integrating the small
PAO signal. Estimates of leaching for this sample of PAO
used PAO that was purified by extraction with acetonitrile
for 3 d in a liquid/liquid extraction apparatus.
13
peaks due to the 1.1% C in cyclooctane appeared. When
the 1H NMR spectrum in the 0.5-2.0 δ region was carefully
examined, the cyclooctane peak and the 13C satellite peaks
were the only signals seen. No peaks attributable to the
PP oligomer 4 were seen. This corresponds to the leach-
ing of <0.1% of 4 and to the presence of less than 100 ppm
of 4 in the DMF phase. This level of contamination of 4 in
the polar phase was judged to be insignificant.
e
version of this 1H NMR experiment. In this case we relied
on the 1.1% natural abundance of C in MeOH, DMF, and
13
This promising result of little contamination of the polar
phase by 4 led us to quantitatively study the extent to
which PAO solvents 1-3 significantly contaminate a polar
phase (cf. Table 3). To carry out these studies, we used a
CH3CN and examined 6 g of a 1:1 (w:w) mixture of the
PAO and either MeOH, DMF, or CH3CN as the polar sol-
vent. When the PAO and MeOH or DMF were heated,
these solvent mixtures exhibited thermomorphic charac-
ter and a monophasic solution formed at 100 °C. On cool-
ing to room temperature, these solutions became bipha-
sic. The PAO/ CH3CN mixtures were always biphasic.
They were heated with stirring for 24 h at ca. 100 °C. We
believe this heating and stirring time was sufficient to
reach phase equilibrium for the PAO and CH3CN mixture
since experiments carried out for 48 h showed no signifi-
cant change in the % leaching of PAO 1, 2, or 3 into
CH3CN. After cooling the solvent mixtures to ambient
temperature, the polar phase was isolated and the
amount of the PAO present was determined by integrat-
ing the satellite of one of the polar solvent peaks and
comparing it to the integration of the known PAO peak.
We did not determine if cooling to room temperature
lowered this level of contamination of PAO in CH3CN.
However, since we believe that the solubility of PAO in
CH3CN does not increase on cooling, the trace amounts of
PAO in CH3CN we measure are a maximum amount of
contamination for this polar phase. Table 3 shows the
1
Table 3. H NMR Analysis of PAO Leaching into the
Polar Phase of a Polar Solvent/PAO System
Oligomer
Polar
PAO in the Polar
Phase (mg)b
PAO
leaching
(%)c,d
Solventa
1
2
3
1
MeOH
MeOH
MeOH
DMF
1.0
0.4
0.5
0.3
2.0
3.4
24.0
1.0
0.03
0.01
0.02
0.01d
0.06
0.12
2
2e
3
1
DMF
DMF
DMF
0.80
0.03d
MeCN
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mass of PAOs that leached into the various polar solvents
the PIB has a very small effect on the antileaching proper-
as well as the percent leaching of the PAOs in each polar
phase. These analyses correspond to the presence of 50-
200 ppm PAO 1 in any of these solvents. This ppm value
would decrease if the PAO were used as a cosolvent. We
speculate that the percent leaching and the ppm of PAO
in these experiments would also be further decreased by
the addition of some water or salt to the polar phase. In
any case, only a small amount of PAO leached regardless
of which polar solvent was used, showing that PAOs as
alternative solvents d0 not significantly contaminate a
polar phase in a thermomorphic or biphasic solvent mix-
ture.
ty of these cosolvents. These same studies show that
PAOs 1-3 are similar to PIB or PIB derivatives as antileach-
ing agents. We next set out to more systematically ana-
lyze the antileaching effectiveness of PAOs as solvents or
cosolvents with heptane. Methanol was again chosen as
the polar solvent and the PIB-bound azo dye 7 was used
to monitor the leaching in different systems. Similar to
the previous leaching experiment, 20 mg of the azo dye 7
was added to the nonpolar phase which had varying
amounts of heptane and
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Table 4. Leaching of a Polymer-supported Dye into
the Methanol Phase in a Methanol/Heptane Polymer
Cosolvent Thermomorphic Systema
Our prior studies of polyethylene oligomers and of liquid
polyolefin cosolvents suggested oligomeric cosolvents
could have an additional feature not seen with heptane
alone. Specifically, the several cases where we used poly-
ethylene oligomers as cosolvents as well as experiments
with azo dyes and Ru complexes suggested that oligomers
added as cosolvents could reduce hydrocarbon polymer-
bound catalyst leaching into a polar phase. This an-
tileaching effect was further explored here using the azo
dyes 6-8.
Entry
Oligomer Cosolvent
None (Heptane only)
% Leachingb
1
4.1
2.3
2
PIB-(alkene terminated) (5)
3
PIB-(CH2Br terminated)
2.5
2.5
To study this antileaching effect, we first examined the
leaching of dyes 6-8 from heptane into 10% aqueous
EtOH in a thermomorphic mixture. Addition of 3 g of
10% aqueous EtOH to a solution of 20 mg of the azo dye
in 3 g of heptane produced a biphasic solvent mixture.
Heating this produced a visually monophasic solution.
On cooling, this thermomorphic solvent mixture re-
formed a biphasic heptane/aqueous EtOH solvent mix-
ture. At this point, we analyzed the polar phase using
UV-Visible spectroscopy to determine the amount of the
leaching of the dye into the polar phase. These studies
showed that the azo dye 6 had 7.8% leaching, the azo dye
7 had 1.3% leaching and the azo dye 8 with two PIB
groups had the least leaching (0.2%).
4
PIB-(2,6-dimethylaniline
terminated)
5
PIB-(CH2OH terminated)
PIB-(cresol terminated)
2.7
2.8
6
7
8
4
2.3c
1.9d
2.6d
3.2d
PAO 1
PAO 2
PAO 3
9
We chose the azo dye 7 having an intermediate amount of
leaching in the next set of experiments to study the effect
of changing the identity of the polar solvent. We repeat-
ed the above experiments this time using the same dye 7,
varying the polar solvent identity. Using DMF, MeOH,
10% aqueous EtOH, and CH3CN as the polar solvent led to
4.7%, 4.1%, 1.3%, and 0.9% leaching respectively. While
the experiment with CH3CN as the polar phase never in-
volved formation of a homogeneous solution, the 0.9%
leaching observed was the limiting value for leaching of 7
after stirring a biphasic mixture of 7, heptane and CH3CN
for 24 h at ambient temperature.
10
a20 mg of the dye and 1 g of the polymer cosolvent were add-
ed to 3 g of heptane and 3 g of MeOH. Absorbance measure-
ments were taken after thermomorphic heating at 85 °C fol-
lowed by cooling to room temperature and allowing the
samples to sit overnight to separate cleanly. All PIB function-
alized materials were prepared from PIB alkene of molecular
weight 1000 Da and their syntheses use literature procedures
b
or are described in the supporting information. The percent
leaching was calculated by using the known concentration of
the dye in heptane and the extinction coefficient of a low
molecular weight analog of the naphthol dye in MeOH and
The experiments above suggested that the use of 7 with a
heptane/MeOH thermomorphic mixture would be the
most useful solvent mixture to probe the ‘antileaching’
effects of hydrocarbon oligomers. As shown in Table 4,
PIB or PIB additives measurably decrease leaching of dye
7. However, the identity of the terminal functionality on
c
has an estimated error of ± 0.2%. A similar experiment used
1 g of 4, 2 g of heptane, and 3 g of MeOH with a PIB2300
-
bound naphthol azo dye and had 0.5% dye leaching (refer-
ence 34). dThis experiment used 20 mg of dye, 1 g of the
PAO, 2 g of heptane, and 3 g of MeOH. Absorbance meas-
urements of the MeOH phase were taken after the mixture
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was heated at 100 °C to form a single phase and then cooled
1
1
687
687
0.5/2.5
0/3.0
0.8
0.6
to room temperature to reform a biphasic mixture The
MeOH phase was isolated at that point, centrifuged to re-
move any physical PAO contaminant and analyzed.
aThe dye 7 (20 mg) was added to a heptane/PAO or a PAO
only phase (3 g total) followed by the addition of methanol (3
g). This biphasic mixture was then heated to 100 °C. During
this heating process, the biphasic mixture became one phase.
After stirring for several minutes, the thermomorphic mix-
ture was cooled to room temperature. Centrifugation was
used to cleanly separate the phases. The MeOH phase was
then analyzed by UV-Visible spectroscopy. bThe leaching
value reported is the average of three measurements and was
calculated based on the original concentration of the dye in
heptane using an extinction coefficient for a low molecular
weight analog of the naphthol dye in MeOH. This value has
an estimated error of ± 0.2%.
5
6
7
8
PAO (3 g total). Next, 3 g of methanol was added and the
system was heated to 100 °C to form a monophasic solu-
tion. Cooling reformed a biphasic mixture where the dye
was visually in the PAO phase. After separation of the
phases, the methanol absorbance was analyzed by UV-
Visible spectroscopy to determine the amount of leaching
of the azo dye. By varying the amount of the PAO in
comparison to heptane, the viability of the PAO as an
antileaching agent was analyzed.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
The results of the experiments presented in Table 5
showed that as the amount of PAO cosolvent increased in
the nonpolar phase, the leaching of the polymer-
supported dye into methanol decreased regardless of
which molecular weight of oligomer cosolvent was used.
PAO 1 was able to reduce leaching of the dye most signifi-
cantly. When PAOs were used as replacement solvents for
heptane the leaching was reduced even more substantial-
ly. Again, PAO 1 was shown to be the oligomer solvent
with the greatest antileaching ability.
It was also important to understand whether reactions in
a PAO phase would occur as they do in heptane, the non-
polar thermomorphic solvent we have most commonly
used for catalysis studies and catalyst recycling. To ad-
dress this question, we used a PIB ester of p-methyl red 9
that we had previously used as an additive in surface
modification of polyethylene and as a probe of thermo-
morphic separations with PIB and polar solvents.53,54 The-
se studies used PAO 1 and first studied the thermal isom-
erization of 9 in heptane and in PAO 1 (Scheme 2).
Table 5. Leaching of the PIB-Bound Dye 7 into the
Methanol Phase of a Heptane/PAO/Methanol Ther-
momorphic Solvent Mixturea
Scheme 2. Light Induced Isomerization of a PIB-
bound p-Methyl Red Azo Dye 9
PAO
PAO Mn
(Da)
Heptane/
PAO Ratio
(g/g)
% Leaching of 7
into MeOHb
None
--
3.0/0
2.0/1.0
1.5/1.5
1.0/2.0
0.5/2.5
0/3.0
4.1
3.2
2.5
2.0
1.5
1.1
3
3
3
3
3
2
2
2
2
2
1
2505
2505
2505
2505
2505
1758
1758
1758
1758
1758
687
The results obtained showed that the rate of the isomeri-
zation remained constant whether heptane or PAO 1 were
used as solvents. The isomerization rate in heptane is 2.2
x 10-4 s-1 while the rate in PAO 1 is 2.3 x 10-4 s-1.
To further probe the possible difference in reaction rates
in heptane versus a PAO, we also examined acid-
promoted dye isomerizations in which selected acids were
added to study the rate of acid-promoted isomerization of
azo dye 9 in both heptane and PAO 1. As shown in Figure
1, regardless of whether the carboxylic acid used was oc-
tanoic acid, lauric acid, or a PIB-supported carboxylic
acid, the rate of isomerization of 9 increased with acid
2.0/1.0
1.5/1.5
1.0/2.0
0.5/2.5
0/3.0
2.6
1.7
1.5
1.1
0.9
1.9
1.4
1.0
2.0/1.0
1.5/1.5
1.0/2.0
1
687
1
687
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the polar solvent, 20 mg of the dye 7, and 3 g of the PAO sol-
vent. After thermomorphic heating, the solutions were
concentration.
The
cooled to ambient temperature and UV-Visible spectroscopy
was used to analyze the concentration of 7 in the MeOH
phase of the biphasic mixture. In the second and subsequent
cycles, the original MeOH phase was removed and 3 g of
fresh methanol was added to the PAO solvent containing the
polymer-supported dye to begin the next cycle. The process
was repeated until five cycles were complete. The results
presented in Figure 2 show that all of the PAOs can be re-
used. Dye leaching slightly decreased during these five cy-
cles. We believe this behavior is similar to leaching behavior
seen with catalysts where the first few cycles have more
leaching. We believe this occurs because the PIB-bound
species, here a PIB-bound dye, has some dispersity where the
lower molecular weight fraction has a small but measureably
greater leaching rate. No measureable volume decrease of
the PAO phase was seen through these five cycles – a result
that is consistent with the trace leaching of PAOs into the
polar phase. In similar experiments with heptane, the hep-
tane volume would decrease significantly through this same
number of cycles unless heptane-saturated MeOH was used
as the polar phase. Purification of PAO 2 and PAO 3 by ex-
traction with acetonitrile for 3 d in a liquid/liquid extraction
apparatus had little effect in these experiments.
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 1. Comparison of carboxylic-acid promoted isomeriza-
tion rates using different nonpolar phase soluble carboxylic
acids in either PAO 1.
results in Figure 1 showed a nonlinear increase in the ob-
served dye isomerization rate with the concentration of
the carboxylic acid. The acid-promoted dye isomerization
data and the thermal isomerization data show that these
simple reactions in PAO and heptane occur at similar
rates, further indicating that these hydrocarbon oligomers
can serve as a suitable solvent replacement for conven-
tional volatile hydrocarbons.
1.6
PAO 1
PAO 2
1.4
PAO 3
PAO 2 Purified
1.2
PAO 3 Purified
As noted above, PAOs are prepared from α-olefins using
acidic or transition metal catalysts. In the event some
catalyst residues from the PAO synthesis were present,
they, like the carboxylic acids, could promote the isomer-
ization rate of the basic dye 9. In the isomerization stud-
ies in Figure 1, we saw no evidence of this for studies of
thermal isomerization of 9 carried out in PAO 1. Howev-
er, thermal isomerizations in the ‘as received’ PAO 2 and
PAO 3 were faster than in heptane. When triethylamine
was added to these solutions, the higher isomerization
rate was no longer seen and the thermal isomerization of
dye 9 in the amine modified PAO 2 or 3 was the same as
in heptane or as in PAO 1. This suggested acidic impuri-
ties were present in PAOs 2 and 3. We thus examined
whether we could remove these impurities from PAOs 2
and 3 by continuous liquid/liquid extraction with acetoni-
trile. In the event, a 3 d liquid/liquid extraction appeared
to remove the presumed acid impurity and thermal isom-
erization rates in the purified PAO 2 and PAO 3 were the
same as in heptane or PAO 1. Since PAO 2 and PAO 3 are
less likely to be used as pure solvents for reactions be-
cause of their viscosity, we did not further examine these
two solvents in isomerization studies. We did however
examine how they behaved in recycling and in dye leach-
ing below.
1.0
0.8
0.6
0.4
0.2
0.0
1
2
3
4
5
Cycle
Figure 2. Recycling of PAO oligomer solvents in
PAO/methanol thermomorphic solvent system.
a
The changes in dye leaching using purified or ‘as received’
PAO 2 and 3 were either very small or were within exper-
imental error (Figure 2).
Conclusion
In summary, the work presented in this paper shows that
hydrocarbon oligomers can be used as alternatives for
heptane in thermomorphic solvent systems. Detailed
studies of one class of such solvents – PAOs – show that
PAO solvents behave like heptane in terms of their solu-
bility in other solvents and in terms of what they do or do
not dissolve. These studies also show that PAOs do not
significantly leach into polar phases. In addition, when
used with polymer-bound dyes, PAOs act as antileaching
agents reducing the amount of the polymer-bound dye
Finally, we examined recycling of these PAO solvents. The-
se recycling experiments included five cycles for each PAO.
Following the protocols used before, we used 3 g of MeOH as
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15. Howdle, S. M.; Pollak, S.; Birkin, N. A.; Warren, M. Carbon
that leaches into a polar phase. These recyclable oligo-
dioxide as a sustainable industrial solvent to replace organic
solvents. In Materials for a Sustainable Future; Letcher, T.
M.; Scott, J. L., Eds; RSC Publishing: Cambridge, UK, 2012;
pp 503-636.
meric hydrocarbon solvents were also compared to hep-
tane in studies of azo dye isomerization. The results show
that thermal isomerization or carboxylic acid promoted
isomerization of an azo dye occurs at the same rate in
heptane and a PAO. These results indicate that PAOs and
other polyolefin oligomers can be a more sustainable sol-
vent choice in comparison with heptane and that they can
serve even better than heptane for separation of soluble
polymer-bound catalysts in liquid/liquid separations.
16. Petigny, L.; Ozel, M. Z.; Perino, S.; Wajsman, J.; Chemat, F.
in Green Extraction of Natural Products: Theory and Prac-
tice; Chemat, F.; Strube, J., Eds.; Wiley-VCH, Weinheim,
Germany, 2015; Chapter 7.
17. Banerjee, S.; Sutanto, S.; Kleijn, J. M.; van Roosmalen, M. J.
E.; Witkamp, G.-J.; Stuart, M. A. C. Adv. Colloid Inter. Sci.
2012, 175, 11.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Associated Content
18. Alshamrani, A. K.; Vanderveen, J. R.; Jessop, P. G. Phys.
Chem. Chem. Phys. 2016, 18, 19276.
19. Kohlpainter, C. W.; Fischer, R. W.; Cornils, B. Appl. Catal.,
A. 2001, 221, 219.
20. Sugishi, T.; Matsugi, M.; Hamamoto, H.; Amii, H. RSC Adv.
2015, 5, 17269.
21. Bergbreiter, D. E. ACS Macro Lett. 2014, 3, 260.
22. Khamatnurova, T. V.; Zhang, D.; Suriboot, J.; Bazzi, H. S.;
Bergbreiter, D. E. Catal. Sci. Technol. 2015, 5, 2378.
23. Chao, C.-G.; Leibham, A. M.; Bergbreiter, D. E.; Org. Lett.,
2016, 57, 3272.
24. Bergbreiter, D. E.; Su, H.-L.; Koizumi, H.; Tian, J.-H. J. Or-
ganomet. Chem. 2011, 696, 1272.
25. Priyadarshani, N.; Liang, Y.; Suriboot, J. Bazzi, H. S.;
Bergbreiter, D. E. ACS Macro Lett. 2013, 2, 571.
Supporting Information
Experimental procedures for the synthesis of azo dyes and
functionalized polymer cosolvents, general procedures for
the setup of UV-Visible spectroscopy, and details of the 1H
NMR spectroscopic studies of leaching are provided.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Author Information
Corresponding Author
*bergbreiter@tamu.edu
Notes
26. Baker
Hughes
Inc.
Polywax.
http://assets.cmp.bh.mxmcloud.com/system/9a/bf54c6e6c
848125fdbdf1b41fdc8de/28729_polywax-sheet-1210.pdf (ac-
cessed October 16, 2016).
The authors declare no competing financial interest.
Acknowledgments
27. Suriboot, J.; Hobbs, C. E.; Yang, Y.-C.; Bergbreiter, D. E. J.
Polym. Sci., Part A: Polym. Chem. 2012, 50, 4840.
28. Sather, A. C.; Lee, H. G.; Colombe, J. R.; Zhang, A.; Buch-
wald, S. L. Nature 2015, 524, 208.
29. Priyadarshani, N.; Suriboot, J.; Bergbreiter, D. E. Green
Chem. 2013, 15, 1361.
30. Yang, Y.; Priyadarshani, N.; Khamatnurova, T.; Suriboot, J.;
Bergbreiter, D. E. J. Am. Chem. Soc. 2012, 134, 14714.
31. Suriboot, J.; Hobbs, C. E.; Guzman, W.; Bazzi, H. S.;
Bergbreiter, D. E. Macromolecules 2015, 48, 5511.
32. Hobbs, C.; Yang, Y.-C.; Ling, J.; Nicola, S.; Su, H.-L.; Bazzi,
H. S.; Bergbreiter, D. E. Org. Lett. 2011, 13, 3904.
33. Older, C. M.; Kristjansdottir, S.; Ritter, J. C.; Tam, W.;
Grady, M. C. Chem. Ind. 2009, 123, 319.
Support of CTL by the National Science Foundation (NSF
REU, CHE 1359175)), support of this research by the National
Science Foundation (CHE-1362735) and the Robert A. Welch
Foundation (Grant A-0639), and the donation of polyolefin
oligomers by Exxon (Dr. Wenning Han), Baker-Hughes (Dr.
Paul K. Hanna), and the TPC Group (Dr. Michael Nutt) are
gratefully acknowledged.
References
1. Jessop, P. G. Green Chem. 2011, 13, 1391.
2. Prat, D.; Wells, A.; Hayler, J.; Sneddon, H.; McElroy, C. R.;
Abou-Shehada, S.; Dunn, P. J. Green Chem. 2016, 18, 288.
3. Gu, Y.; Jerome, F. Chem. Soc. Rev. 2013, 42, 9550.
4. McLain, V. C. Int. J. Toxicology, 2008, 27, 83. McLain, V. C.
Int. J. Toxicology, 2007, 26, 115.
5. Carpenter, J. F. J. Synth. Lubr. 2006, 12, 13.
6. Bergbreiter, D. E.; Sung, S. D. Adv. Syn. Catal. 2006, 348,
1252.
34. Liang, Y.; Harrell, M. L.; Bergbreiter, D. E. Angew. Chem.,
Int. Ed. 2014, 53, 8084.
35. Yara-Varon, E.; Selka, A.; Fabiano-Tixier, A.-S.; Canela-
Garayoa, R.; Balcells, M.; Bily, A.; Touaibia, M.; Chemat, F.
Green Chem. 2016, DOI: 10.1039/C6GC02191C.
36. Rudnick, L. R. Chem. Ind. 2013, 135, 3.
37. Exxon Mobil, Synthetic Fluids and Lubricant Base Stocks.
http://www.exxonmobilchemical.com/Chem-
English/brands/spectrasyn-hi-vis-
pao.aspx?ln=productsservices
(accessed October 16, 2016).
38. Ineos, Durasyn Polyalphaolefins: Summary of Environmen-
7
Bergbreiter, D. E.; Liu, Y.-S.; Osburn, P. L. J. Am. Chem. Soc.
1998, 120, 4250.
8. Hayes, R.; Warr, G. G.; Atkin, R. Chem. Rev. 2015, 115, 6357.
9. Olmos, A.; Asensio, G.; Perez, P. J. ACS Catal. 2016, 6, 4265.
10. Lipshutz, B. H.; Ghorai, S. Green Chem. 2014, 16, 3660.
11. Alonso, D. A.; Baeza, A.; Chinchilla, R.; Guillena, G.; Pastor,
I. M.; Ramón, D. J. Eur. J. Org. Chem. 2016, 612.
12. Lo, A. S. W.; Horvath, I. T. Green Chem. 2015, 17, 4701.
13. Vafaeezadeh, M.; Hashemi, M. M. J. Mol. Liq. 2015, 207, 73.
14. Eshetu, G. G.; Armand, M.; Ohno, H.; Scrosati, B. Passerini,
S. Energy Environ. Sci. 2016, 9, 49.
tal
Data.
http://www.ineos.com/globalassets/ineos-
group/businesses/ineos-oligomers/she/durasyn-
environmental-summary-202009.pdf (accessed October 16,
2016).
39. U.S. Department of Health and Human Services, Toxologi-
cal
Profile
for
n-Hexane.
9
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 10 of 13
1
2
https://www.atsdr.cdc.gov/toxprofiles/tp113.pdf (accessed
October 16, 2016).
49. Shetty, M.; Kothapalli, V. A.; Hobbs, C. E. Polymer 2015, 80,
64.
3
4
5
6
7
8
9
40. Centers for Disease Control and Prevention, Heptane.
http://www.cdc.gov/niosh/pel88/142-82.html (accessed Oc-
tober 16, 2016).
41. Shueuermann, S. S.; Eibl, S.; Bartl, P. Lubrication Sci. 2011,
23, 221.
42. Obenauf, J.; Kretschmer, W. P.; Bauer, T.; Kempe, R. Eur. J.
Inorg. Chem. 2013, 537.
43. Keim, W. Angew. Chem., Int. Ed. 2013, 52, 12492.
44. Access Science from McGraw-Hill Education, Ethylene from
bioethanol.
https://www.accessscience.com/content/ethylene-from-
bioethanol/BR0120141 (accessed October 16, 2016).
45. Havelka, K. O.; Gerhardt, G. E. ACS Symp. Ser. 2015, 1192,
201
46. Wang, D.; Hakim, S. H.; Alonso, D. M.; Dumesic, J.A. Chem.
Commun. 2013, 49, 7040.
50. TPC
Group
Inc.,
Polyisobutylene.
http://www.tpcgrp.com/tpc-
group/products/polyisobutylene-150.html%E2%80%8B (ac-
cessed October 16, 2016).
51. Bergbreiter, D. E.; Priyadarshani, N. J. Polym. Sci., Part A:
Polym. Chem. 2011, 49, 1772.
52. Claridge, T. D. W.; Davies, S. G.; Polywka, M. E. C.; Roberts,
P. M.; Russell, A. J.; Savory, E. D.; Smith, A. D. Org. Lett.
2008, 10, 5433.
53. Bergbreiter, D. E.; Li, J. Chem. Commun. 2004, 42.
54. Bergbreiter, D. E.; Hein, M. D.; Huang, K. L. Macromole-
cules, 1989, 30, 177.
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Figure 1. Comparison of carboxylic-acid promoted isomeri-zation rates using different nonpolar phase
soluble carbox-ylic acids in either PAO 1.
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Figure 2. Recycling of PAO oligomer solvents in a PAO/methanol thermomorphic solvent system.
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